Global Sources of Local Pollution An Assessment of Long-Range Transport of Key Air Pollutants to and from the United States (2010) / Chapter Skim
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6 Crosscutting Issues and Synthesis
6 Crosscutting Issues and Synthesis
Pages 125-150
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From page 125... ...
CROSSCUTTING ISSUES New Pollutant Fingerprinting Techniques The high degree of complexity involved in identifying and quantifying long-range pollution transport, particularly in identifying and characterizing contributions from individual pollution sources, will require new developments in analytical and observational techniques. The difficulty in resolving sources is a limiting factor in determining the contributions of long-range transport for almost all pollutants.
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From page 126... ...
This is a particularly powerful application for long-range transport studies because it is one of few measurements that provides information about the chemical processes that have occurred during transit as well as their bulk properties at arrival. For example, applications of isotopic techniques provide a means by which ship emissions can be recognized in regions with multiple pollution sources that cannot be separated by traditional concentration measurements (Dominguez et al., 2008)
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, the use of stable isotope ratio measurements could play an increasingly significant role in all aspects of understanding international pollutant transport. Molecular Chirality Measurements A recently proposed technique involves the study of enantiomeric signatures of chiral organochlorine pesticides (OCPs)
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, wildfires (Mühle et al., 2007) , gasoline and diesel emissions, and ship emissions (Toner et al., 2008; Ault et al., 2009)
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Both nested emission inventories and nested models, with higher resolution in highconcentration areas, are needed to more accurately represent initial plume processing and transport. Emission projections Understanding the effects of a changing climate and an evolving economy on future natural or anthropogenic emissions requires mechanistic representations of the factors that affect those emissions.
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. The use of satellite data for selected tropospheric pollutants, including CO and NO2 and PM, can also be used to identify emission hot spots and evaluate regional emission inventories.
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HTAP-TF (2007) provides a comprehensive summary of emission inventories that represent energy and economy.
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(ii) Natural environment Contributions from the natural environment are observed in both episodic transport and in regional and transported background concentrations.
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Improvements in present-day emission inventories will be possible only by representing the factors that modulate those emis sions. These factors are as diverse as the response of the natural environment to changing climate and shifts in the mix of technol ogy caused by tightened emission standards.
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Enhance the understanding of legacy emissions of Hg and POPs by modeling environmental flows and reservoirs, in conjunction with historical emission inventories that cover sev eral decades of human activity. Meteorological Processes Chemical transport models as well as trajectory calculations and particle dispersion models rely on meteorological conditions to simulate pollutant transport.
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In addition to needing meteorological data, the models meant for chemistry transport studies need to be run at high resolution in an attempt to incorporate the myriad of circulations (see Appendix B) that affect long-range pollutant transport.
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Convective transport, whether dry or associated with thunderstorms, is a prime exam ple that directly affects pollutant transport. Many convective parameterization schemes have been designed for grid resolutions greater than 10 km.
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To be most effective meteorologists and atmospheric chemists, including both modelers and measurement specialists, should collaborate on efforts to obtain the phenomenological insights and data required to develop the better measurement techniques and improved numerical models that will enable us to adequately quantify the role of distant sources on local air quality. International Pollutant Transport from Maritime Shipping and Aviation Sources Pollutant emissions from international ship and air transport are of direct interest to those studying long-range atmospheric pollutant transport because they represent a unique class of international pollutant transport, which is growing rapidly and may in some cases mimic long-range atmospheric transport.
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This work demonstrates that not only are ship emissions significant sources of both PM and PAHs but also may be distinct from other transportation emissions. Aircraft Emissions As discussed in IPCC reports global aviation transport involves direct emissions of fine particles into the upper troposphere
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Finding. Emissions from ocean shipping and passenger and cargo aircraft are a source of long-range pollution transport that can complicate the detection and characterization of long-range atmo spheric pollutant transport from historical land-based sources.
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Improving our capability to assess the impacts of long-range transport of pollution on the effectiveness of national control strategies requires better quantification of the global distribution of pollutants and their trends, and an increased ability to perform source attribution analyses at hemispheric and global scales. The importance and required attributes of a global air quality observational strategy were articulated in an earlier NRC report Global Air Quality: An Imperatie for Long-Term Obserational Strategies (NRC, 2001)
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Reducing these uncertainties requires combining model and measurement techniques in an integrated analysis of data from an enhanced observing system. Figure 6.1 depicts the major components of the needed system, including: emission inventories; chemical transport modeling; long term ground based monitoring; satellites; and intensive field studies.
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source signals, which can be exploited in fingerprint and observation-based source attribution analyses; • closer integration of ground-based observations and models will lead to reduced uncertainties as a result of more critical evaluation of model predictions, better calibration and evaluation of observation- and modelbased attributions, and improved measurement strategies; • closer integration of field experiments with elements focused on source attribution will lead to improved understanding of processes affecting the source-receptor relationships, better techniques to follow targeted air masses (e.g., from specific source sectors or regions) over long
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, in an enhanced lidar network, in new instrument platforms such as supersites for measuring a comprehensive suite of chemical species in remote locations, and in unmanned aerial vehicles for long-duration sampling of the atmosphere over a wide range of altitudes. This network would provide a wealth of information needed for chemical data assimilation and improved prediction of transport and chemical processes, which are needed to reduce uncertainties in source attribution estimates.
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Currently satellite observations can provide long-term global records of a limited number of key atmospheric trace gas and aerosol parameters; observations of long-range and intercontinental transport of pollution from continental source regions; column or partial column retrievals with very limited sensitivity to the lowermost troposphere; and top-down emissions estimates on fairly coarse scales. To improve their use in long-range transport studies the following are needed: • improvements in resolution -- spatial coverage to facilitate the tracking of individual plume events.
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have made substantial efforts to establish a global network of observational sites including sites in undersampled, remote regions around the world, supported by data centers and quality control programs to enhance integration of air quality measurements from different national and regional networks. The source attribution analysis described here requires substantial international cooperation and open exchange of data from national emission inventories and air quality monitoring networks.
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Thus there are additional activities needed for source attribution beyond those for compliance and detection of long-term trends in ambient concentrations. Finding: Source attribution analysis, which builds upon a global observing system with integration among other key elements, requires substantial international cooperation and an open exchange by countries of data from national emission inventories and air quality monitoring networks.
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Under present global socioeconomic scenarios nondomestic influences on air quality are expected to increase in the future and will likely be an issue of increasing concern. Enhancing observations, chemical transport models, trend analyses, studies of reaction mechanisms for relevant species, and emission inventories and projections will all be of critical importance to better quantify such effects.
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Some pollutant sources, such as ships and aircraft, that are inherently international in nature require more sophisticated and extensive observations and analysis. Emission inventories may be improved in some cases by development of additional satellite observations, assuming continued development and launch of advanced sensors and suitable platforms designed to increase the vertical and horizontal resolution, increased species coverage, and higher sensitivities for important tropospheric pollutants.
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The United States, as both a source and receptor of this long-range pollution, has a responsibility to remain actively engaged in addressing this issue. It is clear that local pollution can be affected by global sources, although in most cases air quality violations are driven by local emissions.
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