Comparison of catalytic activity of two platinised TiO2 films towards the oxidation of organic pollutants

Two types of platinised TiO2 films, i.e., Pt-TiO2/ITO and Pt(TiO2)/ITO, were prepared by a procedure of dip-coating and subsequent photo-deposition, and photo-deposition and subsequent dip-coating, respectively. They were well characterized by DRS, XRD spectra, SEM microscopy and photoelectrochemical measurement. Their photocatalytic, dark catalytic and photoelectrocatalytic activities were investigated using formic acid as a model organic pollutants. Compared with pure TiO2/ITO film, the photocatalytic activity of the platinised TiO2 films were apparently improved. However, the improvement was considerably dependent on the preparation method of these films. Pt-TiO2/ITO not only possessed higher photocatalytic activity but also showed a dark catalytic activity towards HCOOH degradation. As a sequence, it was first emphasized that the dark catalytic effect of Pt-TiO2/ITO was partly responsible for degradation of formic acid in the photocatalytic oxidation process. Although the Pt(TiO2)/ITO film does not exhibit the dark catalytic activity, its photocatalytic degradation efficiencies towards HCOOH are higher than that of Pt-TiO2/ITO film. Therefore, in view of enhanced photocatalytic activity, the Pt(TiO2)/ITO was more favored than Pt-TiO2/ITO film.     

Study on fractions of adsorbed Pb and Cd onto natural surface coatings

The speciation and extent of migration of adsorbed Pb and Cd in natural surface coatings (NSCs) were investigated using sequential extraction procedure to provide an understanding of distribution of the adsorbed Pb and Cd. Extractions were conducted on NSCs before and after Pb and Cd adsorption treatment under controlled laboratory conditions with initial Pb and Cd concentrations ranging from 0.2-2.5 mol/l. The Langmuir adsorption isotherms were applied to estimate equilibrium coefficients of Pb and Cd adsorption to NSCs components. The results showed that 58.50% of adsorbed Pb in average existed in tightly adsorbed form, and the remaining Pb was mostly present as solid oxides/hydroxides (34.00%) and exchangeable and soluble form (7.50%) in NSCs, respectively. Large amount of adsorbed Cd (70.51% in average) was present in exchangeable and soluble form, following a decreasing order in tightly adsorbed form (18.61%), solid oxides/hydroxides (9.87%), and easily oxidizable solids/compounds (1.01%), respectively. No Cd was found in strongly held oxides and precipitates. Compared to the distribution of adsorbed Pb in NSCs, Cd distribution showed that less migration of Cd from exchangeable and soluble form to solid oxides/hydroxides after adsorbed to NSCs, indicating fewer sites for Cd to adsorb to NSCs and less affinity of Cd to the NSCs. These percent distributions of metals provided an additional interpretation to that Pb adsorption to the NSCs greater than that of Cd, less retention of Cd than that of Pb and less roles attributed for Pb/Cd adsorption by organic materials in NSCs, which were observed based on the selective extraction techniques in the independent investigations.     

Influence of cadmium on antioxidant capacity and four microelement concentrations in tomato seedlings (Lycopersicon esculentum)

Tomato (Lycopersicon esculentum) seedlings were grown in four cadmium (Cd) levels of 0-10 microM in a hydroponic system to analyze the antioxidative enzymes, Cd concentration in the plants, and the interaction between Cd and four microelements. The results showed that there was a significant increase in malondialdehyde (MDA) concentration, and superoxide dismutase (SOD) and peroxidase (POD) activities in the plants subjected to 1-10 microM Cd. This indicates that Cd stress induces an oxidative stress response in tomato plants, characterized by an accumulation of MDA and increase in activities of SOD and POD. Root, stem and leaf Cd concentrations increased with its exposure Cd level, and the highest Cd concentration occurred in roots, followed by leaves and stems. A concentration- and tissue-dependent response was found in the four microelement concentrations to Cd stress in the tomato leaves, stems and roots. Regression analysis showed that there was a significantly negative correlation between Cd and Mn, implying the antagonistic effect of Cd on Mn absorption and translocation. The correlation between Cd and Zn, Cu and Fe were inconsistent among leaves, stems and roots.     

Cu and Zn adsorption onto non-residual and residual components in the natural surface coatings samples (NSCSs) in the Songhua River, China

Natural surface coatings samples (NSCSs) from the surface of river shingles were employed to investigate the roles of non-residual and residual components of the NSCSs in controlling Cu and Zn adsorption via the selective extraction techniques and statistical analysis. The results indicate that the greatest contribution to metals adsorption on a molar basis was from Mn oxides in the non-residual fraction. Metals adsorption capacities of Mn oxides exceeded those of Fe oxides by one order of magnitude, fewer roles were found attributing to adsorption by organic materials (OM), and the estimated contribution of the residual fraction to metals adsorption was insignificant. These results implied that Mn oxides were the most important component in controlling heavy metals in aquatic environments. Experiments with Cu and Zn adsorption measured together showed that Cu severely interfered with Zn adsorption to the NSCSs and vice versa under the conditions of the two coexisted ions adsorption.     

Effects of metsulfuron-methyl on the microbial population and enzyme activities in wheat rhizosphere soil

The effects of metsulfuron-methyl, a sulfonylurea herbicide, on the wheat soil microorganisms were evaluated by the methods of microbial inoculation culture, and the activities of three enzymes were measured using the colorimetric method. The tolerant microorganisms that can resist 500 microg x g(-1) metsulfuron-methyl in the counting culture medium were studied specially. Metsulfuron-methyl distinctly inhibited the common aerobic heterotriphic bacteria, but the effects on common fungi and common actinomycete were not evident. In the meantime, the number of tolerant fungi increased greatly in the rhizosphere after the application of metsulfuron-methyl in contrast to the significant decrease of the amount of tolerant actinomycete. It indicates that fungi might turn into the dominant microbial type and actinomycete is the sensitive factor in the soil polluted by sulfonylurea residues. The population of aromatic compounds-decomposing bacteria, aerobic azotobacter, and nitrite bacteria all increased in the earlier period, but the aerobic azotobacter decreased rapidly in number 30 days later, and the amount of nitrite bacteria also showed a temporary decrease with time 15 days later. However, the denitrifying bacteria just began to increase significantly after the crops had grown for 50 days. The amount of sulfur-oxidizing bacteria gradually decreased with the growth of crops, and so were the sulfate-reducing bacteria after metsulfuron-methyl application. To all types of microorganisms, there were more microbes in rhizosphere samples than those in nonrhizosphere except aerobic azotobacter. It means the growth of wheat root system can stimulate the growth of most microorganisms. The activities of hydrogen peroxidase and polyphenol oxidase in soil samples after metsulfuron-methyl application were notably lower than those in the control, and the difference of the activities between the samples of rhizosphere and nonrhizosphere was evident. On the contrary, the activity of dehydrogenase was not inhibited by the application of metsulfuron-methyl, and the rhizosphere effect was not obvious either.     

综放工作面覆岩破坏特征及裂隙演化相似模拟试验研究

针对煤层开采后常出现矿压显现剧烈、煤岩透气性增大和地表下沉等问题,利用二维相似模拟试验研究综放工作面覆岩破坏特征并通过分形理论表征裂隙演化规律.试验结果表明:煤层基本顶初次来压步距为78 m,周期来压步距为24 m;煤层采动裂隙发育,距煤层顶板超过35 m;煤层开采后形成的覆岩裂隙具有分形特征,其分形维数随工作面的推进...     

基于SWAT模型的瀼渡河生态流量计算方法

保障和管理河湖生态流量是加强水资源开发利用管控的基本要求,是实施长江大保护和高质量发展的重要内容.以瀼渡河为例,提出了针对无实测流量的河流推算生态流量的方法.首先,利用SWAT水文模型模拟得到1990—2019年30年逐月流量过程,表明该河流流量由上游至下游逐渐增大,且具有明显的汛期和非汛期特征;其次,采用蒙大拿法、最...     

Towards corporate environmental information disclosure: an empirical study in China

High levels of corporate environmental information disclosure (EID) have become pressing issues due to environmental protection around the world. Corporate EID refers to disclose their information on activities related to the natural environment, environmental protection and use of resource. Emerging economies in developing countries seem to face a formidable task for promoting corporate EID. Based on data of corporate EID for 871 listed manufacturing companies in China, this paper examines the status of corporate EID. The significant difference of selectively disclosing their environmental information for the listed companies is investigated. The relations among the level of EID, industrial sector, company size, and company ownership are also explored. Surprisingly, the result reveals the inverse relationship between the marketization level and corporate EID.     

典型区域历史遗留土壤污染问题及其综合防治研究

土壤污染是历史遗留环境问题的众多表现形式之一.土壤污染引发的土壤环境质量恶化,直接影响到人居环境安全、人体健康和社会稳定.本文通过对贵州铜仁汞矿产历史遗留问题区域土壤污染综合防治方案的分析研究,明确了土壤污染综合防治原则,并分别给出了实现污染源控制、土壤污染修复治理以及农产品安全与环境健康监管的路线图,为其它历史遗留问题区编制和实施土壤污染综合防治规划提供参考.     

炼油废水中环烷酸测定方法的改进

研究了用酸碱滴定法测定炼油废水中环烷酸含量，并与重量法进行了比较，滴定法的精度与准确度都比重量法好。