Investigation into sampling and determination method of metals in rainwater: A preliminary results at Ho Chi Minh City

Abstract

The bulk deposition (both dry and wet) is an important process that removes metal pollution from the air. The rainwater sampling is a commonly employed method for the composition estimation. While extensive global research exists on metal deposition, there remains a notable lack of attention to this field in Southeast Asia as well as in Vietnam. The paper presented the designment a sampling model to determine metal concentrations and to conduct an initial analysis of the concentrations of six metals (Pb, Zn, As, Ni, Cu, Cr) in rainwater samples obtained at an urban environment of Ho Chi Minh City (HCMC). The metal concentrations were determined by the inductivelycoupled mass spectrometry (ICPMS) technique. The observation involved assessments of rainwater collection devices, evaluations of evaporation dynamics and comparisons with theoretical precipitation. The effectiveness and reliability of the sampling equipment in collecting rainwater samples facilitated the metal content analysis. An observations over a fivemonth period (January to June 2023) showed the presence of all six mentioned metals, with average concentrations decreasing in the order of Zn (46.9 µg/L), Ni (4.53 µg/L), Cu (4.34 µg/L), Pb (2.46 µg/L), Cr (1.33 µg/L), As (0.20 µg/L). The rainout effect plays an important role in determining metal concentrations in rainwater samples. A significant correlations found among these metals showed the substantial contribution of the anthropogenic pollution sources to the rainwater. The proposed sampling equipment suitably proved for conducting wet deposition studies, shedding light on metal presence in the atmosphere in HCMC. This would be a preliminary information about the concentration of the six metals in rainwater collected at an urban area of HCMC.