Geochemical features of topsoils in the Gaza Strip: natural occurrence and anthropogenic inputs

The aims of this study were to establish the current contents of trace metals and major elements in agricultural soils of the Gaza Strip and to identify the main anthropogenic inputs affecting trace metal contents. An extensive soil survey was conducted in agricultural and nonagricultural areas. One hundred and seventy sites that represent a broad range of soil types and locations were selected. The results revealed that soils in the Gaza Strip fall within the range of uncontaminated to slightly contaminated. Up to 90% of the tested soils had trace metal contents equal to the international background values. Ten percent showed slight contamination, primarily by Zn, Cu, As, and Pb, due to anthropogenic inputs, and the mean concentrations of these elements were 180, 45, 13, and 190 mg/kg, respectively. The trace metal contents varied, with the highest contents detected in the southern regions (where one finds clay soil and low precipitation) and the lowest in the northern areas (where are sandy soil and high precipitation). The soil geochemistry is dependent on soil type and location and to a lesser extent on crop pattern and fertilizer and fungicide application. Anthropogenic inputs lead to the enrichment of Zn, Pb, Cu, and Cd in the agricultural soils. The pollution of several investigated sites was found to be most severe for Zn, Pb, Cu, Cd, and, to a somewhat lesser extent, for As, whereas anthropogenic input of Hg, Ni, and Co seemed to be less important. The application of Cd-containing phosphate fertilizers coupled with Cu-containing fungicides may be an important source of Cd and Cu in several soils. High Zn levels (1000 ppm) in several soils may be caused by sewage sludge, which has an average Zn content of 2000 ppm. Saline-sodic soils were found in the central and southern regions, where the soils are characterized by high contents of Na and salty groundwater. Elevated Cl, Na, Zn, and Pb contents in some areas need further investigation to determine their ecological and health implications.