Positive Impact of COVID-19 Lockdown on Heavy Metals in Groundwater and Possible Health Risks for Human beings in an Industrialized City of South India

Abstract In this investigation, positive impact of COVID-19 lockdown on heavy metals concentration and biological parameters in the groundwater samples of Coimbatore city of South India. The groundwater samples (n = 15) were obtained from shallow-open wells before lockdown (24–25 January 2020) and after lockdown (2–3 June 2020) periods. These samples were analysed for heavy metals (Fe, Mn, Ni, Cr and Pb) and biological parameters (E. coli, Fecal coliforms, Fecal streptococci and Total coliforms). Fe concentration was within the permissible limit but, the concentrations of Mn, Ni, Cr and Pb were above the allowable limits for drinking uses as per the WHO. However, after lockdown the number of samples crossing the cutoff limit had considerably decreased (Mn: 2 to 0; Ni: 13 to 10; Cr: 7 to 5; Pb: 13 to 8). The spatial distribution of heavy metal pollution index (HPI) revealed that 176.75 km2 (67.4%) and 85.35 km2 (32.6 %) areas fell under unsuitable and very poor categories, respectively, during pre-lockdown period, whereas 138.23 km2 (52.6 %), 118.98 km2 (45.3%) and 4.89 km2 (2.1%) areas fell under very poor, poor and good categories, respectively, during post-lockdown period. Similarly, Total coliform, Fecal coliform and E. coli had decreased distinctly due to the pandemic lockdown. Therefore, shutdown of small and large-scale industries during the lockdown period had improved the groundwater quality. Health risk assessment showed that 93%, 87% and 80% of pre-lockdown samples, and 87%, 80% and 73% of post-lockdown samples possessed non-carcinogenic risks (HI > 1) for children, female and male categories, respectively.