SF Bay Region Atmospheric Mercury Monitoring

Funded by: RMP, USEPA

w/ services by: NADP/MDN, Contra Costa, San Francisco, San Jose

Relevant Management Questions

• Are current estimates about loading to San Francisco Bay from watersheds, wastewater treatment facilities, and atmosphere valid?

• What is the contribution of atmospheric deposition to urban storm water?

SF Region Atmospheric Hg

• RMP Pilot Study– 1999-2000, wet deposition + dry ambient

concentration, 3 sites

• Mercury Deposition Network (MDN)– wet deposition continued 2000-2006 @ RMP pilot

study South Bay site (NASA Ames)

• Guadalupe & NASA Ambient Hg– ambient concentration @NASA, Calero, Fall 2005

RMP Pilot Study Sites

• Away from sources as practicable

• Located North (Martinez), Central (Treasure Island), South (NASA Ames) Bay

• NASA Ames becomes MDN site

NASA Ames• MDN CA72 “San Jose” site

Calero Reservoir

RMP Pilot Study/MDN• Aerochem (wet deposition) collector

Guadalupe/NASA Ambient• EPA Region IX Mobile Hg Lab

Mobile Hg Lab (Interior)

• Tekran automated Hg analyzer w/ particulate and reactive speciation modules. – 2537– 1135– 1130

2006 California MDN Sites

Sequoia NP

San Jose

Results: RMP Pilot Study

• Wet deposition & rainfall concentrations

South Bay

Central Bay

North Bay

Region

Area (km2) 485 214 434 1133

Rainfall (cm/yr) 36 68 58 53

Hg Conc (ng/L) 9.7 6.6 7.4 8.0

Wet Dep (µg/m2·yr) 3.5 4.5 4.3 4.2

Loading (kg/yr) 1.7 0.96 1.8 4.8

Results: MDN

• RMP Pilot S Bay: Conc < 10ng/L, rainfall < .5m/yr

San Jose Sequoia

2nd half 2003

2.04 µg/m2

.115 m precip

17.7 ng/L (3.60 µg/m2 13.4 ng/L all year)

2.56 µg/m2

.526 m precip

4.87 ng/L

2004 2.02 µg/m2

.257 m precip

7.88 ng/L

1.74 µg/m2

.412 m precip

4.22 ng/L

2005 3.56 µg/m2

.431m precip

8.26 ng/L

6.42 µg/m2

1.29 m precip

4.98 ng/L

Results: RMP Pilot Study

• Atmospheric Concentrations (pg/m3)

• No speciation measured

South Bay

Central Bay

North Bay

Entire Estuary

Average 2.20 1.90 2.30 2.10

Stdev .66 .33 .59 .57

(pg/m3)

Results: Calero• Daily afternoon Hg max (all species)• Reactive + particulate ~0.3% of elemental

Elemental, Reactive and Particulate Mercury - Calero Reservoir

0

1

2

3

4

5

9/9

/05

9/1

0/0

5

9/1

1/0

5

9/1

2/0

5

9/1

3/0

5

9/1

4/0

5

9/1

5/0

5

9/1

6/0

5

9/1

7/0

5

9/1

8/0

5

9/1

9/0

5

9/2

0/0

5

9/2

1/0

5

9/2

2/0

5

9/2

3/0

5

9/2

4/0

5

9/2

5/0

5

9/2

6/0

5

9/2

7/0

5

9/2

8/0

5

Ele

me

nta

l Me

rcu

ry (

ng

/m3

)

-5

0

5

10

15

20

25

30

35

40

45

Re

act

ive

, Pa

rtic

ula

te (

pg

/m3

)Elemental Mercury

Particulate

Reactive

Results: NASA• Daily morning Hg (elemental) max• Reactive + particulate ~0.2% of elemental

Elemental, Reactive and Particulate Mercury - NASA Ames

0

1

2

3

4

5

8/30

/05

8/31

/05

9/1/

05

9/2/

05

9/3/

05

9/4/

05

9/5/

05

9/6/

05

9/7/

05

9/8/

05

9/9/

05

9/10

/05

Ele

men

tal M

ercu

ry (

ng/m

3)

-5

0

5

10

15

20

25

Rea

ctiv

e, P

artic

ulat

e (p

g/m

3)

Elemental Mercury

Particulate

Reactive

Summary:

• Atmospheric conc and annual wet dep similar to previous RMP Pilot Study (Bayside & watershed sites similar magnitude)

• Direct wet dep flux to Bay ~4 µg/m2·yr (load ~5 kg/yr)• Reactive + particulate ~0.2-0.3% of elemental Hg

(~20x lower than previous RMP Pilot Study estimate of ~5% from literature)

• Direct dry dep flux to Bay ~2.5 µg/m2·yr (~3 kg/yr load, w/ 2 kg elemental, 1 kg reactive+particulate)

Management Implications:(with a bit of handwaving)

• Reactive+particulate= ionic dry dep ~ 1 kg/yr • Ionic wet dep unknown, possibly ~.015 kg/yr (0.3% of

total) to 5 kg/yr (100%)• New ionic mercury most readily available for

methylation (METAALICUS, 6% of applied 202Hg(II) converted to Me202Hg within 1 day)

• 0.4 to 2 pg/L·day ionic Hg available from air dep for methylation (1% to 5% of ambient MeHg conc)

• Need speciation for wet dep and other Hg loads to the Bay (which <1% of tot Hg becomes MeHg?)