Presentation from EPA Transboundary Research Workshop, Galway, 8th and 9th September 2010.

1. Critical Loads Julian Aherne, Trent University, Canada Thomas Cummins, University College Dublin

2. Definition of critical load: "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" (Nilsson and Grennfelt, 1988) Keywords to note: quantitative significant sensitive elements present knowledge

3. 2007-CCRP-4.4.4b: Re-sample 1997 acid lakes survey Baseline database on acid sensitive soils Baseline on persistent organic pollutants (POPs) 2008-CCRP-4.1a: Determine critical loads of acidity for soils and waters Determine critical loads for nutrient nitrogen . EPA-funded projects at Trent–UCD

4. Passive air samples for POPs (n = 14, blue; 3-month exposures during 2009–2011). POPs in soil & water (n = 7, green). [PCBs, pesticides and PAHs (PBDEs and PFOS to follow)] Persistent Organic Pollutants (POPs) Networks

5. Back-trajectory analysis Cian Woods & Rodrigo Caballero, UCD CASL

6. Upland acid-sensitive lakes (n = 150) sampled during 1997 & 2008 for major anions and cations Upland lakes

7. Statistically significant decrease (by 30 %) in concentrations of lake sulphate Sulphate decrease in upland lakes, 1997–2008 2008 1997 Sulphate (µmol ± L -1 )

8. Trends in sulphur dioxide (SO 2 ) emissions for Ireland (EPA, 2009) and non-marine sulphate (nmSO 4 2– ) deposition (three-year running mean of five deposition stations) in Ireland, 1995–2007. Annual emissions and deposition are highly correlated (r 2 = 0.9). Declining emission & deposition of sulphur

9. Long-term rainfall chemistry stations (1991–2009) Precipitation non-marine SO 4 2– Valentia Lough Navar Brackloon Cloosh 0 1 2 3 4 5 6 7 1990 1995 2000 2005 2010 Roundwood

10. Weathering rate (mol ± ha -1 year -1 ) Acid-sensitive soils sampled 2008–9 (forests, green; lake sites, blue; upland acid mineral soil, brown)

11. Historical (1970) and new plant relevé and soil-chemical observations used to identify chemical niches for grassland species with respect to N. Approximately 1000 soil samples with plant relevés a cquired 2009–10 for chemical analysis. 1970 Empirical chemical habitats

12. Ammonia (µg m –3 ) Ammonia by emission-inventory & measurement 1999 0.0–0.6 0.6–1.2 1.2–1.8 1.8–2.4 2.4–3.0 > 3.0

13. Calls for data (C4D) on critical loads (CL) under UNECE 2010: major call for acidity and nutrient nitrogen CL 2008: submission on C4D 2007: submission on C4D 2005: significant dynamic modelling effort to meet C4D 2003: update to CL database for dynamic modelling 2000: C4D 1998: C4D x 2 1997: C4D, CL database established by UCD 1996: EPA funded CL project (UCD 1996–1999) 1991: EPA report on critical loads (M. McGettigan)

14. UK–Ireland methods review Critical Load for nutrient N year -1

16. Acknowledgements

17. Ecosystem Response Linking the ecosystem response to deposition level is the central principle of the critical load approach. receptor: the ecosystem under consideration. biological indicator: the organism selected to represent the receptor. chemical criterion: the chemical measure affected by atmospheric deposition used to predict the risk of damage to the biological indicator. critical limit: the most unfavourable value that the chemical criterion may attain without long-term harmful effects to ecosystem structure and function.

18. Quote

19. Critical-load mapping Critical loads are linked to an area representing one (or more) ecosystems, as such, they are best represented as maps. Map-based data is very efficiently handled with a Geographical Information System (GIS).

20. Modelling approaches L evels of sophistication Level 0 semi-quantitative Level I mass balance models Level II dynamic models complexity data requirements certainty

21. CLRTAP