Cosolvent-enhanced chemical oxidation of perchloroethylene by potassium permanganate

A laboratory study was conducted to examine cosolvent-enhanced in-situ chemical oxidation (ISCO) of perchloroethylene (PCE) using potassium permanganate (KMnO4). The conceptual basis for this new technique is to enhance permanganate oxidation of dense non-aqueous phase liquids (DNAPLs) with the addition of a cosolvent, thereby increasing DNAPL solubility while avoiding mobilization. Among 17 cosolvent candidates screened, tertiary butyl alcohol (TBA) and acetone were the most stable in the presence of KMnO4, both of which increased PCE aqueous solubility significantly, and therefore are suitable to be used as cosolvent in this study. Batch experiments indicated that the second-order rate constant for PCE oxidation by potassium permanganate was 0.043+/-0.002 M(-1) s(-1) in the purely aqueous (no cosolvent) solution. In the presence of 20% cosolvent (volume fraction=fc=0.2), the rate constant decreased to 0.036+/-0.003 M(-1) s(-1) with TBA and to 0.031+/-0.002 M(-1) s(-1) with acetone. However, in the presence of free-phase PCE, chloride ion concentration from PCE oxidation in acetone/water solutions (fc=0.2) was about twice that in aqueous solutions, indicating that the increase in PCE solubility more than compensated for the decrease in reaction rate constant, such that the oxidation efficiency of PCE was increased with cosolvent. A complete chlorine mass balance was observed in the aqueous system, whereas approximately 70% was obtained in TBA/water or acetone/water (fc=0.2). In soil columns containing residual DNAPL and subjected to isocratic flushing with step-wise increases in f(c) cosolvent, TBA at fc=0.2 resulted in PCE mobilization, whereas acetone at fc相似文献   

Numerical simulation of reactive processes in an experiment with partially saturated bentonite

Bentonites are preferred materials for use as engineered barriers for high-level nuclear waste repositories. Simulation of geochemical processes in bentonite is therefore important for long-term safety assessment of those repositories. In this work, the porewater chemistry of a bentonite sample subject to simultaneous heating and hydration, as studied by Cuevas et al. [Cuevas, J., Villar, M., Fernández, A., Gómez, P., Martín, P., 1997. Porewaters extracted from compacted bentonite subjected to simultaneous heating and hydration. Applied Geochemistry 12, 473-481.], was assessed with a non-isothermal reactive transport model by coupling the geochemical software PHREEQC2 with the object-oriented FEM simulator GeoSys/RockFlow. Reactive transport modelling includes heat transport, two-phase flow, multicomponent transport and geochemical reactions in the liquid phase, i.e. ion exchange, mineral dissolution/precipitation and equilibrium reactions. Simulations show that the easily soluble minerals in bentonite determine the porewater chemistry. Temperature affects both two-phase flow and geochemical reactions. Porosity change due to dissolution/precipitation is low during the experiment. However, changes of the effective porosity caused by bentonite swelling can be very large. The simulated results agree well with the experimental data.     

Effects of metsulfuron-methyl on the microbial population and enzyme activities in wheat rhizosphere soil

The effects of metsulfuron-methyl, a sulfonylurea herbicide, on the wheat soil microorganisms were evaluated by the methods of microbial inoculation culture, and the activities of three enzymes were measured using the colorimetric method. The tolerant microorganisms that can resist 500 microg x g(-1) metsulfuron-methyl in the counting culture medium were studied specially. Metsulfuron-methyl distinctly inhibited the common aerobic heterotriphic bacteria, but the effects on common fungi and common actinomycete were not evident. In the meantime, the number of tolerant fungi increased greatly in the rhizosphere after the application of metsulfuron-methyl in contrast to the significant decrease of the amount of tolerant actinomycete. It indicates that fungi might turn into the dominant microbial type and actinomycete is the sensitive factor in the soil polluted by sulfonylurea residues. The population of aromatic compounds-decomposing bacteria, aerobic azotobacter, and nitrite bacteria all increased in the earlier period, but the aerobic azotobacter decreased rapidly in number 30 days later, and the amount of nitrite bacteria also showed a temporary decrease with time 15 days later. However, the denitrifying bacteria just began to increase significantly after the crops had grown for 50 days. The amount of sulfur-oxidizing bacteria gradually decreased with the growth of crops, and so were the sulfate-reducing bacteria after metsulfuron-methyl application. To all types of microorganisms, there were more microbes in rhizosphere samples than those in nonrhizosphere except aerobic azotobacter. It means the growth of wheat root system can stimulate the growth of most microorganisms. The activities of hydrogen peroxidase and polyphenol oxidase in soil samples after metsulfuron-methyl application were notably lower than those in the control, and the difference of the activities between the samples of rhizosphere and nonrhizosphere was evident. On the contrary, the activity of dehydrogenase was not inhibited by the application of metsulfuron-methyl, and the rhizosphere effect was not obvious either.     

水中氯化物测定的不确定度评定

根据硝酸银滴定法测定水中氯化物的含量，分析了该方法测量不确定度的来源，评定了水中氯化物的测量不确定度，在各不确定度中，以标准溶液配制与样品分析时滴定消耗的硝酸银体积引入的不确定度较大。     

武汉市青山区大气中NO_x污染的调查及其影响因素的初步探讨

应用“盐酸萘乙二胺分光光度法”测定了武汉市青山区大气中NO_x的含量,并考察了时间、地点、汽车流量诸因素对这一地区大气中NO_x含量的影响。研究表明该地区NO_x含量较高,防治空气中NO_x的污染已迫在眉睫。     

Monitoring seasonal distribution of an endangered anadromous sturgeon in a large river using environmental DNA

Monitoring dynamic distribution is crucial to conservation management of anadromous sturgeons, but traditional survey methods are less efficient for low-density populations in a large river. Natural propagation of Chinese sturgeon has been monitored annually mainly at the spawning ground using netting for eggs and hydroacoustics for broodstock. However, absence of spawning was observed sporadically in recent years, indicating further crises for the declining population. We analyzed eDNA of water samples collected from 24 sites across 1360 km of the migratory route of anadromous Chinese sturgeon in the middle and lower reaches of the Yangtze River. Chinese sturgeon was detected at 9 sites during the spawning season and 14 sites after the spawning season. We found that positive eDNA detection rates remained constant in the middle reaches but dramatically changed in the lower reaches, reflecting seasonal migration pattern of Chinese sturgeon. Invasive sturgeons were detected in the river, indicating their possible escape from aquaculture facilities. This study established a protocol for the use of eDNA to monitor distribution of Chinese sturgeon and could be valuable in making better policies for the conservation of this endangered species.     

盐城湿地大米草-芦苇群落对生活污水净化效果的实验研究

大米草、芦苇群落对COD、N、P和NH4-N等污染物有着明显的净化作用,这对潮间带水质稳定起着积极的作用.研究发现在同一淹水深度下,随着群落盖度的增加,芦苇与大米草对有机物、N,P的净化能力也随之增强;而随着淹水深度的增加,大米草对COD的去除率在淹水深度为30 cm时效果最佳;而芦苇群落对COD去除率随淹水深度的增加呈缓慢下降的趋势.光照能够促进湿地植物群落对污染物的净化,但受植物群落垂直结构与淹水深度的影响很大.在群落盖度大于60%、淹水深度为30 cm与当前水质条件下,大米草、芦苇二者联合净化作用在一个潮周期内对有机物、N、P和NH4-N分别可达33.6、24.9、20.8和27.6%以上.     

山东省农业循环经济发展评价

为了加快农业循环经济发展，首先要对发展状态进行评估。该文以循环经济理论为依据，探索建立表征农业循环经济发展程度的指标体系，并以山东省17市为例，进行主成分分析，评价山东省各市农业循环经济发展程度，找出各地农业循环经济发展过程中存在的差距，为推动区域农业循环经济发展提供理论支持。研究发现各地区农业循环经济发展程度与区域总体发展水平并不一致，一些经济发达地区忽视农业资源的节约利用导致农业循环经济发展水平不高。为加快出东省农业循环经济发展，建议通过推进农业产业化，节约资源投入；大力推广农业清洁生产；合理规划和确立农业循环经济发展模式。     

浅论环境保护公众参与信息发布系统的构建

公众参与是环境保护工作一项重要内容。从中国实际情况来看，公众参与信息发布方式与手段已不能适应经济、社会发展的要求。本文主要介绍了基于应用信息网络技术改进公共服务，重组公共组织，提高公共参与的原理和涉及的相关技术。讨论了利用面向对象的分析和设计方法、分布式数据库技术、三层结构的网站建设技术、C／S和B／S网络技术结合移动通讯和网络接口技术的公众参与信息发布系统设计，探讨利用互联网及移动通讯技术实现公众便捷地参与对专项规划和建设项目环境影响评价的模式。