Annually, ~ 3.6 million abandoned oil and gas wells in the U.S. emit a combined ~ 3.2 Tg methane (CH4), adversely affecting climate and regional air quality. However, these estimates depend on emission factors derived from inventorying sub-populations of wells, but which vary by orders of magnitude due to inadequate sampling numbers. This problem is exacerbated by regional differences requiring independent emission inventories and the recent identification of poorly characterized super-emitters that skew the distribution. Currently, U.S. funding to remediate orphaned wells lacks standardized quantification methods needed to both prioritize plugging and account for emission reductions. Sensitive, reliable, affordable, and scalable CH4 flux quantification methods are needed. We evaluate a simple Gaussian plume method constrained by in situ ground measurements of CH4 concentrations and winds to estimate the leak rate from an orphan well in the Permian basin. We derive a flux of 10.53 ± 1.16 kg CH4 h-1 during a venting procedure that agrees with the directly measured volumetric flow rate of 9.0 ± 0.25 kg CH4 h-1. This is 71% greater than the flux measured 7-months prior which induces a bias between bottom-up and top-down estimates. Additionally, we discovered a secondary leak through the surface-casing inferred as 0.43-0.67 kg CH4 h-1 by both our ground Gaussian analysis and by transecting the plume with an uncrewed aerial system (UAS). Our technique addresses operational needs by reducing sampling time of leak detection and quantification and good sensitivity to characterize wells emitting below the detection limit of satellites.

We present indirect measurements of size-resolved ultrafine particle composition conducted during the Ocean–Atmosphere–Sea Ice–Snowpack (OASIS) Campaign in Utqiagvik, Alaska, during March 2009. This study focuses on measurements of size-resolved particle hygroscopicity and volatility measured over two periods of the campaign. During a period that represents background conditions in this location, particle hygroscopic growth factors (HGF) at 90% relative humidity ranged from 1.45-1.51, which combined with volatility measurements suggest a mixture of ~30% ammoniated sulfates and ~70% oxidized organics. Two separate regional ultrafine particle growth events were also observed during this campaign. Event 1 coincided with elevated levels of H2SO4 and solar radiation. These particles were highly hygroscopic (HGF=2.1 for 35 nm particles), but were almost fully volatilized at 160 °C. The air masses associated with both events originated over the Arctic Ocean. Event 1 was influenced by the upper marine boundary layer, while Event 2 spent more time closer to the surface and over open ocean leads, suggesting marine influence in growth processes. Event 2 particles were slightly less hygroscopic (HGF=1.94 for 35nm and 1.67 for 15nm particles), and similarly volatile. We hypothesize that particles formed during both events contained 60-70% hygroscopic salts by volume, with the balance for Event 1 being sulfates and oxidized organics for Event 2. These observations suggest that primary sea spray may be an important initiator of ultrafine particle formation events in the Arctic late-winter, but a variety of processes may be responsible for condensational growth.

Pyrocumulonimbus clouds have a complex origin depending on fire dynamics and meteorological conditions. When a pyrocumulonimbus (PyroCb) cloud formation develops and is maintained over a period of time, it can inject significant aerosol into the troposphere and lower stratosphere, resulting in longer term (months to years) climate cooling effects. In this work we investigate the British Columbia and northern Washington wildfires on August 12-13, 2017 using a multi-scale simulation framework. We use the output of a physics based wildfire model (FIRETEC) with parameterized energy, particle, and gas emissions to drive the upper atmospheric aerosol mass injection within a regional cloud resolving model (HIGRAD). We demonstrate that vertical motions produced by latent heat release of the condensation of ice and cloud particles within the PyroCbs induce another 5 km of lifting of the simulated aerosol plume. Primary black carbon and organic aerosols alone may not be enough to explain the observed aerosol burden, thus we show that dust and ash particles can enhance lofted aerosol mass. Additionally, we show that semi volatile organic gases emitted by the fires eventually condense, further increasing the aerosol burden. A simulation with all aerosol mechanisms active, driven by the observed fuel load and environmental conditions, reasonably reproduces an aerosol profile inferred from observational data.