Heavy-Metal Assessment of Groundwater in Kushinagar District, Uttar Pradesh and Its Phytotoxic Effect on Wheat Seedlings

Abstract

Background: Heavy metals, characterized by their high density and persistence, include elements such as cadmium, lead, arsenic, and mercury, among others.  These elements can significantly impair agricultural productivity and pose severe risks to both ecological and human health due to their non-biodegradable nature and propensity for bioaccumulation within the food chain. Aims: As heavy metals pose a critical threat to agroecosystems and food safety, the study aims to evaluate the heavy metal contamination in groundwater and its impact on bioaccumulation, translocation, and phytotoxic effects in wheat. Study Design and Location: The location of the study was the Kushinagar District of Uttar Pradesh. The field and laboratory work have been performed for all six tehsils of the district of Kushinagar. Methodology: The samples were collected in sterilised and pre-washed HDPE bottles. The samples were analysed for heavy metals using the ICP-MS method, and wheat seedlings were grown under controlled Petri-dish conditions for exposure. Physiological parameters, along with oxidative stress enzymes, were tested using spectrophotometric methods. The BAF was calculated accordingly. Result: Groundwater samples in Kushinagar district exhibited great variability, Fe (38.21–63.65 ppb), Mn (up to 88.43 ppb), Cr (10.12–17.64 ppb), and as (up to 16.22 ppb) being detected as major contaminants, while Cd (3.48 ppb) was detected at selected sites. When grown in the controlled laboratory conditions, the wheat seedlings demonstrated significant metal accumulation, particularly in roots (Fe up to 70.58 ppb; Cd up to 39.36 ppb), indicating roots as primary sinks. Shoot accumulation was comparatively lower but notable for Fe (58.57 ppb) and Cd (12.34 ppb). Cadmium exhibited exceptionally high bioaccumulation factors (BAF = 11.29–11.15), while Pb and as showed limited accumulation (BAF ≤ 0.40), reflecting restricted mobility. Physiological responses indicated clear phytotoxicity, with reduced shoot length (11.74–13.13 cm vs. 14.31 cm in control) and decreased chlorophyll content (Chl-a reduced from 2.9 to 1.2–1.4 mg/L). Antioxidant enzyme activities increased significantly, with catalase (127.89 μ mol ml⁻¹) and peroxidase (8594.22 μ mol ml⁻¹), indicating oxidative stress adaptation. Germination remained relatively stable (91–94%), suggesting higher sensitivity of post-germination growth stages. Conclusion: Overall, the study establishes a strong linkage between groundwater contamination and heavy metal bioaccumulation in wheat, highlighting cadmium as a critical risk factor. These findings emphasise the necessity of continuous monitoring and sustainable irrigation management to mitigate food chain contamination and ensure agricultural safety.