Effect of freshwater and wastewater irrigation on buildup of toxic elements in soil and maize crop

Untreated wastewater is routinely used for agricultural activities in water-stressed regions, thereby causing severe ecological risks by various pollutants. Hence, management strategies are needed to cope with the environmental issues related to wastewater use in agriculture. This pot study evaluates the effect of mixing either freshwater (FW) or groundwater (GW) with sewage water (SW) on the buildup of potentially toxic elements (PTEs) in soil and maize crop. Results revealed that SW of Vehari contains high levels of Cd (0.08 mg L-1) and Cr (2.3 mg L-1). Mixing of FW and GW with SW increased soil contents of As (22%) and decreased Cd (1%), Cu (1%), Fe (3%), Mn (9%), Ni (9%), Pb (10%), and Zn (4%) than SW alone treatment. Risk indices showed high-degree of soil-contamination and very-high ecological risks. Maize accumulated considerable concentrations of PTEs in roots and shoot with bioconcentration factor > 1 for Cd, Cu, and Pb and transfer factor > 1 for As, Fe, Mn, and Ni. Overall, mixed treatments increased plant contents of As (118%), Cu (7%), Mn (8%), Ni (55%), and Zn (1%), while decreased those of Cd (7%), Fe (5%), and Pb (1%) compared to SW alone treatments. Risk indices predicted possible carcinogenic risks to cow (CR 0.003 > 0.0001) and sheep (CR 0.0121 > 0.0001) due to consumption of maize fodder containing PTEs. Hence, to minimize possible environmental/health hazards, mixing of FW and GW with SW can be an effective strategy. However, the recommendation greatly depends on the composition of mixing waters.

Automated summary

Untreated wastewater used in agriculture poses severe ecological risks due to various pollutants. This study examined the effects of mixing freshwater or groundwater with sewage water on soil and maize crop contamination. Results showed high levels of Cd and Cr in sewage water. Mixing freshwater or groundwater with sewage water increased soil content of As and decreased Cd, Cu, Fe, Mn, Ni, Pb, and Zn compared to sewage water alone. Maize accumulated PTEs in roots and shoots, with potential carcinogenic risks to livestock consuming contaminated fodder. Mixing water sources can be an effective strategy to minimize environmental/health hazards.