Variations in Hg isotope ratios in cinnabar ores obtained from different countries were detected by high precision isotope ratio measurements using multi-collector inductively coupled mass spectrometry (MC-ICP-MS). Values of delta198/202Hg varied from 0.0-1.3 percent per thousand relative to a NIST SRM 1641d Hg solution. The typical external uncertainty of the delta values was 0.06 to 0.26 percent per thousand. Hg was introduced into the plasma as elemental Hg after reduction by sodium borohydride. A significant fractionation of lead isotopes was observed during the simultaneous generation of lead hydride, preventing normalization of the Hg isotope ratios using the measured 208/206Pb ratio. Hg ratios were instead corrected employing the simultaneously measured 205/203T1 ratio. Using a 10 ng ml(-1) Hg solution and 10 min of sampling, introducing 60 ng of Hg, the internal precision of the isotope ratio measurements was as low as 14 ppm. Absolute Hg ratios deviated from the representative IUPAC values by approximately 0.2% per u. This observation is explained by the inadequacy of the exponential law to correct for mass bias in MC-ICP-MS measurements. In the absence of a precisely characterized Hg isotope ratio standard, we were not able to determine unambiguously the absolute Hg ratios of the ore samples, highlighting the urgent need for certified standard materials.

Gliding arc discharge has been proved to be effective in treatment of gas and liquid contaminants. In this study, physical characteristics of dc gliding arc discharge and its application to naphthalene destruction are investigated with different external resistances and carrier gases. The decomposition rate increases with increasing of oxygen concentration and decreases with external resistance. This value can be achieved up to 92.3% at the external resistance of 50 kOmega in the oxygen discharge, while the highest destruction energy efficiency reaches 3.6 g (kW h)(-1) with the external resistance of 93 kOmega. Possible reaction pathways and degradation mechanisms in the plasma with different gases are proposed by qualitative analysis of postdestructed products. In the air and oxygen gliding arc discharges, the naphthalene degradation is mainly governed by reactions with oxygen-derived radicals.

Precise and accurate analysis of Hg isotope compositions in environmental samples can be an invaluable tool in investigating Hg cycles in the environment. We have developed a method for high precision Hg isotope analysis using a gold trap sample introduction system coupled to a Thermo Finnigan MC-ICP-MS. Environmental samples were pyrolyzed at high temperature and Hg released from the samples was collected in gold traps. The Hg on the gold traps was then thermally released into a sample introduction system coupled to an MC-ICP-MS. The sample introduction system extended the Hg signal duration, which would otherwise be a short transient signal if released directly into the plasma, thus significantly improving the precision and accuracy of Hg isotope measurement. Instrumental mass bias was corrected using a Tl internal isotopic standard and a ''standard-sample-standard'' bracketing technique. Based on the long term measurement of NIST-2225 elemental Hg standard, the external precision ranges from 44 to 109 ppm for 201 Hg/ 202 Hg and 199 Hg/ 202 Hg ratios, respectively. The average mass bias corrected Hg isotope ratios for

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