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案（公法111-5）资助的。本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的化学形态是否随时间和空间的变化而变化？形成RGM的过程是什么？RGM的干沉积在不同的环境条件下是如何变化的？所有这些问题都解决了汞全球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的形式将是气团中大气氧化剂与该地点相互作用的函数。RGM被认为是由臭氧、羟基自由基和含卤素化合物反应形成的。与海洋气团相关的RGM可能主要是HgCl2，而来自自由对流层的气团和高海拔地区的空气中HgBr2可能是主要形式，而与臭氧和羟基自由基丰富的城市地区相关的HgO则是主要形式。本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浓度和沉积将分别使用标准的自动化分析方法和干沉积模型，以及新开发的被动采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基于它们从替代表面释放的温度的特定化合物。将采用反轨迹分析，以了解在每个地点收集的与特定形式的RGM有关的空气来源；社区多尺度空气质量模型和汞模块将用于了解大气化学对观测到的空气汞浓度和沉积的影响。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、分析和解释这个项目的数据，使他们成为研究团队不可或缺的组成部分。

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.