1. the impacts of transboundary air
pollution on acid sensitive lakes
julian aherne, heidi scott, andrew burton, colin whitfield,
kevin adkinson, thomas cummins, and others…
Ireland’s Environment 2012: EPA-STRIVE Research Conference
Trinity College Dublin [28 June 2012]

2. overview | atmospheric pollution can adversely affect the natural
environment leading to significant impacts on ecosystem services.
sulphur and nitrate dioxide cause acidification.
excess nitrogen causes decreased ecosystem biodiversity.
heavy metals and persistent organic pollutants may accumulate in soil
and water and cause damage to the environment and human health.
as a consequence, during the last two decades international policies have
focused on reducing emissions of transboundary air pollutants.
source: www.apis.ac.uk

3. objective | the principal objective was to assess the impacts of major
transboundary air pollutants on acid-sensitive lakes and soils, their
response to reductions in emissions of sulphur and nitrogen oxides, and
to address knowledge gaps in relation to the levels of heavy metals and
persistent organic pollutants in semi-natural ecosystems.
• assess response of rainfall chemistry to emissions reductions
• evaluate response of surface waters (predominantly small upland
headwater lakes) to changes in atmospheric deposition
• evaluate the levels and controls on trace metals in acid-sensitive lakes
• evaluate the influence on sea-salt on acidification of lakes
• evaluate the drivers of long-term patterns in surface waters
• evaluate the controls on green house gases…
• characterise the physico-chemical characteristics of acid sensitive soils
• evaluate total and methylmercury in the soil and water
• evaluate the presence of POPs in the soil and water of selected
headwater lake catchments
emission reductions | western | marine | semi-natural ecosystems | climate

4. (a) assess response of rainfall chemistry to emissions reductions
location of monitoring stations
contributing precipitation
chemistry to the co-operative
programme for monitoring and
evaluation of the long range
transmission of air pollutants in
Europe (EMEP [Chemical Co-
ordinating Centre]).

5. one-day back-trajectory wind-rose plots showing the proportion (%) of air by
direction and source during the period 1989–2009 for sites in west (Mayo) and
east (Wicklow)

6. –1 –1 –1
Non-marine sulphate (mg L ) Nitrate (mg L ) Ammonium (mg L )
0.6 0.40 0.6
Valentia Observatory
Turlough Hill
0.5 The Burren 0.5
Ridge of Capard
0.30 Oak Park
Glenveagh
0.4 0.4
Johnstown Castle
Lough Navar
Median concentration
0.3 0.20 0.3
0.2 0.2
0.10
0.1 0.1
0.0 0.00 0.0
1990 1995 2000 2005 2010 1990 1995 2000 2005 2010 1990 1995 2000 2005 2010
long-term annual trend (1991–2009) in non-marine sulphate, nitrate and
ammonium concentration in precipitation (mg L–1) at EMEP stations

7. (b) evaluate response of headwater lakes to changes in atmospheric deposition
sensitivity of surface waters to survey lakes sampled during spring
acidification based on soil and geology 1997 and 2007 (n = 77)

10. significant decreases in SO42–, nmSO42– and non-marine base cations, and significant
increases in alkalinity between the 1997 and 2007 lake surveys, suggesting that lakes have
responded to reductions in long-range transboundary air pollution. However, there were no
significant changes in surface water pH and AlT. It is likely that inter-annual variations in sea
salt inputs and DOC concentrations (organic acidity) may have contributed to the delay in
recovery of pH.

11. (c) evaluate the levels and controls on trace metals in acid-sensitive lakes
sensitivity of surface waters to trace metal survey lakes sampled
acidification based on soil and geology during spring 2008 (n = 122)

12. order of total trace metal concentrations (µg L–1) was (highest to lowest) : Fe >
Al > Mn > Sr > B > Zn > Ba > Ti > Mo > Se > V = As > Bi > Cr > Ni = Cu > Cd > Pb >
Tl > Co > U > Hg. The study lakes were strongly dominated by Fe, Al and Mn,
measurements BDL were common for certain elements such as Be (100% BDL),
Cd (79%), Se (40%), Co (39%) and Pb (29%).
fractions: trace metals (i.e., Al, Mn, Fe, Ni, Cu, Zn, Sr, Ba, V and B) were
predominantly in dissolved form; although elevated particulate fractions were
observed for Mn (20%), Al (25%) and Fe (33%). The dissolved labile phase was
the dominant form for Sr (98%), Ba (90%), Mn (78%) and Zn (75%). In contrast,
the dissolved non-labile phase was dominant for Cu (78%), Ni (67%), Fe (58%),
V (58%) and Al (48%).

13. toxicity: trace metal concentrations were low, within the range of pristine
global surface water concentrations; however, dissolved zinc, cadmium,
inorganic labile aluminum and manganese may potentially reach levels harmful
to aquatic organisms in some lakes (~20%).
sources: redundancy analysis indicated that metals were predominantly derived
from geochemical weathering. However, a number of trace metals (e.g., lead,
zinc) were correlated with anthropogenic atmospheric deposition (non-marine
sulphate), suggesting atmospheric sources or elevated leaching owing to acidic
deposition. Dissolved organic carbon (DOC) was a major driver associated with
higher concentrations of dissolved metal fractions.

14. (d) evaluate the levels and controls on green house gases
ghg: the majority of lakes were
supersaturated with CO2, N2O and CH4.
principal components analysis indicated
that higher levels of CH4 and N2O
supersaturation were exhibited under
different land-cover conditions. Methane
supersaturation was highest in lower
elevation catchments with an evaporative
hydrologic character and high organic
carbon concentration. In contrast, lakes
characteristic of N2O supersaturation
were low in carbon and located in more
rapidly flushed higher elevation
catchments.

15. (e) evaluate the influence on sea-salt on acidification of lakes
–1
Daily chloride (mg L )
250
“Lowest March pressure on record for
Valentia Observatory
Ireland on 10th” Met Eireann, Glenveagh Park
Monthly Weather Bulletin, March 200 –1
March 10: Valentia Observatory 1967.0 (mg L )
2008.
“Deep depressions passing close to or 150
over Ireland brought very unsettled
conditions, with strong winds and 100
spells or rain or showers each day. All
areas received heavy rain between
the 9th and 11th… The same period 50
produced very strong winds…”
0
0 50 100 150 200 250 300 350
Julian day (2008)

16. sodium:chloride ratio in lake water during 2007 (left) and 2008 (right) surveys

17. –1 –1 –1
Chloride (mg L ) Dissolved organic carbon (mg L ) Calcium (mg L )
100 20 4.0
75 15 3.0
50 10 2.0
25 5 1.0
0 0 0.0
2007 2008 2007 2008 2007 2008
pH –1 –1
8.0 Total aluminium (µg L ) Manganese (µg L )
200 100
7.0
150 75
6.0
100 50
5.0
50 25
4.0
3.0 0 0
2007 2008 2007 2008 Y2007 Y2008
Box-plot comparison of paired lake chemistry (n ~ 50) observations from the
2007 and 2008 surveys, before and after the 10 March 2008 sea-salt event.

18. (f) & (g) POPs and Hg in headwater catchments: intensive study catchments

20. (e) evaluate the presence of POPs in the soil and water of lake catchments
Concentrations of POPs in Water at Study Lakes (n=5)
600 60
CUM
ADA
MUL
500 50
SGI
CLE
400 40
pg/L
pg/L
300 30
200 20
100 10
0 0
s an -a -b T Ps s
AH CH ulf es es DD OC CB
lP talH os ien ien tal er lP
T ota To en
d lod lod To oth T ota
tal cyc cyc tal
To tal tal To
To To
POPs
water: mean ± S.D. (n=3) lake concentrations of POPs estimated from SPMDs
deployed during the period from July, 2009 to January, 2010 at the five study
sites. Other OCPs include OCS, HCB, Methoxyxhlor, and Pentachloranisole.

21. 2
Concentrations of POPs in Soil at Study Sites (n=5) Concentration of POPs per m of Soil at Study Sites (n=5)
40 2500 60
1500
CUM
CUM
ADA
ADA 50
MUL
500 20 2000 MUL
SGI
SGI
CLE
CLE
40
400
15 1500
2
2
30
300
g/m
ng/g
ng/g
g/m
µ
µ
10 1000
200 20
5 500
100 10
0 0 0 0
To To To To To To
tal To tal tal tal To tal tal
PA tal DDTo PC PA tal D PC
Hs PB T ta Bs PB To
DT
DE lo Hs DE tal Bs
s the s oth
e
POPs r O CP POPs r OC
s P s
soil: concentrations (left) and pool (right) of POPs measured in soils at the
five study sites ( ng/g and µg/m2), sampled during October 2010. Other OCPs
include HCHs, Cyclodienes-a and b, Endosulfan, OCS, HCB, Methoxyxhlor, and
Pentachloranisole.

22. POPs summary
• physical, meteorological, and chemical parameters exhibited correlations
with POPs in SPMDs and soil samples, e.g., lake:catchment ratio, rainfall,
DOC, and source air (e.g., Endosulfan and % overland air).
• the role of media partitioning for many of the compounds is apparent.
Even in highly organic soils, HCHs, HCB, Endosulfan, and less-chlorinated
PCBs have a tendency to revolatilize or washout more readily and are
more likely to be captured in SPMDs. Whereas, ‘heavier’ compounds,
e.g., PAHs, PBDEs, and the more-chlorinated PCBs bind to soil and
sediments.
• observed concentrations were well within, or below, the range of
‘background’ values from continental Europe and internationally.

23. (e) evaluate total and methylmercury in the soil and water
5 0.18
0.15
4
Plot 1
0.12
MeHg (ng/L)
THg (ng/L)
3
0.09
2
0.06
1
0.03
0 0.00
CUM ADA MUL SGI CLE CUM ADA MUL SGI CLE
Site Site
water: averages concentrations of THg (n= 6) and MeHg (n= 4) in study lakes
between 2010 and 2011.

24. relationships between THg (and MeHg) in water and lake chemistry
4.5 0.14
4.0
0.12
3.5
Predicted THg (ng/L)
0.10
3.0
2.5 0.08
2.0
0.06
1.5
Predicted MeHg(ng/L)
0.04
1.0
0.5 0.02
0 1 2 3 4 5 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
THg (ng/L) MeHg (ng/L)
THg = –2.458 + (0.327 * TOC) +
MeHg = –0.0602 + (0.0023 *
(0.261 * Na+) – (1.178 * SiO2) –
Conductivity) + (0.0215 * Gran
(0.606 * d18O) Adj R2 = 0.56
Alkalinity) + (0.0501 * SiO2) +
(0.0031 * Turbidity) Adj R2 = 0.48

25. 400 500
400
300
THg (ng/g)
THg ( g/m )
2
300
µ
200
200
100
100
0 0
CUM ADA MUL SGI CLE CUM ADA MUL SGI CLE
Site Site
soil: averages concentrations (left) and pools (right) of THg in soil at the five
study catchments, October 2010.

26. Age Chronology of MUL Peat Core Fluxes of THg in MUL Peat Core
0
2
2010
1994 ± 1
Hg summary
0
2
2010
1994 ± 1
4
6
1973 ± 2
1961 ± 2 • various physical and chemical
4
6
1973 ± 2
1961 ± 2
8
10
1953 ± 3
1946 ± 3
8
10
parameters exhibited 1953 ± 3
1946 ± 3
12 1940 ± 3 12
correlations with Hg in water and 1940 ± 3
soil samples; notably THg is
14 1931 ± 3 14 1931 ± 3
16 1921 ± 3 16
Year
1921 ± 3
Year
18 1905 ± 4 18
strongly influenced by the level of 1905 ± 4
Depth (cm)
Depth (cm)
20 1880 ± 5 20 1880 ± 5
22
24
1811 ± 17
1787 ± 25
22
24
organic matter in soil and water 1811 ± 17
1787 ± 25
26
28
1753 ± 45
• lake concentrations of Hg in this
26
28
1753 ± 45
30 30study were similar to levels
measured inTHg (µg/m ) and soils
water
50 100 150 200 250 300 350 0 10 20 30 40 50 60 70
2
THg (ng/g)
elsewhere.
Age Chronology of SGI Peat Core
• peat core records Peat Core there
Fluxes of THg in SGI
indicate
0 2010 0have been significant decreases 2010
since the highest peaks (1950–
2 2001 ± 2 2 2001 ± 2
4 1988 ± 2 4 1988 ± 2
6
8
1980 ± 3
1970 ± 3
6
8
1980s), indicative of regulation 1980 ± 3
1970 ± 3
10 1959 ± 4 10and enforcement of Hg 1959 ± 4
emissions.
12 1949 ± 4 12 1949 ± 4
14 1937 ± 4 14 1937 ± 4
• northwestern sites appear to
16 1927 ± 5 16 1927 ± 5
Year
Year
18 1914 ± 5 18 1914 ± 5
Depth (cm)
Depth (cm)
20
22
1896 ± 6
1872 ± 7
20
22have highest levels of THg and 1896 ± 6
1872 ± 7
24
26
24
26
MeHg in lake water and soils.
28 28
30 30
0 100 200 300 400 500 600 0 20 40 60 80
THg (ng/g) 2
THg (µg/m )

27. overall conclusions
3. precipitation chemistry shows a significant response to emission reductions
of sulphur dioxide (and tentative for nitrogen oxides)
4. in concert, lake chemistry has responded to reduced anthropogenic
sulphur deposition, but pH has not changed owing to increases in dissolved
organic carbon
5. trace metal concentrations were low, dominated by iron, aluminium and
manganese; however, dissolved zinc, cadmium, inorganic labile aluminum
and manganese may potentially reach levels harmful to aquatic organisms
6. lakes were supersaturated with GHGs; however, effluxes contributed little
to national emissions. Methane and nitrous oxide are strongly related to
landscape characteristics
7. Sea-salt events can have significant and widespread impacts on lake
chemistry (albeit temporary)
8. levels of POPs and Hg were low, consistent with background regions and
strongly associated with organic carbon
climate: potential future changes to biogeochemical cycling of carbon (soil organic
matter / dissolved organic carbon) and climate variability (storminess) will influence
acid status, trace metals and mercury, and POPs in semi-natural ecosystems…