Constraining Atmospheric Selenium Emissions Using Observations, Global Modeling, and Bayesian Inference.

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Biogeochemistry

Background:

• Selenium (Se) is an essential dietary element for humans and animals.
• Atmospheric deposition is a significant source of soil selenium.
• Global atmospheric selenium flux estimates are currently highly uncertain.

Purpose of the Study:

• To reduce uncertainties in global atmospheric selenium flux estimates.
• To determine probability distributions of global selenium emissions from major sources.
• To improve the understanding of the global selenium cycle.

Main Methods:

• Utilized a global model of atmospheric selenium cycling.
• Incorporated a database of over 600 sites with measured aerosol selenium.
• Applied Bayesian inference techniques to optimize emission parameters.

Main Results:

• Annual global atmospheric selenium emissions estimated between 29 and 36 Gg, doubling previous figures.
• Model demonstrated good agreement with aerosol (R² = 0.66) and deposition measurements (0.59, 0.57).
• Observed and modeled decline in North American selenium over two decades due to policy changes.

Conclusions:

• The ocean acts as a net atmospheric selenium sink, transferring approximately 7 Gg yr⁻¹ from land.
• Constrained selenium emission estimates represent a significant advancement in understanding the global selenium cycle.
• Findings provide a more accurate basis for assessing selenium's role in ecosystems and human health.