Solubility of antimony and other elements in samples taken from shooting ranges

The aim of this study was to determine whether or not Sb and other elements (Ni, Cu, Bi, Tl, and Hg) originating from Pb alloy (2-5 wt. % Sb) bullets become more soluble as a result of weathering and what mechanisms possibly control their solubility. Samples were taken from bank material behind the targets at seven Swiss shooting ranges. The samples were dried, sieved, analyzed, and subjected to leaching experiments. Total average concentrations of Sb ranged from 0.5 to 13.8 g kg(-1). In the leaching experiments, Sb was almost exclusively present in solution as the oxidized species Sb(V) in concentrations of up to 5 mg L(-1). The Ca mineral Ca[Sb(OH)6]2 is suggested to control dissolved Sb(V) concentrations in soils at high concentrations. Oxalate extractions suggested that approximately 50% of Sb [predominantly Sb(V)] in the <0.5-mm fraction was adsorbed to Fe (hydr)oxides and possibly other minerals, such as calcite, that are soluble at pH 2. However, it is possible that only a fraction of the oxalate-extractable Sb(V) is reversibly bound to mineral surfaces. It was concluded that the release of Sb is significant and considerably higher than the other elements under investigation and that the mechanisms controlling Sb mobility should be further investigated.     

Photochemical production of methane in natural waters: implications for its present and past oceanic source

We conducted irradiation experiments with riverine, estuarine, and marine water samples to investigate the possibility of photochemical methane (CH4) formation. CH4 photoproduction was undetectable under oxic conditions or in the absence of methyl radical precursors indicating that its photochemical formation is negligible in the present ocean. Significant photochemical CH4 production was observed in the presence of a methyl radical precursor such as acetone under strictly anoxic conditions. Our results indicate an indirect formation mechanism with coloured dissolved organic matter acting as photosensitizer. We suggest that photochemical CH4 formation might have occurred in the anoxic ocean surface layer of the Archean prior to the onset of O2 accumulation in the atmosphere at around 2300 million years ago. Oceanic CH4 photoproduction via methyl radical (CH3) precursors and its subsequent release to the atmosphere may have contributed to high CH4 mixing ratios in the Archean atmosphere.     

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Intake of phthalates and di(2-ethylhexyl)adipate: results of the Integrated Exposure Assessment Survey based on duplicate diet samples and biomonitoring data

Phthalates are ubiquitous environmental chemicals with potential detrimental health effects. The purpose of our study was to quantify dietary intake of phthalates and of DEHA (Di-ethylhexyl adipate) using duplicate diet samples and to compare these data with the calculated data based on urinary levels of primary and secondary phthalate metabolites. 27 female and 23 male healthy subjects aged 14-60 years collected daily duplicate diet samples over 7 consecutive days. Overall, 11 phthalates were measured in the duplicates by GC/MS and LC/MS methods. Urinary levels of primary and secondary phthalate metabolites are also available. The median (95th percentile) daily intake via food was 2.4 (4.0) microg/kg b.w. (Di-2-ethylhexyl phthalate, DEHP), 0.3 (1.4) microg/kg b.w. (Di-n-butyl phthalate, DnBP), 0.6 (2.1) microg/kg b.w. (Di-isobutyl phthalate, DiBP) and 0.7 (2.2) microg/kg b.w. for DEHA. MEPH (Mono-2-ethylhexyl phthalate) was detectable only in minor concentrations in the samples, thus conversion of DEHP to MEHP and dietary intake of MEHP were negligible. When comparing back-calculated intake data of the DEHP metabolites with dietary DEHP intake from the day before significant correlations were observed for most of the metabolites. No correlation was found for DnBP and only a weak but significant correlation for DiBP. The median and 95th percentile daily dietary intake of all target analytes did not exceed the recommended tolerable daily intake. Our data indicated that food was the predominant intake source of DEHP, whilst other sources considerably contributed to the daily intake of DnBP and DiBP in an adult population.