Evaluation of selected solid adsorbents for passive sampling of atmospheric oil and natural gas non-methane hydrocarbons
Creators: name: Helmig, Detlev
name: Fangmeyer, Jens
name: Fuchs, Joshua
name: Hueber, Jacques
name: Smith, Kate
Publisher: name: Taylor & Francis
Year: 2022
Subjects: subject: Biophysics
subject: Space Science
subject: Medicine
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Ecology
subject: FOS: Biological sciences
subject: 69999 Biological Sciences not elsewhere classified
subject: Science Policy

description: This project investigated passive adsorbent sampling of light (C<sub>2</sub>-C<sub>5</sub>) hydrocarbons which are sensitive tracers of fugitive emissions from oil and natural gas (O&amp;NG) sources. Stronger adsorbent materials, i.e. Carboxen 1000 and Carboxen 1016, than those typically used in adsorbent sampling were considered. Experiments were conducted in laboratory and field settings using thermal desorption – gas chromatography analysis. Uptake of water vapor and system blanks were challenges inherent to the increased affinity of these adsorbents. Carboxen 1000 exhibited the best signal-to-noise ratio for the target compounds after optimizing conditioning parameters to reduce blanks, and by reducing the adsorbent mass loaded in the cartridge. This strategy reduced blanks to equivalent ambient air mole fractions of &lt;0.05 nmol mol<sup>−1</sup> (ppb), and allowed determination of these O&amp;NG tracers over three-day sampling intervals with a lower detection limit of ≥0.5–1 ppb. Linear VOCs uptake was observed in dry air. Water uptake was as high as 0.65 g<sub>H2O</sub> g<sup>−1</sup><sub>adsorbent</sub> at relative humidity (RH) above ≈ 75%. The water collection passivates adsorbent sites and competes with the uptake rates of VOCs; under the worst case relative humidity level of 95% RH, VOCs uptake rates dropped to 27–39% of those in dry air. This effect potentially causes results to be biased low when cartridges are deployed at high relative humidity (RH), including overnight, when RH is often elevated over daytime levels. Nonetheless, representative sampling results were obtained under ambient conditions during three field studies where cartridges were evaluated alongside whole air sample collection in canisters. Agreement varied by compound: Ethane and alkenes correlated poorly and could not be analyzed with satisfactory results; results for C<sub>3</sub>-C<sub>5</sub> alkanes were much better: <i>i</i>-butane correlated with R<sup>2 </sup>&gt; 0.5, and propane, <i>n</i>-butane, <i>i</i>-pentane, and <i>n</i>-pentane with R<sup>2</sup> &gt; 0.75, which demonstrates the feasibility of the passive sampling of these latter O&amp;NG tracers. <i>Implications:</i> Oil and natural gas development has been associated with emissions of petroleum hydrocarbons that impact air quality and human health. This research characterizes and defines the application possibilities of solid adsorbent sampling for atmospheric passive sampling monitoring of low molecular weight volatile organic compounds (i.e. ethane through pentane isomers) that are most commonly emitted from natural gas drilling and well sites. The passive sampling of these pollutants offers a simple, low cost, and readily applicable monitoring method for assessing emissions and air quality impacts in the surroundings of oil and gas operations.