Cadmium accumulation in wastewater-irrigated vegetables: Exploring factors, thresholds, health implications, and transfer modeling

Abstract

The Introduction of cadmium (Cd) into the soil-crop system through wastewater (WW) irrigation poses a significant challenge to environmental safety. However, the understanding of the relationship between Cd phytoavailability in WW-irrigated soil and its uptake characteristics in edible vegetables remains largely unknown. This study aims to analyze the influence of WW irrigation on the accumulation characteristics and health risks associated with Cd in the soil-vegetables system. Soil and corresponding vegetable samples were collected from 12 vegetable farms including cabbage, lettuce, green beans, and pepper were studied under wastewater (WW) and freshwater (FW) irrigation. WW irrigation led to a significant increase in soil Cd levels, with enrichment factor, and contamination factor values ranging from 2.9 to 3.1 and 2.7 to 3.3 times higher, respectively, compared to the control. Across the study farms, WW irrigation increased Cd concentrations in cabbage, green beans, lettuce, and pepper by 62–220%, 55–100%, 25–68%, and 29–80%, respectively, compared to FW-irrigated farms. The average hazard quotient (HQ) and carcinogenic risk (CR) scores for Cd in WW-irrigated vegetables indicated low risk (0.1 < HQ) and fell within the permissible range (1.00E-06 < CR < 1.00E-04) for children and adults. The soil DTPA-extractable Cd thresholds for WW-irrigated farms cultivating cabbage, lettuce, green beans, and pepper were 0.62, 0.72, 0.85, and 0.83 mg kg−1, respectively. The results provide insight into the management strategies along with developing sustainable production practices for common leafy vegetables in Cd-enriched soil resulting from WW irrigation.