Bioaccessibility of trace elements as affected by soil parameters in smelter-contaminated agricultural soils: a statistical modeling approach

An investigation was undertaken to identify the most significant soil parameters that can be used to predict Cd, Pb, and Zn bioaccessibility in smelter-contaminated agricultural soils. A robust model was established from an extended database of soils by using: (i) a training set of 280 samples to select the main soil parameters, to define the best population to be taken into account for the model elaboration, and to construct multivariate regression models, and (ii) a test set of 110 samples to validate the ability of the regression models. Total carbonate, organic matter, sand, P(2)O(5), free Fe-Mn oxide, and pseudototal Al and trace element (TE) contents appeared as the main variables governing TE bioaccessibility. The statistical modeling approach was reasonably successful, indicating that the main soil factors influencing the bioaccessibility of TEs were taken into account and the predictions could be applicable for further risk evaluation in the studied area.     

Acetylcholinesterase activity in the terrestrial snail Xeropicta derbentina transplanted in apple orchards with different pesticide management strategies

Apple orchards are highly manipulated crops in which large amounts of pesticides are used. Some of these pesticides lack target specificity and can cause adverse effects in non-target organisms. In order to evaluate the environmental risk of these products, the use of transplanted sentinel organisms avoids side-effects from past events and facilitate comparison of multiple sites in a short time. We released specimens of the terrestrial snail Xeropicta derbentina in each 5 of two kinds of apple orchards with either conventional or organic management strategies plus in a single abandoned orchard. After one month, individuals were retrieved in order to measure acetylcholinesterase (AChE) activity. Mean values of AChE activity were significantly reduced in all conventional apple orchards compared to the others. Results show that the measurement of biomarkers such as AChE inhibition in transplated X. derbentina could be useful in the environmental risk assessment of post-authorized pesticides.     

Isolation and characterization of <Emphasis Type="Italic">Bradyrhizobium</Emphasis> sp. SR1 degrading two β-triketone herbicides

In this study, a bacterial strain able to use sulcotrione, a β-triketone herbicide, as sole source of carbon and energy was isolated from soil samples previously treated with this herbicide. Phylogenetic study based on16S rRNA gene sequence showed that the isolate has 100 % of similarity with several Bradyrhizobium and was accordingly designated as Bradyrhizobium sp. SR1. Plasmid profiling revealed the presence of a large plasmid (>50 kb) in SR1 not cured under nonselective conditions. Its transfer to Escherichia coli by electroporation failed to induce β-triketone degrading capacity, suggesting that degrading genes possibly located on this plasmid cannot be expressed in E. coli or that they are not plasmid borne. The evaluation of the SR1 ability to degrade various synthetic (mesotrione and tembotrione) and natural (leptospermone) triketones showed that this strain was also able to degrade mesotrione. Although SR1 was able to entirely dissipate both herbicides, degradation rate of sulcotrione was ten times higher than that of mesotrione, showing a greater affinity of degrading-enzyme system to sulcotrione. Degradation pathway of sulcotrione involved the formation of 2-chloro-4-mesylbenzoic acid (CMBA), previously identified in sulcotrione degradation, and of a new metabolite identified as hydroxy-sulcotrione. Mesotrione degradation pathway leads to the accumulation of 4-methylsulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4 methylsulfonylbenzoic acid (AMBA), two well-known metabolites of this herbicide. Along with the dissipation of β-triketones, one could observe the decrease in 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibition, indicating that toxicity was due to parent molecules, and not to the formed metabolites. This is the first report of the isolation of bacterial strain able to transform two β-triketones.     

A DFT study of the reactions of O3 with Hg° or Br

In the mid 1980s the study of ozone reactivity gained a significant interest with the discoveries of the stratospheric ozone hole (Farman et al., 1985) and of the ozone depletion events in the polar boundary layer (Oltmans et al., 1989). In the stratosphere, the mechanism involves heterogeneous reactions on polar stratospheric clouds that lead to chlorine activation (Solomon et al., 1986). In contrast, tropospheric ozone depletion occurring during polar springtime rather involves reactive bromine species. They are released during a series of photochemical and heterogeneous reactions often called the bromine explosion (see the review of Simpson et al., 2007). In this reaction sequence, an essential step is the generation of photolyzable Br₂, the precursor of two Br atoms, via the multiphasic reaction (1):

(1)

HOBr + Br⁻ + H⁺ → H₂O + Br₂

The production of reactive HOBr could occur with the oxidation of BrO by HO₂.     

新型TCAS吸附树脂对水中Cd2+的吸附去除研究

通过静态吸附试验,研究一种由超分子受体化合物磺化硫杂杯芳烃（TCAS）与树脂结合的产物——新型TCAS吸附树脂对重金属Cd²⁺的吸附去除性能,并初步探讨了吸附机理。试验研究结果表明,TCAS吸附树脂对Cd²⁺的饱和吸附量为14.45 mg/g。当温度为20℃,0.5 g TCAS吸附树脂对10 mL浓度为5 mg/L的Cd²⁺溶液吸附60 min时, Cd²⁺的去除率可达到99%以上。pH值是影响TCAS吸附树脂吸附效果的重要因素,在pH=5～9时,Cd²⁺的去除率随着pH值的升高而增大。在试验范围内,TCAS吸附树脂对Cd²⁺吸附符合Freundlich方程。吸附在TCAS吸附树脂上的Cd²⁺可洗脱回收,TCAS吸附树脂也可再生利用。 TCAS吸附树脂对重金属Cd²⁺的吸附机理主要归因于TCAS对Cd²⁺的络合作用。     

Polymer biodegradation: mechanisms and estimation techniques

Within the frame of the sustainable development, new materials are being conceived in order to increase their biodegradability properties. Biodegradation is considered to take place throughout three stages: biodeterioration, biofragmentation and assimilation, without neglect the participation of abiotic factors. However, most of the techniques used by researchers in this area are inadequate to provide evidence of the final stage: assimilation. In this review, we describe the different stages of biodegradation and we state several techniques used by some authors working in this domain. Validate assimilation (including mineralisation) is an important aspect to guarantee the real biodegradability of items of consumption (in particular friendly environmental new materials). The aim of this review is to emphasise the importance of measure as well as possible, the last stage of the biodegradation, in order to certify the integration of new materials into the biogeochemical cycles. Finally, we give a perspective to use the natural labelling of stable isotopes in the environment, by means of a new methodology based on the isotopic fractionation to validate assimilation by microorganisms.     

凹型建筑外立面火灾烟气蔓延特性研究

为了研究凹型建筑外立面火灾烟气蔓延特性，对高层建筑凹槽内火灾烟气“三场”数值模拟。研究表明:结构因子α（进深与槽宽之比）的变化导致凹型建筑结构内呈现不同的火灾烟气蔓延规律；当α为0~0.4时，建筑凹槽内的火灾烟气无烟囱效应；当α为0.6~1.2时，建筑凹槽内的火灾烟气呈现一定的烟囱效应，其火灾烟气温度场、CO浓度场、扩散速度场变化显著；当α>1.2的，建筑凹槽内的火灾烟气烟囱效应显著。     

世界银行贷款云南环境项目中的移民问题

工程项目带来的移民是一个破坏性非常大的复杂过程，关系着工程建设与营运的成败。世行移民政策的目标是保证受工程影响的人能从工程中受益。以滇池污染治理为主体的世行贷款云南并存项目，通过系统规划和预先编制行搬迁动计划，并通过方案比较和设计调整，使征地和受影响人数量减少到最低限度，保证了项目的顺利评估。