Geochemical fractionation, source identification and risk assessments for trace metals in agricultural soils adjacent to a city center (Çanakkale, NW Turkey)

Agricultural lands around city centers are exposed to trace metal pollution through urbanization especially and industrialization-related human activities. This study investigates potential sources of trace metals (Cd, Cr, Cu, Ni and Pb) in agricultural lands surrounding Çanakkale city center (NW Turkey) and estimates their environmental impacts with the sequential extraction procedure. Soil samples were taken from agricultural fields adjacent to the city center that represent all types of land use. The aqua regia wet digestion method was used to determine trace metal contents and the sequential extraction procedure was used to determine geochemical fractions of trace metals. Multivariate analysis was applied for source identification of trace metals. Contamination factors and risk assessment codes were used to assess current pollution. Trace metal contents were in the order: Ni > Cr > Pb > Cu > Cd. Recorded values were greater than the values specified for agricultural land. Trace metal mobility based on totals for the first three fractions was in the order: Cd (62%) > Pb (57%) > Cu (40%) > Ni (32%) > Cr (15%) and these findings indicate that Cd and Pb exist mostly in mobile phases. These mobile phases were mostly attributed to anthropogenic sources. These findings comply with the outcomes of statistical analysis. It was concluded that the soils were contaminated with Pb and Cd. While Pb poses moderate risks for the environment, Cd poses high risks. Considering the present findings, it was observed that primarily Cd and partially Pb reached soils near urban areas, exhibited accumulation and may be easily incorporated into water and plants through the mobile phases. Therefore, it is concluded that the relevant metals, especially Cd, should be controlled and monitored.