Dataset Information

Influence of Sulfide Nanoparticles on Dissolved Mercury and Zinc Quantification by Diffusive Gradient in Thin-Film Passive Samplers.

ABSTRACT: Diffusive gradient in thin-film (DGT) passive samplers are frequently used to monitor the concentrations of metals such as mercury and zinc in sediments and other aquatic environments. The application of these samplers generally presumes that they quantify only the dissolved fraction and not particle-bound metal species that are too large to migrate into the sampler. However, metals associated with very small nanoparticles (smaller than the pore size of DGT samplers) can be abundant in certain environments, yet the implications of these nanoparticles for DGT measurements are unclear. The objective of this study was to determine how the performance of the DGT sampler is affected by the presence of nanoparticulate species of Hg and Zn. DGT samplers were exposed to solutions containing known amounts of dissolved Hg(II) and nanoparticulate HgS (or dissolved Zn(II) and nanoparticulate ZnS). The amounts of Hg and Zn accumulated onto the DGT samplers were quantified over hours to days, and the rates of diffusion of the dissolved metal (i.e., the effective diffusion coefficient D) into the sampler's diffusion layer were calculated and compared for solutions containing varying concentrations of nanoparticles. The results suggested that the nanoparticles deposited on the surface of the samplers might have acted as sorbents, slowing the migration of the dissolved species into the samplers. The consequence was that the DGT sampler data underestimated the dissolved metal concentration in the solution. In addition, X-ray absorption spectroscopy was employed to determine the speciation of the Hg accumulated on the sampler binding layer, and the results indicated that HgS nanoparticles did not appear to directly contribute to the DGT measurement. Overall, our findings suggest that the deployment of DGT samplers in settings where nanoparticles are relevant (e.g., sediments) may result in DGT data that incorrectly estimated the dissolved metal concentrations. Models for metal uptake into the sampler may need to be reconsidered.

SUBMITTER: Pham AL

PROVIDER: S-EPMC4782790 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Influence of Sulfide Nanoparticles on Dissolved Mercury and Zinc Quantification by Diffusive Gradient in Thin-Film Passive Samplers.

Pham Anh Le-Tuan AL Johnson Carol C Manley Devon D Hsu-Kim Heileen H

Environmental science & technology 20151013 21

Diffusive gradient in thin-film (DGT) passive samplers are frequently used to monitor the concentrations of metals such as mercury and zinc in sediments and other aquatic environments. The application of these samplers generally presumes that they quantify only the dissolved fraction and not particle-bound metal species that are too large to migrate into the sampler. However, metals associated with very small nanoparticles (smaller than the pore size of DGT samplers) can be abundant in certain e ...[more]

PMID: 26414810

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Project description:Mercury is a risk in aquatic ecosystems when the metal is converted to methylmercury (MeHg) and subsequently bioaccumulates in aquatic food webs. This risk can be difficult to manage because of the complexity of biogeochemical processes for mercury and the need for accessible techniques to navigate this complexity. Here, we explored the use of diffusive gradient in thin-film (DGT) passive samplers as a tool to simultaneously quantify the methylation potential of inorganic Hg (IHg) and the bioaccumulation potential of MeHg in freshwater wetlands. Outdoor freshwater wetland mesocosms were amended with four isotopically labeled and geochemically relevant IHg forms that represent a range of methylation potentials (202Hg2+, 201Hg-humic acid, 199Hg-sorbed to FeS, and 200HgS nanoparticles). Six weeks after the spikes, we deployed DGT samplers in the mesocosm water and sediments, evaluated DGT-uptake rates of total Hg, MeHg, and IHg (calculated by difference) for the Hg isotope spikes, and examined correlations with total Hg, MeHg, and IHg concentrations in sediment, water, and micro and macrofauna in the ecosystem. In the sediments, we observed greater relative MeHg concentrations from the initially dissolved IHg isotope spikes and lower MeHg levels from the initially particulate IHg spikes. These trends were consistent with uptake flux of IHg into DGTs deployed in surface sediments. Moreover, we observed correlations between total Hg-DGT uptake flux and MeHg levels in periphyton biofilms, submergent plant stems, snails, and mosquitofish in the ecosystem. These correlations were better for DGTs deployed in the water column compared to DGTs in the sediments, suggesting the importance of vertical distribution of bioavailable MeHg in relation to food sources for macrofauna. Overall, these results demonstrate that DGT passive samplers are a relatively simple and efficient tool for predicting IHg methylation and MeHg bioaccumulation potentials without the need to explicitly delineate IHg and MeHg speciation and partitioning in complex ecosystems.

Project description:Products and starting materials containing volatile organic compounds (VOCs) can easily be found in a variety of businesses, making them a common source of occupational exposure. To prevent negative impacts on employee health, field industrial hygienists must conduct regular sampling to ensure exposures remain below the regulatory limits set by governmental and professional associations. As such, the need for sensitive and reliable exposure assessment techniques becomes evident. Over the preceding decade, the industrial hygiene research group at the University of Alabama at Birmingham (UAB) has been working on the development of an emerging, preanalytical technique known as photothermal desorption (PTD) to improve upon the analytical sensitivity of currently employed methods. PTD's novel design uses pulses of high-energy light to desorb analytes from thermally conductive, carbonaceous sorbents, to be delivered to downstream analytical detectors. Since PTD's conception, the theoretical framework and advances in sorbent fabrication have been investigated; however, further work is needed to produce a field-ready sampling device for use with PTD. As such, objectives of the present work were to design a PTD-compatible diffusive sampler prototype and characterize the prototype's sampling efficiencies for toluene, n-hexane, trichloroethylene, and isopropyl alcohol. In pursuit of these objectives, the study empirically quantified the sampled masses of toluene, n-hexane, trichloroethylene, and isopropyl alcohol, at occupationally relevant air concentrations, to be 12.17 ± 0.06, 8.2 ± 0.1, 3.97 ± 0.06, and 8.0 ± 0.1 mg, respectively. Moreover, the analyte sampling efficiencies were found to be 2.2 ± 0.1, 1.7 ± 0.1, 1.2 ± 0.1, and 0.51 ± 0.05 (unitless) when comparing empirically (i.e., laboratory observed) sample mass values to theoretically predicted values. The sampling efficiencies and collected sample masses reported herein demonstrate the promising design of PTD-compatible diffusive samplers. When used in conjunction with the PTD method, the prototype samplers present strong evidence for improving analytical sensitivity in exposure assessments of VOCs in the workplace.

Dataset Information

Influence of Sulfide Nanoparticles on Dissolved Mercury and Zinc Quantification by Diffusive Gradient in Thin-Film Passive Samplers.

Publications

Influence of Sulfide Nanoparticles on Dissolved Mercury and Zinc Quantification by Diffusive Gradient in Thin-Film Passive Samplers.

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