2017 A&WMA Air Quality Measurement Methods and Technology

Technical Presentation

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Carol Meyer
Session 3B: Air Toxics

Taking Your Lab to the Field: AutoGC Systems and the Data They Generate

Carol Meyer (Orsat, LLC)

Wednesday, Nov 8th | 10:40 AM | Broadlind Ballroom, 2nd Floor, Renaissance Long Beach Hotel

Abstract: Unlike the data collected by automated gas chromatographic systems used for process control, the VOC data collected by AutoGC systems used at Photochemical Assessment Monitoring Sites is collected for use in ambient air modeling. Data collected for ambient air modeling requires that every analysis meet minimum requirements for quality in order to develop the necessary population of data to allow modelers to adequately represent the spacial and temporal data necessary for sophisticated models. However, unlike high quality laboratory results, AutoGCs are capable of generating a large amount of data and this makes the problems associated with real-time review more difficult. Emphasis on data completeness necessitates that operators must be able to evaluate the instruments performance in real time with minimum interruptions.

Like data collected in a laboratory, data must be reviewed and validated to achieve the necessary quality objectives. The best chromatographic systems are capable of repeatable, accurate analysis but when systems are un-attended it is not always clear when problems arise. The problems associated with meeting the data objectives of the PAMS VOC monitoring network can be divided into two categories; those associated with operations and those associated with data validation.

From the standpoint of operations, it is important to choose an analytical system which will make collection of the data not only efficient but also minimize operator intervention. To determine the minimum criteria that the operator must meet it is helpful to look at the elements of the analysis most likely to vary across routine sampling. Assuming the system is calibrated and capable of low drift, the two most significant sources of data loss in continuous monitoring are failure of the sample to be collected within the sample hour and failure of the data system to correctly identify the target analytes. Current state-of-the-art data systems can compensate for variations in retention times associated with changing room temperatures or sample humidity by the use of retention time references. This makes the operator’s primary job one of checking that the system is sampling and that samples are collected each hour as planned. The third measurement of system performance is the stability of the instruments response. To track this a daily check sample and blank can be run so the operator merely inspects these for instrument performance. These checks should include targets at a reasonable concentration and across the range of boiling points to adequately represent the range of the ambient air, generally C2 – C9. If operators can verify that targets are identified correctly, the sample is collected within the correct interval and that the instrument response has not changed then the data should pass further validation.

It is not practical for operators to review every chromatogram so some systematic review of this large amount of data must be achieved to validate results. Some problems which occur can be corrected by simply reprocessing some data. Changes in flows, temperatures, humidity may case analytes to shift slightly and become miss identified. Equipment failures or power interruptions occur and data must be reviewed to determine accuracy and ultimately some will be lost. While fully automated systems can collect a large amount of quality data, they can also collect a large amount of poor quality data as well. Identifying problems, implementing corrective actions and determining what is valid or invalid is still a challenge. This presentation will present tools which will help both operators and validators review hourly VOC data generated from AutoGC sites.

Carol MeyerCarol Meyer has been actively involved with PAMS monitoring since the initial 1993 Coastal Ozone Assessment for Southeastern Texas (COAST) study. Orsat, LLC has provided ambient monitoring services to both state and industry, and currently operates 25 PAMS AutoGC monitoring sites in Texas for the TCEQ, UT CEER and AECOM. Using both the PerkinElmer Ozone Precursor system and the Agilent GC System with a Markes Unity 2 thermal desorber, Orsat has developed a fully automated application for the continuous monitoring of 56 NMHCs hourly.

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One of A&WMA’s most well attended events, the Air & Waste Management Association’s Air Quality Measurement Methods and Technology conference provides a forum for current advances in measurement technology covering all aspects of air quality, including ambient air, indoor air, point sources, and area sources. Professionals from academia, consulting, industry, government, and manufacturers will gather to hear the latest information on available technology, including new monitoring networks and regulations from industry and government experts, as well as citizen and community monitoring efforts.
Air quality issues related to greenhouse gas measurements, ambient monitoring, fugitive and area source air measurements, quality assurance, and data uses in order to improve models, emission inventories, and policy decisions will also be addressed. Includes multiple concurrent sessions, 20+ vendor exhibits, and plenty of networking time.

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