微囊藻毒素微生物降解途径与分子机制研究进展

随着大量含氮和磷的废水流入湖泊和江河,导致淡水蓝藻水华污染现象日趋严重.蓝藻水华污染的最主要危害是产生和释放以微囊藻毒素(microcystins,MCs)为主的多种藻毒素.由于MCs对动植物具有很强的毒性,且其在水体中很难被传统的处理方法有效去除,因此如何有效控制蓝藻水华污染和去除MCs是摆在中外环境科学领域的一个难题.针对MCs的结构与毒性、降解菌株、酶催化降解、降解基因和生物降解途径与分子机制的研究进展进行了综述,并对今后微生物降解MCs的研究方向进行了展望,以期为解决我国日益严峻的湖库水体MCs污染和饮用水安全问题提供参考.     

Decontamination of alachlor herbicide wastewater by a continuous dosing mode ultrasound/Fe2+/H2O2 process

We used a ultrasound/Fe2+/H2O2 process in continuous dosing mode to degrade the alachlor.Experimental results indicated that lower pH levels enhanced the degradation and mineralization of alachlor. The maximum alachlor degradation(initial alachlor concentration of 50 mg/L) was as high as 100% at pH 3 with ultrasound of 100 Watts, 20 mg/L of Fe2+, 2 mg/min of H2O2 and 20℃ within60 min reaction combined with 46.8% total organic carbon removal. Higher reaction temperatures inhibited the degradation of alachlor. Adequate dosages of Fe2+and H2O2 in ultrasound/Fe2+/H2O2process not only enhance the degradation efficiency of alachlor but also save the operational cost than the sole ultrasound or Fenton process. A continuous dosing mode ultrasound/Fe2+/H2O2 process was proven as an effective method to degrade the alachlor.     

Land Use Change and Land Degradation in Southeastern Mediterranean Spain

The magnitude of the environmental and social consequences of soil erosion and land degradation in semiarid areas of the Mediterranean region has long been recognized and studied. This paper investigates the interrelationship between land use/cover (LULC) changes and land degradation using remotely sensed and ancillary data for southeastern Spain. The area of study, the Xaló River catchment situated in the north of the Alicante Province, has been subjected to a number of LULC changes during the second half of the 20th century such as agricultural abandonment, forest fires, and tourist development. Aerial photographs dating back to 1956 were used for the delineation of historic LULC types; Landsat ETM+ data were used for the analysis and mapping of current conditions. Two important indicators of land degradation, namely, susceptibility to surface runoff and soil erosion, were estimated for the two dates using easily parametrizable models. The comparison of 1956 to 2000 conditions shows an overall “recuperating” trend over the catchment and increased susceptibility to soil erosion only in 3% of the catchment area. The results also identify potential degradation hot-spots where mitigation measures should be taken to prevent further degradation. The readily implemented methodology, based on modest data requirements demonstrated by this study, is a useful tool for catchment to regional scale land use change and land degradation studies and strategic planning for environmental management.     

茚虫威在土壤中的消解动态研究

茚虫威是一种广谱高效的氨基甲酸酯类杀虫剂,低毒低残留。采用气相色谱法对茚虫威在土壤中的残留进行分析,采用田间试验方法研究了茚虫威在土壤中的消解动态。结果表明,茚虫威在土壤中消解较快,其残留消解动态曲线符合化学反应一级动力学方程,在土壤中的半衰期为7.6天。说明茚虫威使用后在环境(土壤)中可以较快地消解,从而可以较好地保障生产安全。     

新农药硫肟醚在土壤中降解的影响因子研究

在实验室条件下对新农药硫肟醚(O(3苯氧苄基)2甲硫基1(4氯苯基)丙基酮肟醚)在土壤中降解的影响因子进行了研究.结果表明,在20 d的培养时间内,随着土壤含水量的增加,硫肟醚的降解速率加快.当土壤含水量增加到80%(质量分数)时,其降解率达到最大(46.73%),然后随土壤含水量增加反而下降.随着土壤温度的升高,硫肟醚在土壤中的降解速率增加.30 ℃时降解速率达到最大(47.83%),以后温度继续升高,其降解速率呈现出下降趋势.在5～100 mg/kg的质量比范围内硫肟醚在土壤中的降解速率随其质量比的增加而提高;但当质量比继续增加时,硫肟醚的降解速率表现出下降趋势.硫肟醚在土壤中的降解遵循一级动力学方程,其在非灭菌与灭菌土壤中的降解速率常数k分别为8.106×10-3和1.63×10-3;半衰期分别为85.5 d和425.2 d.微生物对硫肟醚在土壤中的降解具有显著的影响.     

水解酸化-好氧法处理油田废水机理研究

采用水解酸化-好氧法对经物化预处理的油田废水进行试验研究.当进水COD为190～220 mg·L^-1时,水解酸化段和好氧段停留时间均为10h的条件下,出水COD为65～75 mg·L^-1,达到GB3550-83第一级Ⅰ类标准.运用GC/MS技术分析油田废水有机污染物在工艺流程中相对组分变化的规律,揭示了水解酸化-好氧法处理油田废水过程中的污染物迁移和降解规律.并运用PCR-DGGE技术,考察不同生物反应器内微生物种群及其分布特征,初步确定水解酸化和好氧反应器内的优势菌种.     

Identification of a reactive degradation zone at a landfill leachate plume fringe using high resolution sampling and incubation techniques

Vertical small-scale variation in phenoxy acid herbicide degradation across a landfill leachate plume fringe was studied using laboratory degradation experiments. Sediment cores (subdivided into 5 cm segments) were collected in the aquifer and the sediment and porewater were used for microcosm experiments (50 experiments) and for determination of solid organic carbon, solid-water partitioning coefficients, specific phenoxy acid degraders and porewater chemistry. Results from a multi-level sampler installed next to the cores provided information on the plume position and oxygen concentration in the groundwater. Oxygen concentration was controlled individually in each microcosm to mimic the conditions at their corresponding depths. A highly increased degradation potential existed at the narrow plume fringe (37.7 to 38.6 masl), governed by the presence of phenoxy acids and oxygen. This resulted in the proliferation of a microbial population of specific phenoxy acid degraders, which further enhanced the degradation potential for phenoxy acids at the fringe. The results illustrate the importance of fringe degradation processes in contaminant plumes. Furthermore, they highlight the relevance of using high-resolution sampling techniques as well as controlled microcosm experiments in the assessment of the natural attenuation capacity of contaminant plumes in groundwater.     

Photocatalytic Treatment of RDX Wastewater with Nano-Sized Titanium Dioxide (5 pp)

Background, Aim and Scope The polynitramines, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), are important military explosives and regulated toxic hazardous compounds. Production, testing and use of the compounds has resulted in numerous acres of contaminated soils and groundwater near many munitions facilities. Economical and efficient methods for treatment of wastewater and cleanup of soils or groundwater containing RDX and HMX are needed. This study focuses on the photocatalytic treatment of RDX wastewater with nano-sized titanium dioxide (nano-TiO2) under simulated sunlight, whose intensity and wavelength are similar to that of the real sunlight in Xi'an at noon. The objective is to determine the potential for RDX destruction with nano-TiO2 in aqueous solution. Materials and Methods: An activated carbon fiber (ACF) cloth-loaded with nano-TiO2 was put into the RDX containing solution, and the concentration of RDX was measured (by HPLC–UV) at regular time intervals under simulated sunlight. Results: The RDX degradation percentage of the photocatalytic process is higher than that of Fenton oxidation before 80 min, equivalent after 80 min, and it reaches 95% or above after 120 min. The nano-TiO2 catalyst can be used repeatedly. Discussion: The photocatalytic degradation kinetics of RDX under simulated sunlight can be described by a first-order reaction kinetics equation. The possible degradation mechanism of RDX was presented and the degradation performance was compared with that of biological method. Conclusions: It was demonstrated that the degradation of RDX wastewater is very effective with nano-TiO2 as the photocatalytic catalyst under simulated sunlight. The efficiency of the nano-TiO2 catalyst for RDX degradation under simulated sunlight is nearly identical to that of Fenton oxidation. Recommendations and Perspectives: To date, a number of catalysts show poor absorption and utilization of sunlight, and still need ultraviolet light irradiation during wastewater degradation. The nano-TiO2 used in the described experiments features very good degradation of RDX under simulated sunlight, and the manufacturing costs are rather low (around 10 Euro/m2). Moreover, the degradation efficiency is higher compared to that of the biological method. This method exhibits great potential for practical applications owing to its easiness and low cost. If it can be applied extensively, the efficiency of wastewater treatment will be enhanced greatly.     

Impact of Carbon Storage Through Restoration of Drylands on the Global Carbon Cycle

   Using estimates of land suitable for restoration in woodlands, grasslands, and deserts, as well as estimates of the rate at which restoration can proceed, we estimate that carbon storage in these biomes can range up to 0.8 billion tons of carbon per year (Gt C/yr), for a combination of land management strategies. This corresponds to a reduction in atmospheric buildup of 0.5 Gt C/yr, which represents up to 15% of the average annual atmospheric carbon buildup in the next century, 3.5 Gt C/yr, assuming the IPCC 92d scenario. A global strategy for reducing atmospheric carbon dioxide concentration will require the implementation of multiple options. The advantage of carbon storage in restored drylands is that it comes as a side benefit to programs that are also justifiable in terms of land management.     

Pollution-induced successions in forests of the Kola Peninsula

Trends of changes in the successional status of northern taiga forests exposed to technogenic pollution in the Kola Peninsula are discussed. Main studies of digression in spruce and pine forests are characterized on the basis of the dynamics of species composition of phytocenoses and chemical composition of atmospheric fallout, soils, and dominant plants.