CAREER: Molecular Mechanism of Atmospheric Mercury through Speciation-Resolved Experiments

这个CAREER项目的重点是更好地了解大气中的汞。汞是一种由化石燃料燃烧和垃圾焚烧释放的剧毒污染物，主要以气态单质汞（GEM）的形式释放。GEM参与可能导致汞向海洋转移的远程转运。这个项目将研究大气中汞反应的动力学。该项目提高了对汞化学的认识，这对评估汞对环境的影响至关重要。本研究的科学目标是：(1)阐明溴化汞（HgBr）气相反应的动力学和机理，评价GEM的寿命和气态氧化汞（GOM）的分子形态；(2)研究GOM在表面的非均匀吸收，以提高对形成颗粒结合汞的过程的理解；(3)研究GOM的离子-分子反应，确定可用于化学电离质谱（CIMS）直接检测大气中GOM的试剂离子。激发这项研究的问题包括：(a)哪些大气化学物质负责将HgBr转化为稳定的气相产物？(b)这些产品的化学性质是什么？(c)相关反应途径的速率系数是多少？(d)哪一种气相产物能与大气颗粒物有效结合？(e)这些气相和颗粒结合产物能否直接检测和定量？

This CAREER project is focused on developing a better understanding of atmospheric mercury. Mercury is a highly toxic pollutant released by fossil fuel combustion and waste incineration, primarily in the form of gaseous elemental mercury (GEM). GEM is involved in long-range transport that can result in the transfer of mercury to the oceans. This project will investigate the kinetics of mercury reactions in the atmosphere. The improved knowledge of mercury chemistry obtained by this project will be critical for assessing the environmental impacts of mercury.The science objectives of the proposed research are to: (1) Elucidate the kinetics and mechanism of gas-phase reactions of mercury bromide (HgBr) to evaluate the lifetime of GEM and the molecular speciation of gaseous oxidized mercury (GOM); (2) Investigate the heterogeneous uptake of GOM on surfaces to improve understanding of the processes that form particle-bound mercury; and (3) Investigate ion-molecule reactions of GOM to identify reagent ions that can be utilized for direct detection of GOM in the atmosphere by chemical ionization mass spectrometry (CIMS). Questions that motivate this research include: (a) what atmospheric chemicals are responsible for the conversion of HgBr to stable gas-phase products? (b) What is the chemical nature of those products? (c) What are the rate coefficients of associated reaction pathways? (d) Which of the gas-phase products can bind effectively with atmospheric particulate matter? (e) Can these gas-phase and particle-bound products be detected and quantified directly?