Major ions, trace elements and evidence of groundwater contamination in Hanoi, Vietnam

Abstract Groundwater contamination is a critical issue in Hanoi because it affects the water supply and treatment of crowded city. This study aimed to explore groundwater quality across whole area city identify potential sources. 206 samples were collected Holocene Pleistocene aquifers during two consecutive seasons (rainy 2015 dry 2016) assess understand which elements can be used as tracers for future monitoring. As result, spatial distributions major ions (Na, K, Ca, Mg, Cl − , SO 4 2− ) some selected (As, Li, Sr, Ba, Mn, Fe, Al, B, Br, total nitrogen (TN), P) obtained. Distributions contaminants varied not only on depth regions (aquifers) but also season-wise. In upper aquifer, As, Br TN, P concentrations significantly higher than common range. south city, we found elevated Na, aquifer. Additionally, such Fe did follow clear pattern. Their seem predominantly influenced by geological processes controlling area's hydro-geochemical environment. However, high P, particularly central Hanoi, supported idea from surface. study's results might help managers foster sustainable resource strategies.