CRITICAL LOADS ONTARIO

Transcription

1 CRITICAL LOADS ONTARIO Final Report: Calculating Critical Loads of Acid Deposition for Forests in Ontario using the NEG-ECP Working Group Protocol on Critical Loads Shaun A. Watmough, Julian Aherne and Peter Dillon Environmental and Resource Studies, Trent University Peterborough, Ontario, K9J 7B8 November 2003 Critical Loads Ontario Report No. 1

2 Project Title: Critical Loads Ontario (CLONT) Report Title: Calculating Critical Loads of Acid Deposition for Forests in Ontario using the NEG-ECP Working Group Protocol on Critical Loads Project Leader: Peter Dillon Scientific Team Members Dr Peter Dillon Dr Shaun A. Watmough Dr Julian Aherne Environmental and Resource Studies Trent University, Peterborough, Ontario K9J 7B8 Telephone: (705) x Telephone: (705) x7536 Telephone: (705) x Progress Report: Final Report November 2003 Acknowledgements Funding source: Environment Canada (contract number KM )

3 Critical Load: a quantitative estimate of exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge Nilsson and Grennfelt 1988 Critical Loads Ontario Report Series No. 1. Watmough, S.A., Aherne, J. and Dillon, P.J., Calculating Critical Loads of Acid Deposition for Forests in Ontario using the NEG-ECP Working Group Protocol on Critical Loads. Final Report, November Trent University, Ontario, 5 pp. No. 2. Watmough, S.A., Aherne, J. and Dillon, P.J., Relating Exceedance of Critical Load with Biological Effects at Ontario Forests. Final Report, March Trent University, Ontario, 15 pp. No. 3. Aherne, J., Watmough, S.A. and Dillon, P.J., The Relative Impact of Acid Deposition and Forest Harvesting on Soil and Surface Water Chemistry. Final Report, November Trent University, Ontario, 15 pp. Reports are available on-line:

4 Table of Contents 1. Introduction Statement of Work Data Sources: Theme Map Attribute Climate Soil and Land Cover Nutrient Export Deposition Summary of Results...2 Acknowledgement...3 References...3 Appendix 1. Critical Load and Exceedance Maps...4

5 1. Introduction Critical loads, defined as a quantitative estimate of an exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge, have been widely accepted in Europe as a basis for the development of effects-based air pollution control strategies, as evidenced by the Oslo Protocol (1994 Protocol on Further Reduction of Sulphur Emissions) and the Gothenburg Protocol (1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone). In October 1998, Canadian Energy and Environment Ministers signed The Canada- Wide Acid Rain Strategy for Post-2000, in which they committed to take steps over the long-term to solve the acid rain problem in eastern Canada and prevent one in western and northern Canada. The Strategy set a long-term goal of achieving the threshold of critical loads for acid deposition across Canada. Critical loads and current exceedances have been determined and mapped for upland forests in eastern Canada (Newfoundland, Prince Edward Island, Nova Scotia, New Brunswick, Quebec) following guidelines established by the New England Governors- Eastern Canadian Premiers (NEG-ECP) Environmental Task Group on Forest Mapping (NEG-ECP 2001). Critical loads have not been mapped for Ontario. This report presents the determination and mapping of critical loads of acid deposition (and exceedances) for upland forest soils in Ontario. For consistency with eastern Canada, the methodology followed the protocol and guidelines established by the NEG- ECP. 2. Statement of Work A critical load map of acid deposition for forests in Ontario was developed using the protocol established by the NEG-ECP Environmental Task Group on Forest Mapping. Exceedances of the critical load were estimated by comparing critical load values with S (sulphur) and N (nitrogen) deposition ( average). The critical load and exceedance maps are presented in Appendix 1. The map was produced following guidelines established by the NEG-ECP so it is directly comparable to maps produced for other provinces and states in eastern North America. Critical loads for forest soils was calculated by: (1) CL( S + N) = BCdep Cl dep + BCw Bcu + Ni + Nu + Nde Alk le( crit ) where BC dep = base cation (BC = Ca 2+ + Mg 2+ + K + + Na + ) deposition; Cl dep = chloride deposition; BC w = base cation weathering; Bc U = net base cation uptake (Bc = Ca 2+ + Mg 2+ + K + ); N i = net nitrogen immobilisation rate in soil; N u = net nitrogen uptake; N de = net denitrification rate and Alk le(crit) = critical alkalinity leaching rate. Units are in eq ha 1 yr 1. Data sources for production of the map are described below (Section 3). 1

6 3. Data Sources: Theme Map Attribute 3.1. Climate Runoff: runoff data obtained from Cumming Cockburn Ltd. (unpublished map). Mean annual temperature (Source: Environment Canada) Soil and Land Cover The CANSIS database, which is comprised of more than 1400 soil polygons (Soils Landscape of Canada, scale 1:1,000,000), was used to describe soil and land cover for Ontario. This data set contained information on soil type, soil texture, soil depth, bulk density, and dominant land cover. Online: sis.agr.gc.ca/cansis/nsdb/slc/intro.html Nutrient Export Estimates of nutrient removal due to harvest were obtained from permanent sampling plots located throughout Ontario. Data for tree species, age and size at each plot were provided by the Ontario Ministry of the Environment. For each plot, information on tree species, size and age was used to estimate annual increase in biomass. Nutrient export was calculated using published and unpublished nutrient content data for stems and bark for each species. All scenarios assumed stem-only harvesting and in regions were no sampling plots existed; southern and northern Ontario; nutrient uptake was set to Deposition Deposition data for S, N and base cations (Ca 2+ (calcium); Mg 2+ (magnesium); K + (potassium) and Na + (sodium)) were provided by Environment Canada (Ro and Vet 2002). We used the wet deposition average, multiplied by 1.2 to account for dry deposition to calculate current critical loads and exceedances. 4. Summary of Results Critical load maps for S and N for forests in Ontario were calculated along with current exceedances of the critical load. Both maps have already been given to Heather Morrison, but are also included as an attachment. The main details are as follows: Critical loads for S and N were calculated for forests in Ontario (737,145 km 2 ) (Map 1). Critical loads were not calculated for urban and agricultural areas that dominate southern Ontario, or parts of northern Ontario were all data were not available. The median base cation weathering rate was 584 eq ha 1 yr 1 ; although weathering rates are between 117 and 4566 eq ha 1 yr 1. Highest weathering rates generally occur in southern Ontario or in clay-belt areas of northern Ontario. The median base cation deposition rate was 75 eq ha 1 yr 1, but was between 51 and 281 eq ha 1 yr 1. Highest base cation deposition is in southern Ontario. The median S deposition level was 164 eq ha 1 yr 1, but ranged between 94 and 517 eq ha 1 yr 1. 2

7 The median N deposition level was 260 eq ha 1 yr 1, but ranged between 180 and 675 eq ha 1 yr 1. Deposition of both S and N are highest in southern Ontario and generally decrease northwards. The median base cation uptake value was 96 eq ha 1 yr 1, but ranged between 30 and 333 eq ha 1 yr 1. The median N value was 52 eq ha 1 yr 1, but ranged between 14 and 144 eq ha 1 yr 1. The total forest area considered to be harvested in the mapping exercise was 378,514 km 2 (51 % of total mapped area). The median critical load CL(SN) was 1020 eq ha 1 yr 1, but ranged between 288 and 6274 eq ha 1 yr 1. Lowest critical loads were generally in central and north-west Ontario (Appendix 1. Map 1). The median exceedance of the critical load was 166 eq ha 1 yr 1, but ranged between 4 and 650 eq ha 1 yr 1. Exceedance of the critical load was greatest in central Ontario (Appendix 1. Map 2). The total forest area where S and N deposition currently exceeds the critical load is 155,440 km 2. This represents approximately 21 % of the mapped area for Ontario, or 41 % of the productive forest area. Acknowledgement This work was funded by Environment Canada (contract number KM ). The authors gratefully acknowledge the Canadian National Atmospheric Chemistry (NAtChem) Database and its contributing agencies/organisations for providing the precipitation chemistry data used in this publication. Forest plot data for forest nutrient uptake estimates were provided by the Ontario Ministry of Natural Resources (OnTAP). References NEG-ECP Critical Load of Sulphur and Nitrogen Assessment and Mapping Protocol for Upland Forests. New England Governors and eastern Canadian Premiers Environment Task Group, Acid Rain Action Plan, Halifax, Canada. Nilsson, J. and Grennfelt, P., (eds) Critical Loads for Sulphur and Nitrogen. Report from a Workshop held at Skokloster, Sweden March, 1988, Miljorapport 1988:15, Nordic Council of Ministers, Copenhagen, Denmark. Ro, C.U. and Vet, R.J., Analyzed data fields from the National Atmospheric Chemistry Database (NAtChem) and Analysis Facility. Air Quality Research Branch, Meteorological Service of Canada, Environment Canada, Toronto, Canada. 3

8 Appendix 1. Critical Load and Exceedance Maps < > 1000 Critical loads (eq ha 1 yr 1 ) Map 1. Critical loads (eq ha 1 yr 1 ) for upland forest soils in Ontario.

9 exceedance > 100 exceedance no exceedance no exceedance > 100 Exeedance (eq ha 1 yr 1 ) Map 2. Critical load exceedances (eq ha 1 yr 1 ) for upland forest soils in Ontario.