جواد اشجاری

Most local people in the agricultural areas of Sistan and Baluchestan Province (Iran), generally consume shallow groundwater from farm wells. This study aimed to assess the water quality and health risk potentially of As, Pb, Cr and Ni for drinking purposes in Zarabad aquifer. Also the geochemical processes controlling chemistry of Zarabad aquifer were studied. Piper diagram shows two major hydrochemical facies of Na-Cl/SO4 and Na-SO4/Cl in the groundwater samples. Based on hydrogeochemical results (Composite and Gibbs diagrams), chemistry of groundwater is influenced by water-rock interaction, evaporation and ion exchange. Arsenic, Ni and Pb for 27, 53 and 80% of the groundwater samples show higher concentrations than the maximum acceptable limit for drinking water. According to the WQI values all of the water samples were considered unsuitable for drinking purpose. The results of principal component analysis (PCA) indicate that As, Ni, Pb and Cr have more influence from anthropogenic sources such as application of fertilizers and pesticides in the agricultural lands. The result of health risk assessment shows that the consumption of heavy metals (such as As and Pb) contaminated groundwater poses an emerging health threat to the populations in the study area, and hence needs regular monitoring and management measures.

IntroductionCarbonate formations (including karst springs and wells), have important role in supplying domestic and irrigation water in our country. Along with the exploitation of these resources, it is required to be considered geochemical characteristics and factors affecting water quality changes. Khosh-Yailagh carbonate formation is a formation of Devonian age in the north of Iran. The outcrops are located in mountainous areas and in the margins of Gorganroud plain. The local base level of erosion is high due to particular tectonic behavior. Because of low thickness and coarse texture of alluvium, well yields are not respond to different uses.
Groundwater hydrochemical assessment is usually based on a set of comprehensive information about the chemistry of groundwater. Chemistry of groundwater is affected by different factors such as geology, climate, type of rock weathering reactions, and recharge water quality (Guler et al, 2004; Subramani et al, 2005; Coetsiers, 2006).
The purpose of this study is to evaluate the evolution of geochemical processes and water quality of Khosh-Yailagh carbonate formation. Water quality graphic methods, multivariate statistical methods, hierarchical cluster analysis (HCA), principal components factor analysis (PCA) and chemical mass balance were used in determination of hydrochemical parameters and assessing geochemical process of water of carbonate formation.
Materials and MethodsThe study area located in the east Alborz structural-sedimentary zone in Golestan province, north of Iran between the N36º48' 00" to S37º00'00" and W54º47'00" to W55º08'00". Minimum height in the region of 118 meters and a maximum altitude is 1834 meters. Various formations outcrop in the study area. Khosh-Yailagh is the most important of these formations, which is carbonate with karst development potential.
20 water samples were collected from springs. Field analysis of Temperature, pH and conductivity was done when the sample is collected. The major elements (Na, Ca2,Mg2, K, Cl-, SO42-, HCO3-, NO3-) were analyzed in the lab using standard methods. Composite diagrams were used to indicate relation between different ions. The statistical technique of multivariate analysis was used to characterize hydrochemical processes through data reduction and classification. The factor analysis derived principal components from a correlation matrix and rotated axes with a quartimin rotation.
Discussion of ResultAll of the groundwater samples are low salinity with electrical conductance ranges from 220 to 706μs. All groundwater samples have carbonate-Calcium type. Clustering analysis was used for combining cases (water samples) into clusters. This clustering routine resulted in three groups of water samples on the basis of variables (pH, EC and major elements).
Group 1: low salinity waters (309 ≤ EC ≤ 589μs) (samples 1, 2, 5, 10, 11, 12, 13, 14, 18, and 20). Average TDS of this group is 41.27 mg/l.
Group 2: low salinity waters (451 ≤ EC ≤ 538μs) (samples 4, 7, 8, 15 and 16). Average TDS of this group is 37.22 mg/l.
Group 3: electrical conductance of this group ranges between 495 to 706μs. This group contains samples 3, 6, and 19. These samples indicate more water-rock interaction. Groups 1 and 2 are more similar and could be consider as one group.
Most measured parameters showed weak correlation, which is the evidence on the effects of different processes in the water chemistry. Factor analysis was applied to identify the dominant processes controlling major chemical components of groundwater. The variables for factor analysis were Na, K, Mg2, Ca2, HCO3-, Cl-, SO42-, EC and pH. The virmax orthogonal rotation method was applied. Four factors are extracted to represent the contributions influencing chemical composition of groundwater (Table 1). The variables of TDS and Ca, have high positive loading of factor 1. The variables K and HCO3 have high positive loading of factor 2. The factor loading of pH show high positive value on factor 3. The variables Na and Cl have positive loadings on factors 4.
Table 1. Results of principle component analysis
VARIABLES Component
P1 P2 P3 P4
TDS .916 .507 -.770 -.040
pH -.082 .007 .969 .017
Ca .895 .263 -.004 .009
Mg -.907 .316 .211 .056
Na -.306 .195 -.325 .785
K .190 .844 -.199 .131
HCO3 -.211 .774 -.015 .287
Cl .193 .201 .335 .796
% of variance 24.072 23.207 20.463 17.252
Ion-exchange reactions occurs, both positive and negative direction that depends on the flow distribution and mixing of groundwater. In order to understand the dominant lithology of environment in which water is flowing, the molar ratio of calcium and magnesium was used. Molar ratio of 1.44 represents interaction of water with dolomitic limestone and dolomite formations. Saturation indices of calcite, dolomite and gypsum indicate that the groundwater is not at the chemical evolution.
The processes that govern changes in the groundwater composition, as interpreted from the factor analysis are mainly determined. In plotted Gibbs diagram, the water samples lie in field of water rock interaction. Dissolution and precipitation of carbonate minerals is the main factor controlling chemistry of groundwater in the study area. Cation exchange processes influence the concentration of cation such as Ca, Mg and Na. Rainwater that is charged with biogenic and atmospheric CO2 is another component determines chemistry of groundwater in the recharge area.

Several factors are important to evaluate the potential of karst groundwater resources which can be referred to as hydrogeological (springs), structural (fractures and faults), geological (lithology), topographic (local base level and slope), precipitation and vegetation factors. The aim of this research is to assess the potential of karst groundwater in Dashtak anticline and its effective factors. Accordingly, several thematic maps have been prepared by means of using Geographic Information System (GIS) and Remote Sensing (RS) techniques. The rating has been done in each map by crisp method on a scale from 0 to 9. Weighting of the maps has been performed by using the analytical hierarchical process (paired comparisons), and finally maps have been combined using the index overlay. The final map includes weights from 0 to 9 and the classified map is presented. The results show that karst groundwater potential of the northern part of Dashtak is more than the southern part. The correlation between high groundwater potential areas and high discharge springs indicates that the proposed model can be successfully applied to karstic areas.Several factors are important to evaluate the potential of karst groundwater resources which can be referred to as hydrogeological (springs), structural (fractures and faults), geological (lithology), topographic (local base level and slope), precipitation and vegetation factors. The aim of this research is to assess the potential of karst groundwater in Dashtak anticline and its effective factors. Accordingly, several thematic maps have been prepared by means of using Geographic Information System (GIS) and Remote Sensing (RS) techniques. The rating has been done in each map by crisp method on a scale from 0 to 9. Weighting of the maps has been performed by using the analytical hierarchical process (paired comparisons), and finally maps have been combined using the index overlay. The final map includes weights from 0 to 9 and the classified map is presented. The results show that karst groundwater potential of the northern part of Dashtak is more than the southern part. The correlation between high groundwater potential areas and high discharge springs indicates that the proposed model can be successfully applied to karstic areas.Several factors are important to evaluate the potential of karst groundwater resources which can be referred to as hydrogeological (springs), structural (fractures and faults), geological (lithology), topographic (local base level and slope), precipitation and vegetation factors. The aim of this research is to assess the potential of karst groundwater in Dashtak anticline and its effective factors. Accordingly, several thematic maps have been prepared by means of using Geographic Information System (GIS) and Remote Sensing (RS) techniques. The rating has been done in each map by crisp method on a scale from 0 to 9. Weighting of the maps has been performed by using the analytical hierarchical process (paired comparisons), and finally maps have been combined using the index overlay. The final map includes weights from 0 to 9 and the classified map is presented. The results show that karst groundwater potential of the northern part of Dashtak is more than the southern part. The correlation between high groundwater potential areas and high discharge springs indicates that the proposed model can be successfully applied to karstic areas.Several factors are important to evaluate the potential of karst groundwater resources which can be referred to as hydrogeological (springs), structural (fractures and faults), geological (lithology), topographic (local base level and slope), precipitation and vegetation factors. The aim of this research is to assess the potential of karst groundwater in Dashtak anticline and its effective factors. Accordingly, several thematic maps have been prepared by means of using Geographic Information System (GIS) and Remote Sensing (RS) techniques. The rating has been done in each map by crisp method on a scale from 0 to 9. Weighting of the maps has been performed by using the analytical hierarchical process (paired comparisons), and finally maps have been combined using the index overlay. The final map includes weights from 0 to 9 and the classified map is presented. The results show that karst groundwater potential of the northern part of Dashtak is more than the southern part. The correlation between high groundwater potential areas and high discharge springs indicates that the proposed model can be successfully applied to karstic areas.

One of the major issues in dam construction is water seepage، post impounding. Assessment and prediction of the amount of water leakage can be useful in preventing such events. The Seymareh dam has been constructed on the Seymareh River in Ilam province، Southwest of Iran. The dam controls the floods and generates hydroelectric power. It is already under impoundment and the seepage problem is being considered. Grout curtains have been employed in two directions at the right abutment of the dam to control the seepage. The normal reservoir level is 720 m and it has been impounded at the 660 m level up to the point. The purpose of this study is to predict the amount of water seepage through the right abutment of the dam by using numerical modeling. For this purpose، a new GW finite element code was used for a two-dimensional simulation of the water seepage. The Levels of the observations wells and the discharges of the downstream springs on the right river bank are used as the main data for this modeling and its verification. Assessments show that if the dam impoundment rises to the normal level، significant seepage may occur through the right abutment.

Understanding of bacteria transport within saturated porous media is essential for protecting groundwater from microbial contamination. In this research, the transport of E. coli in homogenous saturated porous media was investigated. The main objective was to evaluate velocity and behavior of E. coli transpor through Loamy sand layer. Comparing E. coli biological tracer with Uranine tracer and also hydraulic dispersion investigation are other purposes of this paper. To achieve these purposes, a physical model withthree sizes of particle were used in these transport experiments. The bacteria suspension were injected in a hole at one side and water were sampled in two holes located at axial distances of 20 and 60 cm from the injection point, two marginal sampling holes at a distance of 40 cm from the injection point and at the output of the model. The results indicated that the advection component has a significant influence on Bacteria movement, but in marginal holes the potency of advection is reduced and causes the repining phenomenon that is observed in marginal holes curves. Bacteria plume indicated a significant difference from conservative tracer. Unlike conservative tracer, bacteria breakthrough curve had three peaks showing front, mean and ripped tile, respectively and bacteria plume has oblong shape.

This study investigated the karst development in Poyon anticline, Southwest of Iran. For this propose, the parameters of karst development including lithology, slope, vegetation density, faults, distance from faults, lineament density, distance from lineaments, precipitation, and temperature were investigated. Using Analytical Hierarchy Process (AHP) the weight of each layer on karst development was estimated. Final map of karst development was extracted by combination of effective layers. The results showed that 59 percent of Poyon anticline area had high karstification potential, 5.3 percent had moderate potential, and 35.7 percent had either very low potential or no karstification potential. Areas with high potential of karst development are located in north of karst aquifer (Ilam - Sarvak Formation). Springs with high discharge were noted mainly in karst areas with high potential. The result can be adapted for aquifer development management.