Persistent organic pollutants in global surface soils: Distributions and fractionations

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Ecotoxicology

Background:

• Persistent organic pollutants (POPs) are chemicals that remain intact in the environment for long periods.
• Understanding POPs distribution and fractionation is crucial for assessing their transport to remote areas like the Arctic.

Purpose of the Study:

• To review progress in understanding POPs distribution and fractionation.
• To analyze intermedia processes governing POPs transfer between air and soil.
• To develop quantitative methods for studying POPs distribution and fractionation.

Main Methods:

• Review of existing literature on POPs distribution and fractionation.
• Analysis of four intermedia processes: dry and wet deposition of gaseous and particulate POPs.
• Development of equations for quantitative analysis of primary and secondary POPs distribution and fractionation.
• Use of a one-dimensional transport model to simulate POPs transport.

Main Results:

• POPs transfer from air to soil depends on molecular weight: low molecular weight (LMW) POPs via gas diffusion and particle deposition, high molecular weight (HMW) POPs mainly via particle deposition.
• HMW-POPs are typically trapped near the source, while LMW-POPs undergo long-range atmospheric transport.
• Primary fractionation is temperature-independent, while secondary fractionation occurs along temperature gradients.

Conclusions:

• Temperature gradients drive secondary POPs distribution and fractionation, not primary fractionation.
• Decreasing temperatures with latitude do not primarily cause POPs fractionation into polar ecosystems.
• Cold climates and polar regions facilitate longer-term POPs accumulation through processes like polar cold trapping.