MWNTs/TiO2光催化降解氧乐果农药影响因素及动力学研究

通过合成多壁碳纳米管/二氧化钛(MWNTs/TiO_2)复合光催化剂,研究其对氧乐果农药的降解效率和作用机理,为去除水体中农药提供高效环保的水处理技术。通过溶胶-凝胶法制备MWNTs/TiO_2复合光催化剂,其中钛酸丁酯:异丙醇:水摩尔比为1∶25∶3、MWNTSs为0.5 g、MWNTSs与TiO_2质量比为100∶1.5。采用批实验法考察了复合材料投加量(200、400、600、800、1 000 mg/L)、溶液p H值(3、5、7、9、11)、氧乐果初始浓度(20、75、150 mg/L)、温度(15℃、25℃、35℃)、光照强度(385、560 W)等因素对其降解效果的影响,对比了MWNTs/TiO_2和TiO_2两种催化剂对降解效果,并通过SEM和EDS等手段对MWNTs/TiO_2复合光催化剂进行表征。结果表明,TiO_2均匀覆盖在MWNTs上,其中TiO_2占复合光催化剂的质量分数为59.59%;MWNTs/TiO_2复合光催化剂对氧乐果的降解效率受复合材料投加量、溶液p H值、氧乐果初始浓度、温度、光照强度等因素影响较大,在氧乐果初始浓度75 mg/L、MWNTs/TiO_2投加量600 mg/L、p H值为3、温度35℃及光照强度560 W最佳条件下,MWNTs/TiO_2对氧乐果的光催化降解率为60.71%。降解动力学分析发现降解过程符合一级反应动力学方程,降解速率常数为0.0033 h-1。在同样的条件下,MWNTs/TiO_2复合光催化剂比TiO_2降解效率提高了8.45%。     

Kinetics of the release of dissolved organic matter (DOM) from air‐dried and pre‐moistened soil material

In this study, the kinetics of soil organic matter (SOM) dissolution from soil samples in different states of moisture was investigated, using a continuous extraction method. The investigation distinguished three processes of SOM dissolution. They include an initial, fast process (probably hydrophilic dissolved organic matter) and two slow, rate limited processes, which probably correspond to hydrophobic dissolved organic matter (DOM). The second process indicates a slow, continuous release of DOM, whereas the third process is determined by a power law. The rate of the third process strongly depends on temperature and state of moisture. It is diffusion limited, with the diffusion control probably being located in the solid soil organic matter. This was explained by a gel structure, which slowly forms in the hydrating SOM and allows diffusion of mobile particles of SOM. The results show the importance of considering the moisture state of SOM for the kinetics of DOM dissolution.     

Kinetic Study of the Degradation of Ethiofencarb in Aqueous Solutions

A kinetic study of the hydrolysis of ethiofencarb (α-ethylthio-o-tolyl methylcarbamate) in pure water and in aqueous solutions at pH 2, 6, 9 and 12 and at three different temperatures (4, 20 and 50(±1)°C) has been carried out using a gas chromatographic nitrogen-phosphorus detection method. The values of the first-order rate constants (k) for the degradation reaction were calculated. The values for k were found to be dependent on pH and temperature. No acid hydrolysis was observed in any case. Complete degradation of ethiofencarb was observed at pH 12 at all three temperatures; it was practically instantaneous at room temperature. Ethiofencarb was also completely degraded at pH 9 at 20 and 50°C, while in pure water (pH 6) degradation took place at 50°C but not at 20°C. Ethiofencarb was not degraded in pure water at lower temperatures and, due to the reversible nature of the reaction, at equilibrium about 80% of the pesticide remained undegraded at room temperature. © 1997 SCI.     

草鱼肾细胞中双氟沙星代谢酶的酶动学

细胞色素P450s(CYPs)主要参与动物体内药物代谢。水产养殖中不合理的联合用药常会导致治疗失败,这通常与CYP活性的诱导有关。然而,关于鱼类CYP的诱导却知之甚少。为获得有关CYP诱导的信息,实验采用反相高效液相色谱(RP-HPLC)的方法测定了草鱼肾细胞(CIK)中CYPs的特异性诱导剂对双氟沙星(DIF)的代谢作用及酶动学分析。对照组和β-萘黄酮(BNF)诱导组的酶动学方程分别为1/V=0.1375×1/[S]+0.003和1/V=0.0245×1/[S]+0.0013。DIF与经BNF处理的CIK共孵育后,其代谢量增加了1倍,酶动学参数Clint和Vmax值分别增加了7倍和2倍。BNF是CYP1A的特异性诱导剂,因此,CYP1A可能参与了DIF的代谢。     

Increased activity associated with reduced sensitivity of acetylcholinesterase in organophosphate-resistant greenbug,schizaphis graminum (homoptera: aphididae)

The activity and sensitivity of acetylcholinesterase (AChE, EC 1.1.1.7) from an organophosphate-susceptible (OSS) and three resistant (OR-0, OR-1 and OR-2) strains of the greenbug (Schizaphis graminum) were biochemically compared. All three resistant strains displayed higher frequencies of individuals with respect to both increased activity of AChE toward the model substrate acetylthiocholine (ATC) and reduced sensitivity of AChE to inhibition by paraoxon as compared with the OSS strain. Kinetic study indicated that AChE from the OR-0, OR-1 and OR-2 strains had 3.3-, 2.7- and 2.3-fold, respectively, lower affinity, but 1.5-, 2.2- and 2.0-fold, respectively, higher catalytic activity toward ATC than AChE from the OSS strain. Significantly increased activity of AChE in the resistant strains was also confirmed by non-denaturing polyacrylamide gel electrophoresis, and appeared to be associated with the increase of general esterase activity. Inhibition kinetics revealed that AChE from the OR-0, OR-1 and OR-2 strains was 2.1-, 2.2- and 2.7-fold less sensitive to inhibition by paraoxon than that from the OSS strain. The study suggested that both qualitative and quantitative modifications of AChE had evolved in the resistant strains and were likely to significantly enhance the overall resistance level in greenbugs. © 1999 Society of Chemical Industry     

Effect of residence time on the kinetics of nonexchangeable ammonium release from illite and vermiculite

The fraction of nonexchangeable ammonium (NH₄⁺) can play an important role in N cycling of soils as a sink (fixation) or a source (release) of NH₄⁺. Recently fixed nonexchangeable NH₄⁺ especially seems to be a significant source for N release. The aim of our study was to determine the effect of residence time on the kinetics of nonexchangeable NH₄⁺ release from illite and vermiculite. Calcium-saturated illite and vermiculite, containing NH₄⁺ that was “fixed” for one and 60 d, were extracted with a H-resin for 0.25 to 384 h. Both clay minerals “fixed” significantly more NH₄⁺ in 60 d than in 1 d, but vermiculite “fixed” more NH₄⁺ than illite. The kinetics of nonexchangeable NH₄⁺ release from illite and vermiculite were well described by the Elovich equation and by a heterogeneous diffusion model. In vermiculite the percentage of nonexchangeable NH₄⁺ release decreased from 84% to 78% when the time of fixation increased from 1 to 60 d. In illite time of residence has not influenced the complete release of newly fixed NH₄⁺.     

砷在铜藻中的亚细胞分布及细胞壁吸附作用研究

为揭示铜藻(Sargassum horneri)细胞壁在砷(As)生物吸附中的作用,以铜藻幼苗为研究对象,测定了不同As胁迫浓度(50、100、150、200、250μmol·L^-1)下细胞亚组分中的As含量变化,并对细胞壁的吸附动力学、细胞壁多糖As吸附效果以及细胞壁多糖傅里叶红外光谱进行了分析研究。结果表明：在低浓度(50μmol·L^-1)As胁迫时,50.0%的As分布于细胞壁,明显高于其他组分;而在高浓度(≥150μmol·L^-1)As胁迫时,As优势分布由细胞壁转向细胞可溶组分,细胞壁中的As比例下降至36.4%～37.3%。随着As胁迫浓度升高,细胞壁As含量呈上升趋势,当As胁迫浓度超过100μmol·L^-1时,细胞壁As含量上升趋于平缓。细胞壁吸附动力学实验表明酯化改性和甲基化改性可降低细胞壁As吸附的平衡容量,其降幅分别为68.5%和42.9%,同时细胞壁多糖红外光谱分析结果也表明羟基、氨基、羧基、硫酸盐基等官能团为细胞壁As吸附提供了结合位点。细胞壁多糖体外吸附实验表明随着多糖浓...     

土壤中乙羧氟草醚残留分析方法及降解动态研究

利用气相色谱仪建立了土壤中乙羧氟草醚残留量的分析检测方法,并在实验室条件下研究了其在河南潮土、吉林黑土、江西红壤中的降解动态,为其环境和生态安全性评价提供重要的科学依据。结果表明:①土壤中的乙羧氟草醚残留物用丙酮-乙酸乙酯(1∶2,V/V)混合液提取,经弗罗里硅土SPE柱净化,浓缩后用气相色谱仪(带63Ni-ECD)进行检测;当添加浓度为0.01、0.05、0.5mg.kg-1时,添加回收率为86.9%～98.3%,标准偏差为1.50%～9.99%,最低检出量为1×10-12g,最低检出浓度为0.01mg.kg-1。②乙羧氟草醚在3种不同类型的土壤中降解速率大小依次为河南潮土>吉林黑土>江西红壤,降解速率常数分别为9.92×10-2、6.42×10-2和2.89×10-2,降解半衰期分别为7.0、10.8和24.0h,符合一级动力学方程。土壤pH值对乙羧氟草醚的降解有显著影响,乙羧氟草醚在碱性土壤中降解较快,在酸性土壤中降解较慢。根据国内农药在土壤中的残留性划分标准,乙羧氟草醚为易降解农药。     

陶瓷载体固定化酵母细胞啤酒连续发酵动力学研究

采用陶瓷拉西环载体固定化酵母细胞,进行啤酒连续发酵,对发酵中的菌体生长、底物消耗、酒精生成等过程进行了动力学研究,建立了相应的动力学模型,并进行了参数拟合。发现当反应器体积为84.8 L、麦汁流量大于6.2 L/h时,拟合效果较好。     

甘蔗品种抗旱性光合生理指标及其综合评价

利用相关、主成分、聚类和判别分析, 研究有关生理生化指标与甘蔗抗旱性关系. 结果表明: (1)中度水分胁迫下, MDA含量和PMP有不同程度地提高, 而Fv/Fm、 Fv/Fo、ΔFv/Fo、ΔFv/Ft和T1/2 有不同程度地降低, 变化的幅度因供试品种基因型而异. (2)PMP与MDA含量呈极显著正相关, 而与Fv/Fm、 Fv/Fo及ΔFv/Fo呈显著负相关; Fv/Fm与F