Black carbon (BC), characterized by high microporosity and high specific surface area (SSA), has been demonstrated to have substantial contributions to the sorption of hydrophobic organic chemicals in soils and sediments. Other naturally... more
Black carbon (BC), characterized by high microporosity and high specific surface area (SSA), has been demonstrated to have substantial contributions to the sorption of hydrophobic organic chemicals in soils and sediments. Other naturally occurring organic matters provide soft and penetrable sorption domains while may cling to BC and affect its original surface properties. In this work, we studied the sorption sites of a Yangtze River sediment sample with organic carbon (OC) content of 3.3 % and the preheated sediment (combusted at 375 °C) with reduced OC content (defined as BC) of 0.4 % by gas and pyrene sorption. The SSA and microporosity of the pristine and preheated sediments were characterized by N2 and CO2 adsorption. The results suggest that the adsorption of N2 was hindered by amorphous organic carbon (AOC) in the pristine sediment but CO2 was not. Instead, the uptake of CO2 was higher in the presence of AOC, likely due to the partition of CO2 molecules into the organic matter. The pyrene adsorptions to BC in pristine and preheated sediments show a similar adsorption capacity at high concentration, suggesting that AOC of ca. 2.9 % in the pristine sediment does not reduce the accessibility to the sorption sites on BC for pyrene.
Research Interests:
Research Interests:
... This small microcell needs only 0.08 ml of sample. ... where os -- 2~tc,)~ (in cm -1) is the frequency of the scattered light, cos = mL -- 0)R; O)L: incident laser frequency; COR: Raman active normal mode excited by the inelastic ...... more
... This small microcell needs only 0.08 ml of sample. ... where os -- 2~tc,)~ (in cm -1) is the frequency of the scattered light, cos = mL -- 0)R; O)L: incident laser frequency; COR: Raman active normal mode excited by the inelastic ... Surface Enhanced Raman Scattering of Biomolecules ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Black carbon (BC), characterized by high microporosity and high specific surface area (SSA), has been demonstrated to have substantial contributions to the sorption of hydrophobic organic chemicals in soils and sediments. Other naturally... more
Black carbon (BC), characterized by high microporosity and high specific surface area (SSA), has been demonstrated to have substantial contributions to the sorption of hydrophobic organic chemicals in soils and sediments. Other naturally occurring organic matters provide soft and penetrable sorption domains while may cling to BC and affect its original surface properties. In this work, we studied the sorption sites of a Yangtze River sediment sample with organic carbon (OC) content of 3.3 % and the preheated sediment (combusted at 375 °C) with reduced OC content (defined as BC) of 0.4 % by gas and pyrene sorption. The SSA and microporosity of the pristine and preheated sediments were characterized by N2 and CO2 adsorption. The results suggest that the adsorption of N2 was hindered by amorphous organic carbon (AOC) in the pristine sediment but CO2 was not. Instead, the uptake of CO2 was higher in the presence of AOC, likely due to the partition of CO2 molecules into the organic matter. The pyrene adsorptions to BC in pristine and preheated sediments show a similar adsorption capacity at high concentration, suggesting that AOC of ca. 2.9 % in the pristine sediment does not reduce the accessibility to the sorption sites on BC for pyrene.
Research Interests:
Research Interests:
Research Interests:
ABSTRACT The surface area and pore structure of easily dispersed soil particles < 2 μm in size (water-dispersible colloids, WDCs) are important for carbon sequestration and transport in soil, two processes which are essential for... more
ABSTRACT The surface area and pore structure of easily dispersed soil particles < 2 μm in size (water-dispersible colloids, WDCs) are important for carbon sequestration and transport in soil, two processes which are essential for the terrestrial carbon cycling. In this work, we determine the effects of dithionite–citrate–bicarbonate (DCB) extractable metal oxides, and oxalate extractable metal oxides on the specific surface area (SSA) and pore structure of WDCs from silt loam topsoils of three TERENO test sites with a similar clay content (20%) in Germany (arable (Selhausen), grassland (Rollesbroich) and forest (Wuestebach) soils). The N2 gas-adsorption (− 196 °C), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and microelectrophoretic (ME) methods were used and compared. Results show that 1) the SSA of the WDCs from Selhausen, Rollesbroich, and Wuestebach decreased more after DCB treatment (27%, 35%, and 44%) than after oxalate treatment (5%, 14%, and 22%). DCB removed metal oxide nanoparticles from WDCs were found to have diameters (dp) ranging from 4 nm to 8 nm and the surface loading ratios on the surface of aluminosilicate residues in WDCs were estimated to be 11% to 22% for three soils where the highest value was found in the acidic forest soil. 2) Pore sizes in the mesopore range (2 nm to 50 nm) were analyzed in the WDC fractions. The results were discussed in terms of accessible open pores for the pristine WDCs and WDC samples from which metal oxide nanoparticles and organic carbon (OC) had been removed. The lower average pore radius (Rp) measured by the N2 gas-adsorption method based on the total volume (Vt) to SSA ratio variations in WDCs without metal oxides compared to WDC with metal oxides indicated a contraction of the porous structure of WDCs due to the presence of metal oxide nanoparticles. The pore size distribution (PSD) analysis showed a sensitive contribution of metal oxide nanoparticles in the low range of pore sizes (< 25 nm) of WDCs. In SAXS measurements, higher surface fractal dimensions (Ds) were observed in WDCs before the metal oxide's removal, which supports a roughness increase of the interfaces in the presence of nanoparticles. The colloidal characterization of WDCs by the DLS and ME methods shows, at a μm scale, the role of positively charged metal oxide nanoparticles in forming WDCs with a more compact structure by decreasing the particle size (dz) and the negative zeta potential (ζ). 3) The comparison of Rp, k, dz and dp results between different soils also indicates the dependence on the clay mineralogy of WDCs so that the heterocoagulation between kaolinite and illite (clay minerals of different aspect ratios) increases the size of soil mesopores (Rollesbroich). In conclusion, the results of this study clearly show that the combination of the N2 gas-adsorption, SAXS, DLS and ME methods allows the characterization of soil porosity in the nanometer range where metal oxide nanoparticles contribute to a more compact structure of WDC.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Aggregate size fractionation in combination with chemical extraction was used to assess pesticide interactions with soil organic matter under different soil management practices [1]. In this study, surface area measurements (BET-N2) were... more
Aggregate size fractionation in combination with chemical extraction was used to assess pesticide interactions with soil organic matter under different soil management practices [1]. In this study, surface area measurements (BET-N2) were established as a method to calculate the distribution of organic carbon (OC) and xenobiotics in clay and combined silt+sand fractions. It was shown that concentrations of OC associated
Research Interests:
Humic substances are the predominant components of the organic matter in the terrestrial system, which are not only important for the physicochemical properties of soil but are also dominant factors for controlling the environmental... more
Humic substances are the predominant components of the organic matter in the terrestrial system, which are not only important for the physicochemical properties of soil but are also dominant factors for controlling the environmental behaviors and fates of some organic contaminants, such as hydrophobic compounds. Nonylphenol [4-(1-ethyl-1, 3 dimethylpentyl) phenol] (NP), a ubiquitous hydrophobic pollutant, has recently focused the attention
Research Interests:
Electrochemical methods (direct-current polarography, cyclic voltammetry and differential pulse polarography) were used for analysis of 7-methylguanine nucleosides and nucleotides.
Research Interests:
The importance of BC for the long term sequestration of organic carbon is actually discussed for mitigating climate change. In this context, the role of BC as a filter or source of nutrients or toxic chemicals is questioned. The fate of... more
The importance of BC for the long term sequestration of organic carbon is actually discussed for mitigating climate change. In this context, the role of BC as a filter or source of nutrients or toxic chemicals is questioned. The fate of polycyclic aromatic hydrocarbons (PAHs) is especially concerned. In this study, we have investigated the binding of PAH compounds, pyrene and phenanthrene, to Yangtze River sediments. For this purpose, the PAHs sorption to pristine and preheated sediments at 375°C was studied, which allow discriminating the contributions of amorphous organic carbon (AOC) and black carbon (BC) fractions to the PAH sorption extent. An analytical procedure for the determination of PAHs in the solution phase of the batch experiments has been developed with fluorescence spectroscopy. The PAHs sorption isotherms to pristine sediments were fitted by Freundlich and composite models as linear Langmuir model (LLM) and linear Polanyi-Dubinin-Manes model (LPDMM). The sequential ...
Research Interests:
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... more
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.