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

摘要

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 OErencik Formation, consisting of loose conglomerate, sandstone, mudstone, siltstone, and claystone levels; from the Yoeruek member of the OErencik Formation consisting of limestone, from areas where the Orencik Formation and Yoeruek 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 Orencik 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 Orencik Formation were higher than the average values at geo-thermal 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-rockrninteraction, 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.