Continental-scale variation in chloride/bromide ratios of wet deposition

M. A. Short*, P. de Caritat, D. C. McPhail

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    13 Citations (Scopus)

    Abstract

    Chlorine and bromine play crucial roles in atmospheric element cycles and are important environmental tracers in catchment investigations, so understanding their distribution at the Earth's near-surface is imperative for deciphering their behaviour. This study presents the first continental-scale analysis of Cl and Br concentrations of wet deposition, based on six and half years of weekly samples collected across North America. A recently developed imputation algorithm was applied to estimate the high proportion of censored Br values, as well as the other eight analytes, based on the multivariate relationships of nine analytes. The results are consistent with previous studies that have found that the concentrations of these two ions in wet deposition, and the Cl/Br ratios of wet deposition decrease with distance inland. Close to the coast, Cl/Br ratios of wet deposition are similar to the ratio found in seawater (~ 288 by mass), rapidly decrease to approximately a third of the seawater ratio at ~ 200 km inland, and then decrease at a much lesser rate to reach mass-ratios of 20 to 10 at ~ 1500 km inland, following a logarithmic regression. The Niagara Falls and the Great Salt Lake are identified as localised sources of atmospheric solutes based on elevated Cl/Br ratios of wet deposition at proximal sites. Our observations provide further confidence in the findings presented in previous studies that have shown that Cl/Br ratios systematically decrease with increasing distance from the coast, despite the potential confounding impact of other processes, such as weather patterns, chemical behaviour and anthropogenic activity. Our results provide improved estimates of Cl/Br ratios of wet deposition source water in the absence of site-specific data.

    Original languageEnglish
    Pages (from-to)1533-1543
    Number of pages11
    JournalScience of the Total Environment
    Volume574
    DOIs
    Publication statusPublished - 1 Jan 2017

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