Evaluation of Pollution Potential of the Confined Aquifer of Tabriz plain

There is a limited research in the literature on the vulnerability of confined aquifers. In this research as the first one in Iran, the confined aquifer of Tabriz plain has been investigated to evaluate the vulnerablity related to the contaminantion from surface sources. This aquifer is subjected to contamination by various pollutants which may be released from urban areas, industries and farmlands. At first, confined aquifer of the plain has been delineated from unconfined aquifer using study of well information and The hydrochemical Characteristics of aquifer. Five hydrogeological parameters (piezometric level, aquifer media, hydraulic conductivity, distance to confind-unconfined boundary, and pollution potential index of unconfined aquifer) were introduced as the main parameters that impact on the vulnerability of confined aquifers. These parameters were linearly combined using weighted overlay technique to achieve the final index to reflect the vulnerability of the aquifer. The results revealed a vulnerability index value between 47 to 202 indicated that the east and northeast parts of the aquifer had a high vulnerability condition while the west and south parts of the study area had a low and low to moderate risk of pollution. Nitrate concentration distribution map confirmed the results of the vulnerability assessmentand comparing the spatial relationship between the land use and vulnerability zoning maps showed that the most areas of the confined aquifer were under the threat of anthropogenic contaminants. It is recommended to use artificial neural network and fuzzy logic techniqus to verificate the results of this model. In areas with high vulnerability, severe monitoring should be exerted in order to avoidence of pollution from industrial plants, also establishment of new industrial units in the vulnerable zones should be prevented.