Mercury in the Atmosphere Thomas M. Holsen Clarkson University - - PowerPoint PPT Presentation

Mercury in the Atmosphere

Thomas M. Holsen – Clarkson University

Outline Outline

• Sources of Atmospheric Hg

Sources of Atmospheric Hg

• Anthropogenic

Anthropogenic vs vs natural natural

• Anthropogenic sources

Anthropogenic sources

• Forms of Hg in the atmosphere

Forms of Hg in the atmosphere

• Hg concentrations in NYS

Hg concentrations in NYS

• Hg deposition processes

Hg deposition processes Acknowledgements Acknowledgements – – C Driscoll, M Cohen, NY DEC, YJ C Driscoll, M Cohen, NY DEC, YJ Han, S Lai, J Han, S Lai, J Pagano Pagano, M Milligan , M Milligan

Global Sources of Mercury Global Sources of Mercury to the Atmosphere (in metric tons per year) to the Atmosphere (in metric tons per year)

Source Source Seigneur et Seigneur et

• al. 2004
• al. 2004

Bergan Bergan et al. et al. 1999 1999 Mason & Mason & Sheu Sheu 2002 2002 Direct Anthropogenic Direct Anthropogenic 2143 2143 2160 2160 2400 2400 Recycled Anthropogenic Recycled Anthropogenic 2134 2134 2000 2000 2090 2090 Total Anthropogenic 4277 4160 4490 Natural Natural 2134 2134 1900 1900 2110 2110 Total (% of Anthropogenic Origin) 6411 (67%) 6060 (69%) 6600 (68%) from C. Driscoll

U.S. Emissions of Mercury

50 100 150 200 250 TPY 1990 Emissions 1996 Emissions 1999 Emissions

Other Non-MACT Other MACT Hazardous Waste Incineration Chlorine Production Industrial Boilers Municipal Waste Combustors Medical Waste Incinerators Utility Coal Boilers

210 185 118

U.S. Anthropogenic Emissions of Mercury

Source: EPA 1990, 1996 NTI and EPA 1999 NEI. Short tons per year.

From M. Cohen

Based on 1999 NEI

From YJ Han

Atmospheric Mercury Species Atmospheric Mercury Species

Elemental Mercury (Hg0)

Predominant species, Long range transport Globally distributed, 0.5 to 2 years residence time

Gaseous divalent mercury (RGM, Hg2+, )

Oxidized mercury: Hg(II) : HgCl2, other species? Highly water soluble -> short atmospheric life time (0.5-2 days) Local and Regional effects

Particulate Mercury (Hgp)

Species largely unknown – probably Hg(II) Local and Regional Effects (0.5-2 days)

Estimated Speciation Profile for U.S. Estimated Speciation Profile for U.S. Atmospheric Mercury Emissions (1999) Atmospheric Mercury Emissions (1999)

RGM

Simplified Mercury Cycle from C. Driscoll

Hg sampling sites in NYS Hg sampling sites in NYS

+ Potsdam

+ Sterling

+ Stockton

Potsdam and Stockton funded by NYSERDA, Potsdam and Stockton funded by NYSERDA, Sterling by US EPA Sterling by US EPA

Sterling, NY Sterling, NY

Between Oswego and Rochester on a bluff overlooking the lake

Manual Air Sampling Manual Air Sampling

TGM: Adsorption into Gold traps RGM: Annular Denuder coated by KCl

Monthly Average TGM Concentrations, ng/m Monthly Average TGM Concentrations, ng/m3

Date

May 00 July 00 May 01 July 01 Sep 01 Nov 01 Jan 02 Mar 02 May 02 July 02 Sep 02 Nov 02 Jan 03 Mar 03

TVM Concentrations (ng m-3)

• 6
• 4
• 2

2 4 6 8 10 12 Stockton site Potsdam site Sterling site

Daily TGM Concentrations, ng/m Daily TGM Concentrations, ng/m3

3

TGM Concentration

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 12/6/1999 4/19/2001 9/1/2002 1/14/2004 5/28/2005 10/10/2006 Date Concentration, ng m-3 Potsdam Stockton Sterling

Daily RGM Concentrations, pg/m Daily RGM Concentrations, pg/m3

3

RGM Concentration

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 Date 5/14/2002 7/7/2002 8/30/2002 10/11/2002 12/4/2002 1/27/2003 3/22/2003 5/15/03 7/8/03 8/31/03 10/24/03 12/17/03 2/9/04 Date Concentration, pg m-3 Potsdam Stockton Sterling

Computation of Trajectories Computation of Trajectories -

• HYSPLIT4

HYSPLIT4

• NOAA Model

NOAA Model

• Predicts history of

Predicts history of air movement air movement

Potential Source Contribution Function Potential Source Contribution Function (PSCF) (PSCF)

Sampling site Cell 1 Cell 1 Cell 2 Cell 2 Back-trajectory representing high concentration PSCF value Cell 1 = 2/3 Cell 2 = 0/2 Back-trajectory representing low concentration

JP JP-

• PSCF result for TGM measurements taken in Potsdam,

PSCF result for TGM measurements taken in Potsdam, Stockton, and Sterling in NY Stockton, and Sterling in NY

Tekran Automated Speciation System –

highly time resolved concentrations

Hg concentrations obtained with a Hg concentrations obtained with a Tekran Speciation System Tekran Speciation System

05/14/05 05/18/05 05/22/05 05/26/05 05/30/05 06/03/05 06/07/05 06/11/05 06/15/05 06/19/05 06/23/05 06/27/05 07/01/05 07/05/05 07/09/05

Elemental Hg [ng m-3]

0.0 0.5 1.0 1.5 2.0 2.5 3.0

RGM & Particulate Hg [pg m-3]

• 2

2 4 6 8 10 12 14 Elemental Hg Reactive gaseous Hg Particulate Hg

Relationship between Relationship between Hg and SO Hg and SO2

2

concentrations in concentrations in Rochester, NY Rochester, NY Data from NY DEC Data from NY DEC

Hg Deposition Processes Hg Deposition Processes

• Wet deposition

Wet deposition – – Hg associated with rain, dew, Hg associated with rain, dew, snow, fog (mostly RGM) snow, fog (mostly RGM)

• Particle dry deposition

Particle dry deposition – – Hg associated with Hg associated with atmospheric particles (mostly RGM) atmospheric particles (mostly RGM)

• Air

Air-

• surface exchange (water and vegetation)

surface exchange (water and vegetation)

• RGM deposition only

RGM deposition only

• Hg(0) deposition and emission

Hg(0) deposition and emission

Deposition Processes

Air-water exchange Wet deposition (RGM, Hg(p)) Dry particle deposition (Hg(p)) Wet and dry deposition, stomata uptake RGM, Hg(0) RGM → Hg(0) Hg(0) litterfall throughfall

Mercury Deposition Mercury Deposition

• Predominant source of mercury in most

Predominant source of mercury in most watersheds is atmospheric deposition ( watersheds is atmospheric deposition (Lindqvisit Lindqvisit et al. 1991; Mason 1994). et al. 1991; Mason 1994).

• Deposition of mercury has increased two to three

Deposition of mercury has increased two to three-

• fold over the past two centuries, with some

fold over the past two centuries, with some locations exhibiting greater than a twenty fold locations exhibiting greater than a twenty fold increase ( increase (Meili Meili 2003; 2003; Nriaguand Nriaguand Becker 2003). Becker 2003).

From C. Driscoll

Historical deposition of mercury to sediments in West Pond and Historical deposition of mercury to sediments in West Pond and Little Echo Pond in the Adirondack region ( Little Echo Pond in the Adirondack region (Lorey Lorey and Driscoll, and Driscoll, 1999) 1999)

Regional and Global Contributions to Total Hg Regional and Global Contributions to Total Hg Deposition to the Catskill, NY Receptor Site Deposition to the Catskill, NY Receptor Site

USA Canada

• S. America

Europe Africa Asia Natural

60% 16% 13% 5% 2% 2% 2% Seigneur et al. 2002 for NYSERDA

(A) Precipitation Depth (mm) (B) Hg concentration in precipitation (ng L-1) (C) Hg wet deposition flux (µg m-2)

Event Event-

• based wet

based wet deposition Potsdam, deposition Potsdam, NY, Sept. 2003 NY, Sept. 2003 – – Apr. Apr. 2004) 2004)

Sponsored by NYSERDA and US Sponsored by NYSERDA and US EPA EPA

PSCF result for wet deposition PSCF result for wet deposition

PSCF value (max intensity, mean) 0.1 - 0.2 0.2 - 0.3 0.3 - 0.5 0.5 - 0.7 0.7 - 1

Based on 1999 NEI

From YJ Han

Dry Deposition Dry Deposition

Difficult to measure Function of surface type, Hg species, particle size,

meteorological conditions

Modeled as product of particle concentration and

deposition velocity, Flux = Vd × Hg(p)

Generally thought to be equal to or greater than wet

deposition

Area that needs additional research

Air Air-

• Water Exchange

Water Exchange

• f Hg
• f Hg0

= K = KOL

OL (

(C Cd

d-

• C

Ca

a/H)

/H)

KOL: mass transfer coeff. C Cd

d –

– dissolved dissolved concentration concentration Ca Ca – – air concentration air concentration H – Henry’s Law constant → RGM - deposition only → Hg(0) - deposition and evasion

Hg Mass Balance for Lake Ontario Hg Mass Balance for Lake Ontario

Conclusions Conclusions

• There are significant anthropogenic emissions of

There are significant anthropogenic emissions of Hg Hg – – biggest source in US is utility coal biggest source in US is utility coal combustion combustion

• The form of Hg in the atmosphere controls its

The form of Hg in the atmosphere controls its fate and transport fate and transport

• There is evidence that North America sources

There is evidence that North America sources contribute significantly to ambient Hg contribute significantly to ambient Hg concentrations and deposition in NYS concentrations and deposition in NYS