(Table 1) Concentrations of neutral and phenolic organohalogen compounds in adipose tissue, blood, brain and liver of polar bears (Ursus maritimus) from East Greenland

The tissue-specific composition of sum classes of brominated and chlorinated contaminants and metabolic/degradation byproducts was determined in adult male and female polar bears from East Greenland. Significantly (p < 0.05) higher concentrations of SUM-PCBs, various other organochlorines such as SUM-CHL, p,p'-DDE, SUM-CBz, SUM-HCHs, octachlorostyrene (OCS),SUM-mirex, dieldrin, the flame retardants SUM-PBDEs, and total-(R)-hexabromocyclododecane (HBCD), SUM-methylsulfonyl (MeSO2)-PCBs and 3-MeSO2-p,p'-DDE, were found in the adipose and liver tissues relative to whole blood and brain. In contrast, SUM-hydroxyl (OH)-PCB, 4-OH-heptachlorostyrene and SUM-OH-PBDE concentrations were significantly highest (p < 0.05) in whole blood, whereas the highest concentrations of SUM-OH-PBBs were found in the adipose tissue. Based on the total concentrations of all organohalogens in all three tissues and blood, the combined body burden was estimated to be 1.34 ± 0.12 g, where >91% of this amount was accounted for by the adipose tissue alone, followed by the liver, whole blood, and brain. These results show that factors such as protein association and lipid solubility appear to be differentially influencing the toxicokinetics, in terms of tissue composition/localization and burden, of organohalogen classes with respect to chemical structure and properties such as the type of halogenation (e.g., chlorination or bromination), and the presence or absence of additional phenyl group substituents (e.g., MeO and OH groups). The tissue- and blood-specific accumulation (or retention) among organohalogen classes indicates that exposure and any potential contaminant-mediated effects in these polar bears are likely tissue or blood specific.

Geochemistry of oceanic crust beneath Costa Rica

Resolving flow geometry in the mantle wedge is central to understanding the thermal and chemical structure of subduction zones, subducting plate dehydration, and melting that leads to arc volcanism, which can threaten large populations and alter climate through gas and particle emission. Here we show that isotope geochemistry and seismic velocity anisotropy provide strong evidence for trench-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua. This finding contradicts classical models, which predict trench-normal flow owing to the overlying wedge mantle being dragged downwards by the subducting plate. The isotopic signature of central Costa Rican volcanic rocks is not consistent with its derivation from the mantle wedge (Feigenson et al., 2004, doi:10.1029/2003GC000621; Herrstom et al., 1995, doi:10.1130/0091-7613(1995)023<0617:VILCAW>2.3.CO;2; Abratis and Woerner, 2001) or eroded fore-arc complexes (Goss and Kay, 2006, doi:10.1029/2005GC001163) but instead from seamounts of the Galapagos hotspot track on the subducting Cocos plate. This isotopic signature decreases continuously from central Costa Rica to northwestern Nicaragua. As the age of the isotopic signature beneath Costa Rica can be constrained and its transport distance is known, minimum northwestward flow rates can be estimated (~63-190 mm/yr) and are comparable to the magnitude of subducting Cocos plate motion (approx85 mm/yr). Trench-parallel flow needs to be taken into account in models evaluating thermal and chemical structure and melt generation in subduction zones.

(Table 1) Salinity and dissolved organic carbon concentration of marine water (ANT-XIX/2) and mangrove porewater (Brazil)

The chemical structure of refractory marine dissolved organic matter (DOM) is still largely unknown. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS) was used to resolve the complex mixtures of DOM and provide valuable information on elemental compositions on a molecular scale. We characterized and compared DOM from two sharply contrasting aquatic environments, algal-derived DOM from the Weddell Sea (Antarctica) and terrigenous DOM from pore water of a tropical mangrove area in northern Brazil. Several thousand molecular formulas in the mass range of 300-600 Da were identified and reproduced in element ratio plots. On the basis of molecular elemental composition and double-bond equivalents (DBE) we calculated an average composition for marine DOM. O/C ratios in the marine samples were lower (0.36 ± 0.01) than in the mangrove pore-water sample (0.42). A small proportion of chemical formulas with higher molecular mass in the marine samples were characterized by very low O/C and H/C ratios probably reflecting amphiphilic properties. The average number of unsaturations in the marine samples was surprisingly high (DBE = 9.9; mangrove pore water: DBE = 9.4) most likely due to a significant contribution of carbonyl carbon. There was no significant difference in elemental composition between surface and deep-water DOM in the Weddell Sea. Although there were some molecules with unique marine elemental composition, there was a conspicuous degree of similarity between the terrigenous and algal-derived end members. Approximately one third of the molecular formulas were present in all marine as well as in the mangrove samples. We infer that different forms of microbial degradation ultimately lead to similar structural features that are intrinsically refractory, independent of the source of the organic matter and the environmental conditions where degradation took place.