Rain Amplification of Persistent Organic Pollutants.

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Pollutant Transport

Background:

• Rain is an efficient wet deposition mechanism for organic pollutants.
• Snow amplifies pollutant fugacities in cold environments, but rain's role is less studied.
• Organic pollutants include perfluoroalkyl substances (PFAS), organophosphate esters (OPEs), and polycyclic aromatic hydrocarbons (PAHs).

Purpose of the Study:

• To investigate the role of rain in scavenging and amplifying organic pollutants.
• To compare the amplification effects of rain and snow on pollutant fugacities.
• To analyze pollutant concentrations in Antarctic rain and perform a meta-analysis of global data.

Main Methods:

• New measurements of PFAS, OPEs, and PAHs in Antarctic rain.
• Meta-analysis of 46 published studies on air and rain concentrations of various organic pollutants.
• Calculation of rain-aerosol (KRP) and rain-gas (KRG) partition constants.

Main Results:

• High scavenging ratios observed for pollutants in Antarctic rain.
• Field-derived KRG values indicate adsorption onto raindrops is a key scavenging mechanism.
• Rain deposition amplified pollutant fugacities by up to 3 orders of magnitude, comparable to snow.
• Significant variability in KRP and KRG values across studies and chemical classes.

Conclusions:

• Rain is a significant factor in the global distribution and amplification of organic pollutants.
• The findings highlight the importance of considering rain's role in wet deposition and pollutant transport.
• Organic pollutants are found in diverse climatic regions due to mechanisms like rain amplification.