Groundwater contamination and its effect on health in Turkey

Hydrogeochemical properties of groundwater and associated human health hazards in coastal multiaquifers of India

Due to the scarcity of water supplies, coastal groundwater quality most importantly influences sustainable development in the coastal region. Rising groundwater pollution through heavy metal contamination is an intense health hazard and environmental concern worldwide. This study shows that 27%, 32%, and 10% of the total area come under the categories very high, high, and very low human health hazard index (HHHI) accordingly. This area's water quality is also much polluted; the study shows approximately 1% has very good water quality. High concentrations of Fe, As, TDS, Mg2+, Na, and Cl- are relatively noticed in the portion of the western part of this district. The concentration of heavy metals in coastal aquifers influences the groundwater pollution of that region. The average heavy metal concentration in this region is 0.20 mg/l (As) and 1.160 mg/l (TDS). The groundwater quality and hydrogeochemical properties are determined through the Piper diagram. The study stated that TDS, Cl- (mg/l), and Na+ (mg/l) are the most regulatory issues of vulnerability. In the present study region, a huge number of alkaline substances are present resulting in the water being unfit for drinking purposes. Lastly, it is clear from the study's findings that multiple risks exist there like As, TDS, Cl-, and other hydrochemical parameters in the groundwater. The proposed approach applied in this research work may be a pivotal tool for predicting groundwater vulnerability in other regions.

Health risk assessment of toxic elements in groundwater in a major industrial and agricultural basin, (East of Ergene Basin, Turkey)

Ergene Basin is an important agricultural and industrial region and an important water resource. In this current research, groundwater quality of east of Ergene Basin was evaluated using water quality index (WQI), and health risk due to groundwater consumption was assessed with HQ, HI, and CR. Multivariate statistical analyses were performed to evaluate the multiple effects of pollutants on groundwater. Uncertainty and sensitivity analyses were also performed. All samples were in the "excellent" WQI category. Health risk values for adults and children were below the safe limit, both from digestion and dermal exposure. CR values of As in some samples exceeded the threshold value, both for adults and children. Sensitivity analysis revealed that ingestion rate and exposure frequency for adults and exposure duration and concentration of toxic metal for children were the most sensitive variables affecting probabilistic health risk.

Nitrates in Turkish waters: sources, mechanisms, impacts, and mitigation

Intensive technological developments, rapid population growth and urbanization, and excessive use of nitrogen fertilizers have caused water resources to be contaminated substantially by nitrates in Turkey. The accumulated information should be evaluated to draw a nationwide attention to the problem. The aim of this review article was to highlight the importance of nitrate (NO3) contamination and to discuss the measures to be taken to mitigate the contamination across the nation. Agriculture, especially chemical fertilizers used in irrigated agriculture, was the most important source of NO3 in groundwater. Also, the industrial and domestic discharges substantially contributed to NO3 in both groundwater and surface waters in many cases. The most severe and widespread groundwater (e.g., 344 mg NO3 L-1 in İzmir, 476 mg L-1 in Afyon, 477 mg L-1 in Antalya, and 948.0 mg L-1 in Konya) and surface water contaminations (e.g., 293.8 mg NO3 L-1 in İzmir, 63.3 mg L-1 in Eskişehir, 89.8 mg L-1 in Edirne, and 90.6 mg L-1 in Sakarya) occurred in the regions where intensive agriculture, industrial development, and rapid urbanization were clustered. Well-established irrigation and fertilizer management plans are critical for reducing fertilizer-related NO3 contaminations in the irrigated agriculture. Special attention should be given to the regions where industrially and domestically contaminated running water bodies are in contact with groundwater. Discharge of wastewaters to the streams, creeks, rivers, and lakes should be prevented. Well-designed studies are needed to evaluate potential health effects, including the risk of cancer, of NO3 in drinking water.

Identifying Geogenic and Anthropogenic Aluminum Pollution on Different Spatial Distributions and Removal of Natural Waters and Soil in Çanakkale, Turkey

The Çanakkale-Kirazlı region (Turkey) is enriched with minerals, especially aluminum (Al), which dangerously get transported into aquatic media due to several mining and geological activities in recent years. In this study, Al and other potentially toxic metals (PTMs) including B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Si, and Zn, in both water and soil samples, were measured for quality determination. Selected metals were also analyzed by the enrichment factor (EF), the geoaccumulation index (I _geo), the contamination factor (CF), and the pollution load index (PLI) to evaluate both water and soil pollution geogenically or anthropogenically. Also, the metals were clustered to support the pollution source with Pearson's correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA). Forty-five natural water samples and 12 soil samples were collected spatially. To perform pollution assessment, two fundamental treatment processes to remove Al pollution from the sample including the highest Al concentration (38.38 mg/L) in water were applied: (1) precipitation with pH adjustment and (2) removal with ion exchange. The pH values of water samples were changed in the range of 3-9 to test the dissolution of Al. The results demonstrated that the study area was mostly under the influence of geogenic aluminum pollution.

Hydrogeochemical characterization of groundwater and their associated potential health risks

The present study assessed the human health risk exposure from the consumption of poor quality groundwater in the Lucknow area, a part of Central Ganga alluvial plain in India. Around 27 (n = 27) groundwater samples were collected from the study area. The analytical results of the samples (n = 27) collected indicate silicate and carbonate weathering is the dominant process along with cation exchange, sulfide oxidation, and reverse ion exchange. The type of groundwater is Ca²-Na-HCO₃^- type having all cations and anions within permissible WHO limits except for iron (Fe²⁺) and nitrate (NO₃^-). The high concentrations of Fe² and NO₃^- in samples indicate the possibility of a non-geogenic point source for the same in an urban-influenced environment. The ionic concentration of dissolved constituents is used in weighted overlay analysis to generate the water quality index (WQI). WQI indicates that most urban areas (~ 98.52%) have fallen in the good to excellent category except few situated in the highly populated parts of Lucknow. The ionic concentrations of Fe²⁺ and NO₃^- have been further used to estimate human health risk by integrating regional urban population density data in Lucknow. The risk map shows alarming risks in the west-central part, where nearly ~ 35% of the total area is at moderate to high health risk.

Determination of PCDD/F and DL-PCB pollution levels, source appointment and risk assessment of surface sediments in dam lakes in Istanbul, Türkiye

The current situation of the water resources of Istanbul, which is one of the important metropolises of Europe, should be known and constantly monitored by the reasons of the rapid increase in the city population, the acceleration of production-related industrial activities, the expansion of the city with construction activities, and the decrease in precipitation. The purpose of this study was to reveal the situations of surface sediments collected from Istanbul water reservoirs in terms of PCDD/Fs and DL-PCBs, to identify possible sources, and to conduct their ecological risk assessment. Total PCDD/Fs and DL-PCBs concentrations varied between 28.13 and 457.4 pg/g (average 136.8 pg/g) and 12.19-340.1 pg/g (average 72.09 pg/g). The corresponding TEQ values of PCDD/Fs and DL-PCBs were between 0.53 and 5.37 pg TEQ/g (average 2.23 pg TEQ/g) and 0.02-0.44 pg TEQ/g (average 0.12 pg TEQ/g), respectively. Octachlorodibenzo-p-dioxin (OCDD) is the dominant congener by constituting about 75% of the total PCDD/Fs on average, while congener distributions of DL-PCBs showed the dominance of PCB-118 and PCB-105. The sediments taken from Kazandere dam have the lowest pollution levels for both PCDD/Fs and DL-PCBs. The highest PCDD/F and DL-PCB amounts were measured in sediments of Alibey and Elmalı dams (closest to highly populated settlements of Istanbul), which are most affected by the air pollution caused by the traffic, commercial/industrial combustion (like waste incineration facility) and combustion for residential heating. Almost all the sediments have total dioxin-like toxicity levels higher than the safe threshold level (with two exceptions) of 0.85 pg TEQ/g dw, proposed for ecological risk. Health risk assessment shows that levels of dioxin-like compounds would result in a total intake of 0.33 pg TEQ/kg bw/day even in the worst-case scenario, not exceeding the tolerable daily intake value of 1 pg TEQ/kg bw/day. Among exposure pathways, consumption of fish constitutes almost all the total intake, while contributions of other pathways are minimal.

Disruption of Leydig cell steroidogenic function by sodium arsenite and/or sodium fluoride

Arsenite (As) and fluoride (F), both of which are linked to a variety of human ailments, are regularly found in underground drinking water. Numerous studies have shown that As and/or F have negative impacts on testicular function and fertility. For this purpose, mouse Leydig cells, the main cells responsible for the generation and regulation of steroid hormones such as testosterone, were used to reveal the effects of individual and combined exposure of As and F on the steroidogenic pathway in the male reproductive system. Leydig cells were treated with 0.39 μM (50 ppb) As and 0.0476 mM (2 ppm) F alone and in combination for 24 h. The findings revealed that As and/or F exposure induced oxidative stress and apoptosis in Leydig cells and altered antioxidant equilibrium of the cells by reducing superoxide dismutase, catalase, glutathione peroxidase. Additionally, individual and combined administration of As and/or F significantly supressed the expression of both steroidogenic enzymes and the genes encoding these enzymes. In conclusion, this study showed that exposure to As and F at environmentally relevant concentrations dispersed by water decreased testosterone production in Leydig cells, an important cell of the male reproductive system. The deleterious effects of even the lowest concentrations of As and F elements that can reach humans from the environment on the Leydig cell, and therefore on male infertility, emphasize necessity new safe limits for these elements.

Synergistic effects of arsenic and fluoride on oxidative stress and apoptotic pathway in Leydig and Sertoli cells

Excessive intake of arsenic (As) and fluoride (F), which are present in underground drinking water, have adverse effects on human health, and especially on the male reproductive system. In this regard, it's critical to figure out how As and F affect Leydig and Sertoli cells, which are key cells in the male reproductive system. The goal of this study was to determine the synergistic effects of co-exposure of As and F, via drinking water, on Leydig and Sertoli cells, which are models for the male reproductive system, as well as the mechanisms underlying these effects in terms of oxidative damage and apoptosis. Leydig and Sertoli cells were exposed to concentrations of 7.7 µM (0.57 ppm) As and 0.4 mM (7.24 ppm) F based on the highest daily intake of drinking water for 24 h. The present results revealed that As and/or F treatment reduced cell viability and proliferation in Leydig and Sertoli cells, elevated lactate dehydrogenase, a cytotoxicity marker, and triggered oxidative stress and apoptosis. Furthermore, it has been proven that when As and F are exposed in combination, they have a synergistic effect. In conclusion, by revealing the harmful effects of As and F on Leydig and Sertoli cells, and thus on male infertility, it is possible to reduce As and F exposure to prevent infertility after exposure to these molecules not only separately but also together. It will be considered to determine new action and action plans to reduce As and F exposure.

Predicting regional fluoride concentrations at public and domestic supply depths in basin-fill aquifers of the western United States using a random forest model

A random forest regression (RFR) model was applied to over 12,000 wells with measured fluoride (F) concentrations in untreated groundwater to predict F concentrations at depths used for domestic and public supply in basin-fill aquifers of the western United States. The model relied on twenty-two regional-scale environmental and surficial predictor variables selected to represent factors known to control F concentrations in groundwater. The testing model fit R² and RMSE were 0.52 and 0.78 mg/L. Comparisons of measured to predicted proportions of four F-concentrations categories (<0.7 mg/L, 0.7-2 mg/L, >2 mg/L - 4 mg/L, and > 4 mg/L) indicate that the model performed well at making regional-scale predictions. Differences between measured and predicted proportions indicate underprediction of measured F at values by between 4 and 20 mg/L, representing less than 1% of the regional scale predicted values. These residuals most often map to geographic regions where local-scale processes including evaporative discharge in closed basins or intermittent streams concentrate fluoride in shallow groundwater. Despite this, the RFR model provides spatially continuous F predictions across the basin-fill aquifers where discrete samples are missing. Further, the predictions capture documented areas that exceed the F maximum contaminant level for drinking water of 4 mg/L and areas that are below the oral-health benchmark of 0.7 mg/L. These predictions can be used to estimate fluoride concentrations in unmonitored areas and to aid in identifying geographic areas that may require further investigation at localized scales.

A holistic study on fluoride-contaminated groundwater models and its widespread effects in healthcare and irrigation

Groundwater is a key resource in the world. Its importance is often undermined, despite the various applications which include irrigation, drinking, sanitation, and industrial uses. One of the contaminants of groundwater is fluoride or the fluorine ion. Fluoride is a common pollutant of water, carrying potential benefits and costs to various sectors. Fluoride contamination of groundwater can impact humans, animals, healthcare, and the agricultural sector in direct or indirect ways. This paper aims to establish the definition of fluoride contamination of groundwater and simultaneously provide an outline of a few common sources that may cause fluoride contamination. Furthermore, this study will lay out the impacts of fluoride-contaminated groundwater on two sectors: healthcare and agriculture/irrigation. This study will also summarize various other research projects conducted across the world, which deliver promising evidence to support the points made throughout the paper. In addition to a detailed analysis of the impacts of fluoride on the healthcare and agricultural sector, this study also evaluates few other challenges which this issue poses and how to overcome them in the near future. A summation of deflouridation techniques is included, along with the future scope pertaining to the field of fluoride contamination. Another objective of the study is to spread awareness about the various health impacts that fluoride contamination poses and encourages consumption of fluoride in accordance with the set limit of 0.5-1.5 mg/L. The motivation behind writing this review is to compile and document various researches, along with an address on this prevalent issue to minimize the detrimental impacts and potential health risks on the society. The results of this study help to minimize risks in the future and encourage scientists to come up with mitigation strategies to ensure a safer environment.

Groundwater quality assessment using the weighted arithmetic index method in the selected villages of Butchayyapeta Mandal, Visakhapatnam, Andhra Pradesh, India

Groundwater quality assessment is an important measure to determine the usability of available water based on its physical, chemical, and bacteriological properties. In the present study, 10 physicochemical parameters have been considered for the groundwater quality assessment which include potential of hydrogen (pH), electrical conductivity (EC), total dissolved solids (TDS), sodium (Na⁺), potassium (K⁺), total hardness (TH), calcium (Ca²⁺), magnesium (Mg²⁺), bicarbonate (HCO₃^-), and chloride (Cl^-). For the analysis, 21 samples for pre- and post-monsoon periods were collected from the wells/bore wells of five designated villages, Chinna Madina, Chittiyyapalem, Typuram, Rajam, and Neelakantapuram of the Butchayyapeta Mandal (sub-district) located in Visakhapatnam District, Andhra Pradesh, for the year 2017. The Bureau of Indian Standards (BIS 2012) has been used in this study to assess the suitability of the water for drinking. The water quality index (WQI) values derived by using WAI were categorized for various levels of water quality ranging from "excellent" to "unsuitable for drinking." To get the spatial distribution pattern, the WQI values of sample points were interpolated in the Arc GIS environment. The results indicated that water quality is good in the north-western parts of the current study area during pre- and post-monsoon seasons.

Boron Bioaccumulation by the Dominant Macrophytes Grown in Various Discharge Water Environments

Turkey has the largest boron (B) reserves in the world (> 70 %). Therefore, the land and water resources in Turkey contaminated with high concentration of B Pollution due to mining and industrial operations. This study investigates the accumulation of B in aquatic macrophytes soil and water in the both mining and municipal waste water discharges. For this purpose, soil, plant and water samples were collected from the streams at the areas of mining and municipal waste water discharge sites and analyzed for B using ICP-MS. Results show that the Xanthium strumarium, Eupatorium cannabinum, Lythrum salicaria, Tamarix tetrandra, Typha latifolia, and Salix sp. hyperaccumulate B. These hyperaccumulator plants have a great capacity to accumulate and transport B to plant parts from the soil and water. Therefore, these plants can be useful for decontaminating or rehabilitation of soils and waters polluted with B.

Simulation-Based Solutions Reducing Soil and Groundwater Contamination from Fertilizers in Arid and Semi-Arid Regions: Case Study the Eastern Nile Delta, Egypt

Intensive agriculture requires increasing application of fertilizers in order to sustain food production. Improper use of these substances in combination with increasing seawater intrusion results in long-term and nonpoint soil and groundwater contamination. In this work, a 3-D groundwater and solute transport numerical model was created to simulate the effect of excessive fertilizers application along the Bahr El Baqar drain system, in the eastern Nile Delta, Egypt. The geotechnical properties of the soils, hydrologic parameters, and unconfined compressive strength were determined at different sites and used as input parameters for the model. Model results showed that silty clay soils are able to contain the contaminations and preserve the groundwater quality. Nevertheless, sandy soils primarily located at the beginning of the Bahr El Baqar drain allow leakage of fertilizers to the groundwater. Thus, fertilizer application should be properly managed in the top sandy layers to protect the groundwater and soil, as increasing aquifer by excess irrigation water increased the groundwater contamination in confined layers due to the high value of cumulative salt for the current situation while the unconfined zone decreased groundwater and soil contamination. A mass transport 3-D multi-species (MT3D) model was set to identify the optimal measure to tackle soil and groundwater contamination along the Bahr El-Baqar drain system. A potential increase of the abstraction rates in the study area has a positive impact in reducing the transfer of fertilizer contamination to groundwater while it has a negative impact for soil contamination. The scenario analysis further indicated that the installation of a drainage network decreases the groundwater and soil contamination. Both solutions are potentially effective for protection against nonpoint contamination along the Bahr El Baqar drain system. However, a more sustainable management approach of fertilizer application is needed to adequately protect the receptors located further downstream in the Nile Delta.

Underground Barrier Wall Evaluation for Controlling Saltwater Intrusion in Sloping Unconfined Coastal Aquifers

Barrier walls are considered one of the most effective methods for facilitating the retreat of saltwater intrusion (SWI). This research plans to examine the effect of using barrier walls for controlling of SWI in sloped unconfined aquifers. The sloping unconfined aquifer is considered with three different bed slopes. The SEAWAT model is implemented to simulate the SWI. For model validation, the numerical results of the seawater wedge at steady state were compared with the analytical solution. Increasing the ratio of flow barrier depth (db/d) forced the saltwater interface to move seaward and increased the repulsion ratio (R). With a positive sloping bed, further embedding the barrier wall from 0.2 to 0.7 caused R to increase from 0.3% to 59%, while it increased from 1.8% to 41.7% and from 3.4% to 46.9% in the case of negative and horizontal slopes, respectively. Embedding the barrier wall to a db/d value of more than 0.4 achieved a greater R value in the three bed-sloping cases. Installing the barrier wall near the saltwater side with greater depth contributed to the retreat of the SWI. With a negative bed slope, moving the barrier wall from Xb/Lo = 1.0 toward the saltwater side (Xb/Lo = 0.2) increased R from 7.21% to 68.75%, whereas R increased from 5.3% to 67% for the horizontal sloping bed and from 5.1% to 64% for the positive sloping bed. The numerical results for the Akrotiri coastal aquifer confirm that the embedment of the barrier wall significantly affects the controlling of SWI by increasing the repulsion ratio (R) and decreasing the SWI length ratio (L/La). Cost-benefit analysis is recommended to determine the optimal design of barrier walls for increasing the cost-effectiveness of the application of barrier walls as a countermeasure for controlling and preventing SWI in sloped unconfined aquifers.

Integrated Modelling for Groundwater Contamination from Polluted Streams Using New Protection Process Techniques

Evaluating water quality indicators is a crucial issue in integrated water resource management, since potable water is an essential resource for the world's health and sustainable development. The current study was developed using a coupled model of MODFLOW and MT3DMS (Mass Transport 3-Dimension Multi-Species) to integrate two water supply systems, surface water (polluted drains and canals) and ground water, to identify the contamination process of the groundwater from drains as fresh water is polluted and the contamination level exceeds the standard limits. The study was applied to two cases: the first was a hypothetical simulation and the second was the real case of the Nile Delta Aquifer (NDA). Four different scenarios were simulated to first identify groundwater contamination by total dissolved solids (TDS), and then select the more efficient protection process. The first scenario involved changing polluted drain and canal boundary conditions regarding head and concentration; the second consisted of studying the location of the polluted drain in a low permeability layer or a confined aquifer; the third was based on installing a cut-off wall in the polluted drain sides; and the fourth investigated the use of lining materials for polluted drains. The results reveal that aquifer contamination was decreased by increasing the water head of canals by 50 cm and decreasing the drain head by 50 cm and concentration by 25%, whereby large quantities of groundwater were protected. The percentages of salt repulsion in the hypothetical case were +10.66, +12.89, and +24.99%, while in NDA they were +6.29, +8.71, and +25% respectively compared with the base case. Decreasing the aquifer hydraulic conductivity led to decrease in aquifer contamination, in which the confined aquifer pollution was less than the unconfined aquifers due to the clay cap, which plays a significant role in minimizing the solute transport into the groundwater reservoir, and to reduction of the aquifer salt variation by +19.01% for the hypothetical case. The results indicate that the cut-off wall is effective for contamination management in shallow aquifers (hypothetical case) and the reduction in aquifer salt was +28.49%, whereas it had no effect in the deep aquifer (NDA), where the salt was reduced by just +0.34%. Using the drain lining scenario prevented contamination from the polluted drains and protected the freshwater in the aquifer, so that the aquifer salt mass reductions were +91.02 and +70.13% for the hypothetical case and NDA respectively, indicating that this method is more effective for controlling groundwater contamination. Polluted drains should be located in a low permeability layer to minimize the water degradation. This study represents a new contribution to groundwater protection techniques by changing the boundary conditions, installing a cut-off wall and using linings for polluted drains, and shows the way forward for the future treatment of polluted stream networks.

Evaluation of potential human health risk and investigation of drinking water quality in Isparta city center (Turkey)

Isparta city center is selected as a work area in this study because the public believes that the tap water is dirty and harmful. In this study, the city's drinking water in the distribution system and other spring waters which are used as drinking water in this region were investigated from the point of water quality and health risk assessment. Water samples were collected from major drinking water springs, tap waters, treatment plants and dam pond in the Isparta province center. Ca-Mg-HCO3, Mg-Ca-HCO3, Ca-Na-HCO3, Ca-HCO3, Ca-HCO3-SO4 and Ca-Mg-HCO3-SO4 are dominant water types. When compared to drinking water guidelines established by World Health Organization and Turkey, much greater attention should be paid to As, Br, Fe, F, NH4, PO4 through varied chemicals above the critical values. The increases of As, Fe, F, NH4 and PO4 are related to water-rock interaction. In tap waters, the increases of As and Fe are due to corrosion of pipes in drinking water distribution systems. The major toxic and carcinogenic chemicals within drinking water are As and Br for both tap water and spring water. Also, F is the non-carcinogenic chemical for only spring waters in the study area.

Statistical analysis of causes of death (2005-2010) in villages of Simav Plain, Turkey, with high arsenic levels in drinking water supplies

The purpose of this research was to compare the causes of death in 5 villages situated in Simav Plain, Turkey, during 2005-2010 where different arsenic levels were detected in drinking water supplies. Since groundwater in Simav Plain had arsenic concentrations that ranged between 7.1 and 833.9 ppb, a two-phase research was formulated. In the first phase, public health surveys were conducted with 1,003 villagers to determine the distribution of diseases. In the second phase, verbal autopsy surveys and official death records were used to investigate the causes of death. In total, 402 death cases were found in the study area where cardiovascular system diseases (44%) and cancers (15.2%) were major causes. Cancers of lung (44.3%), prostate (9.8%), colon (9.8%), and stomach (8.2%) were comparably higher in villages with high arsenic levels in drinking water supplies. Furthermore, the majority of cases of liver, bladder, and stomach cancers were observed in villages with high arsenic levels.

Human health risk assessment of groundwater in Hetao Plain (Inner Mongolia Autonomous Region, China)

Groundwater quality significantly affects public health. In order to better understand groundwater suitability, a total of 887 shallow groundwater samples were collected from the Hetao Plain (HP), Inner Mongolia, China; the maximum and minimum health guideline values of each element were established in this work. Subsequently, the desirability functions (DFs) theory was employed to evaluate the human health risk of groundwater. The results indicate that 780 of the samples were unsuitable for drinking purposes due to the iron, total dissolved solids (TDS), arsenic, strontium, fluoride, and manganese concentrations present, all of which exceeded their maximum guideline value (MaGV). Only 107 samples were suitable for drinking use; however, these samples also have adverse effects on human health to some extent, due to the extremely lower concentrations of nutrient elements and existence of non-nutrient elements. Based on the observed results, groundwater that is unsuitable for drinking use must undergo bacteriological treatment prior to consumption. It was necessary for residents in the western, central, and northeastern parts of the study area are required to be supplied with certain nutrient elements, such as iron, iodine, molybdenum, manganese, and lithium. According to the human health risk assessment of groundwater, the general public can safely and reasonably consume the groundwater for drinking, agriculture irrigation, and industrial purposes.

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.