critical loads— and ecosystem impacts of air pollutants

Clean Air Conference Wood Quay Venue, Dublin City Council [28 September 2015]

It is well established that anthropogenic air pollution can have negative impacts on the natural environment, both in terms of direct effects on vegetation, and indirectly through effects on the acid and nutrient status of soils and waters.

impacts to ecosystem health such as acidification, eutrophication (loss of species diversity) and ground level ozone (crop damage) associated with the emissions of the sulphur (S) and nitrogen (N) oxides, and ammonia (national and transboundary air pollutants). transboundary air pollution refers to pollutants that are not easily destroyed or react in the atmosphere to form secondary pollutants. These pollutants can be generated in one country and deposited in others; as such they require international actions* and collaboration to control their formation and effects. *Convention on Long-range Transboundary Air Pollution (LRTAP)

transboundary air pollution

Convention on Long-range Transboundary Air Pollution

under the Convention, the ‘critical loads’ concept was introduced as an effects-based tool for assessing the sensitivity of natural habitats to the harmful effects of S and N deposition, i.e., air pollution thresholds to protect and restore ecosystem health. “a quantitative estimate of exposure to one or more pollutants below which significant harmful effects on sensitive elements of the environment do not occur according to present knowledge” exceedance of critical load quantifies the environmental harm associated with air pollution, e.g., biodiversity indicator ‘critical load exceedance for nitrogen’.

critical loads

Gothenburg Protocol under Convention on LRTAP based on critical loads. similarly EU’s National Emission Ceilings (NEC) directive introduced legally binding national emission limits for sulphur dioxide, nitrogen oxides and ammonia (to reduce levels of acidification and eutrophication). new European Clean Air Package has long-term strategic objective of ‘no exceedance of the critical loads which mark the limits of ecosystem tolerance’. EU biodiversity strategy is ‘aimed at reversing biodiversity loss… deposition encourages the growth of competitive plant species… reducing the structural density’.

policy setting

0

20

40

60

80

100

120

140

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

kilo

ton

ne

s A

mm

on

ia

Dairy Cattle Other Cattle Other Livestock Direct SoilsN-excreted on Pasture Road Transport NEC Target

0

20

40

60

80

100

120

140

160

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Gg

NO

x

Power Stations Residential & Commercial Industrial Agriculture & Forestry Transport Other NEC Target

0

20

40

60

80

100

120

140

160

180

200

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Gg

SO

2

Power Stations Residential & Commercial Industrial Agriculture & Forestry

Transport Other NEC Target

2050

future trends emissions

ecosystem response to emissions protocols reductions in sulphur and nitrogen oxide emissions will reduce ‘acidic deposition’. with respect to sulphur emissions, reductions in ‘acidic deposition’ will lead to improvements in ecosystems health (acidification recovery in surface waters). Reduction in exceedance of critical loads of acidity. with respect to nitrogen emissions, continue exceedance of critical loads of nutrient nitrogen, leading to changes in plant species diversity in natural habitats.

atmospheric deposition EMEP monitoring network

0.0

0.1

0.2

0.3

0.4

0.5

0.6

1990 1995 2000 2005 2010

Non-marine sulphate (mg L–1

)

0.00

0.10

0.20

0.30

0.40

1990 1995 2000 2005 2010

Valentia Observatory

Turlough Hill

The Burren

Ridge of Capard

Oak Park

Glenveagh

Johnstown Castle

Lough Navar

Median concentration

Nitrate (mg L–1

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

1990 1995 2000 2005 2010

Ammonium (mg L–1

)

atmospheric deposition | long-term annual trend (1991–2009) in non-marine sulphate, nitrate and ammonium concentration in precipitation (mg L–1) at EMEP stations

what we expect | studies across Europe have shown changes in lake chemistry associated with decreased SO2 emissions

1997 observations

19

97

ob

serv

atio

ns

upper lake Glendalough, Co. Wicklow

Long-term trend [1984–2010] in surface acidity [pH]

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

1984 1989 1994 1999 2004 2009

pH: mid-lake observations [1984–2010] pH: inflow 3 [1984–2010]

maximum critical load of sulphur

exceedance of critical load of sulphur

reductions in exceedance of critical loads of acidity for surface waters

similar reductions in exceedance of critical loads of acidity for terrestrial ecosystems

however no change in exceedance of critical loads of nutrient nitrogen for terrestrial ecosystems

0

10

20

30

40

50

60

70

0 5 10 15 20 25

Acid grassland (n = 416)

Neutral-calcareous (n = 419)

y = 30.23 - 0.60x R2= 0.12

y = 42.00 - 1.11x R2= 0.22

Sp

ecie

s r

ich

ne

ss

Nitrogen deposition (kg N ha–1

a–1

)

response of grassland plants species diversity to elevated nitrogen deposition

Semi-natural dry grasslands and scrubland facies on calcareous substrates (Festuco-Brometalia) 6210

n Vd

(cm s–1)

z- change point

(kg N ha–1 yr–1)

z+ change point

(kg N ha–1 yr–1)

507 1.0 8.17 8.17

The death toll from air-pollution sources Estimates of worldwide deaths associated with exposure to fine particles in atmospheric pollution provide some surprising results. The findings will guide future research and act as a wake-up call for policymakers.

… Lelieveld and colleagues’ next major finding is that agricultural sources are the second-largest contributor to global mortality from PM 2.5 — releases of ammonia from livestock and fertilizers lead to atmospheric formation of ammonium nitrate and sulfate particles. Agricultural sources are the leading source of mortality in the eastern United States, Russia, Turkey, Korea, Japan and Europe, contributing to more than 40% of the deaths in many European countries.

Meeting greenhouse gas and ammonia emission reduction targets will be particularly challenging… Strategic Environmental Objective: Manage air pollution

SEO Indicator: Air quality measurements from EPA national monitoring programme

conclusions sulphur emissions reductions have driven reductions in acidic deposition, (chemical) recovery of surface waters, reductions in exceedance of critical loads of acidity. nitrogen emissions (specifically ammonia), may lead to significant changes in (loss of) plant species diversity in natural habitats, i.e., natura 2000 areas. there are limited national observations of ammonia.

Convention on Long-range Transboundary Air Pollution