Integrating Multiple Methods to Understand the Atmospheric Chemistry of Mercury and Mercury Dry Deposition from the Pacific to the Basin and Range

该奖项是根据2009年《美国复苏和再投资法》(公法111-5)资助的。该项目采用多方面的方法，重点解决以下问题：什么是活性气态汞(RGM)？RGM的化学形式是否会随着空间和时间的变化而变化？RGM形成的过程是什么？RGM的干沉积如何在不同的环境环境中变化？所有这些问题都涉及全球汞生物地球化学循环中的重大不确定性。一个可行的假设是，一个地点空气中RGM的形式将是与该地点相互作用的气团中大气氧化剂的函数。RGM假定是由臭氧、羟基自由基和含卤素化合物反应形成的。与海洋气团有关的RGM可能主要是HgCl2，而HgBr2可能是来自自由对流层的气团和高海拔地区空气中的主要形式，HGO是与臭氧和羟基自由基丰富的城市地区有关的形式。该项目的现场选址包括上述所有地区，包括2个沿海地点、3个高海拔地点、1个城市地点和3个大陆地点。RGM的浓度和沉积将分别使用标准的自动分析方法和干沉积模型以及新开发的被动取样器和替代表面进行量化。RGM的形式将使用一种方法来识别，该方法旨在根据特定化合物从替代表面释放的温度来识别它们。将使用反向轨迹分析来了解在每个站点收集的特定形式的RGM所关联的空气来源；将使用带有汞模块的社区多尺度空气质量模式来了解造成所观测到的空气汞浓度和沉积的大气化学。来自五所高中的学生以及来自几个机构的四名本科生每年将帮助收集、分析和解释该项目的数据，使他们成为研究团队不可或缺的一部分。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project applies a multifaceted approach focused to address the following questions: What is reactive gaseous mercury (RGM)? Does the chemical form of RGM vary over space and time? What are the processes responsible for RGM formation? How does dry deposition of RGM vary across environmental settings? All of these questions address significant uncertainties in the global biogeochemical cycle of Hg. A working hypothesis is that the form of RGM in the air at a site will be a function of the atmospheric oxidants in the air masses interacting with that location. RGM is hypothesized to be formed by reactions with ozone, hydroxyl radical and halogen containing compounds. RGM associated with marine air masses may be predominantly HgCl2, while HgBr2 may be the dominant form in air masses derived from the free troposphere and in the air at high elevation sites, and HgO the form associated with urban areas where ozone and hydroxyl radical will be abundant. Field sites for this project have been chosen to include all of the above areas with 2 coastal sites, 3 high elevation sites, 1 urban site and 3 continental sites. RGM concentrations and deposition will be quantified using a standard automated analytical method and a dry deposition model, as well as using newly developed passive samplers and surrogate surfaces, respectively. The form of RGM will be identified using a method designed to identify specific compounds based on the temperature at which they are released from surrogate surfaces. Back trajectory analyses will be applied to understand the source of the air associated with specific forms of RGM collected at each site; and the Community Multiscale Air Quality model with the mercury module will be used to understand the atmospheric chemistry responsible for the observed air Hg concentrations and deposition. Students from five high schools, as well as four undergraduate students from several institutions will help collect, analyze and interpret data each year of this project making them an integral component of the research team.