Sensitivity of Organic Aerosol Concentrations and Forcing to Anthropogenic EmissionsEPA Grant Number: R835405
Title: Sensitivity of Organic Aerosol Concentrations and Forcing to Anthropogenic Emissions
Investigators: Pandis, Spyros N. , Donahue, Neil
Institution: Carnegie Mellon University
EPA Project Officer: Hunt, Sherri
Project Period: April 1, 2013 through March 31, 2016
Project Amount: $399,998
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
Despite its importance for human health and climate change organic aerosol (OA) remains one of the least understood aspects of atmospheric chemistry. We propose to continue the development of an innovative new framework for the description of OA in chemical transport and climate models that will be able to overcome the challenges posed by the chemical complexity of OA while capturing its essential features.
The objectives of the proposed project are: (i) The experimental investigation of the mixing of biogenic and anthropogenic components. (ii) The quantification of the effects of NOx and SO2 on the formation of biogenic SOA. (iii) The measurement of the OA formed per unit of biogenic and anthropogenic SOA precursor added to typical air masses. (iv) The development of parameterizations of the above processes in the OA volatility-oxygen content coordinate system. (v) The evaluation of this new module in the regional chemical transport model PMCAMx against some of the best available (or soon to be available) datasets (SOAS and SENEX-2013 in the US and EUCAARI and PEGASOS in Europe). (vi) The use of PMCAMx to quantify the response of the biogenic OA and its climatic effects (direct effect and also cloud condensation nuclei concentrations) in the Eastern US for different scenarios of anthropogenic emission changes.
The proposed work involves a combination of laboratory measurements, novel field “atmospheric perturbation experiments”, OA model development, and modelling in urban and regional scales. The laboratory work will combine a multiple-residence time thermodenuder (TD) including a dilution system with a high-resolution Aerosol Mass Spectrometer, a Scanning Mobility Particle Spectrometer, a Cloud Condensation Nuclei Counter and a Hygroscopic Tandem Differential Mobility Analyzer (all placed after the TD) to investigate the mixing of organic aerosol from anthropogenic and biogenic sources, the effect of NOx on the formation of biogenic SOA. Field work will involve perturbation (addition of known concentrations of isotopically labeled biogenic and anthropogenic VOCs and SO2) of ambient air inside a chamber and quantification of the change of the OA levels. The quantification will rely on the difference of the OA levels between the “perturbed” chamber and a second similar chamber filled with just ambient air. The results of the laboratory and field perturbation experiments will be used for the continued development of parameterizations for the description of the biogenic SOA formation, its interactions with anthropogenic OA, and SO2 in the volatility-oxygen content coordinate system (2D-Volatility Basis Set). The resulting modules will be added to PMCAMx and will be evaluated against the best available datasets.
The resulting OA module that could be used in different CTMs together with the insights about the sensitivity of the biogenic (but also anthropogenic) SOA to changes in emissions of anthropogenic pollutants will be the major outcomes of the proposed study.