A Case Study of Sulfur Dioxide in Muscatine, Iowa and the Ability for AERMOD to Predict NAAQS Violations Presented by Charlene Becka Air Quality Engineer
NAAQS SO 2 Standards Respiratory irritant in sensitive individuals Standard changed to hourly limit of 75 ppb (approximately 196 µg/m 3 ) in 2010 2
Muscatine, Iowa Area of nonattainment 2010: 14 violations (starting 8-27) 2011: 37 violations 2012: 36 violations 2013: 67 violations 2014: 46 violations (through 9-5) Monitor Monsanto Grain Processing Corp & Muscatine Power and Water Mid American Energy 3
Many emission points for each facility Several facilities located near the receptor (monitor) 4
Can We Predict A Violation Before It Happens? Historical Analysis Hourly SO 2 monitored concentrations obtained from IDNR for 2007 AERMOD input file with allowable emission rates prepared by IDNR for Muscatine obtained AERMOD run using 1 year (2007) of preprocessed (IDNR) meteorological data based on surface and upper air information Meteorological conditions for highest monitored and modeled concentrations examined 5
Concentration, ppb 802 602 Modeled Measured Hourly Modeled and Monitored Concentrations for 2007 402 202 2 1/1 1/31 3/2 4/1 5/1 5/31 6/30 7/30 8/29 9/28 10/28 11/27 12/27 Date 6
Concentration, ppb 142 122 102 82 62 42 24-Hour Averaged Modeled and Monitored Concentrations for 2007 Modeled Measured 22 2 1/1 1/31 3/2 4/1 5/1 5/31 6/30 7/30 8/29 9/28 10/28 11/27 12/27 Date 7
Emissions, lb/d Inaccurate Model Concentrations? It might be due to inaccurate emission rates! 100000 90000 80000 70000 60000 50000 40000 30000 20000 10000 0 Grain Processing Corporation Daily Emissions in 2012 8
Can We Predict A Violation Before It Happens? Forecast Model Analysis Weather forecast models used as meteorological input for AERMOD 9
Can We Predict Violations? Weather Research Forecast Model (WRF) High resolution, local model Hourly concentrations Retro analysis Bounded with observational nudging 10
Can We Predict Violations? North American Mesoscale Forecast System (NAM) Low resolution, regional model Unbound Concentrations every 6 hours 11
Emissions, lb/d Emission Variability By Day, March 2012 100000 Emission inventories and CEMS data obtained These were used as daily emission rates in AERMOD 90000 80000 70000 60000 50000 40000 30000 20000 GPC Musc Power and Water Mid Am Energy Monsanto 10000 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 Day of March 12
WRF Processing Need to convert WRF forecast into files AERMOD can read Surface Upper air Mesoscale Model Interface Program (MMIF) EPA beta program 13
Concentration, ug/m3 WRF vs Monitored Concentrations: Highest Values 10000 Highest actual Highest WRF 1000 100 10 1 0.1 1 6 11 16 21 26 31 Day of March 14
NAM Processing NAM files unreadable by MMIF Downloaded NAM files (compressed grib2 format) Used Linux program that stripped the variables out of the NAM file, placed variables into WRF file Processed the new WRF files (filled with NAM variables) with MMIF 15
Concentration, ug/m3 NAM vs. Monitored Concentrations: Highest Values 10000 1000 Monitored conc Day 2 forecast Day 3 forecast 100 10 1 0.1 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 Day of March 16
Overall Results Violations Correct violations False positives Unreported violations Correct nonviolations Number Percent Number Percent Number Percent Number Percent Number Percent Monitored 9 22 WRF 15 66.7% 8 88.9% 7 31.8% 1 11.1% 15 68.2% NAM Day 2 8-11.1% 2 22.2% 6 27.3% 7 77.8% 16 72.7% NAM Day 3 6-33.3% 3 33.3% 3 13.6% 6 66.7% 19 86.4% WRF overpredicted, but correctly predicted more days when they occurred NAM predicted number of days more accurately, but timing of violations was inaccurate 17
Final Thoughts More research is needed using the latest technology and tools to accurately predict a violation before it occurs. Using prognostic meteorological data such as WRF or NAM could possibly be used in a regulatory setting as an alternative to the standard modeling practice. 18
Questions? Charlene Becka Wenck Associates, Inc. cbecka@wenck.com 19
A Case Study of Sulfur Dioxide in Muscatine, Iowa and the Ability for AERMOD to Predict NAAQS Violations Presented by Charlene Becka Air Quality Engineer