Using polymer mats to biodegrade atrazine in groundwater: laboratory column experiments

Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats to deliver oxygen into groundwater to induce biodegradation of the pesticides atrazine, terbutryn and fenamiphos contaminating groundwater in Perth, Western Australia. The polymer mats, composed of woven silicone (dimethylsiloxane) tubes and purged with air, were installed in 2-m-long flow-through soil columns. The polymer mats proved efficient in delivering dissolved oxygen to anaerobic groundwater. Dissolved oxygen concentrations increased from <0.2 mg l(-1) to approximately 4 mg l(-1). Degradation rates of atrazine in oxygenated groundwater were relatively high with a zero-order rate of 240-380 microg l(-1) or a first-order half-life of 0.35 days. Amendment with an additional carbon source showed no significant improvement in biodegradation rates, suggesting that organic carbon was not limiting biodegradation. Atrazine degradation rates estimated in the column experiments were similar to rates determined in laboratory culture experiments, using pure cultures of atrazine-mineralising bacteria. No significant degradation of terbutryn or fenamiphos was observed under the experimental conditions within the time frames of the study. Results from these experiments indicate that remediation of atrazine in a contaminated aquifer may be achievable by delivery of oxygen using an in situ polymer mat system.     

面向生态城市的水资源供需平衡分析

提出了面向生态城市的水资源供需平衡分析原则,强调了水质水量的统一性,人与自然的和谐性,生态环境需水的优先性.在此基础上,建立了面向生态城市的水资源供需平衡分析概念框架,并对供需平衡的基本内涵进行了界定.以广州为例,进行了实证研究.结果表明,生态环境需水对供需平衡状态影响显著,2000年花都区与中心区非汛期分别缺水0.91,4.86亿m3/月;基本控制方案下,各目标年(2005,2010,2020年)全市非汛期缺水量将分别高达19.74,41.78,77.62亿m3/月;实施以污染负荷控制和节水为主导的综合强化方案才能保证供需平衡.     

Analysis of pollution status of River Illo,Ota, Nigeria

An assessment of the pollution status of River Illo, located within River Owo catchments area in Ota, Ogun State, Nigeria, was carried out. The River’s response to deoxygenation due to BOD loading from an abattoir and its dissolved oxygen (DO) level was predicted using the modified Streeter-Phelps model. The average concentrations of measured parameters at the sampling stations include: 2.24 mg/l of DO, 312.85 mg/l of BOD, 782.86 mg/l of chemical oxygen demand, and 620.76 g/l of total solids. The DO model for River Illo showed a positive correlation between measured and calculated DO, while the dissolved oxygen curve gave a double spoon shape of two major segments with distinct zones of degradation, decomposition, and recovery. The self-purification factor (f) for both segments ranged between 0.8 and 1.1 depicting River Illo as a slow moving or sluggish river. The above results revealed slow reaeration of the water body while full recovery from pollution was difficult. The treatment of River Illo before usage is very essential to ensure public health safety of users from waterborne diseases.     

Influence of thermal environment on metallographic structure characteristics of the electric arc bead pattern

Electrical apparatuses are prone to arc, which generally causes a fire, even an explosion hazard, when a flammable gas mixture is present, especially during industrial processes. Terrible fire scenes are challenging for fire investigations. In this work, by performing a simultaneous thermal analysis test we simulated a fire environment and found that as the oxygen concentration decreased, the oxidation/exothermic peak temperature of ‘cause’ bead became higher, but the melting temperature was unaffected. Results indicated that the bead pattern underwent oxidation at approximately 831 °C, melting initiated at approximately 1060 °C, and the pattern then disappeared. The melted pattern grain changes were divided into three critical temperature stages: Approximately 600 °C, the onset temperature at which the melted pattern grains began to be equiaxed; approximately 831 °C, at which the grains were interspersed with oxygen-containing material; and 831–1060 °C, when the grains disappeared, which is a criterion for identifying electrical fires. However, the boundaries remained throughout the thermal environment process. Moreover, the bead pattern demonstrated three metallographic regions: Deep layer (Region I), the intermediate layer (Region Ⅱ), and surface layer (Region Ⅲ). Region I was the most thermally sensitive, in which equiaxed crystals first appeared. Region Ⅲ was the thermal reaction lag zone, in which the typical branching crystals finally disappeared, and Region Ⅱ was intermediate between Regions I and Ⅲ. The results may help fire investigators determine the fire scene temperature stages and provide support for fire evidence extraction.     

活性污泥中需氧量的研究现状及供氧系统的节能技术

叙述了国内外活性污泥法中需氧量的研究过程及微孔曝气系统的节能技术，对微孔曝气器与穿孔曝管进行对比，证实前者较后者节电４４％．     

活性污泥数学模型中异养菌产率系数测定方法的研究

采用间歇活性污泥法和呼吸计量法测定活性污泥数学模型中异养菌产率系数.研究结果表明,间歇活性污泥法测定结果受试验控制条件特别是污泥有机负荷的影响非常大,且试验周期比较长;人工配水条件下,呼吸计量法测定异氧菌产率系数(YH)在0.71以上,比活性污泥数学模型推荐值高,其结果与底物性质有关,该方法准确性高,重现性良好.     

S–O–C isotopic picture of sulphate–methane–carbonate system in freshwater lakes from Poland. A review

Microbial oxidation of organic compounds (including methane), in freshwater sediments, may result in precipitation of carbonates, which may become an important geochemical archive of paleoenvironmental variations. Most probably low δ¹³C value in calcite in eutrophic systems results from an advanced oxidation of organic compounds in turbulent or/and sulphate-rich conditions. Likewise, high δ¹³C value in calcite from organic-rich sediments may evidence low redox potential of the freshwater system. Oxidation of methane and organic matter results in significant isotope effects in sulphates dissolved in water. Therefore, to better understand the origin of carbon isotope signal in carbonates, concentration and stable isotope measurements in dissolved sulphate (water column), bubble methane and calcite (freshwater sediments) have been carried out in 24 lakes, 2 ponds and 4 rivers in Poland. The highest concentration of sulphate has been detected in rivers (85.47 SO₄ ²⁻ mg/l) and an artificial lake (70.30 SO₄ ²⁻ mg/l) located in the extremely SO₄ ²⁻-polluted region called the “Black Triangle”. The lowest concentration of sulphate is found in dystrophic and mountain lakes (from 0.5 SO₄ ²⁻ to about 3 mg/l). The lowest δ³⁴S(SO₄ ²⁻) and δ¹⁸O(SO₄ ²⁻) values occur in unpolluted lakes in eastern Poland (−0.94 and 1.38‰, respectively). The highest S and O isotopic ratios are found in a polluted lake in western Poland (δ¹⁴S(SO₄ ²)=12.95‰) and in a dystrophic lake in eastern Poland (δ¹⁸O(SO₄ ²) = 16.15‰) respectively. It is proposed that δ³⁴SO₄ ²⁻ and (¹⁸O(SO₄ ²⁻) values in lakes represent a good tool to assess and quantify anthropogenic impact by acid precipitation and to monitor variations in the trophic state and redox processes controlled by biodegradation of organic compounds in sediments and water column. In general, increasing depth (up to 12 m) of the water column is associated with decreasing trend the δ¹³C(CH₄) value from about –35 to about –78‰. However, δ¹³C value in sedimentary calcite (δ¹³C vary from –10 to 0.5‰) shows opposite trends as compared to the corresponding methane. This is probably due to redox processes and distribution of heavy isotopes between methane and calcite. Likewise, turbulent water (river) show high δ¹³C value in methane and low δ¹³C value in calcite—this is probably due to an enhanced oxidation of methane producing ¹³C-depleted CO₂. In contrast to clean lakes, it is observed that an increase of the δ¹³C(CH₄) value occurs with increasing depth of the water column in a strongly SO₄ ²⁻-contaminated lake. This is probably due to a loss of biological buffering potential of the lake accompanied by an active oxidation of methane precursors.     

A cost worth paying: energetically expensive interactions with males protect females from intrasexual aggression

When approached by males, females of the Amarillo fish (Girardinichthys multiradiatus) perform a behaviour called vibration or they are aggressively challenged. We quantified vibration and assessed whether it compromises the rate of feeding attempts in dyads kept in outdoor enclosures. Male approaches resulted in female vibration and in a reduced feeding rate. Vibration was not evoked by female–female aggression, which was frequent and always ended in the subordinate fleeing from the dominant female. Using a closed respirometer we found that vibration is costly; oxygen consumption of females was greater in the presence of a male (which evoked vibration) than in the presence of a non-familiar female (when no vibration occurred). By recording interactions of females confined in aquaria in the presence and in the absence of males, we confirmed that escaping is the only available response to deal with female aggression. Females kept without males participated in frequent aggressive (even lethal) interactions that did not abate while the subordinate female was in sight of the dominant, and which caused premature births and injuries. Yet in the alternative treatment aggression ceased when a male approached, prompting vibration in both females. Thus, in the Amarillo, in as much as it evokes energetically costly female vibrations, male courtship is an expression of sexual conflict. However, in the absence of males, frequent female aggression potentially annuls the benefits of not vibrating. We propose that a complete appraisal of the consequences of sexual conflict must include an assessment of the costs imposed by intra-sexual interactions.     

微电解工艺处理染料工业废水研究

该文研究了采用微电解工艺处理染料工业废水.经过微电解工艺处理的染料工业废水色度和化学需氧量(COD)去除率分别为93.94%和64.62%.废水的可生化性提高,生化速率常数K从0.02876提高到0.04754.微电解工艺预处理该染料工业废水的吨水运行成本为0.91元.     

苏州河底泥的耗氧量

对苏州河底泥耗氧量(SOD)的实验测定结果表明,苏州河底泥(北新泾下游)的夏季耗氧强度是冬季的6倍,最大强度发生在武宁路河段,达7500mg/m2