短芽孢杆菌RL-2絮凝机理研究

由编号为RL-2的短芽孢杆菌(Bacillus brevis)产生的生物高分子,经研究发现是一种对高岭土悬液有较高絮凝活性的阴离子型絮凝剂.对絮凝剂的热处理及酶处理表明,其活性成分为多糖;经茚三酮试验,Molish反应,薄层色谱及红外光谱分析表明,该絮凝剂为一种阴离子型多糖絮凝剂;ζ电位测定及絮凝剂与高岭土颗粒之间结合键的检测表明,絮凝剂与高岭土颗粒间的结合力为氢键,絮凝过程基于"桥联"机理;絮凝剂和高岭土在絮凝剂的活性部位--多糖中的羟基或羧基以氢键相结合,经架桥作用絮凝沉淀.     

The interactions of phthalate esters with suspended particulate material in fresh and marine waters

The behaviour of six phthalate esters in the presence of particulate material suspended in fresh and saline water has been examined. The adsorption of all phthalates by the particulates is enhanced by the presence of salt. The adsorption process is fairly rapid ( <2-3 h) and the degree of adsorption depends on the characteristics of the particulates. Di-ethylhexyl phthalate is adsorbed most actively by material of a small particle size. The adsorption of other phthalates is more strongly influenced by the chemical composition of the particulates and is most closely correlated with their lipid content.     

Photocatalytic mechanisms of indoleamine destruction by the quinalphos metabolite 2-hydroxyquinoxaline: a study on melatonin and its precursors serotonin and N-acetylserotonin

The redox-active quinalphos main metabolite, 2-hydroxyquinoxaline, is particularly effective under excitation by light. We have studied the photocatalytic destruction of melatonin and its precursors, because the cytoprotective indoleamine has been detected in high quantities in mammalian skin. In photooxidation reactions, in which melatonin, N-acetylserotonin and serotonin are destroyed by 2-hydroxyquinoxaline, the photocatalyst is virtually not consumed. Rates of melatonin and serotonin destruction are not changed by the singlet oxygen quencher 1,4-diazabicyclo-(2,2,2)-octane, indicating that this oxygen species is not involved in the primary reactions, so that the persistence of 2-hydroxyquinoxaline has to be explained by redox cycling. This should imply formation of an organic radical, presumably the quinoxaline-2-oxyl radical, from which 2-hydroxyquinoxaline is regenerated by electron abstraction from indolic radical scavengers. Electron donation by 2-hydroxyquinoxaline is demonstrated by reduction of the 2,2'-azino-bis-(3-ethylbenzthiazolinyl-6-sulfonic acid) cation radical under ultrasound excitation. The compound 2-hydroxyquinoxaline interacts with the specific superoxide anion scavenger Tiron. Formation of oligomeric products from melatonin and serotonin is strongly inhibited by sodium dithionite. Products from photocatalytic indolamine conversion are predominantly dimers and oligomers. No kynuramines were detected in the case of serotonin oxidation, and melatonin's otherwise prevailing oxidation product N(1)-acetyl-N(2)-formyl-5-methoxykynuramine, another cytoprotective metabolite, is only formed in relatively small quantities. The proportion between products from melatonin is changed by 1,4-diazabicyclo-(2,2,2)-octane: singlet oxygen, also formed under the influence of excited 2-hydroxyquinoxaline, only affects secondary reactions.     

Numerical simulation of smoke plumes from large oil fires

A large eddy simulation (LES) model of smoke plumes generated by large outdoor pool fires is presented. The plume is described in terms of steady-state convective transport by a uniform ambient wind of heated gases and particulate matter introduced into a stably stratified atmosphere by a continuously burning fire. The Navier-Stokes equations in the Boussinesq approximation are solved numerically with a constant eddy viscosity representing dissipation on length scales below the resolution limits of the calculation. The effective Reynolds number is high enough to permit direct simulation of the large-scale mixing over two to three orders of magnitude in length scale. Particulate matter, or any non-reacting combustion ;product, is represented by Lagrangian particles which are advected by the fire-induced flow field. Background atmospheric motion is described in terms of the angular fluctuation of the prevailing wind, and represented by random perturbations to the mean particle paths. Results of the model are compared with two sets of field experiments.     

Photocatalytic mechanisms of indoleamine destruction by the quinalphos metabolite 2-hydroxyquinoxaline: a study on melatonin and its precursors serotonin and N-acetylserotonin

The redox-active quinalphos main metabolite, 2-hydroxyquinoxaline, is particularly effective under excitation by light. We have studied the photocatalytic destruction of melatonin and its precursors, because the cytoprotective indoleamine has been detected in high quantities in mammalian skin. In photooxidation reactions, in which melatonin, N-acetylserotonin and serotonin are destroyed by 2-hydroxyquinoxaline, the photocatalyst is virtually not consumed. Rates of melatonin and serotonin destruction are not changed by the singlet oxygen quencher 1,4-diazabicyclo-(2,2,2)-octane, indicating that this oxygen species is not involved in the primary reactions, so that the persistence of 2-hydroxyquinoxaline has to be explained by redox cycling. This should imply formation of an organic radical, presumably the quinoxaline-2-oxyl radical, from which 2-hydroxyquinoxaline is regenerated by electron abstraction from indolic radical scavengers. Electron donation by 2-hydroxyquinoxaline is demonstrated by reduction of the 2,2′-azino-bis-(3-ethylbenzthiazolinyl-6-sulfonic acid) cation radical under ultrasound excitation. The compound 2-hydroxyquinoxaline interacts with the specific superoxide anion scavenger Tiron. Formation of oligomeric products from melatonin and serotonin is strongly inhibited by sodium dithionite. Products from photocatalytic indolamine conversion are predominantly dimers and oligomers. No kynuramines were detected in the case of serotonin oxidation, and melatonin's otherwise prevailing oxidation product N ¹-acetyl-N ²-formyl-5-methoxykynuramine, another cytoprotective metabolite, is only formed in relatively small quantities. The proportion between products from melatonin is changed by 1,4-diazabicyclo-(2,2,2)-octane: singlet oxygen, also formed under the influence of excited 2-hydroxyquinoxaline, only affects secondary reactions.     

Pollution and the Planetary Albedo

Addition of cloud nuclei by pollution can lead to an increase in the solar radiation reflected by clouds. The reflection of solar energy by clouds already may have been increased by the addition of man-made cloud nuclei. The albedo of a cloud is proportional to optical thickness for thin clouds, but changes more slowly with increasing thickness. The optical thickness is increased when the number of cloud nuclei is increased. Although the changes are small, the long-term effect on climate can be profound.     

Ozone injection into an activated carbon bed to remove hydrogen sulfide in the presence of concurrent substances

Adsorption using activated carbon is one of the most reliable techniques for preventing odor by substances such as H2S. Concurrent substances in effluent gas often reduce the removal capacity of activated carbon for H2S. As a means of restoring capacity under such conditions, ozone injection into an activated carbon column was examined. When activated carbon was saturated with substances such as toluene, ethanol, n-butanol, or iso-butanol, its capacity to remove H2S decreased in proportion to the amount of the saturating substance. Under such conditions, ozone injection greatly increased capacity. Toluene, which is not easily decomposed by ozone, was displaced by ozone and by oxidized products of H2S. Ethanol, which is adsorbed in small amounts by activated carbon and easily decomposed by ozone, was removed by ozone injection. Butanols, which are also decomposed by ozone and adsorbed in large quantities by activated carbon, showed intermediate behavior between that of toluene and ethanol.     

On the escape of pollutants from urban street canyons

Pollutant transport from urban street canyons is numerically investigated using a two-dimensional flow and dispersion model. The ambient wind blows perpendicular to the street and passive pollutants are released at the street level. Results from the control experiment with a street aspect ratio of 1 show that at the roof level of the street canyon, the vertical turbulent flux of pollutants is upward everywhere and the vertical flux of pollutants by mean flow is upward or downward. The horizontally integrated vertical flux of pollutants by mean flow at the roof level of the street canyon is downward and its magnitude is much smaller than that by turbulent process. These results indicate that pollutants escape from the street canyon mainly by turbulent process and that the net effect of mean flow is to make some escaped pollutants reenter the street canyon. Further experiments with different inflow turbulence intensities, inflow wind speeds, and street aspect ratio confirm the findings from the control experiment. In the case of two isolated buildings, the horizontally integrated vertical flux of pollutants by mean flow is upward due to flow separation but the other main results are the same as those from the control experiment.     

控制城市垃圾焚烧二噁（口英）产生与扩散方法

控制垃圾焚烧二产生与扩散分三部分首先,通过预处理除去原生垃圾中的聚氯乙烯塑料,从源头上控制垃圾焚烧二哄产生的物质基础;其次,垃圾焚烧炉采用组合式循环流化床锅炉,实行垃圾先低温热解气化,然后高温燃烧垃圾热解气体的方式,同时在炉内加入添加剂实现稳定燃烧和部分脱氯,以减少二哄在炉内生成和炉后形成量;最后,在烟气尾部采用吸附剂吸附二哄,并与布袋除尘器配套使用,控制二哄的尾部扩散.该工艺具有成本低、控污效率高等优点,特别适用于发展中国家的垃圾焚烧二哄控制.     

泥炭作为吸油材料的试验

为了研制一种理想的吸油剂,对泥炭、秸秆、锯末和改性泥炭用作吸油材料进行了对比试验.结果表明,未改性的风干泥炭吸油效果好于秸秆和锯末,而且是藓类泥炭吸油效果好于草本泥炭;对于同一类型的泥炭,中细纤维结构的吸油量高于中粗纤维结构的;与未改性的风干泥炭相比,不论采用物理方法还是物理化学方法进行改性,改性后泥炭的吸油效果均好于改性前的.试验证明了泥炭可以作为一种吸油材料,尤其是改性后的泥炭更是一种效率高、成本低、环保型的吸油材料.     

Potential application of a semi-quantitative method for mercury determination in soils, sediments and gold mining residues

An alternative, low cost method for analyzing mercury in soil, sediment and gold mining residues was developed, optimized and applied to 30 real samples. It is semiquantitative, performed using an acid extraction pretreatment step, followed by mercury reduction and collection in a detecting paper containing cuprous iodide. A complex is formed with characteristic color whose intensity is proportional to mercury concentration in the original sample. The results are reported as range of concentration and the minimum detectable is 100 ng/g. Method quality assurance was performed by comparing results obtained using the alternative method and the Cold Vapor Atomic Absorption Spectrometry techniques. The average results from duplicate analysis by CVAAS were 100% coincident with alternative method results. The method is applicable for screening tests and can be used in regions where a preliminary diagnosis is necessary, at programs of environmental surveillance or by scientists interested in investigating mercury geochemistry.     

The mechanism and kinetics of ultrasound-enhanced electrochemical oxidation of phenol on boron-doped diamond and Pt electrodes

The research on ultrasound (US) enhanced electrochemical oxidation of Phenol (Ph) on boron-doped diamond (BDD) and Pt electrodes is studied. The enhancement by US on BDD is much greater than for Pt. With the assistance of US, the degradation rate and current efficiency on BDD are increased by 301% and 100%, respectively, while those on Pt are 51% and 49%. The difference of the enhancement on these two electrodes is caused by the fact that mass transport, adsorption amount and electrode reaction affected by US on BDD are different from those of Pt. The kinetics investigation on intermediates formed during electrochemical degradation show that the variety of intermediates produced on BDD is less than for Pt. In the presence of US, on both electrodes, no change occurred to the amounts of the intermediate species. However, time for intermediates to reach the highest concentration is cut down. This effect for degradation of Ph on BDD is more obvious than for Pt. The present research indicates that BDD is suitable for degradation of Ph by US assisted electrochemical oxidation.     

城市污水处理厂污泥作为矿山废弃地复垦土壤基质的可行性分析

以具有代表性的、运行技术成熟的污水处理厂的污泥为对象,对污水处理厂处理后的污泥进行好氧发酵堆肥,并对堆肥过程中的主要参数进行控制,对城市污水处理厂污泥作为矿山废弃地复垦土壤基质进行了可行性分析。     

Acetochlor as a soil pollutant

Acetochlor is a widely used herbicide all over the world. Similarly to other organic pollutants, the environmental fate of the acetochlor is strongly related to its adsorption properties. Static adsorption equilibrium measurements were carried out at 25 degrees C on different types of Hungarian soils characterized by varying amounts of organic matter and pH values. Isotherms obtained under different conditions, as well as on various soils, exhibit a similar shape, thus indicating a two-step adsorption process. The plots cannot be interpreted according to the classes of isotherms suggested by Giles. The adsorption coefficients (K) were estimated from the initial slope of the curves. These values were determined not only by the type of the soil, but also by the composition of the aqueous media. The organic matter adsorption coefficients (Kom) were also calculated and they were approximately identical for soils of high organic matter. Due to the low value of the adsorption coefficients, the acetochlor is a rather mobile pollutant of the soil posing a potential danger to the aquatic environment. For soils with high organic content, the Kom values are similar to each other and, due to the significant coverage of the inorganic surfaces, the adsorption is controlled by the solute-organic substance interactions. The adsorption of weakly polar compounds, however, is remarkable even on those soils where the organic content is low. In this case, the binding is governed by the solute-inorganic surface interactions. This conclusion is nicely proved by the adsorption of the acetochlor on quartz. According to our hypothesis, the second part of the adsorption step is controlled by the solute-adsorbed solute interactions. The role of the organic matter in this region of the isotherm is probably negligible. As the organic matter content of the soils plays an important role in the acetochlor adsorption, humic substances must have a strong influence upon the transport of this compound. Experiments to obtain adsorption isotherms of further pesticides and the development of a quantitative model are in progress.     

New insights into pesticide photoprotection

Photolysis may be a significant route of pesticide dissipation on crops, leading to an increase of pesticide use. Spraying strong absorbing compounds (photoprotector) along with pesticide is an attractive strategy to prevent the photodegradation phenomenon. The aim of this study is to get a better understanding of the parameters governing the photoprotection efficiency. Experiments were conducted using formulated sulcotrione as a pesticide and a grape wine extract as a photoprotector. These compounds were irradiated using simulated solar light as dried deposits on carnauba wax films or on disks of tobacco leaves and analyzed by ultra performance liquid chromatography ultraviolet (UV), spectroscopy, and microscopy. It is shown that photolysis is faster on leaves than on carnauba wax and that the photoprotection effect of grape wine extract is more efficient on leaves than on wax. Images recorded by microscopy bring evidence that deposits are very different on the two supports both in the absence and in the presence of the photoprotector. The grape wine extract plays a double role; it is antioxidant and UV screen. Photoprotection by the grape wine extract is a complex mixing of UV screen and antioxidant effects. The UV screen effect can be rationalized by considering the rate of light absorption by sulcotrione. Our results demonstrate that the rates of sulcotrione phototransformation are mainly governed by the repartition of the deposit on the solid support.     

First-passage-time transfer functions for groundwater tracer tests conducted in radially convergent flow

Forced-gradient groundwater tracer tests may be conducted using a variety of hydraulic schemes, so it is useful to have simple semi-analytic models available that can examine various injection/withdrawal scenarios. Models for radially convergent tracer tests are formulated here as transfer functions, which allow complex tracer test designs to be simulated by a series of simple mathematical expressions. These mathematical expressions are given in Laplace space, so that transfer functions may be placed in series by simple multiplication. Predicted breakthrough is found by numerically inverting the composite transfer function to the time-domain, using traditional computer programs or commercial mathematical software. Transport is assumed to be dictated by a radially convergent or uniform flow field, and is based upon an exact first-passage-time solution of the backward Fokker–Planck equation. These methods are demonstrated by simulating a weak-dipole tracer test conducted in a fractured granite formation, where mixing in the injection borehole is non-ideal.     

Scavenging of soluble trace gases by falling rain droplets in inhomogeneous atmosphere

We analyze non-isothermal absorption of trace gases by the rain droplets with internal circulation which is caused by interfacial shear stresses. It is assumed that the concentration of soluble trace gases and temperature in the atmosphere varies in a vertical direction. The rate of scavenging of soluble trace gases by falling rain droplets is determined by solving heat and mass transfer equations. In the analysis we accounted for the accumulation of the absorbate in the bulk of the falling rain droplet. The problem is solved in the approximation of a thin concentration and temperature boundary layers in the droplet and in the surrounding air. We assumed that the bulk of a droplet, beyond the diffusion boundary layer, is completely mixed and concentration of the absorbate and temperature are homogeneous and time-dependent in the bulk. By combining the generalized similarity transformation method with Duhamel's theorem, the system of transient conjugate equations of convective diffusion and energy conservation for absorbate transport in liquid and gaseous phases with time-dependent boundary conditions is reduced to a system of linear convolution Volterra integral equations of the second kind which is solved numerically. Calculations are performed using available experimental data on concentration and temperature profiles in the atmosphere.It is shown than if concentration of a trace gas in the atmosphere is homogeneous and temperature in the atmosphere decreases with height, beginning from some altitude gas absorption is replaced by gas desorption. Neglecting temperature inhomogenity in the atmosphere described by adiabatic lapse rate leads to essential overestimation of the trace gas concentration in a droplet on the ground.     

Macrodispersion by diverging radial flows in randomly heterogeneous porous media

Radial flow takes place in a heterogeneous porous formation where the transmissivity T is modelled as a stationary random space function (RSF). The steady flow is driven by a given rate, and the mean velocity is radial. A pulse-like of a tracer is injected in the porous formation, and the thin plume spreads due to the fluctuations of the velocity which results a RSF as well. Transport is characterized by the mean front, and by the second spatial moment of the plume. We are primarily interested in tracer macrodispersion modelling. With the neglect of pore-scale dispersion, macrodispersion coefficients are computed at the second order of approximation, without neglecting the head-gradient fluctuations. Although transport is non-ergodic at the source, it is shown that ergodicity is achieved at small distances from the source. This is due to the fact that close to the source local velocities are quite large, and therefore solute particles become uncorrelated very soon. Under ergodic conditions, we compare macrodispersion mechanism in radial flows with that occurring in mean uniform flows. At short distances the spreading effect is highly enhanced by the large variability of the flow field, whereas at large distances transport exhibits a lesser dispersion due to the reduction of velocities. This supports the explanation provided by Indelman and Dagan (1999) to justify why the macrodispersivity is found smaller than that pertaining to mean uniform flows. The model is tested against a tracer transport experiment (Fernàndez-Garcia et al., 2004) by comparing the theoretical and experimental breakthrough curves. The accordance with real data, that is achieved without any fitting to concentration values, strengthens the capability of the proposed model to grasp the main features of such an experiment, the approximations as well as experimental uncertainties notwithstanding.     

基于TM数据和ANN的河流水质参数监测研究

以珠江水系广州河段为研究对象,联合使用遥感（RS）和人工神经网络（ANN）技术对珠江水质进行分析监测。这种技术主要是利用GIS对RS图像进行地理定位,然后利用RS专用软件提取定位点的RS数据,最后通过建立前馈误差反传人工神经网络（BP网络）,确定TM数据前5个波段在定位点的反射率与水质3个主要参数的映射关系,即建立RS数据与水质的映射模型。经过检验,该技术监测误差小于16%,基本能满足当前实际需要。     

Air pollution detection by satellites: The transport and deposition of air pollutants over oceans

Research is continuing towards the possible detection of air pollution by remote sensing techniques, and satellite imagery has been examined to find evidence of cross-Atlantic transport of air pollution. Pollution masses from industrial areas are often carried out over the Atlantic Ocean by tropospheric winds. However, the pollution mass is generally steered by convergent flows and fronts of extra-tropical cyclones, and wet deposition and scavenging of air pollutants within clouds occur primarily over the cold ocean, especially during the occlusion stage of a cyclone. As a result, the oceanic area from Cape Hatteras to 1500 km ENE of Newfoundland (the SW sector of the Icelandic low area) is often a ‘dumping ground’ (sink region) for air pollution from N America.However, a dust cloud generated by a volcanic eruption and a smoke plume from large-forest fires in western N America have been observed near the W coast of Europe. Saharan dust carried to N America by trade winds have been identified on satellite imagery. The massive smoke generation by large forest fires in Siberia is also identified in the present study. The results of research on forest fire smoke are currently being used by scientists studying the atmospheric effects of a large-scale nuclear war. It is suggested that the area between the S of Japan and the SW section of the Aleutian low is another principal sink of air pollutants and dust originating from NE Asia.