Heavy metals extraction from contaminated soil: recovery of the flushing solution

The optimum conditions for the recovery of copper from a contaminated soil by using the soil flushing technique are evaluated. Tests on a soil artificially contaminated with copper chloride were carried out in order to evaluate the influence of the speed of percolation and of the chelating agent concentration (aqueous solution of an ethylendiaminotetraacetic acid di-sodium salt Na2-EDTA). At pH=7.3 an efficiency up to 93.9% for copper extraction was achieved by flushing 500 ml of Na2-EDTA 0.05 M solution and 100 ml of pure water at 0.792 cm/h. At these operating conditions the formation of EDTA complexes with other competitive cations (calcium and iron) was negligible. The experimental results were in agreement with the ones obtained using a model describing the chemistry of metal extraction. This model assessed that above pH=6 the formation of calcium and iron EDTA complexes was excluded and only the chelation of copper was allowed. The recovery of 91.6% of EDTA was also achieved by evaporating and acidifying the extracted solution: after filtration, solid EDTA was obtained, through the addition of sodium hydroxide Na2-EDTA. About 99.5% of the extracted copper was finally precipitated under alkaline conditions from the liquid phase.     

Risk analysis for road and rail transport of hazardous materials: a simplified approach

A simplified approach to transportation risk analysis for road and rail transport of dangerous goods is proposed, which is based on the use of a product databank, containing the impact areas for a number of pre-selected accidental scenarios, and on the selection of a few typical average values of the involved parameters, relevant to the type of transport activity and to the route. Such an approach enables also a non-specialist to very rapidly perform a transportation risk analysis, obtaining both individual and societal risk measures for the study case(s): the results may be used to support a decision making process, and/or as a basis for a more in deep analysis.     

Organochlorine pesticides,PCBs and heavy metals in tissues of the mullet Liza aurata in lake Ganzirri and Straits of Messina (Sicily,Italy)

The aim of this research was to investigate the presence of organochlorine pesticides, PCBs and heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in fish living in lake Ganzirri and the Straits of Messina, using the mullet Liza aurata as a "biological indicator". Different tissues of Liza aurata, which include the muscle, gill and vertebral column, were taken for analyses. Quantitative determination of the organochlorine compounds was performed by GC-ECD and confirmed with GC-MS. The concentrations of "essential" and "toxic" heavy metals were determined by Atomic Absorption Spectrophotometry. For the mullets of lake Ganzirri, the study showed DDE in three samples of gills and one of muscle, at concentrations below the MRL; no appreciable residues of PCBs (Aroclor 1232 series) were found. The concentrations of Zn and Cu were much higher than those of the "toxic" metals. No traces of organochlorine pesticides and PCBs were found in the individuals from the Straits of Messina. Therefore, these results indicate that these two environments are not at toxicological risk.     

Assessing potential bioavailability of metals in sediments: A proposed approach

Due to anthropogenic inputs, elevated concentrations of metals frequently occur in aquatic sediments. In order to make defensible estimates of the potential risk of metals in sediments and/or develop sediment quality criteria for metals, it is essential to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavailability of metals in test sediments. Many factors may influence pore water concentrations of metals; however, in anaerobic sediments a key phase controlling partitioning of several cationic metals (cadmium, nickel, lead, zinc, copper) into pore water is acid volatile sulfide (AVS). In this paper, we present an overview of the technical basis for predicting bioavailability of cationic metals to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Included are discussions of the advantages and limitations of metal bioavailability predictions based on these parameters, relative both to site-specific assessments and the development of sediment quality criteria.     

Histological and biochemical bases of defense mechanisms in four species of Polybranchioidea ascoglossan molluscs

The multiple defensive strategies of four Mediterranean ascoglossan molluscan species, belonging to two different Polybranchioidea families, Cyerce cristallina (Trinchese, 1881) and Caliphylla mediterranea (Costa A., 1869) (Polybranchiidae), and Ercolania funerea (Costa A., 1867) and Placida dendritica (Alder and Hancock, 1843) (Stiligeridae), were studied. E. funerea, P. dendritica and C. mediterranea were collected from the lake Fusaro (Arco Felice, Naples) in 1992. C. cristallina was collected from Capo Miseno (Bay of Naples) in 1991. C. cristallina and E. funerea easily undergo autotomy of dorso-lateral appendages (cerata) followed by an extraordinarily quick (8 to 10 d) regeneration of the latter. Histological analyses showed the presence, at the basis of both normal and regenerated cerata of these species, of a muscular sphincter which facilitates the autotomic process. C. mediterranea and P. dendritica, which do not undergo autotomy, lack this anatomical feature but feed upon algae belonging to the Chaetomorpha and Bryopsis genera, and, as shown by electron microscopy studies, retain large quantities of chloroplasts which they use as camouflage amidst algae and to escape predation. E. funerea also exploits this behavioral defense mechanism. Histological investigations also revealed in the cerata of all four species several multi-cellular mucous glands responsible for the secretion of the slime typical for these molluscs. C. cristallina, E. funerea and P. dendritica secrete large amounts of slime, whose extracts displayed ichthyotoxic activity when assayed by the Gambusia affinis ichthyotoxicity assay, while extracts of C. mediterranea slime were not toxic. A chemical analysis of the slime, mantle and cerata led to the isolation of polypropionate - and -pyrones from all species except C. mediterranea. These secondary metabolites possess structures that differ only by the degree of methylation and the geometry of double bonds of the side chain and are specifically distributed in cerata and slime of C. cristallina and E. funerea. The pyrones also display different activities in the Hydra vulgaris regeneration assay and in the G. affinis ichthyotoxicity test and, depending on their structural features and tissue distribution, are likely to play a role either as defense allomones or as supportive inducers of cerata regeneration. In conclusion, combined biological observations and histological and chemical techniques generated valuable information on the defensive behavior of these four ascoglossan species which exploit various combinations of the same behavioral and/or chemical defensive strategies and thus successfully avoid predation.     

我国寻找超大型陆相火山岩型铀矿床的潜力评估

国外早己发现了超大型陆相火山岩型铀矿床 ,但我国迄今尚末找到。我国有广泛分布的陆相火山岩 ,能否找到此类超大型铀矿床 ,这是当前火山岩铀矿地质工作者急待解决的重要课题。本文在剖析了世界上已发现的超大型陆相火山岩型铀矿床的成矿环境和成矿条件及我国大型陆相火山岩型铀矿床成矿特点的基础上 ,对我国陆相火山岩的时空分布规律及我国主要构造火山岩带成矿潜力作了评述 ,综合得出在我国找到超大型陆相火山岩型铀矿床是有可能的 ,并确认赣杭、南岭、燕辽、大兴安岭等构造火山岩带具备形成超大型陆相火山岩型铀矿床的地质条件。上述主要构造火山岩带与其它构造火山 ( -侵入 )岩带交汇重叠部位 ,是最有希望的突破区。     

观音坪电站工程评价区景观格局预测分析

以湖北省宣恩县酉水流域观音坪水电工程生态完整性评价报告为基础,采用卫星遥感图片分析,运用GIS技术,完成土地利用结构和景观格局图。通过对工程建成前后各种土地类型的优势度值的变化分析得出:工程建设中会造成林草地减少约3.45hm2,优势度由原来的58.30%下降到57.41%,仅下降0.89%;林地和耕地也分别减少约7.20 hm2和0.84 hm2,优势度下降3.87%和1.92%;而水域增加10.82 hm2,优势度上升1.73%,但是它们之间的比例关系基本与工程建设前的比例相当,草地仍然是景观生态体系中的模地。工程建设后当地景观生态体系不会有很大变化。     

A new approach of drawing airport noise contours on computer based on Surfer

Noise contours are used to describe the extent of airport noise pollution and to plan land use around airports. The LWECP, (weighted equivalent continuous perceive noise level) recommended by ICAO( International Civil Aviation Organization) is adopted as airport noise rating parameter in this paper. With the help of various mathematical models in the software Surfer, noise contours can be drawn automatically by the completed program in Visual C Code. Corrections for thrust, velocity, atmospheric temperature, humidity and lateral ground attenuation are also considered in the new method, which can improve the efficiency of drawing contours. An example of its use for drawing noise contours of an airport in Zhejiang Province of China is proposed and the predictions and the measurements show agreements well.     

考虑贮存剖面的固体火箭发动机橡胶密封圈贮存寿命研究

目的 对贮存周期内包含多个温度环境剖面的固体火箭发动机橡胶密封圈贮存寿命进行评估。方法 通过开展硅橡胶材料加速老化试验,结合Arrhenius老化规律,建立硅橡胶老化模型,获得硅橡胶加速老化等当规律,并根据等当关系开展模拟密封装置加速老化试验,考核老化后硅橡胶密封性。最后通过对固体火箭发动机贮存环境剖面进行梳理,计算出贮存周期下的等效温度,并结合试验获得的硅橡胶密封圈老化性能,直接对该贮存周期下密封圈老化寿命进行评估。结果 通过硅橡胶材料老化试验及模拟密封装置老化试验,得到了25℃下硅橡胶能够满足20 a的使用寿命。随后通过梳理并计算得出固体火箭发动机贮存周期下的等效温度为22.78℃,可以直接获得该发动机使用的硅橡胶密封圈寿命在该贮存环境下能够满足20 a使用寿命。结论 通过计算贮存周期下多个温度环境剖面的等效温度,并结合加速老化试验结论,可快速获得橡胶密封圈老化寿命。