Impact of Irrigation with Contaminated Water on Heavy Metal Bioaccumulation in Water Chestnut (Trapa natans L.)

Abstract

This study investigated the monitoring of six heavy metals (Cd, Cr, Cu, Fe, Mn, and Zn) in pond water, sludge, and cultivated water chestnut (Trapa natans L.) crops in Saharanpur district of Uttar Pradesh, India. For this purpose, samples of pond water, sludge, and T. natans plant (nut, shoot, and root) were collected in November of 2021 and 2022 from three zones (Zone 1: agricultural area irrigated with borewell water, Zone 2: urban area irrigated with municipal wastewater, and Zone 3: rural area irrigated with mixed type of wastewater) and subsequently analyzed for heavy metal concentration using atomic absorption spectroscopy. The results showed that the physicochemical and heavy metal characteristics of pond water and sludge were significantly (p < 0.05) higher in Zone 2 and 3 than to those in Zone 1. The concentration of heavy metals in T. natans root was comparatively high followed by shoot and nut parts. The bioaccumulation factor (BAF) was maximum while using pond water as a reference medium compared to pond sludge. Overall, the increasing order of heavy metals in T. natans was observed as Cd < Cr < Cu < Zn < Mn < Fe. In the edible part (nut) of T. natans, the average contents of Cd (0.005 ± 0.002 mg/kg), Cr (0.134 ± 0.009 mg/kg), Cu (1.043 ± 0.104 mg/kg), Fe (9.589 ± 0.957 mg/kg), Mn (4.326 ± 0.753 mg/kg), and Zn (1.540 ± 0.537 mg/kg) were comparatively less than shoot and root parts. Overall, the results revealed that T. natans irrigated with contaminated irrigation supplies at Zone 2 and 3 showed the highest BAF of heavy metals than Zone 1. Because the heavy metal concentrations in edible parts of T. natans did not exceed the threshold limits, the contaminated water sources in the Saharanpur region of India should be used in a safe and controlled manner.