Chronic toxicity of copper on embryo development in Chinese toad, Bufo gargarizans

This study examined the effects of copper exposure on embryonic development of Chinese toad, Bufo gargarizans. Firstly, the LC₅₀ values from 24 to 96 h of exposure were 3.61 × 10⁻⁶ M, by means of a 4 d toxicity test with B. gargarizans embryos. Secondly, Chinese toad embryos were exposed to 10⁻⁹-10⁻⁶ M copper from mid gastrula stage to operculum completion stage. Measurements included mortality, tadpole weight, tadpole total length, growth retardation, duration of different embryo stages and malformation. Embryonic survival was not affected by copper. Relative to control tadpoles, significantly decreased weight and total length were found at 10^-9-10^-6 M reduced percentage of the embryos in right operculum stage after 10 d exposure to copper and reduced percentage of embryos in operculum completion stage after 12 d exposure to copper were also observed. Moreover, the duration of embryonic development increased at neural, circulation and operculum development stage in copper-treated groups. For the scanning microscope and histological observation, the abnormalities were malformation of wavy dorsal fin, flexural tail, curvature body axis, yolk sac oedema and reduced pigmentation in the yolk sac. Histopathological changes in olfactory, retinal epithelium and skin were also observed. DNA strand breaks exposed to the copper were analyzed by DNA ladder. In conclusion, copper induced toxic effects on B. gargarizans embryos. The present study indicated chronic toxicity tests may provide more accurate way in formulating the “safe levels” of heavy metals to amphibian.     

Evidence for the inhibitory effects of silver nanoparticles on the activities of soil exoenzymes

Silver nanoparticles (AgNPs) are well known to have antimicrobial ability, but very little is known about the effect of AgNPs on soil exoenzyme activities, which reflect the potential of a soil to support biochemical processes. This study provides evidence of the inhibitory effects of AgNPs on the activities of soil exoenzymes. Six exoenzymes related to nutrient cycles (urease, acid phosphatase, arylsulfatase, β-glucosidase) and the overall microbial activity (dehydrogenase, fluorescein diacetate hydrolase) were tested in soils treated with AgNPs (1, 10, 100 and 1000 μg g(-1)) and silver ion (0.035, 0.175, 0.525, 1 and 1.5 μg g(-1)). AgNPs were capable of inhibiting the activities of all the exoenzymes tested in this study. Especially, the urease and dehydrogenase activities were significantly related to the presence of AgNPs. The effects of silver ions dissolved from the AgNPs were not significant, indicating the adverse effects caused by AgNPs themselves. This study suggested that AgNPs negatively affect soil exoenzyme activities, with the urease activity especially sensitive to AgNPs.     

Degradation of o-toluidine by fluidized-bed Fenton process: statistical and kinetic study

Background, aim, and scope  

The optimal conditions of o-toluidine degradation by fluidized-bed Fenton process were determined using Box–Behnken designs (BBD). The BBD can be used to find the optimal conditions in multivariable systems. The optimal conditions obtained by the design were further applied in the kinetic analysis of o-toluidine oxidation in fluidized-bed Fenton process.     

Monitoring of hexabromocyclododecane diastereomers in fish from European freshwaters and estuaries

Background and aims  

Hexabromocyclododecane (HBCD) is a brominated flame retardant used mainly in polystyrene foam as well as in textile applications. In recent years, measures were taken to reduce HBCD emissions during its production and use. To evaluate the efficacy of these measures, a monitoring project was initiated with fish as bioaccumulation indicators.     

Assessment of exposure to DDT and metabolites after indoor residual spraying through the analysis of thatch material from rural African dwellings

Introduction  

We report on the analysis of 4,4′-dichlorodiphenyltrichloroethane (4,4′-DDT) and its metabolites in thatch and branch samples constituting the wall materials of dwellings from South African subtropical areas. This approach was used to assess the exposure to DDT in the residents of the dwellings after indoor residual spraying (IRS) following recommended sanitation practices against malaria vectors.     

Pesticide removal from waste spray-tank water by organoclay adsorption after field application: an approach for a formulation of cyprodinil containing antifoaming/defoaming agents

Purpose  

Many reports on purification of water containing pesticides are based on studies using unformulated active ingredients. However, most commercial formulations contain additives/adjuvants or are manufactured using microencapsulation which may influence the purification process. Therefore, the main objective of this work was to develop and test a pilot scheme for decontaminating water containing pesticides formulated with antifoaming/defoaming agents.     

简单芽孢杆菌产高效微生物絮凝剂

通过从绿化植物根际土壤和污水处理厂的活性污泥中分离筛选絮凝剂产生菌,得到一株稳定高效的微生物絮凝剂产生菌PS1,根据形态学特征、生理生化实验以及16S rDNA序列分析将其鉴定为简单芽孢杆菌(Bacillus simplex)。对菌株PS1产生絮凝剂的最佳培养时间、絮凝活性分布以及pH、CaCl2、絮凝剂投量对絮凝效果的影响进行了研究,并考察了其对实际废水的絮凝效果。结果表明,菌株PS1产絮凝剂的最佳培养时间为36 h,产生的絮凝活性物质全部存在于发酵液离心后的上清液中;当pH为7.0～8.5、CaC12投量为0.25～0.35 g/L、发酵液投加量的体积分数为1.5%～2.5%时,菌株PS1发酵液对4 g/L的高岭土悬浊液的絮凝效果最佳,絮凝率达到97%。菌株PS1所产絮凝剂对城市污水、啤酒废水、淀粉废水、医院废水的絮凝率可达90%以上。     

氮掺杂TiO2可见光光催化剂的制备及性能

以尿素和钛酸丁酯为原料,通过溶胶-凝胶法低温下制备了高可见光催化活性的氮掺杂TiO2(NDT)光催化剂,采用XRD、TEM、BET和UV-Vis DRS等测试手段对其进行了表征,并在自制光催化反应器中降解甲基橙评价了样品的光催化活性。结果表明,当氮与钛的摩尔比为0.5∶1时,350℃焙烧的样品(NDT350)具有最佳的可见光光谱吸收和光催化活性,该催化剂为锐钛矿晶相,平均粒径为21 nm,比表面积为89.13 m2/g。可见光辐照下,NDT350降解甲基橙的表观反应速率常数为1.381×10-2min-1,是商业P25催化剂的16.85倍。NDT350优良的可见光催化活性与其大的比表面积和强烈的可见光光谱吸收有关。