Salinity and SO4 and Br enrichment of seawater and frost flowers near Barrow, Alaska

Frost flowers have been proposed to be the major source of sea-salt aerosol to the atmosphere during polar winter and a source of reactive bromine during polar springtime. However little is known about their bulk chemical composition or microstructure, two important factors that may affect their ability to produce aerosols and provide chemically reactive surfaces for exchange with the atmosphere. Therefore, we chemically analyzed 28 samples of frost flowers and parts of frost flowers collected from sea ice off of northern Alaska. Our results support the proposed mechanism for frost flower growth that suggests water vapor deposition forms an ice skeleton that wicks brine present on newly grown sea ice. We measured a high variability in sulfate enrichment factors (with respect to chloride) in frost flowers and seawater from the vicinity of freezing sea ice. The variability in sulfate indicates that mirabilite precipitation (Na2SO4 x 10 H2O) occurs during frost flower growth. Brine wicked up by frost flowers is typically sulfate depleted, in agreement with the theory that frost flowers are related to sulfate-depleted aerosol observed in Antarctica. The bromide enrichment factors we measured in frost flowers are within error of seawater composition, constraining the direct reactive losses of bromide from frost flowers. We combined the chemical composition measurements with temperature observations to create a conceptual model of possible scenarios for frost flower microstructure development.

(Table 1) Micro-inclusion counts and ion concentrations in the five GRIP ice-core sections

We provide the first direct evidence that a number of water-soluble compounds, in particular calcium sulfate (CaSO4 2H2O) and calcium carbonate (CaCO3), are present as solid, micron-sized inclusions within the Greenland GRIP ice core. The compounds are detected by two independent methods: micro-Raman spectroscopy of a solid ice sample, and energy-dispersive X-ray spectroscopy of individual inclusions remaining after sublimation. CaSO4 2H2O is found in abundance throughout the Holocene and the last glacial period, while CaCO3 exists mainly in the glacial period ice. We also present size and spatial distributions of the micro-inclusions. These results suggest that water-soluble aerosols in the GRIP ice core are dependable proxies for past atmospheric conditions.

Aerosol total mass concentration and optical depth during IPY 2007-2008 at Maitri and Larsemann Hills Station

The properties of background aerosols and their dependence on meteorological, geographical and human influence are examined using measured spectral aerosol optical depth (AOD), total mass concentration (Mt) and derived number size distribution (NSD) over two distinct coastal locations of Antarctica; Maitri (70°S, 12°E, 123 m m.s.l.) and Larsemann Hills (LH; 69°S, 77°E, 48 m m.s.l.) during southern hemispheric summer of 2007-2008 as a part of the 27th Indian Scientific Expedition to Antarctica (ISEA) during International Polar Year (IPY). Our investigations showed comparable values for the mean columnar AOD at 500 nm over Maitri (0.034±0.005) and LH (0.032±0.006) indicating good spatial homogeneity in the columnar aerosol properties over the coastal Antarctica. Estimation of Angstrom exponent a showed accumulation mode dominance at Maitri (alpha ~1.2±0.3) and coarse mode dominance at LH (0.7±0.2). On the other hand, mass concentration (M(T)) of ambient aerosols showed relatively high values (~8.25±2.87 µg/m**3) at Maitri in comparison to LH (6.03±1.33 µg/m**3).

Density and stable oxygen isotope profiles of four snow pits from Berkner Island, Filchner-Ronne Ice Shelf, Antarctica

The ice cap on Berkner Island is grounded on bedrock within the Filchner-Ronne Ice Shelf and is, therefore, expected to be a well-suited place to retrieve long-term ice-core records reflecting the environmental situation of the Weddell Sea region. Shallow firn cores were drilled to 11 m at the two main summits of Berkner Island and analysed in high depth resolution for electrical d.c. conductivity (ECM), stable isotopes, chloride, sulphate, nitrate and methane-sulphonate (MSA). From the annual layering of dD and non-sea-salt (nss) sulphate, a mean annual snow accumulation of 26.6 cm water at the north dome and 17.4 cm water at the south dome are obtained. As a result of ineffective wind scouring indicated by a relatively low near-surface snow density, regular annual cycles are found for all species at least in the upper 4-5 m. Post depositional changes are responsible for a substantial decrease of the seasonal dD and nitrate amplitude as well as for considerable migration of the MSA signal operating below a depth of 3-4 m. The mean chemical and isotopic firn properties at the south dome correspond to the situation on the Filchner-Ronne Ice shelf at a comparable distance to the coast, whereas the north dome is found to be more influenced by maritime air masses. Persistent high sea-salt levels in winter snow at Berkner Island heavily obscure the determination of nss sulphate probably due to sulphate fractionation in the Antartic sea-salt aerosols. Estimated time-scales predict ages at 400 m depth to be ca. 2000 years for the north and ca. 3000 years for the south dome. Pleistocene ice is expected in the bottom 200 and 300 m, respectively.

Gel particles in the sea-surface microlayer during an experimental study

Since the early 80's, the sea-surface microlayer (SML) has been hypothesized as being a gelatinous film. Recent studies have confirmed this characteristic, which confers properties that mediate mass and energy fluxes between ocean and atmosphere, including the emission of primary organic aerosols from marine systems. We investigated SML thickness and composition in five replicate indoor experiments between September and December 2010. During each experiment, the SML and underlying seawater were sampled from four seawater tanks: one served as control, and three were inoculated with Thalassiosira weissflogii grown in chemostats at 180, 380 and 780 ppm pCO2. We examined organic material enrichment factors in each tank, paying particular attention to gel particles accumulation such as polysaccharidic Transparent Exopolymer Particles (TEP) and the proteinaceous Coomassie Stainable Particles (CSP). While previous studies have observed carbohydrates and TEP enrichment in the microlayer, little is yet known about proteinaceous gel particles in the SML. Our experiments show that CSP dominate the gelatinous composition of the SML. We believe that the enrichment in CSP points to the importance of bacterial activity in the microlayer. Bacteria may play a pivotal role in mediating processes at the air-sea interface thanks to their exudates and protein content that can be released through cell disruption.

Aerosol concentrations measured along the track of METEOR cruise M16

During the third part of the Atlantic Expedition 1969 from 10° S to 60° N along 30° W, measurements of the complete size distribution of atmospheric aeosols over the whole size range from about 10**-7 to 10**-2 cm radius were made. This was possibe by the simultaneous operation of different methods which are critically discussed. The results obtained are the first of its kind and are of general interest despite some methodical shortcomings. North of the equator the ship passed through air masses of west African origin and the influence of Sahara dust on the Marine aerosols could be documented in a unique way. The Sahara dust component was restricted to the size range of 10**-5 to 10**-3 radius. Throughout the voyage particles up to 10**-2 radius were always found to be present, similar to findings over continents. Of special interest is the observation that the size distribution extends to very small particles, suggesting continuous aerosol production over the ocean.

Superoxide decay rates during METEOR cruise M83/1

Superoxide is an important transient reactive oxygen species (ROS) in the ocean formed as an intermediate in the redox transformation of oxygen (O2) into hydrogen peroxide (H2O2) and vice versa. This highly reactive and very short-lived radical anion can be produced both via photochemical and biological processes in the ocean. In this paper we examine the decomposition rate of O2- throughout the water column, using new data collected in the Eastern Tropical North Atlantic (ETNA) Ocean. For this approach we applied a semi factorial experimental design, to identify and quantify the pathways of the major identified sinks in the ocean. In this work we occupied 6 stations, 2 on the West African continental shelf and 4 open ocean stations, including the CVOO time series site adjacent to Cape Verde. Our results indicate that in the surface ocean, impacted by Saharan aerosols and sediment resuspension, the main decay pathways for superoxide is via reactions with Mn(||) and organic matter.

Lignin and chemical elements in the surface layer of bottom sediments from the Kandalaksha Bay of the White Sea

Chemical composition of the upper layer of sediments (0-1 cm) in the Kolvits and Knazhaya inlets, and also in the deep-water part of the Kandalaksha Bay is considered. It is shown that silts are richer in Fe, TOC, and heavy metals, than sands. The highest concentration of these elements is found in sediments under mixing zones of riverine and sea waters. Correlations of P, Zn, Cd, and Cu with iron are high, and correlations of Pb and Cu with organic carbon are also high. Very high concentration of Pb in the Kandalaksha Bay indicate technogenic pollution of sediments. Lignin makes significant contribution to formation of organic matter in the sediments. Composition of lignin in bottom sediments of the Kandalaksha Bay is defined by composition of lignin in soils and aerosols. Vanillin and syringyl structures prevail in molecular composition of lignin in bottom sediments. Their sources are coniferous vegetations, soils, and mosses. Ratios of certain types of phenol compounds indicate pollution of the upper layer of sediments by technogenic lignin. Lead and copper correlate well with this technogenic lignin.