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Occurrence of chlorinated paraffins in house dust samples from Bavaria, Germany Texte intégral
2013
Hilger, B. | Fromme, H. | Völkel, W. | Coelhan, M.
Levels and distribution of chlorinated paraffins were studied in randomly taken house dust samples (<63 μm) from the greater area of Munich, Germany. Quantification of short- (SCCPs, C10–C13) and medium-chain chlorinated paraffins (MCCPs, C14–C16) were performed using gas chromatography electron capture negative ion mass spectrometry (GC–ECNI–MS). Concentrations of MCCPs in private household samples varied between 9 μg/g and 892 μg/g, and exceeded levels of SCCPs, which were in the range of 4–27 μg/g. Two dust samples from a public building contained up to 2050 μg/g SCCPs but no MCCPs. Among MCCPs, chlorinated tetradecanes were major components with a proportion of almost 50%. Among SCCPs, chlorinated dodecanes were usually present at higher concentrations than the congeners of any C10, C11, and C13 chains. The results indicate that particularly MCCPs may be present in relatively high concentrations in house dusts.
Afficher plus [+] Moins [-]Effects of freeze–thaw cycling on metal-phosphate formation and stability in single and multi-metal systems Texte intégral
2013
Hafsteinsdóttir, Erla G. | White, D. A. (Duanne A.) | Gore, Damian B.
Freeze–thaw cycling may influence the chemistry, mineral stability and reaction rate during metal orthophosphate fixation. This study assessed the formation and stability of Cu-, Pb-, and Zn-phosphates in chemically simple laboratory systems during 240 freeze–thaw cycles (120 days) from +10 to −20 °C, using X-ray diffractometry. In single heavy metal systems, chloro- and hydroxy-pyromorphite (Pb5(PO4)3(Cl,OH)), sodalite (Na6Zn6(PO4)6·8H2O), chiral zincophosphate (Na12(Zn12P12O48)·12H2O), and copper phosphate hydrate (Cu3(PO4)2·3H2O) were the primary phosphate minerals that formed, and were typically stable during the experiment. Zinc and Cu-phosphate formation was reduced in multi heavy metal systems, and was substantially lower in abundance than chloropyromorphite. Successful Cu-, Pb- and Zn-phosphate formation can be expected in cold and freezing environments like the polar regions. However, field implementation of orthophosphate fixation needs to consider competing ion effects, concentration of the phosphate source, and the amount of free-water.
Afficher plus [+] Moins [-]Critical evaluation of a new passive exchange-meter for assessing multimedia fate of persistent organic pollutants at the air-soil interface Texte intégral
2013
Liu, Xiang | Ming, Li-Li | Nizzetto, Luca | Borgå, Katrine | Larssen, Thorjørn | Zheng, Qian | Li, Jun | Zhang, Gan
A new passive exchange meter (PEM) to measure inter-compartment fluxes of persistent organic pollutants (POPs) at the interface between soil and the atmosphere is described. The PEM uses labeled reference compounds (RC) added in-situ to vegetation litter deployed in open cylinders designed to trap the vertical downward export of the RCs while allowing free exchange of POPs between litter and air. Fluxes of native compounds (bulk deposition, volatilization and downward export) are quantitatively tracked. One scope of the PEM is to investigate the influence of biogeochemical controls on contaminant re-mobilization. The PEM performance was tested in a subtropical forest by comparing measurements under dense canopy and in a canopy gap; conditions in which deposition and turn-over of organic matter (OM) occur at different rates. Significant differences in fate processes were successfully detected. Surprisingly, mobilization by leaching of more hydrophobic compounds was higher under canopy, possibly as a result of canopy mediated enhancement of OM degradation.
Afficher plus [+] Moins [-]Limited transport of functionalized multi-walled carbon nanotubes in two natural soils Texte intégral
2013
Kasel, Daniela | Bradford, Scott A. | Šimůnek, Jiří | Pütz, Thomas | Vereecken, H. (Harry) | Klumpp, Erwin
Column experiments were conducted in undisturbed and in repacked soil columns at water contents close to saturation (85–96%) to investigate the transport and retention of functionalized 14C-labeled multi-walled carbon nanotubes (MWCNT) in two natural soils. Additionally, a field lysimeter experiment was performed to provide long-term information at a larger scale. In all experiments, no breakthrough of MWCNTs was detectable and more than 85% of the applied radioactivity was recovered in the soil profiles. The retention profiles exhibited a hyper-exponential shape with greater retention near the column or lysimeter inlet and were successfully simulated using a numerical model that accounted for depth-dependent retention. In conclusion, results indicated that the soils acted as a strong sink for MWCNTs. Little transport of MWCNTs is therefore likely to occur in the vadose zone, and this implies limited potential for groundwater contamination in the investigated soils.
Afficher plus [+] Moins [-]Plant Species Sensitivity Distributions for ozone exposure Texte intégral
2013
van Goethem, T.M.W.J. | Azevedo, L.B. | van Zelm, R. | Hayes, F. | Ashmore, M.R. | Huijbregts, M.A.J.
This study derived Species Sensitivity Distributions (SSD), representing a cumulative stressor-response distribution based on single-species sensitivity data, for ozone exposure on natural vegetation. SSDs were constructed for three species groups, i.e. trees, annual grassland and perennial grassland species, using species-specific exposure–response data. The SSDs were applied in two ways. First, critical levels were calculated for each species group and compared to current critical levels for ozone exposure. Second, spatially explicit estimates of the potentially affected fraction of plant species in Northwestern Europe were calculated, based on ambient ozone concentrations. We found that the SSD-based critical levels were lower than for the current critical levels for ozone exposure, with conventional critical levels for ozone relating to 8–20% affected plant species. Our study shows that the SSD concept can be successfully applied to both derive critical ozone levels and estimate the potentially affected species fraction of plant communities along specific ozone gradients.
Afficher plus [+] Moins [-]Correlation analysis of the urban heat island effect and the spatial and temporal distribution of atmospheric particulates using TM images in Beijing Texte intégral
2013
Xu, L.Y. | Xie, X.D. | Li, S.
This study combines the methods of observation statistics and remote sensing retrieval, using remote sensing information including the urban heat island (UHI) intensity index, the normalized difference vegetation index (NDVI), the normalized difference water index (NDWI), and the difference vegetation index (DVI) to analyze the correlation between the urban heat island effect and the spatial and temporal concentration distributions of atmospheric particulates in Beijing. The analysis establishes (1) a direct correlation between UHI and DVI; (2) an indirect correlation among UHI, NDWI and DVI; and (3) an indirect correlation among UHI, NDVI, and DVI. The results proved the existence of three correlation types with regional and seasonal effects and revealed an interesting correlation between UHI and DVI, that is, if UHI is below 0.1, then DVI increases with the increase in UHI, and vice versa. Also, DVI changes more with UHI in the two middle zones of Beijing.
Afficher plus [+] Moins [-]Upwind impacts of ammonia from an intensive poultry unit Texte intégral
2013
Jones, L. | Nizam, M.S. | Reynolds, B. | Bareham, S. | Oxley, E.R.B.
This study investigated potential ammonia impacts on a sand dune nature reserve 600 m upwind of an intensive poultry unit. Ammonia concentrations and total nitrogen deposition were measured over a calendar year. A series of ammonia and nitrogen exposure experiments using dune grassland species were conducted in controlled manipulations and in the field. Ammonia emissions from the intensive poultry unit were detected up to 2.8 km upwind, contributing to exceedance of critical levels of ammonia 800 m upwind and exceedance of critical loads of nitrogen 2.8 km upwind. Emissions contributed 30% of the total N load in parts of the upwind conservation site. In the nitrogen exposure experiments, plants showed elevated tissue nitrogen contents, and responded to ammonia concentrations and nitrogen deposition loads observed in the conservation site by increasing biomass. Estimated long-term impacts suggest an increase in the soil carbon pool of 9% over a 50-year timescale.
Afficher plus [+] Moins [-]Application of MicroResp™ for soil ecotoxicology Texte intégral
2013
Wakelin, Steven | Lombi, Enzo | Donner, Erica | MacDonald, Lynne | Black, Amanda | O'Callaghan, Maureen
MicroResp™ is a miniaturised method for measuring substrate induced respiration (SIR) in soil. We modified the MicroResp™ method to develop a rapid tool for quantifying the ecotoxicological impact of contaminants. The method is based on reduction in SIR across a gradient of contaminant, allowing for determination of dose–response curves EC-values. Contaminants are mixed into soil samples at a range of concentrations; each sample is then dispensed into a column of eight wells in 96 well format (deep) plates. Moisture and glucose are added to the samples at levels to provide maximum response. Released CO2 from the soils is then measured using colorimetric gel-traps, following the standard MicroResp™ methodology. Examination revealed that this method works over a range of soil types and is insensitive to minor variations in assay length (2–7 h), alteration of moisture content (±20 μL from optimum), and soil storage conditions (4 °C versus fresh).
Afficher plus [+] Moins [-]Initial transport and retention behaviors of ZnO nanoparticles in quartz sand porous media coated with Escherichia coli biofilm Texte intégral
2013
Jiang, Xujia | Wang, Xueting | Tong, Meiping | Kim, Hyŏn-jŏng
The significance of biofilm on the transport and deposition behaviors of ZnO nanoparticles were examined under a series of environmentally relevant ionic strength at two fluid velocities of 4 m-d−1 and 8 m-d−1. Biofilm enhanced nanoparticles retention in porous media under all examined conditions. The greater deposition was also observed in extracellular polymeric substances (EPS) coated surfaces by employment of quartz microbalance with dissipation (QCM-D) system. Derjaguin–Landau–Verwey–Overbeek (DLVO) failed to interpret more ZnO nanoparticles deposition on biofilm (EPS) coated silica surfaces. Chemical interaction and physical morphology of biofilm contributed to this greater deposition (retention). Biofilm affected the spacial distribution of retained ZnO nanoparticles as well. Relatively steeper slope of retained profiles were observed in the presence of biofilm, corresponding to the greater deviation from colloid filtration theory (CFT). Pore space constriction via biofilm induced more nanoparticle trapped in the column inlet, leading to greater deviations (σln kf) from the CFT.
Afficher plus [+] Moins [-]Ultra-sensitive conductometric detection of pesticides based on inhibition of esterase activity in Arthrospira platensis Texte intégral
2013
Tekaya, Nadèje | Saiapina, Olga | Ben Ouada, Hatem | Lagarde, Florence | Ben Ouada, Hafedh | Jaffrezic-Renault, N. (Nicole)
Enzymatic conductometric biosensor, using immobilized Arthrospira platensis cells on gold interdigitated electrodes, for the detection of pesticides in water, was elaborated. Cholinesterase activity (AChE) was inhibited by pesticides and a variation of the local conductivity was measured after addition of the substrate acetylthiocholine chloride (AChCl). The Michaelis–Menten constant (Km) was evaluated to be 1.8 mM through a calibration curve of AChCl. Inhibition of AChE was observed with paraoxon-methyl, parathion-methyl, triazine and diuron with a detection limit of 10−18 M, 10−20 M, 10−20 M and 10−12 M, respectively and the half maximal inhibitory concentration (IC50) was determined at 10−16 M, 10−20 M, 10−18 M and 10−06 M, respectively. An important decrease of response time τ90% was recorded for AChE response towards AChCl after 30 min cell exposure to pesticides. Scanning electron microscopy images revealed a degradation of the cell surface in presence of pesticides at 10−06 M.
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