Human activity dramatically changes the chemosphere through contribution of synthetic compounds as well as unnatural mobilization processes such as industrial scale hydrocarbon extraction, combustion and agriculture. Millions of man-made chemicals have been synthesized, of
Scavenging of gas-
and aerosol-phase organic pollutants by rain
is an efficient wet deposition mechanism of organic pollutants. However,
whereas snow has been identified as a key amplification mechanism
of fugacities in cold environments, rain has received less attention
in terms of amplification of organic pollutants. In this work, we
provide new measurements of concentrations of perfluoroalkyl substances
(PFAS), organophosphate esters (OPEs), and polycyclic aromatic hydrocarbons
(PAHs) in rain from Antarctica, showing high scavenging ratios. Furthermore,
a meta-analysis of previously published concentrations in air and
rain was performed, with 46 works covering different climatic regions
and a wide range of chemical classes, including PFAS, OPEs, PAHs,
polychlorinated biphenyls and organochlorine compounds, polybromodiphenyl
ethers, and dioxins. The rain–aerosol (K
RP) and rain–gas (K
RG) partition
constants averaged 105.5 and 104.1, respectively,
but showed large variability. The high field-derived values of K
RG are consistent with adsorption onto the raindrops
as a scavenging mechanism, in addition to gas–water absorption.
The amplification of fugacities by rain deposition was up to 3 orders
of magnitude for all chemical classes and was comparable to that due
to snow. The amplification of concentrations and fugacities by rain
underscores its relevance, explaining the occurrence of organic pollutants
in environments across different climatic regions.
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