Canada-United States Air Quality Agreement: Progress Report 2016: Section 3

Scientific and technical cooperation and research - ­Emission inventories and trends

The United States and Canada have updated and improved their emission inventories and projections for a number of important pollutants, including particulate matter less than or equal to 10 microns (PM10), PM2.5, VOCs, NOX, and SO2, to reflect the latest information available. In Canada, the emission inventory data are for the year 2014. The United States emissions data are based on national and state-level trend information from the 2014 National Emission Inventory.

Figure 18 shows the distribution of emissions by source category grouping for SO2, NOX, and VOCs. The following observations can be made about this figure:

  • Canadian SO2 emissions originate mostly from the non-ferrous smelting and refining industry, upstream petroleum industry, and coal-fired electric power generation. The relative contribution from electric power generation utilities is lower in Canada due to the large hydroelectric and nuclear capacity in place.
  • SO2 emissions in the United States originate primarily from coal-fired combustion in the electric power sector and from industrial boilers.
  • In Canada, non-road and on-road vehicles account for the greatest portion of NOX emissions, followed by the upstream petroleum industry.
  • Similarly, in the United States, non-road and on-road vehicles account for the greatest portion of NOX emissions, followed by industrial sources.
  • Solvent utilization and industrial sources contribute more than half of the total VOC emissions in both Canada and the United States.

Figures 19, 20, and 21 show emissions from 1990 through 2014 in Canada and the United States, for SO2, NOX, and VOCs, respectively. Both countries have seen major reductions in emissions.

In Canada, the reductions in SO2 emissions came from the non-ferrous smelting and refining industry, coal-fired electric power generation, and the upstream petroleum industry. For NOX, the reductions were from coal-fired electric power generation and transportation-related sources. The VOC reductions came from transportation-related sources such as off-road and on-road vehicles.

In the United States, the reductions in SO2 emissions came mostly from electric power generation and industrial sources. Reductions in NOX emissions came from on-road and off-road transportation, and from electric power generation. Reductions in VOC emissions came from on-road and off-road transportation as well as from other anthropogenic sources.

Scientific cooperation

Figure 18.  Canada and the United States National Emissions by Sector for Selected Pollutants, 2014

Long description

Figure 14 depicts U.S. and Canada national emissions by sector for selected pollutants in 2014. It includes six pie charts. This figure shows that SO2 emissions in the United States originate primarily from coal-fired combustion in the electric power sector and from industrial boilers. Canadian SO2 emissions originate mostly from the non-ferrous smelting and refining industry, upstream petroleum industry, and coal-fired electric power generation. The relative contribution from electric power generation utilities is lower in Canada due to the large hydroelectric and nuclear capacity in place. In Canada, on-road and non-road vehicles account for the greatest portion of NOx emissions, followed by the upstream petroleum industry. Similarly in the United States, non-road and on-road vehicles account for the greatest portion of NOx emissions, followed by industrial sources. Solvent utilization and industrial sources contribute more than half of the total VOC emissions in both Canada and the United States.

Notes: Emissions exclude natural sources (biogenics and forest fires).

Percentages may not add up to 100 due to rounding.

Sources: ECCC, 2016; EPA, 2016

Figure 19.  National SO2 Emissions in Canada and the United States from All Sources, 1990–2014

Source: ECCC and EPA, 2016

Long description

Figure 16 depicts SO2 emission trends in the U.S. and Canada in million short tons and million metric tons, respectively, from 1990 to 2014. In Canada, the reductions in SO2 emissions came from the non-ferrous smelting and refining industry, coal-fired electric power generation and the upstream petroleum industry.

In the U.S., the reductions in SO2 emissions came from electric power generation and industrial sources.

Figure 20.  National NOX Emissions in Canada and the United States from All Sources, 1990–2014

Source: ECCC and EPA, 2016

Long description

Figure 20 depicts NOx emission trends in the U.S. and Canada in million short tons and million metric tons, respectively, from 1990 to 2014. In Canada, the NOx, reductions were from coal-fired electric power generation and transportation-related-sources. In the U.S., the reductions in NOx emissions came from on-road and off-road transportation as well as other anthropogenic sources.

Figure 21.  National VOC Emissions in Canada and the United States from All Sources, 1990–2014

Source: ECCC and EPA, 2016

Long description

Figure 21 depicts VOC emission trends in the U.S. and Canada in million tons and million tonnes, respectively, from 1990 to 2014. In Canada, the VOC reductions came from transportation-related sources such as off-road and non-road vehicles. In the U.S., the reductions in VOC emissions came from on-road and off-road transportation as well as other anthropogenic sources.

Air Quality Model Evaluation International Initiative

Since its start in 2008, the Air Quality Model Evaluation International Initiative (AQMEII) has been coordinated by the European-Commission Joint Research Center (JRC) and the EPA. The primary goal of this project is to promote the collaboration of the European and North American regional scale air quality modeling communities on evaluation of air quality models. The key elements driving the AQMEII process are regular, dedicated workshops; the organization of international model evaluation studies; and the dissemination of findings from these studies in the peer-reviewed literature.

Phase 2 of AQMEII began in 2012 and focused on applying and evaluating online coupled or integrated chemistry transport models and meteorological models. It is well known that atmospheric dynamics and composition are interconnected, that variations in heat distribution affect atmospheric flows and physics, and that atmospheric optical and heat properties depend on atmospheric composition. An online coupled model is a model in which all these feedback loops are partially or completely closed. This online coupled or integrated modeling approach leads to a higher level of complexity in model development, application, and evaluation, but at the same time also yields intrinsic consistency in the model results.

The primary focus of Phase 2 was on simulating air quality for the year 2010, but updated inputs were also prepared for 2006 for North America to facilitate dynamic evaluation studies. A common set of anthropogenic emissions and chemical boundary conditions was prepared and used by all modeling groups. Over 20 groups took part in this project, including EPA and ECCC. JRC and ECCC collected, compiled, and harmonized a massive amount of monitoring and observation data for model evaluation. The analysis of model results and comparison with observations was distributed throughout the community of participants. Over 24 papers were included in a special journal issue in Atmospheric Environment. Fourteen of these papers were co-authored by researchers from EPA and/or ECCC, including six papers that had an EPA or ECCC lead author. The body of work contained in this special issue represents a first step in the systematic evaluation of online coupled modeling systems through a multi-model intercomparison approach. A key recommendation is that future work should focus on shorter-duration, process-focused sensitivity simulations, in order to better inter-compare process representations and model coupling methodologies. Another important finding is that inter-model variability typically is greater than the feedback effects simulated with a given model. This implies that factors other than feedback effects such as emissions, boundary conditions, and process representations of chemistry and/or transport remain the key determinants for overall model performance. However, within a given model, the feedback effects were shown to be capable of improving both meteorological and chemical forecasts, especially for specific episodes, and hence, represent a fruitful direction for future research.

Some of the other highlights of findings from Phase 2 of AQMEII include:

  • It is important to include interactions between meteorology and chemistry (especially aerosols and ozone) in online coupled models;
  • Aerosol indirect and direct effects often counteract each other - direct effects are weaker on the annual scale;
  • The aerosol indirect effect (cloud microphysics implementation) is a prime cause of model differences; and
  • The representation of aerosol indirect effects is incomplete/poor and needs to be further developed and improved in online coupled models.

A key finding from AQMEII Phase 2 (as well as previous global model simulations under the Task Force on the Hemispheric Transport of Air Pollution (TF-HTAP) model intercomparison) was that global transport of certain pollutants may exert a significant seasonal influence on simulated regional scale concentrations. The influence of global scale background concentrations on regional scale air quality simulations is the primary focus of the next phase of AQMEII that will contribute to the activities of TF-HTAP. EPA is an active participant in the ongoing AQMEII Phase 3 effort.

Global assessment of precipitation chemistry and deposition

The atmospheric deposition of nitrogen, sulfur, and other chemical species to underlying surfaces is an important exposure pathway that can contribute or lead to the degradation of air, land, and water quality as well as reductions in the benefits humans may derive from ecosystems. Understanding the processes and outcomes associated with atmospheric deposition is needed to characterize progress toward meeting targeted reductions in deposition in the United States and Canada.

Scientists at the EPA actively participate in the NADP’s Total Deposition Science Committee (TDEP). The mission of TDEP is to improve estimates of atmospheric deposition by advancing the science of measuring and modeling atmospheric wet, dry, and total deposition of species such as sulfur, nitrogen, and mercury. TDEP provides a forum for the exchange of information on current and emerging issues within a broad multi-organization context including atmospheric scientists, ecosystem scientists, resource managers, and policy makers. One of the goals of the NADP's TDEP is to provide estimates of total sulfur and nitrogen deposition for use in critical loads and other assessments, where loading results in the acidification and eutrophication of ecosystems.

Gridded total deposition values provided by TDEP were developed using a hybrid approach that combines measured air concentration and wet deposition data with modeled unmeasured air concentration estimates and deposition velocities. Wet deposition values are obtained from combining the National Trends Network (NTN) measured values of precipitation chemistry with precipitation estimates from the Parameter-elevation Regression on Independent Slopes Model (PRISM). Dry deposition values are estimated by combining air concentration data from the Clean Air Status and Trends Network (CASTNET) and modeled deposition velocities. Modeled data were obtained from the Community Multiscale Air Quality model. Details of the methodology for developing the data set, as well as comparisons of these data to other deposition estimates, are provided in Schwede and Lear (2014). Total sulfur and nitrogen deposition data and maps are available for 2000 through 2015 on the NADP website.

EPA has been coordinating with ECCC to apply the same deposition approach of fusing measurement and modeling data with the goal of producing mutually-agreed-upon maps of total atmospheric deposition across North America. The Atmospheric Deposition Analysis Generated by Optimal Interpolation from Observations (ADAGIO) system being developed by ECCC will produce annual wet, dry, and total deposition maps for sulfur and nitrogen. The CAPMoN and NAPS network are providing observational data for air and precipitation concentrations in addition to the data from NTN and CASTNET. The Global Environmental Multi-scale – Modeling Air Quality and Chemistry model is being used to provide the modeled estimates. It is anticipated that the first results from ADAGIO for 2010 total deposition of nitrogen and sulfur will be released shortly.

Cooperation on mobile transportation sources

There is a long history of collaboration between ECCC and the EPA to reduce transportation emissions, largely fostered by the framework of the Agreement. A work plan has been developed that supports this ongoing collaboration. EPA and ECCC continue to work closely to align emission standards and coordinate their implementation. For example, EPA and ECCC share information and closely coordinate vehicle and engine compliance verification testing programs between our laboratories in Ann Arbor, Michigan and Ottawa, Canada. EPA and ECCC also coordinate research and testing projects to inform the development of
regulations. This collaboration minimizes testing overlap and improves the breadth of compliance monitoring, resulting in program efficiencies in both organizations. EPA and ECCC meet regularly to review progress on their coordination efforts and to discuss any opportunities or obstacles that should be addressed.

Cooperation on oil and gas sector emissions

In November 2015, a work plan between the EPA and ECCC was approved under the Agreement to support collaboration on oil and gas sector emissions. The oil and gas work plan has facilitated ongoing technical discussions between the two countries on a range of oil and gas issues, including developing equipment standards, addressing regulatory requirements and emissions associated with venting and flaring, designing leak detection and repair programs, fence-line monitoring at refineries, and the sharing of information through WebEx discussions on our respective greenhouse gas inventory and reporting programs. The work plan also served as the foundation for developing joint commitments to reduce methane emissions from the oil and gas sector. The Canada–United States cooperation has also extended to a work exchange with an EPA representative participating in an Embassy Science Fellowship Program in collaboration with ECCC in fall 2016.

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