Source Apportionment
Source apportionment for regional haze planning was conducted using various modeling techniques. The SOx/NOx Tracer and Organic Aerosol Tracer were performed using a regional air quality model. The Weighted Emissions Potential analysis included the synthesis of emissions data and meteorological back trajectories. The PMF Receptor Modeling and Causes of Dust analysis were complex statistical exercises involving IMPROVE monitoring data. Not all source apportionment techniques were applied to all pollutants.
Source Apportionment Tools
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The WRAP Modeling Forum’s Regional Modeling Center (RMC) performed a source apportionment analysis using the CAMx air quality model and the PM Source Apportionment Technology (PSAT) tool. Results from this analysis provide information regarding source region and source category contributions to particulate sulfate and nitrate at Class I areas. Tracer results for SOx and NOx are selectable by source category and source region, for the 2000-04 Baseline and 2018 Base Case modeling simulations.
Navigation Note: 1) Click the link above, 2) Select a site(s), 3) Click the "Emissions and Source Apportionment" button below the map, and 4) Select either the "Sulfate/SOx Tracer" or the "Nitrate/NOx Tracer" link.
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The Weighted Emissions Potential (WEP) analysis was developed as a screening tool for states to decide which source regions have the potential to contribute to haze formation at Class I areas, based on annual emissions inventories, baseline period wind patterns, and source to Class I area distances.
Navigation Note: 1) Click the link above, 2) Select a site(s), 3) Click the "Emissions and Source Apportionment" button below the map, and 4) Select one of the "Weighted Emissions Potential" links.
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The regional gridded model tracer results for organic aerosols identifies organic carbon source type contributions as: 1) primary organics (anthropogenic and biogenic); 2) anthropogenic secondary organics; and 3) biogenic secondary organics. These results do not include emissions source region or detailed source category information.
Navigation Note: 1) Click the link above, 2) Select a site(s), 3) Click the "Emissions and Source Apportionment" button below the map, and 4) Select the "Organic Aerosol Tracer" link.
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This receptor modeling technique, called Positive Matrix
Factorization, analyzes the statistical relationships among
monitored IMPROVE chemical species over time at Class I areas,
and provides some additional assessment of the contribution to
haze of source groups identified in the analysis.
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Sources of fugitive dust can vary greatly in spatial scale, time, location, causes of emission, and are not well characterized by emissions inventory and regional dispersion modeling techniques used for other haze-causing pollutants. The study utilized several alternative methods to specifically identify the primary causes of dust measured at WRAP region Class I areas. 2001-2003 data from IMPROVE (and some protocol) monitoring sites in the WRAP region for each worst dust visibility day was associated with one of these events:
- Transcontinental transport of large scale events from Asia
- Windblown dust events
- Transport of windblown dust from sources upwind (i.e. not from immediate vicinity of site)
- Undetermined Events
Further specification if windblown and upwind transport events appear to be regional in nature based on scale of meteorological phenomenon causing dust and number of sites affected. Dust source apportionment results by Class I area monitoring site can be obtained from the Dust Episode Analysis tool .
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Source Apportionment Methods
PSAT Analysis:This document summarizes the PM Source Apportionment Technology (PSAT) analysis performed to trace SOx and NOx emissions leading to particulate species at WRAP region IMPROVE monitoring sites. This analysis was performed by the Regional Modeling Center.
Organic Aerosol Tracer:This document summarizes the method used by the Regional Modeling Center to model the contribution of primary and secondary, natural and anthropogenic organic carbon at WRAP region IMPROVE monitoring sites. (Document under development)
WEP Analysis:This document summarizes the Weighted Emissions Potential (WEP) analysis performed by the TSS team. The WEP analysis identifies the potential for emissions source regions to impact haze constituents at WRAP region IMPROVE monitoring sites.
Key to Monitoring-Modeling-Emissions Mapping:This table summarizes the relationship among real-world visibility-related parameters and parameters defined by the IMPROVE program, the CMAQ and CAMx models, and WRAP emissions inventories. Specific topical designations and direct comparisons are presented. (
HTML or
Excel)