High resolution ICP-MS was used to determine Cu, Zn, Cd and Pb in urine. The effect of sample dilution, preparation method and choice of internal standard were assessed. Sample dilution (1+9) with In as the internal standard was found to offer an acceptable compromise between analytical accuracy and sample throughput. A spectral resolution of 3000 was used to separate Cu and Zn isotopes from interferences commonly found in biological matrices, while a resolution of 300, offering increased sensitivity and lower detection limits, was used for Cd and Pb. The accuracy and precision of the analytical method were evaluated using two Bio-Rad Lyphochek standard urines. The concentrations of Cu, Zn, Cd and Pb in Bio-Rad Level 1 reference urine were determined by external calibration and were found to agree to within 0-17% of recommended values (Cu 48, Zn 710, Cd 6.5 and Pb 14.3 ng g ^–1 ). Closer agreement of 0-7% was found for Bio-Rad Level 2 reference urine (Cu 63, Zn 1057, Cd 12.3 and Pb 69 ng g ^–1 ). Forty-two urine samples from seven workers occupationally exposed to Cd were analysed and the results were compared with those obtained from 11 samples collected from four non-exposed volunteers. Similar average concentrations of Cu and Zn were found in both groups when the results were normalised to creatinine levels. Workers exposed to Cd were found to have an average urine Cd concentration elevated approximately 7-8-fold over that measured for the control group (about 2.2 compared with about 0.3 ng g ^–1 , or 1.7 and 0.2 μg per gram of creatinine when normalised). Urinary levels of Pb were slightly increased in the cadmium exposed workers (about 6 compared with about 4 ng g ^–1 ).

The permanent ice cover of Lake Vida (Antarctica) encapsulates an extreme cryogenic brine ecosystem (−13 °C; salinity, 200). This aphotic ecosystem is anoxic and consists of a slightly acidic (pH 6.2) sodium chloride-dominated brine. Expeditions in 2005 and 2010 were conducted to investigate the biogeochemistry of Lake Vida’s brine system. A phylogenetically diverse and metabolically active Bacteria dominated microbial assemblage was observed in the brine. These bacteria live under very high levels of reduced metals, ammonia, molecular hydrogen (H ₂ ), and dissolved organic carbon, as well as high concentrations of oxidized species of nitrogen (i.e., supersaturated nitrous oxide and ∼1 mmol⋅L ⁻¹ nitrate) and sulfur (as sulfate). The existence of this system, with active biota, and a suite of reduced as well as oxidized compounds, is unusual given the millennial scale of its isolation from external sources of energy. The geochemistry of the brine suggests that abiotic brine-rock reactions may occur in this system and that the rich sources of dissolved electron acceptors prevent sulfate reduction and methanogenesis from being energetically favorable. The discovery of this ecosystem and the in situ biotic and abiotic processes occurring at low temperature provides a tractable system to study habitability of isolated terrestrial cryoenvironments (e.g., permafrost cryopegs and subglacial ecosystems), and is a potential analog for habitats on other icy worlds where water-rock reactions may cooccur with saline deposits and subsurface oceans.