Anthropogenic  perturba0ons  to  the  biogeochemical  cycle  of  mercury  

Helen  M.  Amos,  Daniel  J.  Jacob,  David  G.  Streets,  Elsie  M.  Sunderland  

AMS  Atmospheric  Biogeosciences,  01  June  2912  

To  what  extent  is  the  present  day  impacted    by  past  releases?  

New  Almaden  Mine,  Santa  Clara  County  

Nriagu  (1994)  –  illustraHon  from  Erker  (1574)  

Evidence  of  3500+  years  of  Hg  releases  

Peru  Hg  flu

x  raHo

 

103  

102  

10  

1  

0.1  

Calibrated  Year  AD/BC  

Cooke  et  al.  (2009)  

Historical  simula0on  of  global  Hg  cycle  

!""#$%&"'(

)*+)*,-'&"$%&"'(

)*,-'&"$%&"'($$

./(",'0

',.%,"! )0%1 -')2

'2.%)#3","

)%/0)$'(!$4"5"2'2/%(

Anthropogenic  emissions  

Streets  et  al.  (2011)  

Approach  •   box  model  of  global  Hg  cycle  

• historical  anthropogenic  emissions  •   pre-­‐1850:  137  Gg  •   1850-­‐2008:  215  Gg  

•   0me-­‐dependent  simula0on:        2000  BC  –  2008  AD  

Advantages  •   coupling  between  reservoirs  on  0mescales  ranging  from  <1  –  1000s  years  

•   geogenic  emissions  define  natural  steady-­‐state  

•   quan0fy  anthropogenic  enrichment  and  legacy  Hg  

Amos  et  al.  (in  prep)  

Global  Hg  reservoirs  have  experienced  substan0al  anthropogenic  enrichment  

!""#$%&"'(

)*+)*,-'&"$%&"'(

)*,-'&"$%&"'($$

!""#$./(",'03x1011 Mg

',.%,"!210,000 Mg

(120%)

)0%148,000 Mg(490%)

-')210,000 Mg(560%)

'2.%)#3"," 5200 Mg (730%)

3000 Mg (570%)

140,000 Mg (510%)

190,000 Mg (200%)

)%/0)$'(!$4"5"2'2/%(

~54 m

~1500 m

Amos  et  al.  (in  prep)  

Most  of  the  anthropogenic  Hg  in  the  ocean  was  emiTed  before  1950  

85%

15%

surface ocean

84%

16%

subsurface ocean

67%

33%

deep ocean

anthropogenicnatural

17%

8%

20%19%

23%

13%

6%

8%

23%

22%

27%

15%

< 1%6%

15%

29%

49%

surface  ocean   subsurface  ocean   deep  ocean  

anthropogenic  

natural  

2000-­‐2008  

1990-­‐  1999  

1950-­‐1989  

1900-­‐1949  

1850-­‐  1899  

pre  1850  

natural  vs.  anthropogenic  

Contribu0on  from  different  

historical  periods  

Amos  et  al.  (in  prep)  

Deposi0on  will  increase  under  all  IPCC    future  scenarios  

1850 1900 1950 2000 2050 21000

1000

2000

3000

4000

5000

6000

7000

8000

Year (AD)

(Mg

a1 )

Future Anthropogenic Emissions

A1BA2B1B2Best caseZero

1850 1900 1950 2000 2050 21000

0.5

1

1.5

2

2.5x 104

Year (AD)

(Mg

a1 )

Future Atmospheric Deposition

A1BA2B1B2Best caseZero

A1B  

A2  

B2  

B1  

Best  Zero  

Anthropogenic  Emissions   Atmospheric  Deposi0on  

Our  best  case  scenario  assumes  widespread  implementa0on  of  Hg  specific  control  technology.  

A1B,  A2,  B1,  B2:    Streets  et  al.  (2009)  

Amos  et  al.  (in  prep)  

Legacy  Hg  plays  a  crucial  role  in  future  scenarios  

Global  atmospheric  deposi0on  1850 1900 1950 2000 2050 21000

0.5

1

1.5

2

2.5 x104

Year (AD)

NaturalPrimaryLegacy

0

4000

8000

12000

-

-

0

2000

4000

6000

8000

(Mg

a-1 )

1850 1900 1950 2000 2050 2100Year (AD)

1850 1900 1950 2000 2050 2100Year (AD)

(Mg

a-1 )

(Mg

a-1 )

!"#

#"

$%&'

natural  primary  anthropogenic  

legacy  

IPCC  best  case  –  B1  

1850 1900 1950 2000 2050 21000

0.5

1

1.5

2

2.5 x104

Year (AD)

NaturalPrimaryLegacy

0

4000

8000

12000

-

-

0

2000

4000

6000

8000

(Mg

a-1 )

1850 1900 1950 2000 2050 2100Year (AD)

1850 1900 1950 2000 2050 2100Year (AD)

(Mg

a-1 )

(Mg

a-1 )

!"#

#"

$%&'zero  future  emissions  

(Mg  a-­‐

1 )  

(Mg  a-­‐

1 )  

Amos  et  al.  (in  prep)  

Legacy  Hg  can  provide  an  addi0onal    benefit  or  penalty  

A1B A2 B1 B2 Best Zero

(Mg)

PrimaryLegacy

legacy  

primary  

Changes  in  2100  Deposi0on  Rela0ve  to  2015  

•   All  IPCC  scenarios:      penalty  from  legacy  exceed      primary  penalty  

•   Best  case:        primary  benefit  offset  by  lags      in  legacy  Hg  

•   Zero  future  emissions:      effecHve  benefit  is  nearly      doubled  because  of  legacy  

Amos  et  al.  (in  prep)  

Fate  of  anthropogenic  Hg  

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

atmocsociocdtftsta

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1Fr

actio

n

Time (years)

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

atmocsociocdtftsta

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

atmocsociocdtftsta

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

0 20 40 60 80 1000

0.2

0.4

0.6

0.8

1

Frac

tion

Time (years)

atmosphere  

subsurface  ocean  

surface  ocean  

deep  ocean  

fast  terrestrial  

slow  soil  armored  soil  

1  Mg  into  atmosphere   1  Mg  into  surface  ocean   1  Mg  into  fast  terrestrial  pool  

Frac0on

 

Amos  et  al.  (in  prep)  

Summary  

Helen  Amos  amos@fas.harvard.edu  

hTp://people.fas.harvard.edu/~amos  

•   Global  biogeochemical  box  model  used  to  characterize  Hmescales  of  response,  anthropogenic  enrichment,  and  to  separate  legacy  Hg  from  primary.  

•   Surface  and  subsurface  ocean  enriched  by  >500%.  More  than  50%  of  the  anthropogenic  Hg  in  the  ocean  today  was  released  prior  to  1950.    

•   If  future  emissions  stay  constant  (B1),  deposiHon  will  increase  by  40%  by  2100  w.r.t.  to  present  day.    

•   If  future  emissions  can  be  aggressively  decreased,  longer  effecHve  benefit  from  legacy  Hg.  

•   The  subsurface  ocean  plays  a  central  role  in  the  environmental      fate  of  anthropogenic  Hg.