Paul B. Shepson

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Forest emissions of biogenic volatile organic compounds (BVOCs), such as isoprene and other terpenes, play a role in the production of tropospheric ozone and aerosols. In a northern Michigan forest, the direct measurement of total OH reactivity, which is the inverse of the OH lifetime, was significantly greater than expected. The difference between measured(More)
Bromine atoms are believed to play a central role in the depletion of surface-level ozone in the Arctic at polar sunrise. Br2, BrCl, and HOBr have been hypothesized as bromine atom precursors, and there is evidence for chlorine atom precursors as well, but these species have not been measured directly. We report here measurements of Br2, BrCl, and Cl2 made(More)
During the Southern Oxidants Study 1999 field campaign at Dickson, TN, we conducted measurements of the n-aldehydes propanal, pentanal, hexanal, heptanal, octanal, and nonanal. Propanal and nonanal tended to have the largest concentrations, with afternoon maxima of approximately 0.3 ppb. These aldehydes typically represented a significant fraction of the(More)
The identification and quantification of methane emissions from natural gas production has become increasingly important owing to the increase in the natural gas component of the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern PA in June 2012. A large regional flux,(More)
Following the springtime polar sunrise, ozone concentrations in the lower troposphere episodically decline to near-zero levels1. These ozone depletion events are initiated by an increase in reactive bromine levels in the atmosphere2–5. Under these conditions, the oxidative capacity of the Arctic troposphere is altered, leading to the removal of numerous(More)
Although oxidation of biogenic volatile organic compounds (BVOCs) plays an important role in tropospheric ozone and secondary organic aerosol production, significant uncertainties remain in our understanding of the impacts of BVOCs on ozone, aerosols, and climate. To quantify BVOCs, the proton-transfer reaction linear ion trap (PTR-LIT) mass spectrometer(More)
Received for review February 17,1988. Accepted June 1,1988. Funding for this research was provided by the National Oceanic and Atmospheric Administration Grant 50-DGNC-5-00262 (Status and Trends Mussel Watch Project) and Texas A&M University Sea Grant (RIES-18). Maquire, R. J.; Chau, Y. K.; Bengert, G. A.; Hale, E. J.; Wong P. T. S.; Kramar, 0. Environ.(More)
We present estimates of regional methane (CH4) emissions from oil and natural gas operations in the Barnett Shale, Texas, using airborne atmospheric measurements. Using a mass balance approach on eight different flight days in March and October 2013, the total CH4 emissions for the region are estimated to be 76 ± 13 × 10(3) kg hr(-1) (equivalent to 0.66 ±(More)
Photolysis of nitrous acid generates hydroxyl radicals—a key atmospheric oxidant—in the lower atmosphere. Significant concentrations of nitrous acid have been reported in the rural atmospheric boundary layer during the day, where photolysis of nitrous acid accounts for up to 42% of sunlight-induced radical production1–7. The observed concentrations of(More)