Risk assessment of potentially toxic metal(loid)s in Vigna radiata L. under wastewater and freshwater irrigation.

Depending on the use and management, wastewater generation can be a severe environmental dilemma or a potential source. Proper application and management of municipal water (MW) in agriculture could be its sustainable use. Until now, there is rare data about the combined application of wastewater and freshwater in agriculture that could be considered as sustainable water management strategy. Also, plant (oxidative) stress responses to wastewater application have been rarely investigated. Here, we elucidated the influence of MW irrigation, diluted with canal water (CW) and groundwater (tap water; TW), on Vigna radiata to evaluate (i) the accumulation of potentially toxic metal(loid)s (PTMs; arsenic, copper, cadmium, iron, manganese, lead, nickel, zinc) in different plant tissues, (ii) biochemical modifications in plants, (iii) relative compartmentation of PTMs inside plant, and (iv) PTMs-induced health risk. Results revealed that the soil-plant transfer of PTMs and physiological changes in V. radiata varied depending on the irrigation water type. Noticeably, plants sequestered most of the PTM contents in roots (average 64%) and less were translocated to plant shoots. All the irrigation treatments provoked oxidative stress in V. radiata with high production of hydrogen peroxide, followed by an oxidation of membrane lipids and a decrease in chlorophyll content. The estimated cancer risk and hazard quotients values revealed a potential risk to human health (HQ: 2.2-108.8, CR: 0.0002-0.664), especially for arsenic, cadmium and lead. The integrated risk estimated from PTMs highlighted the unsuitability of all the treatments for crop irrigation. Therefore, in areas with high PTM levels in MW and freshwaters their mixed use is not an ideal management practice. Conclusively, this study helps to strictly monitor the quality of irrigation water before applying to crops and develop a suitable management and remediation strategy.