Methods, fluxes and sources of gas phase alkyl nitrates in the coastal air

Abstract

The daily and seasonal atmospheric concentrations, deposition fluxes and emission sources of a few C3-C9 gaseous alkyl nitrates (ANs) at the Belgian coast (De Haan) on the Southern North Sea were determined. An adapted sampler design for low- and high-volume air-sampling, optimized sample extraction and clean-up, as well as identification and quantification of ANs in air samples by means of gas chromatography mass spectrometry, are reported. The total concentrations of ANs ranged from 0.03 to 85 pptv and consisted primarily of the nitro-butane and nitro-pentane isomers. Air mass backward trajectories were calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to determine the influence of main air masses on AN levels in the air. The shorter chain ANs have been the most abundant in the Atlantic/Channel/UK air masses, while longer chain ANs prevailed in continental air. The overall mean N fluxes of the ANs were slightly higher for summer than those for winter-spring, although their contributions to the total nitrogen flux were low. High correlations between AN and HNO₂ levels were observed during winter/spring. During summer, the shorter chain ANs correlated well with precipitation. Source apportionment by means of principal component analysis indicated that most of the gas phase ANs could be attributed to traffic/combustion, secondary photochemical formation and biomass burning, although marine sources may also have been present and a contributing factor.

Photochemical Formation of C1–C5 Alkyl Nitrates in Suburban Hong Kong and over the South China Sea

“…Similar to O 3 , observed RONO 2 usually showed a peak at midday, reflecting the dominance of photochemical reactions. , Besides, studies have confirmed that RONO 2 are also directly emitted from the oceans, particularly for light (<C 2 ) RONO 2 . , Biomass burning is also a source of RONO 2 , which are quickly formed through the pathway of RO + NO 2 . , The source contributions may vary in different locations and/or under the influence of different origins of air masses. , …”