Sample collection, filtration and preservation protocols for the determination of ‘total dissolved’ mercury in waters

Abstract

The objective of the work carried out was to recommend protocols for the collection, filtration (0.45 microm) and preservation of surface water samples for the subsequent determination of total 'dissolved' Hg. Cold vapour (CV) ICP-MS was employed to determine Hg; samples were acidified to a strength of 4 mol l(-1) HCl and 1% NaBH4 was used as the reducing agent in-line. Four types of 125 ml bottles were studied (Teflon, fluorinated ethene propene copolymer, FEP; high density polyethylene, HDPE; polyethylene terephthalate copolyester, PET; polypropylene, PP), together with three cleaning methods (EPA Methods 1631, 1638 and a rinse with reverse osmosis deionised water, 'MilliQ'). The transmission properties of the four materials were also studied to evaluate the potential for contamination from atmospheric Hg0. Results of this bottle study (n = 195), all below the detection limit of 0.5 ng l(-1), indicate that the bottles of choice, from an economic and time-saving perspective, are HDPE and PP, the latter being preferable if the sample is to be stored in a contaminated atmosphere. The bottles would be used on a once-only basis, negating the need for labourious and costly cleaning on repeat use. A simple rinse with MilliQ water would suffice prior to use. Twelve 0.45 microm filter systems (mostly Millipore and Gelman) were studied for (a) their potential Hg contamination properties and (b) their retention of Hg, possibly in colloidal form, during filtration. Ottawa River water, spiked at 50 ng l(-1) Hg, was used as a control sample. Again blank values were all negative, indicating contamination was not a concern but different recoveries of Hg were obtained across the different systems. The optimum systems to use, in that they provided maximum recovery (ca 80%) of Hg, are the Millipore Sterivex capsule and the Millipore Millex disc, both based on the hydrophilic Durapore membrane. The lowest recoveries (23-36%) were found with the Gelman AquaPrep systems and the Millipore HN nylon filter. Four control samples, Ottawa, Rideau and Gatineau Rivers, and a MilliQ blank, were used to study three preservation approaches, in the media: 0.5% BrCl, 2% HCl and 0.04% K2Cr2O7 in 1% HNO3. Mercury was stable for 28 days in a medium of 0.5% BrCl in all four samples but the other two media showed a loss of up to ca 20% Hg over this time frame, the loss being sample and time dependent. This may be a species transformation which is not detected by CV-ICP-MS from an HCl medium but this requires further investigation. Mercury was stable over the 28 days in the spiked blank MilliQ sample for all three preservation media.

A synthesis of atmospheric mercury depletion event chemistry in the atmosphere and snow

“…In general, water samples are collected in Teflon or glass bottles containing a 0.4-0.5% acidic solution of HCl in order to reduce contamination and to preserve the Hg in the sample (Parker and Bloom, 2005). As well, samples can be collected using high density polyethylene bottles (Hall et al, 2002) should Teflon not be available. BrCl is added to the sample after collection to digest the Hg in the water followed by reduction of the Hg with stannous chloride (SnCl 2 ).…”

“…Aqueous monomethyl mercury (MeHg) concentrations are reported in levels from a few tenths of a picogram per litre in Arctic Lakes (St. Louis et al, 2005;Hammerschmidt et al, 2006a) and the Mackenzie river basin and mainstream (Leitch et al, 2007) to several hundreds of picograms per litre in small Arctic ponds (St. Louis et al, 2005) and the North Atlantic Ocean . In most applications MeHg was determined by aqueous phase ethylation with sodium tetraethylborate, subsequent concentration either by cryofocusing with liquid nitrogen (Demuth and Heumann, 2001) or by collection on Tenax traps (Hammerschmidt et al, 2006a), separation by capillary gas chromatography and finished by AFS detection St.…”

Trace Metal Levels in Water and Sediment from the Sakumo II and Muni Lagoons, Ghana

“…Trace metals have been determined in potable water (Garcia et al, 1999) and fresh and marine waters (Hall et al, 2002). Although water is commonly employed as a pollution indicator by trace metals, sediment can also provide a deeper insight into the long-term pollution state of the water body.…”

Levels of trace metals in water and sediment from Tyume River and its effects on an irrigated farmland

“…Its toxic effects in man are related to dermal, lung and nasal sinus cancers. Trace metals have been determined in potable water (Holynska et al, 1996;Gulson et al, 1997;Garcia et al, 1999) and fresh-and marine waters (Fatoki et al, 2002;Fatoki, 1993;Batterham et al, 1997;Fiaccabrino et al, 1998;Hall et al, 2002), using varieties of methods. Although water is commonly employed as a pollution indicator by trace metals, sediment can also provide a deeper insight into the long-term pollution state of the water-body.…”