Anthropogenic influence on biogenic VOC oxidation: the role of NOx pollution in secondary organic aerosol production in the Southeast U.S.EPA Grant Number: R835399
Title: Anthropogenic influence on biogenic VOC oxidation: the role of NOx pollution in secondary organic aerosol production in the Southeast U.S.
Investigators: Fry, Juliane L
Institution: Reed College
EPA Project Officer: Hunt, Sherri
Project Period: April 1, 2013 through March 31, 2016
Project Amount: $299,995
RFA: Anthropogenic Influences on Organic Aerosol Formation and Regional Climate Implications (2012) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Global Climate Change , Climate Change , Air
Nitrogen oxides, through their interactions with volatile orgaruc compounds (VOCs), NH3, OH, and other gas-phase species, exert important controls on the lifetime and fate of atmospheric VOCs and the formation of secondary aerosol. During the rught, the N03 radical is an important oxidant, reacting rapidly with unsaturated VOCs, many of which are biogeruc in origin (BVOC), to produce organic nitrates and other oxidized VOCs, some of which lead to the formation of secondary organic aerosol (SOA). We hypothesize that this N03-BVOC reaction pathway will be important at and above the SOAS campaign ground site, which is situated in a relatively polluted region where BVOC comprise essentially all ofVOC reactivity toward NOy N03-BVOC SOA formation has been the subject of a few experiments in large environmental chambers; however, quantitative demonstration of these processes in the ambient atmosphere is practically non-existent. Field verification of the competitive role of inorganic nitrate chemistry also remains incomplete. Our objective is to measure the reactive N budget and fate of oxidized nitrogen in and above the forest canopy at the SOAS flux tower in Centreville, AL, a site with large BVOC emissions that are representative of those across the southeastern U.S.
At the Southern Oxidant and Aerosol Study (SOAS), we propose to measure oxides of nitrogen (NOv): N03 radical, N20 5, and N02, (using cavity ringdown and chemiluminescence) at several heights, coordinated with aircraft vertical profile measurements of the same species (SENEX) and with other groups' measurements of VOCs, RON02, ROON02, and HN03, to get a complete picture of the NOY budget in and above the forest canopy, with special focus on the fate of the reactive N03 radical. We will also measure gas- and aerosol-phase HN03, NH3, NH4 + and N03. using ion chromatography. We will assess maximum potential aerosol mass (PAM) using a flow reactor to which we add a known amount of N03. After analysis of the field data, we will conduct a chamber experiment collaboration in Boulder simulating ambient and N03 PAM chemistry, to verify field -observed relationships and assess the predictive capacity of the PAM flow reactor.
This proposal targets EPA STAR call "Anthropogeruc Influences on Orgaruc Aerosol Formation and Regional Climate Implications," particularly addressing the stated goals of achieving improvements in understanding (a) the influence of anthropogeruc pollution on SOA formation from BVOCs, and (b) role of NOx in the oxidation of isoprene and the formation of SO A. N03- initiated chemistry is either not included or treated in a highly simplified form in air quality models, impeding decision-makers' ability to accurately predict the downstream effects of e.g. NO, emissions reductions in forested regions. The proposed project seeks to improve this predictive ability with consequential improvements in risk assessment related to emissions policies.