# Presentation: 211197

## Source-apportionment for atmospheric mercury deposition:Where does the mercury in mercury deposition come from?

**Mark Cohen, Roland Draxler, and Richard Artz**
**NOAA Air Resources Laboratory**
**Silver Spring, Maryland**
_***http://www.arl.noaa.gov/ss/transport/cohen.html***_

**Presentation at USGS, Eastern Region**
**2004 Mercury Workshop, August 17-18, 2004, Reston, VA**
**(revised version January 2005)**

## For many (but not all) aquatic ecosystems,much of the loading comes directly or indirectly through the atmospheric pathway... 

***For the atmospheric pathway:***

**How much of the mercury in atmospheric mercury deposition comes from local, regional, national, continental, and global sources?**
**How important are different source types?**

## 1. The impact of any given mercury emissions source on any receptor is highly variable 

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***1. The impact of any given mercury emissions source on any receptor is highly variable***** **

**extreme spatial and temporal variations**
**Think about the weather and then add all the chemistry and physics of mercury’s interactions with the “weather”**

## 2. The impact of any given mercury emissions source on any receptor is highly dependent on the “type” of mercury emitted 

**Elemental mercury - Hg****0**** - is not readily dry or wet deposited, and its conversion to ionic Hg or Hg(p) is relatively slow**
**Particulate mercury – Hg(p) - is moderately susceptible to dry and wet deposition**
**Ionic mercury – also called Reactive Gaseous Mercury or RGM – is very easily dry and wet deposited**
***Conversion of RGM to Hg******0****** in plumes*****?**

## Example simulation of the atmospheric fate and transport of mercury emissions:

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**Example simulation of the atmospheric fate and transport of mercury emissions:**

** ****hypothetical 1 kg/day source of **
**	****RGM, Hg(p) or Hg(0)**
** ****source height 250 meters**
** ****results tabulated on a 1****o**** x 1****o ****receptor grid**
** ****annual results (1996)**

## Slide 6

## 1o x 1o grid 

- 1o x 1o grid
- over entire
- modeling
- domain

## Results tabulated on a 1o  x 1o grid

- Results tabulated on a 1o  x 1o grid
- over model domain

- Daily values for each grid square will be shown as “ug/m2-year”
- as if the deposition were to continue at that particular daily rate for an entire year

- Daily values for May 1996 will be shown (julian days 121-151)

**And now for the movie...**

## For emissions of Hg(0)

## For emissions of Hg(p)

## For emissions of Hg(II)

## Estimated Speciation Profile for 1999 U.S.Atmospheric Anthropogenic Mercury Emissions 

**Very uncertain for most sources**

##  Estimated 1999 U.S. Atmospheric Anthropogenic Mercury Emissions

## Each type of source has a very different emissions speciation profile

- <date/time>

**Each type of source has a very different emissions speciation profile**
**Even within a given source type, there can be big differences – depending on process type, fuels and raw materials, pollution control equipment, etc.**

## 3. There can be large local and regional impacts from any given source 

- <date/time>

***3. There can be large local and regional impacts from any given source***** **

**same hypothetical 1 kg/day source of RGM**
**source height 250 meters**
**exactly the same simulation, but results tabulated on a 0.1****o**** x 0.1****o ****receptor grid**
**overall results for an entire year (1996)**

## 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

- source
- location

## Slide 18

## Slide 19

## Slide 20

## Slide 21

## 4. At the same time, medium to long range transport can’t be ignored

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***4. At the same time, medium to long range transport can’t be ignored***

## Slide 23

## Slide 24

## Slide 25

## 5. There are a lot of sources...

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***5. There are a lot of sources...***

**Large spatial and temporal variations**
**Each source emits mercury forms in different proportions**
**A lot of different sources can contribute significant amounts of mercury through atmospheric deposition to any given receptor**

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

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

## 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 29

## 6. Getting the source-apportionment information we all want is difficult

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***6. Getting the source-apportionment information we all want is difficult***

**With measurements alone, generally impossible**
**Coupling measurements with back-trajectory analyses yields only a little information**
**Comprehensive fate and transport modeling – “forward” from emissions to deposition – holds the promise of generating detailed source-receptor information**

## 7. There are a lot of uncertainties in current comprehensive fate and transport models

- <date/time>

***7. There are a lot of uncertainties in current comprehensive fate and transport models***

** ****atmospheric chemistry of mercury**
** ****concentrations of key reactants**
** ****mercury emissions (amounts & speciation profile)**
** ****meteorological data (e.g., precipitation)**

## 8. Nevertheless, many models seem to be performing reasonably well, i.e., are able to explain a lot of what we see

- <date/time>

***8. Nevertheless, many models seem to be performing reasonably well, i.e., are able to explain a lot of what we see***

## 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**

## Slide 34

## Slide 35

## 9. A model does not have to be perfect in order to be useful

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***9. A model does not have to be perfect in order to be useful***

**Often, most decisions just require qualitatively reasonable results**
**And realistically, m****ost if not all data and information used in decision-making has uncertainties **
**	****(e.g., public health impacts, economic impacts)**
**So, we shouldn’t demand perfection of models**

## Modeling needed to help interpret measurements and estimate source-receptor relationships

**Modeling needed to help interpret measurements and estimate source-receptor relationships**

**Monitoring needed to develop models and to evaluate their accuracy**

***10. To get the answers we need, we need to use both monitoring and modeling -- ***_***together***_

## 11. MDN is GREAT!...but there are some big gaps in atmospheric monitoring – making it very difficult to evaluate and improve models

**We desperately need national MDN-like network to measure ambient air concentrations of Hg0, Hg(p), and RGM, *****with readily available data***** **
**What is RGM? What is Hg(p)?**
**Both “background/regional” *****and***** near-source measurements needed...**
**Measurements at different heights in the atmosphere**

## Dry Deposition? 

- <date/time>

***Dry deposition is important, and difficult – if not impossible – to measure reliably with current techniques...****** ***
***Essentially all dry deposition estimates made currently are made by applying models***
***National ambient network of speciated ambient measurements will help to evaluate and improve models of dry deposition ***

- _Dry Deposition?_

## Source-Apportionment

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**Source-Apportionment**
**where does the *****mercury***** in *****mercury deposition***** come from?**

## Source-apportionment answers depend on 

*** ******where***** you are, and**
*** ******when***** you are**

***(and the effects of deposition***
***will be different in each ecosystem)***

## For areas without large emissions sources

**the deposition may be relatively low,**
**but what deposition there is may largely come from natural and global sources**
_**For areas **__***with large emissions sources***_
**the deposition will be higher**
**and be more strongly influenced by these large emissions sources...**

## Mercury deposition at selected receptors arising from 1999 base-case emissions from anthropogenic sources in the United States and Canada (IPM coal fired plants are large coal-fired plants in the U.S. only) 

**Mercury deposition at selected receptors arising from 1999 base-case emissions from anthropogenic sources in the United States and Canada ****(IPM coal fired plants are large coal-fired plants in the U.S. only) **

## Example of modeling results:

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**Example of modeling results:**
**Chesapeake Bay**

## 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

## Distance Range from the Chesapeake Bay (km)

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

## Conclusions