Methylmercury in Bay and Wetland Sediments of the San Francisco Bay Region Don Yee, SFEI RMP 2008 Hg Coordination Meeting San Francisco Estuary Institute.

Methylmercury in Bay and Methylmercury in Bay and Wetland Sediments of the San Wetland Sediments of the San

Francisco Bay RegionFrancisco Bay Region

Don Yee, SFEIDon Yee, SFEIRMP 2008 Hg Coordination MeetingRMP 2008 Hg Coordination Meeting

San Francisco Estuary Institute

UC Santa Cruz

USGS WRD Menlo Park CA, Middleton WI, BRD Vallejo CA

San Francisco Hg SourcesSan Francisco Hg Sources

Anthropogenic sources dating to Gold Rush

USBM/USGS

Ongoing SF Bay Hg SourcesOngoing SF Bay Hg Sources

Source kg/yrBed Erosion 460Central Valley Watershed 440Urban Stormwater Runoff 160Guadalupe River Watershed (mining legacy) 92Atmospheric Deposition 27Non-Urban Stormwater Runoff 25Wastewater (municipal and industrial) 18Sediment Dredging and Disposal 0

SFBRWQCB TMDL

Bay Sampling LocationsBay Sampling Locations

Regional Monitoring Program – survey Bay1993-– summer (annual)– 49 sediment sites– random stratified

5 bay segments + rivers

Wetland Sampling LocationsWetland Sampling Locations

3 wetlands along Petaluma River– Gambinini Ranch– Mid-Petaluma Marsh– Black John Slough

Gradient of increasing salinity/Bay influence

San Pablo Bay

City of Petaluma

< Gambinini Marsh< Gambinini Marsh

< Mid Petaluma< Mid Petaluma

Black John Slough >Black John Slough >

Wetland Site DistributionWetland Site Distribution

Habitat elementsa) medium channelsb) small channelsc) high marsh edged) high marsh interior

Composites (transects or clusters)

Replicates of habitat elements

ab c

d

Hydro-Biological Hydro-Biological InteractionsInteractions

Overbank events recharge groundwater table

Marsh plain interiors drain slowly Redox swings with O2 supply and

respiration

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/06

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/06

DATEOR

P m

V o

r m

mH

20

vs

Su

rfa

ce

Redox GW_mmH20 chan_mmH20

Bay Hg and MeHg 2002-2006Bay Hg and MeHg 2002-2006

Intersegment DifferencesIntersegment DifferencesSan Pablo Bay (SPB) Hg high but MeHg low

SF Bay MeHg vs Total HgSF Bay MeHg vs Total Hg

Sediment concentrations poorly correlated

0.00

0.50

1.00

1.50

2.00

2.50

0.0 0.2 0.4 0.6 0.8 1.0

Hg mg/kg dw

MeH

g µ

g/kg

dw

2002

2003

2004

2005

2006

y = 1.41x + 0.235

R2 = 0.092

Wetland MeHg vs Total HgWetland MeHg vs Total Hg

Sediment MeHg vs Hg also poorly correlated

0

5

10

15

20

25

100 200 300 400 500STHg (ng/g dry)

SM

Hg

(ng/

g dr

y)

BJMPGM

BJy = -0.0201x + 7.8516R2 = 0.1482

MPy = -0.0144x + 8.4838R2 = 0.076

GMy = -0.0053x + 5.3061R2 = 0.0107

What Drives MeHg?What Drives MeHg?

Plenty of Hg, SO4, bacteria need food!

BJ y = 0.0012x - 0.0039

R2 = 0.278MP y = 0.0014x - 0.0105

R2 = 0.517

GM y = 0.0004x + 0.0061

R2 = 0.102

0%

1%

2%

3%

4%

5%

6%

7%

8%

5 10 15 20 25 30 35 40

% Loss on Ignition

% M

eHg/

TH

g

BJ

MP

GM

Linear (BJ)

Linear (MP)

Linear (GM)

Wetland Plant ProcessesWetland Plant Processes

(Windham will give details)

Compare untreated vs devegetated areas

Wetland Devegetation Wetland Devegetation EffectsEffects

organic = reduced reduction

-100

-75

-50

-25

0

25

50

75

MeH

gPro

du

ction

Rate

Con

sta

nt

(k)

Estim

ate

d

MeH

g

Pro

du

ction

Rate(k

*Hg

II)

Mic

rob

ial S

ulfate

Red

uction

Rate

(k)

Acid

Vola

tile

Su

lfu

r

Tota

l R

ed

uced S

ulfu

r

Ch

rom

ium

Red

ucib

le S

ulfu

r

Ferr

ou

s I

ron

Pore

wate

rDis

solv

ed

Org

an

ic C

arb

on

Pore

wate

rSu

lfid

e

Pore

wate

rSu

lfate

(mm

ol)

Pore

wate

rCh

lorid

e (m

mol)

Red

ox(E

h)

% D

iffe

rence b

etw

een p

air

s o

f veg

eta

ted a

nd

d

eveg

eta

tedplo

ts

Pairwise t-tests p<0.05-100

-75

-50

-25

0

25

50

75

MeH

gPro

du

ction

Rate

Con

sta

nt

(k)

Estim

ate

d

MeH

g

Pro

du

ction

Rate(k

*Hg

II)

Mic

rob

ial S

ulfate

Red

uction

Rate

(k)

Acid

Vola

tile

Su

lfu

r

Tota

l R

ed

uced S

ulfu

r

Ch

rom

ium

Red

ucib

le S

ulfu

r

Ferr

ou

s I

ron

Pore

wate

rDis

solv

ed

Org

an

ic C

arb

on

Pore

wate

rSu

lfid

e

Pore

wate

rSu

lfate

(mm

ol)

Pore

wate

rCh

lorid

e (m

mol)

Red

ox(E

h)

% D

iffe

rence b

etw

een p

air

s o

f veg

eta

ted a

nd

d

eveg

eta

tedplo

ts

Pairwise t-tests p<0.05

SF Bay MeHg vs TOCSF Bay MeHg vs TOC

Not all carbon is good bacterial food

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0.50

1.00

1.50

2.00

2.50

0.0 0.5 1.0 1.5 2.0 2.5

% TOC

MeH

g µ

g/kg

dw

2002

2003

2004

2005

2006y = 0.44x + 0.072

R2 = 0.099

SF Bay MeHg vs Total NSF Bay MeHg vs Total N

N better proxy for labile organic matter?

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0.50

1.00

1.50

2.00

2.50

0.00 0.05 0.10 0.15 0.20 0.25

% Total N

MeH

g µ

g/kg

dw

2002

2003

2004

2005

2006

y = 5.27x - 0.056

R2 = 0.23

SF Bay MeHg vs RedoxSF Bay MeHg vs Redox

OM substrate -> reduction -> methylation

0.00

1.00

2.00

0 100 200 300 400 500 600

Eh mV 1-6cm Average

MeH

g µ

g/kg

dw

2003

2004

2005

2006

y = -0.0017x + 0.89

R2 = 0.20

Linkage to BiotaLinkage to Biota

Biota Hg concentrations mirror ambient MeHg– matrix linked to nearest food web element

– e.g. Slotton water MeHg vs fish in Sacramento Delta

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GM MP BJ

me

Hg

ug

/g w

w

Target marsh invertebrates

aa

b

HM Average

0

2

4

6

8

10

GM MP BJ

MeH

g 0-

2cm

Dep

th (

ng/g

dry

)

SummarySummary

New(ish): Total Hg not limiting MeHg in SF Bay (both wetlands & subtidal)– MeHg generally < 1% of total Hg– Legacy loads, ongoing inputs >> sufficient for all

MeHg production

Q1 (what “hot” spots) & Q2 (what processes): high Sediment MeHg linked to OM/ redox– Less reduction less methylation, more

demethylation

Management ImplicationsManagement Implications

Q3 (how might we manage) even small Hg inputs could support a major portion of standing MeHg pool– 1 week air input = water MeHg pool– 2 years input = sediment MeHg pool top 5cm

Might some Hg be more manageable?– e.g. METAALICUS new 202Hg 1% of total Hg

overall but 6% of vegetation Hg within 15 weeks

Management ImplicationsManagement Implications

More productivity = more OM more MeHg?– Will wetland restoration exacerbate Hg problem?– Competing goal of more wildlife habitat

Indirect management levers– MeHg control by-product of nutrient TMDL?

Need better understanding of– Relative availability of Hg loads– MeHg transport and uptake into food web

Closing CreditsClosing CreditsFunding: SF Estuary Regional Monitoring Program, CBDA Ecosystem

Restoration Program Sampling, Site Access: USBR Endeavor, CA DFG, R.Phelan & S.BrandProject Partners:

AMS: P.Salop, B.Bemis, C.Dominik, B.HajduczekSFEI: J.Collins, L.Grenier, J.Hunt, S.Pearce, C.Striplen, S.Shonkoff, S.Bezalel, N.David, A.Franz,M.WilliamsUCSC : A.R.Flegal, S. HibdonUSGS WRD-CA: M.Marvin-DiPasquale, J.Agee, L.Kieu, N.Ladizinski, L.WindhamUSGS WRD-WI: D.Krabbenhoft, T.Sabin, J.DeWildUSGS BRD- J.Takekawa, I.Woo, D.Tsao-Melcer,

Photo: D.Gaube, E.Lindgren, B.Hill