Grantee Research Project Results
2009 Progress 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 Period Covered by this Report: February 15, 2009 through February 14,2010
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 proposed 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 is being realized by achieving the following objectives:
1) Quantification of the sensitivity of dry deposition of elemental mercury to temperature and sunlight intensity
2) Investigation of the oxidation of elemental mercury in the presence of the complex atmospheric reactions that produce photochemical smog and secondary organic aerosols
3) 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 are also helping understand the broader impact of climate change.
Progress Summary:
Year 3 of 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:
1) Studies of mercury cycling to plants, soils, and other environmental surfaces at the UW-Madison Biotron controlled environment facility, using on-line mercury instruments and mercury isotope spiking studies.
2) Smog chamber studies of mercury oxidation during controlled ozone and SOA formation studies using expertise at the University of New Hampshire
3) 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 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). Two manuscripts are in preparation that cover these research activities.
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 have previously only been studied 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 secondary organic aerosol 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, and 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. Two manuscripts are currently in preparation that cover these research experiments.
Modeling Analysis of Mercury in the Great Lakes Region
In this third year of the project, 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. Based on our finding that the regional model significantly overestimates reactive mercury species, we have modified the model chemical mechanism to characterize how individual reaction pathways contribute to simulated concentration and deposition. Results from this final stage in the analysis will identify necessary directions for model development, and characterize key climate dependencies.
As noted in the proposal, we are employing 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 U.S. (CONUS) and 12 km x 12 km resolution over the Upper Midwestern U.S. As noted in the Year 2 report, we are not proceeding with the very-high resolution experiments (4 km x 4 km) due to obvious errors in CMAQ, discussed below, and the associated demands of model development and evaluation.
Emissions were employed from the 2002 National Emissions Inventory (EPA). These emissions were processed using SMOKE v. 2.4, which allocated the emissions to our grid, and adapted emissions to the specific weather conditions of the 2003 study year (especially relevant for biogenic emissions and temperature-dependent vehicle emissions).
The Weather Research and Forecasting (WRF) model was used to generate the input meteorological datasets, constrained to observed weather patterns by “nudging” the model to the assimilated 40 km x 40 km data from the National Center for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR) data. These custom WRF datasets were compared with ground-based observations of precipitation and temperature, as well as the spatially continuous NARR data.
As noted in our Year 2 report, this set-up has allowed us to evaluate CMAQ performance, and to quantify the impact of boundary conditions characteristic of mercury inflow to the U.S. In Year 3, we have completed this evaluation, and we have modified the CMAQ chemical mechanism to isolate the contributions of individual chemical processes. Under the no-cost extension approved for the project, this work will continue through February 2011. Our progress is discussed below.
We have prepared a draft manuscript for submission in summer 2010, reporting evaluation of the current-generation mercury mechanism in CMAQ and sensitivity to boundary inflow vs. regional emissions. This evaluation, with major findings presented in the Year 2 progress report, employed a unique data set of hourly atmospheric mercury measurements of GEM, RGM and PHg that were co-located with event based mercury wet deposition measurements collected at the Devil’s Lake, Wisconsin mercury TMDL site (available for 2003). In addition, we have compared with mercury concentration measurements collected in Milwaukee, Wisconsin (for 2004), and with available data on mercury wet deposition from across the Upper Midwestern U.S.
Future Activities:
The main goals of Year 3 of the project are to: 1) continue modeling efforts to identify key processes that are missing or biased in CMAQ and integrate new models that represent experimental results obtained as part of the project, 2) continue Biotron and fog water experiments, and 3) complete and submit several manuscripts currently in preparation.
References:
Ariya, P. A., Khalizov, A. and Gidas, A., Reactions of gaseous mercury with atomic and molecular halogens: Kinetics, product studies, and atmospheric implications, Journal of Physical Chemistry A 106 (2002), pp. 7310-7320.
Ariya, P. A. and Ryzhkov, A., Atmospheric transoformation of elemental mercury upon reactions with halogens, Journal De Physique Iv 107 (2003), pp. 57-59.
Bash, J. O., Description and initial simulation of a dynamic bidirectional air-surface exchange model for mercury in Community Multiscale Air Quality (CMAQ) model, Journal of Geophysical Research-Atmospheres 115 (2010), pp.
Bash, J. O., Bresnahan, P. and Miller, D. R., Dynamic surface interface exchanges of mercury: A review and compartmentalized modeling framework, Journal of Applied Meteorology and Climatology 46 (2007), pp. 1606-1618.
Bash, J. O. and Miller, D. R., Growing season total gaseous mercury (TGM) flux measurements over an Acer rubrum L. stand, Atmospheric Environment 43 (2009), pp. 5953-5961.
Bullock, O. R. and Brehme, K. A., Atmospheric mercury simulation using the CMAQ model: formulation description and analysis of wet deposition results, Atmospheric Environment 36 (2002), pp. 2135-2146.
Bushey, J. T., Nallana, A. G., Montesdeoca, M. R. and Driscoll, C. T., Mercury dynamics of a northern hardwood canopy, Atmospheric Environment 42 (2008), pp. 6905-6914.
Calvert, J. G. and Lindberg, S. E., Mechanisms of mercury removal by O-3 and OH in the atmosphere, Atmospheric Environment 39 (2005), pp. 3355-3367.
Graydon, J. A., St Louis, V. L., Lindberg, S. E., Hintelmann, H. and Krabbenhoft, D. P., Investigation of mercury exchange between forest canopy vegetation and the atmosphere using a new dynamic chamber, Environmental Science & Technology 40 (2006), pp. 4680-4688.
Hall, B., THE GAS-PHASE OXIDATION OF ELEMENTAL MERCURY BY OZONE, Water Air and Soil Pollution 80 (1995), pp. 301-315.
Hall, B., Schager, P. and Ljungstrom, E., AN EXPERIMENTAL-STUDY ON THE RATE OF REACTION BETWEEN MERCURY-VAPOR AND GASEOUS NITROGEN-DIOXIDE, Water Air and Soil Pollution 81 (1995), pp. 121-134.
Lin, C. J., Pongprueksa, P., Lindberg, S. E., Pehkonen, S. O., Byun, D. and Jang, C., Scientific uncertainties in atmospheric mercury models I: Model science evaluation, Atmospheric Environment 40 (2006), pp. 2911-2928.
Lyman, S. N., Gustin, M. S., Prestbo, E. M. and Marsik, F. J., Estimation of dry deposition of atmospheric mercury in Nevada by direct and indirect methods, Environmental Science & Technology 41 (2007), pp. 1970-1976.
P'yankov, V. A., O kinetike reaktsii parov rtuti s ozonom (Kinetics of the reaction of mercury vapour with ozone). , Zhurmal Obscej Chemii Akatemijaneuk SSSR 19 (1949.), pp. pp. 224–229.
Pal, B. and Ariya, P. A., Gas-phase HO center dot-Initiated reactions of elemental mercury: Kinetics, product studies, and atmospheric implications, Environmental Science & Technology 38 (2004a), pp. 5555-5566.
Pal, B. and Ariya, P. A., Studies of ozone initiated reactions of gaseous mercury: kinetics, product studies, and atmospheric implications, Physical Chemistry Chemical Physics 6 (2004b), pp. 572-579.
Raofie, F. and Ariya, P. A., Kinetics and products study of the reaction of BrO radicals with gaseous mercury, Journal De Physique Iv 107 (2003), pp. 1119-1121.
Raofie, F. and Ariya, P. A., Product study of the gas-phase BrO-initiated oxidation of Hg-0: evidence for stable Hg1+ compounds, Environmental Science & Technology 38 (2004), pp. 4319-4326.
Rutter, A. P., Hanford, K. L., Zwers, J. T., Perillo-Nicholas, A. L., Schauer, J. J., Worley, C. A., Olson, M. L. and DeWild, J. F., Evaluation of an Off-line Method for the Analysis OF Atmospheric Reactive Gaseous Mercury and Particulate Mercury, In Press by the Journal of Air and Waste Management Association (2007), pp.
Rutter, A. P., Schauer, J. J., Lough, G. C., Snyder, D. C., Kolb, C. J., Von Klooster, S., Rudolf, T., Manolopoulos, H. and Olson, M. L., A comparison of speciated atmospheric mercury at an urban center and an upwind rural location, Journal of Environmental Monitoring 10 (2008), pp. 102-108.
Rutter, A. P., Snyder, D. C., Stone, E. A., Schauer, J. J., Gonzalez-Abraham, R., Molina, L. T., Márquez, C., Cárdenas, B. and de Foy, B., In situ measurements of speciated atmospheric mercury and the identification of source regions in the Mexico City Metropolitan Area, Atmos. Chem. Phys. 9 (2009), pp. 207-220.
Si, L. and Ariya, P. A., Reduction of oxidized mercury species by dicarboxylic acids (C-2-C-4): Kinetic and product studies, Environmental Science & Technology 42 (2008), pp. 5150-5155.
Sommar, J., Hallquist, M. and Ljungstrom, E., Rate of reaction between the nitrate radical and dimethyl mercury in the gas phase, Chemical Physics Letters 257 (1996), pp. 434-438.
Sommar, J., Hallquist, M., Ljungstrom, E. and Lindqvist, O., On the gas phase reactions between volatile biogenic mercury species and the nitrate radical, Journal of Atmospheric Chemistry 27 (1997), pp. 233-247.
Tokos, J. J. S., Hall, B., Calhoun, J. A. and Prestbo, E. M., Homogeneous gas-phase reaction of Hg-0 with H2O2, O-3, CH3I, and (CH3)(2)S: Implications for atmospheric Hg cycling, Atmospheric Environment 32 (1998), pp. 823-827.
Journal Articles:
No journal articles submitted with this report: View all 4 publications for this projectSupplemental 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.