Introduction

How to Use this Report

Use the visualizations of our emissions inventory below to explore the sources of ozone precursor emissions in the summertime within the Northern Wasatch Front Nonattainment Area (NWF NAA). Data presented in this interactive tool represent the summertime Northern Wasatch Front emissions inventory at the time of export. Inventories displayed here are for public consumption and may not necessarily reflect inventories submitted in the final SIP or used in the photochemical model.

  1. Use your mouse to hover over data points to learn more about the Source Classification Code (SCC) and the amount of pollutant coming from that emissions source in tons per day (TPD).
  2. To zoom in, click and drag over the area of the plot you’re interested in.
  3. Use the controls in the upper right corner of each plot to show the plot in full screen mode.
  4. Click on the blue buttons to navigate between sectors and charts.
  5. Double click on a sector in the legend to show data from only that sector. Double click again to show all data.
  6. Read “How to Read a Cumulative Distribution” tab above!

Background Information

This report summarizes emissions from the Northern Wasatch Front (NWF) Ozone Nonattainment Area (NAA), which includes Salt Lake, Davis, and parts of Weber and Tooele counties. This summertime emissions inventory will be used in several applications as part of the Utah Division of Air Quality’s ozone State Implementation Plan (SIP) for the Northern Wasatch Front. The important precursor pollutants that allow ozone to form in the atmosphere are the oxides of nitrogen (NOx) and volatile organic compounds (VOC). Both NOx and VOC are emitted from anthropogenic sources along the Wasatch Front, such as vehicles, paint, or lawnmowers. This report will help you explore the sources of NOx and VOC from many different emission source types.

Emissions inventories are collected and processed through the Sparse Matrix Operating Kernel Emissions Model (SMOKE). SMOKE modeling spatially allocates, temporalizes, and chemically speciates annual emissions estimations from the emissions inventories. Emissions inventories contain annual estimations of the amount of pollutant emitted from a given emission source, typically represented in tons of that pollutant per year. SMOKE takes that annual emission rate and some other inputs to determine 1) where the emissions are coming from geographically, 2) when those emissions are emitted throughout the year, month, and week, and 3) what chemical species are included in the emission of pollutant. From SMOKE, air quality scientists get emissions data in tons of pollutant per day for a given emissions source.

Emissions sources are identified by a Source Classification Code (SCC). Each SCC represents a unique source category-specific process or function that emits air pollutants.

Emissions are temporalized and reported in tons per day from July 12th, 2017, a representative summertime weekday in the modeling episode.

SCC’s and their emissions are classified into broader source sectors. Sectors relevant to the Northern Wasatch Front Ozone State Implementation Plan include: nonpoint, point, other point, onroad mobile, nonroad mobile, airports, rail, solvents, residential wood combustion, and livestock.

  • Airports: Emissions from all aircraft and ground support equipment. These are treated as point sources located at a fixed, stationary location.
  • Point: Any non-airport point sources, including large industrial facilities and Electric generating units, or EGU’s. For the NWF NAA, point sources only include sources with annual emission greater than 50 tons per year of NOx or VOC. These point sources are located at a fixed, stationary location.
  • Other Point: Any non-airport point sources, including smaller industrial facilities. For the NWF NAA, “nonpoint-point” sources only include sources with annual emission less than 50 tons per year of NOx or VOC. These point sources are located at a fixed, stationary location.
  • Nonpoint: Nonpoint sources include emissions that individually are too small in magnitude to report as point sources. Examples include residential heating, residential charcoal grilling.
  • Rail: Emissions from railroads, for example, FrontRunner trains. Emissions from rail yards are included in the Point sector.
  • Solvents: This sector includes emissions from asphalt paving, and commercial and consumer solvent use (e.g. hairspray, household cleaning products).
  • Livestock: Emissions from the agricultural production of livestock, including emissions from manure.
  • Wood Combustion: Emissions from the residential wood combustion. In the summertime, these emissions are from firepits, chimineas, etc.
  • Onroad: Includes emissions from onroad vehicles that use gasoline, diesel, and other fuels. Onroad vehicles include light-duty and heavy-duty vehicles operating on roads, highway ramps, and during idling.
  • Nonroad: Includes emissions from off-road mobile sources that use gasoline, diesel, and other fuels. These source types include construction equipment, and lawn and garden equipment.

How to Read a Cumulative Distribution

A cumulative distribution helps us easily understand emissions sources that contribute most significantly to the total pollution. All source classification codes (SCC’s) are sorted from the greatest pollutant emission rate (tons per day) to the least emission rate. The SCC with the largest pollution rate is assigned rank 1. The SCC with the smallest pollution rate is given the highest rank. On the cumulative distribution plot, this rank is the “cumulative rank” and is displayed on the x-axis.