An Approach to Investigate the Impact of Anthropogenic and Geogenic Sources on Heavy Metals Concentration (Case Study: Zanjan Plain Aquifer)

Industrial development, increasing demand for water supply and illegal waste discharge into the aquifers have created major problems in most of the plains. Among the pollutants, heavy metals are considered as common factors due to their wide application in industry and urban communities. Thus, Zanjan plain as the hub of polluting industries is not exempted and the qualitative samples taken from it indicate the presence of different kinds of heavy metals. To investigate the role of natural and artificial factors in creation these pollutants, the used methodology is proposed based on geology, hydro-geochemistry study, the relationship between cations and anions and the distribution of heavy metals.
Using the proposed framework for measuring water quality data in both wet and dry periods, initially, all the factors leading to pollution were identified. Then, the role of anthropogenic and geogenic activities was determined based on a combination of factors involved in pollution of the plain.
Findings: The results indicate that the main part of contamination in the northern half of the plain is due to anthropogenic sources and appears naturally in the aquifer. In the central part of the aquifer, due to the centralization of industry and presence of Zanjan city, geogenic activities were identified to be the source of heavy metals. In other parts, both anthropogenic and geogenic activities were jointly involved in aquifer pollution.
The main source of pollution by heavy metals including Cr, Cu, Fe and Pb in Zanjan aquifer have been natural and geogenic factors. Also, the elements such as Zn, Mn and Cd are mainly associated with human activities and industries that are scattered throughout the plain. According to the evaluations, management strategies can be presented for restoration and control of pollutants input into the aquifer in that part of the plain whose contamination is due to geogenic activities.