Уточнить поиск
Результаты 1-10 из 98
Toxic metals in children's toys and jewelry: Coupling bioaccessibility with risk assessment Полный текст
2015
Cui, Xin-Yi | Li, Shi-Wei | Zhang, Shu-Jun | Fan, Ying-Ying | Ma, Lena Q.
A total of 45 children's toys and jewelry were tested for total and bioaccessible metal concentrations. Total As, Cd, Sb, Cr, Ni, and Pb concentrations were 0.22–19, 0.01–139, 0.1–189, 0.06–846, 0.14–2894 and 0.08–860,000 mg kg−1. Metallic products had the highest concentrations, with 3–7 out of 13 samples exceeding the European Union safety limit for Cd, Pb, Cr, or Ni. However, assessment based on hazard index >1 and bioaccessible metal showed different trends. Under saliva mobilization or gastric ingestion, 11 out of 45 samples showed HI >1 for As, Cd, Sb, Cr, or Ni. Pb with the highest total concentration showed HI <1 for all samples while Ni showed the most hazard with HI up to 113. Our data suggest the importance of using bioaccessibility to evaluate health hazard of metals in children's toys and jewelry, and besides Pb and Cd, As, Ni, Cr, and Sb in children's products also deserve attention.
Показать больше [+] Меньше [-]Influence of polyethylene microplastic beads on the uptake and localization of silver in zebrafish (Danio rerio) Полный текст
2015
Khan, Farhan R. | Syberg, Kristian | Shashoua, Yvonne | Bury, Nicolas R.
This study aimed to determine whether the uptake and localization of Ag in zebrafish was affected by the presence of polyethylene microplastic beads (PE MPBs). Zebrafish were exposed to 1 μg Ag L−1 (radiolabelled with 110mAg) for 4 and 24 h in the presence or absence of PE MPBs (10, 100 or 1000 MPBs mL−1), and one treatment in which MPBs (1000 MPBs mL−1) were incubated with Ag to promote adsorption. The presence of MPBs, at any of the tested doses, had no effect on the uptake or localization of Ag. However, exposure to the Ag-incubated MPBs (∽75% of the Ag bound to MPBs) significantly reduced Ag uptake at both time points and also significantly increased the proportion of intestinal Ag. This study demonstrates that microplastics can alter the bioavailability and uptake route of a metal contaminant in a model fish species.
Показать больше [+] Меньше [-]Tenax as sorption sink for in vitro bioaccessibility measurement of polycyclic aromatic hydrocarbons in soils Полный текст
2015
Li, Chao | Cui, Xin−Yi | Fan, Ying−Ying | Teng, Ying | Nan, Zhong−Ren | Ma, Lena Q.
Physiologically based in vitro methods have been developed to measure bioaccessibility of organic contaminants in soils. However, bioaccessibility of hydrophobic organic contaminants (HOCs) can be underestimated by in vitro tests if gastrointestinal (GI) solution fails to provide sufficient sorption sink for HOCs. To circumvent this drawback, Tenax was included in GI solution as sorption sink to trap mobilized HOCs and maintain the desorption gradient between soil and GI solution. Polycyclic aromatic hydrocarbons (PAHs) were selected as target HOCs, and physiologically based extraction test (PBET) was selected as the in vitro method. Inclusion of Tenax in GI solution increased bioaccessibility of PAHs in five spiked soils from 8.25–20.8% to 55.7–65.9% and the bioaccessibility of PAHs in a field contaminated soil from 3.70–6.92% to 16.3–31.0%. Our results demonstrated the effectiveness of Tenax as sorption sink to enhance PAH mobilization in bioaccessibility measurement in soils.
Показать больше [+] Меньше [-]Characterising the exchangeability of phenanthrene associated with naturally occurring soil colloids using an isotopic dilution technique Полный текст
2015
Tavakkoli, Ehsan | Juhasz, Albert | Donner, Erica | Lombi, Enzo
Characterising the exchangeability of phenanthrene associated with naturally occurring soil colloids using an isotopic dilution technique Полный текст
2015
Tavakkoli, Ehsan | Juhasz, Albert | Donner, Erica | Lombi, Enzo
The association of polycyclic aromatic hydrocarbons (PAHs) with inorganic and organic colloids is an important factor influencing their bioavailability, mobility and degradation in the environment. Despite this, our understanding of the exchangeability and potential bioavailability of PAHs associated with colloids is limited. The objective of this study was to use phenanthrene as a model PAH compound and develop a technique using 14C phenanthrene to quantify the isotopically exchangeable and non-exchangeable forms of phenanthrene in filtered soil water or sodium tetraborate extracts. The study was also designed to investigate the exchangeability of colloidal phenanthrene as a function of particle size. Our findings suggest that the exchangeability of phenanthrene in sodium tetraborate is controlled by both inorganic and organic colloids, while in aqueous solutions inorganic colloids play the dominant role (even though coating of these by organic matter cannot be excluded). Filter pore size did not have a significant effect on phenanthrene exchangeability.
Показать больше [+] Меньше [-]Characterising the exchangeability of phenanthrene associated with naturally occurring soil colloids using an isotopic dilution technique Полный текст
2015
Tavakkoli, E. | Juhasz, A. | Donner, E. | Lombi, E.
Abstract not available. | Ehsan Tavakkoli, Albert Juhasz, Erica Donner, Enzo Lombi
Показать больше [+] Меньше [-]Interactions of multiwalled carbon nanotubes with algal cells: Quantification of association, visualization of uptake, and measurement of alterations in the composition of cells Полный текст
2015
Rhiem, Stefan | Riding, Matthew J. | Baumgartner, Werner | Martin, Francis L. | Semple, K. T. (Kirk T.) | Jones, K. C. (Kevin C.) | Schäffer, Andreas | Maes, Hanna M.
Carbon nanotubes (CNTs) are considered promising materials in nanotechnology. We quantified CNT accumulation by the alga Desmodesmus subspicatus. Cells were exposed to radiolabeled CNTs (14C-CNTs; 1 mg/L) to determine uptake and association, as well as elimination and dissociation in clear media. Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was used to detect effects of CNTs on algae. CNT-cell interactions were visualized by electron microscopy and related to alterations in their cell composition. A concentration factor of 5000 L/kg dry weight was calculated. Most of the material agglomerated around the cells, but single tubes were detected in the cytoplasm. Computational analyses of the ATR-FTIR data showed that CNT treated algae differed from controls at all sampling times. CNT exposure changed the biochemical composition of cells. The fact that CNTs are bioavailable for algae and that they influence the cell composition is important with regard to environmental risk assessment of this nanomaterial.
Показать больше [+] Меньше [-]Microplastic in three urban estuaries, China Полный текст
2015
Zhao, Shiye | Zhu, Lixin | Li, Daoji
Estuarine Microplastics (MPs) are limited to know globally. By filtering subsurface water through 330 μm nets, MPs in Jiaojiang, Oujiang Estuaries were quantified, as well as that in Minjiang Estuary responding to Typhoon Soulik. Polymer matrix was analyzed by Raman spectroscopy. MP (<5 mm) comprised more than 90% of total number plastics. The highest MPs density was found in Minjiang, following Jiaojiang and Oujiang. Fibers and granules were the primary shapes, with no pellets found. Colored MPs were the majority. The concentrations of suspended microplastics determine their bioavailability to low trophic organisms, and then possibly promoting the transfer of microplastic to higher trophic levels. Polypropylene and polyethylene were the prevalent types of MPs analyzed. Economic structures in urban estuaries influenced on MPs contamination levels. Typhoon didn't influence the suspended MP densities significantly. Our results provide basic information for better understanding suspended microplastics within urban estuaries and for managerial actions.
Показать больше [+] Меньше [-]Dual partitioning and attachment effects of rhamnolipid on pyrene biodegradation under bioavailability restrictions Полный текст
2015
Congiu, Eleonora | Parsons, John R. | Ortega-Calvo, Jose Julio
We investigated the effects of different bioavailability scenarios on the rhamnolipid-enhanced biodegradation of pyrene by the representative polycyclic aromatic hydrocarbon degrader Mycobacterium gilvum VM552. This biosurfactant enhanced biodegradation when pyrene was provided in the form of solid crystals; no effect was observed when the same amount of the chemical was preloaded on polydimethylsiloxane (PDMS). An enhanced effect was observed when pyrene was sorbed into soil but not with the dissolved compound. Synchronous fluorescence spectrophotometry and liquid scintillation were used to determine the phase exchange of pyrene. We also investigated the phase distribution of bacteria. Our results suggest that the rhamnolipid can enhance the biodegradation of pyrene by micellar solubilization and increase diffusive uptake. These mechanisms increase substrate acquisition by bacterial cells at exposure concentrations well above the half-saturation constant for active uptake. The moderate solubilization of pyrene from PDMS by the rhamnolipid and the prevention of cell attachment may explain the lack of enhancement for pyrene-preloaded PDMS.
Показать больше [+] Меньше [-]Urban legacies and soil management affect the concentration and speciation of trace metals in Los Angeles community garden soils Полный текст
2015
Clarke, Lorraine Weller | Jenerette, G Darrel | Bain, Daniel J.
Heavy metals in urban soils can compromise human health, especially in urban gardens, where gardeners may ingest contaminated dust or crops. To identify patterns of urban garden metal contamination, we measured concentrations and bioavailability of Pb, As, and Cd in soils associated with twelve community gardens in Los Angeles County, CA. This included sequential extractions to partition metals among exchangeable, reducible, organic, or residual fractions. Proximity to road increased all metal concentrations, suggesting vehicle emissions sources. Reducible Pb increased with neighborhood age, suggesting leaded paint as a likely pollutant source. Exchangeable Cd and As both increased with road proximity. Only cultivated soils showed an increase in exchangeable As with road proximity, potentially due to reducing humic acid interactions while Cd bioavailability was mitigated by organic matter. Understanding the geochemical phases and metal bioavailability allows incorporation of contamination patterns into urban planning.
Показать больше [+] Меньше [-]Evaluation of the measurement of Cu(II) bioavailability in complex aqueous media using a hollow-fiber supported liquid membrane device (HFSLM) and two microalgae species (Pseudokirchneriella subcapitata and Scenedesmus acutus) Полный текст
2015
Rodríguez-Morales, Erik A. | Rodríguez de San Miguel, Eduardo | de Gyves, Josefina
The environmental bioavailability of copper was determined using a hollow-fiber supported liquid membrane (HFSLM) device as a chemical surrogate and two microalgae species (Scenedesmus acutus and Pseudokirchneriella subcapitata). Several experimental conditions were studied: pH, the presence of organic matter, inorganic anions, and concomitant cations. The results indicated a strong relationship between the response given by the HFSLM and the microalgae species with free copper concentrations measured by an ion selective electrode (ISE), in accordance with the free-ion activity model (FIAM). A significant positive correlation was evident when comparing the bioavailability results measured by the HFSLM and the S. acutus microalga species, showing that the synthetic device may emulate biological uptake and, consequently, be used as a chemical test for bioavailability measurements using this alga as a biological reference.
Показать больше [+] Меньше [-]Arsenic availability in rice from a mining area: Is amorphous iron oxide-bound arsenic a source or sink? Полный текст
2015
Liu, Chuanping | Yu, Huan-Yun | Liu, Chengshuai | Li, Fangbai | Xu, Xianghua | Wang, Qi
The effect of iron (Fe) redox cycling on the mobility and bioavailability of arsenic (As) in paddy soils has attracted increasing concerns, especially in Asia, where the paddy soil is characteristic of Fe with high abundance and activity. However, whether amorphous Fe oxide-bound As acts as a source or a sink of As in natural field conditions needs to be clarified further. In this study, 73 pairs of soil and rice were collected from paddy fields contaminated by As-containing acid mining drainage. The most significant correlations between the iron fractions and As fractions suggest that Fe redox cycling can directly affect As fractionation in soils, which can then indirectly affect As bioavailability. Significantly negative correlations between amorphous Fe oxide-bound As in soil and As in rice grain were found, indicating that amorphous Fe oxide-bound As acts a sink of As.
Показать больше [+] Меньше [-]