Risk assessment of heavy metals in the major surface water system of Nepal with potential remediation technologies

Abstract

This paper presents an analytical risk assessment of heavy metals (HMs) in twenty-three rivers and two typical lakes across five different provinces of Nepal. The study examines their effects on humans of varying age groups and ecological systems using different indexes such as Hazard Index (HI), Cancer Index (CI), and Hazard Quotient (HQ). The human health risk assessment reveals that female children are the most vulnerable to heavy metal risks, followed by male children, female adults, and male adults. Notably, Co, Pb, Cd, As, Cr, and Cu present substantially high non-carcinogenic health risks for all adults and children with HI values ranging from 1 to more than 100. However, this risk is confined to only children (both male and female) for the metals Mn and Ni. HMs such as Cr, Ni, As, Cd, and Pb have a very high carcinogenic risk in some rivers for all adults and children (CI > 1.00E-3). Concerning ecological risk, the HQ values are found to be significantly above the permissible limit with the order Cu > Cd > Pb > Fe > Zn > Co > Ni > Mn. Furthermore, the integration of various treatment technologies would enhance effectiveness in eliminating HMs from polluted river water, ensuring that the water becomes suitable for irrigation and other purposes. The heavy metals identified as priority controlling factors with potential remediation technologies can provide valuable insights for policymakers in making informed decisions concerning the safety of human health and the ecological system.

Keywords

• Heavy metal
• Non-carcinogenic risk
• Carcinogenic risk
• Ecological risk
• Surface water system
• Treatment technologies