Experimental toxicity and bioaccumulation of cadmium in freshwater periphytic diatoms in relation with biofilm maturity

A study was undertaken to examine cadmium accumulation in freshwater biofilm, its effects on biofilm development and on diatom community structure in laboratory experimental conditions. A suspension of a biofilm originated from the Riou-Mort River (South West France) was inoculated into three experimental units containing clean glass substrates under laboratory conditions. Settling and already developed biofilms were exposed to a Cd concentration of 100 µg L^− 1. Metal accumulation (total and intracellular metal content) in biofilms, dry weight and ash-free dry mass, diatom cell density and diatom community composition were analyzed. Both total and intracellular Cd accumulated by the biofilm throughout the experiment increased with duration of metal exposure. Biofilms in the course of maturation were showed higher Cd content and less effective development than settled biofilms. However diatom communities in younger biofilms exposed to Cd increased their tolerance to Cd by a highly significant development of Nitzschia palea. In contrast, Cd exposure had different effect in installed biofilm and taxonomic composition. These results indicate that mature biofilm may limit Cd accumulation into its architecture and protect diatom communities from the effects of metals.     

Combined effect of copper, cadmium, and lead upon Cucumis sativus growth and bioaccumulation

Cucumis sativus (cucumber) was tested to assess an ecotoxicity in soils contaminated by the heavy metals copper (Cu), cadmium (Cd), and lead (Pb) separately and in combinations. The toxicity endpoint was plant growth, which was measured as shoot and root lengths after 5 day exposure. Sum of toxic unit (TU) at 50% inhibition for the mixture (EC50mix) was calculated from the dose (TU-based)-response relationships by the Trimmed Spearman-Karber method. Binary metal combinations of Cu+Cd, Cu+Pb, and Cd+Pb produced all three types of interactions; concentration additive (EC50mix=1TU), synergistic (EC50mix<1TU), and antagonistic (EC50mix>1TU) responses. Ternary combination of Cu+Cd+Pb produced an antagonistic response for the growth of Cucumis sativus. Bioaccumulations of Cu, Cd, and Pb were observed in Cucumis sativus and the bioaccumulation of one metal was influenced by the presence of other metals in metal mixtures. In general, antagonistic and/or synergistic responses reflected bioaccumulation patterns in some binary combinations, but the patterns in mixtures were not always consistent with toxicity data. This study indicated that TU approach appears to be a good model to estimate the combined effect of metals in plant systems, and mixture toxicity may be closely-related to the bioaccumulation pattern within plants. Combined effects of mixtures have to be taken into account to ecological risk assessment.     

Study on the separation and characterization of cadmium incorporated into Zea Mays L.

Methods of separation and characterization of Cd in Zea Mays L. were studied by means of a radioisotopic technique based on injecting ¹⁰⁹Cd into the plant. Two classic methods for fractionating plant material were compared. Cd was found to occur in all different cell components and a significant activity of Cd in the intracellular liquid is bound to proteins as indicated by chromatography on a molecular sieve. Cd fixed to cell walls exchanges entirely after selective solvent extraction with H₂O, KNO₃, HAc, HCl. Our results indicate Cd‐binding sites in stems.     

The dynamics of mercury and cadmium uptake into different organs of Anodonta cygnea L.

The bioaccumulation of Hg and Cd into various organs of the freshwater mussel Anodonta cygnea was investigated during an 840 h experimental period. Parallel with the metal concentrations the periodicity of activity and the body weight of the animals were also checked.The accumulation of Hg in all of the investigated organs, and that of the Cd into the kidney have two phases, up to 24 h it was non linear, between 24 and 72 h it became linear in most organs up to 840 h, and could be characterized by a regression line. For Hg accumulation the gills while for Cd accumulation the kidney and viscera were exceptions, here saturation was observed after 504 and 672 h, respectively.The speed of Hg and Cd uptake was different in various organs of Anodonta cygnea. Into the kidney the accumulation of Hg was six times faster than that of Cd. As compared to the adductor muscles the Hg and Cd uptake of the kidney was 20 and 10 times faster, respectively.The factor of concentration was in all organs except adductor muscles over 1000, in case of the kidney the rate of bioconcentration for Hg reached nearly 100,000.The dry weight of organs dropped during the metal uptake by 20–60%, but no mortality was observed up to 840 h.In the presence of Hg and Cd the filtering activity of the mussels became reduced as a result of increase of inactive rest periods. Nevertheless, the decrease of activity did not prevent the linear uptake of metals into the animal     

蓝之上——COOP HIMMELB(L)AU建筑展

1968年,由Wolf D.Prix和Helmut Swiczinskv在维也纳创立了COOP HlMMELB(L)AU建筑师事务所.多年以来,他们一直活跃在建筑、城市规划、设计和艺术的领域,是视觉及实验建筑的先驱.在去年10月竣工开放的宝马世界(BMW WELT),更以大胆新颖的造型吸引了世人的目光.     

The significance of cadmium in hair. The influence of a recommended washing procedure on the cadmium content of hair of rats experimentally exposed to cadmium

The impact of a "mild" preanalytical washing procedure on an elevated Cd-content in hair was studied in newly grown hair of rats exposed to a large amount of Cd in their drinking water. A large part of the Cd in hair was removed by this procedure. Agitation by way of ultrasound seems to be no more effective than agitation by mechanical shaking. The effectiveness of washing varied in accordance with the type and duration of exposure.     

中海蓝湾设计

本文简单介绍了中海蓝湾项目的建筑设计特点,并通过该项目的设计实践探索住宅人性化设计的设计方向     

Flowering stage characteristics of cadmium hyperaccumulator Solanum nigrum L. and their significance to phytoremediation

The Cd accumulation and biomass characteristics of a newly found Cd-hyperaccumulator Solanum nigrum L. were investigated at the flowering stage and the mature stage. The results showed that the concentration of Cd in the stems and leaves of S. nigrum harvested at the flowering stage was up to 83.1% and 85.5% of that at the mature stage, and the dry-weight sum of the stems and leaves of S. nigrum harvested at the flowering stage was 93.4% of that at its seed maturity. The Cd-removing ratio by the shoots of S. nigrum harvested at the flowering stage was 87.5% of that at the mature stage. It was also found by observing the growth duration of S. nigrum that the frostless period at the experimental site was at least twice as long as the growth duration from the seedling-transplanted phase to the flowering stage of the hyperaccumulator. Therefore, S. nigrum could be transplanted into contaminated soils twice in one year by harvesting the hyperaccumulator at its flowering stage based on climatic conditions of the site and traits of the plant growth. In particular, the extraction efficiency of Cd by harvesting the shoots of S. nigrum at its flowering stage twice in one year could increase 75.0% compared to that of at its single maturity. Thus, the method of multiple harvesting would be very important to increase phytoremediation efficiency in practice.     

Cadmium bioaccumulation factors for terrestrial species: application of the mechanistic bioaccumulation model OMEGA to explain field data

In environmental risk assessment of metals it is often assumed that the biota-to-soil accumulation factor (BSAF) is generic and constant. However, previous studies have shown that cadmium bioaccumulation factors of earthworms and small mammals are inversely related to total soil concentrations. Here, we provide an overview of cadmium accumulation in terrestrial species belonging to different trophic levels, including plants, snails and moles. Internal metal concentrations of these species are less than linearly related to total soil levels, which is in accordance with previously observed trends. The mechanistic bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) is used to provide a quantitative explanation of these trends in cadmium accumulation. Our results indicate that the model accurately predicts cadmium accumulation in earthworms, voles and shrews when accounting for geochemical availability of metals and saturable uptake kinetics.     

The chemistry of cadmium in natural water—I a study of cadmium complex formation using the cadmium specific-ion electrode

The extent of formation of labile complexes of cadmium has been investigated in synthetic solutions and in real samples. A substantial proportion of the total cadmium in river and lake water will usually be present as the free cadmium ion, and this proportion will be larger the lower the pH value and the lower the proportion of sewage effluent present in the water. Humic substances usually account for most of the complexation, followed in importance by carbonate, the complex of which with cadmium has not been reported previously.     

Removal of cadmium and manganese by a non-toxic strain of the freshwater cyanobacterium Gloeothece magna.

The ability of both living and dry cells of Gloeothece magna, a non-toxic freshwater cyanobacterium, to adsorb cadmium and manganese is demonstrated in this study. Chlorophyll a content of living cells was not influenced by either cadmium or manganese concentrations, indicating that adsorption of both Cd²⁺ and Mn²⁺ by living cells of G. magna, was independent of the metabolic state of the organism. Moreover, the adsorption of both Cd²⁺ and Mn²⁺ to living cells and dry cells, was dependent on the metal concentrations, and fitted the Freundlich adsorption isotherm. However, dry cells had larger binding capacity for both Cd²⁺ (K_f=912.6) and Mn²⁺ (K_f=2398) than living cells (K_f=151.4 & 63, respectively). The role of the capsular polysaccharides, the main constituents of the cyanobacterial envelope, in binding these two metals was also studied. Polysaccharide extracts of this organism adsorbed high amounts of both Cd²⁺ (115–425 μg mg⁻¹) and Mn²⁺ (473–906 μg mg⁻¹). This study suggests that G. magna would probably be cultured in water bodies contaminated by heavy metals to ameliorate their toxicity. Also dry material of this cyanobacterium being a non-toxic species, could be used as a safe biofilter to remove toxic metals from drinking water.     

从浅蓝走向深蓝 国有大型建筑设计企业海外市场开拓之简析

文章从中国大型国有建筑设计企业"走出去"的必要性出发,分析了开拓海外市场的可行性及存在的不足,探讨了开拓海外市场的策略,包括提出目标市场的选择标准、信息渠道的建设以及积极主动开拓市场的一些建议,并对开拓海外市场进行了概要性的风险分析。     

蓝色伊斯坦布尔——东方与西方之间的明珠

如果说土耳其是伸入到欧洲的一个马头,伊斯坦布尔就是这个马头上的眼睛。她矗立在欧洲与亚洲的分界线上,像一个动情的少女,用深情的目光,一只眼看着亚洲,一只眼看着欧洲,在亚欧大陆之间静静地汲取     

The leaching of cadmium from plastic toys

A systematic examination has been made of the factors that influence the leaching of cadmium from solid ABS (acrylonitrile-butadiene-polystyrene) plastic toys containing cadmium sulphide or selenide pigments, and realistic test procedures have been developed that give reproducible results. It has been shown that in the absence of light less than 100 ppm of cadmium is extracted from the pigmented plastic used for toys on sale in the United Kingdom.     

化学沉淀法去除水中镉的特性研究

考察了氢氧化物沉淀法和硫化物沉淀法对镉的去除效果。结果表明,两种方法均能将0.025mg/L的镉降低到《生活饮用水卫生标准》限值(0.005mg/L)以内,除镉效果稳定。氢氧化物沉淀法中,三氯化铁作为混凝剂对镉的去除效果明显优于聚合氯化铝,能有效去除0.250mg/L的镉,且处理后铁残余浓度未超标;硫化钠沉淀法除镉效果好,但硫化钠投加量增加到0.20mg/L时,上清液硫化物会超标。