EPA Precursor Gas Training Workshop Kevin A Cavender EPA-Office of Air Quality, Planning and Standards Precursor Gas Monitoring NO y Monitoring Training Overview

EPA Precursor Gas Training Workshop Outline Methodology Interferences and operational issues Commercially available NOy Monitors Calibration Current work in progress Summary

EPA Precursor Gas Training Workshop Methodology What is NO y ? NO y consists of the sum of all reactive nitrogen oxides. including NO, and NO 2, and other nitrogen oxides referred to as NO z. NO + NO 2 + NO z = NO y The major components of NO z include nitrous acids [nitric acid (HNO 3 ), and nitrous acid (HONO)], organic nitrates [peroxyl acetyl nitrate (PAN), methyl peroxyl acetyl nitrate (MPAN), and peroxyl propionyl nitrate, (PPN)], and particulate nitrates.

EPA Precursor Gas Training Workshop Methodology Why Measure NO y ? NO y is a precursor to both ozone and PM 2.5 formation Conventional NOx boxes “accidentally” measure some NO z species, but not all.

EPA Precursor Gas Training Workshop Methodology Measurement Principles NO is measured based on its chemiluminescent reaction with O 3 NO > NO 2 + hv The amount of light generated is linearly proportional to the concentration of NO. NO y is measured by first passing the sample through a converter that converts NO 2 and NO z species to NO and then measuring for NO as above.

EPA Precursor Gas Training Workshop Methodology Diagram of a High Sensitivity NO y instrument

EPA Precursor Gas Training Workshop Methodology What makes a high sensitivity NO y monitor different than a conventional (low sensitivity) NO x monitor? A high sensitivity NO y monitor is very similar to conventional NO x monitors with the following exceptions: Remote converter is located at sample inlet, not inside monitor Pre-reactor to reduce non-NO y interferences Increased sample flow rate Reduced reaction chamber temperature and pressure

EPA Precursor Gas Training Workshop Installation Remote Converter Remote Converter on 10 meter tower

EPA Precursor Gas Training Workshop Interferences and Operational Issues Reaction of NO with ambient O 3 Ambient ozone will react with NO in sample lines creating negative NO interference Residence in sample line should be kept to less than 2 seconds Ammonia Converter may convert a small amount of ammonia to NO creating positive NO interference Avoid locating near ammonia sources (e.g., feed lots) Converter height above ground level and “fetch”

EPA Precursor Gas Training Workshop Commercially Available NOy Monitors TAPI 200EU/501 NOy TEI 42CY EC9841A-NOy

EPA Precursor Gas Training Workshop Testing Results Make/ModelThermo 42CY NO y (observed) API 200EU/501 (observed) Averaging Time120 seconds Conc. Range0-100 ppb Zero Drift (0.1 ppb/day)12 hr. (0.1 ppb) 24 hr. (0.1 ppb) 12 hr. (0.03 ppb) 24 hr. (0.05 ppb) Span Drift20% FS (0.3%) 80% FS (0.6%) 20% FS (0.5%) 80% FS (1.2%) Precision (Coefficient of Variance)1.49%2.67% Bias+/-1.19%+/-2.73% LDL (0.05 ppb)0.05 ppb Noise (0.025 ppb)0.013 ppb0.009 ppb Linearity (1% FS. M, B, and R 2 reported) x R 2 = x R 2 = MDL Observed0.050 ppb (0.03 – 0.13 ppb CL)0.058 ppb (0.04 – 0.11 ppb CL)

EPA Precursor Gas Training Workshop NOy Span Response

EPA Precursor Gas Training Workshop NOy Precision Response

EPA Precursor Gas Training Workshop Histogram of NOy Data Collected at Burden's Creek Site 5/1/05-1/29/06 Percent Concentration (ppb) NO NOy NO2 + NOz

EPA Precursor Gas Training Workshop Histogram of NOy Data Collected at Burden's Creek Site 5/1/05-1/29/06 BinNONOyNO2+NOz Total4630

EPA Precursor Gas Training Workshop Instrument Operation Initial Calibration Note: Supply sufficient calibration gas to ensure excess flow through converter inlet (supply > 5 liters per minute) Supply zero air until stable readings are obtained (approximately minutes) Adjust monitor to read zero response for NO and NO y. Supply NO calibration gas at approximately 90% of scale Adjust monitor after stable NO and NO y readings are obtained Add ozone to calibration gas to produce NO 2 at approximately 70% of scale Amount NO decreases equals the amount of NO 2 created Calculate conversion efficiency as (NO y -NO)/(NO 2 created) Conversion efficiency should be greater > 96%. Adjust NO 2 + NO z reading to amount of NO 2 created

EPA Precursor Gas Training Workshop Instrument Operation Converter Efficiency Test Converter efficiency test designed to challenge converter with more difficult to convert NO y species N-propyl nitrate, isopropyl nitrate Supply sufficient calibration gas to ensure excess flow at converter inlet (> 5 liters per minute) Supply calibration gas at approximately 90% of scale Allow sufficient time for readings to stabilize Calculate converter efficiency as – (NOy reading/Concentration Suppliedx100%) If converter efficiency is less than 96% the converter should be repaired/replaced

EPA Precursor Gas Training Workshop Current Work In Progress Evaluation of inlet materials for API –Testing HNO3 loss on stainless steel, silico steel, and FTP teflon. Evaluation of “proof of concept” NO/true NO 2 /NOy monitor –Two converters Moly for NOy High intensity LED for NO 2

EPA Precursor Gas Training Workshop Questions?