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Berlin Brandenburg

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  • 1
    Language: English
    In: Environmental science & technology, 2013, Vol.47(21), pp.12229-37
    Description: Column experiments were conducted with undisturbed loamy sand soil under unsaturated conditions (around 90% saturation degree) to investigate the retention of surfactant stabilized silver nanoparticles (AgNPs) with various input concentration (Co), flow velocity, and ionic strength (IS), and the remobilization of AgNPs by changing the cation type and IS. The mobility of AgNPs in soil was enhanced with decreasing solution IS, increasing flow rate and input concentration. Significant retardation of AgNP breakthrough and hyperexponential retention profiles (RPs) were observed in almost all the transport experiments. The retention of AgNPs was successfully analyzed using a numerical model that accounted for time- and depth-dependent retention. The simulated retention rate coefficient (k1) and maximum retained concentration on the solid phase (Smax) increased with increasing IS and decreasing Co. The high k1 resulted in retarded breakthrough curves (BTCs) until Smax was filled and then high effluent concentrations were obtained. Hyperexponential RPs were likely caused by the hydrodynamics at the column inlet which produced a concentrated AgNP flux to the solid surface. Higher IS and lower Co produced more hyperexponential RPs because of larger values of Smax. Retention of AgNPs was much more pronounced in the presence of Ca(2+) than K(+) at the same IS, and the amount of AgNP released with a reduction in IS was larger for K(+) than Ca(2+) systems. These stronger AgNP interactions in the presence of Ca(2+) were attributed to cation bridging. Further release of AgNPs and clay from the soil was induced by cation exchange (K(+) for Ca(2+)) that reduced the bridging interaction and IS reduction that expanded the electrical double layer. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, and correlations between released soil colloids and AgNPs indicated that some of the released AgNPs were associated with the released clay fraction.
    Keywords: Metal Nanoparticles -- Chemistry ; Silver -- Chemistry ; Soil -- Chemistry
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 2
    Language: English
    In: Environmental science & technology, 06 December 2016, Vol.50(23), pp.12713-12721
    Description: Transport and retention behavior of multi-walled carbon nanotubes (MWCNTs) was studied in mixtures of negatively charged quartz sand (QS) and positively charged goethite-coated sand (GQS) to assess the role of chemical heterogeneity. The linear equilibrium sorption model provided a good description of batch results, and the distribution coefficients (K) drastically increased with the GQS fraction that was electrostatically favorable for retention. Similarly, retention of MWCNTs increased with the GQS fraction in packed column experiments. However, calculated values of K on GQS were around 2 orders of magnitude smaller in batch than packed column experiments due to differences in lever arms associated with hydrodynamic and adhesive torques at microscopic roughness locations. Furthermore, the fraction of the sand surface area that was favorable for retention (S) was much smaller than the GQS fraction because nanoscale roughness produced shallow interactions that were susceptible to removal. These observations indicate that only a minor fraction of the GQS was favorable for MWCNT retention. These same observations held for several different sand sizes. Column breakthrough curves were always well described using an advective-dispersive transport model that included retention and blocking. However, depth-dependent retention also needed to be included to accurately describe the retention profile when the GQS fraction was small. Results from this research indicate that roughness primarily controlled the retention of MWCNTs, although goethite surfaces played an important secondary role.
    Keywords: Quartz ; Nanotubes, Carbon -- Ultrastructure
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 3
    Language: English
    In: Environmental science & technology, 15 June 2011, Vol.45(12), pp.5216-22
    Description: Veterinary antibiotics introduced into the environment may change the composition and functioning of soil microbial communities and promote the spreading of antibiotic resistance. Actual risks depend on the antibiotic's persistence and (bio)accessibility, which may differ between laboratory and field conditions. We examined the dissipation and sequestration of sulfadiazine (SDZ) and its main metabolites in soil under field conditions and how it was influenced by temperature, soil moisture, plant roots, and soil aggregation compared to controlled laboratory experiments. A sequential extraction accounted for easily extractable (CaCl₂-extractable) and sequestered (microwave-extractable, residual) SDZ fractions. Dissipation from both fractions was largely temperature-dependent and could be well predicted from laboratory data recorded at different temperatures. Soil moisture additionally seemed to control sequestration, being accelerated in dry soil. Sequestration, as indicated by increasing apparent distribution coefficients and decreasing rates of kinetic release into CaCl₂, governed the antibiotic's long-term fate in soil. Besides, we observed spatial gradients of antibiotic concentrations across soil aggregates and in the vicinity of roots. The former were short-lived and equilibrated due to aggregate reorganization, while dissipation of the easily extractable fraction was accelerated near roots throughout the growth period. There was little if any impact of the plants on residual SDZ concentrations.
    Keywords: Anti-Bacterial Agents -- Isolation & Purification ; Environmental Restoration and Remediation -- Methods ; Sulfadiazine -- Analogs & Derivatives ; Veterinary Drugs -- Analogs & Derivatives
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 4
    Language: English
    In: Environmental science & technology, 01 November 2010, Vol.44(21), pp.8102-7
    Description: Sorption of pyrene and phenanthrene to model (illite and charcoal) and natural (Yangtze sediment) geosorbents were investigated by batch techniques using fluorescence spectroscopy. A higher adsorption of phenanthrene was observed with all sorbents, which is related to the better accessibility of smaller molecules to micropores in the molecular sieve sorbents. In addition, pyrene sorption in binary-solute systems with a constant initial concentration of phenanthrene (0.1 μmol L(-1) or 2 μmol L(-1)) was studied. A 0.1 μmol L(-1) concentration of phenanthrene causes no competitive effect on the pyrene sorption. A 2 μmol L(-1) concentration of phenanthrene significantly suppresses the sorption of pyrene, especially in the low concentration range; nonlinearity of the pyrene sorption isotherms thus decreases. The competitive effect of 2 μmol L(-1) phenanthrene on the pyrene sorption is overestimated by the ideal adsorbed solution theory (IAST) using the fitted single sorption results of both solutes. An adjustment of the IAST application by taking into account the molecular sieve effect is proposed, which notably improves the IAST prediction for the competitive effect.
    Keywords: Models, Chemical ; Phenanthrenes -- Chemistry ; Pyrenes -- Chemistry
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 5
    Language: English
    In: Environmental science & technology, 15 June 2010, Vol.44(12), pp.4651-7
    Description: The worldwide use of veterinary antibiotics poses a continuous threat to the environment. There is, however, a lack of mechanistic studies on sorption and transformation processes for environmental assessment in soils. Two-week batch sorption experiments were performed with the antibiotic sulfadiazine (SDZ) in the plow layer and the subsoil of a loamy sand and a silty loam. The sorption and transformation parameters of SDZ and its main transformation products N1-2-(4-hydroxypyrimidinyl) benzenesulfanilamide (4-OH-SDZ) and 4-(2-iminopyrimidin-1(2H)-yl)aniline (An-SDZ) were estimated using a global optimization algorithm. A two-stage, one-rate sorption model combined with a first-order transformation model adequately described the batch data. Sorption of SDZ was nonlinear, time-dependent, and affected by pH, with a higher sorption capacity for the loamy sand. Transformation of SDZ into 4-OH-SDZ occurred only in the liquid phase, with half-life values of 1 month in the plow layers and 6 months in the subsoils. Under the exclusion of light, An-SDZ was formed in substantial amounts in the silty loam only, with liquid phase half-life values of 2 to 3 weeks. Despite the rather large parameter uncertainties, which may be reduced using additional information obtained from sequential solid phase extraction, the proposed method provides a framework to assess the fate of antibiotics in soils.
    Keywords: Environmental Restoration and Remediation -- Methods ; Soil -- Analysis ; Sulfadiazine -- Isolation & Purification ; Veterinary Drugs -- Isolation & Purification
    ISSN: 0013-936X
    E-ISSN: 15205851
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  • 6
    Language: English
    In: Environmental science & technology, 15 May 2004, Vol.38(10), pp.2885-93
    Description: Calculation of pesticide volatilization from plants as an integral component of pesticide fate models is of utmost importance, especially as part of PEC (predicted environmental concentrations) models used in the registration procedures for pesticides. A mechanistic approach using a laminar air-boundary layer concept to predict volatilization from plant surfaces was compared to data obtained in a wind-tunnel study after simultaneous application of parathion-methyl, fenpropimorph, and quinoxyfen to winter wheat. Parathion-methyl was shown to have the highest volatilization during the wind-tunnel study of 10 days (29.2%). Volatilization of quinoxyfen was about 15.0%, revealing a higher volatilization tendency than fenpropimorph (6.0%), which is attributed to enhanced penetration of fenpropimorph counteracting volatilization. Predictions of the boundary-layer approach were markedly influenced by the selected values for the equivalent thickness of the boundary layer and rate coefficients, thus indicating that future improvements of the approach will require a deeper understanding of the kinetics of the underlying processes, e.g. phototransformation and penetration. The boundary-layer volatilization module was included in the European registration model PELMO, enabling simultaneous calculation of volatilization from plants and soil. Application of PELMO to experimental findings were the first comprehensive PEC model calculations to imply the relevant processes affecting the postapplication fate of pesticides.
    Keywords: Fungicides, Industrial -- Analysis ; Insecticides -- Analysis ; Methyl Parathion -- Analysis ; Morpholines -- Analysis ; Plants -- Chemistry ; Quinolines -- Analysis
    ISSN: 0013-936X
    E-ISSN: 15205851
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  • 7
    Language: English
    In: Environmental science & technology, 01 July 2008, Vol.42(13), pp.4870-6
    Description: The need to determine soil-air partitioning coefficients (K(SA)) of low-volatility organic chemicals as a measure of their distribution in the soil surface after release into the environment resulted in the development of a novel chamber system, which has been filed for patent. A major advantage of this pseudo-static system is that sufficient time can be factored into the experiment to ensure that the system has achieved equilibrium. In a highly precise method, the air is collected in adsorption tubes and subsequently liberated in a thermodesorption system for the quantitation of the adsorbed compound. The precision of the method is great enough that even the effects of temperature and soil moisture on the soil-air partitioning of very low-volatility compounds can be quantified. Because of analytical detection limits, quantitation of these influences has not been possible to date. Functionality of the setup was illustrated by measurements on the fungicide fenpropimorph. K(SA) values of fenpropimorph displayed a negative relationship with temperature and soil moisture. The type of application (spraying or incorporation) and the use of formulated compounds was shown to have a major impact on the measured K(SA) values. Comparison with calculations using an estimation method revealed that the use of experimentally determined K(SA) values will facilitate a more adequate consideration of volatilization in recent model approaches.
    Keywords: Temperature ; Environmental Monitoring -- Instrumentation ; Environmental Pollutants -- Analysis ; Organic Chemicals -- Analysis ; Soil -- Analysis
    ISSN: 0013-936X
    E-ISSN: 15205851
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