地下水曝气修复技术现场试验与应用研究进展

结合近年来国内外地下水曝气修复现场工程实践,对原位曝气的设计、操作和监测技术进行了全面的综述。对原位设计中的相关参数进行了整理分析,给出了合理取值范围,并探讨了不同场地条件下的应对方法。发展新的监测技术(如示踪技术、新型传感器等)能使曝气系统的工作性能得到更有效的监测,对于曝气修复工程现场监测新技术进行了系统的归纳和总结。此外,对现场曝气修复效果影响因素如污染物类型、曝气方式、曝气井数量、最大生物降解速率、土体孔隙率和含水层有机碳含量等进行了分析,以利于实际操作工艺的优化。最后对未来地下水曝气修复现场试验研究需开展的工作进行了展望。     

Chemical fate,latitudinal distribution and long-range transport of cyclic volatile methylsiloxanes in the global environment: A modeling assessment

Cyclic volatile methylsiloxanes (cVMS) such as octamethycyclotetrasiloxane (D4), decamethycyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) are widely used as intermediates in the synthesis of high-molecular weight silicone polymers or as ingredients in the formulation of personal care products. The global environmental fate, latitudinal distribution, and long range transport of those cVMS were analyzed by two multimedia chemical fate models using the best available physicochemical properties as inputs and known persistent organic pollutants (POPs) and highly persistent volatile organic chemicals (“fliers”) as reference. The global transport and accumulation characteristics of cVMS differ from those of typical POPs in three significant ways. First, a large fraction of the released cVMS tends to become airborne and is removed from the global environment by degradation in air, whereas known POPs have a tendency to be distributed and persistent in all media. Secondly, although cVMS can travel a substantial distance in the atmosphere, they have little potential for deposition to surface media in remote regions. This contrasts with a deposition potential of known POPs that exceeds that of cVMS by 4–5 orders of magnitude. Thirdly, cVMS have short global residence times with the majority of the global mass removed within 3 months of the end of release. Global residence times of POPs on the other hand are in years. The persistent fliers resemble the cVMS with respect to the first two attributes, but their global residence times are more like those of the POPs.     

Growth and photosynthetic responses to copper in wild grapevine

The present study evaluates the tolerance and accumulation potential of Vitis vinifera ssp. sylvestris under moderate and high external Cu levels. A greenhouse experiment was conducted in order to investigate the effects of a range of external Cu concentrations (0–23 mmol L⁻¹) on growth and photosynthetic performance by measuring gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments. We also measured the total copper, nitrogen, phosphorus, sulphur, calcium, magnesium, iron, potassium and sodium concentrations in the plant tissues. All the experimental plants survived even with external Cu concentrations as high as 23 mmol L⁻¹ (1500 mg Cu L⁻¹), although the excess of metal resulted in a biomass reduction of 35%. The effects of Cu on growth were linked to a reduction in net photosynthesis, which may be related to the effect of the high concentration of the metal on photosynthetic electron transport. V. vinifera ssp. sylvestris survived with leaf Cu concentrations as high as 80 mg kg⁻¹ DW and growth parameters were unaffected by leaf tissue concentrations of 35 mg Cu kg⁻¹ DW. The results of our study indicate that plants of V. vinifera ssp. sylvestris from the studied population are more tolerant to Cu than the commercial varieties of grapevine that have been studied in the literature, and could constitute a basis for the genetic improvement of Cu tolerance in grapevine.     

Trends of PCDD/F and PCB concentrations and depositions in ambient air in Northwestern Germany

Time series of polychlorinated dioxins and furans (PCDD/F) and polychlorinated biphenyls (PCB) in ambient air of a large conurbation in North-Western Germany are presented and analyzed. The trend of PCDD/F concentrations, starting from as early as 1988, shows a pronounced decrease by at least one order of magnitude, demonstrating that the emission reductions were effective. The PCDD/F depositions also have decreased by a factor of 5 since 1992. However, both trends have leveled out since 2005. Time series of PCB concentrations and depositions starting in 1994 show only slight decreases for the concentrations and almost no decrease for the depositions. From the decay rates following first order kinetics, half-lives in the order of 5-15 years for the PCDD/F and 15-31 years for the sum of the six indicator PCB could be calculated, which are much longer than the half-lives estimated from their reactivity towards the OH radical. Apparently, small fresh emissions (PCDD/F), considerable secondary emissions and evaporation from contaminated soils slow down their decay in the atmosphere of big conurbations. Analyzing the decay rates of individual PCB congeners shows that the lower chlorinated and more volatile ones are removed faster than the higher chlorinated congeners, probably via gas phase reactions with the OH radical. It can be concluded from the present study that the input of PCDD/F and PCB into the food chain via the air path will continue for another one or two decades in big conurbations.     

A_2型高粱细胞质雄性不育系与其保持系的胞质DNA和核DNA差异

以高粱细胞质雄性不育系A2 V4 (A)及其保持系V4 (B)的总DNA为模板 ,对 184个随机引物进行筛选 ,找到6个其RAPD扩增产物在A/B间存在稳定差异的引物 .将该 6个引物同时扩增A/B的总DNA、线粒体DNA(mtDNA)及叶绿体DNA(cpDNA) .以总DNA为模板时得到 12个扩增片段 ,以mtDNA为模板时得到 4个 ,以cpDNA为模板时得到 11个 .结果分析表明 ,在这些扩增片段中 ,有 7个仅仅出现在以胞质DNA为模板的扩增中 ,有 5个在以总DNA和胞质DNA为模板时同时出现 ,即认为这 12个片段来自胞质DNA .另有 7个片段 ,在以胞质DNA为模板时未出现 ,而是仅仅出现在以总DNA为模板的扩增中 ,认为是来自核DNA .来自核DNA的 7个扩增片段中 ,有 5个来自保持系 ,有 2个来自不育系 ,这表明 ,不育系与保持系在核DNA上存在差异 .对A/B核DNA在CMS中的重要性及研究对策进行了讨论 .图 2表 4参 19     

Diel Cycling of Zinc in a Stream Impacted by Acid Rock Drainage: Initial Results from a New in situ Zn Analyzer

Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a novel instrument, the Zn-DigiScan, to continuously monitor in situ zinc concentrations in near real-time. Initial results from a 3-day deployment at Fisher Creek, Montana have demonstrated the ability of the Zn-DigiScan to record diel Zn cycling at levels below 100 μg/l. Longer deployments of this instrument could be used to examine the effects of episodic events such as rainstorms and snowmelt pulses on zinc loading in streams affected by acid rock drainage.     

Metals in biomass

Background, Aim and Scope

Metal ions generally share the ability/tendency of interacting with biological material by forming complexes, except possibly for the heavy alkali metals K, Rb and Cs. This is unrelated to the metals being either essential for sustaining life and its reproduction, apparently insignificant for biology, although perhaps undergoing bioconcentration or even being outright toxic, even at low admission levels. Yet, those different kinds of metal-biomass interactions should in some way depend on properties describing coordination chemistries of these very metals. Nevertheless, both ubiquitously essential metals and others sometimes used in biology should share these properties in numeric terms, since it can be anticipated that they will be distinguished from nonessential and/or toxic ones. These features noted above include bioconcentration, the involvement of metal ions such as Zn, Mg, Cu, Fe, etc. in biocatalysis as crucial components of metalloenzymes and the introduction of a certain set of essential metals common to (almost) all living beings (K, Mg, Mo, Mn, Fe, Cu and Zn), which occurred probably very early in biological evolution by ‘natural selection of the chemical elements’ (more exactly speaking, of the metallomes).

Materials and Methods

The approach is semiempirical and consists of three consecutive steps: 1) derivation of a regression equation which links complex stability data of different complexes containing the same metal ion to electrochemical data pertinent to the (replaced) ligands, thus describing properties of metal ions in complexes, 2) a graphical representation of the properties-two typical numbers c and x for each metal ion-in some map across the c/x-space, which additionally contains information about biological functions of these metal ions, i.e. whether they are essential in general (e.g. Mg, Mn, Zn) or, for a few organisms of various kinds (e.g. Cd, V), not essential (e.g. rare earth element ions) or even generally highly toxic (Hg, U). It is hypothesized that, if coordination properties of metals control their biological ‘feasibility’ in some way, this should show up in the mappings (one each for mono and bidentate-bonding ligands). 3) eventually, the regression equation produced in step 1) is inverted to calculate complex stabilities pertinent to biological systems: 3a) complex stabilities are mapped for ligands delivered to soil (-water) by green plants (e.g. citrate, malate) and fungi and, compared to their unlike selectivities and demands of metal use (photosynthesis taking place or not), 3b) the evolution of the metallome during late chemical evolution is reconstructed.

Results

These maps show some ‘window of essentiality’, a small, contrived range/area of c and x parameters in which essential metal ions gather almost exclusively. c and x thus control the possibility of a metal ion becoming essential by their influencing details of metal-substrate or (in cases of catalytic activities) metal-product interactions. Exceptions are not known to be involved in biocatalysis anyhow.

Discussion

Effects of ligands secreted, e.g. from tree roots or agaric mycelia to the soil on the respective modes (selectivities) of metal bioconcentration can be calculated by the equation giving complex stability constants, with obvious ramifications for a thorough, systematic interpretation of biomonitoring data. Eventually, alterations of C, N and P-compounds during chemical evolution are investigated — which converted CH₄ or CO₂, N₂ and other non-ligands to amino acids, etc., for example, with the latter behaving as efficient chelating ligands: Did they cause metal ions to accumulate in what was going to become biological matter and was there a selectivity, a positive bias in favour of nowessential metals (see above) in this process? Though there was no complete selectivity of this kind, neither a RNA world in which early ribozymes effected most of biocatalysis, nor a paleoatmosphere containing substantial amounts of CO could have paved the way to the present biochemistry and metallomes.

Conclusions

This way of reasoning provides a causal account for abundance distributions described earlier in the Biological System of Elements (BSE; Markert 1994, Fränzle &; Markert 2000, 2002). There is a pronounced change from chemical evolution, where but few transformations depended on metal ion catalysis to biology.

Recommendations and Perspectives

The application of this numerical approach can be used for modified, weighted evaluation of biomonitoring analytical data, likewise for the prediction of bioconcentration hazards due to a manifold of metal ions, including organometallic ones. This is relevant in ecotoxicology and biomonitoring. In combining apoproteins or peptides synthesized from scratch for purposes of catalysing certain transformations, the map and numerical approaches might prove useful for the selection of central ions which are even more efficient than the ‘natural’ ones, like for Co²⁺ in many Zn enzymes.

     

Identification of Pollution Source of Cadmium in Soil. Application of Material Flow Analysis and A Case Study in Taiwan (11 pp)

Background Since the 1970s, at least 200 hectares (ha) of farmland has been polluted by the heavy metal cadmium (Cd).Consequently, the Cd pollution has led to contaminate the rice production and caused acute social panic. According to the recent investigation results performed by the Taiwan Environmental Protection Administration (TEPA), it is indicated that most of the Cd pollution incidents in Taiwan resulted from the wastewater discharge of stearate Cd factories. To prevent the Cd pollution incidents from spreading, the TEPA has either forced these factories to close down or assisted them in improving their production processes since the 1980s. Unfortunately, accidental incidents of Cd pollution still emerge in an endless stream, despite the strict governmental controls placed on these questionable factories. Whether this pollution has resulted from undetected or hidden pollution sources stemming from two decades ago or comes from some new source, will be an outstanding issue. Therefore, this study attempts to identify the pollution sources of Cd in soil in Taiwan as well as to find the solution to the above-mentioned, outstanding issue by way of a methodology termed Material Flow Analysis (MFA). Method logy. The MFA has proved to be a useful tool on providing quantitative information of the flow of substances through an economic to an environmental system. Based upon the supply-and-demand theory of MFA, researchers have successfully conducted an overview of the use of materials in many industries, the construction industry being one of these. Therefore, this study tries to establish a set of analytical processes by way of MFA for identifying the pollution source of Cd in soil in Taiwan. In addition, the spirit of Life Cycle Analysis (LCA) technique was also employed to identify the materials, and products should be ignored as a crucial pollution source in this study. Results and Discussion According to the MFA methodology applied in this study and on the basis of related studies performed by Taiwanese governmental authorities, we arrive at the following analysis results: (1) the total amount of Cd from the economic perspective of material and product flow was approximately 441.2 tons; (2) the wastewater directly discharged into irrigation water can be concluded to be the major pollution route of Cd in farmland soil in Taiwan; (3) material plastic stabilizer (cadmium oxide, CdO), Zn-Pd compounds and Cu compounds should be the crucial pollution sources to contaminate environment through the route of wastewater in Cd flow analysis; (4) the crucial pollution sources to contaminate environment through the route of wastewater in Cd flow analysis were five factories, Coin, Jili, Taiwan Dye, Guangzheng and Mingguan, and they were all categorized as stearate Cd industries; (5) the typical source of the Cd pollution in soil in Changhua County through the pollution route of wastewater should be the metal surfacing process industries. Conclusions This study proved that MFA can be a good tool for identifying Cd flow as well as for recognizing the crux of the problem concerning incidents of Cd pollution. This study led to the conclusion that the causal relationship between farmland pollution caused by Cd and stearate Cd factories in Taiwan seemed quite close by way of MFA methodology. In addition, this study also found that the wastewater discharged from a single metal surfacing process factory will not cause remarkable farmland pollution. However, the wastewater simultaneously discharged from a group of pollution factories can result in a significant pollution incident. Recommendations and Outlook This case study is only a small contribution to the understanding of the toxic material flow related to Cd in the environment. This study recommends that Taiwanese governmental authorities should not deal with problems on an ad hoc basis, but should instead deal with Cd pollution problems overall employing control measures. Finally, the more accurate information or data we can collect, the more reliable results we can identify. Therefore, the quality and quantity of related data used in this MFA model should be closely scrutinized in order to ensure the most correct and comprehensive investigation on the toxic material flow.     

西部开发中的泥石流问题

西部地区的青、甘、陕、川、滇、黔、新、藏、宇、桂、内蒙和重庆等12个省区市内都有泥石流分布,已查明的泥石流沟计15500余条,受泥石流危害或威胁的县级以上政府驻地城镇逾百座,一场泥石流致死百人以上的灾害点达23个,泥石流及其灾害是西部大开发中必须面临的生态环境问题之一,城市建设、公路和铁路等交通建设、水利建设,西气和西电东送工程建设等西部大开发的重点领域,,在开发建设中都将要遇到泥石流问题,吸取以往这类建设中抗御泥石流灾害的经验与教训,对于减轻泥石流灾害和保障西部大开发顺利进行具有现实意义。     

红枫湖特征污染物变化趋势分析

时红枫湖2004年至2007年的特征污染物总磷、总氮以及氨氮的变化趋势以及库容变化进行分析.结果表明,红枫湖总磷严重超标,所有监测垂线超标率为100%;总磷浓度年均值南湖高于北湖,五条监莉垂线由南向北总磷浓度呈递减趋势;从总磷的总量来看,四年间总磷总量增幅较大,2007年比2004年增加895.3吨.总氮、氨氮亦严重超标,年均浓度值超标率为100%,并且氨氮与总氮变化趋势一致.2004年～2007年红枫湖年平均库容量呈逐年上升趋势,但污染物总磷和总氮的浓度并没有降低,其总量也随着上升.