Abstract
Air pollution resulted from fossil fuel burning has been an environmental issue in developing countries in Asia. Sulfur-bearing compounds, in particular, are species that are regulated and monitored routinely. To assess how the species affect at local and global scales, regional background level has to be defined. Here, we report analysis of sulfur isotopes in atmospheric sulfate, the oxidation end product of sulfur species, in particulate phase collected at the Lulin observatory located at 2862 m above mean sea level in 2010. The averaged sulfate concentration for 44 selected samples is 2.7 ± 2.3 (1-σ standard deviation) μg m−3, and the averaged δ34S is 2.2 ± 1.6‰, with respect to the international standard Vienna Canyon Diablo Troilite. Regardless of the origins of air masses, no noticeable difference between the low-altitude Pacific and high-altitude free troposphere sulfate aerosols is observed. Also, no identifiable seasonal cycle in seen. Correlation analysis with respect to coal burning tracers such as lead and oil industry tracers such as vanadium shows sulfate concentration is in better correlation with vanadium (R2 = 0.86, p-value < 0.001) than with lead (R2 = 0.45, p-value < 0.001) but no statistically significant correlation is found in δ34S with any of physical quantities measured. We suggest the sulfate collected at Lulin can best represent the regional background level in the Western Pacific, a quantity that is needed in order to quantitatively assess the budget of sulfur in local to country scales.
Highlights
Air pollution resulted from fossil fuel burning has been an environmental issue in developing countries in Asia
Correlation analysis with respect to coal burning tracers such as lead and oil industry tracers such as vanadium shows sulfate concentration is in better correlation with vanadium (R2 = 0.86, p-value < 0.001) than with lead (R2 = 0.45, p-value < 0.001) but no statistically significant correlation is found in δ34S with any of physical quantities measured
Strong temporal variability in winter and spring is closely associated with northeast Asia monsoon that significantly modifies the trajectories of air masses arriving at the sampling location
Summary
(The aforementioned natural sources such as volcanic emission from Eyjafjallajökull eruption as a major source of sulfate at LLN were not supported, because of good correlation between sulfate concentration and man-made trace metal levels such as vanadium and absence of correlation between δ34S and the other variables measured and analyzed in this work. Tight correlation of [nss-SO42−] with [NO3−] (R2 = 0.70) or [NH4+] (R2 = 0.83) suggests human activities play a major role in the production of sulfate aerosols in the atmosphere; the correlation with nitrate is expected as a result of high temperature combustion and the correlation with ammonium is via NH3 slipped from power plants.
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