Attenuating toluene mobility in loess soil modified with anion-cation surfactants

Soils, subsoils, and aquifer materials can be modified with hydrophobic cationic surfactants to increase their sorption capabilities for organic contaminants. The objective of this study was to examine in detail the sorptive characteristics of the natural loess soil and the resultant organo-modified soils for aqueous-phase neutral organic compounds (NOCs) in an attempt to define the operative sorptive mechanisms. Under the laboratory conditions, a series of modified loess soils in this study were prepared by replacing the cations of loess soil with both cationic surfactant hexadecyltrimethylammonium bromide (HDTMA-Br) and anionic surfactant sodium dodethylbenzene sulfonate (SDBS). Toluene was selected as an indicator to study the sorption behavior of the NOCs in loess soils. The sorption isotherms of toluene in soil samples obtained using the batch equilibration method. The results indicated that natural loess had a poor sorption capability for NOCs, and sorption isotherms of toluene appeared likely nonlinear and fit the Freundlich equation very well. When the soils were coated with large alkyl surfactants such as HDTMA-Br, sorption isotherms correspondingly became linear and the sorptive capability was prominently dependent on the quantity of hexadecyltrimethylammonium (HDTMA) and SDBS added into the soils. The study could provide an essential basis on attenuation of organic contaminants in the subsurface environment.     

Biodegradation of 2,4,6-trichlorophenol in a packed-bed biofilm reactor equipped with an internal net draft tube riser for aeration and liquid circulation

For the aerobic biodegradation of the fungicide and defoliant 2,4,6-trichlorophenol (2,4,6-TCP), a bench-scale packed-bed bioreactor equipped with a net draft tube riser for liquid circulation and oxygenation (PB-ALR) was constructed. To obtain a high packed-bed volume relative to the whole bioreactor volume, a high A(D)/A(R) ratio was used. Reactor's downcomer was packed with a porous support of volcanic stone fragments. PB-ALR hydrodynamics and oxygen mass transfer behavior was evaluated and compared to the observed behavior of the unpacked reactor operating as an internal airlift reactor (ALR). Overall gas holdup values epsilon(G), and zonal oxygen mass transfer coefficients determined at various airflow rates in the PB-ALR, were higher than those obtained with the ALR. When comparing mixing time values obtained in both cases, a slight increment in mixing time was observed when reactor was operated as a PB-ALR. By using a mixed microbial community, the biofilm reactor was used to evaluate the aerobic biodegradation of 2,4,6-TCP. Three bacterial strains identified as Burkholderia sp., Burkholderia kururiensis and Stenotrophomonas sp. constituted the microbial consortium able to cometabolically degrade the 2,4,6-TCP, using phenol as primary substrate. This consortium removed 100% of phenol and near 99% of 2,4,6-TCP. Mineralization and dehalogenation of 2,4,6-TCP was evidenced by high COD removal efficiencies ( approximately 95%), and by the stoichiometric release of chloride ions from the halogenated compound ( approximately 80%). Finally, it was observed that the microbial consortium was also capable to metabolize 2,4,6-TCP without phenol as primary substrate, with high removal efficiencies (near 100% for 2,4,6-TCP, 92% for COD and 88% for chloride ions).     

Compositional and functional features of humic acid-like fractions from vermicomposting of sewage sludge and cow dung

The chemical changes occurring in five different substrates of sewage sludge spiked with different proportions of cow dung after vermicomposting with Eisenia foetida for 90 days were investigated. Their humic acid-like (HAL) fractions were isolated to determine the elemental and functional composition, and structural and functional characteristics using ultraviolet/visible, Fourier transform infrared (FT-IR) and fluorescence spectroscopies and scanning electron microscopy. After vermicomposting, the total organic C and C/N ratio decreased, and the total extractable C and humic acid (HA) C increased in all substrates. In the HAL fractions, the C and H contents, C/N and C/O and aliphatic structures, proteinaceous components and carbohydrates decreased, while the O and N and acidic functional group contents and C/H ratio, aromaticity and polycondensation structures increased. Further, the results suggest that the addition of cow dung to sewage sludge could improve the quality of organic matter humification of the substrates. The structures of HAL fractions in vermicomposts resembled those typical of soil HA, especially the vermicompost of cow dung alone. Scanning electron microscopy showed the microstructure of HAL fraction in final product became close-grained and lumpy. Overall results indicate that vermicomposting was an efficient technology for promoting organic matter (OM) humification in sewage sludge and cow dung alone, as well as in mixtures of both materials, improving their quality and environmental safety as a soil OM resource for utilization as soil amendments.     

Pulse electric current sintering of hydroxyapatite/β-tricalcium phosphate composites

Hydroxyapatite (HA)/β-tricalcium phosphate (β-TCP) composites attract attentions as bone implant materials. As one of the fabrication method of HA/β-TCP is mixing of HA and β-TCP powder in advance of sintering. This method enables to control the ratio of content of β-TCP easier. However, it is difficult to obtain dense composites. In this study, we focused on pulse electric current sintering (PECS) to obtain dense HA/β-TCP composites. The sinterability is evaluated with relative density and grain size measurements. Composition of sintered body was also characterized by X-ray diffraction. In comparison with pressureless sintering, PECS increased relative density of the composites without grain growth. In HA/β-TCP sintered by PECS, the phase transformation from β-TCP to α-TCP was promoted. This is due to higher thermal energy by spark discharge during PECS. On the other hand, sintering additives (MgO) inhibited phase transformation. It was suggested that sinterability of HA/β-TCP composites was improved by PECS.     

Elemental and spectroscopic characterization of humic-acid-like compounds during composting of olive mill by-products

Humic acids (HAs) were isolated at different stages of composting from two piles of solid olive mill residues (SOR) treated for the first 30 days with tap water (pile C1) or olive mill wastewater (pile C2), for a total composting period of 9 months. The HA fractions were characterized by elemental analysis, UV-visible, Fourier transform infrared and fluorescence spectroscopy in order to monitor humification process and the maturity of the composts. As composting proceeded, the elemental composition of the humic acids showed a decrease in C and H content, and in the C/N ratio, and an increase in N and O contents and in the C/H and O/C ratios. These changes could be attributed to a loss of aliphatic groups and to an increase of aromatic character, polycondensation and degree of oxidation of the HAs. Spectroscopic data agree and support these results, suggesting that the chemical and structural features of the HAs of both composts tend to reach those typical of native soil HAs, that is compounds with a high degree of humification and a high molecular weight and complexity. Therefore, both composting processes seem suitable to produce well-humified organic matter, with important benefits for their use in soil amendment. No differences appeared between the two treatments concerning the humic character of the two final composts.     

Sorption behaviors of aromatic anions on loess soil modified with cationic surfactant

Modification of soils with hydrophobic cationic surfactants is an effective approach for enhancing the sorptive capabilities of soil in the vadose zone for the purpose of retaining organic contaminants prior to cleanup. The objective of this study was to examine the sorptive behavior of the cationic surfactant-modified loess soil for aromatic anions in the aqueous phase in an attempt to define the sorptive mechanisms. Some dominant factors governing the sorption, such as ionic strength and divalent heavy metal cation, were investigated. The sorption isotherms of 2,4-dinitrophenol (DNP) and benzoic acid (BA) in the modified soil samples were obtained using the batch equilibration method. Under the laboratory conditions, the modified loess soil utilized in this study was prepared by replacing the cations of loess soil with a cationic surfactant—hexadecyltrimethylammonium (HDTMA) bromide. The acidic aromatic compounds, DNP and BA existing as aromatic anions in the natural mixture of loess soil and aqueous phase, were selected as indicator compounds to measured the sorption behaviors of aromatic anions on the HDTMA-modified loess soil. The results confirmed that the sorptive capabilities of aromatic anions in loess soil were greatly enhanced by modification with HDTMA. The increase of ionic strength and the addition of divalent heavy metal cation Zn²⁺ significantly increased the sorption of aromatic anions on the HDTMA-modified loess soil. In binary solute systems, the sorbed amounts either of DNP or BA on the HDTMA-modified loess soil were reduced if two compounds existed simultaneously in the soil. This results indicated that competitive adsorption between the two aromatic anions occurred in soil matrix.     

Sorption behavior of cesium on various soils under different pH levels

In the present study we investigated the sorption behavior of Cs in four different soils (sandyloam, loam, clayloam and clay) by using batch experiment. Cs sorption characteristics of the studied soils were examined at 4 mgL(-1) Cs concentration, at various pH levels, at room temperature and with 0.01 M CaCl(2) as a background electrolyte. Among different soils the decrease of k(d) (distribution coefficient) of cesium, at all pH levels, followed the sequence sandyloam > loam > clayloam > clay, indicating that the particle size fractions and especially the clay content plays predominant role on sorption of Cs. The effect of pH on cesium sorption displays a similar pattern for all soils, depending on soil type. At acid pH levels less cesium was sorbed, due to a greater competition with other cations for available sorption sites. The maximum sorption of Cs was observed at pH 8, where the negative charge density on the surface of the absorbents was the highest. For all soils was observed significantly lower Cs sorption at pH 10.     

Sorption behavior of tetrabromobisphenol A in two soils with different characteristics

Sorption of tetrabromobisphenol A (TBBPA) in soil influences its fate and transport in the environment. The sorption behaviors of TBBPA in two soils with different characteristics were investigated using batch equilibration experiments in the study, and the impacts of ionic strength and pH on the sorption were also evaluated. The results showed that the fast sorption rather than the slow sorption played a main role in the sorption process. The nonlinear sorption isotherms of TBBPA in the soils were observed and the Freundlich model could describe the sorption behavior of TBBPA well. The calculated K_F were 78.5 and 364.6  (mg/kg)(mg/L)⁻ⁿ for LN soil (loamy clay) and GX soil (silt loam), respectively. Soil organic matter (SOM) played a main role in the sorption of TBBPA, which contributed about 90% to the sorption in the soils. The desorption hysteresis of TBBPA was revealed in the single-cycle sorption and desorption experiments. The sorbed amount of TBBPA decreased with the increase in solution pH and increased with the increase in ionic strength. It was found that the effects of ionic strength on the sorption were mainly caused by the change of solution pH.     

Interaction of 2,4,6-trichlorophenol with high carbon iron filings: Reaction and sorption mechanisms

Reductive dehalogenation of 2,4,6-trichlorophenol (2,4,6-TCP) by two types of high carbon iron filings (HCIF), HCIF-1 and HCIF-2 was studied in batch reactors. While the iron, copper, manganese and carbon content of the two types of HCIF was similar, the specific surface area of HCIF-1 and HCIF-2 were 1.944 and 3.418m(2)g(-1), respectively. During interaction with HCIF-1, 2,4,6-TCP adsorbed on HCIF-1 surface resulting in rapid reduction of aqueous phase 2,4,6-TCP concentration. However, reductive dehalogenation of 2,4,6-TCP was negligible. During interaction between 2,4,6-TCP and HCIF-2, both 2,4,6-TCP adsorption on HCIF-2, and 2,4,6,-TCP dechlorination was observed. 2,4,6-TCP partitioning between solid and aqueous phase could be described by a Freundlich isotherm, while 2,4,6-TCP dechlorination could be described by an appropriate rate expression. A mathematical model was developed for describing the overall interaction of 2,4,6-TCP with HCIF-2, incorporating simultaneous adsorption/desorption and dechlorination reactions of 2,4,6-TCP with the HCIF surface. 2,4-Dichlorophenol (2,4-DCP), 2-chlorophenol (2-CP) and minor amounts of 4-chlorophenol (4-CP) evolved as 2,4,6-TCP dechlorination by-products. The evolved 2,4-DCP partitioned strongly to the HCIF surface. 4-CP and 2-CP accumulated in the aqueous phase. No transformation of 2-CP or 4-CP to phenol was observed.     

稻草生物炭对铕的吸附行为及机理研究

以农业残留物为原料制备的生物炭被广泛应用于去除重金属, 这对于环境保护具有双重意义。本研究以稻草为原料制备了生物炭, 通过系列静态实验和光谱技术研究其对重金属铕(Eu)的吸附行为及机理。研究发现溶液pH显著影响生物炭对Eu(III)的吸附量, 但不改变吸附反应时间; 腐殖酸/富里酸(HA/FA)在pH<7.0的溶液中能促进生物炭对Eu(III)的吸附, 而在pH>7.0的溶液中则抑制Eu(III)的吸附; 吸附过程主要涉及共沉淀或内表面络合机制; 该吸附属于化学吸附, 且吸附速率受内颗粒扩散过程的限制。此外, Freundlich模型对该吸附拟合最好, Langmuir模型显示稻草生物炭对Eu(III)的最大吸附量为40.717 mg/kg, 这可能与生物炭的层状结构和丰富的官能团有关; 热力学分析表明该吸附是自发的吸热过程。这些发现有利于评估稻草生物炭在去除水中重金属方面潜在的应用价值。     

Metal sorption on soils as affected by the dissolved organic matter in sewage sludge and the relative calculation of sewage sludge application

To evaluate the influences of sewage sludge-derived organic matters on metal sorption and on the resultant sludge loading estimates, a batch experiment was conducted to compare the sorption of Ni, Cu and Pb in sewage sludge filtrates (1:20 sewage sludge to water) on eight soils and the adsorption of metals in a reference solution which had the same matrix as the sewage sludge filtrate except dissolved organic material (henceforth referred to as reference solution). Metal sorption could be well fitted by linear isotherm and the dissolved organic matter in sludge significantly depressed the sorption (p<0.01). The main factor controlling sorption of Ni on different soils was dominated by soil cation exchange capacity (CEC) and sorption of Cu and Pb was by soil organic matter (SOM). The parameters obtained from the sorption isotherm equations were then used to estimate sludge loadings into the soils. When the sorption parameters derived from the reference solution were used for calculation, that is the effect of dissolved organic matter was not considered, the calculated safe application rates are approximately 47.8, 51.4, 34.2, 31.3, 21.7, 46.3, 187.1 and 27.6 t-sludge/ha for the Beijing, Jiangxi, Xiamen, Jilin, Guangdong, Wuhan, Gansu and Xinjiang soils, respectively. However, when the sorption parameters derived from the dissolved organo-metallic complexes are used for calculation, the corresponding application rates are reduced to approximately 6.0, 3.4, 1.9, 10.0, 6.3, 3.6, 7.3 and 3.5 t-sludge/ha, respectively. By this study we can get a conclusion that the effect of sewage sludge derived dissolved organic matter on heavy metal sorption and soil properties should be considered in the course of regulating the safe application rates of sewage sludge to soil.     

Effect of soil organic matter chemistry on sorption of trinitrotoluene and 2,4-dinitrotoluene

The sorption of organic contaminants in soil is mainly attributed to the soil organic matter (SOM) content. However, recent studies have highlighted the fact that it is not the total carbon content of the organic matter, but its chemical structure which have a profound effect on the sorption of organic contaminants. In the present study sorption of two nitroaromatic contaminants viz. trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT) was studied in different SOM fractions viz. a commercial humic acid, commercial lignin and humic acid and humin extracted from a compost. ¹³C-DP/MAS NMR studies indicated that the structural composition of the organic carbon in different SOM fractions was different. The order of sorption of the nitroaromatics in the different sorbents was: humic acid-commercial > humic acid-compost > humin ～ lignin. Among the aliphatic and aromatic carbon fractions (representing bulk of SOM matrix), adsorption parameter K_f(1/n) for nitroaromatics sorption correlated well with the aliphatic carbon (r = 0.791 for TNT and 0.829 for 2,4-DNT) than the aromatic carbon (r = 0.634 for TNT and r = 0.616 for 2,4-DNT). However, among carbon containing functional groups, carbonyl carbon showed strong positive correlation with sorption of TNT (r = 0.991) and 2,4-DNT (r = 0.967) while O-alkyl carbon showed negative correlation (r = 0.832 for TNT and r = 0.828 for 2,4-DNT). The study indicates that aliphatic domains in the SOM significantly affect the non-specific sorption of both the nitroaromatic contaminants.     

Time-dependent sorption of norflurazon in four different soils: use of beta-cyclodextrin solutions for remediation of pesticide-contaminated soils

High pesticide concentrations in soil from spills or discharges can result in point-source contamination of ground and surface waters. Cost-effective technologies are needed for on-site treatment that meet clean-up goals and restore soil function. Remediation is particularly challenging when a mixture of pesticides is present. beta-Cyclodextrins (BCD) solutions are employed to enhance the aqueous solubility of a hydrophobic organic compound. The interaction of norflurazon (NFL) with BCD yielded the formation of inclusion complexes at a 1:1 stoichiometric ratio in solution. The change of the sorption parameter K(d) as affected by the time, and desorption studies of NFL previously adsorbed on four different soils with different characteristics have been performed in the presence of 0.01 M BCD or 0.01 M Ca(NO(3))(2) acting as extractant solutions. NFL sorption increased with the residence time in soil, making it more resistant to be desorbed. Likewise, leaching experiments were performed in packed soil columns eluting initially with distilled water, with the aim to simulate the herbicide drainflow losses because of rainfall, approaching to a more realistic environment, and later with 0.01 M BCD solutions to extract the residual NFL bound. The results showed that removal efficiencies of the different flushing systems were significantly influenced by their affinity and selectivity for the contaminants in the soil matrix as well as BCD adsorption on soils, since this could act like a bridge between pesticide molecule and soil particles increasing the stay of NFL in soil. These results are further information to be in condition to predict the potential effect of the BCD solutions on soil chemical decontamination in the field situation assessing the likelihood for bioremediation of a pesticide contaminated-soil, since the increasing in hydrosolubility of the contaminants means the first step before microorganism uptaken.     

Impact of exotic and inherent dissolved organic matter on sorption of phenanthrene by soils

The impacts of exotic and inherent dissolved organic matter (DOM) on phenanthrene sorption by six zonal soils of China, chosen so as to have different soil organic carbon (SOC) contents, were investigated using a batch technique. The exotic DOM was extracted from straw waste. In all cases, the sorption of phenanthrene by soils could be well described by the linear equation. The presence of inherent DOM in soils was found to impede phenanthrene sorption, since the apparent distribution coefficients (K(d)(*)) for phenanthrene sorption by deionized water-eluted soils were 3.13-21.5% larger than the distribution coefficients (K(d)) by control soils. Moreover, the enhanced sorption of phenanthrene by eluted versus control soils was in positive correlation with SOC contents. On the other hand, it was observed that the influence of exotic DOM on phenanthrene sorption was related to DOM concentrations. The K(d)(*) values for sorption of phenanthrene in the presence of exotic DOM increased first and decreased thereafter with increasing the added DOM concentrations (0-106mgDOC/L). The K(d)(*) values at a low exotic DOM concentration (< or =28mgDOC/L) were 14.7-48.4% larger than their control K(d) values. In contrast, higher concentrations (> or =52mgDOC/L) of added exotic DOM clearly impeded the distribution of phenanthrene between soil and water. The effects of exotic and inherent DOM on phenanthrene sorption by soils may primarily be described as 'cumulative sorption', association of phenanthene with DOM in solution, and modified surface nature of soil solids due to DOM binding.     

Pu and Am Distribution in the System Soil-Water-Carboxylic Resin

Dynamics of Pu and Am distribution between components of the system soil-water-carboxylic resin is studied for soils with various absorbing (clay-humus) complexes. The fractional composition of organic components of the aqueous phase of the system and TUE content in the fractions were examined to elucidate the Pu and Am speciation in the solution. The Pu and Am concentrations in the aqueous phase strongly depend on the content and composition of the soil humus matter. Transuranic elements are associated essentially with the humic acid fractions, this trend being more pronounced for Pu. In the system with increased humus content, TUE occur in the solution as complexes with humus substances, and in the system with lower humus content, as hydrolyzed species. The features of sorption processes occurring on the clayhumus complex of the soil were judged from the sorption isotherms of the radionuclides on a resin. Sorption on the resin is controlled by the Pu and Am speciation in the solution.     

Specific proliferation rates of human osteoblasts on calcium phosphate surfaces with variable concentrations of α-TCP

Ideally, ceramics used in the repair of bone defects need to be resorbed and replaced by newly formed bone in vivo. Tricalcium phosphate (TCP) has been widely used in association with hydroxyapatite (HA) due to its higher resorption kinetics when compared with HA alone. The aim of our study was to quantitatively investigate the effect of α-tricalcium phosphate (α-TCP) on human osteoblasts' adhesion and proliferation. Ceramic samples with variable concentrations of α-TCP and HA were produced by the calcination of calcium-deficient and stoichiometric HA. Human osteoblasts were cultured on the materials in three distinct experiments with different concentrations of cells. Numerical evaluation of cellular growth along time in culture was performed for each condition. The quantity of cells seeded onto the ceramics seems to influence the osteoblast behavior once proliferation was lower when more cells were seeded onto the samples. However, a smaller content of α-TCP in relation to that of HA did not significantly modify the specific proliferation rates of the osteoblasts. Only after a long time in culture, the increasing of the α-TCP content seems to change the cells' behavior.     

Preparation of activated carbon from coconut husk: optimization study on removal of 2,4,6-trichlorophenol using response surface methodology

Activated carbon was prepared from coconut husk using physicochemical activation method which consisted of potassium hydroxide (KOH) treatment and carbon dioxide (CO(2)) gasification. The effects of three preparation variables (CO(2) activation temperature, CO(2) activation time and KOH:char impregnation ratio) on the 2,4,6-trichlorophenol (2,4,6-TCP) uptake and activated carbon yield were investigated. Based on the central composite design, two quadratic models were developed to correlate the preparation variables to the two responses. From the analysis of variance (ANOVA), the most influential factor on each experimental design response was identified. The activated carbon preparation conditions were optimized by maximizing both the 2,4,6-TCP uptake and activated carbon yield. The predicted 2,4,6-TCP uptake and carbon yield from the models agreed satisfactorily with the experimental values. The optimum conditions for preparing activated carbon from coconut husk for adsorption of 2,4,6-TCP were found as follow: CO(2) activation temperature of 750 degrees C, CO(2) activation time of 2.29 h and KOH:char impregnation ratio of 2.91, which resulted in 191.73 mg/g of 2,4,6-TCP uptake and 20.16 % of activated carbon yield.     

Assessment of electrokinetic removal of heavy metals from soils by sequential extraction analysis

Electrokinetic remediation of metal-contaminated soils is strongly affected by soil-type and chemical species of contaminants. This paper investigates the speciation and extent of migration of heavy metals in soils during electrokinetic remediation. Laboratory electrokinetic experiments were conducted using two diverse soils, kaolin and glacial till, contaminated with chromium as either Cr(III) or Cr(VI). Initial total chromium concentrations were maintained at 1000mg/kg. In addition, Ni(II) and Cd(II) were used in concentrations of 500 and 250mg/kg, respectively. The contaminated soils were subjected to a voltage gradient of 1 VDC/cm for over 200h. The extent of migration of contaminants after the electric potential application was determined. Sequential extractions were performed on the contaminated soils before and after electrokinetic treatment to provide an understanding of the distribution of the contaminants in the soils. The initial speciation of contaminants was found to depend on the soil composition as well as the type and amounts of different contaminants present. When the initial form of chromium was Cr(III), exchangeable and soluble fractions of Cr, Ni, and Cd ranged from 10 to 65% in kaolin; however, these fractions ranged from 0 to 4% in glacial till. When the initial form of chromium was Cr(VI), the exchangeable and soluble fractions of Cr, Ni and Cd ranged from 66 to 80% in kaolin. In glacial till, however, the exchangeable and soluble fraction for Cr was 38% and Ni and Cd fractions were 2 and 10%, respectively. The remainder of the contaminants existed as the complex and precipitate fractions. During electrokinetic remediation, Cr(VI) migrated towards the anode, whereas Cr(III), Ni(II) and Cd(II) migrated towards the cathode. The speciation of contaminants after electrokinetic treatment showed that significant change in exchangeable and soluble fractions occurred. In kaolin, exchangeable and soluble Cr(III), Ni(II), and Cd(II) decreased near the anode and increased near the cathode, whereas exchangeable and soluble Cr(VI) decreased near the cathode and increased near the anode. In glacial till, exchangeable and soluble Cr(III), Ni(II), and Cd(II) were low even before electrokinetic treatment and no significant changes were observed after the electrokinetic treatment. However, significant exchangeable and soluble Cr(VI) that was present in glacial till prior to electrokinetic treatment decreased to non-detectable levels near the cathode and increased significantly near the anode. In both kaolin and glacial till, low migration rates occurred as a result of contaminants existing as immobile complexes and precipitates. The overall contaminant removal efficiency was very low (less than 20%) in all tests.     

Behavior of ionic and colloid forms of microelements in colloidal chemical extraction from humic acid solutions

Speciation and extractability of humic acids (HAs) and humate complexes of microelements are studied using the colloidal chemical extraction method in combination with ICP MS with an example of natural mineral water with high HA concentration (800–1200 mg l^?1) collected from the Salekhard region. Joint extraction behavior of ionic and colloid forms of anionic and cationic species of a large number of microelements, including U(VI) and Th(IV), and HAs is examined at their natural abundance in mineral water, as influenced by pH and HA concentration. Humic acids proved to behave in natural water as a pool of ion-colloidal species, whose protonation results in precipitation at pH 2.0–3.5. In this case, some chemical elements are sorbed on the resulting solid and may be separated along with HAs by colloidal chemical extraction into isobutanol. In natural humate solutions, a considerable fraction (10–99 mol %) of chemical elements is associated with HAs in the form of colloid species extractable with isobutanol.     

Impact of low molecular weight organic acids and dissolved organic matter on sorption and mobility of isoproturon in two soils

Isoproturon is a selective herbicide belonging to the phenylurea family and widely used for pre- and post-emergence control of annual weeds. Soil amendments (e.g. organic compounds or dissolved organic matter) may affect environmental behavior and bioavailability of pesticides. However, whether the physiochemical process of isoproturon in soils is affected by organic amendments and how it is affected in different soil types are unknown. To evaluate the impact of low molecular weight organic acids (LMWOA) and dissolved organic matter (DOM) on sorption/desorption and mobility of isoproturon in soils, comprehensive analyses were performed using two distinct soil types (Eutric gleysols and Hap udic cambisols). Our analysis revealed that adsorption of isoproturon in Eutric gleysols was depressed, and desorption and mobility of isoproturon were promoted in the presence of DOM and LMWOA. However, the opposite result was observed with Hap udic cambisols, suggesting that the soil type affected predominantly the physiochemical process. We also characterized differential components of the soils using three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy and Fourier transform infrared (FT-IR) spectroscopy and show that the two soils displayed different intensity of absorption bands for several functional groups.