Source impact

The initial direction of transport of pollutants from their source is determined by the wind direction at the source. Air pollutant concentrations from point sources are probably more sensitive to wind direction than any other parameter. If the wind is blowing directly toward a receptor (a location receiving transported pollutants), a shift in direction of as little as 5° (the approximate accuracy of a wind direction measurement) causes concentrations at the receptor to drop about 10% under unstable conditions, about 50% under neutral conditions, and about 90% under stable conditions. The direction of plume transport is very important in source impact assessment where there are sensitive receptors or two or more sources and in trying to assess the performance of a model through comparison of measured air quality with model estimates. 

All of the above particulate investigations were based on mini-radiocarbon measurement techniques, with sample masses typically in the range of 5-10 mg-carbon. This constituted a major advantage, because it was practicable to select special samples (given region, source impact, sediment depth) and to further subject such samples to physical (size) or chemical separation before 14C measurement. This type of "serial selectivity" provides maximum information content about the samples and in fact it is essential when information is sought for the sources or atmospheric distributions of pure chemical species, such as methane or elemental carbon. 

WA Air Qual. Program. 1998. Toxic air pollutants and acceptable source impact levels. Washington Air Quality Program, Department of Ecology. Wash Admin Code Section 173-460. 

The source of the raw materials can greatly influence hydrolytic reactions. This is exemplified by Gold and Campbell [54] where talc obtained from different sources impacts markedly on the overall stability of the aspirin tablet formulation. This is possibly attributable to the effect of different types and amounts of surface impurities, which are dissolved in the adsorbed moisture layer, where they subsequently react with the API. It could also influence the pH of the micro-environment. 

Cooper, J. A. Watson, J. G., Jr. "Review of Air Particulate Source Impact Assessment Methods", This Symposium. 

Urban aerosols are complicated systems composed of material from many different sources. Achieving cost-effective air particle reductions in airsheds not meeting national ambient air quality standards requires identification of major aerosol sources and quantitative determination of their contribution to particle concentrations. Quantitative source Impact assesment, however, requires either calculation of a source s impact from fundamental meteorological principles using source oriented dispersion models, or resolving source contributions with receptor models based on the measurement of characteristic chemical and physical aerosol features. Q)... 

Dispersion model source impact estimates, following comparison to the CMB results, were significantly improved after emission inventory deficiencies were corrected. Pinal modeling results then provided realistic source impact estimates which could be confidently used for strategy development. 

Presented as an overview of the State of Oregon s unique approach to particulate control strategy development, this review was prepared to provide those responsible for airshed management with new information on source impact assessment methods. (This material is available in the form of an audio-visual program suitable for presentation before public, regulatory or private Interest groups). 

Comparison of the PACS-CMB source impact estimates to the dispersion model-predicted source impacts ... 

Completion of emission inventory and modeling assumption improvements to match dispersion model source impacts to CMB results and... 

Industrial emissions collectively accounted for only 5% of the particulate mass, a result that was not surprising given that these sources were well controlled before field sampling began. Some industrial source Impacts, however, may not have been identifiable because of emissions that chemically resembled geologic sources. 

Step 2 required identification of source impacts by airshed modeling. Wind speed, direction, mixing height, and emission data bases designed to represent conditions on PACS sampling days were used to insure that the CMB impact estimates could be directly compared to model predictions for each sampllne site. 

The CMB-dlspersion model comparisons had Identified data base deficiencies that would not have been apparent had the model predictions been compared only to measured particulate mass. Correction of the emission inventory and model inadequacies was, however, critical to improving the model s source Impact predictions and to the strategy s success. 

Particulate Control Alternatives Model Predicted Source Impacts for 1987 (pg/m, 24 Hour Worst Case Meteorology)... 

Major changes in the Medford model s treatment of area source impacts were completed after early results consistently underpredicted road dust impacts measured by CMB. As a result, model performance improved dramatically. 

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... 

The development of new source apportionment methods have, for the first time, led to the development of regional particulate control strategies. Source impacts assigned using a chemical mass balance (CMB) model have been used in association with airshed dispersion models to identify emission inventory deficiencies and Improve modeling assumptions. 

Carter, W. P. L R. Atkinson, A. M. Winer, and J. N. Pitts, Jr., Evidence for Chamber-Dependent Radical Sources Impact on Kinetic Computer Models for Air Pollution, Int. J. Chem. Kinet., 13, 735-740(1981). 

Methods for Quantification of Source Impacts 2.1 Emission Measurements... 

An alternative to the above described approaches is the radiocarbon method that allows a distinction of contemporary carbon (from biogenic emissions and combustion of biomass) and carbon from combustion of fossil fuels in particulate carbonaceous matter [15, 41,42]. In contrast to fossil fuels where the 14C isotope is completely depleted, CM emitted from WB shows a contemporary radiocarbon level. Radiocarbon measurements are often combined with measurements of complementary source specific tracers (macro-tracer) for additional information of source impacts [14, 43, 44]. 

Eatough, D.J., Eatough, M., Lewis, L.J. et al. (1996) Apportionment of sulfur oxides at canyonlands during the winter of 1990 — II. fingerprints of emissions from point and regional sources impacting canyonlands. Atmospheric Environment, 30(2), 283-94. 

Washington Acceptable source impact levels at 10 6 risk (annual average) 2.5 g/m3 WA Dept, of Ecology 1998... 

Washington Acceptable source impact levels Annual average Chromium(VI) 24-hour average Chromium(ll), Cr Chromium(lll), Cr Chromium(metal) Lead chromate, Cr 8.3x105 pg/m3 1.7 pg/m3 1.7 pg/m3 1.7 pg/m3 4x102 pg/m3 WA Dept Ecology 1998... 

The reliable estimation of source impact on receptor conditions is difficult from theory because of undetermined uncertainties. Inference from comparison between emissions and measurements offers an alternative to calculations. Measurements in the East have yielded ambiguous source-receptor relationships. However, evidence suggests that recent changes in sulfate deposition in the West are linked with relatively large changes in SO emissions from non-... 

Diffusion Hybrid Receptor Model (Fay). This approach, beginning with the work of Fay and Rosenzweig (7), is perhaps the most interesting of all the hybrid models that have been proposed to date. Not only is it able to address the usual source apportionment problem of estimating source impacts (of SO2 and secondary sulfate) at a receptor site but it simultaneously generates estimates for the conversion and deposition rate constants and meteorological parameters that are influencing the pollutant transfer between source and receptor. Consequently, we choose to review this model in more detail than the others considered here. 

The second example is the Niagara Frontier AQCR (Buffalo, N.Y.). The highest annual average ambient SOj. concentration recorded at any receptor in this AQCR is 197 /xg/m. The ambient SOa concentration at this receptor could be reduced below the primary ambient air quality standard of 80 /xg/m by the control of one source only to a level of at least 95%. The importance of this single industrial combustion source can further be shown by the fact that, if all other sources impacting on this worst receptor had 100% control, this single combustion source would... 

The calculated values for SOa ambient air quality in the Niagara Frontier AQCR for the top 10 receptors ranged from 114 to 197 /xg/m . Table VIII provides the results of the analysis of source impacting those receptors. The application of selective controls in the Niagara Frontier AQCR would provide for reduction of ground level SOa- concentration to the national primary standard through application of 75% eflFective means to 17 of their 541 emitters or 27% of the emissions. 

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