Post-pandemic assessment: A 3-year study of heavy metal risks in Mizoram's paddy agroecosystem

This study examines the impact of easing COVID-19 restrictions on heavy metal concentrations in paddy soil and rice in Mizoram, India (2021-2023). Concentrations of copper, manganese, zinc, iron, nickel, lead, arsenic, and cadmium were measured using ICP-MS. The Bioaccumulation Factor, Pollution Index, and Health Risk Index were calculated, which assessed metal uptake, pollution level, and health hazards, respectively. Post-pandemic, average heavy metal levels in soil increased significantly, likely due to resumed anthropogenic activities. Notably, nickel reached 0.94 mg/kg (N. Vanlaiphai), lead 0.93 mg/kg (Champhai), and arsenic 1.47 mg/kg (Kolasib), exceeded the permissible limits. Corresponding increases in average concentration of heavy metal in rice were also recorded, with lead up to 0.18 mg/kg (N. Vanlaiphai) and arsenic between 0.04 and 0.05 mg/kg in all the sites, again surpassing the permissible limits. Spearman correlation analysis revealed a strong soil-to-rice correlation for cadmium (0.77) and moderate correlations (0.5-0.6) for copper, manganese, zinc, iron, and lead, indicating that elevated soil levels directly influence rice contamination. However, Bioaccumulation Factor values remained < 1, suggesting that local rice cultivars restrict metal uptake. Pollution Index values > 1 indicated contamination from arsenic (1.3) and lead (1.0) in both soil and rice, identifying them as key pollutants. Health Risk Index values > 1 for arsenic further imply potential health risks from rice consumption, particularly when 500 g of rice is consumed per day. These findings highlight rising environmental and health concerns linked to heavy metal accumulation in the post-pandemic period. We stress the need for targeted mitigation strategies, including phytoremediation, regulation of pollutant inputs, and regular environmental monitoring.