Comparison of masking agents for antimony speciation analysis using hydride generation atomic fluorescence spectrometry

A sensitive atomic spectrometric method for the redox speciation analysis of Sb in water is described. The proposed method is based on the selective generation of stibine from Sb(III) in a continuous flow system using non-dispersive atomic fluorescence spectrometry for detection. The effects of the HCl concentration on the fluorescence intensities of Sb(III) and Sb(V) were investigated. The results indicated that atomic fluorescence emission due to Sb(V) can constructively interfere with the determination of Sb(III). For the determination of Sb(III), four compounds were tested as masking agents to inhibit the generation of stibine from Sb(V). The effects of the concentrations of the masking agents and of HCl on the fluorescence signals from Sb(III) and Sb(V) were studied. The results indicated that citric acid and NaF can successfully suppress hydride generation from Sb(V). To evaluate the developed methodology and the influence of the matrix, the recovery of Sb(III) from natural water that was spiked with different Sb(III) and Sb(V) concentrations was tested.     

Comparative effects of five chelating agents on testicular toxicity in mice induced by acute exposure to cadmium

The aim of this study was to develop new antidotes for cadmium (Cd) since this metal is known to produce mammalian toxicity. N-p-hydroxymethylbenzyl-D-glucamine dithiocarbamate (HBGD), N-benzyl-D-glucamine dithiocarbamate (BGD), diethyldithiocarbamate (DDTC), 2,3-dimercaptopropanol (BAL), and ethylenediamine-tetraacetic acid (EDTA) were studied for their ability to inhibit the adverse effects induced by Cd on mouse testes. The parameters examined included concentrations of Cd, calcium (Ca), iron (Fe), and zinc (Zn) in testes, lipid peroxidation (LPO) levels in testes, lactate dehydrogenase (LDH) activity in serum and reproductive ability of male mice. Mice injected intraperitoneally (ip) with CdCl₂ (2.5?mgCd?kg^?1) after 30?min or 24?h, were then injected ip with chelating agents (400?µmol?kg^?1). Cd increased the concentrations of testicular Ca, Cd, Fe, Zn, and LPO levels as well as the activity of LDH in serum. HBGD and BGD effectively prevented the increase in above indices, and improved the reproductive ability weakened by exposure to Cd. The results suggested that HBGD and BGD are more effective detoxificants in the case of testicular toxicity in mice induced by acute exposure to Cd.     

Chelant-assisted pulse flushing of a field Pb-contaminated soil

Laboratory experiments on a lead-contaminated soil were carried out to test the effects of chelant addition on metal leachability using column tests. Tests were aimed at studying metal mobilisation upon application of two different chelating agents (ethylenediaminetetraacetic acid [EDTA] and ethylenediaminedisuccinic acid [EDDS]). Column operation was arranged to simulate a flushing treatment in which the chelating agent is applied in a pulse mode to the soil for one bed volume, while deionised water was continuously introduced for the rest of the experiment. Two different concentrations (3 and 5 mmol·kg ^?1 respectively) of the two chelating agents and a control solution (deionised water) were tested in separate experiments; pH, total organic carbon and the total concentrations of Pb, Zn, Fe, Cd, Cu and Ni were monitored during each run. A seven-step sequential extraction procedure was used to evaluate metal partitioning and concentration in the contaminated soil after treatment as a function of depth. The results showed the effect of the nature of flushing solution on the hydraulic behaviour of the columns. Metal concentrations in the leachate increased considerably upon the application of chelants, thus indicating their suitability for metal extraction from contaminated soils. In view of full-scale application of soil flushing, particular concern should also be devoted to ensuring a homogeneous distribution of the solution within the contaminated area and an efficient collection of the exhausted extracting solution, as well as to recovering and recycling the chelating agent used.     

Mobilization kinetics of heavy metals from contaminated river sediment of northern Taiwan by complexing agents

A laboratory experiment was used to investigate the mobilization kinetics of heavy metals from the sediment of a contaminated river located in northern Taiwan with varied concentrations of NTA and EDTA. We found that there were two stages of desorption in the mobilization of heavy metals from the sediment. As the concentrations of NTA and EDTA ranged 0–3.9 x 10^‐4M (0–100mg/l) and 0–2.7 x 10^‐4M (0–100mg/l) respectively, the mobilization percentages of heavy metals were proportional to the logarithm values of the concentrations of NTA and EDTA. The physical meaning of the multiple first‐order reaction was significant for the actual condition, but occasionally, it had more errors for Cu and Zn in the initial phase. The two‐constant model was most appropriate for describing the rates of mobilization of Pb, Cu, Zn, and Cr. The agreement between the diffusion model and the experimental data was satisfactory for Pb, Cu, Zn, and Cr only in the initial 5 h.     

模糊控制理论在湿法脱硫真空皮带脱水机滤布纠偏控制中应用

随着国家节能减排工作的不断深入,燃煤电站脱硫装置的投运容量已占全国燃煤机组的一半左右。靖远第二发电公司4×300MW机组脱硫装置自投运以来多次出现真空皮带脱水机滤布跑偏的现象,造成真空皮带过滤机停车及滤布撕裂等严重后果,影响脱硫装置的正常投运。介绍了通过引进先进的模糊控制理论应用于滤布纠偏控制,并对控制硬件进行相应的改造,成功地解决了靖远第二发电公司湿法脱硫真空皮带脱水机滤布纠偏控制中出现的问题。为燃煤电站湿法脱硫真空皮带脱水机滤布及其他行业相似工艺过程的纠偏控制提供参考。     

Characterisation of the abiotic degradation pathways of oxytetracyclines in soil interstitial water using LC-MS-MS

The fate of oxytetracyclines (OTCs) in soil interstitial water was investigated and the structure of a number of degradation products elucidated in a time-related experiment. A previously developed separation method for LC–MS–MS able to base separate and quantify OTC and three of its epimers and degradation products was applied. Compounds detected were 4-epi-oxytetracycline (EOTC) (t_R=3.0 min), OTC (t_R=4.4 min), -apo-oxytetracycline (-apo-OTC) (t_R=11.4 min) and β-apo-oxytetracycline (β-apo-OTC) (t_R=18.4 min). Furthermore, we tentatively identified 4-epi-N-desmethyl-oxytetracycline (E-N-DM-OTC) (t_R=3.0 min), N-desmethyl-oxytetracycline (N-DM-OTC) (t_R=3.5), N-didesmethyl-oxytetracycline (N-DDM-OTC), 4-epi-N-didesmethyl-oxytetracycline (E-N-DDM-OTC) (t_R=3.7 and 4.7 min) and 2-acetyl-2-decarboxamido-oxytetracycline (t_R=8.7) in all samples. Most compounds were only present in trace concentrations (less than 2%) relative to the parent OTC. EOTC was on the other hand formed up to a ratio of 0.6 relative to parent OTC concentration. Only EOTC, E-N-DM-OTC, N-DM-OTC, N-DDM-OTC and E-N-DDM-OTC were formed during the time-related experiment. All other compounds were probably only present as impurities in the spiked OTC formulation as they declined in concentration from the start of the experiment. Half-lives (T_1/2, days) of the OTCs in soil interstitial water were in the order of 2 days (EOTC) to 270 days (β-apo-OTC).     

Air pollutant emission potentials of cotton textile manufacturing industry

Cotton textile manufacturing operations cause air pollution. Air pollutants are generated by fossil fuel fired combustors due to their flues and/or a variety of chemicals in use for production. Excessive use of chemicals can be stopped or minimized by replacing them or by optimizing the production processes. Energy and water conservation are important goals in textile workplaces as well. There is substantial research and development to minimize pollution potentials of textile operations. In this paper air polluting potentials of cotton textile manufacturing operations are discussed and some quantitative examples are given for evaluating the risks to the environment. Studied impacts to environment cover direct discharges into the ambient air as well as the workplace atmosphere. Further studies are recommended for minimizing the impacts to the local and global air quality due to cotton textile production facilities.     

哈龙替代产品的开发及其应用

介绍了哈龙替代产品的灭火机理、优点、缺点以及适用场所.重点分析了细水雾灭火剂的应用范围和发展前景,为开发新型清洁高效的哈龙替代技术提供一定的参考.     

Ecological Information System: Analyzing the Communication and Utilization of Scientific Information in Mexico

/ This study is concerned with the role that communication can play in facilitating the utilization of ecological information by different sectors of society involved in environmental decision-making. The ecological information system is used as a conceptual framework. This system is a model for the analysis of interactions between three sectors involved in the management of natural resources: researchers in ecology, change agents, and rural producers. Two case studies of organizations carrying out scientific research aimed at finding and implementing sustainable strategies of resource management were carried out. The purpose was to examine how real situations function in terms of communication strategies and to analyze such situations in relation to the model proposed. The analysis revealed the importance of promoting the feedback of information from change agents and rural producers to the research sector and the incorporation of this information into the research process. It also emphasized the relevance of having "active utilizer constituencies" within the rural producers who make demands upon the entire system in order to satisfy information needs. The creation of linkage systems facilitating the connection between the generation and utilization of information was supported. In particular, the establishment of special teams within research institutions is proposed, which could promote the links between the sectors through the use of communication as an instrument of work.     

不同运行条件下厌氧微网反应器运行特性研究

采用涤纶网加工的微网膜组件与厌氧反应器结合构成厌氧微网生物反应器用于处理城市生活污水,考察了反应器在停留时间4 h、8 h和16 h、膜通量72 L/m2.h和36 L/m2.h、微网目数250目和380目条件下的运行特性。试验结果表明,反应器的停留时间与进水COD的去除率成线性关系,停留时间越长,COD去除率越高,但对TN的去除影响不大;膜通量的减小有利于出水水质的变好;提高微网目数有利于提高微网动态膜的截留性能。