Kim Holmén

Modelling the impacts of a nitrogen pollution event on the biogeochemistry of an Arctic glacier.

Abstract A highly polluted rain event deposited ammonium and nitrate on Midtre Lovénbreen, Svalbard, European High Arctic, during the melt season in June 1999. Quasi-daily sampling of glacial runoff showed elevated ion concentrations of both ammonium (NH4 +) and nitrate (NO3 −), collectively dissolved inorganic nitrogen (DIN) in the two supraglacial meltwater flows, but only elevated NO3 − in the subglacial outburst. Time-series analysis and flow-chemistry modelling showed that supra- and subglacial assimilation of NH4 + were major impacts of this deposition event. Supraglacial assimilation likely occurred while the pollution-event DIN resided within a/the supraglacial slush layer (estimated DIN half-life 40–50 hours, with the lifetime of NO3 − exceeding that of NH4 + by 30%). Potentially, such processes could affect preservation of DIN in melt-influenced ice cores. Subglacial routing of event DIN and its multi-day storage beneath the glacier also enabled significant assimilation of NH4 + to occur here (60% of input), which may have been either released as particulate N later during the melt season, or stored until the following year. Our results complement existing mass-balance approaches to the study of glacial biogeochemistry, show how modelling can enable time-resolved interpretation of process dynamics within the biologically active melt season, and highlight the importance of episodic polluted precipitation events as DIN inputs to Arctic glacial ecosystems.

A microwave radiometer for the remote sensing of nitric oxide and ozone in the middle atmosphere

Nitric oxide, which reacts catalytically to destroy ozone, can be produced in great abundance in the middle atmosphere during energetic particle precipitation triggered by solar storms. During the Antarctic winter, the strong polar vortex can rapidly transport nitric oxide downward, and this process has been identified as a mechanism that can link ozone recovery in the upper stratosphere with solar activity. As part of the Sun Earth Connection programme at the British Antarctic Survey (BAS), a new, state-of-the-art microwave radiometer is being developed in collaboration with the Max-Planck Institute (MPI) and the Norwegian Polar Institute (NPI) to simultaneously measure profiles of ozone and nitric oxide between 30 and 80 km deep within the Antarctic polar vortex. Operating in the 250 GHz spectral region, the semi-autonomous instrument will be coupled to moderate- and high-resolution chirp spectrometers to provide simultaneous spectra of the nitric oxide and ozone. In addition, a second local oscillator will be used to periodically examine carbon monoxide at 230.538 GHz to infer the vertical descent rate within the Antarctic vortex. Here, we present the science rationale for the observation programme as well as the instrument specifications, design and performance.

Seasonal variation and source areas of airborne lead-210 at Ny-Ålesund in the High Arctic

High-volume aerosol particle samples were collected onto glass-fibre filters at Mount Zeppelin Global Atmosphere Watch station, Ny-ÅAring;lesund, Svalbard, in 2001–05. The filters were assayed for lead-210 (210Pb) by measuring the alpha particles of its in-grown daughter nuclide polonium-210 (210Po). The observed 210Pb activity concentrations at Mount Zeppelin vary between <4 and 1060 μBq m-3, with an arithmetic mean of 130 μBq m-3 and a median of 74 μBq m-3. The lowest 210Pb activity concentrations are found during summer and the highest are found in winter. This variation is caused by seasonal differences in the mixing conditions of the troposphere, the level of precipitation and the speed of atmospheric chemistry induced by solar radiation. The performed source area analysis, which is based on air mass back trajectories, indicated that in summer, 210Pb can be used as a tracer for air masses coming into contact with land areas within the past 5 days. In winter this cannot be performed because of the accumulation of 210Pb-carrying aerosol particles into the Arctic atmosphere during the Arctic night. But even in winter a low 210Pb activity concentration indicates that the associated air mass has had little if any contact with land areas.

INFLUENCE OF LOCAL AND REGIONAL AIR POLLUTION ON ATMOSPHERIC MEASUREMENTS IN NY-ÅLESUND

The Zeppelin observatory is a research station near the village Ny-Ålesund in Svalbard. The facility delivers data to international projects devoted to high data quality monitoring of the background air pollution in the Arctic. An approach for quantifying the influence of local and regional pollution on measurements that may be misinterpreted as long-range transported one, is presented here. The hourly gas and aerosol data measured in Ny-Ålesund and at the Zeppelin station, respectively, have been analysed along with the meteorological data from Ny-Ålesund, Zeppelin station and Longyearbyen (south-east of Ny-Ålesund). Seasonal fluctuation of the average measured values of SO2 and NOx has been observed. Three main wind directions coincided with the peak concentration of SO2 and NOx. The NW-N flow may bring local pollution from ship traffic and diesel power plant as well as biogenic SO2 from the oxidation of DMS. The monthly average number of particles with diameter characteristic for ship plume (50–100 nm), was elevated for the hours when ships have been registered in the local call list. The number concentration of particles with diameter 200 nm, typical for Arctic haze events, and concentration of non-sea salt sulphate rise during springtime. The FLEXTRA-trajectory analysis indicated that most pollution brought by E-SE and SW flows may be of long-range and/or regional origin. Events with these flow directions need to be interpreted with caution.

Effect of seasonal mesoscale and microscale meteorological conditions in Ny-Ålesund on results of monitoring of long-range transported pollution

ABSTRACT Ny-Ålesund is an international research settlement where the thermodynamics and chemical composition of the air are monitored. The present work investigates the effects of micrometeorological conditions, mesoscale dynamics and local air pollution on the data collected at two different locations around the village. Daily filter measurements of sulphur dioxide and non-sea salt sulphate from the temporary Ny-Ålesund station and permanent Zeppelin mountain station have been analysed along with meteorological data. The influence of different factors representing micrometeorological phenomena and local pollution from ships has been statistically investigated. Seasonal variation of the correlation between the data from Ny-Ålesund and Zeppelin stations is revealed, and the seasonal dependence of the relative contribution of different factors has been analysed. The median concentrations of SO42- measured in Ny-Ålesund increased significantly on days with temperature inversions in winter. In spring, concentrations of SO2 and SO42- were higher than normal at both stations on days with temperature inversions, but lower on days with strong humidity inversions. In summer, local ship traffic affects the SO2 data set from Ny-Ålesund, while no statistically significant influence on the Zeppelin data set has been observed. The pollution from ships has an effect on SO42- values at both stations; however, the concentrations in Ny-Ålesund were higher when local pollution accumulated close to the ground in days with strong humidity inversions.