Abstract
The study involved analysis of rainwater samples at four sites on Upolu Island, Samoa from November 2019 to April 2020. A total of 48 rainwater samples were analysed in order to determine the major cations (Na+, Mg2+, Ca2+, K+) and anions (Cl-, , ) in wet precipitation from the four sites. The average pH of the rainwater was 6.89, perhaps due to neutralization. Only 50% of the rain samples had a pH above 5.6. This shows strong inputs of alkaline species to rainwater samples in some sites. The average pH of samples higher than 5.6 is due to high loadings of sodium ions. The rainwater samples are dominated by Na+, Ca2+, Mg2+, Cl- and . The principal cations and anions, in decreasing order, are Na+ > Mg2+ > Ca2+ > K+ and Cl- > > . The correlation study and the comparison of major ion composition with other sites revealed that rainwater ion composition is strongly influenced by marine sources rather than anthropogenic and terrestrial sources.
Highlights
IntroductionChemical species in the atmosphere may be deposited onto the Earth’s surface in two ways: 1) wet deposition (water-based particles in liquid or solid form—rain, snow, ice) and 2) dry deposition (dry species including gases such as sulfur dioxide and solid particles (aerosols)
Chemical species in the atmosphere may be deposited onto the Earth’s surface in two ways: 1) wet deposition and 2) dry deposition
A total of 48 rainwater samples were analysed in order to determine the major cations (Na+, Mg2+, Ca2+, K+) and anions (Cl−, SO24−, NO3− ) in wet precipitation from the four sites
Summary
Chemical species in the atmosphere may be deposited onto the Earth’s surface in two ways: 1) wet deposition (water-based particles in liquid or solid form—rain, snow, ice) and 2) dry deposition (dry species including gases such as sulfur dioxide and solid particles (aerosols). The primary anthropogenic polluting emissions gases are SO2 (sulfur dioxide) and NOx (nitrogen oxides) These pollutants may be dissolved and transported by the rainwater to ground. In India several studies have generally highlighted the alkaline nature of rainwater due to soil derived particles in the atmosphere and chemical composition of rainwater has been carried out at urban and rural locations [4]. [5] [6] reported that chemical characteristics of rainwater in urban areas are contributed to the local pollution sources, whereas in rural areas, it indicates the degree of impact of anthropogenic as well as natural sources. The result from this study will provide more insight of the level of atmospheric pollution in rainwater through the determination of chemical composition of rainwater in Samoa in ten years
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