Influence of frozen storage on herbicide degradation capacity in surface and subsurface sandy soils

The degradation of MCPA and metribuzin was investigated in laboratory batch experiments using fresh and frozen-stored soil samples from the unsaturated zone of a sandy soil. Mineralization potentials measured in fresh and frozen-stored soils were similar, and mineralization kinetics in surface and subsurface soils could be fitted using the same kinetic models. MCPA mineralization data from all three horizons were best described with the exponential growth form of the three-half-order model. During the mineralization of MCPA, growth in MCPA-degrading microbial populations was confirmed by increases in the abundance of tfdA genes following MCPA exposure. In contrast to MCPA, metribuzin mineralization followed zero-order kinetics, and very little metribuzin was mineralized (<1%) in all three of the investigated soil horizons. In addition, metribuzin dissipation and metabolite formation were also measured in surface and subsurface soils using LC-MS/MS. Differences in metribuzin dissipation were observed in the A-horizon at the beginning of the experiment and resulted in substantially different 50% disappearance time, DT50, values for frozen-stored (36 days) and fresh (<15 days) soil samples. However, the % of metribuzin remaining in fresh and frozen-stored surface soils was comparable from day 37 and thereafter.     

In situ identification of microorganisms in biofilm communities

Diverse microorganisms form complex microbial communities and usually exist in biofilm communities in both natural environments and engineered systems such as a wastewater treatment process. However, the conventional approach to investigate microbial ecology has not contributed to the understanding and clarification of the structure and function of biofilm communities. Some effective methods have been developed to investigate phylogenetic affiliations, metabolic activities and genetic activities in biofilm communities at the single-cell level. These techniques have been contributing to a better understanding of the spatial organization of biofilm communities and activities in engineered systems. However, further effort is needed to set out the general rules governing community development in biofilm communities and to advance the process performance of engineered systems. This review describes advances and limitations in methodology, particularly focusing on fluorescence in situ hybridization (FISH) and related techniques and the application of these methods to nitrifying biofilms in wastewater treatment processes.     

Patchy biofilm coverage can explain the potential advantage of BGAC reactors

An adsorbing biofilm carrier, like granular activated carbon (GAC), can be the source of an extra flux of pollutant to the biofilm in addition to the bulk liquid. This double flux can improve the performance of a biological GAC (BGAC) reactor as compared to a nonabsorbing carrier reactor but only under conditions of pollutant partial penetration in the biofilm. Pollutant partial penetration in a biofilm often occurs in treatment processes where very low effluent concentrations are required. However, under these conditions, adsorption in BGAC reactors is questionable and requires the existence of biofilm free areas on the GAC carrier. The purpose of this investigation is to prove that under normal BGAC fluidized bed reactor operational conditions patchy biofilm coverage with exposed areas of GAC develops. Adsorption and desorption through these exposed areas can explain the widely debated advantage of BGAC reactors regarding higher biofilm activity. The patchy-like nature of the biofilm coverage on the GAC particles was verified using experimental and modeling tools. Comparison between a nonadsorbing granular carbon carrier and a GAC carrier with an atrazine degrading biofilm (Pseudomonas ADP) under conditions of atrazine partial penetration in the biofilm showed higher biodegradation and lower effluent atrazine concentrations in the BGAC reactor.     

阴离子交换树脂的粒径和吸附时间对植酸吸附容量的影响

717型阴离子交换树脂的粒径大小和吸附时间长短对植酸在该树脂上的吸附容量有很大影响。通过离子交换的吸附实验,测定植酸在717型阴离子交换树脂上的吸附数据,利用统计分析理论对实验结果进行分析,得出了植酸吸附容量同阴离子交换树脂的粒径与吸附时间之间的统计分析模型和三维曲面图,并确定直径≤20目的阴离子交换树脂进行吸附实验的实验效果较好。      

Influence of surface oxidation of multiwalled carbon nanotubes on the adsorption affinity and capacity of polar and nonpolar organic compounds in aqueous phase

Adsorption of organic contaminants on carbon nanotubes (CNTs) is a critical behavior in the environmental application of CNTs as sorbents and in the environmental risk assessment of both organic contaminants and CNTs. Oxidation of CNTs may introduce oxygen-containing groups on CNTs' surface and then alter the adsorption of organic contaminants. In this study, adsorption of polar and nonpolar organic compounds on four multiwalled carbon nanotubes (MWCNTs) containing varied amounts of surface oxygen-containing groups were investigated to examine the influence of CNTs' surface oxidation on adsorption. We observed that surface oxidation of MWCNTs reduced the surface area-normalized adsorption capacity of organic compounds significantly because of the competition of water molecules but did not alter the adsorption affinity. The interactions (i.e., hydrophobic effect, π-π bonds, and hydrogen bonds) and the interaction strength for adsorption of organic molecules on MWCNTs could not be altered by the surface oxidation of MWCNTs and thus were responsible for the unaltered adsorption affinity. In addition, the decrease of surface area-normalized adsorption capacity of the organic compound with more polarity and higher adsorption affinity by surface oxidation was less because of the heterogeneous nature of hydrophilic sites of MWCNTs' surface.     

混纺活性炭纤维针刺毡的生产与预氧化

利用自制的预氧化针刺毡和自制的设备,采用一步法蒸汽碳化活化工艺来生产活性炭纤维针刺毡。影响活性炭纤维针刺毡的产出率和对碘吸附能力的因素主要有4个:活化温度、活化时间、蒸汽流速、升温速率,用正交试验得出了一步法蒸汽碳化活化生产的最佳工艺参数,最后用单因素实验进一步揭示这4因素对实验结果的影响。     

Influence of organic complexation on the adsorption kinetics of nickel in river waters

The kinetics of Ni adsorption in rivers of widely different chemical characteristics have been studied by monitoring the uptake of 63Ni by suspended sediment particles. The rate and extent of adsorption was critically dependent on the presence and concentration of dissolved organic matter (DOM), defined analytically as the concentration of dissolved organic carbon (DOC). Thus, adsorption was greatest in experiments in which the DOM was decomposed by UV-oxidation and least in experiments in which Ni was preequilibrated with filtered river water before addition of particles. The extent of adsorption arising from the latter approach displayed a clear, inverse dependency on the concentration of DOC in the sample. These observations were interpreted and modeled in terms of the competing effects of DOM and particle sorption sites for dissolved Ni. Adsorption onto suspended particles in the absence of dissolved complexing ligands was adequately described by a reversible, two-stage reaction and a single set of adsorption rate constants. Forward and reverse rate constants defining Ni complexation with DOM of about 8 x 10(4) h(-1) M(-1) and 10 h(-1), respectively, were derived from data-fitting. The experimental and model results indicate that the toxicity, availability, and transport of Ni in freshwater environments are largely dictated by the concentration of DOM and the speciation of Ni entering the watercourse.     

Gas-phase formaldehyde adsorption isotherm studies on activated carbon: correlations of adsorption capacity to surface functional group density

Formaldehyde (HCHO) adsorption isotherms were developed for the first time on three activated carbons representing one activated carbon fiber (ACF) cloth, one all-purpose granular activated carbon (GAC), and one GAC commercially promoted for gas-phase HCHO removal. The three activated carbons were evaluated for HCHO removal in the low-ppm(v) range and for water vapor adsorption from relative pressures of 0.1-0.9 at 26 °C where, according to the IUPAC isotherm classification system, the adsorption isotherms observed exhibited Type V behavior. A Type V adsorption isotherm model recently proposed by Qi and LeVan (Q-L) was selected to model the observed adsorption behavior because it reduces to a finite, nonzero limit at low partial pressures and it describes the entire range of adsorption considered in this study. The Q-L model was applied to a polar organic adsorbate to fit HCHO adsorption isotherms for the three activated carbons. The physical and chemical characteristics of the activated carbon surfaces were characterized using nitrogen adsorption isotherms, X-ray photoelectron spectroscopy (XPS), and Boehm titrations. At low concentrations, HCHO adsorption capacity was most strongly related to the density of basic surface functional groups (SFGs), while water vapor adsorption was most strongly influenced by the density of acidic SFGs.     

In situ lifetimes and kinetics of a reductive whey barrier and an oxidative ORC barrier in the subsurface

Permeable reactive barriers (PRB) are being used to engineer favorable field conditions for in-situ remediation efforts. Two redox adjustment barriers were installed to facilitate a 10-month research effort on the fate and transport of MTBE (methyl tert-butyl ether) at a site called the Michigan Integrated Remediation Technology Laboratory (MIRTL). Thirty kilograms of whey were injected as a slurry into an unconfined aquifer to establish an upgradient reductive zone to reduce O2 concentration in the vicinity of a contaminant injection source. To minimize the impact of contaminant release, 363 kg of oxygen release compound (ORC) were placed in the aquifer as a downgradient oxidative barrier. Dissolved oxygen and other chemical species were monitored in the field to evaluate the effectiveness of this technology. A transient one-dimensional advective-dispersive-reaction (ADR) model was proposed to simulate the dissolved oxygen transport. The equations were solved with commonly encountered PRB initial and constant/variable boundary conditions. No similar previous solution was found in the literature. The in-situ lifetimes, based on variable source loading, were estimated to be 1,661 and 514 days for the whey barrier and ORC barrier, respectively. Estimates based on either maximum O2 consumption/production or measured O2 curves were found to under- or overestimate the lifetime of the barriers. The pseudo-first-order rate constant of whey depletion was estimated to be 0.303/d with a dissolution rate of 0.04/d. The oxygen release rate constant in the ORC barrier was estimated to be 0.03/d. This paper provides a means to design and predict the performance of reactive redox barriers, especially when only limited field data are available.     

活性炭纤维形态对吸附性能的影响

比表面积和孔结构是影响活性炭纤维吸附性能的重要因素。选用相同的活化工艺,制备相似孔结构和比表面积的活性炭毡和活性炭布,讨论在比表面积相近的情况下,活性炭纤维的形态和厚度对吸附性能的影响。结果表明:在一定条件下,活性炭毡的吸附性能略优于活性炭布,活性炭纤维的吸附能力并不随着活性炭织物厚度的增加而线性增强。     

Influence of the polyethylene packaging on the adsorption of odour-active compounds from UHT-milk

Application of an Aroma Extract Dilution Analysis (AEDA) on distillates prepared from two UHT-milks either packed in polyethylene (PE-M) or glass (G-M), respectively, revealed δ-decalactone and γ-dodecalactone as the most odour-active constituents among the 37 odour-active constituents in the PE-M. δ-Decalactone was also the most odour-active among the 32 odorants detected in G-M, followed by δ-octalactone, γ-dodecalactone, (Z)-6-γ-dodecenolactone and vanillin. To detect a possible adsorption of odorants at the packaging, the AEDA was also applied on solvent extracts obtained from both, the glass and the polyethylene bottles, in which the two milks were supplied. The results confirmed the high tendency of polyethylene to adsorb odorants, while the affinity of the aroma compounds to glass were weak. A comparative quantification of selected key odorants in the polyethylene packaging as well as in the milk, allowed the calculation of adsorption ratios. The results demonstrated a strong influence of the chemical structure on the extent of adsorption. For instance, aldehydes, such as (E)-2-nonenal and (E,Z)-2,6-nonadienal, had a much higher affinity to polyethylene than lactones and acids. The results indicated that the overall aroma of UHT-milk packed in polyethylene can be changed during storage by adsorption as well as by permeation processes of milk aroma compounds to and through polyethylene packaging.     

Mechanism of water adsorption capacity change of bamboo by heating

The water adsorption capacity of moso bamboo (Phyllostachys pubescens) heated at 200 °C in air for various times was examined. The samples were subsequently placed in various humidities at 20 °C to obtain relevant isotherms. They were analyzed using the Hailwood and Horrobin theory, derived for hydrophilic macromolecules, and the Dubinin and Radushkevich theory, previously used to describe the behavior of microporous carbons. The results show that the water adsorption capacities of the samples changed after heating for 2 to 5 hrs, and imply that over this time the number of hydroxyl groups decreased markedly while the number of micropores formed increased.     

淀粉纳米颗粒的高效制备及吸附性能

以木薯淀粉为原料,在微波和超声波双外场的作用下采用沉淀法制备淀粉纳米颗粒(starch nanoparticles,SNPs)。通过动态光散射仪(dynamic light scattering,DLS)、场发射扫描电镜(scanning electronic microscope,SEM)、原子力显微镜(atomic force microscope,AFM)、比表面积分析仪(Brunner-Emmet-Teller,BET)对SNPs进行表征,考察了SNPs对番红花红T的吸附机理,进一步考察了时间、吸附剂的投加量、粒径对吸附的影响。结果表明:SNPs具有较好的球形形貌,是V型淀粉晶体结构,Zeta电位值为-23. 7 m V,比表面积大大增加。在番红花红T的质量浓度为200 mg/L,吸附时间为60 min,温度为298. 15 K的条件下,投加20 mg平均粒径为40 nm的SNPs,吸附量可达115 mg/g。SNPs对番红花红T的吸附过程符合准二级动力学模型和Langmuir等温吸附模型。     

Influence of the adherent population level on biofilm population,structure and resistance to chlorination

The aim of this work was to study the influence of adherent population level on biofilm development, either on biofilm population, or on its structure. Our results, obtained from 13 strains isolated from dairy industries environments, demonstrated that, on the whole, Gram-negative bacteria were, although not significantly, globally more adherent to glass than Gram-positive ones (total mean of 6·1 and 5·7 log cfu cm⁻²respectively for an inoculum of 8 log cfu ml⁻¹). Gram-negative bacteria also exhibited a significantly higher biofilm population after 2 days of culture than Gram-positives (7·0 and 6·3 log cfu cm⁻²respectively) and a significant correlation between adhesion ability and biofilm population was seen. Elsewhere, we demonstrated that the level of adherent population did not influence biofilm biomass after 2 days of culture, although it strikingly influenced the biofilm structure. Biofilm resistance to chlorine was significantly increased with age of biofilm (2 log order after 1 day of culture and less than 1 log order after 3 days), but not by its structure.     

膳食纤维吸附脂肪、胆固醇和胆酸盐的研究

采用离体实验模拟人体胃和肠道的pH环境,探讨了大豆纤维、小麦纤维、水果纤维以及由3者和低聚果糖组成的复合膳食纤维产品“清多冲剂”的持水力、对脂肪、胆固醇、胆酸盐的吸附能力,为功能性复合膳食纤维产品的研发提供依据。结果表明,对花生油的吸附能力表现为小麦纤维2.68g/g>清多冲剂2.35g/g>大豆纤维1.76g/g～水果纤维1.66g/g;对猪油的吸附能力表现为小麦纤维5.64g/g>清多冲剂5.37g/g>大豆纤维5.14g/g～水果纤维4.57g/g。对胆固醇和胆酸的吸附,水果纤维能力最强,分别为11.34g/g和73.70mg/g,复合膳食纤维产品“清多冲剂”次之,其吸附量为9.23g/g和45.37mg/mL;两者的吸附能力都大大高于小麦纤维和大豆纤维的吸附能力。另外,在胃pH条件下,几种膳食纤维对胆固醇的吸附能力显著低于在肠道pH条件下。实验结果说明,复合膳食纤维“清多冲剂”能综合3种单一种类膳食纤维的优点。     

Influence of surface oxides on the adsorption of naphthalene onto multiwalled carbon nanotubes

As greater quantities of carbon nanotubes (CNTs) enter the environment, they will have an increasingly important effect on the availability and transport of aqueous contaminants. As a consequence of purification, deliberate surface functionalization, and/or exposure to oxidizing agents after release to the environment, CNTs often contain surface oxides (i.e., oxygen containing functional groups). To probe the influence that surface oxides exert on CNT sorption properties, multiwalled CNTs (MWCNTs) with varying oxygen concentrations were studied with respect to their sorption properties toward naphthalene. For pristine (as-received) MWCNTs, the sorption capacity was intermediate between that of a natural char and a granular activated carbon. Sorption data also reveal that a linear relationship exists between the oxygen content of MWCNTs and their maximum adsorption capacity for naphthalene, with 10% surface oxygen concentration resulting in a roughly 70% decrease in maximum adsorption capacity. The relative distribution of sorption energies, as characterized by Freundlich isotherm exponents was, however, unaffected by oxidation. Thus, the data are consistent with the idea that incorporated surface oxides create polar regions that reduce the surface area available for naphthalene sorption. These results highlight the important role of surface chemistry in controlling the environmental properties of CNTs.     

U(VI) adsorption to heterogeneous subsurface media: application of a surface complexation model

The pH-dependent adsorption of U(VI) onto three heterogeneous, subsurface media from the Department of Energy (DOE) Oak Ridge Reservation, Savannah River Site, and Hanford Reservation was investigated. The three materials contained significant quantities of iron and manganese oxides with nearly identical extractable iron oxide contents (25.3-25.8 g/kg). A model independently developed for the adsorption of U(VI) to synthetic ferrihydrite (Waite, T. D.; Davis, J. A.; Payne, T. E.; Waychunas, G. A.; Xu, N. Geochim. Cosmochim. Acta 1994, 58, 5465-5478) was able to predict the major features of the pH-dependent U(VI) adsorption to the materials under the assumption that all the dithionite-citrate-bicarbonate extractable iron oxide was present as ferrihydrite. Further experiments with the Oak Ridge soil as a function of carbonate and U(VI) concentration indicated that the model could predict pH-dependent U(VI) adsorption to within a root mean square error of 0.163-0.408, even under conditions outside of those for which the model was developed. These results indicate that this model could be used as a first approximation in predicting U(VI) adsorption and transport in the subsurface. U(VI) adsorption also decreased at pH >10, even in the absence of carbonate, which is of potential importance to U(VI) mobility in extreme environments present in the subsurface at some DOE facilities. The pH-dependent adsorption of U(VI) was fundamentally different in systems with a constant CO2 partial pressure as compared to a constant total carbonate concentration. Experiments at constant CO2 partial pressure may not be representative of the conditions present in the subsurface, and a constant carbonate concentration does not always result in decreased U(VI) adsorption at higher pH values.     

纤维素结合域的引入对角质酶在纤维素类纤维上吸附性能的影响

为了研究纤维素结合域（Cellulose-binding Domain,CBD）的引入对角质酶在纤维素类纤维上吸附能力的影响,本文选用漂白棉织物、粘胶纤维、醋酯纤维以及纯棉针织坯布这四种材质,对角质酶与CBD-角质酶进行吸附对比试验。研究表明：CBD结构的引入,可提高角质酶在纤维素纤维上的吸附量。但是当纤维素葡萄糖残基上羟基被部分酯化后,CBD结构的引入对吸附量造成的影响开始减弱,而当纤维素纤维表面被疏水性杂质覆盖时,CBD-角质酶对纤维素纤维的吸附能力反而降低。     

Influence of temperature variation on the metabolism of pig muscle in situ and after excision

The experiment involved six halothane-positive (HP) and six halothane-negative (HN) pigs of about 100 kg liveweight. Under general anaesthesia the tibialis cranialis was exposed. The temperature of the muscle was maintained at either 35 or 40°C (in situ). The muscle was stimulated via the peroneal nerve at 0·1 Hz for 10 min then 1 Hz for 10 further min. Twitch contractions were recorded throughout the stimulation, after which the muscle was excised and split into two parts which were kept in paraffin oil at either 35 or 40°C (post-excision temperature) for 2 h. Samples were taken just before and after the 20 min stimulation period, and at 1 and 2 h after muscle excision for determination of pH and concentrations of PC, ATP, IMP, glycogen, G-6-P and lactate. As soon as one muscle was removed, the operation was repeated on the other leg. Both temperatures (35 and 40°C) were applied to each animal in a balanced design. However data were obtained from only 11 pigs at 40°C as one HP pig died accidentally at the beginning of the 40°C experiment. Halothane sensitivity influenced the pH value and the levels of PC, G-6-P and lactate of the muscle in situ (P < 0·01 in all cases). Temperature affected contrction time (P < 0·01). Both halothane sensitivity and Post-excision temperature affected the pH values and the levels of PC, ATP, IMP, G-6-P and lactate (P < 0·01 in all cases) in the excised muscle. By contrast, the in situ temperature treatments did not affect any of the muscle traits measured after excision. It was concluded that the effects of the various treatments on the rate of metabolism in the excised muscle were wholly explainable in terms of temperature from the time of excision, and that the in situ temperature treatments may not be responsible for the differences after excision.     

Influence of copper loading and surface coverage on the reactivity of granular iron toward 1,1,1-trichloroethane

Although iron-based bimetallic reductants offer promise in treating organohalides, the influence of additive mass loading and two-dimensional surface coverage on reductant reactivity has not been fully elucidated. In this study we examine 1,1,1-trichloroethane reduction by Cu/Fe bimetals as a function of Cu loading and surface coverage. Information from a suite of complementary techniques (X-ray photoelectron spectroscopy, Auger electron spectroscopy, and cross-sectional energy-dispersive X-ray spectroscopy) indicates that displacement plating produces a heterogeneous metallic copper overlayer on iron. The dependence of pseudo-first-order rate constants (k(obs) values) for 1,1,1-trichloroethane reduction on Cu loading exhibits two distinct regimes. At Cu loadings less than 1 monolayer equivalent (approximately 10 micromol Cu/g Fe), a pronounced increase in k(obs) is associated with a corresponding increase in the two-dimensional surface coverage of Cu. A weaker dependence of k(obs) on Cu mass is exhibited at loadings in excess of 1 monolayer equivalent, which we ascribe to an increase in the volume of the metallic overlayer. The observed relationship between k(oba) and loading suggests that 1,1,1-trichloroethane reduction occurs on the Cu surface rather than at the interface between the Cu overlayer and the iron substrate.