Grantee Research Project Results
Final Report: Sensitivity of Heterogeneous Atmospheric Mercury Processes to Climate Change
EPA Grant Number: R833375Title: Sensitivity of Heterogeneous Atmospheric Mercury Processes to Climate Change
Investigators: Schauer, James J. , Griffin, Robert J. , Shafer, Martin M. , Holloway, Tracey
Institution: University of Wisconsin - Madison , University of New Hampshire
EPA Project Officer: Chung, Serena
Project Period: February 15, 2007 through February 14, 2010 (Extended to February 14, 2011)
Project Amount: $899,731
RFA: Consequences of Global Change For Air Quality (2006) RFA Text | Recipients Lists
Research Category: Climate Change , Air
Objective:
The overall goal of the project is to quantify the impact of climate change on key atmospheric processes that control the fate of mercury during transport from emission to deposition. Efforts are being directed at building on the existing scientific understanding of atmospheric mercury processes by examining the incremental impact of climate change variables on heterogeneous atmospheric mercury oxidation and depositional processes.
The goal was realized by achieving the following objectives:
- Quantification of the sensitivity of dry deposition of elemental mercury to temperature and sunlight intensity.
- Investigation of the oxidation of elemental mercury in the presence of the complex atmospheric reactions that produce photochemical smog and secondary organic aerosols.
- Investigation of the sensitivity of mercury deposition to climate change variables using a regional chemical transport model that is being evaluated using a year-long data set of hourly speciated atmospheric mercury and event-based wet deposition data.
These efforts are providing a better understanding of impact of climate change on atmospheric mercury processes, supporting the development of strategies to control mercury deposition in the present and future. These results also are helping us to understand the broader impact of climate change.
Summary/Accomplishments (Outputs/Outcomes):
The project has focused on finalizing experimental work and interpreting the results, along with advancing sensitivity studies to improve regional model capability and identify climate-sensitivities. Such work has been progressing in the following three areas:
- Studies of mercury cycling to plants, soils, and other environmental surfaces at the UW-Madison Biotron controlled environment facility, using online mercury instruments and mercury isotope spiking studies.
- Smog chamber studies of mercury oxidation during controlled ozone and secondary organic aerosol (SOA) formation studies using expertise at the University of New Hampshire.
- Regional chemical transport modeling to study atmospheric mercury deposition under current conditions, and evaluate model sensitivity to temperature, precipitation and atmospheric circulation patterns associated with climate change.
Mercury cycling to plants, soils and environmental surfaces
Atmospheric deposition is the primary pathway by which mercury enters aquatic environments in which bacterial methylation and subsequent accumulation in the food chain can occur. The purpose of this module is to comprehensively determine the climate sensitivity of dry atmospheric deposition velocities for gaseous elemental mercury (GEM) to a range of environmental surfaces. This has been done by determining the functional dependencies of deposition on temperature and light irradiance. Various plants and soils were exposed to gaseous elemental mercury enriched in stable isotope 198 (GEM-198), in a controlled environment room at the UW-Biotron facility. Plots of two types of locally collected soil, white ash trees and white spruce trees were placed in the room alongside deposition coupons made from quartz fiber filters, some with absorbent coatings to collect GEM. GEM-198 was introduced into the room augmenting the background concentration of 3-4 ng m-3 over the course of 7 days at three ambient temperatures (10oC, 20oC and 30oC) under dark, fall and spring light conditions. The final design of the apparatus for GEM-198 dosing typically yielded large initial input of isotope into the room, which stabilized at a low constant value as the experiment progressed through the 7 days (Figure 1). We observed significant time, irradiance and temperature dependent enrichment in White Ash, White Spruce and Kentucy Blue Grass, but uptake to soils was typically the limit of detection of the method (Table 1).
The following papers will make up the first two journal articles we currently are drafting to report the results of this experiment. The first paper is a methods development article that concentrates on the results for all of the substrates at one condition (20oC; 170Wm-2 PAR irradiance), while the second explores the temperature and light dependence of uptake to the plants studied.
Paper 1: Dry Deposition of Gaseous Elemental Mercury to Plants and Soil using Mercury Stable Isotopes in a Controlled Environment.
Citation: Rutter AP, Schauer JJ, Shafer MM, Creswell M, Olson MR, Robinson M, Collins RM, Parman AM, Katzman TL, Mallek JL. Dry deposition of gaseous elemental mercury to plants and soil using mercury stable isotopes in a controlled environment. Atmospheric Environment 2011;45:848-855.
Paper 2: Sensitivity of Gaseous Elemental Mercury Dry Deposition to Plants: Impact of Plant Species, Temperature and Light Intensity.
Citation: Rutter AP, Schauer JJ, Shafer MM, Creswell J, Olson MR, Clary A, Robinson M, Parman AM, Katzman TL. Sensitivity of gaseous elemental mercury dry deposition to plants: impact of temperature, light intensity, and plant species. Environmental Science & Technology 2011;45:569-575.
Smog chamber photo-oxidation of GEM in the presence of photochemical smog and secondary organic aerosols
One of the pathways by which GEM is transferred from the atmosphere to aquatic ecosystems is by wet and dry deposition after oxidation to reactive mercury. The oxidation of GEM by oxidants such as ozone, OH, and various halogen species previously have been studied only in homogeneous reactions systems (Ariya, et al., 2002; Ariya and Ryzhkov, 2003; Calvert and Lindberg, 2005; Hall, 1995; Hall, et al., 1995; P'yankov, 1949; Pal and Ariya, 2004a; Pal and Ariya, 2004b; Raofie and Ariya, 2003; Raofie and Ariya, 2004; Sommar, et al., 1996; Sommar, et al., 1997; Tokos, et al., 1998), which do not effectively represent the heterogeneous aerosol reaction systems that are present in the environment. This module aims to evaluate heterogeneous reaction rates of GEM by observing the effect of a complex smog reaction system that leads to the formation of SOA on reaction rate kinetics for oxidants such as ozone and OH.
During the summer of 2008, we conducted 6 weeks of experiments in the smog chamber at the University of New Hampshire. GEM-198 was added to ongoing oxidations propene, alpha-pinene, isoprene, toluene, and 2-butanol (OH scavenger) in the dark and under ultraviolet (350BL) fluorescent lamps. Concentrations of GEM were monitored real-time using a Tekran 2537A GEM analyzer, and GEM oxidized to reactive mercury (RM) was collected on specially prepared filter substrates (Rutter, et al., 2007) as described above in the dry deposition experiments.
The results from the chamber studies will be reported in two journal articles that are in preparation. The first paper will focus on the results from the gas phase oxidation experiments with ozone and propene, while the second paper will report results from the heterogeneous experiments in which SOA was produced.
Paper 3: The oxidation of atmospheric gaseous elemental mercury in volatile organic carbon reaction systems
Citation: Rutter AP, Shakya KM, Lehr RM, Schauer JJ, Griffin RJ. Observation of decreased net oxidation of gaseous elemental mercury in the presence of secondary organic aerosol formation in the dark. Submitted to Atmospheric Environment (March 2011).
Chamber experiments were conducted to measure the net oxidative losses of GEM in the presence of ozone, and with ozone and propene. Studies of the effect of secondary OH in the propene experiments were performed by adding OH-scavenger. The initial concentrations of reactants were close to ambient concentrations and much lower than in previous studies.
Paper 4: The oxidation of atmospheric gaseous elemental mercury in SOA-forming organic reaction systems
Status: In preparation
Chamber experiments were performed to measure net oxidative losses of GEM in the presence of organic reaction systems that yielded SOA. In particular, we used isoprene, alpha-pinene as biogenic VOC models, and toluene as an anthropogenic VOC model. Propene was added to all of the experiments to allow direct comparison of the results of this study with those presented in Paper 3. In some experiments, we added 2-butanol to act as an OH scavenger allowing us to probe the effects of this radical on the net oxidation of GEM.
CMAQ modeling to simulate mercury
Paper 5: Performance of the CMAQ Model Simulating Mercury in the Great Lakes Region.
Status: In preparation
We have completed our analysis of regional model performance against two year-long time series of speciated mercury concentrations and event-based measurements of total wet deposition. We have employed the regional Community Multi-scale Air Quality (CMAQ) model with the mercury atmospheric chemistry and deposition module. In addition, we have simulated high-resolution (12 km x 12 km) meteorology for 2003 using the Weather Research and Forecasting (WRF) model. We have run simulations in CMAQ with 36 km x 36 km resolution over the continental United States (CONUS) and 12 km x 12 km resolution over the Upper Midwestern United States.
Paper 6: Evaluation of CMAQ Model ability to capture climate-chemistry relationships
Status: In Preperation
To develop effective strategies for air quality improvement, an understanding of how meteorology and climate affect air pollution also is needed. Many studies have examined the effects of climate on ozone pollution over the continental United States, a number of which are highlighted in a recent review by Jacob and Winner (2009). Fewer studies have characterized the response of mercury or particulate matter to meteorology. Even for the relatively well-studied relationships between climate and ozone, only two studies have used climate-chemistry relationships to evaluate model performance (Jacob, et al., 1993 and Steiner, et al., 2006).
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 4 publications | 4 publications in selected types | All 4 journal articles |
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Holloway T, Voigt C, Morton J, Spak SN, Rutter AP, Schauer JJ. An assessment of atmospheric mercury in the Community Multiscale Air Quality (CMAQ) model at an urban site and a rural site in the Great Lakes Region of North America. Atmospheric Chemistry and Physics 2012;12(15):7117-7133. |
R833375 (Final) R831840 (Final) |
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Plachinski SD, Holloway T, Meier PJ, Nemet GF, Rrushaj A, Oberman JT, Duran PL, Voigt CL. Quantifying the emissions and air quality co-benefits of lower-carbon electricity production. Atmospheric Environment 2014;94:180-191. |
R833375 (Final) |
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Rutter AP, Schauer JJ, Shafer MM, Creswell JE, Olson MR, Robinson M, Collins RM, Parman AM, Katzman TL, Mallek JL. Dry deposition of gaseous elemental mercury to plants and soil using mercury stable isotopes in a controlled environment. Atmospheric Environment 2011;45(4):848-855. |
R833375 (Final) |
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Rutter AP, Schauer JJ, Shafer MM, Creswell J, Olson MR, Clary A, Robinson M, Parman AM, Katzman TL. Climate sensitivity of gaseous elemental mercury dry deposition to plants:impacts of temperature, light intensity, and plant species. Environmental Science & Technology 2011;45(2):569–575. |
R833375 (Final) |
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Supplemental Keywords:
RFA, Air, climate change, environmental monitoringProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.