Abstract :
ABSTRACT: In the last few decades, the use of nitrogen fertilizer has increased substantially, without taking in to consideration their effects on soil properties, agricultural products and especially on environmental pollution. Nitrate as the main form of nitrogen, causes groundwater pollution as it has negative charge. Due to its good and somehow constant quality and easy exploitation, groundwater is the most important water resource, especially in arid and semi-arid areas. Excessive amounts of nitrate in the drinking water are harmful for humans, livestock and plants. This study aims to investigate the nitrate pollution and its variations in the groundwater of the agricultural, industrial and urban areas of Shahryar area. Shahryar area is located in the arid and semi-arid area of Iran and in dealing with drought in the last few years, using its groundwater has become ever increasingly important. To conduct this research, the area under study was divided in to three districts: Shahryar, Ghods and Malared and with regards to land use, it was divided in to three areas: agricultural, industrial and urban. Totally, 30 wells were chosen for sampling. Sampling the water of these wells was done in five stages (from May to September, 2008) with the time intervals of one month. And the amounts of nitrate, nitrite, pH, electrical conductance and total dissolved solids in the samples were measured. Approximately, in 60 percent of the wells, the concentration of nitrate was more than the standard level (45 mg/L) and during the study period, the mean concentration of nitrate in the water of the wells was varied between 2.9 and 66.2 mg/L. The mean concentration of nitrate in the groundwater of Shahryar, Ghods and Malared districts was 29.8, 35.7 and 54.1 mg/L, respectively. The nitrate concentration was more than the standard level in 53.3, 50 and 85.7 percent of wells in Shahryar, Ghods and Malared, respectively. However, the abundance of nitrate concentration in different districts was not the same. Most of nitrate pollution in the groundwater was observed in the agricultural areas; with the urban and industrial areas placed in the next ranks. Agricultural activities are the most important factor of nitrate pollution in the groundwater and pollution distribution has a very close relationship with these activities. In most of the study areas, the nitrate concentration in the groundwater increased over time and the highest amount of nitrate concentration was related to July 2008.There was no high correlation between nitrate concentration and any of the chemical parameters measured in the groundwater samples
