CONTRIBUTION Of SIMPLE Hy DROGEOLOGICAL INDICATING METHODS IN CONTAMINATION-IMPACTED ENVIRONMENTS UPORABA METODE PREPROSTIH HIDROGEOLOŠKIH INDIKATORJEV V ONESNAŽENIH OKOLJIH Slavomír MIKITA 1 & Vladimír VyBÍRAL 2 Izvleček UDK 556.3:504 Slavomír Mikita & Vladimír Vybíral: Uporaba metode pre- prostih hidrogeoloških indikatorjev v onesnaženih okoljih V okviru projekta slovaškega ministrstva za okolje, smo v obdobju štirih let izvajali raziskave vpliva različnih virov onesnaževal na vodne vire. Izbrali smo več področij z različno geološko sestavo v zahodnih Karpatih . Rezultati so potrdili, da je vpliv virov onesnaženj spremenljiv v prostoru in času, zato učinkovita zaščita vodnih virov zahteva veliko prostor- sko in časovno gostoto informacij in raziskav. Da bi pri tem zmanjšali uporabo dragih in zapletenih metod, smo uporabili metodo hidrogeoloških indikatorjev (HIM), ki temelji na os- novi povezave med koncentracijo onesnaževal in osnovnimi fizikalnimi parametri vode, kot sta temperatura in specifična električna prevodnost. Merjenje teh parametrov omogoča posredno zaznavanje onesnaževal. č e njihovo zvezno opa- zovanje združimo s točkovnimi analizami vode in ostalimi te- renskimi metodami, lahko vzpostavimo učinkovito in cenovno ugodno kartiranje širjenja onesnaževal. Ključne besede: onesnaževanje, okolje, specifična električna prevodnost, temperatura vode, informacije. 1 Department of hydrogeology, f aculty of Natural Sciences, Comenius University Bratislava, Mlynská dolina, Slovak Republic; e-mail: mikita@fns.uniba.sk 2 Nobelova 34, 831 02 Bratislava, Slovak Republic. Received/Prejeto: 18.09.2006 COBISS: 1.01 ACTA CARSOLOGICA 36/2, 255-260, POSTOJNA 2007 Abstract UDC 556.3:504 Slavomír Mikita & Vladimír Vybíral: Contribution of simple hydrogeological indicating methods in contamination-im- pacted environments Under the project of Ministry of the environment of Slovak Re- public a “real” impact of various contaminant sources on water was monitored and assessed during the period of 4 years. Vari- ous geological environments of The Western Carpathians were chosen as studying areas. The results of the project confirm that the influence of the contamination source is variable in space and time. An amount of objective and efficient information is necessary to fulfill the requirements for the water treatment. The possibility how to minimize the amount of expensive and intricate methods used by investigation was to connect them with hydrogeological indicating methods (HIM). The correlat- ed relations distinguished between contaminant and physical characteristics of water allow using the obtained local informa- tion in larger area and repeating them in higher frequency. The economical benefit is relative to increasing demands on space and time. The base was built on the water conductivity and wa- ter temperature measurements set in field. The measured values which were processed basically allow obtaining indirect infor- mation about the contamination spreading. By correlation the values with water analyses for a monitoring site from specific studied locality and by added other information from field methods the results can be amplified. It is possible to substitute the intricate and expensive contaminant spreading mapping methods by HIM and monitor the dynamic changes of contam- ination influences in space and time with denser data net. Key words: contamination, environment, conductivity, water temperature, information. ACTA CARSOLOGICA 36/2 – 2007 256 The requirements for water quality protection have a very high priority. To protect the water contami- nation must be clearly detected, considered and pre- dicted. Specific localities were studied with aim to improve knowledge about transport of contaminants and behaving the contamination-impacted environ- ments. Contamination-impacted environments in this case can be characterized as localities where the source of contamination has an influence on their vicinity with significant changes in water quality. The most common kind of contamination-impacted environments in Slovak Republic present an “old” landfills often built without legislative control and sufficient information about the waste storage. Under the project of Ministry of the En- vironment of Slovak Republic a “real” impact of 15-se- lected landfills on specific geological setting of The West - ern Carpathians was studied during the period of 4 years (Vybíral et al., 2005). In “old” landfills where all types of materials have been deposited and are possible source of various kinds of organic and inorganic pollutants, originated in leach- ing process. Landfill leachate is generated by excess rainwater percolating through the waste layers. Com- bined physical, chemical and microbial processes in the waste transfer pollutants from the waste materials to the percolating water. f ocusing on the common type of landfill receiving a mixture of municipal, commer- cial and mixed industrial waste, but excluding signifi- cant amounts of concentrated specific chemical waste, landfill leachate may be characterized as water based solution of four groups of pollutants (Christensen et al., 2001). • Dissolved organic matter, expressed as Chemi- cal Oxygen Demand (COD) or Total Organic C (TOC), including CH 4 , volatile fatty acids and more refractory compounds for example, fulvic-like and humic-like com- pounds, • Inorganic macrocomponents: Ca, Mg, Na, K, NH 4 + , f e, Mn, Cl, SO 4 2+ , HCO 3 - , • Heavy metals: Cd, Cr, Cu, Pb, Ni and Zn, • x enobiotic organic compounds (x OCs) originat- ed from household or industrial chemicals are present in relatively low concentrations in the leachate (usually less than 1 mg/l of individual compounds). These com- pounds include among others a variety of aromatic hy- drocarbons, phenols and chlorinated aliphatics. Other compounds may be found in leachate from landfills: e.g. B, As, Se, Ba, Li, Hg and Co. But in general these compounds are found in very low concentrations and are only of secondary importance. Leachate composition varies significantly among landfills depending on waste composition, waste age and landfilling technology. Where leachate enters the groundwater, significant changes in water quality are observed and complicated biogeochemical patterns develop in the leachate pollu- tion plume. The fate and behaving of contaminants will depend on many factors, like individual characters of contami- nants or hydrogeological conditions of given environ- ment. In this system various chemical, biochemical and physical processes are running and the chemical equilib- rium is changing. One of the main characteristic mani- festations related to the contaminants spreading from the landfill is the presence a sequence of redox zones in the groundwater. They originated from leachate reduc- ing processes with methanogenic conditions close to the landfill and oxidized conditions in the outskirts of the plume. The aim of the project was also to present the optimal methods for investigation and monitoring of the contaminant spreading in specific environments. f rom the view of contamination spreading mapping and monitoring is necessary to get information about (Šráček et al., 2000): • nature of the contaminants, source and way of contamination, • area and rate of contamination, including the background values that are valid for specific localities, • migration parameters, direction and velocity of contamination spreading, characteristics of the contami- nated environment (porosity, granularity), hydrogeologi- cal parameters, groundwater regime, • history of contamination and its development in time, trends of contamination differences, • evaluation of the objects endangered by contami- nation spreading, the level of their endangerment, the necessity and propose of remediation methods. To get answers to most of these questions is only possible by studying the interaction zone – the zone of real influence of the source of contamination on their vi- cinity (f ig. 1). Zone of interaction is dynamic in space and time; it depends on the water regime, the characteristics of landfill material, the maturity of stored material and en- gineering geological and hydrogeological conditions. f or the approach to solve the project it was useful to distinguish the landfills due their characteristic zone of interactions with aquatic environment (Putiška et al., 2005). f our main models of landfills can by presented: a) model with zero thickness of superincumbent bed (or INTRODUCTION SLAVOMÍR MIKITA & VLADIMÍR Vy BÍRAL ACTA CARSOLOGICA 36/2 – 2007 257 landfills of “valley type”), b) model with the impermeable subsoil in 10-14 m depth, c) model with impermeable subsoil in „endless” depth, d) model of landfill encapsu- lated by slurry trench walls. f or the landfill locallizated on karst the model with impermeable subsoil in „endless” depth can be applied. In this case landfill is deposited directly on the perme- able environment; vertical movement of groundwater is unlimited. Landfill material is deposited into natural or artificial depressions, as well as, onto the natural surface. Contamination is carried out from the landfill by infil- trating rainwater. The groundwater table is usually too deep for effective observation by boreholes and another methods are focusing on natural objects in the landfill vicinity (springs, rivers) therefore more suitable. Relative big differences of water quality in seasonal variations can be observed. Only one locality (DNV – Srdce) was situ- ated on karst but obtained knowledge correspond well with the experiences from other countries, f. e. Slovenia (Petrič & Šebela, 2005), Sardinia (personal experience). Hy DROGEOLOGICAL INDICATING METHODS (HIM) f or the contamination spreading observation informa- tion about the water physical-chemical features around the contamination-impacted area are very important. The chemical analyses of water yield accurate informa- tion but they are not able to notice effectively frequent changes which depend on the influence of external (pre- cipitation, air temperature) and internal (character and maturing of contamination, geology, hydrogeology) fac- tors. The requirements on monitoring of the groundwa- ter quality around the landfills has long-term duration (several tens years) and therefore demands on finances and expertise are necessary be taken into account. There is a need for connecting them with simple but effective and operative mapping methods and subse- quently getting more information about the contaminant spreading changes. Presence and form of some typical chemical mac- rocomponents from landfill leaching in water is chang- ing physical water parameters significantly and those are possible to be measured. f or mapping activities concerning contamination spreading the field measurement of physical parameters proved very well. Two parameters were measured – water conductivity and water temperature, both belong to Hy- drogeological Indicating Methods (HIM). The water conductivity (termed also as electro- lytic conductivity - κ, given in mS.m -1 ) is an important parameter in water geochemistry. It is a function of ion concentration in solution, their charge number, mobility and temperature. In waters, the contents of which is con- stituted mostly by inorganic compounds (drink waters, most of the surface- and some of waste water), the water conductivity can be used as the approximate rate of the mineral electrolytes concentration. In the wastewater that contains salts of organic acid and alkali the water con- ductivity is an approximate rate of the mineral content and organic electrolytes concentration (Pitter, 1999). The water conductivity was measured: • as an additional parameter with the targeted wa- ter sampling, at which only samples from the selected sampling places were taken, while in other places the orientation data about the range of contamination were obtained only indirectly, • as a main parameter, when the water conductivity was the only measured parameter, • continuously along the whole length of the bore- hole; observed were the changes in water conductivity in a water column. Typical average values of water conductivity from measuring on specific localities ranged from 72 to 1043 mS.m -1 (f ig. 2). The differences between values were mostly depen- dent on character of contamination and its maturity, also on geological, hydrogeological and climate conditions. In some of studied localities there was strong influence from seasonality related to the amount of water in the environment (f ig. 3). As a response there were frequently changing val- ues during the year period. Stability of a frequency was also dependent on the depth of water circulation in the given environment. f rom the view of a longer time pe- riod (several years) the values had a decreasing, or an Fig. 1: model of interaction. Fig. 2: The water conductivity value differences in the studied localities. CONTRIBUTION Of SIMPLE Hy DROGEOLOGICAL INDICATING METHODS IN CONTAMINATION-IMPACTED ENVIRONMENTS ACTA CARSOLOGICA 36/2 – 2007 258 increasing trend, that was connected with the maturity processes in the deposited waste (f ig. 4). Measuring the water temperature (thermometry) in the field is based on a values contrast. f or the purpos- es of the contamination spreading mapping is depending mostly on the maturity processes in source of contamina- tion where the organic matter is present. The water tem- perature could reach 40 – 60 °C. In this way is possible to use it for mapping of transport ways of contamination descending from source. Water temperature was measured: • directly in the field with each water sampling, • for a special purpose, while doing an assessment of the origin of springs and ground water inflows into the streams. PROCESSING AND EVALUATION Of MEASURED PHy SICAL PARAMETERS Information obtained from water conductivity and wa- ter temperature measurements was processed basically and also was related to the results of other field methods to be amplified. The basic processing came from screening all wa- ters accessible in the studied area and it does recur in different time in the same positions. In this way it is possible to: • assess the relative differences of water features in a studied area, • map the source of contamination, and distinguish if the contamination is simple, long term, pointed, flat- ted, etc., • map the mass transport paths of contamination, • estimate the trends of the measured data changes development (f ig. 4), • detect the changes of the water vertical zonality continuance in the borehole (f ig. 5). The information obtained according to described way has only relative character and their contribution is mainly by first investigation of the contaminant-im- pacted environment. The information with higher sig- nificance about the interactions in system contamina- tion – water environment can be reached by the ampli- fied processing. The amplified processing is based on distinguishing the correlation relations between the electric conductivity and a typical chemical param- eter – the macrocontaminant – which is characteristic for the studied area and which we are considering to represent the physical attributes in the given environ- ment. f or that purposes the inert chloride affirm very well (f ig. 6). f inding the optimal correlation relation is condi- tioned with character of contamination, geological and hydrogeological conditions of given locality. It is there- fore necessary to apply the relation on specific monitor- ing place. The correlation allows substituting the specific chemical component with conductivity measurement and so extending the qualitative point information into space and repeating them in higher frequency. The new information with higher weight for the contamination spreading predictions can be obtained. According to the settings of the impacted environment the achieved infor- mation is a good assumption for various purposes: • to monitor dilution with an increasing distance from the contaminant source (f ig. 7), • to assess the climate and hydrological influences on contamination (f ig. 3), Fig. 5: manifestation of the conductivity measurements in one borehole from given environment. Fig. 3: Cooperation of the conductivity variation in concerning to water temperature and water quantity in one monitoring place of the given locality. Fig. 4: Water conductivity development during a 6 years period in one of selected monitoring place from given locality. SLAVOMÍR MIKITA & VLADIMÍR Vy BÍRAL ACTA CARSOLOGICA 36/2 – 2007 259 Fig. 6: Dependency between the chloride ions and conductivity from selected monitoring places in one of the studied locality. • to describe the distribution of related components in space and time by developing 3D models (f ig. 8), • to monitor the intensity and the rate of contami- nation (f ig 4,7,8), • to predict the trends of contamination maturing processes (f ig. 3,4,5). On the f ig. 8 are pointed the values that were de- tected in 6 boreholes from their water table to the bot- tom. The boreholes are localized in a front part of given landfill. The main groundwater flow is transverse direc - tion on the boreholes. Fig. 7: Expression of a dependency between the parameters of chloride ions, conductivity and distance from contamination source, measured from the monitoring places of given locality. The results after measuring and processing are possible to interpret also in a form of different outputs (Krčmář, 2002). Application of HIM was utilized by dealing with the interaction between contamination-impacted envi- ronments and their surroundings with different extent of contribution (Mikita et al., 2005). It is conditioned mainly by hydrogeological conditions of studied envi- ronment and the monitoring instruments access to the water. Relatively the best utilization was obtained from a landfill of “valley type” placed to the valley with imper- meable or almost impermeable subsoil where the leak- age from landfill is distributed to the surrounding area by outflow located in the front parts of landfills (Mikita et al., 2005). To observing the landfill influence on karst aquatic environment the HIMs can be mainly used for: • discovering the hidden inflows of contaminants to the rivers, springs or wells present in the vicinity of the landfill, • continuous monitoring for monitoring points in karst aquifers with caution for unfavorable situation, in- direct monitoring of the seasonally differences in water quality. Fig. 8: Water zonality measuring in selected boreholes from one of studied locality. CONCLUSIONS Evaluation of a geological environment and contami- nants interference is a complicated problem. The con- tamination spreading investigation and monitoring re- quires large amounts of data and detailed information about the surface, groundwater regime, water and soils physical and chemical characteristics. The danger from the given contamination-imapcted environment is radi- cally changing in time and dimensional space. The 15 contamination-impacted areas situated in various geo- logical units of Western Carpathians were analyzed in detail during the four years investigation. Knowledge had shown that the intricate and ex- pensive methods of mapping of contamination spread- ing and consequent monitoring can be substituted with simple but effective and operative hydrogeological indi- cating methods (HIM). Two physical parameters - water conductivity and water temperature were measured di- rectly on monitoring sites. Values obtained from water CONTRIBUTION Of SIMPLE Hy DROGEOLOGICAL INDICATING METHODS IN CONTAMINATION-IMPACTED ENVIRONMENTS ACTA CARSOLOGICA 36/2 – 2007 260 conductivity and water temperature measurements were basically processed and were also related to the results of other field methods to be amplified. Hydrogeological indicating methods in general allow: • continual monitoring of excessively values changing, • detection of potentially hidden transfer of con- tamination into the surface water, • characterization of the depth of groundwater circulation in studied area, • repetition of contamination spreading measur- ing in dimensional space and in time with relatively dense data net, • monitoring extent and development of the con- tamination spreading according the changing condition. The main advantage of HIM is their simplicity and possibility of the directly field measuring which allows sufficient and continual recording of values about the time and dimensional space variations in the contamina- tion development. The correlated relations between contaminant and water conductivity allow to extend local information from water analyses in larger area and repeating them in higher frequency. An amount of objective and optimal amount of sta- tistical information for the water protection management requirements can be obtained from HIM. It improves consideration possibilities for prompt answering how the contamination is dangerous, if is necessary to deal with the contamination and how is possible to handle with it in time. Application of HIM can by utilized with different extent of contribution what is conditioned mainly by hy- drogeological conditions of studied environment. f or the landfills localized on karst the model with impermeable subsoil in “endless“ depth can be applied. The investiga- tion by HIM is here focus mainly on the springs and riv- ers present in the landfill vicinity. The economical benefit from using HIM is rising also with the increase requirements on the longtime con- tamination spreading monitoring and the extent of stud- ied area. 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