GIS based assessment of cadmium and heavy metals contamination in wastewater-irrigated areas of Multan, Pakistan

Cadmium (Cd) is a highly toxic heavy metal for both plants and animals. Its existence in the agroecosystem is alarming for food security due to its presence in the food chain. The objective of this study was to evaluate “Its persistence in agroecosystems poses serious risks to food safety and ecosystem health to assess Cd contamination risk in wastewater-irrigated soils of Multan, Pakistan. The concentration of Cd and other HMs (Pb, Ni, Zn and Cu) was assessed in 52 soil, plant and wastewater samples. Soil samples were taken from 0-20 cm depths and extracted by AB-DTPA for determination of Cd, Pb, Ni, Zn and Cu. The samples were collected, analyzed and digital maps for the area using GIS (Arc Map 10.3.1) were developed for soil samples. Plant samples were dried and digested in HClO4:HNO3. Soil extract, plants extract and water samples were analyzed using AAS (Analytik Jena nova P400). The concentration of Cd, Pb, Ni, Zn and Cu in soil samples ranged from 0.006-6.62, 0.62-6.23, 0.015-4.23, 0.08-4.47, and 0.09-4.94 mg kg-1 respectively. The average concentration HMs (Cd, Pb, Ni, Zn and Cu) in water samples collected from the study area were 0.011, 0.024, 0.051, 0.066 and 0.142 mg L-1 in canal water samples, 0.0040, 0.019, 0.019, 0.048 and 0.092 mg L-1 in groundwater samples and 0.127, 0.067, 0.032, 0.229 and 0.343 mg L-1 in wastewater samples collected from the area of Multan. HMs concentration in different plant species collected from the area ranged from Cd (0.06-7.27 mg kg-1), Pb (0.18-11.35 mg kg-1) Ni (0.44-12.74 mg kg-1), Zn (0.68-15.50 mg kg-1) and Cu (0.80-14.11 mg kg-1). Pollution indices (Igeo and EF) indicated that soil is contaminated with anthropogenic sources. The mean enrichment factor for the Cd was 8.22 which shows significant enrichment by the anthropogenic sources. While the EF for Pb, Ni and Zn was below the recommended criteria and it illustrated that these metals are naturally present in the soil. The Bioaccumulation factor was found in the sequence of Ni>Zn>Pb>Cu>Cd. Based on the study finding, the wastewater irrigated area of Multan was polluted with Cd and to some extent Pb, Ni, Zn and Cu. This study seeks to assist authorities and researchers in creating a plan of future studies by using GIS effectively, offering GIS-based maps for the assessment and prioritization of control and remediation solutions in the contaminated region.