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ACROSS Briefly Described

Humans have recognized for a long time that their air can become contaminated through natural and non-natural events. The problem became particularly apparent as people moved into large cities where the high population densities exacerbated the pollution associated with home heating and industry. Awareness became particularly acute when thousands of people died during severe episodes.

In recent decades, significant progress has been made in understanding the causes and impacts of urban air pollution, generally leading to improved air quality through enhanced knowledge and regulatory action. While significant numbers of people still die prematurely each year from air pollution, progress continues to be made. Scientific investigation has exposed the processes by which primary pollutants, such as oxides of nitrogen and volatile organic compounds, are processed in the atmosphere, leading to their oxidation and ultimate removal, while at the same time producing secondary species such as ozone and organic aerosols. Both primary and secondary species can be toxic for humans, animals and plants.

Recent research has uncovered the complex chemistry of natural organic compounds released from trees and other plants. Because of the chemical structures of these compounds, they react differently than organic substances typically found in urban environments. At present, it is not clear if the mixing of biogenic organic compounds with urban makes air quality better or worse. In the end, the answer may be quite complex. The ACROSS (Atmospheric ChemistRy Of the Suburban foreSt) project focuses on scientific research to understand the detailed chemistry and physics of urban air mixed with biogenic emissions with the goals to increase detailed understanding of the chemical processes and to use this knowledge to improve the performance of air quality models. Enhanced knowledge and improved models will allow society to develop better strategies to improve air quality and save lives.

The central component of ACROSS is a comprehensive summertime field study with many instruments for the measurement of primary and secondary constituents. Measurements will be made from research aircraft, a tower located in a forest, tethered balloons and/or drones, and mobile platforms. Observations from the field study will be analyzed in a variety of ways involving statistical approaches and comparisons with different types of numerical models. The results of the campaign will be widely disseminated through presentations and peer-reviewed publications. Significant broader impacts are expected including training of students, public outreach, and providing useful information to policymakers. The ACROSS observations are expected to provide a unique dataset that will improve understanding of fundamental processes and that can be used to improve model representations of processes that are operative in these environments.