title: Comparison of different types of diffusive gradient in thin film samplers for measurement of dissolved methylmercury in freshwaters.
abstract: Determination of bioavailable concentrations of methylmercury (MeHg(+)) in freshwater is key to further understanding its potential risk and toxicity. In this work, two in-house-manufactured mercury-specific diffusive gradients in thin films (DGT) were used in laboratory to assess the lability of MeHg(+), and to develop a relationship between chemical lability and bioavailability. After diffusing through the diffusive gel, the MeHg(+) accumulated in a thiol functionalised resin gel was extracted using acidic thiourea that was analysed using aqueous-phase propylation followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC) coupled to pyrolysis-atomic fluorescence spectrometry (Py-AFS) detection. The diffusion coefficient (D) at 25°C in agarose (A-DGT) in the absence and presence of dissolved organic matter (DOM) was obtained. Moreover, these values were experimentally compared against polyacrylamide (P-DGT), which is the most frequently used DGT for mercury to date. Statistically significant differences were observed between D values for A-DGT in the absence (3.15×10(-6) cm(2) s(-1)) and presence of DOM (2.68×10(-6) cm(2) s(-1)) and also for P-DGT (2.49×10(-6) and 1.69×10(-6) cm(2) s(-1)). Interestingly, our results show that diffusion of MeHg(+) was higher on agarose diffusive gel with and without DOM in comparison with those observed in polyacrylamide. Even with higher diffusion coefficients of MeHg(+) in the agarose diffusion layer, however, DGT based on polyacrylamide seems to be a better choice for eutrophic waters, when monitoring very low concentrations of MeHg(+), considering its slightly higher uptake capacity.
authors.affiliation: Environmental Chemistry Department, Institute of Environmental Assessment and Water Research, IDÆA-CSIC, E-08034 Barcelona, Spain.
authors.forename: Cristal
authors.initials: C
authors.lastname: Fernández-Gómez
authors.affiliation: Environmental Chemistry Department, Institute of Environmental Assessment and Water Research, IDÆA-CSIC, E-08034 Barcelona, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Bayona
authors.affiliation: Environmental Chemistry Department, Institute of Environmental Assessment and Water Research, IDÆA-CSIC, E-08034 Barcelona, Spain. Electronic address: sdsqam@cid.csic.es.
authors.forename: Sergi
authors.initials: S
authors.lastname: Díez
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002138:Calibration; D002849:Chromatography, Gas / Q000379:methods; D004058:Diffusion; D004784:Environmental Monitoring / Q000379:methods; D005618:Fresh Water / Q000737:chemistry; D008422:Materials Testing; D008628:Mercury / Q000032:analysis* / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D011786:Quality Control; D012685:Sepharose / Q000737:chemistry*; D052616:Solid Phase Extraction / Q000379:methods; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013890:Thiourea / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D008628:Mercury; D009930:Organic Chemicals; D012685:Sepharose; D013890:Thiourea; D014874:Water Pollutants, Chemical; D000099166:Polyacrylamides
keywords: Agarose; Bioavailable; DGT; Methylmercury; Polyacrylamide