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Critical Loads - Thomas Cummins, UCD
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
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
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)
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.
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
Air monitored using Polyurethane Foam (PUF) samples [following Global Atmosphere Passive Sampling (GAPS) Network, which has one site in Malin head). Lake sampling using SemiPermeable Membrane Devises (SPMDs)]. Very little if any POP data for Ireland. ??? Soils by simple sampling; PBDEs Polybrominated diphenylethers; Perfluorooctane sulphonate.
Assessment of POPs will incorporate back-trajectory cluster analysis. Evaluate difference in clusters at air (PUF) monitoring stations for each exposure. ??? Which lines are shown by the red clouds? What are the numbers. Is acknowledgement OK???
During 1997 200 lakes sampled, 150 of the more remote acid sensitive lakes resampled during 2008. Table editable? Why separate first two boxes of analyses? Deuterium? What for? Why is Hg not a trace metal? How were 200 lakes reduced to 150?
Reversed axes possible?
Critical loads of acidity for soils; weathering-rate map updated by new soil sampling. Weathering rate map (1999) and acid sensitive soils sampled (2008–2009). Sampling scheme including topsoil and subsoils (3 depths), a trncated version of the National Soil Database sampling method. Bulk density, LOI, PSA, exch. cations, pH, and some for CNS; total oxides to follow, used to estimate weathering rate for input to PROFILE model.
Development of biodiversity indicators for critical loads of nutrient nitrogen Map shows 1970 releve (and soil chemical) locations. 2009–10 samples from BEC consultants, NPWS-funded; coordinates to follow, species-diverse grasslands and uplands.
Ammonia is nationally an important contribution to nitrogen deposition. Measurements confirm the predictions of inventory estimation, but a higher network density is needed, and