Emission standards control strategy

Without doubt, the top-priority application of air quality models is the determination of emission controls needed to achieve ambient air quality standards. With the re-examination of transportation control strategies and with the pressures of fuel substitutions, refinements well bqrond the traditional proportional models are imperative. Where validated diffusion models are available, they should be used to recalculate the emission requirements that came from initial hasty efforts to implement the Qean Air Act Amendments of 1970. This is the greatest national service that could be performed by the air quality modelers at present. Before this can be achieved, however, the institutional apparatus must provide the impetus and resources called for in a recent National Academy of Sciences report to the U.S. Senate. 

A major limitation of receptor models is their inability to distinguish between specific sources within a source type. Resuspended road dust may be a major cause of standard violations, but until the offending roadways can be pinpointed, a control strategy cannot be implemented. A major limitation of source models is the necessity to estimate emission rates from the many, diverse producers of suspended particulate matter. The receptor model quantifies the source type contributions. Only the major contributors need to be evaluated for the source model, so that resources which might have been used to inventory... 

Without the benefit of the data base improvement programs, 27 million dollars in Industrial controls would likely have been the key element in a new control strategy yet would have only provided one-third of the reduction required to meet standards. Instead, a more effective mix of point and area source controls will likely be adopted and, at considerably less cost to (and with considerably more effectiveness for) the community. Once the capability is developed, CMB estimates of source Impacts can be used to track the progress of the strategy on a source-class basis using actual air samples, (in addition to emission estimates) to measure the effectiveness of the controls. Oregon s Source Apportionment Program and the Future... 

It is interesting that over the same period in many other regions of the United States and in Europe and Japan, ozone levels did not appear to change as dramatically (National Research Council, 1991 Lindsay et al., 1989 Rao et al., 1992, 1994, 1995, 1996 Zurbenko et al., 1995 Fiore et al., 1998 Oltmans et al., 1998). The major difference in control strategies in California compared to the U.S. federal approach has been an emphasis on both NO, and VOC control, rather than primarily on VOC as has been the case at the federal level. For example, Table 16.3 shows the more stringent control of both NO, and VOC from motor vehicles in California beginning in the mid-1970s. Since 1980, however, VOC emission standards in California have been comparable to the federal standards while the allowed NO, emissions have been smaller by a factor of two or more. 

M. Deacon, R.W. Horrocks, C.J. Brace, N.D. Vaughan, C.R. Burrows "Impact of alternative controller strategies on emissions from a diesel CVT powertrain - preliminary results." IMechE Seminar on "Application of Powertrain and Fuel Technologies to meet Emission Standards." 24.-26. June 1996, London. 

The Clean Air Act requires each state to adopt a plan, a State Implementation Plan (SIP), which provides for the implementation, maintenance, and enforcement of the NAAQS. It is, of course, emission reductions that will abate air pollution. Thus the states plans must contain legally enforceable emission limitations, schedules, and timetables for compliance with such limitations. The control strategy must consist of a combination of measures designed to achieve the total reduction of emissions necessary for the attainment of the air quality standards. The control strategy may include, for example, such measures as emission limitations, emission charges or taxes, closing or relocation of commercial or industrial facilities, periodic inspection and testing of motor vehicle... 

As emission standards for automobiles become tighter, improved closed-loop TWC control strategies become even more critical. The development of advanced TWC control strategies includes custom model-based methods (Fiengo et al., 2005 Balenovic et al., 2006 Guzzella, 2008). 

In 1970, new efforts were underway to solve Portland s suspended particulate problem. Early efforts relied on available emission factors and industrial source testing, as a basis for the emission Inventory. The inventory was then used, with a proportional rollback model, as a basis for the new strategy. New industrial controls were Installed which resulted in a 60,000 tons per year region-wide reduction in industrial emissions. Although progress toward cleaner air was made, air quality standard violations caused by then unknown sources continued and modeling efforts failed to account for over one-half of the particulate mass. 

Although the control of fugative emissions appears to be the most cost effective approach to particulate standard attainment, few benefits in regional visibility Improvement and public health would be expected from such a strategy. 

How effective are proposed control or management strategies This question could pertain to the confidence with which a standard will be met. For example, Hanna et al. (2001) assess the uncertainty associated with estimates of predicted ambient ozone levels subject to a particular emission scenario, and Abdel-Aziz Frey (2004) evaluate the probability of non-compliance with United States National Ambient Air Quality Standards for ozone based upon uncertainty in emission inventories that are propagated through an air quality model. A probability distribution of estimated exposures can be compared with a point estimate of an exposure benchmark in order to determine the probability that the benchmark will be exceeded and, if so, by how much. 

The American 1970 Clean Air Act defined ambient air quality standards (NAAQS) in the United States for atmospheric ozone, NO, lead, carbon monoxide, sulfur oxides, and PM-10 (particulate matter less than 10 p.m). The strategy to reduce levels of lead, NOx, PM-10, and to some extent carbon monoxide was to control emissions from automobiles that included the phasing-out of leaded fuel. As previously noted, ozone is a product of the photochemical reaction of volatile organic compounds with NOx (photochemical smog), so the balance between organic compounds and NOx pollutants is important in meeting target ozone levels (e.g., 0.12 ppm). Emissions from stationary sources is an important factor, and limits have been set for them. Because of low pressure drop requirements, coated monolithic catalysts... 

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