Groundwater quality and hydrogeochemical properties of Torbalı Region, Izmir, Turkey

The large demand for drinking, irrigation and industrial water in the region of Torbali (Izmir, Turkey) is supplied from groundwater sources. Almost every factory and farm has private wells that are drilled without permission. These cause the depletion of groundwater and limiting the usage of groundwater. This study investigates spatial and temporal change in groundwater quality, relationships between quality parameters, and sources of contamination in Torbali region. For this purpose, samples were collected from 10 different sampling points chosen according to their geological and hydrogeological properties and location relative to factories, between October 2001 and July 2002. Various physical (pH, temperature, EC), chemical (calcium, magnesium, potassium, sodium, chloride, alkalinity, copper, chromium, cadmium, lead, zinc) and organic (nitrate, nitrite, ammonia, COD and cyanide) parameters were monitored. It was observed that the groundwater has bicarbonate alkalinity. Agricultural contamination was determined in the region, especially during the summer. Nitrite and ammonia concentrations were found to be above drinking water standard. Organic matter contamination was also investigated in the study area. COD concentrations were higher than the permissible limits during the summer months of the monitoring period.     

Assessment of Groundwater Quality in a Structurally Deformed Granitic Terrain in Hyderabad, India

Geochemical study of groundwater from a structurally deformed granitic terrain near Hyderabad (India) was carried out to understand and evaluate the hydrogeochemical processes and quality of groundwater. Several trace elements (Fe, Mn, Be, Al, V, Cr, Co, Ni, Cu, Zn, As, Sr, Mo, Cd, Sb, Ba, Pb, U) along with major ions and minor elements were precisely estimated in shallow and drilled wells to know the suitability of water for drinking and irrigation purposes. Analytical data shows that pH and major ion chemistry in dug wells and bore wells do not vary significantly, while some trace elements (Fe, Mn, Al, Be, Co, Pb, U and Zn) vary in dug wells and bore wells, which can be attributed to differential mineral weathering and dissolution/precipitation reactions along fractures/joints. Although the water is not potable, it was found to be suitable for irrigation with little danger in the development of harmful level of exchangeable sodium. It is inferred that the chemical composition of the groundwater in this region is likely to have its origin from silicate weathering reactions and dissolution/precipitation processes supported by rainfall and groundwater flow.     

Comparison of Nitrate Levels in Raw Water and Finished Water from Historical Monitoring Data on Iowa Municipal Drinking Water Supplies

Nitrate contamination of water sources is a concern where large amounts of nitrogen fertilizers are regularly applied to soils. Ingested nitrate from dietary sources and drinking water can be converted to nitrite and ultimately to N-nitroso compounds, many of which are known carcinogens. Epidemiologic studies of drinking water nitrate and cancer report mixed findings; a criticism is the use of nitrate concentrations from retrospective drinking water data to assign exposure levels. Residential point-of-use nitrate data are scarce; gaps in historical data for municipal supply finished water hamper exposure classification efforts. We used generalized linear regression models to estimate and compare historical raw water and finished water nitrate levels (1960s--1990s) in single source Iowa municipal supplies to determine whether raw water monitoring data could supplement finished water data to improve exposure assessment. Comparison of raw water and finished water samples (same sampling date) showed a significant difference in nitrate levels in municipalities using rivers; municipalities using other surface water or alluvial groundwater had no difference in nitrate levels. A regional aggregation of alluvial groundwater municipalities was constructed based on results from a previous study showing regional differences in nitrate contamination of private wells; results from this analysis were mixed, dependent upon region and decade. These analyses demonstrate using historical raw water nitrate monitoring data to supplement finished water data for exposure assessment is appropriate for individual Iowa municipal supplies using alluvial groundwater, lakes or reservoirs. Using alluvial raw water data on a regional basis is dependent on region and decade.     

Evaluation of groundwater quality and its suitability for drinking and agricultural use in Thanjavur city, Tamil Nadu, India

As groundwater is a vital source of water for domestic and agricultural activities in Thanjavur city due to lack of surface water resources, groundwater quality and its suitability for drinking and agricultural usage were evaluated. In this study, 102 groundwater samples were collected from dug wells and bore wells during March 2008 and analyzed for pH, electrical conductivity, temperature, major ions, and nitrate. Results suggest that, in 90% of groundwater samples, sodium and chloride are predominant cation and anion, respectively, and NaCl and CaMgCl are major water types in the study area. The groundwater quality in the study site is impaired by surface contamination sources, mineral dissolution, ion exchange, and evaporation. Nitrate, chloride, and sulfate concentrations strongly express the impact of surface contamination sources such as agricultural and domestic activities, on groundwater quality, and 13% of samples have elevated nitrate content (>45 mg/l as NO₃). PHREEQC code and Gibbs plots were employed to evaluate the contribution of mineral dissolution and suggest that mineral dissolution, especially carbonate minerals, regulates water chemistry. Groundwater suitability for drinking usage was evaluated by the World Health Organization and Indian standards and suggests that 34% of samples are not suitable for drinking. Integrated groundwater suitability map for drinking purposes was created using drinking water standards based on a concept that if the groundwater sample exceeds any one of the standards, it is not suitable for drinking. This map illustrates that wells in zones 1, 2, 3, and 4 are not fit for drinking purpose. Likewise, irrigational suitability of groundwater in the study region was evaluated, and results suggest that 20% samples are not fit for irrigation. Groundwater suitability map for irrigation was also produced based on salinity and sodium hazards and denotes that wells mostly situated in zones 2 and 3 are not suitable for irrigation. Both integrated suitability maps for drinking and irrigation usage provide overall scenario about the groundwater quality in the study area. Finally, the study concluded that groundwater quality is impaired by man-made activities, and proper management plan is necessary to protect valuable groundwater resources in Thanjavur city.     

The effect of changes in land use on nitrate concentration in water supply wells in southern Chester County, Pennsylvania

An analysis of private potable water well data was conducted for seven single family residential developments in southern Chester County, Pennsylvania. Background data were available for 165 wells within the communities when the wells were first drilled in the 1980s and early 1990s. Sampling of 75 wells within these same communities was performed in 2006 to determine whether conversion of the land to residential housing along with the use of conventional on-lot septic systems had resulted in elevated concentration of nitrate-nitrogen in the drinking water aquifer. The data indicate that prior land use influenced the occurrence of nitrate-nitrogen in the drinking water aquifer. The median nitrate-nitrogen concentration for the 165 wells in the background dataset was 2.9 mg/L. One hundred-seven of those wells were drilled on land previously used for active agricultural purposes. The median nitrate concentration in these wells was 3.8 mg/L. Of 48 wells drilled on forested land, the median nitrate concentration was 1.1 mg/L, approximately 3.5 times lower than those drilled on active agricultural land. The median nitrate concentration in the 2006 sampling dataset was 3.6 mg/L, an increase of 0.7 mg/L. The data indicate that conversion of the land has not resulted in contamination of the drinking water aquifer with respect to nitrate-nitrogen. Likewise, the data suggest that the conversion has not resulted in significant improvements to overall water quality.     

Does irrigation with reclaimed water significantly pollute shallow aquifer with nitrate and salinity? An assay in a perurban area in North Tunisia

In Tunisia, reclaimed water is increasingly used for irrigation in order to mitigate water shortage. However, few studies have addressed the effect of such practice on the environment. Thus, we attempted in this paper to assess the impact of irrigation with reclaimed water on the nitrate content and salinity in the Nabeul shallow aquifer on the basis of satellite images and data from 53 sampled wells. Ordinary and indicator kriging were used to map the spatial variability of these groundwater chemical parameters and to locate the areas where water is suitable for drinking and irrigation. The results of this study have shown that reclaimed water is not an influential factor on groundwater contamination by nitrate and salinity. Cropping density is the main factor contributing to nitrate groundwater pollution, whereas salinity pollution is affected by a conjunction of factors such as seawater interaction and lithology. The predictive maps show that nitrate content in the groundwater ranges from 9.2 to 206 mg/L while the electric conductivity ranges from 2.2 to 8.5 dS/m. The high-nitrate concentration areas underlie sites with high annual crop density, whereas salinity decreases gradually moving away from the coastline. The probability maps reveal that almost the entire study area is unsuitable for drinking with regard to nitrate and salinity levels. Appropriate measures, such as the elaboration of codes of good agricultural practices and action programs, should be undertaken in order to prevent and/or remediate the contamination of the Nabeul shallow aquifer.     

Probability-based nitrate contamination map of groundwater in Kinmen

Groundwater supplies over 50 % of drinking water in Kinmen. Approximately 16.8 % of groundwater samples in Kinmen exceed the drinking water quality standard (DWQS) of NO₃ ^?-N (10 mg/L). The residents drinking high nitrate-polluted groundwater pose a potential risk to health. To formulate effective water quality management plan and assure a safe drinking water in Kinmen, the detailed spatial distribution of nitrate–N in groundwater is a prerequisite. The aim of this study is to develop an efficient scheme for evaluating spatial distribution of nitrate–N in residential well water using logistic regression (LR) model. A probability-based nitrate–N contamination map in Kinmen is constructed. The LR model predicted the binary occurrence probability of groundwater nitrate–N concentrations exceeding DWQS by simple measurement variables as independent variables, including sampling season, soil type, water table depth, pH, EC, DO, and Eh. The analyzed results reveal that three statistically significant explanatory variables, soil type, pH, and EC, are selected for the forward stepwise LR analysis. The total ratio of correct classification reaches 92.7 %. The highest probability of nitrate–N contamination map presents in the central zone, indicating that groundwater in the central zone should not be used for drinking purposes. Furthermore, a handy EC–pH-probability curve of nitrate–N exceeding the threshold of DWQS was developed. This curve can be used for preliminary screening of nitrate–N contamination in Kinmen groundwater. This study recommended that the local agency should implement the best management practice strategies to control nonpoint nitrogen sources and carry out a systematic monitoring of groundwater quality in residential wells of the high nitrate–N contamination zones.     

Agricultural Chemicals in the Alluvial Aquifer of a Typical County of the Arkansas Delta

Statistical methods and a Geographic Information System (GIS) were used to investigate potential indicators of ground water vulnerability to agricultural chemical contamination in a representative area of the Mississippi River alluvial aquifer. A total of 47 wells were sampled for analysis of nitrate, phosphorus, potassium, and 13 pesticides commonly-used in the area. Ten soil and hydrogeologic variables and five ground water vulnerability indices were examined to explain the variations of chemical concentrations. The results showed that no individual soil or hydrogeologic variables or their linear combinations could explain more than 25% of the variation of the chemical concentrations. A quadratic response surface model with the values of confining unit thickness, slope, soil permeability, depth to ground water, and recharge rate accounted for 62% of the variation of nitrate, 43% of P, and 83% of K, suggesting that the interactions among soil and hydrogeologic variables were significant. Observed trends of decreasing nitrate and P concentrations with increasing well depth and/or depth to ground water seemed to correlate with carbonate equilibrium in the aquifer and more reduced environment with depth. In view of uncertainties involved, it was recognized that the limitations associated with input data resolution used in GIS and the formulation of leaching indices limited their use for predicting ground water vulnerability. Misuse of pesticides could be another factor that would complicate the relationships between pesticide concentrations and the vulnerability indices.     

Impact of anthropogenic activities on water quality of Lidder River in Kashmir Himalayas

The pristine waters of Kashmir Himalaya are showing signs of deterioration due to multiple reasons. This study researches the causes of deteriorating water quality in the Lidder River, one of the main tributaries of Jhelum River in Kashmir Himalaya. The land use and land cover of the Lidder catchment were generated using multi-spectral, bi-seasonal IRS LISS III (October 2005 and May 2006) satellite data to identify the extent of agriculture and horticulture lands that are the main non-point sources of pollution at the catchment scale. A total of 12 water quality parameters were analyzed over a period of 1 year. Water sampling was done at eight different sampling sites, each with a varied topography and distinct land use/land cover, along the length of Lidder River. It was observed that water quality deteriorated during the months of June–August that coincides with the peak tourist flow and maximal agricultural/horticultural activity. Total phosphorus, orthophosphate phosphorus, nitrate nitrogen, and ammoniacal nitrogen showed higher concentration in the months of July and August, while the concentration of dissolved oxygen decreased in the same period, resulting in deterioration in water quality. Moreover, tourism influx in the Lidder Valley shows a drastic increase through the years, and particularly, the number of tourists visiting the valley has increased in the summer months from June to September, which is also responsible for deteriorating the water quality of Lidder River. In addition to this, the extensive use of fertilizers and pesticides in the agriculture and horticulture lands during the growing season (June–August) is also responsible for the deteriorating water quality of Lidder River.     

Hydrogeochemistry and Groundwater Quality Assessment of Lower Part of the Ponnaiyar River Basin, Cuddalore District, South India

The Lower Ponnaiyar River Basin forms an important groundwater province in South India constituted by Tertiary formations dominated by sandstones and overlain by alluvium. The region enjoyed artesian conditions 50 years back but at present frequent failure of monsoon and over exploitation is threatening the aquifer. Further, extensive agricultural and industrial activities and urbanization has resulted in the increase in demand and contamination of the aquifer. To identify the sources and quality of groundwater, water samples from 47 bore wells were collected in an area of 154 km² and were analysed for major ions and trace metals. The results reveal that the groundwater in many places is contaminated by higher concentrations of NO₃, Cl, PO₄ and Fe. Four major hydrochemical facies Ca–Mg–Cl, Na–Cl, Ca–HCO₃ and Na–HCO₃ were identified using Piper trilinear diagram. Salinity, sodium adsorption ratio, and sodium percentage indicate that most of the groundwater samples are not suitable for irrigation as well as for domestic purposes and far from drinking water standards. The most serious pollution threat to groundwater is from nitrate ions, which are associated with sewage and fertilizers application. The present state of the quality of the lower part of Ponnaiyar River Basin is of great concern and the higher concentration of toxic metals (Fe and Ni) may entail various health hazards.     

Organochlorine pesticide residues in ground water of Thiruvallur district, India

Modern agriculture practices reveal an increase in use of pesticides and fertilizers to meet the food demand of increasing population which results in contamination of the environment. In India crop production increased to 100% but the cropping area has increased marginally by 20%. Pesticides have played a major role in achieving the maximum crop production, but maximum usage and accumulation of pesticide residues was highly detrimental to aquatic and other ecosystem. The present study was chosen to know the level of organochlorines contamination in ground water of Thiruvallur district, Tamil Nadu, India. The samples were highly contaminated with DDT, HCH, endosulfan and their derivatives. Among the HCH derivatives, Gamma HCH residues was found maximum of 9.8 μg/l in Arumbakkam open wells. Concentrations of pp-DDT and op-DDT were 14.3 μg/l and 0.8 μg/l. The maximum residue (15.9 μg/l) of endosulfan sulfate was recorded in Kandigai village bore well. The study showed that the ground water samples were highly contaminated with organochlorine residues.     

Groundwater geochemistry and identification of hydrogeochemical processes in a hard rock region, Southern India

Hydrogeochemical investigations were carried out in Chithar River basin, Tamil Nadu, India to identify the major geochemical processes that regulate groundwater chemistry. For this study, long-term (1991–1997) and recent water quality data (2001–2002) for 30 groundwater wells spread over the study area were used to understand the groundwater geochemistry and hydrogeochemical process regulating groundwater quality. Groundwater quality data obtained from more than 400 water samples were employed. Results of electrical conductivity and chloride express large variation between minimum and maximum values and high standard deviation, which suggests that the water chemistry in the study region is not homogeneous and influenced by complex contamination sources and geochemical process. Nitrate and depth to water table expose the influences of surface contamination sources, whereas dissolved silica, fluoride and alkalinity strongly suggest the effect of rock–water interaction. In the study region, weathering of carbonate and silicate minerals and ion exchange reactions predominantly regulate major ion chemistry. Besides, the concentrations of sulphate, chloride and nitrate firmly suggest the impact of agricultural activities such as irrigation return flow, fertiliser application, etc on water chemistry in the study region.     

Assessment of the potential hazards of nitrate contamination in surface and groundwater in a heavily fertilized and intensively cultivated district of India

We made an inventory of nitrate (NO3-N) enrichment in surface and groundwater systems in the Hooghly district of India owing to intensive farming with high fertilizer doses as a function of quantity of fertilizers use, soil characteristics, types of crop grown, depth of groundwater sampling and also N-load in soil profiles. Water samples were collected from different sources at 412 odd sites spread over in 17 blocks of the district along with representative soil profiles. On average, the study area had high clay and NO3-N in soil profiles with an increasing and decreasing trends along depth, respectively. The NO3-N content both in surface and groundwater varied from 0.01 microg mL(-1) to 4.56 microg mL(-1), being well below the threshold limit of 10 microg mL(-1) fixed by WHO for drinking purpose. The content decreased with increasing depth of wells (r = -0.39**) and clay content of soil profiles (r = -0.31**). It, however, increased with increasing rate of fertilizer application (r = 0.72**), NO3-N load in soil profiles (r = 0.85**) and was higher in areas where shallow--rather than deep-rooted crops are grown. Results indicated even under fairly high quantity of fertilizer use, groundwater of the study area is safe for drinking purpose.     

Analysis and evaluation of nitrate levels in groundwater at Al-Hashimiya area, Jordan

Water with high nitrate concentration (NO₃ ⁻) is unfit for human consumption, especially when its concentration exceeded the threshold limit (50 mg/l) recommended by the health authorities such as the World Health Organization (WHO). In Jordan, there is a great concern for determination and monitoring organic and inorganic pollutants that may reach groundwater. Nitrate is highly mobile and present in domestic, agricultural and industrial waste in Jordan, and thus this study focused initially on nitrate as both a contaminant of concern and as an indicator of potential groundwater contamination. The present study determined the extent of nitrate contamination in groundwater in the study area and examined the likely sources of NO₃ ⁻. A total of 248 groundwater samples were collected from 16 wells in different sites of Al-Hashimiya area, Zerqa Governorate, Jordan, and investigated for NO₃ ⁻ concentrations. Moreover, measurements of temperature, electrical conductivity and pH were carried out in the field. Analysis was carried out according to the methods described by the American Public Health Association (APHA). Results showed that there was a dramatic increasing in NO₃ ⁻ concentrations from the year 2001 to 2006 for some selected wells in the present study. NO₃ ⁻ concentration in 2006 was ranged from 10 to 330 mg/l with an average of 77 mg/l. Overall, groundwater had elevated nitrate concentration with 92% of the samples containing more than 20 mg/l NO₃ ⁻, indicating the influence of human activities. This study has shown that there is a strong correlation between the nitrate concentration and the wastewater effluents as a source of pollution.     

occurrence and distribution of nitrate and pesticides in bowdle aquifer, south dakota

A shallow aquifer in central South Dakota was monitored for thepresence of nitrate and pesticides. A total of 593 nitrate samples and428 pesticide samples were analyzed from nine different sites and 14wells between 1989 and 1994. Nested wells were installed at four sitesto characterize the distribution pattern of nitrate and pesticidemovement in ground water. Nitrate concentrations and pesticidedetections were qualitatively compared with area precipitation and watertable fluctuations. The results indicate that nitrates tend to betransported by a leaching mechanism in a matrix flow and may appearin ground water within months after the fertilizer application in thefields. The pesticide movement is primarily controlled by geologicaland chemical characteristics of medium and pesticides.     

Groundwater contamination and its effect on health in Turkey

The sources of groundwater pollution in Turkey are identified, and pathways of contaminants to groundwater are first described. Then, the effects of groundwater quality on health in Turkey are evaluated. In general, sources of groundwater contamination fall into two main categories: natural and anthropogenic sources. Important sources of natural groundwater pollution in Turkey include geological formations, seawater intrusion, and geothermal fluid(s). The major sources of anthropogenic groundwater contamination are agricultural activities, mining waste, industrial waste, on-site septic tank systems, and pollution from imperfect well constructions. The analysis results revealed that natural contamination due to salt and gypsum are mostly found in Central and Mediterranean regions and arsenic in Aegean region. Geothermal fluids which contain fluoride poses a danger for skeleton, dental, and bone problems, especially in the areas of Denizli, Isparta, and Ayd?n. Discharges from surface water bodies contaminate groundwater by infiltration. Evidence of such contamination is found in Upper K?z?l?rmak basin, Gediz basin, and Büyük Melen river basin and some drinking water reservoirs in ?stanbul. Additionally, seawater intrusion causes groundwater quality problems in coastal regions, especially in the Aegean coast. Industrial wastes are also polluting surface and groundwater in industrialized regions of Turkey. Deterioration of water quality as a result of fertilizers and pesticides is another major problem especially in the regions of Mediterranean, Aegean, Central Anatolia, and Marmara. Abandoned mercury mines in the western regions of Turkey, especially in ?anakkale, ?zmir, Mu?la, Kütahya, and Bal?kesir, cause serious groundwater quality problems.     

Spatiotemporal variation of groundwater quality using integrated multivariate statistical and geostatistical approaches in Amol–Babol Plain,Iran

In recent years, groundwater quality has become a global concern due to its effect on human life and natural ecosystems. To assess the groundwater quality in the Amol–Babol Plain, a total of 308 water samples were collected during wet and dry seasons in 2009. The samples were analysed for their physico-chemical and biological constituents. Multivariate statistical analysis and geostatistical techniques were applied to assess the spatial and temporal variabilities of groundwater quality and to identify the main factors and sources of contamination. Principal component analysis (PCA) revealed that seven factors explained around 75 % of the total variance, which highlighted salinity, hardness and biological pollution as the dominant factors affecting the groundwater quality in the Plain. Two-way analysis of variance (ANOVA) was conducted on the dataset to evaluate the spatio-temporal variation. The results showed that there were no significant temporal variations between the two seasons, which explained the similarity between six component factors in dry and wet seasons based on the PCA results. There are also significant spatial differences (p?>?0.05) of the parameters under study, including salinity, potassium, sulphate and dissolved oxygen in the plain. The least significant difference (LSD) test revealed that groundwater salinity in the eastern region is significantly different to the central and western side of the study area. Finally, multivariate analysis and geostatistical techniques were combined as an effective method for demonstrating the spatial structure of multivariate spatial data. It was concluded that multiple natural processes and anthropogenic activities were the main sources of groundwater salinization, hardness and microbiological contamination of the study area.     

MONITORING OF SPATIAL AND TEMPORAL HYDROCHEMICAL CHANGES IN GROUNDWATER UNDER THE CONTAMINATING EFFECTS OF ANTHROPOGENIC ACTIVITIES IN MERSIN REGION, TURKEY

The development of groundwater resources for water supply is a favored way in Turkey. The Berdan alluvial aquifer in Mersin is particularly productive, but little is known about the natural phenomena that govern the groundwater quality and the contamination sources in this region. During 2001 and 2002, water samples for chemical analysis were obtained from 27 wells and from two points of Berdan River and analyzed by ICP. Main chemical characteristics of sampled groundwater define two aquifers, which were also determined by hydrogeological investigations. The groundwater produced from some of the wells was affected by anthropogenic activities temporally and spatially by seawater intrusion. Berdan River is polluted with the wastewater discharges and river water also influences the groundwater quality.     

A Fuzzy Logic Approach to Assess Groundwater Pollution Levels Below Agricultural Fields

A fuzzy logic approach has been developed to assess the groundwater pollution levels below agricultural fields. The data collected for Kumluca Plain of Turkey have been utilized to develop the approach. The plain is known with its intensive agricultural activities, which imply excessive application of fertilizers. The characteristics of the soils and underlying groundwater for this plain were monitored during the years 1999 and 2000. Additionally, an extensive field survey related to the types and yields of crops, fertilizer application and irrigation water was carried out. Both the soil and groundwater have exhibited high levels of nitrogen, phosphorus and salinity with considerable spatial and temporal variations. The pollution level of groundwater at several established stations within the plain were assessed using Fuzzy Logic. Water Pollution Index (WPI) values are calculated by Fuzzy Logic utilizing the most significant groundwater pollutants in the area namely nitrite, nitrate and orthophosphate together with the groundwater vulnerability to pollution. The results of the calculated WPI and the monitoring study have yielded good agreement. WPI indicated high to moderate water pollution levels at Kumluca plain depending on factors such as agricultural age, depth to groundwater, soil characteristics and vulnerability of groundwater to pollution. Fuzzy Logic approach has shown to be a practical, simple and useful tool to assess groundwater pollution levels.     

A multi-lysimeter investigation on the mobility and persistence of pesticides in the loam soil of the Fucino Plain (Italy)

In order to evaluate the impact of intensive horticulture on the water resources of the Fucino Plain, one of the most important agricultural settlements of Central Italy, the mobility and persistence in the soil of five commonly used pesticides was investigated by means of multi-lysimeter experiments. The fate of simazine, carbaryl, dicloran, linuron and procymidone was evaluated in the laboratory under experimental conditions simulating as closely as possible both pesticide application and irrigation practices required by the local crops. An efficient extraction procedure followed by chromatographic analysis, allowing the simultaneous determination of the applied chemicals, was used to monitor the pesticide residues in the soil columns as a function of time from application and depth. The experiment, carried out for about 60 days, revealed that soil contamination apparently involves only the surface layer since none of the investigated pesticides was detected at depths greater than 20-30 cm. However, the five pollutants exhibit a quite different behaviour that can be related to their physico-chemical properties.