Low molecular weight alkyl nitrates are produced in surface seawater from the photochemically initiated reaction of NO with organic peroxy radicals. In this study, methyl, ethyl, isopropyl, and n-propyl nitrate photochemical production rates were determined from shipboard incubation experiments. Surface water samples from a variety of different North Pacific water masses were irradiated in sunlight, with and without added nitrite. Production was observed in some, but not all unmodified waters. Production rates increased with increasing addition of nitrite. The relative rates of production of C1, C2, and C3 alkyl nitrates were roughly constant in all production experiments, and similar to the concentration ratios in ambient waters. This constancy most likely reflects consistency in the ratios of the various organic peroxy radicals involved in the reaction ROO + NO. Alkyl nitrate production rates at 1 μM nitrite concentrations generally did not vary markedly by water type, indicating that distribution of nitrite, not organic matter may control photochemical alkyl nitrate formation in the oceans. At higher nitrite levels, differences in production rates may reflect variations in the concentration or reactivity of dissolved organics. © 2008 Elsevier B.V. All rights reserved.

Dimethyl sulfide (DMS) and sulfur dioxide (SO2) mixing ratios were measured in the boundary layer on Oahu, Hawaii in April and May 2000. Average DMS and SO2 levels were 22 ± 7 (n = 488) pmol/mol and 23 ± 7 (n = 471) pmol/mol respectively. Anti-correlated DMS and SO2 diurnal cycles, consistent with DMS + OH oxidation were observed on most days. Photochemical box model simulations suggest that the yield of SO2 and total SO2 sink are ∼85% and ∼2 × 104 molec cm-3 s-1 respectively. On several days the rate of decrease in DMS and increase in SO2 levels in the early morning were larger that predicted by the model. Dynamical and chemical causes for the anomalous early morning data are explored. © Springer Science+Business Media, Inc. 2005.

This paper reports the first measurements of the saturation state of low molecular weight alkyl nitrates (methyl, ethyl, isopropyl, and n-propyl nitrate) in the tropical Pacific Ocean. These compounds were supersaturated with saturation anomalies as high as 2000%. Air/sea flux estimates based on these measurements suggest that surface ocean emissions are sufficient to account for observed levels of tropospheric alkyl nitrates in this region. Model calculations suggest that atmospheric loss rates are faster than can be explained by photolysis and reaction with OH alone. The implication is that removal via transport is important, and there must be a net export of alkyl nitrates from the tropics to other regions of the atmosphere.

Alkyl nitrates have been observed in remote oceanic regions of the troposphere and in the surface ocean. The mechanism for their production in the oceans is not known. A likely source is the reaction of ROO + NO (where R is an alkyl group). Steady-state laboratory experiments show that alkyl nitrates are produced in the aqueous phase via this reaction, with branching ratios of 0.23 ± 0.04, 0.67 ± 0.03, and 0.71 ± 0.04 for methyl, ethyl, and propyl nitrate respectively. The branching ratios in aqueous solution are significantly higher than in the gas phase. Irradiation of surface seawaters yield rates of alkyl nitrate production on the order of 10⁻¹⁸ mol cm⁻³ s⁻¹, suggesting that the reaction of ROO and NO is an important source of alkyl nitrates in seawater.

This is a review of the first 50 patients attending a colocated continuity clinic with harm reduction services to women experiencing homelessness in north Seattle. Among those tested, patients had high rates of curable sexually transmitted infections (44%), injection opioid use (36%), transactional sex (69%), unintended pregnancy (10%), and human immunodeficiency virus infections (10%).