Concentration of Lead in Soils and Some Vegetable Plants in North Nile Delta as affected by Soil Type and Irrigation Water

Soil pollution by lead (Pb) is of great concern because of its adverse effect to human health. This study was conducted in the north Nile Delta, Egypt, to investigate the influence of soil type and irrigation water on the total and ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable Pb content of soils and growing vegetable plants. Eight soil profiles were selected from the three representative deposits existing in the area (i.e., fluvial, lacustrine, and marine). Three of them represent the three deposits, which were irrigated with fresh Nile water, whereas the other five represent those irrigated with mixed wastewater. Samples of soils, waters, and vegetable plants growing in the area were selected from the studied locations and analyzed for total [nitric acid (HNO3)-hydrochloric acid (HCl)-hydrogen peroxide (H2O2)-extractable] and available (AB-DTPA-extractable) Pb (soil samples), Pb concentration (water samples), and total Pb after digestion by using perchloric (HClO4)-sulfuric (H2SO4)-nitric (HNO3) acids (plant samples), respectively.The results of this study showed that the mean values of the total and available Pb differed significantly between the studied soils, the higher being in the lacustrine and lower in the marine soils. However, marine soils showed the highest values of Pb availability index. Irrigation with wastewater significantly increased the concentration of the total Pb in fluvial soils compared to those irrigated with Nile water. Total and available Pb concentrations were significantly correlated with clay, silt, organic matter, and equivalent calcium carbonate content, cation exchange capacity, and CBD-extractable iron (Fe), aluminum (Al), and manganese (Mn) (positively) as well as with sand content and soil pH (negatively). Metal content in leaves was found to be higher than in fruits for the different plant species but lower than the upper permissible limits. Values of bioconcentration ratio and accumulation factor of Pb of the growing plants in marine soils were higher than those grown in fluvial and lacustrine soils.