Groundwater Vulnerability potential and Health-risk assessment related to nitrate and nitrite in drinking water in Azna-Aligudarz Plain

In the Azna-Aligudarz plain, the drinking water is mainly supplied from groundwater.  Therefore, it is necessary to estimate the concentration of nitrate and nitrite and determine the groundwater vulnerability potential and related risks in the plain to guarantee the health of consumers.

The vulnerability potential of the studied plain to pollutants was investigated by the drastic method. To estimate the concentration of nitrate and nitrite, 25 water wells in the study area were sampled within 2018-2019 and analyzed by standard method. Human health risk related to groundwater in the study area was assessed using the USEPA (the United States Environmental Protection Agency) index.

The results of the DRASTIC method demonstrated that 45% and 65% of the region has a high (southern part of the plain) and a medium vulnerability potential (northern part of the plain), respectively. According to the obtained results, nitrate in Chaqataram and Ashrafabad villages with 56 and 65 mg/liter, respectively, and nitrite in groundwater of Chamzaman, Aliabad, and Darreh Bagh villages with 3.5, 3.3, and 3.4 mg/liter, was higher than the standard of World Health Organization. According to the health risk assessment results, 83%, 8%, and 4% of children, women, and men are prone to health threats due to nitrate concentration (HQ>1). The accuracy of the vulnerability results was confirmed by calibrating the results of the health risk assessment and the results of the nitrate map.

As e evidenced by the obtained results, improper use of nitrate chemical fertilizers and unsafe disposal of human wastewater (urban and rural) is the main cause of increased nitrate and nitrite concentrations in agricultural lands. Based on the results of the present study, the use of contaminated drinking wells is not recommended and continuous monitoring of drinking wells in the study area is essential to protect the health of consumers, especially children.