The measurement of C3-C5 alkyl nitrates at a coastal sampling site in the southern hemisphere

doi:10.1016/0045-6535(94)90106-6

Chemosphere

Volume 29, Issue 2, July 1994, Pages 299-310

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Abstract

The mixing ratios of alkyl nitrates measured at a coastal site on the south-east coast of Southern Africa were generally in the low-pptv range. Variations in absolute and relative concentrations of the alkyl nitrates could be related to changes in meteorological conditions. It is considered that the differences observed in chemical composition may represent different sources of trace gas emissions or different degrees of photochemical processing of similar sources. The measured levels of the alkyl nitrates suggest long-range transport to play a major role in regulating the distribution of alkyl nitrates in the troposphere.

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Cited by (13)

Levels and pattern of volatile organic nitrates and halocarbons in the air at Neumayer Station (70°S), Antarctic
2002, Chemosphere
Levels and patterns of C1–C4/C9 organic nitrates were measured for the first time in Antarctica. The sampling was done by adsorptive enrichment on Tenax TA followed by thermodesorption cold-trap high resolution capillary gas chromatography with electron capture detection. 2–70 l air on-column have been analyzed this way. C1–C9 alkyl mononitrates, C2–C4 alkyl dinitrates, C2–C4 hydroxy alkyl nitrates, and halocarbons could be identified in air samples collected near the German Neumayer Research Station, Antarctica, in February 1999. Volatile biogenic and anthropogenic halocarbons were used to assess the origin of the air parcels analyzed. The average concentration measured for ∑C2–C6 alkyl nitrates was in the range of 9.2±1.8 ppt(v), while the sum of the mixing ratios of six C2–C4 hydroxy alkyl nitrates was in the range of 1.1±0.2 ppt(v). Moreover, C2–C4 alkyl dinitrates were found at levels near the detection limit of 0.1–0.5 ppt(v). The concentrations of organic nitrates found in Antarctic air represent ultimate baseline levels due to chemical and physical loss processes during long-range transport in the air. The South Atlantic and the Antarctic Ocean as a general secondary source for organic nitrates in terms of an air/sea exchange equilibrium has to be evaluated yet, but it seems logical. Our results confirm the common assumption that there are no biogenic marine sources of C2–C9 organonitrates. We have found a level of >80 ppt(v) for methyl nitrate. This level if it can be confirmed in a systematic survey requires a strong biogenic source of methyl nitrate in the Antarctic Ocean.
Alkyl nitrates as achiral and chiral solute probes in gas chromatography: Novel properties of a β-cyclodextrin derivative and characterization of its enantioselective forces
1999, Journal of Chromatography A
Achiral and chiral interactions of alkyl nitrates (R–O–NO₂) with heptakis-(3-O-acetyl-2,6-di-O-pentyl)-β-cyclodextrin (LIPODEX-D) in the gas phase were investigated chromatographically. Two major outcomes can be summarized. First, LIPODEX-D shows very fast temperature-dependent variations of the selectivity up to changes in the order of elution for C₁–C₅ alkyl nitrates. These changes in selectivity reveal that LIPODEX-D possesses different shape selectivities for small alkyl nitrates at different temperatures (40–80°C), i.e. with increasing isothermal separation temperature extended (chain-like) alkyl nitrates have increased retention relative to bulky alkyl nitrates. The observations are highly reproducible and might indicate conformational changes of the cyclodextrin, however, an ultimate proof would require further spectroscopic investigation. Secondly, the chiral separations of systematically varied sets of C₄–C₁₁ alkyl nitrates allowed the thermodynamic characterization of enantiodiscriminating interactions. Quantitative evidence is provided showing that the presence of an ethyl group at the asymmetric carbon atom of an n-alkyl nitrate gives a strong enthalpic contribution to the resulting enantioselectivity. The Gibbs free energy differences −ΔR_R,S(ΔG) decrease systematically three to six times if the ethyl group is either shortened or enlarged by only a –CH₂–increment. The results are based on two separate thermodynamic approaches, i.e. the determination of thermodynamic quantities (−Δ_R,S(ΔG), −Δ_R,S(ΔH), −Δ_R,S(ΔS), T_iso) and a theoretical concept of enthalpy–entropy compensation. The data from our laboratory experiments also indicate that van der Waals interactions are responsible for chiral discrimination.
C<inf>3</inf>-C<inf>14</inf>-alkyl nitrates in remote South Atlantic air
1999, Chemosphere
Alkyl nitrates with chain lengths up to fourteen carbons have been detected in the remote troposhere of the South Atlantic Ocean. The concentrations of numerous iso- and n-alkyl nitrates in the range of C₃C₁₂ have been measured. Tenax-GC analysis was applied to determine short chain alkyl nitrates (< C₆), while the novel detection of long chain iso- and n-alkyl nitrates was achieved with a high volume sampling technique using silica gel. C₃C₁₂-alkyl nitrates show the lowest concentrations in the trade wind region (3.5 pptv). Higher concentrations in the west wind belt (11.1 pptv) reveal the influence of the South American continent as the source for the alkyl nitrates after long range transport. The concentrations of alkyl nitrates increase in proximity to South America. Measurements of long chain alkyl nitrates in rural air near the city of Ulm (Germany) are given for comparison. In addition, pattern analysis of long chain alkyl nitrates reveal this complex mixture of new compounds to be useful as trace indicators to distinguish continental and marine air masses. Despite the lower photochemical formation yields of primary n-alkyl nitrates compared to secondary n-alkyl nitrates, the primary n-alkyl nitrates are relatively increased in marine air. The reason for this finding cannot be explained so far, but the correlation of secondary/primary n-alkyl nitrates shows a significant differentiation of air samples with continental or marine character.
Determination of C<inf>1</inf>-C<inf>5</inf> alkyl nitrates in rain, snow, white frost, lake, and tap water by a combined codistillation head-space gas chromatography technique. Determination of Henry's law constants by head-space GC
1998, Chemosphere
Alkyl nitrates with a chain length up to five carbon atoms have been determined in snow, white frost, and surface water. The samples were taken in the vicinity of Ulm, Germany, a region in central Europe. The determination of C₁C₅-alkyl nitrates in water samples was achieved with a new water codistillation enrichment technique directly coupled with on-column head-space gas chromatography. The concentrations of the short chain alkyl nitrates in the different forms of wet deposition range from 89 ng L⁻¹ for 1-propyl nitrate down to 35 ng L⁻¹ for 1-pentyl nitrate. C₁C₅-alkyl nitrates in wet depositions were also directly determined by static head-space gas chromatography.
Gas-water partition coefficients K_GW (Henry's law constant H) were determined by head-space gas chromatography and secondly by calculating the Henry's law constant by the ratio of vapor pressure to water solubility. The gas-water partition constants (dimensionless) or Henry's law constants range from K_GW = 0.038 (H = 93 Pa m³ mol⁻¹) for 1-propyl nitrate up to KGw = 0.122 (H = 302 Pa m³ mol⁻¹) for 2-pentyl nitrate.
Methods, fluxes and sources of gas phase alkyl nitrates in the coastal air
2014, Environmental Monitoring and Assessment
Ocean-atmosphere biogeochemical interactions: A two-way coupling under 'SOLAS'
2004, Indian Journal of Marine Sciences

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The measurement of C3-C5 alkyl nitrates at a coastal sampling site in the southern hemisphere

Abstract

Atmos. Environ.

Atmos. Environ.

Atmos. Environ.

Chemical reactions and transport of alkanes and their products in the troposphere

J. Atmos. Chem.

Organic nitrates in remote marine environments: evidence for long range transport

Geophys. Res. Lett.

The transformation of nitrogen oxides in the polluted troposphere

Tellus

Alkyl nitrate formation from NOx-air photooxidations of C2C8 n-alkanes

J. Phys. Chem.

Effects of temperature and pressure on alkyl nitrate yields in the NOx photooxidations of n-pentane and n-heptane

J. Phys. Chem.

Evidence for ≥C3 alkyl nitrates in rural and remote atmospheres

Nature

The measurement of C₃-C₅ alkyl nitrates at a coastal sampling site in the southern hemisphere

Alkyl nitrate formation from NO_x-air photooxidations of C₂C₈ n-alkanes

Effects of temperature and pressure on alkyl nitrate yields in the NO_x photooxidations of n-pentane and n-heptane

Evidence for ≥C₃ alkyl nitrates in rural and remote atmospheres