Visualisation of natural aquatic colloids and particles -- a comparison of conventional high vacuum and environmental scanning electron microscopy

The applicability of environmental scanning electron microscopy (ESEM; imaging of hydrated samples) and conventional high vacuum scanning electron microscopy (SEM; imaging of dried samples at high vacuum) for the observation of natural aquatic colloids and particles was explored and compared. Specific attention was given to the advantages and limitations of these two techniques when used to assess the sizes and morphologies of complex and heterogeneous environmental systems. The observation of specimens using SEM involved drying and coating, whereas ESEM permitted their examination in hydrated form without prior sample preparation or conductive coating. The two techniques provided significantly different micrographs of the same sample. SEM provided sharper images, lower resolution limits (10 nm or lower), but more densely packed particles, suggesting aggregation, and different morphological features than ESEM, suggesting artefacts due to drying. ESEM produced less easily visualised materials, more complex interpretation, slightly higher resolution limits (30-50 nm), but these limitations were more than compensated for by the fact that ESEM samples retained, at least to some extent, their morphological integrity. The results in this paper show that SEM and ESEM should be regarded as complementary techniques for the study of aquatic colloids and particles and that ESEM should be more widely applied to aquatic environmental systems than hitherto.     

噪声、空气污染、传染病、缺氧等的健康损害防治对策

根据室外噪声污染和空气污染状况及危害,以新理念创新了空气净化杀菌与隔音降噪交融技术——人体舒适空间。它由卧室、办公室等通过一些隔音吸音材料及配套设施改造而成,通过多重隔音构建宁静空间,应用双向层叠全方位空气净化与高效消声一体化系统及智能换气、主动杀菌等措施,能同时降低噪声、空气污染、传染病、缺氧等对健康的损害,还能带来环保、经济和社会效益。     

Photocatalysis of fluorene adsorbed onto TiO2

The adsorption of fluorene onto TiO2 has been investigated by conducting equilibrium and kinetic experiments. Adsorption isotherms have been evaluated at two different pHs in the range of temperatures 296-325 K. The type III isotherm shapes obtained were modelled by considering several expressions taken from the literature. Temperature exerted a positive influence in fluorene uptake. Addition of phosphates involved a negative effect when computing the final equilibrium fluorene removal. The kinetic experiments carried out at 296 K corroborated the competitiveness of phosphates to occupy the active sites on the titania surface. Nevertheless, equilibrium conditions are faster achieved at pH 2 than at pH 5. The photocatalysis of fluorene at different initial concentrations of the parent compound revealed a slight improvement of the process at pH 5 if compared to the results obtained at pH 2. A Langmuir-Hinselwood representation of the data confirms the previous statement. Catalyst load shows an optimum, concentration values of the photocatalyst above the optimum provoke a decrease in the fluorene abatement rate. Reutilisation of the catalyst indicates that fluorene is completely eliminated from the solid, i.e. it is suggested that fluorene and intermediates are surface oxidised.     

Assessment of a process to degrade metal working fluids using Pseudomonas stutzeri CECT 930 and indigenous microbial consortia

The development of a novel biological process to treat metal working fluids (MWFs)-containing effluents at bioreactor scale was pursued in this work. The bacteria Pseudomonas stutzeri CECT 930 was investigated for the first time as an alternative agent for MWF degradation. An adequate medium design and mixing and aeration system, as well as an appropriate microorganism proved to be crucial for reaching high levels of degradation by P. stutzeri and by an indigenous consortium (about 70% and 50% of reduction in total petroleum hydrocarbon content in less than 2 wk, respectively). Additionally, as there is no information in literature trying to kinetically characterize an MWF-polluted effluent degradation process, all the experimental data were fitted to logistic and Luedeking and Piret models, that allowed to elucidate the growth-associated character of the biodegradation process.     

Effect of clays, metal oxides, and organic matter on rhamnolipid biosurfactant sorption by soil

Rhamnolipids produced by Pseudomonas aeruginosa have been proposed as soil washing agents for enhanced removal of metal and organic contaminants from soil. A potential limitation for the application of rhamnolipids is sorption by soil matrix components. The objective of this study is to empirically determine the contribution of representative soil constituents (clays, metal oxides, and organic matter) to sorption of the rhamnolipid form most efficient at metal complexation (monorhamnolipid). Sorption studies show that monorhamnolipid (R1) sorption is concentration dependent. At low R1 concentrations that are relevant for enhancing organic contaminant biodegradation, R1 sorption followed the order: hematite (Fe(2)O(3))>kaolinite>MnO(2) approximately illite approximately Ca-montmorillonite>gibbsite (Al(OH)(3))>humic acid-coated silica. At high R1 concentrations, relevant for use in complexation/removal of metals or organics, R1 sorption followed the order: illite>humic acid-coated silica>Ca-montmorillonite>hematite>MnO(2)>gibbsite approximately kaolinite. These results allowed prediction of R1 sorption by a series of six soils. Finally, a comparison of R1 and R2 (dirhamnolipid) shows that the R1 form sorbs more strongly alone than when in a mixture of both the R1 and R2 forms. The information presented can be used to estimate, on an individual soil basis, the extent of rhamnolipid sorption. This is important for determining: (1) whether rhamnolipid addition is a feasible remediation option and (2) the amount of rhamnolipid required to efficiently remove the contaminant.     

Role of salicylic acid in alleviating oxidative damage in rice roots (Oryza sativa) subjected to cadmium stress

Time-dependent changes in enzymatic and non-enzymatic antioxidants, and lipid peroxidation were investigated in roots of rice (Oryza sativa) grown hydroponically with Cd, with or without pretreatment of salicylic acid (SA). Exposure to 50 microM Cd significantly decreased root growth, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), but increased the concentrations of H(2)O(2), malondialdehyde (MDA), ascorbic acid (AsA), glutathione (GSH) and non-protein thiols (NPT). However, pretreatment with 10 microM SA enhanced the activities of antioxidant enzymes and the concentrations of non-enzymatic antioxidants, but lowered the concentrations of H(2)O(2) and MDA in the Cd-stressed rice compared with the Cd treatment alone. Pretreatment with SA alleviated the Cd-induced inhibition of root growth. The results showed that pretreatment with SA enhanced the antioxidant defense activities in Cd-stressed rice, thus alleviating Cd-induced oxidative damage and enhancing Cd tolerance. The possible mechanism of SA-induced H(2)O(2) signaling in mediating Cd tolerance was discussed.     

淮河中游北岸地区“四水”转化研究

针对近期强人类活动对区域水循环的影响,以淮河中游北岸典型区为研究对象,利用分布式水文模型研究该地区的"四水"(大气水、地表水、土壤水和地下水)转化定量关系。结果表明,研究区水循环受人类活动影响剧烈,产生了明显的自然-社会二元性特征,对"四水"间的相互转化产生重要影响;2003—2010年研究区地表水、土壤水和地下水存在正向补给趋势,增加了当地水资源可利用量;研究时段内研究区需要来自区域外的水汽补给来支持年均39.77×108m3的降水量。最后在定量分析的基础上给出了当地水资源管理与合理利用的若干建议。区域"四水"转化关系研究可为当地的水资源评价、规划和管理提供基础性的技术支持。     

基于Sentinel-2卫星数据的中山市植被叶面积指数反演及空间分析

以广东省中山市为例,基于SNAP软件和2景Sentinel-2卫星数据,反演并分析中山市全域及特定区域内植被叶面积指数。结果表明,反演结果与中山市生态空间格局和植被保护状况相一致,且与其他研究报道中对水库库区林地采用现场实测方法获得的数据高度一致,表明该方法反演城镇植被叶面积指数具有良好的适用性和准确性。     

Evolution of self-organized division of labor in a response threshold model

Division of labor in social insects is determinant to their ecological success. Recent models emphasize that division of labor is an emergent property of the interactions among nestmates obeying to simple behavioral rules. However, the role of evolution in shaping these rules has been largely neglected. Here, we investigate a model that integrates the perspectives of self-organization and evolution. Our point of departure is the response threshold model, where we allow thresholds to evolve. We ask whether the thresholds will evolve to a state where division of labor emerges in a form that fits the needs of the colony. We find that division of labor can indeed evolve through the evolutionary branching of thresholds, leading to workers that differ in their tendency to take on a given task. However, the conditions under which division of labor evolves depend on the strength of selection on the two fitness components considered: amount of work performed and on worker distribution over tasks. When selection is strongest on the amount of work performed, division of labor evolves if switching tasks is costly. When selection is strongest on worker distribution, division of labor is less likely to evolve. Furthermore, we show that a biased distribution (like 3:1) of workers over tasks is not easily achievable by a threshold mechanism, even under strong selection. Contrary to expectation, multiple matings of colony foundresses impede the evolution of specialization. Overall, our model sheds light on the importance of considering the interaction between specific mechanisms and ecological requirements to better understand the evolutionary scenarios that lead to division of labor in complex systems. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00265-012-1343-2) contains supplementary material, which is available to authorized users.     

Formate species in the low-temperature oxidation of dimethyl ether

The oxidation of dimethyl ether (DME, 340 ppm in 10% O2) has been studied experimentally in an atmospheric pressure laminar flow reactor in the temperature range from 240 degrees C to 700 degrees C for residence times in the range 2-4 s. The influence of nitric oxide additions up to 620 ppm to the feed gases has also been investigated. Products of reaction were determined by FTIR. In the absence of NO, reaction is first detected at about 260 degrees C. The products in the low-temperature region include formaldehyde (HCHO), and formic acid (HCOOH). The addition of NO leads to the appearance of methyl formate (CH3OCHO). While the overall behaviour of the system can be explained qualitatively in terms of typical low-temperature hydrocarbon ignition, recently published chemical kinetic models for DME ignition do not allow for the formation of these formate species. We find no experimental evidence for the formation of hydroperoxymethyl formate (HPMF, HOOCH2OCHO) which is predicted by the models to be a significant stable intermediate at temperatures below 350 degrees C. Since both formic acid and methyl formate have potentially harmful health effects, these observations may have significant implications for use of DME as a diesel fuel.