Long-path atmospheric measurements using dual frequency comb spectroscopy

Kevin Cossel
NIST, Boulder, CO

Open-path measurements of atmospheric gas species over km-scale path lengths are well suited to quantify emissions from sources like oil and gas production, agricultural activities, forest fires, and industry. Our group at NIST has developed open-path dual frequency comb spectroscopy (DCS) as a tool to provide accurate measurements of multiple trace gas species simultaneously across path lengths ranging from 100 m to >10 km.

We have used these systems for a number of field measurements. In the first campaign, we deployed a prototype system in the mid-infrared spectral region to a new oil and gas well installation in order to measure emissions during the different stages of unconventional well development. In another measurement, we deployed to the Platteville Atmospheric Observatory in north-eastern Colorado or 4 months. This site is located in the Denver-Julesburg oil and gas basin and in an area with a large number of confined animal feeding operations, leading to a complex mixture of trace gas emissions. By using measurements of ethane and NH3, we can attribute the observed CH4 to the oil and gas and agricultural sectors. We also see HCHO plumes that are correlated with C2H6, indicating oil and gas related sources of HCHO (likely from combustion). Finally, we took a system to a beef cattle stocker site to measure emissions of methane and NH3 over several months.

Current opportunities in our group include field measurements working to understand urban greenhouse gas emissions and air quality links, testing mitigation of greenhouse gas emissions in agriculture, and measuring emissions from forests as well as laboratory studies looking at emissions of greenhouse gases and reactive nitrogen from cyanobacteria and combustion.

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Expanding the Use of 9F NMR Spectroscopy in Per- and Polyfluoroalkyl Substance Analysis
Andre Schaum,
ANYL 1st year, CU Boulder

Aqueous film-forming foams (AFFFs) have been used to extinguish liquid-fuel fires since the 1960s and are significant historical sources of per- and polyfluoroalkyl substances (PFAS) in the environment. Though in the process of being phased out of use in the United States, large stockpiles of AFFFs still exist nationwide, often stored in poorly labeled containers and tanks. For proper assessment and disposal, rapid and inexpensive analytical methods are needed to quantify total fluorine, determine PFAS composition, and identify AFFF type. Current analytical methods that provide quantitative measures of individual PFAS in AFFFs, such as liquid chromatography – tandem mass spectrometry (LC-MS/MS), are often complicated, time-consuming, and expensive. Methods for total fluorine analysis, though quantitative, provide relatively little information on the chemical nature of PFAS in AFFFs. Fluorine Nuclear Magnetic Resonance Spectroscopy (9F NMR) has previously been used to characterize PFAS in environmental matrices, technical mixtures, and analytical standards, though its application to AFFFs has been limited. Here, a 9F NMR method was developed for rapid qualitative and quantitative analysis of fluorine content in AFFFs and used to identify the manufacturing method of two AFFFs of unknown origin.