Selective incorporation of dissolved organic matter (DOM) during sea ice formation

This study investigated the incorporation of DOM from seawater into >2 day-old sea ice in tanks filled with seawater alone or amended with DOM extracted from the microalga, Chlorella vulgaris. Optical properties, including chromophoric DOM (CDOM) absorption and fluorescence, as well as concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved carbohydrates (dCHOs) and dissolved uronic acids (dUAs) were measured. Enrichment factors (EFs), calculated from salinity-normalized concentrations of DOM in bulk ice, brine and frost flowers relative to under-ice water, were generally >1. The enrichment factors varied for different DOM fractions: EFs were the lowest for humic-like DOM (1.0–1.39) and highest for amino acid-like DOM (1.10–3.94). Enrichment was generally highest in frost flowers with there being less enrichment in bulk ice and brine. Size exclusion chromatography indicated that there was a shift towards smaller molecules in the molecular size distribution of DOM in the samples collected from newly formed ice compared to seawater. Spectral slope coefficients did not reveal any consistent differences between seawater and ice samples. We conclude that DOM is incorporated to sea ice relatively more than inorganic solutes during initial formation of sea ice and the degree of the enrichment depends on the chemical composition of DO

Biomonitoring for arsenic, toxic and essential metals in single hair strands by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been developed as reliable analytical technique for the quantitation of metal distributions at micrometre resolution. In this work a novel microanalytical strategy for biomonitoring of arsenic, toxic and essential metals in single hair strands is proposed. Two different calibration strategies in LA-ICP-MS were developed using either certified hair standard reference material (IAEA 086) or prepared matrix-matched laboratory hair standards doped with analytes of interest at defined concentration. Powdered hair standards and human hair strands mounted on a sticky tape in the LA chamber were analyzed under the same experimental conditions by an optimized LA-ICP-MS technique. The use of hair powder standard allows calibration curves to be obtained by plotting the analyte ion (M+) intensity normalized to S-34(+) (the ratio M+/S-34(+)) as a function of the concentration determined by ICP-MS of acidic digests. The linear correlation coefficients (R) of calibration curves for analytes As, Ba, Cd, Ce, Co, Cr, Cu, Fe, Ga, Hg, Mg, Mo, Ni, Pb, Rb, Sr, Ti and U were typically between 0.985 and 0.999. The limit of detection (LOD) was 0.6 mu g g(-1) for As and ranged from 0.3 to 7.8 mu g g(-1) for the other analytes. Distinct elemental exposition time profiles were observed in hair samples from five volunteers. (C) 2011 Elsevier B.V. All rights reserved