Riverside CL meeting, Feb. 15-18, 2005 Canadian accomplishments on Critical Load Mapping Forests Rock Ouimet, MRNFP, QC Paul A. Arp, UNB, N.B. Shaun Watmough, TU, ON Julian Aherne, TU, ON Ian DeMerchant, NRCan, N.B. Surface waters Dean Jeffries, EC, ON Jacques Dupont, MENV, QC Jill Franklyn, EC, ON David Lam, EC, ON Fred Norouzian, EC, ON Isaac Wong, EC, ON
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Riverside CL meeting, Feb. 15-18, 2005 Canadian accomplishments on Critical Load Mapping Forests Rock Ouimet, MRNFP, QC Paul A. Arp, UNB, N.B. Shaun Watmough,
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2005 EC report on acid deposition science assessmentFirst mapping of terrestrial CL for eastern CanadaUpdated mapping of aquatic CL for eastern and first
mapping of CL for western Canada
4Riverside CL meeting, Feb. 16-18, 2005
Definitions
Critical load « The highest deposition of acidifying compounds that will not
cause chemical changes leading to long-term harmful effects on ecosystem structure and functions »
Nilsson and Grennfelt (1988)
« A quantitative estimate of an exposure to one or more pollutants below which significant harmful effects on specified elements do not occur according to present knowledge »
UN ECE (1994)
« A quantitative estimate of an exposure to one or more pollutants below which the probability of long-term unacceptable effects on specified elements is acceptable according to present knowledge and policy »
Barkman (1998)
5Riverside CL meeting, Feb. 16-18, 2005
Chemical thresholds and methods : the steady-state approach
Aquatic Biotic toxicity of the lower aquatic food web Acid neutralizing Capacity (ANC) = 40 µeq/L (~pH = 6.0) Model : Expert (Lam et al. 1994) SSWC (Henriksen & Posch 2001)
Terrestrial Maintaining current soil base saturation of forest soils Log(KGibb) = 9.0 BC/Al = 10 (M/M) The Simple Mass-Balance Model (SMB)