# Presentation: 318481

## Modeling the Atmospheric Transportand Deposition of Mercury

**Dr. Mark Cohen**
**NOAA Air Resources Laboratory**
**Silver Spring, Maryland**

**Materials assembled for a discussion with **
**Maryland Department of the Environment, **
**Baltimore MD,  August 25, 2005**

## There are many ways in which mercury is introduced into a given aquatic ecosystem... atmospheric deposition can be a very significant pathway

**Mercury transforms into methylmercury in soils**
** ****and water, then can****bioaccumulate in fish**

**Humans and wildlife affected primarily by**
**eating fish **
**containing mercury**
**Best documented impacts are on the developing fetus:  impaired motor and cognitive skills**

**There are many ways in which mercury is introduced into a given aquatic ecosystem... ****atmospheric deposition can be a very significant pathway**

**atmospheric deposition to the watershed**

**atmospheric deposition directly to the water surface**

## Atmospheric mercury modeling

**Atmospheric mercury modeling**

**What do atmospheric mercury models need from us?**

**Why do we need atmospheric mercury models?**

**Some preliminary results:**
**Model evaluation**
**Source Receptor Information**

## Atmospheric mercury modeling

**Atmospheric mercury modeling**

**What do atmospheric mercury models need from us?**

**Why do we need atmospheric mercury models?**

**Some preliminary results:**
**Model evaluation**
**Source Receptor Information**

## Three “forms” of atmospheric mercury

**Notes:**
To begin, the atmospheric community generally classifies atmospheric mercury into three different “forms” –
First, there is elemental mercury...
Then there is Reactive Gaseous Mercury...
And finally there is particulate mercury...

## Atmospheric Mercury Fate Processes

**Atmospheric Mercury Fate Processes**

## Atmospheric Chemical Reaction Scheme for Mercury

| Reaction | Rate |  | Units | Reference |
| --- | --- | --- | --- | --- |
|     GAS PHASE REACTIONS |  |  |  |  |
| Hg0  + O3   Hg(p) | 3.0E-20 | cm3/molec-sec |  | Hall (1995) |
| Hg0  + HCl  HgCl2  | 1.0E-19 | cm3/molec-sec |  | Hall and Bloom (1993) |
| Hg0  + H2O2  Hg(p)  | 8.5E-19 | cm3/molec-sec |  | Tokos et al. (1998) (upper limit based on experiments) |
| Hg0  + Cl2  HgCl2 | 4.0E-18 | cm3/molec-sec |  | Calhoun and Prestbo (2001) |
| Hg0 +OH  Hg(p) | 8.7E-14 | cm3/molec-sec |  | Sommar et al. (2001) |
|     AQUEOUS PHASE REACTIONS |  |  |  |  |
| Hg0 + O3  Hg+2 | 4.7E+7 | (molar-sec)-1 |  | Munthe (1992) |
| Hg0  + OH  Hg+2 | 2.0E+9 | (molar-sec)-1 |  | Lin and Pehkonen(1997) |
| HgSO3  Hg0 | T*e((31.971*T)-12595.0)/T)    sec-1
[T = temperature (K)] |  |  | Van Loon et al. (2002) |
| Hg(II)  + HO2  Hg0 | ~ 0 | (molar-sec)-1 |  | Gardfeldt & Jonnson (2003) |
| Hg0  + HOCl  Hg+2 | 2.1E+6 | (molar-sec)-1 |  | Lin and Pehkonen(1998) |
| Hg0  + OCl-1  Hg+2 | 2.0E+6 |  (molar-sec)-1 |  | Lin and Pehkonen(1998) |
| Hg(II)     Hg(II) (soot) | 9.0E+2 | liters/gram;
t = 1/hour |  | eqlbrm: Seigneur et al. (1998)
rate: Bullock & Brehme (2002). |
| Hg+2  + h  Hg0 | 6.0E-7 | (sec)-1 (maximum)	 |  | Xiao et al. (1994); 
Bullock and Brehme (2002) |

## NOAA HYSPLIT MODEL

**NOAA HYSPLIT MODEL**

## Slide 9

**Notes:**
This is way we typically run the HYSPLIT model.  We do a run for one particular source location, and we release puffs periodically throughout the year (e.g., once every 7 hours).  We follow each puff and keep track of the dispersion and the fate processes (deposition, transformation, etc.).  The model uses the physical-chemical properties of the pollutant we are modeling, of course. By the end of the year, we have a good idea of the average impact that a source in this location would have on the receptors of interest (e.g., the Great Lakes).

## Geographic Distribution of Largest Anthropogenic Mercury Emissions Sources in the U.S. (1999) and Canada (2000)

**Geographic Distribution of Largest Anthropogenic Mercury Emissions Sources in the U.S. (1999) and Canada (2000)**

## Slide 11

## In principle, we need do this for each source in the inventory

**But, since there are more than 100,000 sources in the U.S. and Canadian inventory, we need shortcuts...**
**Shortcuts described in Cohen *****et al ****Environmental Research* **95**(3), 247-265, 2004

## Cohen, M., Artz, R., Draxler, R., Miller, P., Poissant, L., Niemi, D., Ratte, D., Deslauriers, M., Duval, R., Laurin, R., Slotnick, J., Nettesheim, T., McDonald, J.   “Modeling the Atmospheric Transport and Deposition of Mercury to the Great Lakes.” Environmental Research 95(3), 247-265, 2004.

**Cohen, M., Artz, R., Draxler, R., Miller, P., Poissant, L., Niemi, D., Ratte, D., Deslauriers, M., Duval, R., Laurin, R., Slotnick, J., Nettesheim, T., McDonald, J.**   “Modeling the Atmospheric Transport and Deposition of Mercury to the Great Lakes.” *Environmental Research* **95**(3), 247-265, 2004.
- Note: Volume 95(3) is a Special Issue: "An Ecosystem Approach to Health Effects of Mercury in the St. Lawrence Great Lakes", edited by David O. Carpenter.

## For each run, simulate fate and transport everywhere,

**	****but only keep track of impacts on each selected receptor**
**  ****	****(e.g., Great Lakes, Chesapeake Bay, etc.)**
**Only run model for a limited number (~100) of hypothetical, individual unit-emissions sources throughout the domain**
**Use spatial interpolation to estimate impacts from sources at locations not explicitly modeled**

## 0.1o x 0.1o subgrid 

- 0.1o x 0.1o subgrid
- for
- near-field analysis

## 0.1o x 0.1o subgrid 

- 0.1o x 0.1o subgrid
- for
- near-field analysis

## Slide 17

## Slide 18

## Slide 19

## Slide 20

## Logarithmic

***Logarithmic***

**Why is emissions speciation information critical?**

## Linear

***Linear***

**Why is emissions speciation information critical?**

## Why is emissions speciation information critical?

***Linear***

***Logarithmic***

## Atmospheric mercury modeling

**Atmospheric mercury modeling**

**What do atmospheric mercury models need from us?**

**Why do we need atmospheric mercury models?**

**Some preliminary results:**
**Model evaluation**
**Source Receptor Information**

## Why do we need atmospheric mercury models?

- to get *comprehensive source attribution* information ---
- 	**we don’t just want to know how much is depositing at any given location, we also want to know where it came from...**
- to estimate *deposition over large regions, *
*	**...*because deposition fields are highly spatially variable,
- 	and one can’t measure everywhere all the time...
- to estimate *dry deposition*
- to evaluate *potential consequences* of alternative future emissions scenarios

## Atmospheric mercury modeling

**Atmospheric mercury modeling**

**What do atmospheric mercury models need from us?**

**Why do we need atmospheric mercury models?**

**Some preliminary results:**
**Model evaluation**
**Source Receptor Information**

## What do atmospheric mercury models need?

**Inventories**

**Meteorological**
**Data**

**Scientific understanding of**
**phase partitioning, **
**atmospheric chemistry, **
**and deposition processes**

**Ambient data for comprehensive model evaluation and improvement**

**What do atmospheric mercury models need?**

## Slide 28

|  | some challenges facing mercury modeling |
| --- | --- |
| emissions inventories |  need all sources
 accurately divided into different Hg forms
 U.S. 1996, 1999, 2003 / CAN 1995, 2000, 2005 
 temporal variations (e.g. shut downs) |
| meteorological data |  precipitation not well characterized |
| scientific understanding | what is RGM? what is Hg(p)?
accurate info for known reactions? 
do we know all significant reactions?
natural emissions, re-emissions? |
| ambient data for model evaluation |  Mercury Deposition Network (MDN) is great, but:
 also need RGM, Hg(p), and Hg(0) concentrations
 also need data above the surface (e.g., from aircraft)
 also need source-impacted sites (not just background) |

## Slide 29

## Slide 30

|  | some challenges facing mercury modeling |
| --- | --- |
| emissions inventories |  need all sources
 accurately divided into different Hg forms
 U.S. 1996, 1999, 2003 / CAN 1995, 2000, 2005
 temporal variations (e.g. shut downs)  |
| meteorological data |  precipitation not well characterized |
| scientific understanding | what is RGM? what is Hg(p)?
accurate info for known reactions? 
do we know all significant reactions?
natural emissions, re-emissions? |
| ambient data for model evaluation |  Mercury Deposition Network (MDN) is great, but:
 also need RGM, Hg(p), and Hg(0) concentrations
 also need data above the surface (e.g., from aircraft)
 also need source-impacted sites (not just background) |

## Slide 31

|  | some challenges facing mercury modeling |
| --- | --- |
| emissions inventories |  need all sources
 accurately divided into different Hg forms
 U.S. 1996, 1999, 2003 / CAN 1995, 2000, 2005 
 temporal variations (e.g. shut downs) |
| meteorological data |  precipitation not well characterized |
| scientific understanding | what is RGM? what is Hg(p)?
accurate info for known reactions? 
do we know all significant reactions?
natural emissions, re-emissions? |
| ambient data for model evaluation |  Mercury Deposition Network (MDN) is great, but:
 also need RGM, Hg(p), and Hg(0) concentrations
 also need data above the surface (e.g., from aircraft)
 also need source-impacted sites (not just background) |

## Slide 32

|  | some challenges facing mercury modeling |
| --- | --- |
| emissions inventories |  need all sources
 accurately divided into different Hg forms
 U.S. 1996, 1999, 2003 / CAN 1995, 2000, 2005 
 temporal variations (e.g. shut downs) |
| meteorological data |  precipitation not well characterized |
| scientific understanding | what is RGM? what is Hg(p)?
accurate info for known reactions? 
do we know all significant reactions?
natural emissions, re-emissions? |
| ambient data for model evaluation |  Mercury Deposition Network (MDN) is great, but:
 also need RGM, Hg(p), and Hg(0) concentrations
 also need data above the surface (e.g., from aircraft)
 also need source-impacted sites (not just background) |

## Atmospheric mercury modeling

**Atmospheric mercury modeling**

**What do atmospheric mercury models need from us?**

**Why do we need atmospheric mercury models?**

**Some preliminary results:**
**Model evaluation**
**Source Receptor Information**

##  EMEP Model Intercomparison

-  Phase II – ambient concentrations
-  Phase III – wet and dry deposition
-  Chesapeake Bay region

##  EMEP Model Intercomparison

-  Phase II – ambient concentrations
-  Phase III – wet and dry deposition
-  Chesapeake Bay region

## Slide 36

## Measured and Simulated Total Gaseous Mercury at Neuglobsow during the 1995 episode

## Slide 38

## Slide 39

## Slide 40

## Slide 41

##  EMEP Model Intercomparison

-  Phase II – ambient concentrations
-  Phase III – wet and dry deposition
-  Chesapeake Bay region

## Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site DE_02 during 1996

**Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site DE_02 during 1996**

## Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site MD_13 during 1996

**Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site MD_13 during 1996**

## Summer 2004 Chesapeake Bay Atmospheric Hg Study(June – August 2004)

- NOAA Cooperative Oxford Lab: ***Bob Wood***
- NOAA Air Resources Lab Atmospheric Turbulence and Diffusion Division (ATDD): ***Steve Brooks***
- NOAA Air Resources Lab HQ Division: ***Winston Luke, Paul Kelley, ******	******	******	******	******	******Mark Cohen,  Richard Artz***
- NOAA Chesapeake Bay Office: ***Maggie Kerchner***
- Frontier GeoSciences: ***Bob Brunette, Gerard van der Jagt, Eric Prestbo***
- Univ. of MD Wye Res. and Educ. Center: ***Mike Newall***

## Summer 2004 Measurement Sites

**Summer 2004 Measurement Sites**

## Slide 47

## Summer 2004 Chesapeake Bay Atmospheric Hg Study(June – August 2004)

|  | Oxford | Wye |
| --- | --- | --- |
| Event-based precipitation samples analyzed for Hg |  |  |
| Speciated Hg concentrations in ambient air (RGM, Hg(p), Hg0) |  |  |
| Ambient concentration of ozone and sulfur dioxide | 
(continuous) |  
(weekly via AirMON Dry) |
| Ambient concentration of carbon monoxide |  |  |
| Meteorology |  |  
(via NADP/NTN site) |
| Major ions in precipitation |  |  
(via NADP/NTN site) |

**Summer 2004 Chesapeake Bay Atmospheric Hg Study****(June – August 2004)**

## Atmospheric mercury modeling

**Atmospheric mercury modeling**

**What do atmospheric mercury models need from us?**

**Why do we need atmospheric mercury models?**

**Some preliminary results:**
**Model evaluation**
**Source Receptor Information**

## Example of

**Detailed Results:**
**1999 Results for**
**Chesapeake Bay**

## Geographical Distributionof 1999 Direct Deposition Contributions to the Chesapeake Bay (entire domain)

- Geographical Distributionof 1999 Direct Deposition Contributions to the Chesapeake Bay (entire domain)

## Geographical Distribution of 1999 Direct Deposition Contributions to the Chesapeake Bay (regional close-up)

## Geographical Distribution of 1999 Direct Deposition Contributions to the Chesapeake Bay (local close-up)

## Largest Regional Individual Sources Contributing to1999 Mercury Deposition Directly to the Chesapeake Bay

**Largest Regional Individual Sources Contributing to****1999 Mercury Deposition Directly to the Chesapeake Bay**

## Largest Local Individual Sources Contributing to1999 Mercury Deposition Directly to the Chesapeake Bay

**Largest Local Individual Sources Contributing to****1999 Mercury Deposition Directly to the Chesapeake Bay**

## Emissions and Direct Deposition Contributions from Different Distance Ranges Away From the Chesapeake Bay

## Top 25 Contributors to 1999 Hg Deposition Directly to the Chesapeake Bay

## Preliminary Results for other Maryland

**Receptors**

## Maryland Receptors Included in Recent Preliminary HYSPLIT-Hg modeling (but modeling was not optimized for these receptors!)

- Maryland Receptors Included in Recent Preliminary HYSPLIT-Hg modeling *(but modeling was not optimized for these receptors!)*

## Largest Modeled Atmospheric Deposition Contributors Directly to Deep Creek Lake based on 1999 USEPA Emissions Inventory (national view)

## Largest Modeled Atmospheric Deposition Contributors Directly to Deep Creek Lake based on 1999 USEPA Emissions Inventory (regional view)

## Largest Modeled Atmospheric Deposition Contributors Directly to Deep Creek Lake based on 1999 USEPA Emissions Inventory (close-up view)

- Largest Modeled Atmospheric Deposition Contributors Directly to Deep Creek Lake based on 1999 USEPA Emissions Inventory (close-up view)

## Some Next Steps

## Conclusions

## EXTRA SLIDES

## Why might the atmospheric fate of mercury emissions be essentially linearly independent?

**Hg won’t affect meteorology  (can simulate meteorology independently, and  provide results to drive model)**

**Most species that complex or react with Hg are generally present at *****much***** higher concentrations than Hg**

**Other species (e.g. OH) generally react with many other compounds than Hg, so while present in trace quantities, their concentrations cannot be strongly influenced by Hg**

**The current “consensus” chemical mechanism (equilibrium + reactions) does not contain any equations that are not 1****st**** order in Hg**

**Wet and dry deposition processes are generally 1****st**** order with respect to Hg**

**Why might the atmospheric fate of mercury emissions be essentially linearly independent?**

## Spatial interpolation

**RECEPTOR**

**Impacts from**
**Sources 1-3**
**are Explicitly**
**Modeled**

- 2

- 1

- 3

## Perform separate simulations at each location for emissions of pure Hg(0), Hg(II) and Hg(p) 

**	****[*****after emission, simulate transformations between Hg forms*****]**
**Impact of emissions mixture taken as a linear combination of impacts of pure component runs on any given receptor **

## =

**Impact of Source**
**Emitting**
**30% Hg(0)**
**50% Hg(II)**
**20% Hg(p)**

**=**

**Impact of Source Emitting Pure Hg(0)**

**0.3 x**

**Impact of Source Emitting Pure Hg(II)**

**0.5 x**

**Impact of Source Emitting Pure Hg(p)**

**0.2 x**

**+**

**+**

## Slide 70

## Standard Source Locations in Maryland region during recent simulation