Biogeochemistry of some selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights into river water geochemistry, stable carbon isotopes and weathering material flows Biogeokemija izbranih slovenskih rek (Kamniška Bistrica, Idrijca in Sava v Sloveniji): vpogled v rečno vodno geokemijo, stabilne izotope ogljika in snovne tokove preperevanja Tjaša KANDUČ1, David KOCMAN1 & Timotej VERBOVŠEK2 1Jožef Stefan Institute, Department of Environmental Sciences, Jamova cesta 39, SI-1000 Ljubljana, Slovenia; e-mail: tjasa.kanduc@ijs.si 2Department of Geology, Faculty of Natural Sciences and Engineering, University of Ljubljana, Privoz 11, SI-1000 Ljubljana, Slovenia; Prejeto / Received 19. 10. 2016; Sprejeto / Accepted 23. 5. 2017; Objavljeno na spletu / Published online 9.6.2017 Dedicated to Professor Jože Pezdič on the occasion of his 70th birthday Key words: water geochemistry, biogeochemistry, carbon stable isotopes, weathering fluxes, rivers Ključne besede: vodna geokemija, biogeokemija, stabilni izotopi ogljika, snovni tokovi, reke Abstract Review of biogeochemical processes studied in three Slovenian rivers (River Kamniška Bistrica, River Sava in Slovenia and River Idrijca), which represent an ideal natural laboratory for studying biogeochemical processes and anthropogenic impacts in catchments with high weathering capacity is presented. The River Kamniška Bistrica, the River Sava in Slovenia and the River Idrijca water chemistry is dominated by HCO3 -, Ca2+ and Mg2+, and Ca2+/Mg2+ molar ratios indicate that calcite/dolomite weathering is the major source of ions to the river system. The Kamniška Bistrica River, the River Sava and River Idrijca and its tributaries are oversaturated with respect to calcite and dolomite. pCO2 concentrations were on average up to 25 times over atmospheric values for River Kamniška Bistrica, 20 times for River Sava and 13 times over atmospheric values for River Idrijca. δ13CDIC values ranged from -12.7 to -2.7 ‰ in River Kamniška Bistrica, from -12.7 to -6.3 ‰ in River Sava in Slovenia, from -10.8 to -6.6 ‰ in River Idrijca, respectively. In all investigated rivers we found out that carbonate dissolution is the most important biogeochemical process affecting carbon isotopes in the upstream portions of the catchment, while carbonate dissolution and organic matter degradation control carbon isotope signatures downstream, except for River Idrijca where both processes contribute equally from source to outflow to River Soča. Izvleček Predstavljen je pregled biogeokemisjkih procesov, ki smo jih preučevali v treh slovenskih rekah (Kamniška Bistrica, Sava v Sloveniji in Idrijci) in predstavljajo idealen naravni laboratorij za študij biogeokemisjkih procesov in antropogenih vplivov v porečjih z visoko intenzivnostjo preperevanja. Vodna geokemija Kamniške Bistrice, Save v Sloveniji in Idrijce je dominirana s HCO3 -, Ca2+ in Mg2+ ter Ca2+/Mg2+ molarnim razmerjem in kaže da je kalcitno/ dolomitno preperevanje glavni vir ionov v rečnem sistemu. Kamniška Bistrica, reka Sava v Sloveniji in Idrijca ter njeni pritoki so prenasičeni glede na kalcit in dolomit. Koncentracije pCO2 so v povprečju 25 krat nad atmosferskimi vrednostmi v Kamniški Bistrici, 20 krat nad atmosferskim v reki Savi v Sloveniji ter 13 krat v reki Idrijci. δ13CDIC vrednosti se v Kamniški Bistrici spreminjajo od -12,7 do -2,7 ‰, od -12,7 do -6,3 ‰ v reki Savi v Sloveniji in od 10,8 do -6,6 ‰ v reki Idrijci. V vseh raziskanih rekah je raztapljanje karbonatov najpomembnejši biogeokemijski proces, ki vpliva na izotopsko sestavo ogljika v zgornjem delu porečja, medtem ko raztapljanje karbonatov in razgradnja organske snovi kontrolirata izotopsko sestavo ogljika v spodnjem delu porečja, razen v reki Idrijci, kjer oba procesa vplivata enako od izvira do izliva v reko Sočo. GEOLOGIJA 60/1, 9-26, Ljubljana 2017 https://doi.org/10.5474/geologija.2017.001 © Author(s) 2017. CC Atribution 4.0 License 10 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK Introduction Systematic studies of river water geochem- istry provide important information on chemi- cal weathering of bedrock/soil and natural and anthropogenic processes that may control the dissolved chemical loads (schulte et al., 2011; GiBBs, 1972; reeDer et al., 1972; huh et al., 1998; néGrel & lachassaGne, 2000). Since carbonate weathering largely dominates the water chem- istry of river waters, characterization of rivers draining carbonate-dominated terrain is crucial to precisely identify the various contributions of the different sources of water solutes, and to estimate the weathering fluxes of the continen- tal crust and associated CO2 consumption (liu & zhao, 2000). Freshwaters cover small fraction of the Earth’s surface area, inland freshwater ecosystems (par- ticularly lakes, rivers and reservoirs) have rarely been considered as potentially important quan- titative components of the carbon cycle at either global or regional scales (cole et al., 2007). Riv- ers are the major pathways for the transport of carbon (C) from the continents top the oceans. Global river carbon fluxes are estimated to be 0.4 Pg C/year of organic C (evenly divided between particulate and dissolved phases) and 0.4 Pg C/ year for dissolved inorganic carbon (DIC). Bulk fluxes are small components of the global C cy- cle but are significant compared to net oceanic uptake of anthropogenic CO2 (sarMiento & sun- Dquist, 1992). Concentrations of DIC and its isotopic com- position of dissolved inorganic carbon (δ13CDIC) are governed by processes occurring in the riv- er system and vary seasonally. Changes of DIC concentrations result from carbon addition or removal from the DIC pool, while changes of its isotopic composition result from the fractiona- tion accompanying transformation of carbon or mixing of carbon from different sources (ateK- wana & KrishnaMurthy, 1998). The major sources of carbon to riverine DIC loads are dissolution of carbonate minerals, soil CO2 derived from root respiration and from microbial decomposition of organic matter and exchange with atmospheric CO2. The major processes removing riverine DIC are carbonate mineral precipitation, CO2 degas- sing, and aquatic photosynthesis (ateKwana & KrishnaMurthy, 1998). Rivers in Slovenia repre- sents an "ideal natural laboratory" for studying biogeochemical processes and tracing the river- ine carbon cycle as a result of its geologically het- erogeneous composition, relatively high specific discharge, and limited aquatic photosynthesis (GerM et al., 1999). The relative contributions of C3 and C4 veg- etation to an ecosystem can be reconstructed using the isotopic composition of particulate or- ganic carbon (POC, e.g. δ13CPOC), because of their different isotopic composition, which ranges from -32.0 to -20.0 ‰ for C3 plants and from -15.0 to -9.0 ‰ for C4 plants (Deines, 1980). Vegetation of the River Sava watershed in Slovenia is de- scribed in detail in Kanduč et al. (2007) and refer- ences therein. Detail evaluation of some selected sites of River Sava watershed was described with aquatic moss Fontinalis antipyretica (Mechora & Kanduč, 2016). Hydrogeochemical and isotopic characterization of River Pesnica, Slovenia was described in detail in Kanduč et al. (2016). Application of stable isotopes and biogeo- chemical processes in environmental studies is presented in Pezdič (1999). In this study we rep- resent summary (review) of biogeochemical re- search with application of stable isotope analysis of river systems; three rivers were subject of in- vestigation during years 2004–2011 in different time related to national research projects and program founding P1-0143 in Slovenia: River Kamniška Bistrica (Kanduč et al., 2013), River Sava in Slovenia (Kanduč et al., 2007) and River Idrijca (Kanduč et al., 2008) presented in the Fig- ures 1 and 2. Study area Catchment and hydrological characteristics of gravel bed rivers River Kamniška Bistrica is the left tributary of the River Sava, which is the largest river in Slo- venia (Figs. 1 and 2). Kamniška Bistrica emerges at the southern foothills of Kamnik-Savinja Alps at 630 m a.s.l. elevation. The river is 32.8 km long and drains an area of 380 km2, with an average discharge of 15.4 m3/s at its confluence with Riv- er Sava. The average discharge at the mouth of the River Kamniška Bistrica measured during this study was 0.7-12.1 m3/s. According to dis- charge regimes of all rivers and streams in Slove- nia, River Kamniška Bistrica has an alpine high mountain snow-rain regime (hrvatin, 1998). The maximum discharge occurs in autumn (Novem- ber) and spring (May) and minimum occurs in summer (August) and winter (February). Major 11Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... tributaries of the River Kamniška Bistrica are the Črna and Nevljica rivers on the left and Riv- er Pšata on the right. In the upper reaches, from the headwater spring to Stahovica (at the conflu- ence with River Črna), River Kamniška Bistri- ca changes over a short distance (6.8 km down- stream) from a clean alpine river to industrially and agriculturally affected river at the conflu- ence with the tributary River Črna, which carries sediments and waste waters from the abandoned Črna kaolin mine (raDinja et al., 1987). Discharge regimes of the River Sava are con- trolled by precipitation and the configuration of the landscape. In the upper part of the River Sava a snow-rain regime prevails and in the cen- tral and lower part a rain-snow regime (hrvatin, 1998). Annual discharge maxima are character- istic in spring and late summer, while discharge minima occur in the summer and winter months. The mean annual long term discharge (from the years 1960–1991) for the gauging stations increas- es from 17 m3/s of the upper section of the River Sava at Radovljica (location 35, Table 1, Fig. 1) to 182 m3/s of the central section at Hrastnik (loca- tion 60, Table 1, Fig. 1) and to 290 m3/s in the low- er section of the river at Čatež (location 68, Table 1, Fig. 1) (internet 2). Discharges are also con- trolled by hydropower outflows along the Sava River. The discharge conditions for the River Sava and its tributaries during the study ranged from 2 to 344 m3/s during spring 2004, from 1 to 144 m3/s during late summer 2004, and from 0.3 to 128 m3/s during winter, respectively. The River Idrijca joins the River Soča in the middle stretch at the village of Most na Soči. Both rivers have torrential characteristics. Detail description of the Idrijca catchment is described in Kanduč et al. (2008). High peaks and steep mountain slopes prevent air circulation in the valley and induce severe erosion. Characteristic long-term dis- charge data (from the years 1949 to 2015) accord- ing to the Slovenian Environment Agency for the gauging station on the Idrijca at Hotešk, which is located above the confluence with the River Soča, are as follows: low long-term discharge varies from 3.4 to 8.5 m3/s, mean long-term discharge varies from 14.3 to 39 m3/s, and high long-term discharge varies from 113 to 644 m3/s (inter- net 2). Fig. 1. General topographic map of the major river network in Slovenia, with a detailed location map of the numbered sampling sites for the rivers Kamniška Bistrica, Sava (Slovenian part) and Idrijca. Digital elevation model (DEM) was obtained from the Shuttle Radar Topography Mission (SRTM) dataset (internet 1). Numbers correspond to the sampling points IDs (see Tables 1 and 2). 12 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK General geological setting of selected river watersheds This chapter summarizes the general geolog- ical setting of the river watershed areas, as the geological composition of each river basin is very complex (Fig. 1). Therefore, the prevailing geo- logical units are described below. Detailed gen- eral description of geological setting of investi- gated Slovenian rivers is described in detail in Kanduč et al. (2007, 2008 and 2013). River Kamniška Bistrica. The upper part of the River Kamniška Bistrica is underlain by massive and stratified limestone and dolomite of middle and upper Triassic age (Fig. 2), and car- bonates generally prevail in the watershed. The middle part of the river is underlain by marlstone and limestone of Miocene age (Buser, 1987). The lower reaches of the River Kamniška Bistrica, along the right bank and before the confluence with the River Sava, is underlain by Pleistocene and Holocene age gravels, while the left bank is underlain by Permo-Carboniferous shales with a cover of Quaternary gravel. The River Kam- niška Bistrica is also one of the Slovenian wa- tersheds identified as having a high weathering capacity, due to the predominance of carbonate bedrock and high relief and precipitation (Kan- duč et al., 2013). River Sava in Slovenia. The valley of the Sava River extends in a NW-SE direction comprising almost half the surface area of Slovenia and has a very heterogeneous geological composition. Both branches of the Sava River (Sava Bohinjka and Sava Dolinka rivers) emerge in the Julian Alps, composed mostly of Triassic limestones and dolomites. Leaving the Alps approximately at the confluence of the Sava Bohinjka and Sava Dolinka rivers, river then flows on the Holocene and Pleistocene fluvioglacial sediments (terrac- es) (ŽlebniK, 1971). Eastwards from the city of Ljubljana, the watershed in Sava folds is mainly composed of Permo-Carbonian clastic sediments, which alternate with some Triassic carbonates, with Miocene sandstones, clays and gravels in some of the valleys. Leaving the Sava folds, the watershed in the Krško-Brežice area mainly con- sists of terraced Holocene and Pleistocene sedi- ments - sands and gravels. The catchments of the River Sava’s tributaries are composed of Trias- sic and Jurassic carbonates, Permo-Carbonian sandstones and siltstones, Oligocene clay and volcanic rocks, Miocene clastic rocks and Pleis- tocene sediments (Buser, 1987). River Idrijca. The beds in the upper part of the River Idrijca are composed of various sedimen- tary and volcanic rocks, predominantly massive and stratified Triassic limestones and dolomites. Along Idrijca, Middle Permian mica quartz sandstone and red sandstone with conglomerate are exposed as the oldest rocks. In the lower part of the flow, before the confluence with the River Soča, stratified and massive Upper Triassic dolo- mites and Cretaceous limestones with marls ap- pear (Buser, 1987). In general, the Idrija region has a very complex tectonic structure (MlaKar & čar 2009; čar, 2010) with several major faults dissecting the area and tectonic nappes overlying several units. Materials and methods Sampling and used methods Surface water sampling locations (Fig. 1, Ta- bles 1 and 2) were selected based on their rela- tionship to confluence of the major and minor streams, typically sampled before and after the confluence. Sampling of river water and tribu- taries was performed at different sampling sea- sons according to discharge regimes (hrvatin, 1998; Fratar, 2005). Temperature, conductivity, dissolved oxygen (DO), and pH measurements were performed in the field. The precision of dissolved oxygen saturation and conductiv- ity measurements was ±5 %. The field pH was determined on the NBS scale using two buffer calibrations with reproducibility of ±0.02 pH unit. Total alkalinity was measured within 24h of sample collection by Gran titration (GiesK- es, 1974) with a precision of ±1%. Carbonate rocks from hinterland of river watershed were ground to powder in an agate mortar and then approximately 2 mg of sample was first flushed with He and then transformed to CO2 by H3PO4 acid treatment. NBS 18 and NBS 19 were used as reference materials. The isotopic composi- tion of carbonate (δ13CCaCO3) was measured with a Europa Scientific 20-20 continuous flow IRMS ANCA-TG preparation module. All methods are described in detail in Kanduč et al. (2007, 2008 and 2013). All stable isotope results for carbon are ex- pressed in the conventional delta (δ) notation, defined as per mil (‰) deviation from the refer- ence standards VPDB. Precision was ±0.2 ‰ for δ13CDIC, δ 13CPOC and δ 13CCaCO3. 13Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... Major and minor cation chemistry was meas- ured by inductively coupled plasma optical emission spectroscopy (ICP-OES) technique. The precision of the method was ±2% for ma- jor (Ca2+, Mg2+, Na+ and K+) and ±5% for minor elements (Sr and Si). The stable isotope com- position of dissolved inorganic carbon (δ13CDIC) was determined with a Europa Scientific 20- 20 continuous flow IRMS ANCA-TG prepara- tion module. Phosphoric acid (H3PO4, 100 %) was added (100-200 ml) to a septum-sealed vial which was then purged with pure He. The water sample (6 mL) was injected into a septum tube and headspace CO2 was measured (modified af- ter MiyajiMa et al., 1995; sPötl, 2005). In order to determine the optimal extraction procedure for surface water samples, a standard solution of Na2CO3 (Carlo Erba) with a known δ 13CDIC of -10.8 ‰ ± 0.2 ‰ was prepared with a concen- tration of either 4.8 mol/L (for samples with al- kalinity above 2 mmol/L) or of 2.4 mmol/L (for samples with alkalinity below 2 mmol/L). The carbon stable isotope composition of particulate organic carbon (δ13CPOC) was determined with a Fig. 2. General geological map of Slovenia with selected three rivers: Kamniška Bistrica, Sava in Slovenia and Idrijca. Geological data were obtained from the 1: 5 Million International Geological Map of Europe and Adjacent Areas (IGME 5000) dataset (internet 3). 14 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK T ab le 1 . S a m p li n g lo ca ti on s a n d g eo ch em ic a l d at a fo r sp ri n g sa m p li n g se a so n ( sa m p li n g ye a rs : Id ri jc a: 2 00 6 -2 00 7, K a m n iš k a B is tr ic a: 2 01 0 -2 01 1, S av a: 2 00 4 -2 00 5) . ID n u m b er s co rr e- sp on d t o th e lo ca ti on s in F ig u re 1 . ID N am e Ri ve r Ty pe LA T (° ) LO N (° ) Z (m ) T (° C) pH (-) Al ka l. m m ol /L EC (µ S/ cm ) Ca 2+ m m ol /L M g2 + m m ol /L N a+ m m ol /L K+ m m ol /L Si m m ol /L SO 42 - m m ol /L Cl - m m ol /L N O 3- m m ol /L pC O 2 (b ar ) SI ca lc ite (-) SI do lo m ite (-) δ1 3 C DI C (‰ ) 0 Id rij ca Co nfl ue nc e Id rij ca /B el ca Ri ve r 45 .9 63 39 6 13 .9 81 28 1 38 9 9. 00 8. 43 4. 12 33 3. 0 0. 82 0. 74 0. 05 0. 00 0. 00 0. 04 0. 03 0. 06 -3 .1 4 0. 66 1. 17 -9 .4 1 Id rij ca Po dr ot ej a Ri ve r 45 .9 90 65 2 14 .0 35 86 4 32 5 7. 30 7. 92 4. 20 35 3. 0 0. 93 0. 75 0. 07 0. 00 0. 00 0. 05 0. 07 0. 09 -2 .6 2 0. 20 0. 16 -1 0. 6 2 Id rij ca Ko le kt or Ri ve r 46 .0 09 51 9 14 .0 28 85 8 31 6 10 .8 8. 43 4. 33 36 7. 0 1. 15 0. 87 0. 11 0. 05 0. 02 0. 11 0. 10 0. 05 -3 .1 2 0. 84 1. 48 -1 0. 1 3 Id rij ca Tr av ni k Ri ve r 46 .0 68 86 9 13 .9 93 71 6 26 7 11 .4 8. 44 4. 43 48 5. 0 1. 00 1. 22 0. 10 0. 02 0. 02 0. 72 0. 10 0. 05 -3 .1 2 0. 80 1. 62 -9 .2 4 Id rij ca Ko za rs ka g ra pa Ri ve r 46 .1 17 87 7 13 .9 21 68 2 22 7 11 .7 8. 29 4. 26 41 6. 0 1. 01 0. 89 0. 11 0. 02 0. 03 0. 36 0. 11 0. 04 -2 .9 7 0. 66 1. 21 -9 .3 5 Id rij ca Be fo re B ač a Ri ve r 46 .1 43 31 2 13 .7 67 60 4 15 3 13 .0 8. 82 4. 27 38 3. 0 1. 16 0. 85 0. 10 0. 05 0. 00 0. 00 0. 00 0. 47 -3 .5 3 1. 22 2. 27 -8 .4 6 Id rij ca Aft er B ač a Ri ve r 46 .1 44 95 4 13 .7 65 60 8 15 2 12 .7 8. 77 4. 20 35 6. 0 1. 15 0. 84 0. 11 0. 05 0. 02 0. 00 0. 00 0. 05 -3 .4 8 1. 16 2. 15 -8 .3 7 Id rij ca Za la Tr ib ut ar y 45 .9 86 56 1 14 .0 31 76 8 32 8 10 .6 8. 09 4. 87 42 0. 0 1. 27 0. 98 0. 17 0. 04 0. 03 0. 07 0. 15 0. 06 -2 .7 2 0. 60 1. 00 -9 .7 8 Id rij ca Lj ub ev šč a Tr ib ut ar y 45 .9 95 14 2 14 .0 34 41 1 32 5 10 .2 8. 54 5. 04 44 4. 0 1. 32 1. 05 0. 30 0. 05 0. 07 0. 10 0. 29 0. 05 -3 .1 7 1. 04 1. 90 -9 .6 9 Id rij ca N ik ov a Tr ib ut ar y 46 .0 01 97 14 .0 26 07 8 32 5 10 .1 8. 67 4. 81 41 8. 0 1. 31 0. 91 0. 20 0. 06 0. 04 0. 10 0. 13 0. 04 -3 .3 3 1. 14 2. 03 -9 .4 10 Id rij ca Ka no m lji ca Tr ib ut ar y 46 .0 33 90 2 14 .0 15 13 9 30 2 10 .8 8. 29 4. 33 36 8. 0 1. 23 0. 87 0. 08 0. 05 0. 04 0. 15 0. 00 0. 04 -2 .9 3 0. 78 1. 32 -9 .4 11 Id rij ca Ce rk ni ca Tr ib ut ar y 46 .1 03 91 6 13 .9 48 57 6 24 5 11 .8 8. 35 3. 52 34 9. 0 1. 25 0. 47 0. 19 0. 06 0. 10 0. 19 0. 12 0. 02 -3 .1 2 0. 75 1. 00 -7 .6 12 Id rij ca Tr eb uš či ca Tr ib ut ar y 46 .0 94 54 9 13 .8 32 34 4 18 8 11 .6 8. 37 4. 01 18 1. 0 1. 00 0. 85 0. 06 0. 04 0. 02 0. 05 0. 03 0. 05 -3 .0 8 0. 71 1. 29 -8 .0 13 Id rij ca Ba ča Tr ib ut ar y 46 .1 44 88 8 13 .7 67 26 3 15 4 12 .2 8. 37 3. 15 28 2. 0 1. 18 0. 32 0. 08 0. 05 0. 07 0. 08 0. 00 0. 05 -3 .2 1 0. 74 0. 86 -6 .9 14 Ka m ni šk a Bi st ric a Sp rin g Ri ve r 46 .3 25 73 44 14 .5 88 46 44 6 62 3 5. 70 8. 29 1. 55 18 8. 5 0. 70 0. 18 0. 04 0. 00 0. 00 0. 01 0. 00 0. 03 -3 .4 2 0. 04 -0 .6 8 -2 .7 15 Ka m ni šk a Bi st ric a be fo re S ta ho vi ca Ri ve r 46 .2 85 67 75 3 14 .6 16 92 48 2 53 0 7. 10 8. 40 2. 33 19 4. 0 0. 80 0. 24 0. 03 0. 00 0. 01 0. 02 0. 01 0. 04 -3 .3 6 0. 39 0. 10 -5 .0 16 Ka m ni šk a Bi st ric a aft er S ta ho vi ca Ri ve r 46 .2 58 67 67 5 14 .6 03 64 76 9 45 0 7. 70 8. 63 2. 38 19 8. 6 0. 90 0. 27 0. 05 0. 00 0. 01 0. 03 0. 03 0. 04 -3 .6 0 0. 64 0. 62 -5 .6 17 Ka m ni šk a Bi st ric a Ka m ni k Ri ve r 46 .2 21 51 34 14 .6 10 34 33 8 37 8 10 .6 8. 61 2. 86 23 8. 4 1. 04 0. 33 0. 11 0. 01 0. 02 0. 03 0. 06 0. 04 -3 .5 4 0. 80 0. 97 -7 .4 18 Ka m ni šk a Bi st ric a Vi r Ri ve r 46 .1 47 10 26 9 14 .6 04 53 60 3 31 0 14 .6 8. 73 2. 82 23 9. 3 1. 04 0. 32 0. 09 0. 01 0. 02 0. 01 0. 03 0. 02 -3 .5 9 0. 98 1. 45 -6 .9 19 Ka m ni šk a Bi st ric a Do m ža le Ri ve r 46 .1 35 84 97 4 14 .6 02 77 83 7 30 0 9. 50 8. 54 3. 35 28 2. 7 1. 20 0. 42 0. 21 0. 02 0. 03 0. 06 0. 16 0. 04 -3 .3 4 0. 85 1. 15 -7 .3 20 Ka m ni šk a Bi st ric a Vi de m Ri ve r 46 .0 88 35 69 6 14 .6 25 94 16 8 26 0 12 .5 8. 34 4. 39 36 8. 3 1. 50 0. 50 0. 38 0. 05 0. 05 0. 04 0. 16 0. 11 -3 .0 1 0. 91 1. 36 -9 .6 21 Ka m ni šk a Bi st ric a Do lsk i G ra be n Tr ib ut ar y 46 .3 08 51 52 3 14 .6 06 99 00 3 57 0 7. 80 8. 15 2. 92 23 9. 7 1. 21 0. 18 0. 05 0. 00 0. 35 0. 03 0. 02 0. 05 -3 .0 0 0. 41 -0 .1 3 -9 .8 22 Ka m ni šk a Bi st ric a Bi st rič ic a Tr ib ut ar y 46 .2 86 06 50 1 14 .6 17 10 38 3 47 0 9. 90 8. 49 3. 79 31 7. 1 1. 17 0. 66 0. 13 0. 02 0. 06 0. 08 0. 06 0. 05 -3 .2 5 0. 85 1. 36 -8 .7 23 Ka m ni šk a Bi st ric a Čr na Tr ib ut ar y 46 .2 68 02 86 9 14 .6 17 10 38 3 47 0 8. 70 8. 47 2. 72 29 1. 0 1. 12 0. 50 0. 24 0. 02 0. 06 0. 08 0. 22 0. 05 -3 .3 6 0. 66 0. 86 -8 .7 24 Ka m ni šk a Bi st ric a N ev lji ca Tr ib ut ar y 46 .2 30 68 02 4 14 .6 37 50 48 3 46 0 10 .4 8. 42 4. 53 35 8. 4 1. 72 0. 43 0. 18 0. 02 0. 07 0. 11 0. 11 0. 05 -3 .0 7 0. 99 1. 28 -1 1. 0 25 Ka m ni šk a Bi st ric a Ra do m el jsk a M lin šč ic a Tr ib ut ar y 46 .1 72 51 45 5 14 .6 08 03 29 1 34 0 8. 90 8. 54 2. 91 23 4. 0 1. 05 0. 32 0. 11 0. 01 0. 02 0. 04 0. 07 0. 04 -3 .4 0 0. 74 0. 85 -7 .1 0 26 Ka m ni šk a Bi st ric a Pš at a Tr ib ut ar y 46 .1 60 32 59 9 14 .5 93 30 62 7 33 8 16 .1 8. 34 4. 25 40 9. 4 1. 20 0. 35 0. 24 0. 04 0. 04 0. 09 0. 23 0. 22 -2 .9 6 0. 82 1. 11 -1 0. 5 27 Ka m ni šk a Bi st ric a Ra ča Tr ib ut ar y 46 .1 44 01 04 7 14 .6 16 06 56 4 31 0 13 .5 8. 38 4. 33 39 0. 3 0. 60 0. 38 0. 21 0. 02 0. 03 0. 09 0. 41 0. 05 -3 .0 4 0. 59 0. 96 -1 0. 7 28 Ka m ni šk a Bi st ric a Ho m šk a M lin šč ic a Tr ib ut ar y 46 .0 95 43 70 8 14 .6 25 63 53 9 29 0 10 .5 8. 61 3. 09 24 3. 9 1. 05 0. 33 0. 19 0. 01 0. 02 0. 05 0. 17 0. 05 -3 .4 3 0. 85 1. 12 -6 .9 29 Ka m ni šk a Bi st ric a Pš at a ch an ne l Tr ib ut ar y 46 .0 88 35 69 6 14 .6 25 94 16 8 28 0 9. 80 8. 38 3. 58 32 7. 1 1. 40 0. 41 0. 22 0. 04 0. 08 0. 08 0. 16 0. 09 -3 .1 5 0. 80 0. 96 -1 0. 9 30 Sa va Sa va D ol in ka , s pr in g Ri ve r 46 .4 92 38 10 8 13 .7 37 38 95 8 83 0 8. 60 7. 83 2. 98 27 6. 0 1. 02 0. 52 0. 05 0. 00 0. 03 0. 06 0. 00 0. 03 -2 .6 7 0. 04 -0 .3 4 -1 0. 7 31 Sa va Sa va D ol in ka , P od ko re n Ri ve r 46 .4 91 08 96 13 .7 62 49 57 2 82 9 8. 90 8. 14 2. 62 24 4. 0 0. 00 0. 00 0. 10 0. 15 0. 02 -3 .8 0 -1 0. 3 32 Sa va Pi šn ic a at K ra nj sk a go ra Tr ib ut ar y 46 .4 74 64 47 9 13 .7 81 97 23 4 81 9 7. 60 8. 36 2. 37 21 6. 0 0. 82 0. 44 0. 07 0. 00 0. 01 0. 07 0. 00 0. 04 -3 .3 1 0. 36 0. 31 -7 .9 33 Sa va Sa va D ol in ka , D ov je Ri ve r 46 .4 62 65 05 9 13 .9 53 93 19 6 70 4 9. 70 8. 28 2. 81 25 1. 0 1. 00 0. 53 0. 07 0. 00 0. 03 0. 13 0. 00 0. 03 -3 .1 5 0. 45 0. 54 -8 .6 34 Sa va Sa va D ol in ka , Š ob ec Ri ve r 46 .3 67 97 84 9 14 .1 34 64 50 5 45 9 9. 70 8. 48 3. 19 28 3. 0 1. 12 0. 43 0. 09 0. 00 0. 02 0. 15 0. 00 0. 04 -3 .3 0 0. 75 0. 98 -9 .6 15Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... ID N am e Ri ve r Ty pe LA T (° ) LO N (° ) Z (m ) T (° C) pH (-) Al ka l. m m ol /L EC (µ S/ cm ) Ca 2+ m m ol /L M g2 + m m ol /L N a+ m m ol /L K+ m m ol /L Si m m ol /L SO 42 - m m ol /L Cl - m m ol /L N O 3- m m ol /L pC O 2 (b ar ) SI ca lc ite (-) SI do lo m ite (-) δ1 3 C DI C (‰ ) 35 Sa va Ri ve r S av ic a Tr ib ut ar y 46 .2 90 39 11 7 13 .8 02 50 16 7 70 0 6. 20 8. 32 2. 00 17 2. 3 0. 76 0. 18 0. 01 0. 00 0. 01 0. 03 0. 00 0. 04 -3 .3 4 0. 21 -0 .3 7 -5 .8 36 Sa va La ke B oh in j, ou tle t Tr ib ut ar y 46 .2 78 39 8 13 .8 86 34 17 55 7 12 .3 8. 26 2. 35 20 1. 0 0. 90 0. 20 0. 05 0. 00 0. 01 0. 04 0. 00 0. 04 -3 .1 9 0. 38 0. 06 -8 .3 37 Sa va Sa va B oh in jk a, N om en j Tr ib ut ar y 46 .2 98 01 52 6 14 .0 37 57 24 9 50 9 9. 50 8. 43 2. 30 20 3. 0 1. 01 0. 19 0. 03 0. 00 0. 01 0. 04 0. 03 0. 04 -3 .3 9 0. 54 0. 26 -9 .1 38 Sa va Sa va O to če c Ri ve r 46 .3 12 16 99 7 14 .2 37 44 78 4 41 5 10 .3 8. 57 2. 91 25 4. 0 1. 10 0. 33 0. 07 0. 00 0. 02 0. 09 0. 00 0. 04 -3 .4 3 0. 80 0. 99 -9 .0 39 Sa va Tr žiš ka B ist ric a, B ist ric a Tr ib ut ar y 46 .2 90 11 45 8 14 .2 84 42 50 3 42 2 11 .0 8. 95 2. 60 27 7. 0 1. 22 0. 44 0. 09 0. 00 0. 03 0. 36 0. 00 0. 04 -3 .8 9 1. 12 1. 73 -6 .8 40 Sa va Ko kr a, K ra nj Tr ib ut ar y 46 .2 52 04 69 9 14 .3 68 69 10 4 40 7 12 .1 8. 10 2. 64 26 4. 0 1. 08 0. 43 0. 07 0. 00 0. 02 0. 19 0. 00 0. 04 -2 .9 8 0. 33 0. 20 -7 .0 41 Sa va Sa va , K ra nj Ri ve r 46 .2 37 82 81 3 14 .3 52 02 31 8 35 0 10 .5 8. 59 2. 89 24 6. 0 1. 15 0. 35 0. 08 0. 01 0. 02 0. 12 0. 08 0. 05 -3 .4 5 0. 83 1. 07 -9 .5 42 Sa va Sa va , S m le dn ik Ri ve r 46 .1 64 19 81 6 14 .4 25 55 63 3 33 6 10 .6 8. 42 2. 79 30 5. 0 1. 18 0. 38 0. 13 0. 03 0. 02 0. 14 0. 00 0. 06 -3 .2 9 0. 67 0. 76 -1 0. 2 43 Sa va So ra , L ad ja Tr ib ut ar y 46 .1 43 58 73 2 14 .3 92 85 26 6 31 3 10 .2 8. 37 2. 48 26 0. 0 0. 93 0. 43 0. 12 0. 01 0. 05 0. 12 0. 00 0. 09 -3 .2 9 0. 48 0. 52 -1 1. 2 44 Sa va Sa va , T ac en Ri ve r 46 .1 17 22 40 1 14 .4 61 18 30 4 28 0 10 .4 8. 43 3. 16 30 2. 0 1. 15 0. 39 0. 10 0. 00 0. 03 0. 14 0. 00 0. 07 -3 .2 5 0. 72 0. 88 -1 0. 7 45 Sa va Ka m ni šk a Bi st ric a, Be rič ev o Tr ib ut ar y 46 .0 88 42 29 1 14 .6 26 48 00 2 26 0 11 .2 8. 17 3. 90 38 1. 0 1. 42 0. 46 0. 35 0. 03 0. 04 0. 17 0. 00 0. 21 -2 .8 9 0. 64 0. 72 -1 2. 4 46 Sa va Lj ub lja ni ca , Z al og Tr ib ut ar y 46 .0 62 20 61 7 14 .6 21 69 26 8 26 7 10 .9 8. 10 4. 01 39 1. 0 1. 47 0. 50 0. 17 0. 00 0. 03 -2 .8 1 0. 60 0. 67 -1 3. 5 47 Sa va Sa va , D ol sk o Ri ve r 46 .0 87 99 49 6 14 .6 78 35 02 7 26 5 10 .9 8. 23 3. 27 33 8. 0 1. 36 0. 45 0. 17 0. 00 0. 03 0. 15 0. 00 0. 10 -3 .0 3 0. 61 0. 66 -1 2. 7 48 Sa va Je vn ic a, Je vn ic a Tr ib ut ar y 46 .0 83 60 96 5 14 .7 37 19 53 3 24 0 13 .0 7. 79 0. 39 62 .3 0. 15 0. 08 0. 13 0. 03 0. 16 0. 07 0. 07 0. 03 -3 .4 7 -1 .5 6 -3 .4 6 -8 .1 49 Sa va Sa va , K re sn ic e Ri ve r 46 .0 96 32 92 9 14 .7 73 95 62 3 23 5 11 .1 8. 20 3. 60 32 4. 0 1. 33 0. 45 0. 17 0. 01 0. 03 0. 14 0. 00 0. 09 -2 .5 6 0. 61 0. 68 -1 2. 5 50 Sa va Sa va , L iti ja Ri ve r 46 .0 56 46 17 1 14 .8 20 51 44 7 23 0 12 .1 8. 27 3. 28 32 3. 0 1. 34 0. 45 0. 16 0. 00 0. 03 0. 15 0. 00 0. 12 -3 .0 6 0. 66 0. 79 -1 2. 3 51 Sa va Re ka p ri Br eg u, L iti ja Tr ib ut ar y 46 .0 59 62 08 6 14 .8 46 14 68 4 24 5 13 .4 8. 18 2. 59 27 2. 0 0. 80 0. 62 0. 17 0. 03 0. 11 0. 14 0. 00 0. 08 -3 .0 5 0. 29 0. 43 -1 3. 2 52 Sa va Sa va , L og Ri ve r 46 .0 85 63 08 3 14 .8 92 06 99 9 23 0 11 .2 8. 18 3. 00 34 4. 0 1. 26 0. 45 0. 15 0. 01 0. 03 0. 14 0. 16 0. 09 -3 .0 1 0. 50 0. 98 -1 2. 0 53 Sa va Po lšn ik , S av a Tr ib ut ar y 46 .0 83 37 90 1 14 .9 23 08 09 1 26 0 8. 40 8. 17 1. 87 20 8. 0 0. 57 0. 45 0. 15 0. 03 0. 14 0. 15 0. 09 0. 03 -3 .2 1 -0 .0 6 -0 .3 6 -1 1. 6 54 Sa va M ed ija , Z ag or je Tr ib ut ar y 46 .1 21 25 63 8 14 .9 94 34 95 3 24 0 8. 70 8. 16 4. 15 49 1. 0 1. 64 0. 76 0. 29 0. 05 0. 10 0. 38 0. 00 0. 12 -2 .8 7 0. 66 0. 87 -1 3. 0 55 Sa va Sa va , Z ag or je Ri ve r 46 .1 18 89 00 3 14 .9 94 55 67 1 22 5 10 .4 8. 10 3. 32 38 0. 0 1. 34 0. 48 0. 17 0. 00 0. 03 0. 16 0. 17 0. 10 -2 .8 9 0. 48 0. 41 -1 1. 0 56 Sa va Šk le nd ro ve c, Z ag or je Tr ib ut ar y 46 .1 03 01 83 3 15 .0 02 15 04 6 35 0 8. 70 8. 34 4. 26 42 4. 0 1. 48 0. 91 0. 15 0. 01 0. 05 0. 25 0. 16 0. 05 -3 .0 4 0. 80 1. 28 -1 2. 4 57 Sa va M ito vš ic a, T rb ov lje Tr ib ut ar y 46 .1 19 71 80 6 15 .0 42 99 91 1 35 0 8. 40 8. 19 3. 34 31 8. 0 1. 57 0. 34 0. 03 0. 00 0. 03 0. 17 0. 05 0. 08 -2 .9 9 0. 60 0. 41 -1 2. 6 58 Sa va Tr bo ve ljš či ca , T rb ov lje Tr ib ut ar y 46 .1 61 92 11 7 15 .0 52 68 00 8 23 0 10 .1 8. 31 3. 56 38 9. 0 0. 91 0. 76 0. 39 0. 04 0. 12 0. 28 0. 01 0. 11 -3 .0 8 0. 53 0. 89 -1 0. 5 59 Sa va Sa va , T rb ov lje Ri ve r 46 .1 26 21 67 1 15 .0 36 32 72 3 22 0 10 .7 8. 08 3. 57 39 5. 0 1. 37 0. 49 0. 20 0. 01 0. 03 0. 21 0. 18 0. 10 -2 .8 4 0. 50 0. 46 -1 1. 5 60 Sa va Sa va , H ra st ni k Ri ve r 46 .1 21 55 11 3 15 .0 91 62 58 21 0 10 .8 8. 08 3. 38 34 9. 0 1. 32 0. 47 0. 18 0. 01 0. 02 0. 16 0. 17 0. 10 -2 .8 6 0. 46 0. 39 -1 1. 5 61 Sa va Bo be n, H ra st ni k Tr ib ut ar y 46 .1 50 57 26 4 15 .0 85 92 69 4 22 0 11 .0 8. 10 4. 48 57 3. 0 1. 13 0. 21 0. 15 -2 .7 4 -9 .5 62 Sa va Sa vi nj a, R im sk e To pl ic e Tr ib ut ar y 46 .1 22 62 89 5 15 .2 03 28 14 7 20 0 14 .4 8. 98 3. 04 37 5. 0 1. 30 0. 43 0. 32 0. 03 0. 03 0. 30 0. 00 0. 12 -3 .8 5 1. 27 2. 06 -8 .5 63 Sa va Sa va , R ad eč e Ri ve r 46 .0 65 52 03 9 15 .1 88 17 90 6 19 3 11 .6 8. 10 3. 66 37 5. 0 1. 34 0. 47 0. 20 0. 02 0. 03 0. 19 0. 00 0. 10 -2 .8 4 0. 53 0. 54 -1 1. 1 64 Sa va M irn a, D ol B os ta nj Tr ib ut ar y 46 .0 04 25 24 15 .2 88 07 39 6 19 1 12 .9 8. 48 4. 57 44 3. 0 1. 66 0. 82 0. 11 0. 00 0. 07 0. 19 0. 00 0. 05 -3 .1 4 1. 07 1. 80 -1 1. 5 65 Sa va Sa va , B re st an ic a Ri ve r 45 .9 87 08 88 2 15 .4 65 96 94 7 15 0 13 .4 8. 42 3. 17 38 3. 0 1. 38 0. 48 0. 19 0. 01 0. 03 0. 18 0. 16 0. 10 -3 .2 3 0. 82 1. 14 -1 0. 0 66 Sa va Sa va , B re žic e Ri ve r 45 .8 97 94 94 5 15 .5 91 47 52 5 14 5 14 .2 8. 04 3. 39 39 6. 0 1. 42 0. 52 0. 21 0. 02 0. 03 0. 22 0. 00 0. 10 -2 .5 3 0. 50 0. 54 -1 1. 9 67 Sa va Kr ka , Č at ež Tr ib ut ar y 45 .8 94 36 14 2 15 .5 91 06 33 4 14 0 13 .5 8. 32 4. 33 42 3. 0 1. 67 0. 50 0. 11 0. 00 0. 04 0. 10 0. 00 0. 09 -2 .9 9 0. 92 1. 30 -1 2. 9 68 Sa va Sa va , M os te c Ri ve r 45 .8 95 65 40 1 15 .6 26 99 19 7 14 0 13 .4 8. 28 3. 52 41 2. 0 1. 52 0. 50 0. 16 0. 00 0. 03 0. 16 0. 16 0. 10 -3 .0 4 0. 76 1. 02 -1 1. 1 69 Sa va So tla , R ak ov ec Tr ib ut ar y 45 .9 20 58 24 4 15 .7 04 79 52 1 14 0 14 .0 8. 15 5. 22 57 0. 0 2. 33 0. 68 0. 37 0. 05 0. 09 0. 41 0. 29 0. 11 -2 .7 4 0. 95 1. 35 -1 1. 8 70 Sa va Sa va , B re ga na Ri ve r 45 .8 61 10 49 3 15 .6 91 78 09 1 13 5 13 .8 8. 23 3. 75 39 8. 0 1. 48 0. 50 0. 17 0. 01 0. 03 0. 19 0. 00 0. 09 -2 .9 6 0. 74 0. 98 -1 1. 1 16 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK T ab le 2 . S a m p li n g lo ca ti on s a n d g eo ch em ic a l d at a fo r au tu m n s a m p li n g se a so n ( sa m p li n g ye a rs : Id ri jc a: 2 00 6 -2 00 7, K a m n iš k a B is tr ic a: 2 01 0 -2 01 1, S av a: 2 00 4 -2 00 5) . ID n u m b er s co rr e- sp on d t o th e lo ca ti on s in F ig u re 1 . G IS _ ID N am e Ri ve r Ty pe LA T (° ) LO N (° ) Z (m ) T (° C) pH Al ka l. m m ol /L EC µS /c m Ca 2+ m m ol /L M g2 + m m ol /L N a+ m m ol /L K+ m m ol /L Si m m ol /L SO 42 - m m ol /L Cl - m m ol /L N O 3- m m ol /L pC O 2 ba r SI ca l SI do l δ1 3 C DI C (‰ ) 0 Id rij ca Co nfl ue nc e Id rij ca /B el ca Ri ve r 45 .9 63 39 6 13 .9 81 28 1 38 9 8. 8 8. 17 4. 35 33 8. 0 1. 05 0. 76 0. 06 0. 02 0. 03 0. 07 0. 04 -2 .7 7 0. 61 0. 96 -1 0. 1 1 Id rij ca Po dr ot ej a Ri ve r 45 .9 90 65 2 14 .0 35 86 4 32 5 8. 0 7. 96 3. 88 32 7. 0 1. 23 0. 68 0. 06 0. 01 0. 02 0. 06 0. 07 -2 .6 1 0. 42 0. 44 -9 .3 2 Id rij ca Ko le kt or Ri ve r 46 .0 09 51 9 14 .0 28 85 8 31 6 6. 5 7. 73 3. 93 36 4. 0 1. 16 0. 78 0. 07 0. 01 0. 02 0. 08 0. 07 -2 .3 8 0. 14 -0 .0 5 -1 0. 8 3 Id rij ca Tr av ni k Ri ve r 46 .0 68 86 9 13 .9 93 71 6 26 7 8. 5 8. 34 4. 01 37 5. 0 1. 18 0. 94 0. 08 0. 02 0. 02 0. 14 0. 08 -2 .9 8 0. 78 1. 33 -1 0. 1 4 Id rij ca Ko za rs ka g ra pa Ri ve r 46 .1 17 87 7 13 .9 21 68 2 22 7 9. 0 8. 06 3. 99 40 9. 0 1. 26 0. 97 0. 12 0. 06 0. 02 0. 35 0. 11 -2 .7 0 0. 54 0. 86 -9 .4 5 Id rij ca Be fo re B ač a Ri ve r 46 .1 43 31 2 13 .7 67 60 4 15 3 9. 5 8. 82 4. 21 41 0. 0 1. 26 1. 03 0. 09 0. 01 0. 02 0. 37 0. 08 -2 .9 2 0. 80 1. 41 -9 .2 6 Id rij ca Aft er B ač a Ri ve r 46 .1 44 95 4 13 .7 65 60 8 15 2 9. 6 8. 26 4. 66 41 2. 0 1. 26 1. 00 0. 11 0. 03 0. 02 0. 38 0. 10 -2 .8 3 0. 80 1. 40 -9 .0 7 Id rij ca Za la Tr ib ut ar y 45 .9 86 56 1 14 .0 31 76 8 32 8 8 Id rij ca Lj ub ev šč a Tr ib ut ar y 45 .9 95 14 2 14 .0 34 41 1 32 5 8. 3 8. 29 5. 10 46 5. 0 1. 37 1. 09 0. 33 0. 04 0. 05 0. 17 0. 31 -2 .8 3 0. 87 1. 53 -1 0. 4 9 Id rij ca N ik ov a Tr ib ut ar y 46 .0 01 97 14 .0 26 07 8 32 5 8. 4 8. 23 4. 70 43 4. 0 1. 38 0. 89 0. 23 0. 04 0. 04 0. 14 0. 19 -2 .8 0 0. 80 1. 28 -9 .9 10 Id rij ca Ka no m lji ca Tr ib ut ar y 46 .0 33 90 2 14 .0 15 13 9 30 2 8. 2 8. 34 4. 08 37 8. 0 1. 26 0. 90 0. 07 0. 02 0. 03 0. 21 0. 06 -2 .9 8 0. 81 1. 34 -8 .7 11 Id rij ca Ce rk ni ca Tr ib ut ar y 46 .1 03 91 6 13 .9 48 57 6 24 5 9. 5 8. 19 3. 63 37 8. 0 1. 35 0. 51 0. 37 0. 05 0. 09 0. 09 0. 78 -2 .8 6 0. 65 0. 80 -6 .9 12 Id rij ca Tr eb uš či ca Tr ib ut ar y 46 .0 94 54 9 13 .8 32 34 4 18 8 8. 6 7. 77 3. 89 34 8. 0 1. 01 0. 86 0. 05 0. 01 0. 02 0. 07 29 .7 6 -2 .4 1 0. 16 0. 12 -8 .2 13 Id rij ca Ba ča Tr ib ut ar y 46 .1 44 88 8 13 .7 67 26 3 15 4 9. 2 8. 27 3. 09 28 2. 0 1. 17 0. 34 0. 08 0. 02 0. 06 0. 10 0. 04 -3 .0 1 0. 63 0. 62 -6 .6 14 Ka m ni šk a Bi st ric a Sp rin g Ri ve r 46 .3 25 73 44 14 .5 88 46 44 6 62 3 5. 9 7. 35 1. 93 16 0. 7 0. 73 0. 18 0. 05 0. 00 0. 01 0. 01 0. 01 0. 03 -2 .3 7 -0 .7 7 -2 .3 4 -3 .6 15 Ka m ni šk a Bi st ric a be fo re S ta ho vi ca Ri ve r 46 .2 85 67 75 3 14 .6 16 92 48 2 53 0 6. 5 8. 02 2. 74 21 1. 0 0. 96 0. 29 0. 07 0. 01 0. 01 0. 02 0. 02 0. 04 -2 .8 9 0. 15 -0 .3 9 -6 .7 16 Ka m ni šk a Bi st ric a aft er S ta ho vi ca Ri ve r 46 .2 58 67 67 5 14 .6 03 64 76 9 45 0 6. 8 8. 10 3. 00 22 5. 5 1. 00 0. 32 0. 07 0. 01 0. 03 0. 03 0. 03 0. 04 -2 .9 0 0. 28 -2 .9 5 -7 .3 17 Ka m ni šk a Bi st ric a Ka m ni k Ri ve r 46 .2 21 51 34 14 .6 10 34 33 8 37 8 7. 7 8. 15 3. 48 26 9. 3 1. 21 0. 35 0. 11 0. 02 0. 05 0. 06 0. 06 0. 06 -2 .9 1 0. 48 0. 28 -9 .2 18 Ka m ni šk a Bi st ric a Vi r Ri ve r 46 .1 47 10 26 9 14 .6 04 53 60 3 31 0 9. 3 8. 23 3. 51 27 7. 9 1. 29 0. 35 0. 12 0. 02 0. 06 0. 06 0. 07 0. 06 -2 .9 8 0. 61 0. 54 -9 .7 19 Ka m ni šk B ist ric a Do m ža le Ri ve r 46 .1 35 84 97 4 14 .6 02 77 83 7 30 0 9. 1 8. 18 3. 72 25 9. 7 1. 30 0. 39 0. 17 0. 02 0. 07 0. 07 0. 12 0. 07 -2 .9 1 0. 61 0. 59 -1 0. 1 20 Ka m ni šk a Bi st ric a Vi de m Ri ve r 46 .0 88 35 69 6 14 .6 25 94 16 8 26 0 9. 7 7. 92 4. 19 33 4. 8 1. 43 0. 45 0. 25 0. 03 0. 07 0. 08 0. 20 0. 11 -2 .5 9 0. 42 0. 24 -1 0. 7 21 Ka m ni šk a Bi st ric a Do lsk i G ra be n Tr ib ut ar y 46 .3 08 51 52 3 14 .6 06 99 00 3 57 0 7. 0 7. 82 3. 61 25 9. 7 1. 34 0. 19 0. 10 0. 01 0. 02 0. 03 0. 02 0. 05 -2 .5 7 0. 20 -0 .6 0 -1 0. 8 22 Ka m ni šk a Bi st ric a Bi st rič ic a Tr ib ut ar y 46 .2 86 06 50 1 14 .6 17 10 38 3 47 0 7. 3 8. 12 4. 31 26 7. 0 1. 27 0. 66 0. 11 0. 02 0. 07 0. 07 0. 04 0. 06 -2 .7 9 0. 54 0. 64 -1 0. 0 23 Ka m ni šk a Bi st ric a Čr na Tr ib ut ar y 46 .2 68 02 86 9 14 .6 17 10 38 3 47 0 6. 8 8. 26 3. 25 27 2. 6 1. 07 0. 41 0. 17 0. 02 0. 07 0. 07 0. 12 0. 09 -3 .0 6 0. 49 0. 41 -9 .9 24 Ka m ni šk a Bi st ric a N ev lji ca Tr ib ut ar y 46 .2 30 68 02 4 14 .6 37 50 48 3 46 0 8. 3 8. 04 4. 58 35 5. 6 1. 93 0. 22 0. 12 0. 01 0. 06 0. 09 0. 06 0. 10 -2 .6 8 0. 67 0. 28 -1 2. 6 25 Ka m ni šk a Bi st ric a Ra do m el jsk a M lin šč ic a Tr ib ut ar y 46 .1 72 51 45 5 14 .6 08 03 29 1 34 0 8. 3 8. 21 3. 55 27 4. 5 1. 24 0. 35 0. 11 0. 02 0. 05 0. 06 0. 06 0. 06 -2 .9 6 0. 56 0. 45 -9 .2 26 Ka m ni šk a Bi st ric a Pš at a Tr ib ut ar y 46 .1 60 32 59 9 14 .5 93 30 62 7 33 8 8. 4 8. 07 3. 90 30 9. 1 1. 46 0. 33 0. 16 0. 03 0. 10 0. 08 0. 11 0. 10 -2 .7 8 0. 53 0. 29 -1 2. 1 27 Ka m ni šk a Bi st ric a Ra ča Tr ib ut ar y 46 .1 44 01 04 7 14 .6 16 06 56 4 31 0 9. 0 8. 03 3. 92 32 9. 1 1. 29 0. 52 0. 30 0. 04 0. 09 0. 10 0. 25 0. 09 -2 .7 3 0. 45 0. 39 -1 2. 7 28 Ka m ni šk a Bi st ric a Ho m šk a M lin šč ic a Tr ib ut ar y 46 .0 95 43 70 8 14 .6 25 63 53 9 29 0 8. 8 8. 25 3. 45 27 6. 4 1. 21 0. 35 0. 15 0. 02 0. 00 0. 07 0. 09 0. 07 -3 .0 1 0. 59 0. 52 -8 .8 29 Ka m ni šk a Bi st ric a Pš at a ch an ne l Tr ib ut ar y 46 .0 88 35 69 6 14 .6 25 94 16 8 28 0 9. 5 7. 93 4. 12 33 8. 0 1. 51 0. 42 0. 17 0. 03 0. 09 0. 09 0. 13 0. 11 -2 .6 1 0. 44 0. 23 -1 2. 6 30 Sa va Sa va D ol in ka , s pr in g Ri ve r 46 .4 92 38 10 8 13 .7 37 38 95 8 83 0 5. 6 7. 54 2. 63 27 9. 0 0. 91 0. 47 0. 07 0. 01 0. 02 0. 05 0. 07 0. 03 -2 .4 4 -0 .3 9 -1 .2 5 -7 .8 31 Sa va Sa va D ol in ka , P od ko re n Ri ve r 46 .4 91 08 96 13 .7 62 49 57 2 82 9 7. 1 7. 56 2. 67 38 0. 0 0. 93 0. 47 0. 13 0. 00 0. 05 0. 10 0. 30 0. 03 -2 .4 5 -0 .3 4 -1 .1 2 -8 .6 32 Sa va Pi šn ic a at K ra nj sk a go ra Tr ib ut ar y 46 .4 74 64 47 9 13 .7 81 97 23 4 81 9 7. 6 7. 82 3. 36 23 9. 0 0. 86 0. 44 0. 05 0. 02 0. 01 0. 05 0. 04 0. 03 -2 .6 1 -0 .0 1 -0 .4 4 -5 .4 33 Sa va Sa va D ol in ka , D ov je Ri ve r 46 .4 62 65 05 9 13 .9 53 93 19 6 70 4 8. 5 7. 86 2. 65 28 6. 0 1. 00 0. 51 0. 07 0. 02 0. 03 0. 40 0. 06 0. 06 -2 .7 6 -0 .0 4 -0 .5 0 -7 .3 34 Sa va Sa va D ol in ka , Š ob ec Ri ve r 46 .3 67 97 84 9 14 .1 34 64 50 5 45 9 10 .7 8. 31 3. 06 31 1. 0 1. 12 0. 51 0. 10 0. 01 0. 03 0. 19 0. 12 0. 06 -3 .1 4 -0 .5 8 0. 73 -7 .3 17Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... G IS _ ID N am e Ri ve r Ty pe LA T (° ) LO N (° ) Z (m ) T (° C) pH Al ka l. m m ol /L EC µS /c m Ca 2+ m m ol /L M g2 + m m ol /L N a+ m m ol /L K+ m m ol /L Si m m ol /L SO 42 - m m ol /L Cl - m m ol /L N O 3- m m ol /L pC O 2 ba r SI ca l SI do l δ1 3 C DI C (‰ ) 35 Sa va Ri ve r S av ic a Tr ib ut ar y 46 .2 90 39 11 7 13 .8 02 50 16 7 70 0 6. 0 8. 08 2. 19 19 0. 0 0. 75 0. 23 0. 01 0. 00 0. 01 0. 03 0. 01 0. 03 -3 .0 6 0. 01 -0 .6 8 -3 .3 36 Sa va La ke B oh in j, ou tle t Tr ib ut ar y 46 .2 78 39 8 13 .8 86 34 17 55 7 9. 5 7. 85 4. 11 36 9. 0 2. 33 0. 51 0. 28 0. 02 0. 04 0. 06 0. 24 0. 09 -2 .5 6 0. 52 0. 28 -1 2. 8 37 Sa va Sa va B oh in jk a, N om en j Tr ib ut ar y 46 .2 98 01 52 6 14 .0 37 57 24 9 50 9 12 .0 8. 11 2. 69 24 7. 0 1. 08 0. 24 0. 04 0. 01 0. 02 0. 08 0. 08 0. 05 -2 .9 8 0. 35 -0 .0 1 -7 .2 38 Sa va Sa va O to če c Ri ve r 46 .3 12 16 99 7 14 .2 37 44 78 4 41 5 12 .2 8. 26 3. 24 30 5. 0 1. 18 0. 47 0. 11 0. 03 0. 03 0. 15 0. 10 0. 05 -3 .0 6 0. 60 0. 74 -7 .3 39 Sa va Tr žiš ka B ist ric a, B ist ric a Tr ib ut ar y 46 .2 90 11 45 8 14 .2 84 42 50 3 42 2 11 .3 8. 44 2. 81 37 8. 0 1. 38 0. 60 0. 11 0. 01 0. 05 0. 58 0. 06 0. 04 -3 .3 1 0. 73 1. 04 -6 .4 40 Sa va Ko kr a, K ra nj Tr ib ut ar y 46 .2 52 04 69 9 14 .3 68 69 10 4 40 7 10 .7 8. 20 3. 22 33 3. 0 1. 23 0. 54 0. 09 0. 01 0. 05 0. 21 0. 06 0. 05 -3 .0 1 0. 53 0. 61 -7 .5 41 Sa va Sa va , K ra nj Ri ve r 46 .2 37 82 81 3 14 .3 52 02 31 8 35 0 14 .7 7. 57 3. 22 63 2. 0 1. 38 0. 52 0. 17 0. 01 0. 04 0. 18 0. 19 0. 10 -2 .3 5 0. 02 -0 .4 1 -8 .8 42 Sa va Sa va , S m le dn ik Ri ve r 46 .1 64 19 81 6 14 .4 25 55 63 3 33 6 12 .8 8. 17 4. 76 30 7. 0 1. 22 0. 42 0. 11 0. 02 0. 03 0. 13 0. 10 0. 06 -2 .8 0 0. 69 0. 87 -8 .1 43 Sa va So ra , L ad ja Tr ib ut ar y 46 .1 43 58 73 2 14 .3 92 85 26 6 31 3 12 .5 7. 48 4. 51 37 9. 0 1. 38 0. 63 0. 19 0. 05 0. 07 0. 15 0. 19 0. 15 -2 .1 3 0. 03 -0 .3 3 -1 0. 5 44 Sa va Sa va , T ac en Ri ve r 46 .1 17 22 40 1 14 .4 61 18 30 4 28 0 13 .2 7. 32 2. 99 37 9. 0 0. 00 0. 00 0. 13 0. 11 0. 07 -2 .1 1 -8 .6 45 Sa va Ka m ni šk a Bi st ric a, Be rič ev o Tr ib ut ar y 46 .0 88 42 29 1 14 .6 26 48 00 2 26 0 13 .8 7. 74 4. 60 55 4. 0 1. 72 0. 58 0. 74 0. 17 0. 07 0. 18 0. 51 0. 69 -2 .3 8 0. 39 0. 29 -9 .3 46 Sa va Lj ub lja ni ca , Z al og Tr ib ut ar y 46 .0 62 20 61 7 14 .6 21 69 26 8 26 7 15 .7 7. 93 4. 79 50 0. 0 1. 72 0. 74 0. 52 0. 06 0. 04 0. 14 0. 46 0. 10 -2 .5 4 0. 62 0. 88 -1 1. 8 47 Sa va Sa va , D ol sk o Ri ve r 46 .0 87 99 49 6 14 .6 78 35 02 7 26 5 14 .0 8. 08 3. 44 36 6. 0 1. 34 0. 50 0. 23 0. 04 0. 04 0. 15 0. 19 0. 12 -2 .8 4 0. 52 0. 59 -9 .9 48 Sa va Je vn ic a, Je vn ic a Tr ib ut ar y 46 .0 83 60 96 5 14 .7 37 19 53 3 24 0 11 .9 7. 24 0. 84 11 8. 5 0. 30 0. 14 0. 16 0. 03 0. 19 0. 08 0. 09 0. 03 -2 .6 0 -1 .5 1 -3 .4 2 -9 .0 49 Sa va Sa va , K re sn ic e Ri ve r 46 .0 96 32 92 9 14 .7 73 95 62 3 23 5 11 .5 7. 29 3. 58 38 7. 0 1. 45 0. 49 0. 18 0. 04 0. 05 0. 15 0. 14 0. 10 -2 .0 4 -0 .2 5 -1 .0 3 -1 1. 8 50 Sa va Sa va , L iti ja Ri ve r 46 .0 56 46 17 1 14 .8 20 51 44 7 23 0 12 .1 7. 81 3. 48 39 3. 0 1. 48 0. 49 0. 23 0. 05 0. 05 0. 15 0. 18 0. 12 -2 .5 7 0. 27 0. 01 -1 0. 9 51 Sa va Re ka p ri Br eg u, L iti ja Tr ib ut ar y 46 .0 59 62 08 6 14 .8 46 14 68 4 24 5 13 .6 7. 89 3. 93 41 6. 0 0. 00 0. 00 0. 15 0. 30 0. 11 -2 .5 7 -1 1. 6 52 Sa va Sa va , L og Ri ve r 46 .0 85 63 08 3 14 .8 92 06 99 9 23 0 13 .6 8. 32 3. 81 37 8. 0 1. 44 0. 49 0. 17 0. 03 0. 05 0. 14 0. 14 0. 10 -3 .0 5 0. 81 1. 13 -1 0. 2 53 Sa va Po lšn ik , S av a Tr ib ut ar y 46 .0 83 37 90 1 14 .9 23 08 09 1 26 0 12 .7 8. 34 2. 59 31 6. 0 0. 00 0. 00 0. 18 0. 09 0. 03 -3 .2 0 1. 13 -1 0. 4 54 Sa va M ed ija , Z ag or je Tr ib ut ar y 46 .1 21 25 63 8 14 .9 94 34 95 3 24 0 18 .5 8. 64 4. 89 57 4. 0 1. 69 1. 00 0. 41 0. 09 0. 11 0. 31 0. 26 0. 12 -3 .2 7 1. 31 -1 1. 0 55 Sa va Sa va , Za go rje Ri ve r 46 .1 18 89 00 3 14 .9 94 55 67 1 22 5 13 .7 8. 35 3. 63 40 3. 0 1. 49 0. 52 0. 18 0. 02 0. 06 0. 15 0. 16 0. 10 -3 .0 1 0. 92 2. 44 -9 .8 56 Sa va Šk le nd ro ve c, Z ag or je Tr ib ut ar y 46 .1 03 01 83 3 15 .0 02 15 04 6 35 0 14 .7 8. 74 5. 15 48 7. 0 1. 52 0. 00 0. 12 0. 00 0. 06 0. 24 0. 11 0. 05 -3 .3 7 1. 33 1. 35 -1 0. 1 57 Sa va M ito vš ic a, T rb ov lje Tr ib ut ar y 46 .1 19 71 80 6 15 .0 42 99 91 1 35 0 15 .0 8. 72 4. 03 41 4. 0 1. 54 0. 55 0. 06 0. 03 0. 04 0. 23 0. 07 0. 07 -3 .4 4 1. 24 2. 53 -1 0. 9 58 Sa va Tr bo ve ljš či ca , T rb ov lje Tr ib ut ar y 46 .1 61 92 11 7 15 .0 52 68 00 8 23 0 12 .5 8. 04 4. 22 51 2. 0 1. 41 1. 00 0. 71 0. 10 0. 15 0. 13 0. 10 0. 06 -2 .7 2 0. 55 2. 04 -1 1. 4 59 Sa va Sa va , T rb ov lje Ri ve r 46 .1 26 21 67 1 15 .0 36 32 72 3 22 0 17 .2 8. 48 3. 54 40 3. 0 1. 48 0. 52 0. 22 0. 04 0. 05 0. 18 0. 16 0. 11 -3 .2 3 0. 99 0. 90 -1 0. 9 60 Sa va Sa va , H ra st ni k Ri ve r 46 .1 21 55 11 3 15 .0 91 62 58 21 0 13 .5 8. 52 3. 45 37 6. 0 1. 43 0. 51 0. 19 0. 04 0. 05 0. 15 0. 15 0. 17 -3 .3 0 0. 96 1. 56 -1 0. 2 61 Sa va Bo be n, H ra st ni k Tr ib ut ar y 46 .1 50 57 26 4 15 .0 85 92 69 4 22 0 17 .3 8. 34 3. 42 57 5. 0 1. 67 1. 01 0. 77 0. 12 0. 13 0. 44 0. 41 0. 10 -3 .1 1 0. 87 1. 44 -1 1. 6 62 Sa va Sa vi nj a, R im sk e To pl ic e Tr ib ut ar y 46 .1 22 62 89 5 15 .2 03 28 14 7 20 0 14 .3 8. 82 3. 42 47 3. 0 1. 62 0. 56 0. 68 0. 08 0. 10 0. 51 0. 34 0. 12 -3 .6 3 1. 25 -1 0. 2 63 Sa va Sa va , R ad eč e Ri ve r 46 .0 65 52 03 9 15 .1 88 17 90 6 19 3 14 .4 8. 54 3. 36 39 7. 0 1. 46 0. 53 0. 32 0. 04 0. 06 0. 24 0. 21 0. 10 -3 .3 3 0. 98 1. 55 -9 .9 64 Sa va M irn a, D ol B os ta nj Tr ib ut ar y 46 .0 04 25 24 15 .2 88 07 39 6 19 1 14 .4 8. 99 5. 49 51 1. 0 1. 73 1. 15 0. 23 0. 09 0. 09 0. 18 0. 14 0. 05 -3 .6 3 1. 59 2. 04 -1 1. 2 65 Sa va Sa va , B re st an ic a Ri ve r 45 .9 87 08 88 2 15 .4 65 96 94 7 15 0 14 .6 8. 63 3. 60 45 3. 0 0. 00 0. 00 0. 25 0. 23 0. 12 -3 .3 5 1. 51 -1 0. 4 66 Sa va Sa va , B re žic e Ri ve r 45 .8 97 94 94 5 15 .5 91 47 52 5 14 5 14 .4 7. 86 3. 29 42 8. 0 1. 57 0. 56 0. 37 0. 06 0. 07 0. 28 0. 24 0. 11 -2 .6 4 0. 35 3. 01 -1 0. 8 67 Sa va Kr ka , Č at ež Tr ib ut ar y 45 .8 94 36 14 2 15 .5 91 06 33 4 14 0 14 .5 8. 77 4. 65 45 9. 0 0. 00 0. 00 0. 10 0. 16 0. 12 -3 .0 9 -1 1. 1 68 Sa va Sa va , M os te c Ri ve r 45 .8 95 65 40 1 15 .6 26 99 19 7 14 0 14 .7 8. 20 3. 74 41 2. 0 1. 49 0. 54 0. 34 0. 05 0. 06 0. 27 0. 23 0. 10 -2 .9 3 0. 71 0. 97 -1 1. 5 69 Sa va So tla , R ak ov ec Tr ib ut ar y 45 .9 20 58 24 4 15 .7 04 79 52 1 14 0 12 .4 8. 61 6. 02 63 0. 0 2. 38 0. 84 0. 67 0. 17 0. 16 0. 39 0. 39 0. 13 -3 .1 8 1. 41 2. 33 -1 2. 2 70 Sa va Sa va , B re ga na Ri ve r 45 .8 61 10 49 3 15 .6 91 78 09 1 13 5 14 .0 7. 93 3. 51 42 4. 0 1. 52 0. 55 0. 30 0. 05 0. 06 0. 22 0. 06 0. 04 -2 .6 8 0. 42 0. 37 -1 0. 8 18 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK Europa-Scientific 20-20 continuous flow IRMS ANCA-SL preparation module. For POC 1 L of the water sample was filtered through a What- man GF/F glass fiber filter (0.7 mm). Filters and soil were treated with 1 M HCl to remove car- bonate. Thermodynamic geochemical modeling was used to evaluate CO2 partial pressures (pCO2) and the saturation state of calcite and dolomite (SIcalcite and SIdolomite) using pH, alkalinity, and temperature as inputs to the PHREEQC specia- tion program (ParKhurst & aPPelo, 1999). Results and discussion Aquatic geochemistry of selected gravel bed rivers in Slovenia The temperature of surface water in River Kamniška Bistrica, pH and conductivity ranged from 1.7 to 26.6 °C, 7.1 to 8.8, and 160.7 to 497.4 mS/cm. DO saturation varied seasonally from 59.6 to 76.8 % in the winter and from 68 to 140 % (Kanduč et al., 2013). In River Idrijca water tem- perature was 7.3 to 13.0 °C, conductivity ranged from 181 to 465 mS/cm, pH ranged from 7.77 to 8.82 (Kanduč et al., 2008). Temperature in River Sava water ranged from 0.4 to 15.7 °C, conductiv- ity ranged from 62.3 to 632 mS/cm and pH ranged from 7.24 to 8.99, respectively (Kanduč, 2006; Kanduč et al., 2007). All results are described in detail in Kanduč et al. (2007, 2008 and 2013). The major solute composition of selected grav- el-bed rivers was dominated by HCO3 -, Ca2+ and Mg2+. Concentrations varied seasonally accord- ing to discharge, with higher concentrations ob- served in autumn at lower discharge and lower concentrations during the spring sampling sea- son. Dissolved Ca2+ and Mg2+ are largely supplied by the weathering of carbonates (Fig. 3), which are the most dominant rocks in the watersheds, and prone to chemical dissolution, with small- er contributions from silicate weathering, as indicated by the relatively high HCO3 - and low Si concentrations (Kanduč, 2006; Kanduč et al., 2007, 2008 and 2013). Figure 3 presents Ca2+ + Mg2+ versus alkalini- ty for all three selected gravel bed rivers in Slo- venia. Most of the samples have a 2:1 mole ratio of HCO3 - to Ca2+ + Mg2+ following the reactions (GaillarDet et al., 1999): Calcite: CaCO3 + CO2 + H2O ⇔ Ca 2+ + 2HCO3 - (1) Dolomite: Ca0.5Mg0.5(CO3) + CO2 + H2O ⇔ Ca 2+ + Mg2+ + 2HCO3 - (2) Some samples deviate from 2:1 line due to weathering of other minerals in river watershed, like albite and anorthite: CaAl2Si2O8 + 3H2O+2CO2 → Anorthite Al2Si2O5(OH)4 + Ca 2+ + 2HCO3 - (3) Kaolinite NaAlSi3O8 + CO2 + 11/2 H2O → Albite Na+ + ½ Al2Si2O5(OH)4+2H4SiO4+HCO3 - (4) Kaolinite The pH, temperature and pCO2 of a watershed determine the carbonate speciation, controlling the HCO3 - carrying capacity. In Slovenian watersheds, total alkalinity comprises carbonate alkalinity (Kanduč, 2006; Kanduč et al., 2007), and therefore the total alkalinity is assumed as HCO3 -, which is also the main DIC species at the pH of 7.0 to 9.0 measured in all investigated watersheds. Concen- trations of HCO3 - in main channel of River Kam- niška Bistrica (Fig. 3A) vary seasonally from 1.93 to 4.19 mM in autumn 2010, from 1.88 to 4.99 mM in winter 2011, from 1.55 to 4.39 mM in spring 2011 and from 1.70 to 5.57 mM in summer 2011, respectively. Concentrations of HCO3 - (alkalinity) in tributaries vary seasonally and range from 3.25 to 4.58 mM in autumn 2010 (Fig. 3A). The alkalin- ity concentrations in the main channel sampling sites varied seasonally in River Sava (Fig. 3B) in the main channel from 2.60 to 3.75 mM in spring, from 2.63 to 4.79 mM in late summer 2004, and from 2.67 to 4.17 mM during winter. The upper al- pine headwater catchments of the River Sava have thin soils developed on carbonate bedrock. In the central and lower part of the River Sava water- shed, tributary streams have more variable alka- linity concentrations, ranging from about 0.39 to 6.02 mM (Kanduč et al., 2007). River Idrijca (Fig. 3C) had alkalinities in range from 3.88 to 4.66 mM in autumn 2006 and from 4.12 to 4.43 mM in spring 2007, while in tributaries alkalinities range from 3.09 to 5.10 mM in autumn 2006 and in spring 2007 from 3.15 to 5.04 mM (Kanduč et al., 2008). Differences in alkalinities in carbonate-bear- ing watersheds are related to the geological com- position of the watershed (Fig. 2), the relief (Fig. 1), the mean annual temperature, the depth of the weathering zone, the soil thickness and the water residence time in the system. Weathering rates in- 19Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... crease in thicker soils like shales due to the high- er residence time of shallow groundwater in con- tact with minerals in comparison to watersheds composed of carbonate minerals. Mg2+ versus Ca2+ relations indicate the rela- tive contribution of calcite/dolomite to carbonate weathering intensity in gravel bed rivers (Fig. 4). Most of the samples indicate that weathering of calcite is dominant over the entire River Kamniš- ka Bistrica, especially in the upper and central reaches (Fig. 4A). A Mg2+/Ca2+ ratio around 0.33 is typical for weathering of calcite for the entire length of the River Kamniška Bistrica as well as for rivers comprising Danube watershed (Kan- duč et al., 2013). In contrast, rivers comprising St. Lawrence watershed (North America) have ratios Mg2+/Ca2+ greater than 0.33 (szraMeK et al., 2007). Most of the samples in River Sava (Fig. 4B) fall below 0.22 line, indicating weathering of calcite, only some samples in River Sava tributaries fall above 0.5 Mg2+/Ca2+ line indicating weathering of dolomite. From Figure 4C it can be observed that most of the samples indicate that weathering of dolomite is dominant over the entire River Idrijca, 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 C a2 + + M g2 + (m M ) Alkalinity (mM) Kamniška Bistrica River, autumn 2010 tributaries, autumn 2010 Kamniška Bistrica River, winter 2011 tributaries, winter 2011 Kamniška Bistrica River, spring 2011 tributaries, spring 2011 Kamniška Bistrica River, summer 2011 2 HCO3- = Ca2+ + Mg2+ A 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 C a2 + + M g2 + (m M ) Alkalinity (mM) Sava River spring 2004 Sava River late summer 2004 Sava River winter 2005 tributaries spring 2004 tributaries late summer 2004 tributaries winter 2005 2 HCO3- = Ca2+ + Mg2+ B 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Idrijca River, autumn 2006 tributaries, autumn 2006 Idrijca River, spring 2007 tributaries, 2007 2 HCO3- = Ca2+ + Mg2+ C Alkalinity (mM) C a2 + + M g2 + (m M ) Fig. 3. Ca2++Mg2+ ratio versus alkalinity with line 1: 2 indi- cating weathering of carbonates in the watershed (rivers: A: Kamniška Bistrica, B: Sava in Slovenia, C: Idrijca). 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 M g2 + (m M ) Ca2+ (mM) Kamniška Bistrica River, late summer 2010 tributaries, late summer 2010 Kamniška Bistrica River, winter 2011 tributaries, winter 2011 Kamniška Bistrica River, spring 2011 tributaries, spring 2011 Dolomite only Calcite only Mg2+/Ca2+<0.1 Mg2+/Ca2+=0.33 Mg2+/Ca2+=0.5 Mg2+/Ca2+=0.75 Mg2+/Ca2+=1 A 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 Sava River, spring 2004 Sava River, late summer 2004 Sava River, winter 2005 tributaries, spring 2004 tributaries, late summer 2004 tributaries, winter 2005 Mg2+/Ca2+=1 Mg2+/Ca2+=0.75 Mg2+/Ca2+=0.5 Mg2+/Ca2+=0.33 Mg2+/Ca2+< 0.1 Dolomite only Calcite only B 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 Idrijca River, autumn 2006 tributaries, autumn 2006 Idrijca River, spring 2007 tributaries, spring 2007 Dolomite only Mg2+/Ca2+=1 Mg2+/Ca2+ = 0.75 Mg2+/Ca2+ = 0.5 Mg2+/Ca2+ = 0.33 Mg2+/Ca2+ < 0.1 Calcite only M g2 + (m M ) M g2 + (m M ) Ca2+ (mM) Ca2+ (mM) C Fig. 4. Mg2+ versus Ca2+ indicating weathering of calcite and dolomite in watershed (rivers: A: Kamniška Bistrica, B: Sava in Slovenia, C: Idrijca). 20 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK especially in the upper and central flow of the riv- er. A Mg2+/Ca2+ ratio around 0.33 is characteristic only in the lowland tributaries of the River Idrijca composed mainly of limestone. The major control on carbonate weathering in- tensity is runoff (aMiotte suchet & ProBst, 1993). Carbonate weathering intensity normalized to drainage area, quantifies HCO3 - produced from mineral weathering. Figure 5 compares carbonate weathering intensities as a function of specific runoff for the River Idrijca watershed, combining new data from this study with published official data for the River Sava, River Kamniška Bistrica and data from berner & berner (1996) for world rivers and the River Danube. Global theoretical models of CO2 consumption in carbonate water- sheds show an alkalinity value around 3 mmol/L determined from a best-fit line (aMiotte suchet & ProBst, 1993). The climate and topographic relief in Slovenian watersheds importantly influence the carbonate weathering intensity and specific runoff. roy et al. (1999) noted that linked factors such as lithology, residence time of water, me- chanical erosion, etc., have more influence togeth- er than they do separately. The watershed of the River Idrijca is typically an environment where enhanced mechanical weathering increases chemical weathering (FairchilD et al., 1999; an- Derson et al., 2000; jacoBson et al., 2000) and caus- es a high carbonate weathering intensity, since the river is a steep mountain river with torrential character, e.g. River Idrijca with 80 mmol/l·km2·s (Fig. 5) and Kamniška Bistrica with the highest weathering intensity of 150 mmol/l·km2·s (Fig. 5). The world average value for carbonate weath- ering intensity is 7 mmol/l km2 s (Berner & Bern- er, 1996). For the River Sava and its tributaries, the mean long term weathering intensity is from 37 to 140 mmol/l km2 s. Also carbonate weathering intensity (HCO3 - in mmol/l km2 s) of some other world rivers (Mis- sissippi, World, Danube) is presented on Figure 5. From Figure 5 it can be observed that Slovenian gravel bed rivers have higher HCO3 - weathering intensity in comparison to world rivers. Thermodynamic modeling and isotope geochemistry with emphasize on carbon cycle Thermodynamical modeling software PHREEQC for Windows was used to calculate pCO2 and saturation indices for calcite and do- lomite (SIcalcite and SIdolomite) along the main water channel and tributaries. In all investigated bed rivers a high value of pCO2 was observed during all sampling seasons, meaning that rivers repre- sent sources of CO2 into air. Calculated pCO2 varied from 977 to 4,169 ppm in autumn and from 295 to 2,398 ppm in the spring sampling season. Normal atmospheric pressure is around 316 ppm according to clarK & Fritz (1997). Calculated pCO2 varied from near atmospheric up to 25-fold supersaturated at River Kamniška Bistrica at Videm in summer season in year 2010 to 2011. Partial pressure in River Sava and its tributaries ranges from 128.8 to 2,951 ppm in April 2004, in September 2004 0 50 100 150 200 250 0.0 20.0 40.0 60.0 80.0 100.0 H C O 3- W ea th er in g in te ns ity (m m ol /(l ·k m ·s ) Specific runoff (l/km2·s) Sava River- Jesenice Kamniška Bistrica River- Beri�evo Danube River Mississippi River World Idrijca River- Hotešk 5 mmol/l 4 mmol/l 3 mmol/l 2 mmol/l 1 mmol/l silicate weathering <0.5 mmol/l 2 Fig. 5. Carbonate weathe- ring intensity (HCO3 - in mmol/l km2 s) versus speci- fic runoff (1/km2s) indicating high carbonate weathering intensity in selected rivers in Slovenia (River Kamniška Bistrica, River Sava in Slovenia, River Idrijca) and in the world. Data include mean long-term data of di- scharge and alkalinity from the Slovenian Environment Agency (2004-2011) for the Slovenian rivers, and Berner & berner (1996) for world rivers, River Danube and Mississipi River. 21Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... from 234.4 to 9,120 ppm in April and from 223.9 to 4,074 ppm in January 2005 (Kanduč, 2006). In autumn all sampling locations on the River Id- rijca watershed are above equilibrium with at- mospheric CO2. These higher partial pressures in autumn are probably due to higher degradation of organic matter in the river and due to lower discharge (Dever et al., 1983). Lower pCO2 (below normal atmospheric pressure at locations 5 and 6, Table 1, Fig.1) in the spring are observed due to the higher pH of the water, which lowers the evasion of CO2 from water. The calcite saturation index (SIcalcite=log([- Ca2+]*[CO3 2-])/Kcalcite; where Kcalcite is the solubility product of calcite and was generally well above equilibrium (SIcalcite=0)), indicates that calcite was supersaturated and precipitation was thermody- namically favoured along most of the course of all selected gravel bed rivers in Slovenia (Fig. 6). Calcite and dolomite were supersaturated and carbonate precipitation was thermodynamically favoured along most of the course of River Kam- niška Bistrica (Fig. 6A). SIcalcite and SIdolomite sea- sonally change in River Sava and their tributar- ies and reach oversaturation in central and lower flow of the river, while in upper part of the river rarely reach saturation (Fig. 6B). Low SIcalcite and SIdolomite are observed at tributary location of Riv- er Sava (Fig. 6B). In most of the samples of River Idrijca and its tributaries calcite and dolomite are oversaturated, only one sample in River Id- rijca is undersaturated with respect to dolomite (Fig. 6C). Mass balance calculation with evaluation of biogeochemical processes in selected gravel bed rivers in Slovenia Mass balance calculations were performed in previous studies (Kanduč et al., 2007, 2008 and 2013). The δ13CDIC value can determine the contribu- tions of organic matter decomposition, carbonate mineral dissolution, and exchange with atmos- pheric CO2 to DIC in selected gravel bed rivers in Slovenia. The δ13CDIC values of the main chan- nel of the river varied seasonally (year 2010-2011) from -10.9 ‰ (River Kamniška Bistrica, location 20, Table 1, Fig. 1) to -2.7 ‰ (River Kamniška Bistrica Spring, location 14, Table 1, Fig. 1) while δ13CDIC in tributaries ranged from -12.7 ‰ (Rača, location 27, Table 1, Fig.1) to -6.9 ‰ (Kamniška Bistrica Spring, location 14, Table 1, Fig.1) (Kan- duč et al., 2013). The δ13CDIC in River Sava varied seasonally from -12.7 to -8.6 ‰ in spring 2004, from -11.8 to -7.3 ‰ in late summer 2004 and from -10.6 to -6.3 ‰ in winter 2005. The River Sava tributaries had δ13CDIC values that varied from -13.5 to -5.8 ‰ in spring 2004, from -12.8 to 3.3 ‰ -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Kamniška Bistrica River, late summer 2010 tributaries, late summer 2010 Kamniška Bistrica River, winter 2011 tributaries, winter 2011 Kamniška Bistrica River, spring 2011 tributaries, spring 2011 Kamniška Bistrica River, summer 2011 tributaries, summer 2011 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Sava River, spring 2004 tributaries, spring 2004 Sava River, late summer 2004 tributaries, late summer, 2004 Sava River, winter 2004 tributaries, winter 2004 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Idrijca River, autumn 2006 tributaries, autumn 2006 Idrijca River, spring 2007 tributaries, spring 2007 A B C -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Kamniška Bistrica River, late summer 2010 tributaries, late summer 2010 Kamniška Bistrica River, winter 2011 tributaries, winter 2011 Kamniška Bistrica River, spring 2011 tributaries, spring 2011 Kamniška Bistrica River, summer 2011 tributaries, summer 2011 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Sava River, spring 2004 tributaries, spring 2004 Sava River, late summer 2004 tributaries, late summer, 2004 Sava River, winter 2004 tributaries, winter 2004 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Idrijca River, autumn 2006 tributaries, autumn 2006 Idrijca River, spring 2007 tributaries, spring 2007 A B C -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Kamniška Bistrica River, late summer 2010 tributaries, late summer 2010 Kamniška Bistrica River, winter 2011 tributaries, winter 2011 Kamniška Bistrica River, spring 2011 tributaries, spring 2011 Kamniška Bistrica River, summer 2011 tributaries, summer 2011 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Sava River, spring 2004 tributaries, spring 2004 Sava River, late su er tributaries, late summer, 2004 Sava River, winter 2004 tributaries, winter 2004 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 SI do lo m ite SIcalcite Idrijca River, autumn 2006 tributaries, autumn 2006 Idrijca River, spring 2007 tributaries, spring 2007 A B C Fig. 6. SIcalcite versus SIdolomite in different sampling seasons in different periods for the selected rivers (A: Kamniška Bistrica, B: Sava in Slovenia, C: Idrijca). 22 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK in late summer 2004, and from -11.9 to -4.2 ‰ in winter 2005 (Kanduč et al., 2007). δ13CDIC var- ied seasonally in River Idrijca watershed from -10.8 to -9.0 ‰ in autumn 2006 and from -10.6 to -8.3 ‰ in spring 2007. The δ13CDIC value of the river water is controlled by the geological com- position of the watershed. Along the River Idrij- ca flow the dissolution of carbonates is the major contributor to δ13CDIC values, but some parts of the watershed also drain shales, mudstones, and sandstones (Kanduč et al., 2008). Thus, in those parts δ13CDIC is much lower (central part of the River Idrijca, lower reaches of River Kamniška Bistrica and central and lower flow of River Sava in Slovenia) since the thickness of soil is on this bedrock much higher and soil CO2 contributes much more to DIC than on carbonate bedrocks. δ13CDIC was also generally lower during spring season at higher discharge (Fig. 7). The average δ13C value of Mesozoic carbonate rocks (δ13CCaCO3) in the hinterland of River Kamniška Bistrica is +2.4 ‰ (Kanduč et al., 2013). The δ13C of Meso- zoic carbonate rocks (δ13CCaCO3) from the River Sava watershed ranged from -1.4 to +2.7 ‰, with an average of +1.4±1.3 ‰ (N=12) (Kanduč et al., 2007). The δ13C value of Mesozoic carbonate rocks (δ13CCaCO3), which forms the slopes in the water- shed of the River Idrijca is on average +2.0±0.7 ‰ (N = 8) (Kanduč et al., 2008). Figure 7 shows a plot of δ13CDIC versus alka- linity in different sampling seasons for selected gravel bed rivers in Slovenia. Changes over the course of the rivers indicate processes affecting δ13CDIC, e. g. degradation of organic matter (line 3), carbonate mineral dissolution (line 2), and equi- libration with atmospheric CO2 (line 1) (Barth et al., 2003). At River Kamniška Bistrica source carbonate dissolution prevails, while in central and lower part of the river degradation of organic matter and dissolution of carbonates prevails (Fig. 7A). The δ13CDIC values from the River Idrijca water- shed (Fig. 7C) indicate that nonequilibrium car- bonate dissolution predominates along the flow of river, since the watersheds are mainly com- posed of carbonate rocks with inclusions of clas- tic rocks, approaching a δ13CDIC value of -12.3 ‰. In tributaries of the River Idrijca watershed (Fig. 7C), River Kamniška Bistrica (Fig. 7A) and Riv- er Sava in Slovenia (Fig. 7B) dissolution of car- bonate minerals prevails, which leads to higher δ13CDIC values. Mineralization of organic matter appears to be the dominant source of δ13CDIC along the Idrijca flows (Fig. 7C), where the greater soil thickness enables accumulation of soil CO2 due to the greater degree of silicate rock weathering, which leads to more a negative δ13CDIC. The evasion of CO2 from the River Kamniška Bistrica, River Sava in Slovenia and River Idri- jca can be calculated (equation 5) based on the thin-film diffusive gas exchange model (BroecK- er, 1974; rayMonD et al., 2012): [DIC]ex =D/z * ([CO2]eq - [CO2]) (5) where D is the CO2 diffusion coefficient in wa- ter of 1.26 *10-5 cm2/s at a temperature of 10 °C -18.0 -16.0 -14.0 -12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 13 C D IC (‰ ) Alkalinity (mM) Kamniška Bistrica River,late summer 2010 tributaries, late summer 2010 Kamniška Bistrica River, winter 2011 tributaries, winter 2011 Kamniška Bistrica River, spring 2011 tributaries, spring 2011 2 1 3 -18.0 -16.0 -14.0 -12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 13 C D IC (‰ ) Sava River , spring 2004 Sava River, late summer 2004 Sava River, winter 2005 tributaries, spring 2004 tributaries, summer 2004 tributaries, winter 2005 -18.00 -16.00 -14.00 -12.00 -10.00 -8.00 -6.00 -4.00 -2.00 0.00 2.00 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 13 C D IC (‰ ) Idrijca River, autumn 2006 tributaries, autumn 2006 Idrijca River, spring 2007 tributaries, spring 2007 C B A Alkalinity (mM) Alkalinity (mM) 1 2 3 2 3 1 Fig. 7. δ13CDIC versus alkalinity of selected gravel bed ri- vers in Slovenia (rivers: A: Kamniška Bistrica, B: Sava in Slovenia, C: Idrijca). 23Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... and 1.67 *10-5 cm2/s at a temperature of 20 °C (jähne et al., 1987), and z is the empirical thick- ness of the liquid layer [cm]. A simple isotopic mass balance calculation was performed in order to quantify different sources of DIC in all three selected gravel bed rivers: at River Kamniška Bistrica mouth (location 20, Ta- ble 1, Fig.1), at the River Idrijca mouth (location 6, Table 1, Fig. 1), at River Sava in Slovenia mouth (location 70, Table 1, Fig.1) considering the sum of tributary inputs and biogeochemical process- es in the watershed. The major inputs to the DIC flux (DICRI) and δ 13CDIC originate from tributaries (DICtri), degradation of organic matter (DICorg), exchange with the atmosphere (DICex), and dis- solution of carbonates (DICca) can be estimated by Eqs. (6 and 7): DICRI = DICtri – DICex + DICorg + DICca (6) DICRI*δ 13CRI = DICtri*δ 13Ctri – DICex*δ 13Cex + DICorg*δ 13CPOC + DICca*δ 13CCaCO3 (7) The contribution of rainwater to riverine DIC is considered to be minimal as it contains only a small amount of DIC (yanG et al., 1996). DICRI and DICtri were calculated from the con- centrations of alkalinity and water discharge, with the corresponding measured δ13C values for δ13CRI and δ 13Ctri. The average diffusive flux of CO2 from the river to the atmosphere, DICex, estimat- ed from Eq. (5), was taken into account. In Eqs. (5 and 6) the minus sign indicates outgassing of CO2, which is observed in autumn, but not in the spring season. The δ13Cex value was calculated ac- cording to the equation for equilibrium isotope fractionation between atmospheric CO2 and car- bonic acid in water (zhanG et al., 1995), where a δ13C value of -7.8 ‰ for atmospheric CO2 was used (levin et al., 1987). The isotopic composition of the contribution of equilibration between atmos- pheric CO2 and DIC (δ 13Cex) would then be +1.4 ‰ in the autumn and +1.8 ‰ in the spring sampling season, considering atmospheric CO2 as the ulti- mate source of CO2 in the River Sava in Slove- nia, River Idrijca and River Kamniška Bistrica drainage system. For δ13CPOC and δ 13CCaCO3 average values of -26.6 ‰ and +2.0 ‰ were used in the mass balance equations. Contributions of DIC from various bioge- ochemical processes were determined using steady state equations for different sampling seasons at the mouth of the River Kamniška Bis- trica; results indicate that: (1) 1.9-2.2 % of DIC came from exchange with atmospheric CO2, (2) 0-27.5 % of DIC came from degradation of or- ganic matter, (3) 25.4–41.5 % of DIC came from dissolution of carbonates and (4) 33.0–85.0 % of DIC came from tributaries (Kanduč et al., 2013). In both sampling seasons the most important biogeochemical process is weathering of car- bonates, while degradation of organic matter is more expressed in the spring sampling season. A less significant process in both sampling sea- sons is exchange with atmospheric CO2 and is not marked in the spring sampling season due to the pCO2 value (at location 28, Table 1, Fig.1), which is near equilibrium with atmospheric CO2 pres- sure. In River Sava mouth among biogeochemical processes dissolution of carbonates contributes the highest proportion in both sampling sea- sons, which moves δ13CDIC to more positive values. Mass balances for riverine inorganic carbon sug- gest that carbonate dissolution contributes up to 26 %, degradation of organic matter ~17 % and exchange with atmospheric CO2 up to 5 %. The concentration and stable isotope diffusion mod- els indicated that atmospheric exchange of CO2 predominates in streams draining impermeable shales and clays while in the carbonate-dom- inated watersheds dissolution of the Mesozoic carbonate predominates (Kanduč et al., 2007). The calculated contributions to the average DIC budget from DICtri:DICex:DICorg:DICca at the Riv- er Idrijca mouth were 61:-11:19:31 % in autumn 2006 and 35:0:26:39 % in spring 2007 (Kanduč et al., 2008). Conclusions The major solute composition of the River Kamniška Bistrica is dominated by HCO3 -, Ca2+ and Mg2+. Concentrations of HCO3 - ranged from 1.6 mM to 5.6 mM in main channel and from 2.6 to 5.5 mM in tributaries. The majority of River Kamniška Bistrica system was supersaturated or near equilibrium with respect to calcite/dolomite in all sampling seasons. According to the calcu- lated pCO2 values, the river is source of CO2 to the atmosphere during all sampling seasons, higher pCO2 is observed during summer season. Lower alkalinities and higher δ13CDIC values of -2.7 ‰ were observed in the upper carbonate part of the watershed, while higher alkalinities and more negative δ13CDIC values of -12.7 ‰ were observed in the central and lower part of the Kamniška Bistrica system. 24 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK The major chemical composition of River Sava water is HCO3 -, Ca2+ and Mg2+. Seasonal (spring 2004, late summer 2004 and winter 2005) con- centrations of HCO3 - range from 2.63 to 4.79 mM, while its tributaries have concentrations of HCO3 - ranging from 0.39 to 6.02 mM. The major- ity of the River Sava system is supersaturated or at equilibrium (in the upper part of the river flow) with respect to calcite in all sampling seasons. δ13CDIC values range from -12.7 to -6.3 ‰ and were observed in late summer. The observed differ- ences in pCO2, alkalinities and δ 13CDIC between the carbonate rock drainages versus mixed li- thology watersheds (carbonate and clastic rocks) at downstream locations are the consequence of the soil thickness since carbonate rocks are more resistant to mechanical weathering processes. The partial pressure is lower in the carbonate part of the watershed and higher at downstream locations. Lower alkalinities and higher δ13CDIC values are observed in the upper carbonate part of the watershed, while higher alkalinities and lower δ13CDIC values are observed in the central and lower part of the River Sava watershed. The biogeochemical processes affecting DIC and δ13CDIC values were quantified by concentra- tion and isotope mass calculations and it can be concluded that the most important biogeochem- ical processes at the River Sava mouth in order of significance in different sampling seasons are: (1) carbonate dissolution comprising 19.4 % in spring to 25.9 % in late summer, (2) degradation of organic matter comprising 10.8 % in winter to 16.7 % in late summer, while (3) atmospheric ex- change comprises 0.8 % in spring to 4.9 % in late summer. The River Sava in Slovenia has high dis- charge, low stream photosynthetic activity and represents a river system where among the bio- geochemical processes geological factors prevail (carbonate dissolution). Construction of hydro- electric power plants in the central and lower Sava flow in the next five years will affect the carbon cycle, e.g accelerated primary production, degradation of organic matter, degassing of CO2 from the river. This investigation will also help to evaluate the biogeochemical state of the river after dam constructions. The major solute composition of River Idrij- ca water is dominated by HCO3 -, Ca2+ and Mg2+. Seasonal alkalinity concentrations ranged from 3.88 to 4.66 mM, while its tributaries had concen- trations of HCO3 - ranging from 3.09 to 5.10 mM. The majority of the River Idrijca system was su- persaturated or near equilibrium with respect to calcite. The biogeochemical processes affect- ing DIC concentrations and δ13CDIC (in the range from -10.8 to -6.6 ‰) calculated by mass balance equations showed that the most important bio- geochemical processes at the River Idrijca mouth are: carbonate mineral dissolution, degradation of organic matter and atmospheric exchange. The River Idrijca is a river with torrential character, has a high specific discharge and therefore high weathering intensity. In all three investigated rivers carbonate dis- solution and degradation of organic matter are the most important biogeochemical processes in river system, while exchange with atmosphere could be negligible according to mass balance equations. Acknowledgements The authors are thankful to Research Agency of Republic of Slovenia, program research groups P1- 0143 and P1-0195. The authors are also thankful to previous research projects funded by Research Agency of Republic of Slovenia and ongoing research project L2–6778 (2014–2017). Finally, our sincere thanks go to prof. dr. Jožef Pezdič for introducing us to stable iso- topic geochemistry and hydrogeochemistry and for his guidance in the research and pedagogical work. References aMiotte suchet, P. & ProBst, j.l. 1993: Modelling of atmospheric CO2 consumption by che- mical weathering of rocks: Application to the Garonne, Congo and Amazon ba- sins. Chem. Geol., 107/3-4: 205-210, doi:10.1016/0009-2541(93)90174-H. anDerson, s.P., Drever, j.i., Frost, c.D. & holDen, P. 2000: Chemical weathering in the foreland of a retreating glacier. Geochim. Cosmochim. Acta, 64/7: 1173-1189, doi:10.1016/ S0016-7037(99)00358-0. ateKwana, e.a. & KrishnaMurthy, r.v. 1998: Seasonal variations of dissolved inor- ganic carbon and d13C of surface waters: Application of a modified gas evaluation technique. Hydrology Journal, 205/3-4: 265- 278, doi:10.1016/s0022-1694(98)00080-8. Barth, j.a.c., cronin, a.a, DunloP, j. & Kalin, r.M. 2003: Influence of carbonates on the ri- verine carbon cycle in an anthropgenically 25Biogeochemistry of selected Slovenian rivers (Kamniška Bistrica, Idrijca and Sava in Slovenia): insights from river water... dominated catchment basin: evidence from major elements and stable carbon isoto- pes in the Lagan River (N. Ireland). Chem. Geol., 200/3-4: 203-216, doi:10.1016/ S0009-2541(03)00193-1. Berner, e.K. & Berner, r.a. 1996: Global envi- ronment, water, air, and geochemical cycles. Prentice Hall, Upper Saddle River. BroecKer, w.s. 1974: Chemical oceanography. Harcourt Brace Jovanovich, New York. Buser, s. 1987: Geological map of Slovenia. In: voGler D. (ed.): Encyclopedia of Slovenia No. 8, Mladinska knjiga, Ljubljana (in Slovene): 4-416. clarK, i. & Fritz, P. 1997. Environmental Isotopes in Hydrogeology. New York: Lewis Publishers. cole, j.j., Prairie, y.t., caraco, n.F., McDowell, w.h., tranviK, l.j. strieGl, r.G., Duarte, c.M. Kortelainen, P., DowninG, j.a., MiDDelBurG, j.j. & MelacK, j. 2007. Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget. Ecosystems, 10: 171-184, doi:10.1007/s10021-006-9013-8. čar, J. 2010: Explanatory book to the map: geo- logical structure of the Idrija - Cerkno hil- ls. Geological Survey of Slovenia, Ljubljana: 125 p. Deines, P. 1980: The isotopic composition of re- duced organic carbon. In: Fritz P. & Fontes J.C. (eds.): Hanbook of Environmental Isotopic Geochemistry, 1: 329-406, Elsevier, Amsterdam. Dever, l., DuranD, r., Fontes, j. c.H. & vaicher, P. 1983: Etude pédogénétique et isotopique des néoformations de calcite dans un sol sur craie. Caractéristiques et origins. Geochimica Cosmochimica Acta, 47: 2079-2090. FairchilD, i.j., Killawee, j.a., huBBarD, B. & DreyBoDt, w. 1999: Interactions of calca- reous suspended sediment with glacial meltwater: a field test of dissolution behavi- our. Chem. Geol., 155: 243-263, doi:10.1016/ s0009-2541(98)00170-3. Fratar, P. 2005: River Flow Regimes of Slovene Rivers and their fluctuations = Pretočni reži- mi slovenskih rek in njihova spremenljivost. Ujma, 19: 145-153. GaillarDet, j., DuPré, B., louvat, P. & allèGre, c.j. 1999: Global silicate weathering and CO2 consumption rates deduced from the chemis- try of large rivers. Chem. Geol., 159: 3-30. Germ, m., GaberščeK a. & urbanc-berčič, O. 1999: Aquatic macrophytes in the River Sava, Kolpa and Krka. Ichtyos, 16: 23-34. GiBBs, r.j. 1972. Water chemistry of the Amazon River. Geochim. Cosmochim. Acta, 36: 1061-1066. GiesKes, j.M. 1974. The alkalinity-total carbon dioxide system in seawater. In: GolDBerG, E.D. (ed.): Marine chemistry of the sea, 5: 123-151. hrvatin, M. 1998. Discharge regimes in Slovenia. Geografski zbornik, XXXVIII: 60-87. huh, y., tsoi M.y., zaitsev a. & eDMonD, j.M. 1998: The fluvial geochemistry of the rivers of Eastern Siberia: I. Tributaries of the Lena River draining the sedimentary platform of the Siberian Craton. Geochim. Cosmochim. Acta, 62:1657–1676. jacoBson, a.D., BluM, j.D. & walter, l.M. 2003: Reconciling the elemental and Sr isotope composition of Himalayan weathering fluxes: insights from the carbonate geochemistry of streams. Geochim. Cosmochim. Acta, 66/19: 3417-3429, http://dx.doi.org/10.1016/ S0016-7037(02)00951-1 jähne, B., heinz, G. & Dietrich, w. 1987: Measurements of the Diffusion Coefficients of sparingly soluble gases in water. J Geophys Res Oceans, 92: 10767-10776. Kanduč, T. 2006. Hydrogeochemical characte- ristics and carbon cycling in the Sava River watershed in Slovenia. PhD Dissertation. University of Ljubljana, Ljubljana: 141 p. Kanduč, T., SzrameK, K., OGrinc, n. & WalTer, l.M. 2007: Origin and cycling of riverine inorganic carbon in the Sava River watershed (Slovenia) inferred from major solutes and stable carbon isotopes. Biogeochemistry, 86: 137-154, doi:10.1007/s10533-007-9149-4 Kanduč, T., KOcman, d. & OGrinc, n. 2008: Hydrogeochemical and stable isotope chara- cteristics of the river Idrijca (Slovenia), the boundary watershed between the Adriatic and Black seas. Aquatic geochemistry, 14: 239-262, doi:10.1007/s10498-008-9035-2. Kanduč T., šTurm, mb. & mcinTOSh, J. 2013. Chemical dynamics and evaluation of bi- ogeochemical processes in alpine River Kamniška Bistrica, North Slovenia. Aquatic Geochemistry, 19:323-346, doi:10.1007/ s10498-013-9197-4. Kanduč, T., SamardŽiJa, z., mOri, n., Jerebic, a., levačić, J., Kračun, m., rObinSOn, J.a., ŽiGOn, S., blaŽeKa, Ž., KOcman, d. 2016: Hydrogeochemical and isotopic characteri- zation of Pesnica River, Slovenia. Geologija, 59/2: 179-192, doi:10.5474/geologija.2016.010. levin, i., KroMer, B., waGenBacK D. & Münnich, K.o. 1987: Carbon isotope measurements 26 Tjaša KANDUČ, David KOCMAN & Timotej VERBOVŠEK of atmospheric CO2 at a coastal station in Antartctica. Tellus, 39B: 89-95. liu, z. & zhao, j. 2000: Contribution of carbonate rock weathering to the atmospheric CO2 sink. Environmental Geology, 39:1053–1058, doi: 10.1007/s002549900072. mechOra, š. & Kanduč, T. 2016: Environmental assessment of freshwater ecosystems of the River Sava watershed and Cerkniško Lake, Slovenia, using the bioindicator species Fontinalis antipyretica: insights from sta- ble isotopes and selected elements. Isotopes Environ. Isotopes in Environmental and Health Studies, 52/3:239-57, doi:10.1080/10256 016.2016.1114933 MiyajiMa, t., yaMaDa, y. & hanBa, y.t. 1995: Determining the stable isotope ration of to- tal dissolved inorganic carbon in lake water by GC/C/IRMS. Limnology Oceanography, 40:994-1000. mlaKar, i. & čar, J. 2009: Geological map of the Idrija - Cerkno hills between Stopnik and Rovte 1:25.000. Geological Survey of Slovenia. néGrel, P. & lachassaGne, P. 2000: Geochemistry of the Maroni River (French Guiana) during the low water stage: implications for water- -rock interactions and groundwater chara- cteristics. Journal of Hydrology, 237:212–233, doi: 10.1016/S0022-1694(00)00308-5. ParKhurst, D.l. & aPPelo, c.a.j. 1999: User’s gu- ide to PHREEQC (version 2)-a computer pro- gram for speciation, batch –reaction, ne-di- mensional transport, and inverse geochemical calculations. Water-Resources Investigations Report, 99-4259. Pezdič, J. 1999: Izotopi in geokemijski pro- cesi (In Slovene). Univerza v Ljubljani, Naravoslovnotehniška fakulteta, Oddelek za geologijo. Univerzitetni učbenik, Ljubljana: 269 p. radinJa, d., GrbOvić, J., POvŽ, m., zuPan, m. & sKoBerne, P. 1987: Kamniška Bistrica. In: javorniK, M. (ed.): Encyclopedia Slovenia 4. Mladinska knjiga, Ljubljana, pp 382 (in Slovene). rayMonD, P.a., zaPPa, c.j., ButMan, D., Bott, t.l., Potter, j., MulhollanD, P., lauersen, a.e., McDowell, w.h. & newBolD, D. 2012: Scaling the gas transfer velocity and hydraulic geo- metry in streams and small rivers. Limnology Oceanography Fluids Environment, 2: 41-53, doi:10.1215/21573689-1597669. reeDer, s.w., hitchon, B. & levinson, a.a. 1972: Hydrogeochemistry of the surface waters of the Mackenzie River drainage basin, Canada: 1. Factors controlling inorganic composition. Geochim. Cosmochim. Acta, 36:181–192. roy, s., GaillarDet, j. & alleGre, c.j. 1999: Geochemistry of dissolved and suspended lo- ads of the Seine River, France: anthropogenic impact, carbonate and silicate weathering. Geochimica Cosmochimica Acta, 63: 1277- 1292, doi:10.1016/S0016-7037(99)00099-X. sarMiento, j.l. & sunDquist, e.t. 1992: Revised budget for the oceanic uptake of anthropo- genic carbon –dioxide. Nature, 356/6370: 589-593. schulte, P., van GelDern, r., FreitaG, h., KariM, a., néGrel, P., Petelet-GirauD, e., ProBst, a., telMer, K., veizer, j. & Barth, j.a.c. 2011: Applications of stable water and car- bon isotopes in watershed research: weathe- ring, carbon cycling, and water balances. Earth Science Review, 109: 20-31, doi:10.1016/j. earscirev.2011.07.003. sPötl, c. 2005: A robust and fast method of sampling and analysis of δ13C of dissolved inorganic carbon in ground waters. Isotopes Environ Health Stud, 41: 217-221. szraMeK, K., Mcintosh, j.c., williaMs, e.l., Kanduč, T., OGrinc, n. & WalTer, l.m. 2007: Relative weathering intensity of calcite versus dolomite in carbonate-bearing temperatu- re zone watersheds: carbonate geochemistry and fluxes from catchments within the St. Lawrence and Danube river basin. Geochem Geophys, 8: 1-26, doi:10.1029/2006gc001337. zhanG, J., huanG, W.W., létole, R. & jusseranD, C. 1995: Major element chemistry of the Huange (Yellow River), China-weathering processes and chemical fluxes. J Hydrol., 168/1–4: 173- 203, doi:10.1016/0022-1694(94)02635-O. ŽlebniK, l. 1971. Pleistocen Kranjskega, Sorškega in Ljubljanskega polja (In Slovene). Geologija, 14: 5–51. yanG, c., telMer, K. & veizer, j. 1996: Chemical dynamics of the “St. Lawrance” riverine system: δDH2O, δ 18OH2O, δ 13CDIC, δ 34Ssulfate and dis- solved 87Sr/86Sr. Geochim. Cosmochim. Acta, 60: 851-866, doi:10.1016/0016-7037(95)00445-9. Internet resources: internet 1: http://srtm.csi.cgiar.org/ (18.10.2016) internet 2: http://www.arso.gov.si/en/ (18.10.2016) internet 3: http://www.bgr.de/karten/igme5000/ igme.htm (18.10.2016)