Michael Kriews

Arctic Study of Tropospheric Aerosol and Radiation (ASTAR) 2000: Arctic haze case study

The ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) campaign ran from 12 March until 25 April 2000 with extensive flight operations in the vicinity of Svalbard (Norway) from Longyearbyen airport (78.25°N, 15.49°E). It was a joint Japanese (NIPR Tokyo)–German (AWI Bremerhaven/Potsdam) airborne measurement campaign using AWI aircraft POLAR 4 (Dornier 228-101). Simultaneous ground-based measurements were done at the international research site Ny-Ålesund (78.95°N, 11.93°E) in Svalbard, at the German Koldewey station, at the Japanese Rabben station and at the Scandinavian station at Zeppelin Mountain (475 m above sea level). During the campaign 19 profiles of various aerosol properties were measured. In general, the Arctic spring aerosol in the vicinity of Svalbard had significant temporal and vertical variability. A strong haze event occurred between 21 and 25 March in which the optical depth from ground-based observation was 0.18, which was significantly greater than the background value of 0.06. Airborne measurements on 23 March during this haze event showed a high aerosol layer with an extinction coefficient of 0.03 km−1 or more up to 3 km and a scattering coefficient from 0.02 in the same altitude range. From the chemical analyses of airborne measurements, sulfate, soot and sea salt particles were dominant, and there was a high mixing ratio of external soot particles in some layers during the haze event, whereas internal mixing of soot in sulfate was noticeable in some layers for the background condition. We argue that the high aerosol loading is due to direct transport from anthropogenic source regions. In this paper we focus on the course of the haze event in detail through analyses of the airborne and ground-based results.

Seasonal variability of crustal and marine trace elements in the aerosol at Neumayer station, Antarctica

Atmospheric trace element concentrations were measured from March 1999 to December 2003 at the Air Chemistry Observatory of the German Antarctic station Neumayer, by inductively coupled plasma–quadrupol mass spectrometry (ICP–QMS) and ion chromatography (IC). This continuous five-year long record derived from weekly aerosol sampling revealed a distinct seasonal summer maximum for elements linked with mineral dust entry (Al, La, Ce, Nd) and a winter maximum for the mostly sea salt derived elements Li, Na, K, Mg, Ca and Sr. The relative seasonal amplitude was around 1.7 and 1.4 for mineral dust (La) and sea salt aerosol (Na), respectively. On average, a significant deviation regarding mean ocean water composition was apparent for Li, Mg and Sr, which could hardly be explained by mirabilite precipitation on freshly formed sea ice. In addition, we observed all over the year, a not clarified high variability of element ratios Li/Na, K/Na, Mg/Na, Ca/Na and Sr/Na. We found an intriguing co-variation of Se concentrations with biogenic sulphur aerosols (methane sulphonate and non-sea salt sulphate), indicating a dominant marine biogenic source for this element, linked with the marine biogenic sulphur source.

Tissue specificity in nickel uptake and induction of oxidative stress in kidney and spleen of goldfish Carassius auratus, exposed to waterborne nickel

Toxic and carcinogenic effects of nickel compounds are suggested to result from nickel-mediated oxidative damage to macromolecules and/or inhibition of cellular antioxidant defenses. We investigated the effects of waterborne Ni(2+) (10, 25 and 50 mg/L) on the blood and blood-producing tissues (kidney and spleen) of goldfish to identify relationships between Ni accumulation and oxidative stress. Whereas the main hematological parameters (total hemoglobin and hematocrit) were unaffected, Ni(2+) exposure had substantial influence on goldfish immune system, causing lymphopenia. Ni accumulation increased renal iron content (by 49-78%) and resulted in elevated lipid peroxide (by 29%) and protein carbonyl content (by 274-278%), accompanied by suppression of the activities of superoxide dismutase (by 50-53%), glutathione peroxidase (15-45%), glutathione reductase (31-37%) and glucose-6-phosphate dehydrogenase (20-44%), indicating development of oxidative stress in kidney. In contrast to kidney, in spleen the activation of glutathione peroxidase (by 34-118%), glutathione-S-transferase (by 41-216%) and glutathione reductase (by 47%), as well as constant levels of low molecular mass thiols and metals together with enhanced activity of glucose-6-phosphate dehydrogenase (by 41-94%) speaks for a powerful antioxidant potential that counteracts Ni-induced ROS production. Further, as Ni accumulation in this organ was negligible, Ni-toxicity in spleen may be minimized by efficient exclusion of this otherwise toxic metal.

Differences in heavy metal concentrations and in the response of the antioxidant system to hypoxia and air exposure in the Antarctic limpet Nacella concinna.

During the austral spring and summer months, the Antarctic limpet Nacella concinna colonizes intertidal environments in the Western Antarctica Peninsula region. The species is divided into a permanently sub-littoral and a seasonally intertidal, migratory subpopulation. We investigate the physiological differentiation between the two limpet groups to identify cellular and molecular changes that accompany adaptation of stenothermal Antarctic invertebrates to life under more stressful intertidal habitat conditions. A major difference between the two groups is the significantly higher concentrations of heavy metals (Fe, Al, Zn) from ingested sediments in sub-littoral limpet digestive glands (DG), associated with higher rates of reactive oxygen species (ROS) formation in this organ. ROS formation is accompanied by significantly higher SOD activity in sub-littoral limpet DG. These high SOD activities are, however, not conserved during either air exposure or hypoxic stress exposure of the sub-littoral limpets, when ROS production is slowed due to the absence of oxygen. The intertidal animals maintain higher levels of SOD and also conserve catalase activity at higher levels during hypoxia or air exposure compared to sub-littoral individuals under the same exposure conditions. More oxidized redox potential in gills and foot muscle and higher antioxidant enzyme activities in gills indicate that intertidal limpets maintain more oxygenated tissues during air exposure, in keeping with shell-lifting for oxygen up-take by the gills of intertidal limpets which migrate up the shore in the spring and down in the autumn. An increase of the redox ratio (GSSG/GSH) and accumulation of the lipid oxidation derived malonedialdehyde in intertidal limpet foot muscle during 12h of exposure to air shows that indeed this tissue becomes more oxidized before the limpets eventually contract their shells tightly to minimize water loss and eventually become anaerobic. Intertidal limpets obviously avoid early onset of anaerobic energy production seen in their sub-littoral congeners when exposed to air and are still able to maintain tissue redox ratio balance when exposed to air.

Oxygen-dependent niche formation of a pyrite-dependent acidophilic consortium built by archaea and bacteria

Biofilms can provide a number of different ecological niches for microorganisms. Here, a multispecies biofilm was studied in which pyrite-oxidizing microbes are the primary producers. Its stability allowed not only detailed fluorescence in situ hybridization (FISH)-based characterization of the microbial population in different areas of the biofilm but also to integrate these results with oxygen and pH microsensor measurements conducted before. The O2 concentration declined rapidly from the outside to the inside of the biofilm. Hence, part of the population lives under microoxic or anoxic conditions. Leptospirillum ferrooxidans strains dominate the microbial population but are only located in the oxic periphery of the snottite structure. Interestingly, archaea were identified only in the anoxic parts of the biofilm. The archaeal community consists mainly of so far uncultured Thermoplasmatales as well as novel ARMAN (Archaeal Richmond Mine Acidophilic Nanoorganism) species. Inductively coupled plasma analysis and X-ray absorption near edge structure spectra provide further insight in the biofilm characteristics but revealed no other major factors than oxygen affecting the distribution of bacteria and archaea. In addition to catalyzed reporter deposition FISH and oxygen microsensor measurements, microautoradiographic FISH was used to identify areas in which active CO2 fixation takes place. Leptospirilla as well as acidithiobacilli were identified as primary producers. Fixation of gaseous CO2 seems to proceed only in the outer rim of the snottite. Archaea inhabiting the snottite core do not seem to contribute to the primary production. This work gives insight in the ecological niches of acidophilic microorganisms and their role in a consortium. The data provided the basis for the enrichment of uncultured archaea.

Interpretation of Arctic aerosol properties using cluster analysis applied to observations in the Svalbard area

Atmospheric aerosols play an important role in global climate change, directly through radiative forcing and indirectlythrough their effect on cloud properties. Numerous measurements have been performed in the last three decades inorder to characterize polar aerosols. Information about aerosol characteristics is needed to calculate induced changes inthe Earth’s heat balance. However, this forcing is highly variable in space and time. Accurate quantification of forcingby aerosols will require combined efforts, assimilating information from different sources such as satellite, aircraft andsurface-based observations. Adding to the complexity of the problem is that the measurements themselves are oftennot directly comparable as they vary in spatial/temporal resolution and in the basic properties of the aerosol that theymeasure. Therefore it is desirable to close the gap between the differences in temporal and spatial resolution and coverageamong the observational approaches. In order to keep the entire information content and to treat aerosol variability ina consistent and manageable way an approach has to be achieved which enables one to combine these data. This studypresents one possibility for linking together a complex Arctic aerosol data set in terms of parameters, timescale and placeof measurement as well as meteorological parameters. A cluster analysis was applied as a pattern recognition technique.The data set is classified in clusters and expressed in terms of mean statistical values, which represent the entire databaseand its variation. For this study, different time-series of microphysical, optical and chemical aerosol parameters aswell as meteorological parameters were analysed. The database was obtained during an extensive aerosol measurementcampaign, the ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) field campaign, with coordinatedsimultaneous ground-based and airborne measurements in the vicinity of Spitsbergen (Svalbard). Furthermore, longtermmeasurements at two ground-based sites situated at different altitudes were incorporated into the analysis. Theapproach presented in this study allows the necessary linking of routine long-term measurements with short-termextensive observations. It also involves integration of intermittent vertical aerosol profile measurements. This is usefulfor many applications, especially in climate research where the required data coverage is large.

Rare Earth Elements determined in Antarctic ice by Inductively Coupled Plasma - Time of Flight, Quadrupole and Sector Field-Mass Spectrometry: an inter-comparison study

Inductively coupled plasma mass spectrometry (ICP-MS) is a suitable tool for multi-element analysis at low concentration levels. Rare earth element (REE) determinations in standard reference materials and small volumes of molten ice core samples from Antarctica have been performed with an ICP-time of flight-MS (ICP-TOF-MS) system. Recovery rates for REE in e.g. SPS-SW1 amounted to approximately 103%, and the relative standard deviations were 3.4% for replicate analysis at REE concentrations in the lower ngL(-1) range. Analyses of REE concentrations in Antarctic ice core samples showed that the ICP-TOF-MS technique meets the demands of restricted sample mass. The data obtained are in good agreement with ICP-Quadrupole-MS (ICP-Q-MS) and ICP-Sector Field-MS (ICP-SF-MS) results. The ICP-TOF-MS system determines accurately and precisely REE concentrations exceeding 5ngL(-1) while between 0.5 and 5ngL(-1) accuracy and precision are element dependent.

Zur Probennahme in die Arktis

Die Wissenschaft fuhrt den Forscher manchmal an die unwirtlichsten Orte: Heftige Schneesturme, Dunkelheit rund um die Uhr und −30°C. Fur die Forscher vom Alfred-Wegener-Institut fur Polar-und Meeresforschung, Bremerhaven, ist die Entnahme und Vorbereitung von Proben unter diesen Bedingungen nichts Ungewohnliches-hier der Bericht einer Expedition im Fruhjahr 2000.