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Science in the News
Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health
- Increase in platinum group elements in Mexico City as revealed from growth rings of Taxodium mucronatum ten 2015-04-24
Tree rings may be used as indicators of contamination events providing information on the chronology and the elemental composition of the contamination. In this framework, we report PGEs enrichment in growth rings of Taxodium mucronatum ten for trees growing in the central area of Mexico City as compared to trees growing in a non-urban environment. Concentrations of PGE were determined by ICP-MS analysis on microwave-digested tree rings. The element found in higher concentrations was Pd (1.13â87.98Â ÎźgÂ kgâ1), followed by Rh (0.28â36.81Â ÎźgÂ kgâ1) and Pt (0.106â7.21Â ÎźgÂ kgâ1). The concentration trends of PGEs in the tree-ring sequences from the urban area presented significant correlation values when comparing between trees (r between 0.618 and 0.98, PÂ <Â 0.025) and between elements within individual trees (r between 0.76 and 0.994, PÂ <Â 0.01). Furthermore, a clear increase was observed for rings after 1997, with enrichment of up to 60 times the mean concentration found for the sequence from the non-urban area and up to 40 times the mean concentration for the pre-1991 period in the urban trees. These results also demonstrate the feasibility of applying T. mucronatum ten to be used as a bioindicator of the increase in PGE in urban environments.
- Trace elements distributions at Datoko-Shega artisanal mining site, northern Ghana 2015-04-24
Environmental geochemistry classifies elements into essential, non-essential and toxic elements in relationship to human health. To assess the environmental impact of mining at Datoko-Shega area, the distributions and concentrations of trace elements in stream sediments and soil samples were carried out. X-ray fluorescence analytical technique was used to measure the major and trace element concentrations in sediments and modified fire assay absorption spectrometry in soils. The results showed general depletion of major elements except titanium oxide (TiO2) compared to the average crustal concentrations. The retention of TiO2 at the near surface environment probably was due to the intense tropical weathering accompanied by the removal of fine sediments and soil fractions during the harmattan season by the dry north-east trade winds and sheet wash deposits formed after flash floods. The results also showed extreme contamination of selenium (Se), cadmium (Cd) and mercury (Hg), plus strong contaminations of arsenic (As) and chromium (Cr) in addition to moderate contamination of lead (Pb) in the trace element samples relative to crustal averages in the upper continental crust. However Hg, Pb and Cd concentrations tend to be high around the artisanal workings. It was recognised from the analysis of the results that the artisanal mining activity harnessed and introduces some potentially toxic elements such as Hg, Cd and Pb mostly in the artisan mine sites. But the interpretation of the trace element data thus invalidates the elevation of As concentrations to be from the mine operations. It consequently noticed As values in the mine-impacted areas to be similar or sometimes lower than As values in areas outside the mine sites from the stream sediment results.
- A gradient of mercury concentrations in Scottish single malt whiskies 2015-04-18
Mercury (Hg) concentrations were measured in 26 Scottish single malt whiskies, and all found to be very low (<10Â ngÂ Lâ1), posing no threat to human health through reasonable levels of consumption. However, a significant south-to-north declining gradient in Hg concentrations was observed reflecting that reported for atmospheric deposition. We speculate that this gradient could be due to a combination of contemporary deposition and the legacy of industrial mercury emissions and deposition over the last 200Â years affecting concentrations in local waters used in whisky production. As UK atmospheric emissions of mercury have declined by 90Â % since the 1970s, we suggest that whisky being produced today should have even lower Hg concentrations when consumed in 10- to 15-years time. This reduction may be compromised by the remobilisation of contaminants stored in catchment soils being transferred to source waters, but is very unlikely to raise the negligible health risk due to Hg from Scottish single malt whisky consumption.