Lane Timothy E, Donahue Neil M, Pandis Spyros N
Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Environ Sci Technol. 2008 Aug 15;42(16):6022-7. doi: 10.1021/es703225a.
The secondary organic aerosol (SOA) module in PMCAMx, a three-dimensional chemical transport model, has been updated to incorporate NOx-dependent SOA yields. Under low-NOx conditions, the RO2 radicals react with other peroxy radicals to form a distribution of products with lower volatilities, resulting in higher SOA yields. At high-NOx conditions, the SOA yields are lower because aldehydes, ketones, and nitrates dominate the product distribution. Based on recent laboratory smog chamber experiments, high-NOx SOA parametrizations were created using the volatility basis-set approach.The organic aerosol (OA) concentrations in the Eastern US are simulated for a summer episode, and are compared to the available ambient measurements. Changes in NOx levels result in changes of both the oxidants (ozone, OH radical, etc.) and the SOA yields during the oxidation of the corresponding organic vapors. The NOx dependent SOA parametrization predicts a maximum average SOA concentration of 5.2 microg m(-3) and a domain average concentration of 0.6 microg m(-3). As the NOx emissions are reduced by 25%, the domain average SOA concentration does not significantly change, but the response is quite variable spatially. However, the predicted average SOA concentrations increase in northern US cities by around 3% but decrease in the rural southeast US by approximately 5%. A decrease of the average biogenic SOA by roughly 0.5 microg m(-3) is predicted for the southeast US for a 50% reduction in NOx emissions.
三维化学传输模型PMCAMx中的二次有机气溶胶（SOA）模块已更新，以纳入与氮氧化物相关的SOA产率。在低氮氧化物条件下，RO2自由基与其他过氧自由基反应，形成挥发性较低的产物分布，从而导致较高的SOA产率。在高氮氧化物条件下，SOA产率较低，因为醛、酮和硝酸盐主导了产物分布。基于最近的实验室烟雾箱实验，使用挥发性基组方法创建了高氮氧化物SOA参数化。对美国东部夏季某一时期的有机气溶胶（OA）浓度进行了模拟，并与现有的环境测量数据进行了比较。氮氧化物水平的变化会导致相应有机蒸汽氧化过程中氧化剂（臭氧、OH自由基等）和SOA产率的变化。与氮氧化物相关的SOA参数化预测，最大平均SOA浓度为5.2微克/立方米，区域平均浓度为0.6微克/立方米。当氮氧化物排放量减少25%时，区域平均SOA浓度没有显著变化，但空间响应变化很大。然而，预测美国北部城市的平均SOA浓度增加约3%，而美国东南部农村地区则下降约5%。预计美国东南部地区氮氧化物排放量减少50%时，平均生物源SOA将减少约0.5微克/立方米。
