What Does the Future Hold for Ambient Air Monitoring Regulations?

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1 An Executive Summary What Does the Future Hold for Ambient Air Monitoring Regulations? A PAMS Site Instrumentation Evaluation for VOC Monitoring Nicola Watson Sales Support Manager - Americas Markes International Greg Harshfeild Continuous Monitoring and Data Systems Supervisor CDPHE Dwain Cardona Environmental Vertical Marketing Manager Thermo Fisher Scientific Overview New Rules established in the 1990 Clean Air Act Amendment (CAAA) require enhanced monitoring of ozone, nitrogen oxides, and volatile organic compounds (VOCs) to collect comprehensive and representative data on ozone air pollution. Subsequent regulations required states to establish Photochemical Assessment Monitoring Stations (PAMS) in ozone nonattainment areas classified as serious, severe, or extreme. The Environmental Protection Agency (EPA) recently commissioned an assessment of currently available instrumentation to be used at these sites in the future including Auto Gas Chromatography (GC) units that measure VOCs in ambient air. This manuscript discusses the two-year evaluation of a combined Markes International and Thermo Fisher Scientific TD-GC-MS air monitoring solution. Included in the manuscript is a review of a new project using this system for online VOC and SVOC (semivolatile organic compounds) monitoring of oil well sites in collaboration with the Colorado Department of Public Health and Environment. The EPA PAMS Update The EPA PAMS Update was published in the Federal Register on October 27, 2015 providing the requirements for replacing the 20-year-old multisite design with an updated two-part network design. Initially, it requires PAMS measurements to be taken at existing National Core (NCORE) multipollutant network sites in areas with populations of one million people or more irrespective of Ozone NAAQS attainment status. A network of approximately 40 required sites will be established with waivers for historically low-ozone areas (i.e., <85% of the U.S. National Ambient Air Quality Standards) as well as sites that already have established PAMS at alternative locations. In addition, hourly VOC measurements are now required because eight-hour canister sampling has been phased out, although a waiver can be obtained to allow three eight-hour canister samples in locations with low VOC concentrations and for logistical and programmatic constraints. By June 2019, the network will be complete and monitoring will begin. The older PAMS network design with types one, two, three, and four monitoring stations are clustered on the East and West Coasts with an additional concentration of systems in the Texas area, providing a somewhat limited view. The new design achieves a much more evenly spaced network to look at background levels in the Midwestern states in addition to those monitored previously (see Figure 1). SPONSORED BY

2 Figure 1: Proposed PAMS sites. PAMS Instrument Evaluation The PAMS Evaluation started in the spring of 2014, before the update s release including both laboratory and field based testing scenarios. Laboratory evaluations included eight different GC systems which were tested with controlled gasses to evaluate the system s performance for precision, bias and the effect of temperature and humidity on sample measurement. Field evaluations were carried out between the springs of 2015 and GC systems were installed in a mobile trailer to evaluate system ruggedness and robustness. The final report for this field evaluation and overall rankings are not yet available, but a draft report has been circulated to internal parties. In addition, preliminary data was presented in August 2016 at the EPA s National Ambient Air Monitoring Conference in St. Louis. The Markes UNITY Air Server-xr sample introduction system was used during the evaluations. This system was designed for online sampling and is available in a three- or eight-channel configuration. The three-channel configuration was used during the evaluation because it allows for cycling between a sample gas, a standard gas, and a blind gas without any manual intervention. Sampling is performed by pulling air through a focusing trap containing a mixture of absorbents specifically designed for PAMS setups. During collection the trap is electrically cooled to 30 C, removing the need for cryogen cooling. Once the sample has been collected, the trap is heated to drive compounds into the gas phase and the flow of gas through the focusing trap is reversed carrying the compounds into GC MS system for separation and detection. It is important to note that multiple sorbents can be packed within the trap to accommodate a wide compound volatility range. In addition an optional split can be used to collect samples onto a clean thermal desorption tube, if desired. Figure 2 demonstrates the PAMS results obtained for the analysis of an ozone precursor standard. The ozone precursor standard was blended with several interference standards (i.e., compounds not on the target list that might be observed) to see how well the system could resolve this complex mixture. Figure 3 illustrates the system s performance for one of the most volatile compounds in the PAMS target list: acetylene. For this analysis, the sample volume was increased to 1.5 liters and a linear response was still obtained without any breakthrough or loss of this compound from the end of the trap (see the left side of Figure 3). Collecting more sample lowers the level of detection as a result of concentrating more mass on the trap. The right side of Figure 3 also shows the use of the UNITY Air Server-xr used in the analysis of compounds not included on the PAMS target list such as four ultra-volatile greenhouse gasses: carbon tetrafluoride, hexafluoroethane, sulfur hexafluoride, and nitrous oxide. In direct sampling applications is very important to manage the amount of external moisture coming into the system.. Historically, PAMS systems have employed a Nafion dryer to remove water from the sample before concentration on the focusing trap which allows the analysis of non-polar compounds. In doing so, however, the Nafion dryer also removes some polar compounds of interest. Another solution for moisture management is to trap compounds at higher temperatures, but for the PAMS application, acetylene was not completely recovered when the trap was set at 25 C due to a lack of retention for highly volatile compounds on the sorbents at the higher temperature. Operating the trap at higher temperatures does, however, allow the detection of other ozone precursors and oxygenates. To balance these approaches another option is to alternate runs with and without the Nafion dryer, although this approach does extend sampling and analysis time. Because there was no clear solution that met all the needs of the PAMS analysis a new water management technique was needed. The Kori-xr was developed to manage moisture introduced during sampling and meet the goals of the PAMS analysis. This device fits between the sampling mechanism and the UNITY Air Server-xr and is used to dry incoming sample by abstracting water in a phase change from gas to solid. The empty Kori-xr trap, held at 30 C, sits between the sample

3 Figure 2: Application: Photochemical Assessment Monitoring Station (PAMS). On-line monitoring of ozone precursors (C 2 to C 9 hydrocarbons) using TD GC MS Driven by the US and China's need to analyze VVOCs, VOC (polar/non polar) from humid samples. Figure 3: Online Sampling: Air Server-xr. VVOCs Ultra Volatile retention without Cryogen Cryogen free, quantitative retention, of acetylene from 1500 ml without breakthrough Ultra-volatile greenhouse gases from ambient air CF 4 (Carbon tetrafluoride) C 2 F 6 (Hexafluoroethane) SF 6 (Sulphur hexafluoride) N 2 O (Nitrous oxide) inlet and the focusing trap, causing only vapor-phase water to be deposited directly as ice before it reaches the trap, thereby minimizing polar compound loss. While the sample is being transferred to the GC, the Kori-xr trap is heated while gas flow is reversed causing the trapped water to be expelled and preparing Kori-xr for the next sample. Figure 4 compares water management options for monitoring polar species in humid environments using the Kori-xr. Development of a Mobile Air Quality Laboratory Recently, an executive order from the state of Colorado made funding available for a mobile air-quality laboratory. To decide

4 Figure 4: Kori-xr An innovative approach for monitoring polar species in humid environments. Kori-xr was developed in collaboration with the University of York (in UK) under a Knowledge Transfer Program. which analyzers to purchase and the laboratory s exact analytical capabilities, a list of goals, priorities, and analytes was developed. The goals and priorities included: Priority 1: Oil and Gas (O&G) Development and Production $ $ Respond to citizens complaints and perform toxicological risk assessments $ $ Source identification of unknowns $ $ Quantitation of natural gas components (e.g., hydrocarbons and hydrogen sulfide) $ $ PAMS target list $ $ Quantitation of ancillary O&G product (e.g., solvents, dust, and nitrogen oxides) $ $ TO-15 target list The EPA PAMS target list contains compounds that are primary emissions and are common precursors to ozone formation (e.g., hydrocarbons, alkanes, alkenes, alkynes, and aromatics). The EPA TO-15 target list is a subset of EPA s HAPS target list. This list contains halogenated compounds, oxygenated compounds, sulfur and nitrogen compounds, alkanes, alkenes, and aromatics. These compounds are selected based upon toxicity and are not necessarily ozone reactive. There is some overlap between the PAMS and TO-15 lists; these compounds are a high priority because of their high ozone reactivity and toxicity. Based on priorities, an analytical system capable of speciating hydrocarbons like GC with either mass spectrometry (MS) or flame ionization detection (FID) is required. The State of Colorado chose the Thermo Scientific TRACE 1310 Gas Chromatograph with two flame ionization detectors and the Thermo Scientific ISQ Mass Spectrometer in combination with the Markes Unity Air Server-xr. In addition to favorable test results, several factors helped make this the best match for the mobile laboratory. Key factors for deciding on the Markes/Thermo Scientific TD-GC-MS system included existing factory method development for PAMS compounds and the PAMS method, easy source removal and cleaning, the small footprint, the low cost and the Markes inlet options of whole air, summa canister, or desorption tubes. For this project all the analytical systems and equipment integration have been recently completed and the process of field method development is in process. Priority 2: Colorado Air Pollution Investigations $ $ Identification and quantitation of ozone precursors $ $ PAMS target list $ $ Transformation of ozone precursors $ $ TO-11 target list Priority 3: Emergency Response $ $ Determining population exposure to hazardous air pollutants (HAPS) $ $ Identification and quantitation of HAPS and unknowns Benefits of Mass Spectromentry (MS) for PAMS and other Continuous Air-Monitoring Efforts PAMS sites have traditionally used gas chromatographs with dual flame ionization detectors for VOC measurement. With a MS detector, however, complex air samples can be analyzed in full scan mode to collect data over a defined mass range. The resulting spectra provide a unique signature that can be used to distinguish compounds from one another. In addition, spectral libraries can be used to identify unknowns, while extracted ion chromatograms can help to resolve compounds of interest from interferences, thus aiding in quantitation.

5 Figure 5: GC-MS Data - What advantages does it bring? Showing TraceFinder analysis of a software 1 ppb ozone analysis precursor of a 1 ppb standard ozone blended precursor with standard interferents. blended n- with Nonane interferents. has been n-nonane selected and has ions been 85 selected and 99 have and ions been 85 compared and 99 have to give been and compared ratio of to 23.26% give and in ion keeping ratio with of 23.26% the NIST in keeping matched with spectra. the NIST matched ion spectra. Figure 5 illustrates how MS detection is used. The top chromatogram shows both the compounds of interest and the interferences. The spectra in the center show the n-nonane sample compared with the library spectra below it. On the left and right sides, the extracted chromatograms for the ions present in the spectra for n-nonane are seen. These ions are used for both quantitation and ion-ratio compound identification. The ease and efficiency of routine maintenance and troubleshooting, particularly in a mobile laboratory application, is also critical. A modular design simplifies troubleshooting and routine maintenance. To maintain sensitivity, all MS instruments require routine source cleaning. The source of the ISQ Mass spectrometer is removable while the system is still under vacuum. Using the access valve built into the mass spectrometer, routine maintenance can be performed in less than two minutes removing the need to open the manifold, ultimately reducing downtime during source cleaning. This factor is key in continuous-monitoring PAMS applications. In addition, a suite of software of tools enables analysts with limited MS data experience to easily analyze the data. Both Thermo Scientific Chromeleon and Thermo Scientific Tracefinder Software can perform all the necessary ion extraction, library comparison, and quantitation. The software also allows instrument control, sequence generation, processing, and data reporting to be automated yet another key requirement for remote site air monitoring stations. Conclusion The Kori-xr water abstraction device and the Markes UNITY Air Server-xr inlet options, when used in combination with the Thermo Scientific GC-MS ISQ mass spectrometer system and the Thermo Scientific Chromeleon Chromatography Data System or Thermo Scientific Tracefinder Software, provide significant advantages over traditional Auto GC FID systems. The systems ease of use, efficiency, speed, and robustness meets all requirements for remote mobile laboratory monitoring at future PAMS sites as well as the initiative for monitoring oil well sites recently launched by the state of Colorado.