Effects of dissolved carbonates and carboxylates on the sorption of thiuram disulfide pesticides on humic acids and model surfaces

The sorption of a hydrophobic pesticide, thiram, on humic acid (HA) occurs via a specific pH-dependent binding of thiram at the deprotonated carboxylates of humic acid, forming a species thiram-[HACOO-] with K = 0.69. Similarly, thiram was sorbed by two model polycarboxylate-{SiO2COOH} materials via the formation of a surface species thiram-{SiO2COO-} with K = 0.45 between thiram and the eprotonated carboxylates grafted on SiO2 particles. In all cases, allowance of presence of bicarbonate at natural concentration caused severe inhibition of thiram's sorption. Oxalate and formate mimic the inhibitive effect of bicarbonate. Theoretical fit of the data showed that the inhibitive effect of HCO3- is due to the formation of the anionic species [thiram-HCO3](-1) (with K = 0.90) which is water soluble and competes with the bound species thiram-{HACOO-}. The same phenomena were observed for the sorption of disulfiram. The specific interaction phenomena reported here bear relevance to the sorption properties of thiram and disulfiram on real soils and, therefore, may determine their environmental fate.     

Effects of dissolved carbonate on arsenic adsorption and mobility

The effects of high aqueous carbonate concentrations on arsenic mobility and transport in the subsurface were studied in synthetic iron oxide-coated sand column experiments. Elevated aqueous carbonate concentrations in groundwater have been studied and linked, by some authors, to increased aqueous As concentrations in natural waters. This study found that increasing carbonate concentrations had relatively little effect on As(V) adsorption to the iron oxide-coated sand surface at pH 7. The adsorption of As(V) decreased marginally when the CO2(g) partial pressure increased from 10(-3.5) to 10(-1.8) atm, despite a 50-fold increase in total dissolved carbonate (0.072 to 3.58 mM). Increasing the CO2(g) partial pressure to 10(-10) atm resulted in only a slight decrease in As(V) adsorption and increase in mobility, despite a >300-fold increase in total dissolved carbonate (to 22.7 mM). When compared to phosphate, a known competitive anion, carbonate mobilized less adsorbed As(V) than was mobilized by phosphate, even when present in much higher concentrations than phosphate. This was also true for an experiment with lower pore water velocity and an experiment where As(II) was introduced instead of As(V). Our experiments conclude that while carbonate anions do compete with As for adsorption to iron oxide-coated sand, the competitive effect is relatively small with regard to the total concentration of adsorbed As and the potential competitive effects of phosphate.     

Relationship between the adsorption capacity of pesticides by wood residues and the properties of woods and pesticides

With the aim to explore the potential use of wood residues in technologies aimed at preventing the pollution of soil and water, we studied the adsorption of four non-ionic pesticides (linuron, alachlor, metalaxyl, and chlorpyrifos) and two ionic pesticides (dicamba and paraquat) with a Kow range of -4.5 to 4.7 by nine types of wood with lignin content in the 18.2-26.9% range. The Freundlich Kf values were considered as indicators of the adsorption capacity. A statistical study was carried out using simple and multiple correlations to establish the degree to which the different parameters of the woods and of the pesticides were involved in adsorption. In the case of the non-ionic pesticides, positive and negative significant correlations were observed between Kf and the lignin (r = 0.73-0.83, p < 0.05-0.01), and soluble C contents of the woods (r = 0.66-0.84), p < 0.1-0.01). For dicamba, a correlation between Kf and pH (r = -0.66, p < 0.1) of the woods was found, while for paraquat, this was seen between Kf and the cation exchange capacity (r = 0.71, p < 0.1) of the woods. No significant correlation was observed between Kf and the total C content of the woods. A highly significant correlation between Kf and Kow values (r > or = 0.93, p < 0.01) was found in the adsorption of the pesticides by the woods (with the exception of paraquat) showing that this parameter is very important in this adsorption process. The determination coefficient of the multiple correlation between Kf and the parameters Kow, soluble C, and lignin contents accounts for nearly 100% of the variability in adsorption for non-ionic pesticides. Based on the results of our study and of those of the literature related to the adsorption of aromatic hydrocarbons, we used the Kow values to define a predictive model of adsorption of hydrophobic organic compounds in general by the woods.     

Effects of dissolved carbonate on arsenate adsorption and surface speciation at the hematite--water interface

Effects of dissolved carbonate on arsenate [As(V)] reactivity and surface speciation at the hematite-water interface were studied as a function of pH and two different partial pressures of carbon dioxide gas [P(CO2) = 10(-3.5) atm and approximately 0; CO2-free argon (Ar)] using adsorption kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure spectroscopic (EXAFS) analyses, and surface complexation modeling. Different adsorbed carbonate concentrations, due to the two different atmospheric systems, resulted in an enhanced and/or suppressed extent of As(V) adsorption. As(V) adsorption kinetics [4 g L(-1), [As(V)]0 = 1.5 mM and I = 0.01 M NaCl] showed carbonate-enhanced As(V) uptake in the air-equilibrated systems at pH 4 and 6 and at pH 8 after 3 h of reaction. Suppressed As(V) adsorption was observed in the air-equilibrated system in the early stages of the reaction at pH 8. In the pseudo-equilibrium adsorption experiments [1 g L(-1), [As(V)]0 = 0.5 mM and I = 0.01 M NaCI], in which each pH value was held constant by a pH-stat apparatus, effects of dissolved carbonate on As(V) uptake were almost negligible at equilibrium, but titrant (0.1 M HCl) consumption was greater in the air-equilibrated systems (P(CO2) = 10(-3.5) atm) than in the CO2-free argon system at pH 4-7.75. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on iron octahedral via bidentate mononuclear ( 2.8 A) and bidentate binuclear (approximately equal to 3.3 A) bonding at pH 4.5-8 and loading levels of 0.46-3.10 microM m(-2). Using the results of the pseudo-equilibrium adsorption data and the XAS analyses, the pH-dependent As(V) adsorption under the P(CO2) = 10(-3.5) atm and the CO2-free argon system was modeled using surface complexation modeling, and the results are consistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest that the acid titrant consumption was strongly affected by changes to electrical double-layer potentials caused by the adsorption of carbonate in the air-equilibrated system. Overall results suggest that the effects of dissolved carbonate on As(V) adsorption were influenced by the reaction conditions [e.g., available surface sites, initial As(V) concentrations, and reaction times]. Quantifying the effects of adsorbed carbonate may be important in predicting As(V) transport processes in groundwater, where iron oxide-coated aquifer materials are exposed to seasonally fluctuating partial pressures of CO2(g).     

单糖和羧酸盐对酸性蛋白酶热稳定性的影响

文中应用动力学方法,较系统地研究了酸性蛋白酶的热稳定性.试验结果显示某些单糖及羧酸盐能够明显延长该酶在较高温度下的半寿期,其中甘露糖和半乳糖均可延长酶的半寿期达11倍以上,能够起到有效保护酸性蛋白酶的作用.     

单糖和羧酸盐对酸性蛋白酶热稳定性的影响

该文应用动力学方法,较系统地研究了酸性蛋白酶的热稳定性。试验结果显示,某些单糖及羧酸盐能够明显延长该酶在较高温度条件下的半寿期,其中甘露糖和半乳糖均可延长酶的半寿期达11倍以上,能够起到有效保护酸性蛋白酶的作用。     

工业发酵中溶氧因素的探讨

工业发酵影响因素很多,其中发酵液中的溶氧浓度(DissolvedOxygen,简称DO)是最基本因素,对微生物的生长和产物形成有着极其重要的影响。在发酵过程中,必须供给适量的无菌空气,菌体才能繁殖和积累所需代谢产物。不同菌种及不同发酵阶段的菌体的需氧量是不同的,发酵液的DO值直接影响微生物的酶活性、代谢途径及产物产量。发酵过程中氧的传质速率主要受发酵液中溶解氧的浓度和传递阻力影响。研究溶氧对发酵的影响及控制对提高生产效率、改善产品质量等都有重要意义。     

工业发酵中溶氧因素的探讨

工业发酵影响因素很多,其中发酵液中的溶氧浓度(DissolvedOxygen,简称DO)是最基本因素,对微生物的生长和产物形成有着极其重要的影响.在发酵过程中,必须供给适量的无菌空气,菌体才能繁殖和积累所需代谢产物.不同菌种及不同发酵阶段的菌体的需氧量是不同的,发酵液的DO值直接影响微生物的酶活性、代谢途径及产物产量.发酵过程中氧的传质速率主要受发酵液中溶解氧的浓度和传递阻力影响.研究溶氧对发酵的影响及控制对提高生产效率、改善产品质量等都有重要意义.     

Effects of the pesticide thiuram: genome-wide screening of indicator genes by yeast DNA microarray

Although there have been studies on the toxicity of the pesticide thiuram, the present study is the first one to attempt to integrate a whole genomic response using microarray technology. From the DNA microarray experiment it was found that exposure to thiuram led to alterations of gene expression in yeast cells and that many genes involved in detoxification and stress response were highly induced. The induced genes were classified according to the MIPS yeast database. The induction of genes concerned with folding and proteolysis reflects the protein denaturing and degradation effects of the thiuram treatment The induction of genes involved in redox and defense against reaction oxygen species also suggests that thiuram has other effects, such as oxidative stress. Genes classified for carbohydrate metabolism and energy were also highly induced, and these gene products may play the role of providing the energy for the detoxification mechanism. In addition, in view of the induction of some genes involved in DNA repair, thiuram potentially causes DNA damage. Therefore, as stated in previous reports, thiuram is a potential positive toxic chemical. On the other hand, YKL071W, YCR102C, YLR303W, and YLL057C were selected based on the result of a DNA microarray experiment and used for the promoter activity assay. Thiuram treatment affected the promoter of these genes, indicating that this technique could be used for the selection of biomarker candidates.     

罗红霉素分子印迹吸附树脂的制备及吸附性能研究

本文以罗红霉素（ROX）为模板分子,丙烯酰胺为功能单体,乙二醇二甲基丙烯酸酯为交联剂,偶氮二异丁腈为引发剂,D101树脂为载体,采用溶液聚合法,制备得到罗红霉素分子印迹D101树脂（ROX-MIP-D101）,采用红外光谱、扫描电镜初步表征了结构。通过静态和动力学吸附实验研究了ROX-MIP-D101对ROX的吸附性能。以红霉素（EM）为竞争底物,研究了ROX-MIP-D101对ROX的吸附选择性。结果显示,ROX-MIP-D101对ROX的静态平衡吸附量为253 mg/g,明显大于NIP-D101的静态平衡吸附量（211 mg/g）,说明其对ROX的吸附能力大于NIP-D101。ROX-MIP-D101对ROX和EM的分离因子为1.26,说明其对ROX具有较好的吸附选择性,而NIP-D101对ROX和EM的分离因子为1.01,基本没有选择性。重复使用性实验表明,ROX-MIP-D101的重复使用性能良好。环境水样的平均加标回收率达90.8%。      

天然彩丝的吸附性能研究

研究了天然彩丝对Fe2+、NNO和酸性橙Ⅱ的吸附性能,并与普通白丝进行了比较.结果表明:天然彩丝和普通白丝对Fe2+和酸性橙Ⅱ的吸附规律都可用Langmuir吸附模型近似描述,天然彩丝和普通白丝对表面活性剂NNO的吸附规律不能完全符合某种吸附等温线.当吸附达到平衡后,天然彩丝对Fe2+、NNO和酸性橙Ⅱ的平衡吸附量高于普通白丝.     

The effect of water temperature on the adsorption equilibrium of dissolved organic matter and atrazine on granular activated carbon

The influence of water temperature on the adsorption of natural dissolved organic matter (DOM) on activated carbon has not been investigated intensively yet. In this study, batch experiments with granular activated carbon (GAC) have been carried out at three temperatures (5 degrees C, 20 degrees C, 35 degrees C) using a humic acid model water and different types of surface water (lake, river, canal). Furthermore, the adsorption of an anthropogenic contaminant, atrazine, was quantified in the absence and presence of DOM. The results indicate a significant influence of water temperature on the adsorption equilibrium of DOM and atrazine. Contrary to expectations, DOM and atrazine adsorption in surface water tends to be increased with increasing water temperature, whereas the extent of this effect is dependent on the type and concentration of DOM. Furthermore, the temperature effect on atrazine adsorption is controlled by competition of DOM and atrazine on adsorption sites. Some assumptions are proposed and discussed for explaining the temperature effects observed in the batch studies.     

改性方式对红花籽粕可溶性膳食纤维理化性质和吸附特性的影响

为改善红花籽粕可溶性膳食纤维的部分理化性质和其吸附特性,以红花籽粕为原料,分别考察碱-酶法、酶-高温蒸煮法、碱-高温蒸煮法3种不同改性方式对其可溶性膳食纤维（SDF）的持水力、膨胀力、持油力等部分理化性质及对葡萄糖、阳离子、胆固醇和亚硝酸根离子吸附能力的影响。结果表明,碱-高温蒸煮法优于其他两种方法,碱-高温蒸煮法改性的红花籽粕SDF的持水力、膨胀力和持油力最佳,分别为5.58 g/g、3.98 mL/g和4.38 g/g;对葡萄糖吸附能力为16.08 mmol/g,在1% NaOH添加量为1～4 mL时,阳离子吸附效果最佳;在pH为2和7时,对胆固醇吸附能力分别为7.68 mg/g、10.14 mg/g,对亚硝酸盐吸附能力为56.43 μg/g、30.53 μg/g。     

磁性壳聚糖对铜的吸附性能研究与应用

目的建立基于磁性壳聚糖(magnetic chitosan,MCS)磁性富集,火焰原子吸收光谱法(flame atomic absorption spectrometry,FAAS)测定饮用水中铜含量的分析方法。方法以水热法合成MCS,以MCS为吸附材料, FAAS为检测手段,考察影响吸附和解析的重要条件。结果在pH 6.0下恒温40℃振荡35 min,铜能被MCS完全吸附,饱和吸附容量为28.2 mg/g,吸附在MCS上的铜可用4 mL 0.1 mol/L硝酸在20 min内完全洗脱。在该吸附和洗脱条件下建立测定铜的分析方法,线性范围为0.02～5.0 mg/L,检出限为6.2μg/L。该方法应用于水中铜的分析,在自来水、某品牌蒸馏水和公共直饮水中所测的铜含量分别为39.2、26.7、30.2μg/L,相对标准偏差(relative standard deviation, RSD)为1.6%～5.1%,加标回收率为95.9%～103%。结论该方法准确、灵敏,适用于生活饮用水中痕量铜的分析检测。     

橄榄渣膳食纤维理化和体外吸附特性

以橄榄果渣制备橄榄渣总膳食纤维（OPTDF）,测定其理化性质及体外模拟吸附性能,并从OPTDF中分离出可溶性膳食纤维（OPSDF）和不溶性膳食纤维（OPIDF）,采用X射线衍射、傅立叶红外光谱、电镜扫描对其结构进行表征。[JP2]结果表明,OPTDF的持水力、持油力、膨胀力及葡萄糖吸附值分别为（4.96±0.51） g/g,（2.45±0.26） g/g,（6.00±0.16） mL/g,（18.11±0.31） mmol/g;其对油脂、胆酸钠、胆固醇及NO-2有吸附能力;[JP]OPTDF、OPIDF呈纤维素I晶型,其结晶度分别为41.39%,46.07%,OPSDF呈非晶态结构;OPSDF中含有纤维素、氢键及醚键,可能含有聚木糖,纤维结构疏松多孔、片状层较为明显;而OPIDF中含有半纤维素、纤维素、木质素和氢键,纤维结构疏松、纤维束有一定的螺旋程度且交错缠绕形成网状结构。