Appraisal of trace metals toxicity and human health risk using a novel approach in produced water of four gas fields, Bangladesh.

Abstract

The current research was conducted in the Sylhet gas-fields area of Bangladesh to evaluate the toxicity of trace metals (TMs) and associated health risks. Gas well-produced water, gas field discharge water, and drinking water surrounding the gas fields were collected for analysis. This study analyzed both carcinogenic and noncarcinogenic TMs such as Cr, As, Co, Cd, Fe, Ni, Mn, Zn, and Pb, as well as physical parameters pH and EC in the collected samples. The Fe and EC concentrations in produced and discharged water samples were found to be incredibly high. The average concentrations of TMs in produced water samples during the summer and rainy season were found to be: Fe > Mn > Zn > Ni > Co > Cu > Cr > Pb > As > Cd. The observed metal concentration in discharge water was higher during the summer than rainy season. Most samples met national and international standards for trace elements, while a few samples exceeded the threshold value. The Heavy Metal Evaluation Index (HMEI) results indicate that the majority of produced water is highly polluted, while discharge and drinking water are moderately to lowly polluted. The Environmental Pollution Index (EPI) indicates environmental pollution for some produced water samples, while it indicates a moderate to low risk for discharge and drinking water samples. The source allocation of heavy metals (HMs) was determined using positive matrix factorization. However, all water samples have an ecological risk index of less than 150, indicating lower risk. Furthermore, the Heavy Metals Toxicity Load (HMTL) was found to be below the allowable toxicity load for all water samples, indicating minimal contamination in the studied water. The non-cancer hazard score (HI) of the studied HMs is greater for children and females than for males. The cancer risk from Ni is a concern, while the cancer risk from Cd and Cr is also a matter of concern.