Lower tropospheric measurements of halogens, nitrates, and sulphur oxides during Polar Sunrise Experiment 1992

Abstract

During the international Polar Sunrise Experiment 1992 at Alert, Northwest Territories, Canada, in the high Arctic, atmospheric chemistry measurements were conducted from January to April to investigate lower tropospheric ozone depletion chemistry. A series of filter‐based measurements involving a denuder and multistage filter holders were made to characterize the particulate and gaseous fraction of lower tropospheric SOx., Br, Cl, I, and NO3− in relation to O3 depletion events. Bromine compounds were the only ones of all those measured to show correlations with ozone depletion. All three components of total Br (particulate inorganic, gaseous inorganic, and gaseous organic) increased during O3 depletion events. Temporal trends in halogens between the dark of January and the complete light of April were in some cases evident. Largely, as a result of more frequently occurring O3 depletion‐related episodes toward April, average concentrations of Br components tended to increase. The sum of inorganic particulate and gaseous Br increased from about 10 to 20 parts per trillion by volume (pptv) and organic gaseous Br increased from 25 to 40 pptv. Total inorganic I concentrations increased from about 0.3 pptv in early March to 1.0 pptv in late April. There was no systematic trend in total inorganic (gas plus particle) Cl with concentrations averaging approximately 40 pptv, while organic Cl trapped on charcoal was much more abundant. SOx concentrations averaged about 1200 pptv, decreasing from a maximum of 6000 pptv in January to 800 pptv in April and were well correlated with anthropogenic V. The fraction of SOx oxidized to SO4= increased progressively from a low of 20 to 30% in January to greater than 80% in April. SO4= concentrations increased from 500 pptv in January/February to 1000 pptv in March and dropped to 700 pptv in April. Inorganic NO3− showed no systematic variation throughout the period. It averaged 50 pptv, which is much less than peroxyacetyl nitrate (PAN) (150 to 600 pptv), and it was predominantly in particles. Judging from denuder observations, a filter combination of Teflon followed by two KOH filters can provide useful estimates of inorganic particulate Br− and NO3− as well as of inorganic gaseous Br−. Inorganic gaseous NO3− measurements from KOH and nylon filters suffer interferences from collection of PAN.

The effects of the coastal environment on the atmospheric mercury cycle

“…The fine and coarse samples were collected at flow rates of 15 L min À1 and 2 L min À1 , respectively. One fine sample was collected on prebaked quartz filters for elemental carbon (EC) and organic carbon (OC) analysis using thermal optical reflectance analysis [Birch and Cary, 1996]. The second fine and the coarse sample were collected onto Teflon filters for gravimetric determination of particulate mass.…”

“…Extensive measurements of Br 2 and Br . have not been made, so concentrations were estimated to be at the lower end of those measured in the Arctic [Impey et al, 1997;Barrie et al, 1994]. Concentrations of OH .…”

Levels and pattern of volatile organic nitrates and halocarbons in the air at Neumayer Station (70°S), Antarctic

“…The results of the light induced photochemistry and oxidation chemistry of hydrocarbons in air depend on the levels of the reaction of starting radicals such as OH,or NO 3 , and on the levels of trace gases like odd-nitrogen NO y , (particularly NO x (NO þ NO 2 ) as main part), ozone, and organosulfur compounds (Atlas et al, 1992a,b;Carroll et al, 1992;Barrie et al, 1994;Kondo et al, 1997;Platt Chemosphere 48 (2002) [981][982][983][984][985][986][987][988][989][990][991][992] www.elsevier.com/locate/chemosphere and Le Bras, 1997). As a result of combustion emissions, levels of NO x greatly enhanced over those in the background troposphere can be found in urban and densely inhabited continental areas.…”

Extending the Community Multiscale Air Quality (CMAQ) modeling system to hemispheric scales: overview of process considerations and initial applications

“…Enhancements to free-tropospheric SO 2− 4 measurements over northwest North America have been attributed to Asian sources (e.g., Andreae et al, 1988;Barrie et al, 1994). Increasing SO 2 emissions in Asia could potentially increase the amount of SO 2− 4 imported to North America and impact local efforts to reduce regional haze and improve visibility in national parks.…”