We developed a technique to measure monomethylmercury (MMHg) concentrations from small volumes (180 mL) of seawater at low femtomolar concentrations using direct ethylation derivitization, decreasing the required volume by 90% from current methods while maintaining a 5 fM detection limit. In this method, addition of ascorbic acid before derivitization of MMHg allows for full recovery of MMHg from the seawater matrix without the need for sample distillation or extraction. The small sample size and relative ease of detection are ideal both for shipboard as well as shore‐based measurements of preserved MMHg samples. Combined with shipboard determination of dimethylmercury (DMHg) and elemental mercury (Hg(0)), this method can be used to determine full marine mercury speciation.

Abstract. Passive air samplers (PASs), which provide time-averaged concentrations of gaseous mercury over the timescale of weeks to months, are promising for filling a gap in the monitoring of atmospheric mercury worldwide. Their usefulness will depend on their ease of use and robustness under field conditions, their availability and affordability, and most notably, their ability to provide results of acceptable precision and accuracy. Here we describe a comparative evaluation of three PASs with respect to their ability to precisely and accurately record atmospheric background mercury concentrations at sites in both southern Italy and southern Ontario, Canada. The study includes the CNR-PAS with gold nanoparticles as a sorbent, developed by the Italian National Research Council, the IVL-PAS using an activated carbon-coated disk, developed by the Swedish Environmental Research Institute, and the MerPAS® using a sulfur-impregnated activated carbon sorbent, developed at the University of Toronto and commercialized by Tekran. Detection limits are deduced from the variability in the amount of mercury quantified in more than 20 field blank samples for each PAS. Analytical and sampling precision is quantified through 22 triplicate deployments for each PAS, ranging in duration from 2 to 12 weeks. Accuracy and bias are assessed through comparison with gaseous elemental mercury concentrations recorded by Tekran 2537 automated mercury analyzers operating alongside the PASs at both locations. The performance of the PASs was significantly better in Italy, with all of them providing concentrations that are not significantly different from the average concentrations of the Tekran 2537 instruments. In Canada, where weather conditions were much harsher and more variable during the February through April deployment period, there are differences amongst the PASs. At both sites, the MerPAS® is currently the most sensitive, precise, and accurate among the three PASs. A key reason for this is the larger size and the radial configuration of the MerPAS®, which results in lower blank levels relative to the sequestered amounts of mercury when compared to the other two PASs, which rely on axial diffusion geometries. Since blank correction becomes relatively smaller with longer deployments, performance tends to be closer amongst the PASs during deployments of 8 and 12 weeks.

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SummaryIn this paper the evaluation of polycychc aromatic hydrocarbons (PAHs) in gasoline is described. A procedure involving a double extraction of samples with N-methylpirrohdonewater-phosphoric acid and with cyclohexane has been used followed by HPLC-DAD and GC-MS. The results obtained show that all gasoline samples contain PAHs with I',,vo to six rings and no substantial difference was noticed bel',,veen leaded and unleaded gasoline. The benzo(a)-pyrene content ranged bel',,veen 1.0-2.0 mg L ], a comparatively high concentration for a dangerous compound.

An investigation of iodine and bromine interference on mercury measurements was carried out in aqueous samples by using continuous flow techniques. The role of acidity in the extent of the interference was also studied. A variety of methods for interference correction were tested, mostly aimed at changing the chemistry of the method to eliminate the offending complexes. The tests evaluated various methods of pH adjustment of the sample matrix prior to reduction with tin(II) chloride and the use of KBH(4) for reduction. On-line alkaline pH adjustment prior to tin(II) chloride reduction was found to be the most effective method for interference correction. Physical changes to the apparatus to extend the reaction time between the sample and SnCl(2) were also explored.