The Experts below are selected from a list of 1608 Experts worldwide ranked by ideXlab platform

Lixiang Zhou - One of the best experts on this subject based on the ideXlab platform.

  • cadmium transport mediated by Soil Colloid and dissolved organic matter a field study
    Journal of Environmental Sciences-china, 2010
    Co-Authors: Lixiang Zhou
    Abstract:

    This study investigated the potential role of Soil Colloids and dissolved organic matter (DOM) in transporting Cd through in situ undisturbed paddy Soil monoliths. Brilliant Blue was used as a tracer to assess the effect of preferential flow on Cd down migration. Experimental results showed that deep penetration of Cd and Brilliant Blue into the Soil profile took place due to the preferential flow through macropores, mainly earthworm channels, with much of chemicals thus bypassing the Soil matrix. Dye tracer and Cd distribution within the Soil matrix was fairly restricted to several centimeters. Colloid restrained the migration of both dye and Cd in the matrix and preferential flow area. DOM facilitated the transport of Cd and Brilliant Blue in matrix and macropores by about 10 cm over that of the control. Pearson's is correlation analysis revealed strong associations between Brilliant Blue concentrations, exchangeable Cd and total Cd concentrations in three studied plots indicating that they had taken the same preferential flow pathway.

Jesus Simalgandara - One of the best experts on this subject based on the ideXlab platform.

  • effect of organic matter and iron oxides on quaternary herbicide sorption desorption in vineyard devoted Soils
    Journal of Colloid and Interface Science, 2009
    Co-Authors: Mirian Pateiromoure, Cristina Pereznovo, Manuel Ariasestevez, R Rialotero, Jesus Simalgandara
    Abstract:

    Abstract Herbicide Soil/solution distribution coefficients ( K d ) are used in mathematical models to predict the movement of herbicides in Soil and groundwater. Herbicides bind to various Soil constituents to differing degrees. The universal Soil Colloid that binds most herbicides is organic matter; however metallic hydrous oxides might also have some influence. The adsorption–desorption of three quaternary ammonium herbicides on Soils with different chemical–physical characteristics was determined using a batch equilibration method before and after the following sequential selective dissolution procedures: removal of organic matter, and removal of organic matter plus free iron oxides. The experimentation involved paraquat (PQ), diquat (DQ) and difenzoquat (DFQ) herbicides. The distribution coefficients ( K d ) of the molecules and their correlation to the Soil components were determined and a significant negative correlation with organic carbon was highlighted ( r − 0.610 , p 0.035 , n = 12 ). All quats cations experiment high adsorption in the control Soils with a Zeta potential at about −21 mV. The order of adsorption on Soils (based on K d ) was the following: PQ > DQ ≫ DFQ. The adsorption isotherms of these three herbicides on the natural and processed Soils were satisfactorily fitted with the Freundlich equation, and a significant correlation with organic carbon was highlighted for quats K F ( r − 0.696 , p 0.012 , n = 12 ). The removal of organic matter from Soils seems to leave free new adsorption sites for quats on the clay surface, which is no longer occluded by organic matter. This work shows that the amount and nature of the surface that remains available after the removal of single Soil constituents is a critical parameter in determining the sorptive behavior of cationic contaminants.

Wenli Chen - One of the best experts on this subject based on the ideXlab platform.

  • Soil Colloids bound plasmid dna effect on transformation of e coli and resistance to dnase i degradation
    Soil Biology & Biochemistry, 2007
    Co-Authors: Peng Cai, Qiaoyun Huang, Wenli Chen, D Zhang, K Wang, Daihua Jiang, Wei Liang
    Abstract:

    Abstract The adsorption and binding of plasmid p34S DNA on four different Colloidal fractions from a Brown Soil and clay minerals in the presence of various Ca 2+ concentrations, the ability of bound DNA to transform competent cells of CaCl 2 -treated Escherichia coli , and the resistance of bound DNA to degradation by DNase I were studied. DNA adsorption on Soil Colloids and clay minerals was promoted in the presence of Ca 2+ . Kaolinite exhibited the highest adsorption affinity for DNA among the examined Soil Colloids and clay minerals. In comparison with organo-mineral complexes (organic clays) and fine clays ( 2 O 2 -treated clays (inorganic clays) and coarse clays (0.2–2 μm). The transformation efficiency of bound DNA increased with increasing concentrations of Ca 2+ at which Soil Colloid or clay mineral-DNA complexes were formed. DNA bound by kaolinite showed the lowest transformation efficiency, and especially no transformants were observed with kaolinite-DNA complex prepared at 5–100 mM Ca 2+ . Compared to organic clays and fine clays, DNA bound on inorganic clays and coarse clays showed a lower capacity to transform E. coli at different Ca 2+ concentrations. The presence of Soil Colloids and minerals provided protection to DNA against degradation by DNase I. Montmorillonite, organic clays and fine clays showed stronger protective effects for DNA than inorganic clays and coarse clays. The protection mechanisms as well as the differences in transforming efficiency of plasmid DNA molecules bound on various Soil Colloidal particles are discussed. The information obtained in this study is of fundamental significance for the understanding of the horizontal dissemination of recombinant DNA and the fate of extracellular DNA in Soil environments.

  • adsorption of copper and cadmium by cu and cd resistant bacteria and their composites with Soil Colloids and kaolinite
    Geomicrobiology Journal, 2005
    Co-Authors: Qiaoyun Huang, Wenli Chen
    Abstract:

    Abstract Remediation of toxic metals by bacteria offers a relatively inexpensive and efficient way for the decontamination of Soil and associated environments. The present study was carried out to investigate the surface characteristics, adsorption, and remobilization of Cd and Cu on bacteria and their composites with Soil Colloidal components, which are the most active constituents in Soils. The bacterial strain NTG-01 (Enterobacter aerogenes), which was both Cd- and Cu-resistant, was isolated from a heavily Cu-contaminated Soil of the mining area in Daye suburb of Hubei Province, China. Batch laboratory experiments with NTG-01 and Soil Colloids were performed to quantify adsorption of Cu and Cd. The surface area of kaolinite and the Soil Colloids from an Alfisol and Ultisol increased by 3.0–8.8% after the introduction of the bacteria. In the presence of bacterial cells, the negative charges of Soil Colloid systems increased and the positive charges decreased, shifting pH from 4.0 to 6.5. Our results dem...

Erwin Klumpp - One of the best experts on this subject based on the ideXlab platform.

  • role of rain intensity and Soil Colloids in the retention of surfactant stabilized silver nanoparticles in Soil
    Environmental Pollution, 2018
    Co-Authors: Joanna Makselon, Nina Siebers, Florian Meier, Harry Vereecken, Erwin Klumpp
    Abstract:

    Abstract Undisturbed outdoor lysimeters containing arable loamy sand Soil were used to examine the influence of either heavy rain events (high frequency of high rain intensity), steady rain (continuous rainfall of low rain intensity), and natural rainfall on the transport and retention of surfactant-stabilized silver nanoparticles (AgNP). In addition, the AgNP–Soil associations within the Ap horizon were analyzed by means of particle-size fractionation, asymmetrical flow field-flow fractionation coupled with UV/Vis-detection and inductively coupled plasma mass spectrometer (AF4-UV/Vis-ICP-MS), and transmission electron microscopy coupled to an energy-dispersive X-ray (TEM-EDX) analyzer. The results showed that AgNP breakthrough for all rain events was less than 0.1% of the total AgNP mass applied, highlighting that nearly all AgNP were retained in the Soil. Heavy rain treatment and natural rainfall revealed enhanced AgNP transport within the Ap horizon, which was attributed to the high pore water flow velocities and to the mobilization of AgNP–Soil Colloid associations. Particle-size fractionation of the Soil revealed that AgNP were present in each size fraction and therefore indicated strong associations between AgNP and Soil. In particular, water-dispersible Colloids (WDC) in the size range of 0.45–0.1 μm were found to exhibit high potential for AgNP attachment. The AF4-UV/Vis-ICP-MS and TEM-EDX analyses of the WDC fraction confirmed that AgNP were persistent in Soil and associated to Soil Colloids (mainly composed of Al, Fe, Si, and organic matter). These results confirm the particularly important role of Soil Colloids in the retention and remobilization of AgNP in Soil. Furthermore, AF4-UV/Vis-ICP-MS results indicated the presence of single, homo-aggregated, and small AgNP probably due to dissolution.

  • roles of cation valance and exchange on the retention and Colloid facilitated transport of functionalized multi walled carbon nanotubes in a natural Soil
    Water Research, 2017
    Co-Authors: Harry Vereecken, Miaoyue Zhang, Scott A Bradford, Jirka Simůnek, Erwin Klumpp
    Abstract:

    Abstract Saturated Soil column experiments were conducted to investigate the transport, retention, and release behavior of a low concentration (1 mg L−1) of functionalized 14C-labeled multi-walled carbon nanotubes (MWCNTs) in a natural Soil under various solution chemistries. Breakthrough curves (BTCs) for MWCNTS exhibited greater amounts of retardation and retention with increasing solution ionic strength (IS) or in the presence of Ca2+ in comparison to K+, and retention profiles (RPs) for MWCNTs were hyper-exponential in shape. These BTCs and RPs were well described using the advection-dispersion equation with a term for time- and depth-dependent retention. Fitted values of the retention rate coefficient and the maximum retained concentration of MWCNTs were higher with increasing IS and in the presence of Ca2+ in comparison to K+. Significant amounts of MWCNT and Soil Colloid release was observed with a reduction of IS due to expansion of the electrical double layer, especially following cation exchange (when K+ displaced Ca2+) that reduced the zeta potential of MWCNTs and the Soil. Analysis of MWCNT concentrations in different Soil size fractions revealed that >23.6% of the retained MWCNT mass was associated with water-dispersible Colloids (WDCs), even though this fraction was only a minor portion of the total Soil mass (2.38%). More MWCNTs were retained on the WDC fraction in the presence of Ca2+ than K+. These findings indicated that some of the released MWCNTs by IS reduction and cation exchange were associated with the released clay fraction, and suggests the potential for facilitated transport of MWCNT by WDCs.

Anzhen Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Interaction between electrical double layers of Soil Colloids and Fe/Al oxides in suspensions.
    Journal of colloid and interface science, 2007
    Co-Authors: Tao Hou, Diwakar Tiwari, Anzhen Zhao
    Abstract:

    Phyllosilicates with net negative surface charge and Fe/Al oxides with net positive surface charge coexist in variable-charge Soils, and the interaction between these oppositely charged particles affects the stability of mixed Colloids, aggregation, and even the surface chemical properties of variable-charge Soils. The interaction of the diffuse layers of electrical double layers between the negatively charged Soil Colloidal particles and the positively charged particles of goethite or gamma-Al(2)O(3) was investigated in this article through the comparison of zeta potentials between single-Soil Colloidal systems and binary systems containing Soil Colloids and Fe/Al oxides. The results showed that the presence of goethite and gamma-Al(2)O(3) increased the zeta potential of the binary system containing Soil Colloids and Fe/Al oxides, which clearly suggests the overlapping of the diffuse layers in Soil Colloids and Fe/Al oxides. The overlapping of the diffuse layers leads to a decrease in the effective negative charge density on Soil Colloid and thus causes a shift of pH-zeta potential curves toward the more positive-value side. The interaction of the electrical double layers is also related to the charge characteristics on the Fe/Al oxides: the higher the positive charge density on Fe/Al oxides, the stronger the interaction of the electrical double layers between the Soil Colloid particles and the Fe/Al oxides.

  • long range effect of electric charge of ion exchange resin and Soil Colloid on potential of ion selective electrodes
    Journal of Colloid and Interface Science, 2001
    Co-Authors: Anzhen Zhao
    Abstract:

    Abstract The effect of electric charge of ion-exchange resin and Soil Colloid on potential of ion-selective electrodes was investigated. It was found that the potential of ion-selective electrodes could be affected by the ion-exchange resin membrane or Soil mass even when the sensitive membrane of the electrode was located at a distance of 2–3 mm from the latter. The potential was related to the kind of the electrode, the kind of the charged material that could induce such an effect, the concentration of the electrolyte, and the distance between the sensitive membrane of the electrode and the ion-exchange resin membrane or Soil mass. It was suggested that the potential of ion-selective electrodes might be quite sensitive to minor changes in electric field or some of its derivative properties and that the effect was not only related to the electric charge of the ion-exchange resin or Soil Colloid, but also related to some electrochemical properties of the sensitive membrane of the electrode. In order to avoid possible errors caused by this long-range effect of electric charge of Colloids on the potential of ion-selective electrodes in potentiometric measurements, the electrode should be located as far from the charged particles as possible.