2004 Progress Report: Simulations of the Emission, Transport, Chemistry and Deposition of Atmospheric Mercury in the Upper Gulf Coast Region

EPA Grant Number: R831276C012
Subproject: this is subproject number 012 , established and managed by the Center Director under grant CR831276
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Gulf Coast HSRC (Lamar)
Center Director: Ho, Tho C.
Title: Simulations of the Emission, Transport, Chemistry and Deposition of Atmospheric Mercury in the Upper Gulf Coast Region
Investigators: Lin, Jerry , Ho, Tho C. , Chu, Hsing-wei
Institution: Lamar University
EPA Project Officer: Lasat, Mitch
Project Period: December 1, 2003 through November 30, 2004
Project Period Covered by this Report: December 1, 2003 through November 30, 2004
Project Amount: Refer to main center abstract for funding details.
RFA: Gulf Coast Hazardous Substance Research Center (Lamar University) (1996) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research

Objective:

Mercury is a persistent air pollutant (0.5-2 years of atmospheric lifetime) that poses a thread to human health through surface water contamination and subsequent bioaccumulation. The health effects caused by ambient exposure and ingestion of mercury compounds through food chain have been documented in the Mercury Report to Congress. Although there is a plausible link between mercury deposition flux and anthropogenic emissions, the question on whether or not anthropogenic ambient emission can be proportional to the mercury input to the biosphere and its consequences to human exposure remain uncertain. Furthermore, numerous studies have suggested that biogenic mercury emission can dominate those from anthropogenic sources, especially in summer season. This raises the question if the biogenic mercury emission also can pose a human health risk. Because the integration of multiple elements of the mercury pollution problems is complicated and usually generates nonlinear responses, a comprehensive, integrated modeling approach must be undertaken to properly address the questions that affect nearly 300 million people in the United States.

The objective of this research project is to investigate the behavior and assess the contamination pathways of atmospheric mercury using the Community Multiscale Air Quality (CMAQ) modeling system. A suite of coupled physicochemical process models will be employed to evaluate the emission, transport, reactions, and deposition of mercury. The specific objectives of the research project are to: (1) establish multiscale modeling platforms for atmospheric mercury in the Upper Gulf Coast Region; (2) compile the mercury emission inventory using the National Emission Inventory data (NEI99 for hazardous air pollutants), Toxics Release Inventory (TRI 2000), and other point/area source emission factors; (3) develop mercury chemistry modules in both gaseous phase and atmospheric droplets; (4) implement the mercury chemistry modules in CMAQ modeling; (5) simulate dynamically the emission, transport, chemistry, and deposition of atmospheric mercury in the model domains, including the impact of mercury emission control on the mercury budget in the ambient air of the region; and (6) investigate the behavior and assess the contamination pathways of atmospheric mercury using the comprehensive modeling approach in CMAQ.

Progress Summary:

Establishment of High Performance Computation Modeling Platform

A high-performance computational (HPC) platform has been configured for integrated air quality simulations. The platform consists of a 5-node (one master and four slave nodes), 10-CPU (Intel Xeon® grade processor) Linux cluster with RAID-5 network attached storage optimized for parallel computing and massive data storage. The HPC platform will be used for the emission inventory, meteorology, and CMAQ simulations proposed in the study.

Assembling of Model Components

The required modeling components for the simulations of dynamic meteorology, processing of emission inventory, and comprehensive modeling of atmospheric mercury have been assembled successfully. The assembled model components are integrated as the schematic diagram shown in Figure 1 and detailed as follows:

The Integrated Modeling Components Implemented for the Proposed Study

Figure 1. The Integrated Modeling Components Implemented for the Proposed Study

Meteorological Model

The National Center for Atmospheric Research (NCAR)/Pennsylvania State University Mesoscale Scale Model, Version 5, Release 3.6 (MM5V3.6) has been installed, compiled, and tested. The modeling system consists of a number of data preparation processors, postprocessing modules, and the core MM5 model. The installed components include TERRAIN for setting up modeling domains, REGRID for processing large-scale meteorological analysis for initial and boundary conditions, LITTLE_R for preparing observational analysis for data nudging, INTERP_F for converting the data pressure level into sigma level coordinate for MM5 calculation, INTERP_B for converting the data sigma level back to pressure level coordinate during one-way nesting calculation, MM5 for dynamic meteorology simulation, and GRAPH for converting the model output into NCAR graphics-ready format for visualization.

Emission Inventory Model

The most up-to-date Sparse Matrix Operator Kernel Emissions (SMOKE) Modeling System, Version 2.0, has been installed (17 processors) and compiled for the emission inventory modeling tasks proposed in the study. In SMOKE V2.0, the processing of air toxins is included for the spatial and temporal allocations of mercury emission inventory. This version of SMOKE also has improved data flow for easy implementation of new chemical species.

Chemical Transport Model

The most updated version of the CMAQ one-atmosphere model (Version 4.3) has been installed and compiled. The installed components include JPROC for photolysis rate calculation, ICON for initial condition preparation, BCON for boundary condition preparation, MCIP2 for converting MM5 output data into model-ready meteorology, and CCTM for chemical transport simulations in parallel computation mode. The mercury modules are not included in the original model and will be developed in this study.

Collection of Mercury Emission Inventory from Anthropogenic Sources

The required mercury emission inventory from anthropogenic sources has been collected and speciated for 121 source categories from U.S. Environmental Protection Agency (EPA) data archives (NEI99 and TRI) and open literature. The data will be used in the upcoming emission inventory modeling. Table 1 shows a summary of the anthropogenic mercury emission inventory in the continental United States (following the estimates of Seigneur, et al., 2001).

Table 1. Summary of Anthropogenic Mercury Emission in the Continental United States

Source
Categories

Utility Boilers

Waste
Incineration

Misc. Coal Burning

Mining

Chlralkali Facility

Other Sources

Total

Emission (tons/year)

47.9

28.8

12.8

6.4

6.1

30.7

132.7

Completion of Initial Meteorological Simulation

New meteorological simulations have been completed for a 36-km continental United States domain nested into 12-km Upper Gulf Coast domain using MM5V3.6. In the simulation, two-way nesting was used and the modeling period of the TexAQS 2000 study was selected for testing purpose. The meteorological output has been processed using Meteorology-Chemistry Interface Processor (MCIP) Version 2.2 for the emission inventory modeling described in the subsequent sections. Further tuning of the meteorological simulation will be conducted in Year 2 of the project.

Development of a Biogenic Mercury Emission Processor in BEIS3 Framework

For the modeling of atmospheric mercury, the biogenic emission of mercury often has been overlooked. Recent studies, however, have suggested that biogenic mercury may dominate that of anthropogenic sources, especially in the summer season. To include this potentially important emission source in our model simulation, we have developed a prototype emission processor for biogenic mercury emission within the framework of Biogenic Emission Inventory System Version 3.11 (BEIS3). In this development, we incorporated the 230 categories of U.S. Geological Survey (USGS) landuse/landcover/vegetation data to generate the normalized vegetation-specific mercury emission in the 36-km Lambert Conformal grid covering the continental United States. The surface temperature and cloud-cover corrected solar radiation from MM5 meteorology were retrieved and used for temperature and photosynthetic active radiation (PAR) corrections to calculate the diurnal variation of biogenic mercury emission. The implemented mercury emission factors were either evaluated from the mercury flux measurement data published in the literatures for selected tree species and wetland, or assumed for the tree species without mercury flux data. The output from the model is temporally (hourly) and spatially resolved gridded emission in netCDF format ready for applications in Eulerian-based chemical transport models including CMAQ-Hg. Figure 2 shows the data flow of the developed processor.

Data Flow for the Developed Biogenic Mercury Emission Processor

Figure 2. Data Flow for the Developed Biogenic Mercury Emission Processor

Generation of Model-Ready Emission Inventory of Mercury

The complete mercury emission inventory for the entire continental United States has been collected, compiled, and gridded using the most updated SMOKE Version 2.1. In the emissions inventory processing, both anthropogenic and vegetative sources of mercury emission were considered. The anthropogenic emissions including point and area source emissions were based on EPA NEI99 Air Toxin Emission Inventory and TRI 2000 for mercury. A total of 121 source categories were processed and the detailed emission speciation was assigned for each source category. The spatial and temporal allocations were calculated from Multimedia Integrated Modeling System spatial surrogates and EPA standard profile. For vegetative mercury emission estimates, codes were developed within the framework of BEIS3 to process this natural emission inventory. The 230 categories USGS landuse and landcover database (BELD3) were employed to generate the standard mercury emission based on the emission factor calculated from ambient mercury flux measurement (Lin, et al., 2005). The surface temperature and radiation were extracted from MM5 meteorological fields for emission correction. Figure 3 shows the month-by-month comparison of anthropogenic and vegetative mercury emissions for elemental mercury (Hg0), divalent gaseous mercury (HgIIGAS), and particulate mercury (PHg). It can be seen that the vegetative mercury emission can rival the anthropogenic emission in summer months. The gridded, merged anthropogenic mercury emission is shown in Figure 4.

Implementation of Mercury Dry Deposition Modules in CMAQ Modeling Framework

We have developed a new deposition velocity scheme for both gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) based on Wesley’s formulation of dry deposition with pertinent physical properties of GEM and RGM including Henry’s constants, surface reactivity, and gaseous phase diffusivity. The dry deposition velocity was calculated through a resistance model considering the aerodynamic, quasilaminar layer, and canopy resistances. The estimated deposition velocity for GEM is less than 0.1 cm/second. The deposition velocity of RGM exhibits a strong diurnal variation, with a deposition velocity as high as 3.5 cm/second during midday. The time-dependent deposition velocity was used for calculating the dry mercury deposition flux in CMAQ simulation.

Comparison of Mercury Emission Quantity and Speciation From Anthropogenic and Vegetative Sources in the Continential United States Domain

Figure 3. Comparison of Mercury Emission Quantity and Speciation From Anthropogenic and Vegetative Sources in the Continential United States Domain

The Merged Anthropogenic Mercury Emission Inventory for CMAQ-Hg Model Input

Figure 4. The Merged Anthropogenic Mercury Emission Inventory for CMAQ-Hg Model Input

Science Updates of the Mercury Chemistry Model

New science components have been added to the mercury model of CMAQ modeling system to simulate the emission, transport, transformation and deposition of mercury in three different forms: GEM, RGM, and PHg. The new science components include: (1) product speciation and distribution of gaseous phase oxidation of GEM, (2) modification of aqueous phase sorption of dissolved Hg(II) to the insoluble particulate in atmospheric droplets, (3) modification of gaseous reaction rate constants according to new kinetic data, and (4) inclusion of additional gaseous oxidation by reactive halogens. The updated chemical reactions of mercury are listed in Table 2.

Table 2. The Chemical Mechanism Implemented in the CMAQ-Hg Model

Reaction

Rate constant

Hg0(g) + O3(g) Hg0(s, g) + O2(g)

3-75×10-20 cm3molec-1s-1

Hg0(aq) + O3(aq) + 2 H + Hg2+(aq) + H2O + O2

4.7×107 M-1 s-1

Hg0(g) + ·OH(g) RGM + Products

8.7×10-14 cm3molec-1s-1

Hg0(aq) + ·OH(aq) Hg2+(aq) + Products

2.0×109 M-1 s-1

Hg0(aq) + HOCl(aq) Hg2+(aq) + Cl- + OH-

2.09×106 M-1s-1

Hg0(aq) + OCl-(aq) + H+ Hg2+(aq) + Cl- + OH-

1.99×106 M-1s-1

Hg0(g) + H2O2(g) PHg + products

8.5´10-19 cm3molec-1s-1

Hg0(g) + Cl2(g) RGM + products

2.6-4.8´10-18cm3molec-1s-1

Hg0(g) + Br2(g) RGM + products

9´10-17 cm3molec-1s-1

Hg0(g) + Cl(g) RGM + products

1.0´10-11 cm3molec-1s-1

Hg0(g) + Br(g) RGM + products

3.2´10-12 cm3molec-1s-1

Hg0(g) + BrO(g) RGM + products

1.5´10-14 cm3molec-1s-1

HgSO3(aq) Hg0(aq) + products

T exp(31.971-(12595/T))s-1

Hg(OH)2(aq) + UV Hg0(aq) + products

3×10-7 s-1, midday 60°N

Hg(II)(aq) + HO2·(aq) Hg+(aq) + O2 + H+

1.7×104 M-1s-1

Implementation of the Updated Mercury Chemistry Model in Parallel CMAQ Framework

CMAQ Version 4.4 is the latest parallel version of CMAQ released in October 2004. We have implemented the mercury chemistry codes that we modified into this release of CMAQ. The major benefits of this implementation are: (1) adding the capability of performing mercury chemical transport simulation in parallel mode, which greatly reduce the computational time, and (2) utilizing the most up-to-date chemical processors in CMAQ to calculate the concentrations of mercury oxidants and reductants.

Completion of Base-Case Simulation for Mercury Deposition in July 2001

To test the modified mercury model, monthly simulations are performed using the gridded emission inventory (for mercury and criterion pollutants) and EPA July 2001 meteorology over a 36-km domain covering the continental United States. The simulated mercury concentration and deposition flux are shown in Figures 5 and 6. It can be seen from Figure 5 that mercury emission does not greatly change GEM level, and high RGM coincides with many ozone-nonattainment areas. This indicates that atmospheric photochemical activity can enhance secondary RGM formation and thus dry mercury deposition. Greater wet mercury deposition flux is observed in the south of the domain (Figure 6).

Modeled Average Concentrations of Gaseous Elemental Mercury and Reactive Gaseous Mercury

Figure 5. Modeled Average Concentrations of Gaseous Elemental Mercury (Left) and Reactive Gaseous Mercury (Right)

Modeled Monthly Wet Deposition of Divalent Mercury and Particulate Mercury

Figure 6. Modeled Monthly Wet Deposition of Divalent Mercury (Left) and Particulate Mercury (Right)

Collection of Field Data of Mercury Deposition for Model Verification

For future model verification purposes, we have collected the measured wet deposition data of mercury recorded from Mercury Deposition Network (MDN) by the National Atmospheric Deposition Program. MDN collects weekly concentrations of total mercury in precipitation and uses the concentration and precipitation data to estimate the seasonal and annual wet deposition flux of total mercury at 88 sites throughout the continental United States. We have performed spatial interpolation of the concentration and deposition flux data to visualize the distribution of mercury wet deposition (Figures 7 and 8) in July 2001. As seen, the highest mercury deposition occurred in Florida and in the eastern Gulf Coast Region because of the great precipitation intensity. This agrees reasonably with our model testing runs (e.g., Figure 6). Further model verification will be performed when data become available in the midwest and west regions of the United States.

The Concentration of Total Mercury in Precipitation Water Over the United States in July 2001

Figure 7. The Concentration of Total Mercury in Precipitation Water Over the United States in July 2001

The Wet Deposition Flux of Mercury Over the United States in July 2001

Figure 8. The Wet Deposition Flux of Mercury Over the United States in July 2001

Future Activities:

The proposed project tasks have been successfully completed according to the original project milestones, with the mercury model tested and all required model inputs (e.g., gridded emission inventory for mercury and other criterion pollutants) generated. These will be incorporated into the modeling works in Year 3. Future project activities will focus on investigating: (1) the effect on simulated mercury deposition from the implemented vegetative mercury emission and new mercury science components, (2) the impact of mercury emission reduction from anthropogenic sources on the dry and wet deposition of mercury, and (3) the effect of long-range and boundary transport on mercury deposition in the Continental United States. The results of the above tasks will be integrated to address the fate and contamination pathways of atmospheric mercury in the upper Gulf Coast Region.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other subproject views: All 8 publications 4 publications in selected types All 4 journal articles
Other center views: All 64 publications 19 publications in selected types All 18 journal articles
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Journal Article Lin C-J, Ho TC, Chu H-W, Yang H, Mojica MJ, Krishnarajanagar N, Chiou P, Hopper JR. A comparative study of US EPA 1996 and 1999 emission inventories in the west Gulf of Mexico coast region, USA. Journal of Environmental Management 2005;75(4):303-313. CR831276 (Final)
R831276C012 (2004)
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  • Journal Article Lin C-J, Pongprueksa P, Bullock Jr. OR, Lindberg SE, Pehkonen SO, Jang C, Braverman T, Ho TC. Scientific uncertainties in atmospheric mercury models II: sensitivity analysis in the CONUS domain. Atmospheric Environment 2007;41(31):6544-6560. CR831276 (Final)
    R831276C012 (2004)
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  • Journal Article Lin C-J, Lindberg SE, Ho TC, Jang C. Development of a processor in BEIS3 for estimating vegetative mercury emission in the continental United States. Atmospheric Environment 2005;39(39):7529-7540. CR831276 (Final)
    R831276C012 (2004)
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  • Journal Article Lin C-J, Pongprueksa P, Lindberg SE, Pehkonen SO, Byun D, Jang C. Scientific uncertainties in atmospheric mercury models I: model science evaluation. Atmospheric Environment 2006;40(16):2911-2928. CR831276 (Final)
    R831276C012 (2004)
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  • Supplemental Keywords:

    atmospheric mercury, emission inventory, chemical mechanism, cloud chemistry, modeling, CAMQ, waste, ecological risk assessment, environmental engineering, hazardous waste, advanced treatment technologies, bioremediation, contaminated waste sites, groundwater contamination, petroleum contaminants, hydrocarbon,, RFA, Scientific Discipline, Air, INTERNATIONAL COOPERATION, Geographic Area, Waste, Ecosystem Protection/Environmental Exposure & Risk, Air Quality, air toxics, Environmental Chemistry, Fate & Transport, Monitoring/Modeling, Hazardous Waste, Environmental Monitoring, Hazardous, Environmental Engineering, Gulf of Mexico, emission control strategies, fate and transport, hazardous waste treatment, atmospheric dispersion models, mercury, fate and transport , emissions monitoring, HAPS, hazardous air pollutants, emissions, modeling, emissions inventory, particulate matter mass, emission control, air pollution control technology, air emissions, atmospheric mercury chemistry, monitoring inorganic chemicals, aerosol analyzers, atmospheric chemistry, atmospheric deposition, mercury vapor

    Relevant Websites:

    http://dept.lamar.edu/gchsrc/ Exit

    Progress and Final Reports:

    Original Abstract
  • Final

  • Main Center Abstract and Reports:

    CR831276    Gulf Coast HSRC (Lamar)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
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    R831276C002 Arsenic Removal and Stabilization with Synthesized Pyrite
    R831276C003 A Large-Scale Experimental Investigation of the Impact of Ethanol on Groundwater Contamination
    R831276C004 Visible-Light-Responsive Titania Modified with Aerogel/Ferroelectric Optical Materials for VOC Oxidation
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    R831276C006 Pollution Prevention through Functionality Tracking and Property Integration
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    R831276C009 Linear Polymer Chain and Bioengineered Chelators for Metals Remediation
    R831276C010 Treatment of Perchlorate Contaminated Water Using a Combined Biotic/Abiotic Process
    R831276C011 Rapid Determination of Microbial Pathways for Pollutant Degradation
    R831276C012 Simulations of the Emission, Transport, Chemistry and Deposition of Atmospheric Mercury in the Upper Gulf Coast Region
    R831276C013 Reduction of Environmental Impact and Improvement of Intrinsic Security in Unsteady-state
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    R831276C015 Improved Combustion Catalysts for NOx Emission Reduction
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    R831276C017 Minimization of Hazardous Ion-Exchange Brine Waste by Biological Treatment of Perchlorate and Nitrate to Allow Brine Recycle
    R831276C018 Integrated Chemical Complex and Cogeneration Analysis System: Greenhouse Gas Management and Pollution Prevention Solutions