Overview of Atmospheric Mercury

Measurement UncertaintiesMeasurement Uncertainties

Mae Gustin and Jiaoyan Huang

Department of Natural Resources

and Environmental Science

Acknowledgments

• Funding sources –

– U. S. National Science Foundation

– Electric Power Research Institute –EPRI

• Thanks to Gustin lab graduate and • Thanks to Gustin lab graduate and

undergraduate students

• Thanks to the many field site operators who

have helped us

Progress on Understanding Atmospheric Mercury Hampered

by Uncertain MeasurementsDaniel A. Jaffe,*,†,‡ Seth Lyman,§ Helen M. Amos,∥Mae S. Gustin,⊥ Jiaoyan Huang,⊥

Noelle E. Selin,# Leonard Levin,∇ Arnout ter Schure,○ Robert P. Mason,◆ Robert Talbot,¶

Andrew Rutter,∞ Brandon Finley,† Lyatt Jaeglé,‡ Viral Shah,‡ Crystal McClure,‡ Jesse Ambrose,†

Lynne Gratz,† Steven Lindberg,$ Peter Weiss-Penzias,⊗Guey-Rong Sheu,∀ Dara Feddersen,⧓Milena Horvat,◘ Ashu Dastoor,Я Anthony J. Hynes,@ Huiting Mao,Π Jeroen E. Sonke,★ Franz Slemr,⧖

Jenny A. Fisher,∫ Ralf Ebinghaus,∮ Yanxu Zhang,× and Grant Edwards⪫

• “at present there is no consensus on what the chemical form(s) of GOM is(are),nor any reliable method to identify the chemical form(s) in the atmosphere. It is likely that more than one form of Hg(II) exists in the atmosphere, depending on its source.” and the atmosphere, depending on its source.” and the oxidants in the air.

• “protocols do not provide a way to calibrate for GOM or PBM, quantify collection efficiency or quantify measurement interferences.”

• “There is some uncertainty as to whether current unspeciated measurements capture total gaseous mercury (TGM) or GEM.”

EST, 2014

Tekran system-Has been useful for

making progress for

understanding

atmospheric Hg

-Being used in networks -Being used in networks

world wide

--KCl-coated denuder

and particulate filter not

calibrated or checked for

interferences

Talk outline

• Focus on GOM uncertainties

• Brief summary of methods

• Chronological discussion of investigation of GOM uncertaintiesGOM uncertainties

• Note on PBM-

– instrument demonstrated to not collect all PBM (Talbot et al., 2011)

– PBM likely measures GOM not collected by the denuder (Gustin et al., 2013)

GOM Passive samplers

Lyman et al., 2009 and 2010 EST AE

Huang et al., 2014 Environ. Sci.: Processes Impacts

Dry deposition

Concentrations

Easily deployed by

regular people

No electricity needed

Demonstrated use in Florida, California, Nevada,

New Mexico, Oklahoma, Texas…….Maryland

UNR active system

Huang et al. 2013

Developed for measurement of GOM concentrations and

chemistry

UNR laboratory manifold

Te

kra

n®

at

4 o

r

7L

pm

Po

rt 1

: 1

Lp

m

Po

rt 2

: 1

Lp

m

Po

rt 3

: 1

Lp

m

Po

rt 4

: 1

Lp

m

zo

ne

an

aly

ze

r a

t

1.2

Lp

m

Imp

ac

tor

DI

wa

ter

so

urc

e

Ze

ro a

ir tan

k

2.5-5.5 Lpm

8-13 LpmAmbient air inlet

Main pumpGOM source

0.05-0.1 Lpm

Manifold

RH and Temp

Exhaust

T Oz

Ze

ro a

ir f

ilte

r

Huang et al., 2013Developed for loading and calibrating

membranes and calibrating the denuder

Florida TMDL Study

Assume the passive sampler data are correct and the Tekran data

are wrong

Gustin et al. 2013 ACP

Peterson et al. 2012 STOTEN

Passive samplers in Florida-GOMSS data corrected should be

higher by 0.2 ng m-2 h-1

Recent work suggests CEC

reflects natural surfaces

(Huang and Gustin 2014)

Measured deposition always

higher than modeled

Peterson et al., 2012 STOTEN

Passive samplers and Tekran

not always correlated

Passive sampler uptake and

SS deposition not always

correlated

Different deposition velocity

of the different forms will

influence uptake

Conclusions� Peterson et al. 2012 Investigate the utility of passive sampling systems to

record spatial and temporal patterns of atmospheric Hg

� Samplers do record spatial and temporal variation

� Variation does not match that measured with the Tekran

� Data suggests different forms of GOM across space and time

� Gustin et al. 2012 based on combining criteria air pollutant data and meteorology

� At OLF� At OLF

� natural background dry deposition 0.03 ng m-2 hr-1

� no significant influence of the EGP

� LRT 0.11 ng m-2 hr-1 GOM dry deposition derived from N-NW

� At Tampa

� Mobile sources 0.2 ng m-2 hr-1

� LRT in the spring 0.08 ng m-2 hr-1

� Davie

� Local point sources 0.1 ng m-2 hr-1

� LRT in the fall and spring 0.1 ng m-2 hr-1

Remember the dry deposition values were corrected and should be

higher by 0.2 ng m-2 hr-1

-Limitations of current methods to

measure atmospheric Hg need to be

systematically addressed

Reno Atmospheric Mercury

eXperiment – RAMIX

August to September 2011

Tekran Uncertainties Field-RAMIXSpike

Concentration

Response/Recovery (%)Instrument r2

n

mean std dev max min hourly

GEM/TGM

Response

Weeks 1 to 3

[ng m-3]

5 to 25

72 13 93 40 Spec 1 0.88 20

55 6 62 43 Spec 2 0.92 16

76 9 86 60Spec 2

adjusted0.92 16

76 12 97 35 UNR 2537 0.96 47

23 13 48 9 Spec 1 16

In manifold

Gustin et al., 2013 EST

RM Response

Week 3

[pg m-3]

~660

23 13 48 9 Spec 1 16

24 15 61 9 Spec 2 16

33 22 85 13Spec 2

adjusted16

Estimated GEM

Recovery

Week 4 [ng m-3]

6 to 8 76 7 - -Spec 1 – Spec

2 adjusted3

Estimated RM

Recovery

Week 4 [pg m-3]

340 to 780 17 3 24 11Spec 1 – Spec

2 adjusted18

RM comparison between Tekran and

DOHGS instrumentsDOHGS system higher RM concentration and measured form(s)

of RM not detected by Tekran

RM

[pg

m-3

]

100

150

RM

[pg m

-3] 400

500Spec 1

DOHGS

DOHGS BDL

Spec 2 adjusted

12:00 12:00 12:00 00:00 00:00 00:00 00:00

Te

kra

n R

M [

pg

m

0

50

100

DO

HG

S R

M [

pg m

0

100

200

300

Spec 2 adjusted

Sep-09 Sep-10 Sep-11 Sep-12

Environmental Science and Technology v 47 Issue 13

Environmental Measurement Methods

Finley et al. Ambrose et al. Gustin et al. 2013

Tekran Uncertainties

Laboratory manifold

GO

M m

ea

su

red b

y C

EM

[ng

]

4

5

6

GO

M m

easu

red

by n

ylon

me

mbra

ne [ng

]

2HgCl

2

HgBr2

HgO

Huang et al., 2013 EST

0 1 2 3 4 5 6

GO

M m

ea

su

red b

y C

EM

[ng

]

0

1

2

3

GOM measured by automatic KCl-coated denuder [ng]

0 1 2

GO

M m

easu

red

by n

ylon

me

mbra

ne [ng

]

0

1

HgCl2, y = 2.4 (0.8) x + 0.1 (0.5)

r2 = 0.58, n = 9

HgO, y = 3.7 (0.2) x + 0.1 (0.1)

r2 = 0.99, n = 6

HgBr2, y = 1.6 (0.4) x + 0.2 ( 0.1)

r2 = 0.86, n = 5

HgCl2, y = 1.6 (0.1) x + 0.002 (0.02)

r2 = 0.97, n = 12

HgO, y = 1.8 (0.05) x - 0.02 (0.03)

r2 = 0.99, n = 8

HgBr2, y = 1.7 (0.1) x - 0.01 (0.02)

r2 = 0.99, n = 10

Field measurements

MBL

03-0

4-1

2

03-1

8-1

2

04-0

1-1

2

04-1

5-1

2

04-2

9-1

2

05-1

3-1

2

05-2

7-1

2

06-1

0-1

2

RM

concen

tra

tion

[pg

m-3

]

20

40

60

80

100

120

HI

11-1

5-1

1

11-2

9-1

1

12-1

3-1

1

12-2

7-1

1

01-1

0-1

2

01-2

4-1

2

02-0

7-1

2

02-2

1-1

2

03-0

6-1

2

03-2

0-1

2

04-0

3-1

2

04-1

7-1

2

RM

con

cen

tration

[p

g m

-3]

20

40

60

80

100

120

Tekran

Nylon

CEM

AI

A A A A A A A

B BB B B

A

BBB

Huang et al., 2013 EST

00

11

-15-1

1

11

-29-1

1

12

-13-1

1

12

-27-1

1

01

-10-1

2

01

-24-1

2

02

-07-1

2

02

-21-1

2

03

-06-1

2

03

-20-1

2

04

-03-1

2

04

-17-1

2

0

5

10

15

20

25

Te

mp [C

] and

RH

[%

]

-20

0

20

40

60

80

100Precip

TEMP

RH

03

-04-1

2

03

-18-1

2

04

-01-1

2

04

-15-1

2

04

-29-1

2

05

-13-1

2

05

-27-1

2

06

-10-1

2

Pre

cip

ita

tion [m

m]

0

5

10

15

20

25

-20

0

20

40

60

80

100

GOM compounds

Laboratory

Temp [C]

40 60 80 100 120 140 160 180 200

GO

M/R

M r

ele

ase

pe

rcen

tag

e [

%]

0

5

10

15

20

GO

M/R

M r

ele

ase

pe

rce

nta

ge [

%]

0

5

10

15

20HgCl2 (n = 9)

HgBr2 (n = 9)

HgO (n = 6)

GEM (n = 3)

HI

5

10

5

10

Nov and Dec 2011 (n = 6)

Jan and Feb 2012 (n = 9)

April 2012 (n = 3)

Huang et al., 2013 EST

GO

M/R

M r

ele

ase

pe

rcen

tag

e [

%]

GO

M/R

M r

ele

ase

pe

rce

nta

ge [

%]

0 0AI

0

5

10

15

0

5

10

15Aug 2011 (n = 4)

Jun 2012 (n = 6)

MBL

Temp [C]

40 60 80 100 120 140 160 180 200

0

5

10

15

20

25

0

5

10

15

20

25Mar 2012 (n = 9)

Apr 2012 (n = 3)

Laboratory study- Ozone impacts the

denuder

Lyman et al. 2010

Laboratory study-relative humidity

impacts the denuder

RH <35% collection efficiency is 21 + 9% lower n=8

RH > 35% collection efficiency is 35 + 18 % lower n=9

TGM versus GEM

• Inlet configuration will significantly influence

result

• RAMIX insight- covered line and temperature

drops results in RM depositiondrops results in RM deposition

• Uncovered line results in better transmission

of TGM

• Some systematic tests are needed to better

understand this

Conclusions

• KCl denuder does not collect different forms

of GOM with equal efficiency

• The measurement is biased low and varies as

a function of the different forms in air.a function of the different forms in air.

• There are interferences with water vapor and

ozone that result in GOM being biased low.

Conclusions

• Surrogate surfaces are useful for understanding potential dry deposition

• Passive samplers are useful for understanding relative concentrations

• These samplers may be applied across broad spatial and temporal scales

• These samplers may be applied across broad spatial and temporal scales

• The passive sampler method needs to be refined

• Additional laboratory tests are needed to understand and calibrate

• Huang et al 2014 Critical Review Environ. Sci.: Processes Impacts, 16, 374-392.

Conclusions

• GOM compounds vary across space and time

• Source of Hg are global it’s the oxidants

present that will influence the production of

GOM and the GOM chemistryGOM and the GOM chemistry

What are current issues?

�Determine limitations of the denuder so we

can interpret data collected in the past

�Additional tests needed for passive samplers

�Unknown GOM compounds in air�Unknown GOM compounds in air

� Address uncertainties of PBM measurements

�Lack of world-wide measurement of long term

spatial and temporal variation in Hg

How to move forward

• Active system appears to work well for

quantifying GOM collected on CEM

• Thermodesorption is a first step at trying to

understand presence of different forms in airunderstand presence of different forms in air

• Passive samplers are useful for measuring

deposition and assessing concentrations

across space and time

Needs

• “Develop calibration methods for GOM and provide routine calibrations for field instrumentation;

• Conduct detailed investigations to quantify interferences in the existing GOM methods and develop new methodologies to measure it; and

• Conduct fundamental research on the chemistry, reaction • Conduct fundamental research on the chemistry, reaction kinetics and chemical identity of the compounds that makeup GOM and PBM in the atmosphere.

• We believe these items should be given high priority by the mercury scientific community. To do otherwise impedes scientific progress and environmental monitoring efforts.”

Exact words from Environmental Science & Technology

Viewpoint

B dx.doi.org/10.1021/es5026432