Nitrate and heavy metal pollution resulting from agricultural activity: a case study from Eskipazar (Karabuk, Turkey)

Abstract

In most countries of the world, groundwater and surface water are at a serious risk of pollution due to chemicals used in agricultural activities. The present study examined whether such a risk exists in Eskipazar, Turkey and the surrounding area, which covers a surface area of 696 km(2). Nitrate pollution (NO(3)) was observed in waters discharging from the A-rencik Formation, consisting of loose conglomerate, sandstone, mudstone, siltstone, and claystone levels; from the Yoruk member of the A-rencik Formation consisting of limestone, from areas where the A-rencik Formation and Yoruk member are located together, and from alluvium. Agricultural is practiced in these areas, and the waters discharging from these formations are used as drinking water and for domestic purposes. In particular, periodically varying levels of pollutants, such as B, Pb, Hg, Se were detected in wells drilled in A-rencik Formation featuring a high NO(3) concentration. The concentrations of S, Cr, Mn, Fe, Cu, Zn, Ga, Br, Sr, Y, I, Ba, and U in these waters are also slightly higher than other cold waters in the study area. In addition to the NO(3) pollution, high levels of Ca and SO(4) pollution was observed at a well drilled in alluvium. In addition, some trace element concentrations identified in the wells drilled in the A-rencik Formation were higher than the average values at geothermal and/or mineral springs in the study area. The study area has an adequate sewage system and has no sources of pollution, such as mineralization, industrial center, waste disposal area, etc. Therefore, it is believed that the main causes of NO(3) and trace element pollution are fertilizers and pesticides used in agricultural activities. Water-rock interaction, usage period of fertilizers and pesticides, amount of precipitation, groundwater level, usage of elements by plants, mobility of elements, pH value of the environment, redox potential, adsorption/desorption, biochemical processes, etc. are thought to be the causes of the periodical variation of some trace element concentrations observed in these waters.