R Barzegar; A Asghari Moghaddam; A Nadiri; E Fijani
Abstract
With respect to the concentration of population, agricultural activities and industrial manufactures in Tabriz Plain area, vulnerability assessment of the plain aquifer is very useful for development, management, decision making for land use and preventing groundwater contamination. In this research, ...
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With respect to the concentration of population, agricultural activities and industrial manufactures in Tabriz Plain area, vulnerability assessment of the plain aquifer is very useful for development, management, decision making for land use and preventing groundwater contamination. In this research, vulnerability of the Tabriz plain complex aquifer to contamination was considered by DRASTIC model in GIS media and different fuzzy logic methods adapted to optimize the model. The DRASTIC model uses seven environmental parameters effective on assessment of aquifers vulnerability such as Depth to groundwater level, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity, which created as seven layers in ArcGIS media and weighted, rated and compiled, finally groundwater contamination vulnerability map was prepared and the DRASTIC index for the study area calculated between 40 to 126. The vulnerability map created by DRASTIC is compared to nitrate data and the results indicated a relative correlation between the nitrate level and vulnerability index. The Sugeno, Mamdani and Larsen fuzzy logic methods were adapted for optimizing the weights of the DRASTIC parameters. For this purpose, the DRASTIC parameters as input data and the vulnerability index as output data were defined for fuzzy models and nitrate concentration data were divided in two categories for training and test steps. The output of model in training step was corrected by related nitrate concentration, and after model training, the output of model in test step was verified by nitrate concentration. The results obtained from different fuzzy models show that the Sugeno fuzzy logic model is an applicable and useful method for optimizing DRASTIC model. According to the final model results, the eastern part of the area, inside the Tabriz city limits, has the maximum potential rate for contamination.
A Asghari Moghaddam; R Barzegar
Abstract
The Tabriz plain with an area of more than 700 km2 is extended from the eastern limit of Tabriz city to the salt flats of UrmiaLake. There are two types of aquifers in this plain with different quality of groundwater. The unconfined aquifer, which is extended all over the plain, in recharge areas near ...
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The Tabriz plain with an area of more than 700 km2 is extended from the eastern limit of Tabriz city to the salt flats of UrmiaLake. There are two types of aquifers in this plain with different quality of groundwater. The unconfined aquifer, which is extended all over the plain, in recharge areas near the plain margins has good quality water but in the central part of the plain along the Aji Chay river as well as in the west margin of the Plain is saline. The multi-layer confined aquifers, which lie down in central and western parts of the Plain bearing more or less good quality groundwater. The arsenic concentration of these aquifers is also different; the water samples analyzed from the chemical point of view especially with respect to concentration of arsenic show two different groups of groundwater. The aim of this study is considering of arsenic spatial distribution and factors controlling high arsenic concentration in the aquifers. For this purpose 16 water samples, with evenly distributed in the Plain, were collected from the aquifers, two water samples for each well, one for analyzing major ions and the other for trace elements. They were analyzed in hydrology lab at the TabrizUniversity. The arsenic concentration in unconfined aquifer and in recharge areas of the plain boundary is low and in confined and deep wells is high. Arsenic concentration compared on the basis of their dependency on hydrogeological conditions, nitrate and phosphate concentrations and pH and the results interpreted by factor analysis and hydrogeochemical methods. Attendance of nitrate and phosphate by positive factor and arsenic by negative factor can show the reduction conditions in groundwater system, which caused the arsenic mobilization. In spite of high arsenic concentrations in the water samples, the saturation index of arsenic minerals is very low and under saturation. The arsenic existing in groundwater resources of the area originate from the geological formations and its concentrations depend highly on the hydrogeological and environmental reduction conditions, residence time of water in underground layers and depth of the sampling wells.
