Heavy metals status of the urban and agricultural soils of Peshawar, Pakistan

摘要

Soil is a crucial component of urban and rural environments, and in both places land management is the key to soil quality. Unfortunately mining, manufacturing, and the use of synthetic products viz., pesticides, paints, batteries, industrial waste, and land application of industrial or domestic sludge can result in heavy metal contamination of urban and agricultural soils. Heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. Therefore, the present study was mainly conducted to investigate the physico-chemical characteristics and concentrations of heavy metals viz; Zn2+, Fe2+, Cu2+, Mn2+, Cr2+, Cd2+, Ni2+, and Pb2+ in the selected soil samples colleted from three depths receiving municipal wastewater of Peshawar City. Results showed that textural class of the soil varied from silt loam to sandy loam with pH of soil samples ranging from 7.30 to 8.89 with an average value of 8.09 that was slightly alkaline. The EC of the soil samples ranges from 0.2 to 0.9 dS m-1 with an average value of 0.5 dS m-1 showing no salinity problem. The concentrations of Zn2+, Fe2+, Cu2+, Mn2+, Cr2+, Cd2+, Ni2+, and Pb2+ ranges from 0.86-3.98, 11.92-31.73, 2.85-6.83, 14.92-19.19, 0.11-0.86, 0.04-0.58, 0.54-0.96, and 3.16-38.3 mg kg-1 with an average values of 2.14, 21.44, 5.11, 17.59, 0.35, 0.28, 0.73 and 17.18 mg kg-1 in surface soils (0-15cm), respectively. While it ranges from 0.64-3.37, 11.03-23.91, 2.48-6.83, 10.7-16.33, 0.05-0.23, 0.01-0.35, 0.06-0.64 and 1.44-40.36 mg kg-1 with an average values of 1.78, 18.42, 4.31, 14.03, 0.12, 0.15, 0.42 and 12.85 mg kg-1 in sub-surface soils (30-45cm), respectively. The concentrations of Cr2+, Fe2+ and Ni2+ were within safe limits while Cu2+ and Mn2+ concentrations were above the permissible limits of WHO standards. The concentrations of Zn2+, Cd2+ and Pb2+ in the soil samples collected from the bank of municipal wastewater drain of Peshawar city were above the permissible limits of WHO standards. None of the soil samples showed phytotoxically excessive concentrations of aforementioned heavy metals.