Measurements of diffuse emissions of CH4 and NMVOCs from oil production and stationary sources using optical methods.  

<p>VOCs correspond to a large number of species which in turn can be categorized into different chemical groups such as: alkanes (e.g. methane, propane, butane etc.), alcohols (e.g. ethanol and propanol, alkenes (e.g. ethene and propene), aromatic hydrocarbons (e.g. benzene and toluene) and aldehydes (e.g. formaldehyde and acetaldehyde). VOCs contributes to the formation of ground level ozone, which is formed through atmospheric chemical reactions of volatile organic compounds and nitrogen oxides (NOx) in the presence of sunlight. Elevated ozone concentrations are known to reduce crop yields and constitute a public health concern and has a climate impact similar to N2O.</p> <p>Stationary sources such as refineries, storage depots, petrochemical facilities and oil production activities are the largest point sources of VOCs. The emissions are typically dominated by evaporative losses from storage tanks and process equipment, so-called diffuse emissions. Several VOCs are also toxic with direct impact on health such as benzene and formaldehyde.</p> <p>In this study, we will show results from measurements in 2021 of diffuse emissions of CH4 and NMVOCs from oil production sources in California using optical methods. At Chalmers, several unique optical techniques have been developed. Two of the techniques, the solar occultation flux (SOF) method, Fig 1, and mobile sky DOAS, measure the gas columns of VOCs and NO2, SO2, and formaldehyde, respectively, and from these measurements, it is possible to derive the gas emissions from a certain source by combining with wind speed. The other two techniques, Mobile extractive FTIR and Mobile extractive DOAS yield the ground concentration of multiple species. Emissions of VOCs, methane and air toxics from several of California’s largest-producing oil fields in Kern County were measured. A total of 4500 kg/h of alkanes and 8900 kg/h of methane were measured from 11 fields.  These data have been compared to emission models.</p>