Journal of the Air & Waste Management Association For Peer Review Only Receptor model source attributions for Utah’s Salt Lake City airshed and the impacts of wintertime secondary ammonium nitrate and ammonium chloride aerosol Journal: Journal of the Air & Waste Management Association Manuscript ID: Draft Manuscript Type: Technical Paper Date Submitted by the Author: n/a Complete List of Authors: Kelly, Kerry; University of Utah, ICSE Kotchenruther, Robert; US Environmental Protection Agency Region 10, Office of Environmental Assessment Kuprov, Roman; Utah Division of Air Quality, Silcox, Geoffrey; University of Utah, Chemical Engineering Keywords: Particulate Matter, Source apportionment, PM2.5 Abstract: Source attribution, PM2.5, cold pool, nonattainment, inversion http://mc.manuscriptcentral.com/jawma Email: [email protected] Page 1 of 51 Journal of the Air & Waste Management Association 1 2 3 IMPLICATIONS 4 5 6 The study suggests that secondary ammonium chloride aerosol can be a significant source of 7 8 wintertime PM 2.5 in an ammonia-rich environment, like the Wasatch Front, if sufficient sources 9 10 of atmospheric chlorine exist. During winter-time, cold-air-pool events, the source attribution 11 results generally agree with the county emission inventories with the exception of wood smoke 12 13 and cooking sources. In Salt Lake City, the estimated contributions from wood smoke and 14 For Peer Review Only 15 cooking are nearly double those of the corresponding inventory, suggesting that they are nearly 16 17 as important as gasoline emissions at this monitoring station. 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 1 http://mc.manuscriptcentral.com/jawma Email: [email protected] Journal of the Air & Waste Management Association Page 2 of 51 1 2 3 Title: Receptor model source attributions for Utah’s Salt Lake City airshed and the 4 5 impacts of wintertime secondary ammonium nitrate and ammonium chloride aerosol 6 7 a b c a 8 Kerry E. Kelly , Robert Kotchenruther , Roman Kuprov , Geoffrey D. Silcox 9 10 a Dept. of Chemical Engineering, University of Utah, 380 INSCC, Salt Lake City, UT, 84112, 11 12 USA, [email protected]; (801) 587 7601 (tel); (801) 585-9291 (fax) 13 Corresponding author 14 b U.S. EPA Region-10For Office Peer of Environmental Review Assessment, 1200 Only Sixth Avenue, Suite 900, OEA- 15 16 095,Seattle, WA, 98101-3140, USA 17 [email protected]; (206) 553-6218 (tel) 18 c Utah Division of Air Quality, 195 North 1950 West, Salt Lake City, UT, 84116, USA 19 20 [email protected]; 801-536-4254 (tel); 801-536-0601 (fax) 21 d Dept. of Chemical Engineering, University of Utah, 3290 MEB, Salt Lake City, UT, 84112, 22 USA, [email protected]; (801) 581-8820 (tel); (801) 585-9291 (fax) 23 24 25 ABSTRACT 26 27 28 Communities along Utah’s Wasatch Front are currently developing strategies to reduce daily 29 average PM 2.5 levels to below National Ambient Air Quality Standards during wintertime, 30 31 persistent, multi-day stable atmospheric conditions or cold-air pools. Speciated PM 2.5 data from 32 33 the Wasatch Front airshed indicates that wintertime exceedances of the PM 2.5 standard are 34 35 mainly driven by high levels of ammonium nitrate. Stable wintertime conditions foster the 36 formation of ammonium nitrate aerosol, if there are sufficient sources of NOx, ammonia, and 37 38 oxidative capacity. However, this work demonstrates that secondary ammonium chloride aerosol 39 40 can also be a significant source of secondary wintertime PM 2.5 if sufficient sources of 41 42 atmospheric chlorine exist. Two factor analysis techniques, positive matrix factorization (PMF) 43 44 and Unmix, were used to identify contributors to PM2.5 at three monitoring stations along Utah’s 45 Wasatch Front: Bountiful, Lindon, and Salt Lake City. The monitoring data included chemically 46 47 speciated PM 2.5 data for 227, 227, and 429 days at each location, respectively, during the period 48 49 from May 2007 through May 2011. PMF identified 10 – 12 factors, and Unmix identified 4 - 5 50 51 factors for each of the locations. The wintertime PMF and Unmix results showed large 52 contributions from secondary PM when PM concentrations exceeded 20 µg/m 3. PMF 53 2.5 2.5 54 identified both ammonium nitrate and ammonium chloride aerosol as significant secondary 55 56 contributors to PM 2.5 (10%-15% of total PM 2.5 from ammonium chloride) during wintertime 57 58 pollution episodes. Subsequent ion balance analysis of the monitoring data confirmed the 59 60 1 http://mc.manuscriptcentral.com/jawma Email: [email protected] Page 3 of 51 Journal of the Air & Waste Management Association 1 2 3 presence of significant ammonium chloride aerosol on these highly polluted days at all three 4 5 monitoring sites. The primary PM 2.5 portion of the source attribution results were further 6 7 compared to county-level emissions inventories and showed generally good agreement for Salt 8 9 Lake City and Lindon during wintertime except for wood smoke and fugitive dust, which have 10 11 higher contributions in the receptor modeling results than in the emissions inventories. 12 13 IMPLICATIONS 14 For Peer Review Only 15 16 The study suggests that secondary ammonium chloride aerosol can be a significant source of 17 18 wintertime PM 2.5 in an ammonia-rich environment, like the Wasatch Front, if sufficient sources 19 of atmospheric chlorine exist. During winter-time, cold-air-pool events, the source attribution 20 21 results generally agree with the county emission inventories with the exception of wood smoke 22 23 and cooking sources. In Salt Lake City, the estimated contributions from wood smoke and 24 25 cooking are nearly double those of the corresponding inventory, suggesting that they are nearly 26 27 as important as gasoline emissions at this monitoring station. 28 29 30 INTRODUCTION 31 32 Exposure to fine particulate matter (PM 2.5 , particles with an aerodynamic diameter <2.5 µm) has 33 34 been linked to adverse human health effects, including increases in cardiovascular and 35 36 pulmonary disease (Baliff et al., 2000; Nicolai et al., 2003), and morbidity and mortality 37 (Dockery et al., 1993; Pope et al., 1991). PM also contributes to impaired visibility (Watson 38 2.5 39 2002) and changes in the global radiative balance (Chung and Seinfeld, 2002). In 2006, EPA 40 3 41 issued an updated 24-hour standard for PM 2.5 of 35 µg/m , and as a result in 2009 they declared 42 43 three regions in northern Utah along the Wasatch Front as nonattainment areas for 24-hr average 44 PM . The state of Utah is currently developing a plan to bring the PM concentrations to 45 2.5 2.5 46 attainment levels. 47 48 49 50 The Wasatch Front typically experiences elevated levels of PM 2.5 during wintertime, when high- 51 52 pressure weather systems and a high solar zenith angle lead to cold-air pools that periodically 53 trap aerosols in mountain valleys. These elevated PM 2.5 levels cause adverse health effects 54 55 locally. For example, the State of Utah found that the odds of an emergency department visit in 56 th th 57 Salt Lake County, with a primary diagnosis of asthma, are 42% greater during the 5 – 7 days 58 59 60 2 http://mc.manuscriptcentral.com/jawma Email: [email protected] Journal of the Air & Waste Management Association Page 4 of 51 1 2 3 of prolonged inversions than for non-inversion days (UDAQ, 2010). During a particularly 4 3 5 extreme cold-air pool event in 2004 PM 2.5 concentrations exceeded 100 µg/m (Malek et al., 6 7 2006), while more recent maximum concentrations have been in the range of 50 – 70 µg/m 3. 8 9 10 11 Several previous studies have examined the sources of fine particulate matter along the Wasatch 12 Front; however, compared to this work these studies used data that spanned a brief time period, 13 14 on the order ofFor weeks.. Hansen Peer et al. (2010) Review collected speciated hourlyOnly PM 2.5 data at the Utah 15 16 Division of Air Quality (UDAQ) Lindon air monitoring station for 10 days during the winter of 17 18 2007 and performed a source apportionment study using the Positive Matrix Factorization (PMF) 19 model. Their model results identified the following four primary sources: mobile diesel, mobile 20 21 gasoline, wood smoke, road dust and the following secondary sources: sulfate, nitrate, organic 22 23 matter, and aged wood smoke. Grover et al. (2006) performed an intensive air monitoring 24 25 campaign in August 2002 at the UDAQ Lindon air monitoring station and complementary source 26 apportionment using the Unmix model. From this small sample set, they found three main 27 28 contributors to PM 2.5 : gasoline emissions, diesel emissions, and secondary aerosols. Their 29 30 analysis did not include inorganic species, so it is not surprising that they did not identify sources 31 32 of crustal material. The limited duration of these previous studies makes it difficult to draw 33 34 general conclusions about the sources of fine particulate matter along the Wasatch Front. 35 36 37 This study investigates the sources of PM 2.5 impacting three monitoring sites along the Wasatch 38 39 Front using ambient data collected from 2007 to 2011. Source apportionment is performed using 40 41 two receptor models, PMF and Unmix, and model results are compared to each other as well as 42 to emissions inventories.