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G4A Atmospheric Mercury: Transport and deposition

Monday, 25 July, 2011

MG4A-P1 — 11:00-12:00 and 17:30-18:30
MODELING OF ATMOSPHERIC MERCURY WITH THE DANISH EULERIAN HEMISPHERIC MODEL
Authors: SOERENSEN, Anne L1, SKOV, Henrik1, CHRISTENSEN, Jesper H1
(1) Aarhus University, NERI, anls@dmu.dk

A 3-D bromine/mercury chemistry model is in the progress of development at National Environmental Research Institute. The model is based on the Danish Eulerian Hemispheric model (DEHM) system. This system consists of a weather forecast model, the PSU/NCAR Mesoscale Model version 5 (MM5) modeling subsystem, which is driven by global analyzed meteorological data either ECMWF or NCEP, and a 3-D atmospheric transport model, the DEHM model. The horizontal space of the model system is defined on a regular 150x150 grid that covers the Northern Hemisphere with a grid-resolution of 150 km at 60oN and 29 vertical layers up to a height of 16 km. The whole system also includes two-way nesting capabilities, so it is possible to do finer (150 km -> 50 km -> 16.67 km, etc) model calculations over e.g. the Arctic Ocean or Greenland. A presentation of the model system will be given with focus on the implementation of new and updated halogen and mercury chemistry schemes. The model-results will be verified against measurements obtain in the Danish AMAP stations at Nuuk and Station Nord on respectively the south west coast of Greenland and on north east coast of Greenland as well as cruise data for the North Atlantic Ocean from the Galathea 3 circum navigation. The focus of the presentation is the simulation of mercury in the Arctic.

MG4A-P2 — 11:00-12:00 and 17:30-18:30
GASEOUS MERCURY DEPLETION EVENTS AT CAPE POINT
Authors: BRUNKE, E.-G.1, EBINGHAUS, R.2, KOCK, H.H. 3, LABUSCHAGNE, C.4, KUSS, J.5, SLEMR, F. 6
(1) South African Weather Service, ernst.brunke@weathersa.co.za; (2) GKSS Forshungszentrum Geesthacht GmbH; (3) GKSS Forschungszentrum Geesthacht GmbH; (4) ; (5) Leibniz Institute for Baltic Sea Research; (6) Max-Planck-Institue for Chemistry.

Since the beginning of the continuous measurements of gaseous mercury at Cape Point (South Africa) in March 2007 until July 2008 numerous mercury depletion events had been observed as reported by Brunke et al. (Atmos. Chem. Phys. 10, 1121-1131, 2010). In contrast to mercury depletion events in polar regions these depletion events last only several hours, occur mostly during the noon and are not accompanied by ozone depletion. They have also been observed elsewhere in the marine boundary layer as well and their mechanism remains obscure. Numerous depletion events of this type have been observed at Cape Point since July 2008 (on average one per week) providing a more detailed information about their occurrence such as on their seasonal and diurnal frequencies, relation to other trace gases and particles, and relation to backward trajectories. We will present this new information and discuss its implications for the mechanism of this type of mercury depletion events.

MG4A-P4 — 11:00-12:00 and 17:30-18:30
CLIMATE SENSITIVITY OF GASEOUS ELEMENTAL MERCURY ACCUMULATION IN TREE LEAVES USING STABLE ISOTOPES IN A CONTROLLED ENVIRONMENT
Authors: RUTTER, Andrew1, SCHAUER, James J.2, SHAFER, Martin M.2, CRESWELL, Joel E. 2, OLSON, Michael R2, ROBINSON, Michael2, PARMAN, Andrew2, MALLEK, Justin 2, CLARY, A.3, KATZMAN, T.L. 3
(1) Rice University & University of Wisconsin-Madison, andrew.p.rutter@rice.edu; (2) UW-Madison; (3) ;

The dry deposition of gaseous elemental mercury (GEM) to plant leaves is considered to be an important atmospheric removal process for atmospheric mercury particularly in locations uninfluenced by point sources. Previous studies have measured foliar accumulation in tree leaves using field and chamber studies, but uncertainty remains in the dependence of foliar accumulation on temperature and irradiance. It is important for modeling mercury deposition under future climate scenarios to be able to account for these dependences.

The goal of this study was to experimentally measure these dependences by exposing tree saplings to isotopically enriched GEM under different temperature and light settings, and to then parameterize the observed relationship for use in atmospheric mercury models. White Ash, White Spruce, and Kentucky Blue Grass were exposed for 1 day in a controlled environment room at the University of Wisconsin Biotron. Temperature was varied between 10oC and 30oC, while irradiance was varied between dark and 170Wm-2. GEM enriched in stable isotope 198 (GEM-198) was released into the room from a custom built vapor source over the course of the experiment. Mercury was recovered from the samples using acidic digestions and leaches, and then analyzed for the content of GEM-198 by high resolution ICPMS. The measurements were parameterized using the resistance model of dry deposition, and the data were then interpolated to produce temperature-irradiance-resistance surface plots.

The newly determined relationships between dry deposition resistance, and temperature and irradiance were used to estimate foliar accumulation of GEM at Devil’s Lake State Park, WI. Measurements of GEM, PHg, and RGM made during the growing season of 2003 using a Tekran atmospheric mercury analyzer (1130-1135-2537) were used with the resistances from this study and published values in order to model and compare the deposition of GEM, PHg and RGM to tree foliage in the Park. Foliar accumulation estimates of GEM compared well with measured foliar accumulations from other northern forests. Comparisons between RGM, PHg and GEM dry deposition estimates to foliage revealed that GEM was always at least as important as RGM and PHg.

MG4A-P5 — 11:00-12:00 and 17:30-18:30
THE INFLUENCE OF THE NORTH ATLANTIC OSCILLATION PHASE MERCURY TRANSPORT IN THE NORTHERN HEMISPHERE
Authors: LO FEUDO, Teresa 1, HEDGECOCK, Ian M.2, JUNG, Gerlinde3, PIRRONE, Nicola4
(1) CNR Institute of Atmospheric Pollution Research, t.lofeudo@iia.cnr.it; (2) CNR-Institute of Atmospheric Pollution Research, Division of Rende, Italy; (3) MARUM Center for Marine Environmental Sciences Department of Geosciences, University of Bremen ; (4) CNR-Institute of Atmospheric Pollution Research.

Large scale climatological effects can have a significant influence on intercontinental mercury transport. The most important index for climatic variability in the Northern Hemisphere is the North Atlantic Oscillation (NAO), (Hurrell, J. W., and H. van Loon, 1997). The NAO index refers to a redistribution of atmospheric mass between the Arctic and the subtropical Atlantic. It swings from one phase to another producing large changes in surface air temperature, winds and precipitation over the Atlantic as well as the adjacent continents. During the positive phase of the NAO transport tends to be from the North America towards North-western Europe and from Europe towards the Arctic, in its negative phase trans-Atlantic transport tends to be southerly, influencing the Mediterranean, while transport in northern Europe can be reversed with Arctic air flowing southwards to north and central Europe (Hurrell, J. W. et al., 2003). In the transition from its positive to its negative phase it is possible for pollution transport to the Arctic to be enhanced until the negative phase is well established (Hurrell, J.W., Clara Deser, 2009). The global atmospheric mercury chemistry and transport model ECHMERIT (Jung, G. et al., 2009), has been used to examine the role of the NAO on mercury transport and its inter annual variability . We carried out simulations for four years 2008-2010 and we report preliminary results of the hemispherical distribution and transport of elemental mercury during these three winters, when the NAO was positive (winter 2008/9), changed from positive to strongly negative (winter 2009/10) and from negative to slightly positive and back to negative (winter 2010/2011).

The model’s ability to predict mercury transport under these quite different conditions has been tested and compared with data from measurement station. The export of elementary mercury towards the Arctic from European source regions was more frequent when the NAO was positive and Hg concentrations were found to be roughly 5% higher within the Arctic Circle with respect to years when the NAO was negative. Mercury from North America is transported to the Arctic Circle in both phases of the NAO, however the amount is reduced when the NAO is negative.

MG4A-P6 — 11:00-12:00 and 17:30-18:30
INVESTIGATION OF EFFECTS OF VARYING MODEL INPUTS ON MERCURY DEPOSITION ESTIMATES IN THE SW US
Authors: MYERS, Thomas1, ATKINSON, R. Dwight2, BULLOCK, O. Russell3, BASH, Jesse O.4
(1) ICF International, tmyers@icfi.com; (2) Office of Water, U.S. EPA; (3) National Exposure Research Laboratory, U.S EPA; (4) National Exposure Research Laboratory, U.S. EPA.

CMAQ model version 4.7.1 was used to simulate mercury wet and dry deposition for a domain covering the continental U.S. The simulations used MM5 meteorological files and the US EPA CAMR emissions inventory. Using tagging methods implemented by ICF (the Particle and Precursor Tagging Methodology (PPTM)) and tracer simulations, this investigation focuses on the contributions of boundary concentrations to deposited mercury in the SW U.S.

Concentrations of oxidized mercury species along the boundaries of the domain, in particular the upper layers of the domain, can make significant contributions to the simulated wet and dry deposition of mercury in the SW U.S. In order to better understand the contributions of boundary conditions to deposition, inert tracer simulations were conducted to quantify the amount of air mass transported across the boundaries of the domain at various altitudes and to quantify the amount of those air masses that reach and potentially deposit to the land surface in the SW U.S.

Simulations using alternate sets of boundary concentrations, including estimates from the global models CTM, GEOS-CHEM, and GRAHM, and alternate meteorological data (for different years) are analyzed in this poster presentation. CMAQ dry deposition in the SW US is sensitive to differences in the atmospheric dynamics and atmospheric mercury chemistry parameterizations between the global models used for boundary conditions.

MG4A-P7 — 11:00-12:00 and 17:30-18:30
MERCURY TRANSPORT STUDIES UNDER THE INTERNATIONAL POLAR YEAR PROJECT OF INTERCONTINENTAL ATMOSPHERIC TRANSPORT OF ANTHROPOGENIC POLLUTANTS TO THE ARCTIC (INCATPA)
Authors: COLE, Amanda1, STEFFEN, Alexandra1, HUNG, Hayley1, DOUGLAS, Thomas A.2, FENG, Xinbin3, KONOPLEV, Alexey4, DASTOOR, Ashu1, DURNFORD, Dorothy 1, SCHERZ, Christina1, LEE, Patrick1
(1) Environment Canada, amanda.cole@ec.gc.ca; (2) U.S. Army Cold Regions Research and Engineering Laboratory; (3) Chinese Academy of Sciences; (4) Centre for Environmental Chemistry SPA;

Elevated levels of mercury and other pollutants are an ongoing threat to the health of Arctic people and wildlife, despite the vast distance that separates the region from major anthropogenic sources of these contaminants. The International Polar Year (IPY) project Intercontinental Atmospheric Transport of Anthropogenic Pollutants to the Arctic (INCATPA) investigated the transport of pollutants, specifically persistent organic pollutants and mercury, from source regions to the remote Arctic. Transport from Asia is of particular interest since Asian sources comprise a significant and increasing fraction of global mercury emissions. The INCATPA project also investigated how climate change may affect atmospheric chemistry and transport processes of these pollutants to the Arctic.

Mercury studies under INCATPA have involved concurrent measurements of ambient mercury during the period 2007-2009 at new and ongoing sites in Arctic and Pan-Pacific regions. In Canada, gaseous elemental mercury (GEM) measurements have been collected at Whistler, British Columbia; Little Fox Lake, Yukon and Alert, Nunavut. Outside of Canada, measurements were collected at Barrow, Alaska; Amderma, Russia; Mount Changbai, China and Waliguan, China. These measurements offer validation for Environment Canada’s atmospheric mercury model (GRAHM) to elucidate the trans-Pacific transport of mercury from Asia into the Canadian Arctic (also within the INCATPA Program). We will present results from the ground level mercury measurements and discuss the relevance of these measurements on future national and international policies.

MG4A-P8 — 11:00-12:00 and 17:30-18:30
MEASUREMENTS BASED MODEL SIMULATIONS OF MERCURY OXIDATION AT THE DEAD SEA, ISRAEL
Author: TAS, Eran1
(1)The Hebrew University, Safra Campus, Jerusalem, Israel , eran.tas@mail.huji.ac.il

The occurrence of atmospheric mercury depletion events (AMDEs) outside of the Polar Regions, in the warm temperatures of the Dead Sea, Israel has been recently discovered; suggesting that atmospheric mercury can readily be oxidized under temperature conditions of the mid-latitudes and tropics. The efficient oxidation of gaseous elemental mercury (GEM) at temperate conditions was unexpected, considering that the thermal back dissociation reaction of HgBr is more than 2.5 orders of magnitude higher under the Dead Sea temperature, compared with the polar temperatures. The present study aims to improve our understanding of Br-Hg interaction, using numerical simulations based on a comprehensive measurement campaign performed at the Dead Sea during summer 2009. The simulations results indicate that the reaction rate of GEM with BrO is faster compared with most previous reported values, and only about twice slower than the reaction rate of GEM with Br. This point out that BrO is more efficient oxidant than Br in the ozone reach atmosphere. This further explains why the efficiency of GEM oxidation by reactive bromine species (RBS) at the Dead Sea, is comparable to the efficiency in the Polar Regions, under much higher temperatures. These findings support the hypothesis stated in previous studies that Br-induced GEM depletion can be important over oceans in the mid-latitudes and tropics. The present study estimated that the oxidation rates for k{Hg+Br} and k{Hg+BrO} are 3.0E-13cm3 molecule-1 s-1and 1.5E-13cm3 molecule-1 s-1, respectively. The model results further indicate that HgO produced by the reaction of Hg and BrO produces a solid product, suggesting that,under the Dead Sea conditions, it may undergo condensation.

MG4A-P9 — 11:00-12:00 and 17:30-18:30
WET DEPOSITION OF ATMOSPHERIC MERCURY IN CHONGQING, CHINA
Authors: WANG, Yongmin1, GUO, Yaozu1, HU, Junjian1, WANG, Dingyong1
(1)1. Key Laboratory of the Three Gorges Reservoir Region’s Eco-Environment (Ministry of Education), College of Resources and Environment, Southwest University, Chongqing 400715, China, wangym.540@163.com

As the most important industry in southwest of China, Chongqing has a large consumption of energy, above 70% being coal. The terrain of valleys, hills and mountains and the weather of no wind or breeze arouse the increased atmospheric stability and radiation inversion, which is easy to lead trouble in mercury spreading and local atmospheric mercury pollution. It reported that the concentration of atmospheric total Hg in main districts of Chongqing is four times as high as global background value. In order to measure the removal effects of wet deposition on atmospheric mercury, the rain samples were collected from three sites: Nanan district (NA, city center), Beibei district (BB, suburb), Jinyun mountain (JY, exurb) in Chongqing . We observed total and methyl Hg (THg and MeHg) concentrations and depositions in samples during the period from July, 2010 to Feb, 2011 and analyzed their temporal and spatial variation. The preliminary results show that the ranges of the monthly volume-weighted (VMW) THg and MeHg concentration are 21.20-40.39ng/l and 0.07-0.77ng/l,respectively. The monthly VMW THg concentration decreased in order of NA?BB?JY, while the order for MeHg was BB?NA?JY. The monthly THg and MeHg deposition in precipitation was 0.93-7.01µg/m2 and 0.0042-0.0485 µg/m2. The order for amount of THg and MeHg deposition is similar to VMW. A monthly pattern for THg and MeHg in precipitation is clearly evident, with increased THg and MeHg depositions observed in July and September in three sites. Meteorological analysis indicated that the precipitation amount was found to be highly significant positive correlation with Hg deposition and significant positive correlation with MeHg deposition.

MG4A-P10 — 11:00-12:00 and 17:30-18:30
ANALYSIS OF PARTICULATE MERCURY IN MARINE AND CONTINENTAL ATMOSPHERES
Authors: FEDDERSEN, Dara1, TALBOT, Robert2, MAO, Huiting3, SMITH, Melissa1, SIVE, Barkley1
(1) University of New Hampshire, dmy49@unh.edu; (2) University of Houston; (3) SUNY College of Environmental Science and Forestry;

A study was conducted at a marine site, Appledore Island, in the Gulf of Maine and at a nearby continental site, Thompson Farm, to collect and assess atmospheric mercury and better understand mercury cycling in the atmosphere. In particular, we were pursuing how important the particulate phase in the marine boundary layer is to the mercury budget and its role in cycling. Over one year, a total of six campaigns were conducted. Mercury was collected using three different types of instrumentation: a Tekran automated system collecting elemental, reactive, and particulate mercury; cascade impactors collecting size-fractionated particulate mercury; and bulk filters collecting total particulate mercury. We determined that: (1) the bulk filters show much higher concentrations of particulate mercury than the automated system; (2) the aersosol size distribution of mercury depends on location and source of air; (3) our continental and marine sites are often affected by the same source of air. Further, we show a diurnal cycle of particulate mercury that matches that of elemental mercury. We calculated the dry deposition of particulate mercury for each season, showing that summer at both sites has the highest depletion rates of 5-7 ppqv/day compared to winter and spring at Thompson Farm, at about 1 and 0.5 ppqv/day, respectively. We compared bulk filters to the impactors to assess the loss of mercury when using filters for long time periods. When week-long impactors were run in conjunction with consecutive three-hour time resolution bulk filters, the impactors lost about half of their mercury. When the impactors were run in conjuntion with 24 hour bulk filters, the impactors lost slightly less mercury compared to the bulk filters. We also integrated the impactors to correlate directly with the Tekran data, and found that the particulate mercury concentration on the impactors was overall about half of the filter values. This study has the goal of providing a more detailed evaluation of sources, cycling and chemical transformations of mercury in both the marine and continental atmospheres.

MG4A-P11 — 11:00-12:00 and 17:30-18:30
ATMOSPHERE OCEAN EXCHANGE OF MERCURY IN A COUPLED REGIONAL MODEL FOR THE NORTH AND BALTIC SEA AREA
Authors: BIESER, Johannes1, AULINGER, Armin1, DAEWEL, Ute2, MATTHIAS, Volker1, QUANTE, Markus1, SCHRUM, Corinna2, EBINGHAUS, Ralf1
(1) Helmholtz-Zentrum Geesthacht, johannes.bieser@hzg.de; (2) Geophysical Institute, University of Bergen;

Mercury in its various chemical states is known to have adverse effects on human health. The European FP7 Research Project GMOS (Global Mercury Observation System) is currently working on the implementation of a world spanning observation system for atmospheric mercury. GMOS also includes the global and regional modelling of atmospheric mercury. Here, the focus is on the further development of the mercury chemistry schemes, on the coupling of the global and regional model systems and their application to investigate past and future pathways of atmospheric mercury transport. Three different model systems are used on the regional scale, one of it is the Hg-version of the Community Multiscale Air Quality (CMAQ) model. At the Helmholtz-Zentrum Geesthacht,

CMAQ is applied to determine atmospheric concentrations of mercury in the area of the North- and Baltic Sea. Anthropogenic mercury emissions are distributed in space and time by the SMOKE for Europe emission model. The worldwide oceans are known to be responsible for roughly half of today’s mercury emissions into the atmosphere. This includes the North- and Baltic Seas which are major sources for mercury inside our model domain. To determine the mercury flux between the ocean and the atmosphere we plan to couple the three dimensional ocean model ECOSMO to the chemistry transport model (CTM). ECOSMO is a physical-biogeochemical model based on the Hamburg Shelf Ocean Model (HAMSOM). The CTM calculates the direct deposition of nutrients and mercury into the ocean. ECOSMO was expanded to include the mercury species Hg0, Hg2+, and particulate Hgpart. The model accounts for photoreactions between Hg0 and Hg2+ as well as dark oxidation of Hg0. Additionally, ECOSMO uses atmospheric nutrient depositions to determine the growth of phytoplankton, which has an influence on the mercury chemistry by reduction of Hg2+. Especially in the North Sea phytoplankton can have a large influence on the oceanic mercury chemistry. Finally meteorological fields are used to determine the concentration dependent flux of mercury between the ocean and the atmosphere.

Because the ocean can be a source as well as a sink for mercury the spatial resolution provided by a three-dimensional ocean model is expected to enhance our capability of modelling atmospheric mercury concentrations. The coupled model system will be presented and the impact of the oceanic mercury emissions on the atmospheric transport and deposition of mercury will be demonstrated.

MG4A-P12 — 11:00-12:00 and 17:30-18:30
TROPICAL AND SUBTROPICAL BRAZILIAN MOUNTAINS AS CONVERSION ZONE OF ATMOSPHERIC MERCURY DEPOSITION
Authors: MEIRE, Rodrigo O1, ALMEIDA, Ronaldo2, MIRANDA, Marcio R2, BASTOS, Wanderley R 2, TORRES, João P M1, MALM, Olaf1
(1) Federal University of Rio de Janeiro, romeire@biof.ufrj.br; (2) Federal University of Rondonia;

Mountainous areas are considered one of the most pristine and remote ecosystems worldwide. However, mountains and uplands are subject to the atmospheric deposition of persistent toxic substances (PTS) which include mercury and other semi volatile compounds.

Generally, PTS transport from emission sources are controlled by climate and geographical parameters like mountain winds, precipitation rates and low temperatures. In tropical and subtropical mountain areas, it is believed that the precipitation rates and also the soil re-emissions could have an important role in the atmospheric deposition of some these pollutants.

This study investigated the total Hg behaviour along altitudinal variations in the tropical and subtropical Brazilian mountains. This work included two National Parks situated in the southeastern (National Park of Serra dos Órgãos, PNSO - Rio de Janeiro State) and in the southern (National Park of São Joaquim, PNSJ – Santa Catarina State) parts of Brazil without historic of regional mercury contamination. Soils samples (10 cm deep) were collected following vertical gradients sites (meters above sea level – masl) for both National Parks (PNSO 400-2200 masl; PNSJ 600-1800 masl) during 2007 and 2008. After field studies, total Hg concentrations in soil samples were carried out by cold vapor atomic absorption spectrophotometry (FIMS-400, Perkin-Elmer).

As a result, the concentrations of total Hg in soil reported in this study for both National Parks are considered very high levels (>100 ng.g-1 d.w.) and in some causes could be similar when compared with contaminated soils as those from gold mining activities, especially in the Amazon basin, Brazil. A Spearman test (p<0.05) reported a strong positive correlation between concentrations of total Hg in soils and altitude for both National Parks investigated. Generally speaking, the highest soil concentrations were found mainly at remote sites above 1500 masl which may indicate a long range atmospheric transport of mercury, probably from lowland sources and soil re-emissions. These results reinforce the potential of mountainous regions as conversion zones for atmospheric mercury deposition and soil acting as a sink of persistent toxic substance.

MG4A-P13 — 11:00-12:00 and 17:30-18:30
ROLE OF CLIMATE AND LOCAL EMISSION SOURCES IN THE WET DEPOSITION OF MERCURY AND MAJOR IONS IN THE PENSACOLA BAY REGION
Authors: CAFFREY, Jane M.1, KRISHNAMURTHY, Nishanth2, LANDING, William M.2, BAGUI, Sikha1, BROWN, Jesse1, BAGUI, Subhash1, HOLMES, Christopher D. 3
(1) University of West Florida, jcaffrey@uwf.edu; (2) Florida State University; (3) University of California Irvine.

Event based wet deposition of mercury, trace metals and major ions has been measured at 3 sites in the Pensacola Bay watershed since December 2004. An additional site at Pensacola Beach was added in 2009. Over this period, emissions in the region have changed as a result of increased population growth and power consumption, along with improvements in the major emission source, a coal fired power plant. Interannual variability in sulfate deposition ranges from 1000 mg SO4/m2/y to 2500 mg SO4/m2/y, with a consistent decline at the 3 long term sites in volume weighted concentration and deposition. There is also significant interannual variation in mercury deposition and volume weighted mean concentration, with lower volume weighted mean mercury concentrations in 2008-2009 compared to earlier years. The Hg/SO4 and Hg/NO3 ratios in wet deposition reflect both long term changes in emissions and different types of weather systems in controlling short term variability. The seasonal pattern in Hg/SO4 in precipitation has changed with a Hg/SO4 ratio in summer and fall about twice that of other seasons in 2010 compared to the beginning of our sampling. We have also observed spatial differences in Hg/SO4 and Hg/NO3 ratios among our sites and nearby National Atmospheric Deposition Program and Mercury Deposition Network sites, with lower ratios at the Beach site and rural site compared to more urban sites.

MG4A-P14 — 11:00-12:00 and 17:30-18:30
ANALYSIS OF TEMPORAL VARIATION AND SOURCE-RECEPTOR RELATIONSHIP OF AMBIENT MERCURY IN THE OHIO RIVER VALLEY REGION
Authors: KIM, Myoungwoo 1, CONLEY, Gary 2, GOSH, Saikat2, CRIST, Kevin2
(1) Ohio EPA, kimmohio@gmail.com; (2) Ohio University;

Gaseous elemental mercury (GEM) has been found to be predominant species of total airborne atmospheric mercury and its life time believed to be between 6 and 24 months (Weiss-Penzias et al., 2003) before it oxidizes, which means that it can be transported globally (Jaffe et al., 2005). Natural emissions and reemissions of mercury were found to be mainly GEM (Mason and Sheu, 2002). 60-70% of anthropogenic mercury emissions are GEM (Carpi, 1997; Streets et al., 2005; Swartzendruber, 2006) and about 56% of the global anthropogenic emissions are from Aisa (Pacyna and Pacyna, 2002; Pacyna et al., 2003). The Ohio University comprehensive monitoring site is located in Athens, Ohio, a rural area that receives both global anthropogenic mercury emissions from long-range transport and regional emissions in the vicinity of Ohio River valley region. Ohio River valley (ORV) region is characterized by a high number of coal-fired power plants, mining activities and industrial plants. The objective of this research is to characterize temporal variation of mercury concentrations (atmospheric and wet deposition); evaluate source-receptor relationship of the mercury species; and identify source locations. Hourly-averaged concentrations of ambient mercury species including elemental mercury (Hg0), reactive gaseous mercury (RGM), and particulate mercury (Hgp) were obtained using Tekran mercury speciation units every other hour. Temporal variation and meteorological analyses suggested that strong seasonality was observed in the temporal trends of ambient mercury species and mixing boundary layer dynamics determined the diurnal trends of mercury. Principal component analysis (PCA), positive matrix factorization (PMF), potential source contribution function (PSCF), and conditional probability function (PCF) were employed to investigate source-receptor relationship and source locations of mercury. PMF result shows that approximately 20% of GEM observed at the monitoring site was attributable to sources associated with coal combustions in the Ohio River Valley region. These results identified in this study provide insights into atmospheric mercury transport from global and regional sources.

MG4A-P15 — 11:00-12:00 and 17:30-18:30
DETERMINATION OF BROMIDE IN NADP/NTN WET DEPOSITION SAMPLES AND ITS SPATIAL AND TEMPORAL CORRELATION WITH NORTH AMERICAN MERCURY WET DEPOSITION
Authors: LEHMANN, Christopher1, GAY, David1, GREEN, Lee1, DOMBEK, Tracy1
(1) University of Illinois, Urbana-Champaign, clehmann@illinois.edu

Bromide is released into the environment via natural and anthropogenic processes. Brominated flame retardants are used widely in a wide variety of products, while methyl bromide is a fumigant applied before and after harvest for a variety of fruits and vegetables. Methyl bromide is classified as an ozone-depleting substance, and its use is strictly regulated and monitored by the U.S EPA. Research has linked bromide oxidation of elemental mercury in the atmosphere to enhanced deposition of mercury to the terrestrial environment. Therefore it is of interest to determine if there is any correlation in time and space between oxidized forms of bromine and mercury wet deposition.

The NADP is evaluating bromide as an additional analyte for its 244-site National Trends Network (NTN) and 7-site Atmospheric Integrated Research Monitoring Network (AIRMoN). Bromide concentrations have been measured in all NTN and AIRMoN samples since June of 2009. Additional funding was provided by the U.S. Geological Survey to evaluate bromide concentrations in NTN archive samples. Archive samples from 2001 and 2002 were selected based upon geographical locations and agricultural activities in those areas. Spatial and temporal trends are evaluated and presented from the data obtained for 2001-2002 and 2009-2010. Initial spatial trends indicate that the highest wet concentrations of bromides are in the Rocky Mountains and along the Gulf and East Coast of North America.

Data from the National Atmospheric Deposition Program/Mercury Deposition Network (NADP/MDN) indicate significant trends have occurred in the deposition of mercury in certain regions of the United States (U.S.). Collocated bromide wet deposition samples are studied to determine whether there exists a relationship between mercury and bromide concentrations.

A rank correlation is evaluated between bromide and mercury concentrations to determine the potential relationship between these species in wet deposition patterns. In general, the highest concentrations of bromide are coincident with mercury concentrations occur in precipitation in regions including the Southeastern U.S. northward through New York State. High bromide to mercury concentrations in precipitation are widely scattered throughout the continental U.S.

MG4A-P16 — 11:00-12:00 and 17:30-18:30
COINCIDENT TRENDS OF MERCURY AND SULFATE CONCENTRATIONS IN WET DEPOSITION MEASUREMENTS FROM THE NATIONAL ATMOSPHERIC DEPOSITION PROGRAM (NADP)
Authors: GAY, David1, LEHMANN, Christopher1
(1) National Atmospheric Deposition Program, dgay@illinois.edu

Data from the National Atmospheric Deposition Program/Mercury Deposition Network (NADP/MDN) indicate significant trends have occurred in the deposition of mercury in certain regions of the United States (U.S.). The NADP/MDN was founded in 1995 to assess long-term spatial and temporal trends in mercury wet deposition, and currently consists of 112 monitoring locations across the U.S. and Canada.

The deposition of mercury to aquatic environments is of concern due to bio-accumulation of mercury in the food chain, with field studies suggesting recent mercury may be more readily incorporated. Research has also shown that sulfur species in aquatic systems may enhance the methylization potential of aquatic systems. Since both Hg and sulfur are emitted through coal combustion, and that oxidized forms of both are deposited as wet deposition, it is important to investigate the relationship between the two.

This study provides a statistical trends analysis (Regional Kendal Trends Test) of long-term mercury wet deposition and their relationship with trends in sulfate deposition, and coincident trends across seasons and regions using collocated data from the NADP’s National Trends Network (NADP/NTN). Rank correlation is evaluated between mercury and sulfate concentrations to determine the relationship between these species.

MG4A-P17 — 11:00-12:00 and 17:30-18:30
SEASONAL VARIATION AND SPATIAL DISTRIBUTION OF GASEOUS ELEMENTAL MERCURY AND PARTICULATE MERCURY IN AN INDUSTRIAL CITY
Authors: JEN, Yi-Shiu1, TSAI, Cheng-Mou1, YUAN, Chung-Shin1, LIN, Yuan-Chung1, LEE, Chang-Gai2
(1)Institute of Environmental Engineering, National Sun Yet-sen University, rock.jay@yahoo.com.tw; (2) Deaprtment of Environmental Resource Management, Taijen University.

This study investigated the seasonal variation and spatial distribution of gaseous and particulate mercury in the atmosphere of Kaohsiung City, the largest industrial city in Taiwan, located at the coastal region of southern Taiwan. Gaseous elemental mercury (GEM) and particulate mercury (Hgp) were simultaneously measured at six sampling sites and one background site by a newly issued method for sampling and analysis of GEM and Hgp in Taiwan (NIEA A304.10C), mainly adopted from USEPA Method IO-5, from June to November, 2010. Field measurement results showed that the seasonal averaged concentrations of GEM and Hgp were in the range of 2.41-9.00 and 0.01-0.59 ng/m3, respectively. The highest concentrations of GEM and Hgp were 9.87 and 0.69 ng/m3, respectively. Moreover, the major partition of atmospheric mercury was GEM, apportioned as 93.86-99.48% GEM and 0.52-6.14% Hgp. As a whole, the concentrations of atmospheric mercury species were generally higher in the drought season (September-November, 2010) than those in the raining season (June-August, 2010). The hot spots of atmospheric mercury were allocated at two regions in Kaohsiung City, including a steel industrial complex in the south and a petrochemical industrial complex in the north.

MG4A-P18 — 11:00-12:00 and 17:30-18:30
GLOBAL MODELING FRAMEWORK GLEMOS: APPLICATION TO MERCURY ATMOSPHERIC SIMULATIONS AND EVALUATION OF CHEMICAL MECHANISMS
Authors: TRAVNIKOV, Oleg1, ILYIN, Ilia1
(1)Meteorological Synthesizing Centre - East of EMEP, oleg.travnikov@msceast.org

Global modeling framework GLEMOS (Global EMEP Multi-media Modeling System) is a multi-scale multi-pollutant simulation platform recently developed for operational and research applications within the EMEP programme under the UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP). The framework allows simulation of dispersion and cycling of different pollutants classes (mercury and other heavy metals, POPs etc.) in the environment with a flexible choice of simulation domain from global to regional scale. Beside, the framework supports multi-media description of the pollutants cycling in the environment. Flexible modular architecture allows flexible configuration of the model setup for particular pollutant properties.

The mercury component of the framework is largely based on the previous well developed and extensively tested hemispheric model MSCE-HM. The current version includes description of major atmospheric processes - emissions to the atmosphere from anthropogenic and natural sources, dispersion and chemical transformations in air and cloud water, scavenging by precipitation and dry deposition to the surface, re-emission to the atmosphere. Chemical transformations include gas-phase and aqueous-phase reactions of mercury with variety of atmospheric chemicals. Besides, intensive mercury oxidation dynamics in the Polar Regions during the atmospheric mercury depletion evens is treated explicitly along with re-emission from snowpack.

The framework was applied for detailed simulation of mercury dispersion and deposition on a global scale and evaluation of different chemical mechanisms governing mercury cycling in the atmosphere. In particular, a number of sensitivity runs was performed with different sets of oxidation kinetics, reaction constants, oxidation products etc. to evaluate relative importance of particular chemical mechanisms under different atmospheric conditions (including free and upper troposphere, continental and marine boundary layer, polar regions etc.). The model performance were evaluated against extensive dataset of speciated mercury measurements collected from literature.

Monday, 25 July, 2011