The Climate Program Office’s Atmospheric Chemistry, Carbon Cycle and Climate (AC4) Program funded new research to find a better way to track sulfur and nitrogen compound emissions (SOx and NOx) in the United States. These pollutants are ultimately taken out of the atmosphere by rain (wet deposition) or absorbed by land and plants (dry deposition). Doctoral candidate Ishir Dutta and AC4-funded scientist Colette Heald of the Massachusetts Institute of Technology explored several long-running deposition datasets to see if they can help understand complex trends in SOx and NOx. They used a dataset with direct measurements of wet deposition, from a network across the country that detects precipitation with sampling bags and rain gauges. Next, they analyzed a dataset that indirectly estimates dry deposition from ambient gas and particle phase concentration measurements. The results, published in JGR Atmospheres, show that records estimating dry deposition match local human-caused emissions, while wet deposition observations track well with regional emissions trends, including human-made, natural, and imported pollutants from nearby countries. The authors conclude that these deposition monitoring systems are useful for tracking SOx and NOx trends, which will be critical for verifying the effectiveness of air quality policies. AC4 supported this project to improve the understanding of long-term trends in our atmospheric chemistry.
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