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Canada - United States Air Quality Agreement

2002 Progress Report

SECTION IV  Scientific Cooperation

This section focuses on U.S. and Canadian progress under Annex 2 of the Air Quality Agreement to cooperate and to exchange scientific information related to transboundary air quality issues.

Data Measurement and Analysis

EMISSIONS INVENTORIES

Emissions inventories provide the foundation for air quality management programs. They are used to identify major sources of air pollution, provide data to input into air quality models, and track the progress of control strategies. This section addresses mainly SO₂, NO_x, and VOCs. SO₂ and NO_x emissions are the dominant precursors of acidic deposition; NO_x and VOCs are primary contributors to the formation of ground-level ozone; and all three pollutants contribute to the formation of PM.

This section outlines emission trends estimates for SO₂, NO_x, and VOCs for both Canada and the United States, reflecting new methodologies for determining total estimates and using new models and results. In addition to the joint emission trends data, the latest available data (1999) on sources of emissions by sector are presented in figures 4, 6, and 7. Canadian emissions data are preliminary.

Sulphur Dioxide

Electric utilities continued to contribute to the majority of total North American SO₂ emissions in 1999. In the United States, well over 90% of these emissions come from coal combustion. Non-ferrous mining and smelting is the main contributor to anthropogenic sources of SO₂ in Canada and along with industrial coal combustion, is a primary source in the United States. Overall, a 38% reduction in SO₂ emissions is projected in Canada and the United States from 1980 to 2010. In the United Sates, these reductions are mainly a result of controls in electric utilities under the Acid Rain program and desulphurization of diesel fuel under Section 214 of the 1990 CAAA. In Canada, they are mainly attributed to reductions from the non-ferrous mining and smelting sector and electric utilities as part of the Canada-Wide Acid Rain Strategy program.

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Nitrogen Oxides

The principal anthropogenic source of NO_x emissions remains the combustion of fuels in stationary and mobile sources. Motor vehicles, residential and commercial furnaces, industrial and electric utility boilers and engines, and other equipment contribute to this category.

U.S. reductions in NO_x emissions are attributed to controls in electric utilities under the Acid Rain Program, the estimated controls associated with EPA Regional Transport NO_x SIP Call, the Tier 2 Tailpipe Standard, and Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Rulemaking.

Canadian NO_x emissions as portrayed in figure 5 show a relatively constant level since 1990 and into the future; however, this forecast does not include the substantial NO_x reductions that will result from the implementation of the Ozone Annex, including the stationary source commitments for NO_x emissions and the 10-year vehicle and fuels agenda, which implement the Tier 2 Tailpipe Standards, among other initiatives.

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Overall estimated trends for anthropogenic emissions of NO_x in Canada and the United States from 1990 to 2010 are shown in figure 5.

Volatile Organic Compounds

Anthropogenic emissions of VOCs continue to de dominated by on-road vehicles and solvent use source categories (e.g., surface coating, consumer products, and degreasing). In 1999, these two categories contributed to almost 60% of VOC emissions in the United States and 37% in Canada. The primary contributor to VOC emissions in Canada in 1999 was the upstream oil and gas industry. Emissions in Canada and the United States are expected to decline by 40% from 1980 through 2010. U.S. reductions in recent years are a result of the control of VOCs through various maximum achievable control technology (MACT) standards. Overall estimated trends in anthropogenic VOC emissions for Canada and the United States from 1980 to 2010 are shown in figure 8.

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ACID DEPOSITION MONITORING

Airborne pollutants are deposited on the earth's surface by three processes: wet deposition, dry deposition, and deposition by cloudwater and fog. Wet deposition is relatively easy to measure through the analysis of rain and snow.

Wet and dry deposition are monitored in Canada and the United States through well-established networks that measure the chemical composition of air and precipitation. Both countries contribute their monitoring results to an integrated data set from which maps are produced of sulphate and nitrate wet deposition across eastern North America.

Wet deposition in Canada is measured by various federal, provincial and territorial governments. Environment Canada operates the Canadian Air and Precipitation Monitoring Network (CAPMoN) with 21 measurement sites in Canada and 1 in the United States. A map of the CAPMoN measurements sites can be found at the following website: http://www.msc.ec.gc.ca/capmon/Index_e.cfm. Provincial wet deposition monitoring networks are operated by the governments of British Columbia, Alberta, Quebec, New Brunswick, Nova Scotia, Newfoundland and the Northwest Territories.

Dry deposition in Canada is measured at 13 of Environment Canada's CAPMoN sites. No dry deposition measurements are made by the provinces or territories.

CAPMoN sites across Canada are currently being upgraded under the implementation of the Ozone Annex and special funds from the Acid Rain Program. The upgrades include an increase in the number of sites, hardware improvements and an increase in the number of pollutants monitored at selected sites. Also included is the establishment of a new Canada/U.S. Intercomparison site at Frelighsburg, Quebec

The United States has three acid deposition monitoring networks: NADP/NTN; AIRMoN, which is part of NADP; and CASTNet. NADP/NTN has 238 sites monitoring wet deposition, including 15 collocated dry deposition sites, monitored weekly. AIRMoN has 10 sites monitoring wet deposition and 5 sites monitoring dry deposition daily. CASTNet has 79 sites monitoring dry deposition and rural ozone concentrations.

By comparing the wet deposition maps before and after the 1995 Phase 1 emission reductions under the Clean Air Act Amendments, it has been possible to assess the impact of the emission decreases on large-scale wet deposition.

Information and Data Exchange

Environment Canada and EPA are collaborating to improve Canadian and U.S. atmospheric deposition measurements and to enhance the exchange, accessibility, and analysis of data within the two countries. Under a cooperative agreement initiated this year, the two governments are planning to establish a common, cooperative, Canadian–U.S. deposition database, analysis, and Web-based mapping capability that will include data from the NADP, CASTNet, and AIRMoN networks as well as Canadian federal and provincial acid rain monitoring networks.

Status and Trends

Five-year average sulphate wet deposition for the years 1996-2000 (figure 11) is considerably reduced from that for the five-year period prior to the Phase 1 reductions (1990–1994). For example, the large area that received 25 to 30 kg/ha/yr (kilogram per hectare per year) of sulphate in 1990-94 almost disappeared in 1996–2000. The marked shrinkage of wet deposition strongly suggests that the Phase 1 SO₂ emission reductions were successful in reducing the sulphate wet deposition over a large section of eastern North America.

For nitrate wet deposition, the spatial patterns shown in figures 10 and 12 are approximately the same before and after the Phase 1 emission reductions. This suggests that the minimal reductions in NO_x emissions after Phase 1 resulted in minimal changes to nitrate wet deposition over eastern North America.

The data used for this assessment came from national and provincial networks in Canada and from national networks in the United States. Five-year average wet deposition maps were produced in order to minimize meteorological variability that seriously affects annual wet deposition patterns. The 1996–2000 maps are less certain in the provinces of Ontario and Quebec because of the lack of provincial data in 1999 and 2000.

Analyses of National Atmospheric Deposition Program/National Trends Network (NADP/NTN) data continued to show dramatic reductions in sulphate deposition over the past decade. Data for 1998–2000 showed up to 30% reductions over a large area of the eastern United States compared with 1989–1991 data. The greatest reductions were in the northeastern United States, where many sensitive ecosystems are located.

Wet Sulphate and Nitrate Deposition in 1990-1994 and 1996-2000

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NADP/NTN data for nitrate deposition showed variable decreases in nitrate deposition in the Northeast and increases in the Upper Midwest and Rockies for the 1998–2000 period compared with the 1989–1991 period. Nitrate deposition was 10% to 20% less in New York and West Virginia; in Maine, 10% less. Nitrate deposition percentages in low deposition areas in the western United States increased by 20% to 50%.

A trend analysis for the 1990 to 1999 period at 34 eastern U.S. Clean Air Status and Trends Network (CASTNet) sites showed significant declines in SO₂ and sulphate concentrations in ambient air. The average SO₂ reduction was 32%; for sulphate the reduction was 24%. Patterns were similar to those reported in the last Progress Report.

In the early 1990s, ambient SO₂ concentrations in the rural eastern United States were highest in western Pennsylvania and along the Ohio Valley in the vicinity of Chicago and Gary, Indiana. Large SO₂ air quality improvements can be seen by comparing the 1990 to 1992 period with the 1999 period. The largest decrease in concentrations is noted in the vicinity of Chicago and throughout states bordering the Ohio Valley (Illinois, Ohio, Pennsylvania, Kentucky, and West Virginia). The highest SO₂ concentrations in the rural parts of the eastern United States are concentrated in southwestern Pennsylvania.

As reported in the last Progress Report, CASTNet data for ambient concentrations of nitrogen containing compounds from 1990 to1999 from sites in the rural eastern United States did not change appreciably. The highest concentrations were found in Ohio, Indiana, and Illinois.

GROUND-LEVEL OZONE MONITORING AND MAPPING

Ground-level ozone continues to be a pervasive pollution problem throughout many areas of the United States and southern Canada. Ozone, formed by the reaction of VOCs and NO_x in the presence of heat and sunlight is not emitted directly into the air but rather is readily formed in the atmosphere by photochemical reactions under summer sunlight.

Ozone Monitoring

Both governments have extensive ground-level ozone monitoring programs.

Ambient monitoring of ground-level ozone and precursors is conducted throughout Canada under the National Air Pollution Surveillance (NAPS) network, a joint program of the federal and provincial governments. As of December 31, 2000, 164 ozone monitoring sites were reporting data to NAPS.

Data records for ozone, NO₂, NO, and NO_x date back to the early 1980s, and special VOC measurements have been collected since 1989 at more than 40 sites across Canada. Most monitoring of ground-level ozone and precursors is focused in the country's densely urbanized regions. In addition, Environment Canada operates CAPMoN which samples at regionally representative, non-urban locations across Canada.

The national ambient air quality monitoring program-the State and Local Air Monitoring Stations (SLAMS) network-is implemented by state and local air pollution control agencies. The SLAMS network consists of three major categories of monitoring stations: (1) those that are SLAMS only; (2) National Air Monitoring Stations (NAMS); and (3) Photochemical Assessment Monitoring Stations (PAMS). PAMS measure a variety of criteria and noncriteria pollutants, specifically ozone precursors. EPA operates CASTNet, which provides ozone levels in rural areas as well as dry acidic deposition levels and trends.

Currently, there are 646 SLAMS and 189 NAMS sites for ozone which are used for SIP support, state/local data, national polcy support, national trends development, measurement of maximum concentrations and population exposures, EPA regional office oversight, and EPA headquarters oversight. Additionally, the state, local, tribal, and other nongovernmental agencies operate approximately 332 special purpose monitors (SPM) for ozone. These are generally used for special studies and state/local oversight. The SPM are also used for regulatory purposes, including designations. There is little distinction among the state, local, or tribal sites that are SLAMS, NAMS, or SPM for ozone-all types are used as described above.

The PAMS networks measure ozone precursors as required by the 1990 Clean Air Act Amendments (CAAA) to monitor the most severe ozone nonattainment areas. The PAMS requirements were designed to provide information on the roles of ozone precursors, pollutant transport, and local meteorology in the photochemical process and to assist in information gathering for proposed ozone control strategies. In 2000, approximately 83 PAMS were in operation in five regions of the United States-the Northeast, the Great Lakes area, Atlanta, Texas (primarily Houston), and California.

Ozone Mapping

AIRNOW

In 2001, Canadian and American jurisdictions (primarily provinces and states) expanded EPA's AIRNOW, real-time air quality program, to include data and develop maps from six Canadian provinces. The real-time ozone air quality maps include the provinces of New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward Island, and Quebec and the northeastern United States. The maps were generated using the ozone standard for Canada and the Air Quality Index (AQI) for the United States. Work is underway to expand the Canadian ozone mapping effort to include data from British Columbia in conjunction with Washington State in the summer of 2002.

For the United States, the project completes existing smog advisory programs and the smog forecasting program. Forty states are participating in the AIRNOW program.

Air Quality Index

Over the past year, Canada has been engaged in a multi-stakeholder review of the air quality index (AQI) system in use in the country. The primary objective has been to ensure that the index becomes more reflective of the health risk of air pollution and a better means of providing people with information they can use to protect their health. Issues considered include the relationship between pollutants and combined exposures; the distinction between air pollution management targets and relative risks; monitoring capabilities and limitations; national consistency versus regional flexibility; associated health messages; and the marketing challenges. A report containing recommendations will be available this fall. Decisions about real-time reporting of ambient air quality remain at the provincial or local level, so the next step will be to develop a mechanism that brings together decision makers and stakeholders for the ongoing coordination and implementation of changes to the AQI.

EPA's AQI continues to provide data on health risks associated with increased pollutant concentrations, pollutant-specific health and cautionary statements on effective risk reduction behaviour, an AQI update for use by the media, an ozone subindex in terms of 8-hr average concentrations, and a subindex for PM (PM_2.5). (For AQI on the Internet, see www.epa.gov/airnow/publications.html.)

Air Quality Reporting Data

As part of the new Ozone Annex to the Air Quality Agreement (see section II, and appendix B), Canada and the United States agreed to report on air quality data beginning in 2002. Data include ambient ozone concentrations in the form of applicable standards 10-year trends in ambient ozone concentrations, ambient VOC concentrations, 10-year ambient VOC concentrations, ambient NO_x concentrations, and 10-year trends in ambient NO_x.

Data were collected for all sites within 500 km of the Canada-U.S. border, and all available data were used to create the contour maps presented below. However, only sites meeting certain data completeness requirements were used in the statistical trends analysis. For ozone, these criteria required that each annual fourth highest daily maximum 8-hr concentration be based on 75% or more of all possible daily values during the EPA designated ozone monitoring season and that eight or more annual values in the 10-year period analyzed (1991-2000) are valid.

Trend sites for NO_x have eight or more valid annual averages where a valid average is based on 50% or more of all possible hourly averages. Hydrocarbon monitoring stations were included as trend sites if there were three or more annual averages reported. The completeness criteria were relaxed for hydrocarbons because these data are far more limited than is the case for NO_x and ozone. Additionally, only urban monitoring sites in Canada were included in trend calculations to provide trends that are roughly comparable to the urban-oriented U.S. monitoring network.

These data are presented in figures 13-17 and in Appendix C (figures 21-23). Figure 14 shows the annual fourth highest daily maximum 8-hour ozone averaged over the period 1998-2000. The highest values are generally near major urban areas in the eastern region of the U. S. Ozone concentrations are based on monitoring data from ozone sites located within approximately 500 km of the U.S./Canadian border depicted in Appendix C (five Canadian sites subject to significant NO scavenging or at high altitude excluded). Figure 15 shows the annual fourth highest daily maximum 8-hour ozone averages over the period 1998-2000. The lowest values are generally found in southern Manitoba and southern British Columbia near Vancouver. Ozone concentrations are based on monitoring data from ozone sites located within approximately 500 km of the U.S./Canadian border depicted in Appendix C (five Canadian sites subject to significant NO scavenging or at high altitude excluded).

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