Atmospheric Chemistry of Methylated Selenium Compounds and Physicochemical Properties of the Resulting Aerosols

该项目涉及大气硒（Se）的归宿和分布的研究。环境室将用于量化含硒有机化合物形成的二次有机气溶胶，并确定使用一套在线和离线仪器产生的主要气体和气溶胶产品。本项目的研究结果将有助于了解长期暴露于有机硒化合物，特别是在富含硒的土壤和沉积物的地区，如美国西部的农业山谷，可能会对公众健康产生负面影响。将使用各种氧化剂在不同的氮氧化物水平下对几种甲基化硒化合物的气相和水相氧化进行系统研究（OH，NO3和O3）和氧化时间尺度。本研究的目的是开发一个更好的理解二次气溶胶形成的气相和水相氧化选定的甲基硒物种和提高知识的化学和微物理特性的气溶胶控制对人类健康和环境化学的影响。这些假说包括：（1）有机硒化合物的光氧化和硝酸根氧化导致了大量的二次气溶胶生成，生成量与NOx有关，硝酸根氧化途径的生成量与高NOx条件下的光氧化途径相似;（2）长时间氧化导致产品的显著碎裂，因此，二次气溶胶质量减少;和（3）甲基化Se中间氧化产物在低NOx条件下的水相氧化导致形成含Se的次级气溶胶物质和更高浓度的氢过氧化物，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的知识价值进行评估，被认为值得支持。影响审查标准。

This project involves the study of the fate and distribution of atmospheric selenium (Se). An environmental chamber will be used to quantify the formation of secondary organic aerosol from selenium (Se)-containing organic compounds and determine the major gas and aerosol products generated using a suite of online and offline instrumentation. The results obtained from this project will improve the understanding of how long-term exposure to organic Se compounds, especially in areas with Se-rich soils and sediments such as agricultural valleys in the western US, might negatively influence public health.Systematic studies of gas and aqueous phase oxidation of several methylated Se compounds will be conducted under variable nitrogen oxide levels using various oxidants (OH, NO3 and O3) and oxidation time scales. The objectives of this research are to develop an improved understanding of secondary aerosol formation from gas and aqueous phase oxidation of selected methylated Se species and improve knowledge about the chemical and microphysical properties of the resulting aerosols that control the impacts on human health and environmental chemistry. The hypotheses include the following: (1) Photooxidation and nitrate radical oxidation of the selected organoselenium compounds lead to significant secondary aerosol formation and the formation yields are NOx-dependent; The yield of the nitrate oxidation pathway is expected to be like that of photooxidation in the presence of high NOx; (2) Long oxidation times lead to significant fragmentation of the products and, therefore, a reduction in secondary aerosol mass; and (3) Aqueous phase oxidation of methylated Se intermediate oxidation products under low NOx conditions leads to formation of Se-containing secondary aerosol species and a higher concentration of hydroperoxides, which results in the increased production of reactive oxygen species.This effort involves the training and mentoring of several graduate and undergraduate students and includes outreach and educational activities at local high schools and middle schools.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.