Toxicity of the nerve agent tabun to Daphnia magna,a new experimental species in military toxicology

Daphnia magna, a freshwater microcrustacean, is currently tested as an alternative experimental species in research dealing with nerve agents poisonings treatment. Because of this, the toxicity of the nerve agent tabun (a cyanide-group containing organophosphate) to Daphnia had to be examined by estimating the EC₅₀ values. The immobilization of daphnids was chosen as the end-point. It was found that D. magna is sensitive to small amounts of tabun, even after 15 min exposure, and tabun toxicity increases with time. The estimated EC₅₀ values for 15, 30, 45, and 60 min exposure were as follows: 67.39, 38.10, 26.95, and 21.9 μg l^?1. In addition, the toxicity of media to which tabun was added 24 h before the start of experiments was examined. The results obtained indicate that daphnids can be used in experiments with nerve-agent intoxication treatment.     

Response of stormwater retention basins to two chemical aquatic weed control methods

The City of Winnipeg, Canada has 70 stormwater retention basins (SRBs) whose primary function is to act as land-drainage, storage reservoirs within the city. The ponds often become choked with vegetation and this disenchants property owners who have been led to believe, by subdivision developers, that the ponds are pristine ‘lakes’. The City has implemented some control measures to help alleviate customer dissatisfaction by removing vegetation using the herbicides Karmex-DF and Reglone-A. For this study, in order to evaluate herbicide control methods, water quality was assessed on 10 occasions, biweekly over the 5 months of a Canadian summer (May to September), on 37 of the SRBs. Various water quality parameters were determined, including total suspended solids (TSS), chlorophyll-a, turbidity, transparency, ammonia, nitrate, orthophosphate, temperature, dissolved oxygen, and pH. By comparing the water quality data resulting from the two aquatic weed control measures, it was established that neither herbicide method seemed to be as effective as the natural ability of the ponds to limit vegetative growth. It is suggested that utilization of the herbicide as a long-term aquatic weed control measure should therefore proceed with caution and perhaps, other alternative methods of control could also be investigated.     

磷酸盐改性方解石去除水中磷酸盐研究

使用磷酸盐溶液和方解石之间的反应得到方解石去除水中磷酸盐后的产物,即磷酸盐改性方解石,通过实验对比分析了方解石和磷酸盐改性方解石对水中磷酸盐的去除动力学,并考察了磷酸盐改性方解石去除水中磷酸盐的各种影响因素。磷酸盐改性方解石对水中磷酸盐的去除能力明显优于方解石。当反应时间为2h时,实验条件下磷酸盐改性方解石对水中磷的去除率达到72%,而方解石对磷的去除率仅为35%。当pH为5~7时,磷酸盐改性方解石对水中磷酸盐的去除能力较高;当pH由7增加到10 h,对磷酸盐的去除能力略微下降;当pH由10增加到12 h,对磷酸盐的去除能力急剧下降。磷酸盐改性方解石对水中磷酸盐的单位去除量随初始磷质量浓度的增加而增加。过高的初始磷质量浓度会导致磷酸盐改性方解石对水中磷酸盐的去除率过低。磷酸盐改性方解石对水中磷酸盐的去除能力随反应温度的升高而增加。磷酸盐改性方解石对水中磷酸盐的去除动力学可以较好地采用准二级动力学模型加以描述。水中共存的钙离子有利于磷酸盐改性方解石对磷酸盐的去除,而水中共存的碳酸氢根离子抑制了磷酸盐改性方解石对磷酸盐的去除。磷酸盐改性方解石去除水中磷酸盐的主要机制是磷酸钙沉淀作用。磷酸盐改性方解石不仅会为磷酸钙沉淀反应的异质成核提供核心,促进磷酸钙沉淀的形成,而且当水处于对方解石不饱和状态时会溶解释放出可溶性钙,为磷酸钙沉淀的形成提供钙源。上述结果表明,方解石去除水中磷酸盐后的产物可以被再次用于水中磷酸盐的去除,并且对磷酸盐的去除效果优于原始的方解石。     

大骨节病区硒元素分布的调控机理研究——以四川省阿坝地区为例

分析了阿坝地区的岩石、饮用水、农作物及其根系土中硒的不同存在形态的分布,并结合生物有效性深入研究了硒元素分布与大骨节病病因的联系和调控机理.阿坝地区的环境(岩石、土壤、水)中全硒浓度、农作物中硒的富集系数和水溶性硒占总硒的含量均远低于非病区;硒在氧化还原条件(Eh平均值143.27 mV)和酸碱度(pH 6.51—8.48)的控制下主要以亚硒酸态的稳定形式存在.元素铝、铁等的富集可能会促进硒的沉淀和络合,制约硒的生物有效利用率,进而导致人体硒摄入不足,最终激发人类微小病毒B19(HPV B19)的毒性,引发大骨节病.通过采取土壤增施硒肥、改善水质、改变膳食结构等方法可以有效地提高环境中硒的水平及其生物有效性,以缓解大骨节病的病情及发病率.     

化学沉淀结合Fenton法预处理脱硫废液的原理与效果分析

脱硫废液因含有高浓度氰化物、硫氰化物、硫化物等有毒组分而影响焦化废水处理的生物工艺.以焦化企业产生的实际脱硫废液为研究对象,选用化学沉淀-Fenton氧化的串联方法尝试预处理及分析方法的可行性,通过单因素实验,考察了硫酸亚铁投加剂量、反应前后溶液pH值、反应时间3种条件对脱硫废液中总氰及易释放氰去除效果的影响,在优化条件下对经硫酸亚铁沉淀后的脱硫废液残液进行Fenton氧化实验.结果表明,当硫酸亚铁投加量为理论值的1.2倍,H2O2投加量为COD当量的0.3倍时,可使脱硫废液的COD去除率达到76.65%,使初始浓度分别为327.7、704.6和2087.3 mg.L-1的氰化物、硫氰化物及硫化物基本得到去除,为后续生物处理创造了有利条件.化学沉淀结合Fenton法是脱硫废液预处理效率高且实用的方法.     

Prevention in the chemical and process industries: Future directions

This paper presents the current trends of future-oriented prevention management in the chemical-using industry. Two concepts leading to the next generation of managing prevention within chemical industrial areas are explained and discussed. The first concept concerns integrated design-based safety and security; the second concerns the collaboration of several chemical plants to increase sustainable development of their activities and their environment.     

大同盆地浅层地下水水质影响因素分析

主要分析了降雨入渗补给、山前侧向补给、地表水入渗补给、引污灌溉的入渗补给及地下水排泄过程对大同盆地浅层地下水水质的影响。通过对盆地浅层地下水水质实测资料的分析,了解了这些因素综合影响着地下水水质。分析了大同盆地浅层地下水受污染原因,建议该地区必须控制污染源,同时建立和完善水环境监测体系。     

Young convict cichlids use visual information to update olfactory homing cues

In this study, we tested the tendency of young cichlids to orient towards their parents using chemical cues. Convict cichlids have biparental defence of their free-swimming young. If young become separated from their family they must rejoin their family within minutes to have any chance of survival. Here, we used a dichotomous Y-maze to test if displaced convict cichlid young can use chemical cues to orient to their family. First, we showed that young preferentially orient toward water taken from their home tank versus blank water taken from a tank that contained no fish. Second, we showed that young prefer home tank water to water from a tank containing another family of convict cichlids. In a third experiment, we placed young convict cichlids in a small aquarium inserted within a larger aquarium. The large aquarium contained either their parents or no fish. The small insert aquarium contained blank water from a tank that had never contained fish. After 20 min in the insert tank, young convict cichlids were placed in the Y-maze and given a choice between either their home tank water or water from the insert tank. Convict cichlids that did not see their parents during the 20-min conditioning period oriented strongly toward chemical cues of their home tank water. Young that saw their parents during the 20-min conditioning period oriented strongly toward the chemical cues of the insert tank. These data indicate that young convict cichlids use visual cues to learn and reset the smell of “home” in less than 20 min.     

Initial phase modelling in numerical explosion applied to process safety

The utilisation of computational fluid dynamics (CFD) in process safety has increased significantly in recent years. The modelling of accidental explosion via CFD has in many cases replaced the classical Multi Energy and Brake Strehlow methods. The benefits obtained with CFD modelling can be diminished if proper modelling of the initial phase of explosion is neglected. In the early stages of an explosion, the flame propagates in a quasi-laminar regime. Proper modelling of the initial laminar phase is a key aspect in order to predict the peak pressure and the time to peak pressure. The present work suggests a modelling approach for the initial laminar phase in explosion scenarios. Findings are compared with experimental data for two classical explosion test cases which resemble the common features in chemical process areas (confinement and congestion). A detailed analysis of the threshold for the transition from laminar to turbulent regime is also carried out. The modelling is implemented in a fully 3D Navier–Stokes compressible formulation. Combustion is treated using a laminar flamelet approach based on the Bray, Moss and Libby (BML) formulation. A novel modified porosity approach developed for the unstructured solver is also considered. Results agree satisfactorily with experiments and the modelling is found to be robust.     

A study of maintenance-related major accident cases in the 21st century

This paper is based on a review of 183 detailed, major accident investigation and analysis reports related to the handling, processing and storage of hydrocarbons and hazardous chemicals over a decade from 2000 to 2011. The reports cover technical, human and organizational factors. In this paper, the Work and Accident Process (WAP) classification scheme is applied to the accident reports with the intention of investigating to what extent maintenance has been a cause of major accidents and what maintenance-related causes have been the most frequent.The main objectives are: (1) to present more current overall statistics of maintenance-related major accidents, (2) to investigate the trend of maintenance-related major accidents over time, and (3) to investigate which maintenance-related major accident causes are the most frequent, requiring the most attention in the drive for improvement.The paper presents statistical analysis and interpretation of maintenance-related major accidents’ moving averages as well as data related to the types of facility, hazardous substances, major accidents and causes. This is based on a thorough review of accident investigation reports.It is found that out of 183 major accidents in the US and Europe, maintenance was linked to 80 (44%) and that the accident trend is decreasing. The results also show that “lack of barrier maintenance” (50%), “deficient design, organization and resource management” (85%) and “deficient planning/scheduling/fault diagnosis” (69%) are the most frequent causes in terms of the active accident process, the latent accident process and the work process respectively.