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

Abstract

The objective of this study is to assess the toxicity of trace metals (TMs) and associated environmental, ecological and health risks in the gas fields located in the Sylhet region of Bangladesh. Gas well-produced water, gas field discharge water, and drinking water surrounding the gas fields were collected for analysis. This study analyzed 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 using various instruments. The TMs were measured using Atomic Absorption Spectrometer (AAS), Flame AAS and physical parameters were evaluated using portable water multiparameter. The Fe and EC concentrations in produced and discharged water samples were incredibly high. The average concentrations of TMs in produced water samples during the summer and rainy seasons 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 in the 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 most produced water is highly polluted, while discharge and drinking water are moderate to lightly 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 of trace metals (TMs) 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 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 more significant for children and females than males. The cancer risk from Ni is a concern, while the cancer risk from Cd and Cr is also a matter of concern. In the end, policymakers can utilize this study's findings to monitor, and control produced water contamination.