In situ measurements of bromine oxide at two high‐latitude boundary layer sites: Implications of variability

Abstract

[1] Bromine oxide (BrO) was measured in situ during the Arctic Tropospheric Ozone Chemistry (ARCTOC) '96 campaign in Ny Å lesund, Spitsbergen (April-May 1996), and during the Alert 2000 Polar Sunrise Experiment in Alert, Nunavut, Canada (April-May 2000). Measurements were made in near-surface air during low-ozone events in early May at both sites. The average of the in situ concentrations of BrO at Ny Å lesund is consistent with the path average of near-simultaneous long-path differential optical absorption spectroscopy measurements, but there is considerable scatter in a point-by-point comparison. The differences between these observations are consistent with a strong surface influence on reactive bromine. We see similar variability of the in situ measurements at Alert, which reflects the real variability of both surface sources and sinks. The fluctuations of BrO abundances are used to assess the expected loss rates and associated lifetimes of ozone during depletion events. We show that ozone loss will be underpredicted by any temporal or spatial average of BrO.

An overview of snow photochemistry: evidence, mechanisms and impacts

“…These measurements provided the first direct evidence of a snowpack source of reactive molecular halogens potentially responsible for the observed tropospheric ozone depletion phenomenon. Comparison of BrO concentrations measured with an in-situ chemical conversion/resonance fluorescence technique and a DOAS system showed a strong vertical gradient of BrO at Alert (Avallone et al, 2003) again pointing to a strong influence from the snowpack. Measurements 1 m and 0.25 m above the snow showed up to 20 pptv of BrO hinting at a possible direct impact of the snowpack on BrO mixing ratios.…”

“…This reversible deposition of H 2 O 2 has been described with a physically based atmosphere-to-snow transfer model (McConnell et al, 1997a(McConnell et al, , b, 1998Hutterli et al, 2003). Concentrations in fresh snow reflect water-to-H 2 O 2 ratios in the cloud, whereas snow exposed sufficiently long to the atmosphere will approach a temperature-dependent partitioning equilibrium analogous to Henry's Law Bales et al, 1995). Levels of H 2 O 2 in fresh snow are altered by subsequent temperature-driven recycling between the snow and the air until the snow is buried below several 10 s of cm.…”

In situ detection of atomic and molecular iodine using Resonance and Off-Resonance Fluorescence by Lamp Excitation: ROFLEX

“…In particular, chlorine and bromine RF instruments were developed during the late 70's and the 80's of the last century for the detection of ClO and BrO in the context of the study of stratospheric halogen-catalysed ozone depletion (Anderson et al, 1977(Anderson et al, , 1980Brune et al, 1985Brune et al, , 1989Brune and Anderson, 1986;Avallone et al, 1995). A bromine oxide boundary layer instrument has also been reported (Avallone et al, 2003). Bale et al (2008) pioneered the detection of atmospheric atomic iodine by constructing, characterising and deploying in the field an instrument for the detection of atomic iodine using the RF technique.…”

“…Bale et al (2008) pioneered the detection of atmospheric atomic iodine by constructing, characterising and deploying in the field an instrument for the detection of atomic iodine using the RF technique. As a proxy for I 2 , Bale et al (2008) used the total photolabile iodine content of the sampled air, derived from the iodine atom signal observed after visible broad band photolysis of ambient iodine bearing molecules, which in a coastal environment with macroalgae emissions would correspond to a large extent to I 2 (McFiggans et al, 2004). A comparison of characteristics and performance of halogen RF instruments is shown in Table 1.…”

“…The most important development with respect to Bale et al (2008) is the inclusion of a second detector for collection of molecular iodine off-resonance fluorescence (ORF). This enables: (i) using a much simpler method for calibration of the fluorescence signal by I 2 absorption and photolysis, and (ii) measuring concurrently and directly a major iodine source (I 2 ) and active iodine atoms (I).…”