Chemical and meteorological influences on the lifetime of NO<sub>3</sub> at a semirural mountain site during "PARADE"

Abstract. Through measurements of NO2, O3, and NO3 during the PARADE campaign (PArticles and RAdicals, Diel observations of mEchanisms of oxidation) in the German Taunus mountains we derive nighttime, steady state lifetimes (τss) of NO3 and N2O5. During some nights, high NO3 (~ 200 pptv) and N2O5 (~ 1 ppbv) mixing ratios are associated with values of τss that exceeded one hour for NO3 and three hours for N2O5 near the ground. Such long boundary layer lifetimes for NO3 and N2O5 are usually only encountered in very clean/unreactive air masses whereas the PARADE measurement site is impacted by both biogenic emissions from the surrounding forest and anthropogenic emissions from the nearby urban…

Development of an active alkaline trap to determine acidic gas ratios in volcanic plumes: sampling technique and analytical methods

In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O<sub>3</sub>, IO, OIO and NO<sub>x</sub>

Abstract. Discrete in situ atmospheric measurements of molecular iodine (I2) were carried out at Mace Head and Mweenish Bay on the west coast of Ireland using diffusion denuders in combination with a gas chromatography-mass spectrometry (GC-MS) method. I2, IO and OIO were also measured by long-path differential optical absorption spectroscopy (LP-DOAS). The simultaneous denuder and LP-DOAS I2 measurements were well correlated (R2=0.80) but the denuder method recorded much higher concentrations. This can be attributed to the fact that the in situ measurements were made near to macroalgal sources of I2 in the intertidal zone, whereas the LP-DOAS technique provides distance-averaged mixing rat…

Abstracts of the 6th FECS Conference 1998 Lectures.

International audience

New insight into halogen release from experimental studies on BrO/Br ratios in volcanic plumes

Retrieval of absolute SO2 column amounts from scattered-light spectra: implications for the evaluation of data from automated DOAS networks

Scanning spectrometer networks using scattered solar radiation in the ultraviolet spectral region have become an increasingly important tool for monitoring volcanic sulfur dioxide (SO2) emissions. Often measured spectra are evaluated using the differential optical absorption spectroscopy (DOAS) technique. In order to obtain absolute column densities (CDs), the DOAS evaluation requires a Fraunhofer reference spectrum (FRS) that is free of absorption structures of the trace gas of interest. For measurements at volcanoes such a FRS can be readily obtained if the scan (i.e. series of measurements at different elevation angles) includes viewing directions where the plume is not seen. In this cas…

Chemical and meteorological influences on the lifetime of NO3 at a semi-rural mountain site during PARADE

Through measurements of NO2, O3 and NO3 during the PARADE campaign (PArticles and RAdicals, Diel observations of mEchanisms of oxidation) in the German Taunus mountains we derive nighttime steady-state lifetimes (τss) of NO3 and N2O5. During some nights, high NO3 (∼ 200 pptv) and N2O5 (∼ 1 ppbv) mixing ratios were associated with values of τss that exceeded 1 h for NO3 and 3 h for N2O5 near the ground. Such long boundary-layer lifetimes for NO3 and N2O5 are usually only encountered in very clean/unreactive air masses, whereas the PARADE measurement site is impacted by both biogenic emissions from the surrounding forest and anthropogenic emissions from the nearby urbanised/industrialised cen…

Bromine chemistry of volcanic plumes

Volcanic gas studies are an established tool for volcanic monitoring and enhance the understanding of volcanic manifestations. The central question of the project, which we will introduce here, is whether the ratio between bromine monoxide (BrO) to sulphur dioxide (SO2) can potentially serve as indicator for volcanic activity. Both species have the advantage that they can be remotely measured by Differential Optical Absorption Spectroscopy (DOAS) at safe distances from the emission source. To answer the question above, it is of great importance to link the measurements of halogen oxides to the total emission flux of individual halogen species and to understand the influences of meteorologic…

Experimental studies on BrO/Br ratios at Stromboli, Etna, Masaya, Gorely and Nyiragongo

Determination and comparison of acidic gas ratios at the Stromboli Volcano and Mount Etna obtained by various active alkaline traps

Observations of high concentrations of I2and IO in coastal air supporting iodine-oxide driven coastal new particle formation

[1] Theoretical studies have predicted that concentrations of gaseous I2 and IO of the order of 80–100 ppt and 40–50 ppt, respectively, are required in coastal air to account for photochemically-driven coastal new-particle formation events to occur. However, measurements reported to date (i.e., ∼20 ppt I2, ≤ 10 ppt IO) have not supported the required model predictions. Here, we present measurements of high concentrations of I2 and IO in N.E. Atlantic marine air on the west coast of Ireland. The maximum mixing ratios of daytime I2 and IO over the seaweed beds during low tide were 302 ppt and 35 ppt, respectively. The I2 distribution was rather inhomogeneous, even at the inter-tidal zone, but…