Assessment of coastal groundwater quality, pollution sources, and fitness-for-purpose in Tien Giang province of the Vietnamese Mekong Delta

This study evaluates the current status of groundwater quality and its suitability for domestic, irrigation, and industrial applications within Tien Giang province, Vietnam, located in the Mekong Delta area. Groundwater samples were collected from 31 locations during March, June, and September in 2020 and 2022, and analyzed for key physico-chemical and microbial parameters. Water quality analysis was conducted by direct comparison with national water quality standards (QCVN 09-MT:2015/BTNMT for groundwater quality; QCVN 01–1:2018/BYT for domestic water quality) and statistical analysis using the Integrated Water Quality Index (IWQI), Principal Component Analysis (PCA), and Absolute Principal Component Score-Multiple Linear Regression (APCS-MLR). Results revealed that while most parameters met general groundwater standards according to QCVN 09-MT:2015/BTNMT, and IWQI classified samples as good and excellent, indicating suitability for irrigation. However, a pollution risk was observed for heavy metal concentrations, which suggests water treatment before consumption. Due to stricter domestic water regulations according to QCVN 01–1:2018/BYT, many groundwater samples were found unsuitable for consumption: Fe (65.6% of total samples) and Cl − (20.4%) were problematic in 2020 while As (29.0%), Fe (22.6%), and Mn (14.0%) exceeded the limits in 2022. For industrial use, 12.9–22.6% of the locations showed corrosion potential according to pH and Cl − levels. Spatial analysis showed poorer groundwater quality in central and eastern regions. PCA/APCS-MLR identified mineralization/ion exchange and agricultural impacts as the primary determinants for the groundwater quality. These findings highlight the need for targeted groundwater treatment and management in Tien Giang to ensure the safety for both domestic and industrial water supply.