控制排水条件下土壤氮素的运移

为研究暗管控制排水与非控制排水条件下, 不同排水出口控制高度对土壤中氮素分布和迁移的影响, 在湖北省荆州市四湖工程管理局丫角排灌试验站进行了野外试验。试验结果表明, 无论采取控制排水与否, 土壤垂直剖面上硝态氮浓度均有一致的变化规律： 20 cm处浓度最高, 在40~60 cm浓度急剧减小, 60~80 cm浓度值很小（1 mg/kg左右）; 控制排水对土壤硝态氮的减小率有显著影响, 表现在控制水位越高, 土层间硝态氮减小率最大; 控制排水能降低表层土壤硝态氮的迁移; 铵态氮与硝态氮迥然不同, 无论采取控制排水与否, 铵态氮在土壤垂直剖面上的含量变化不大; 控制排水对铵态氮的含量也有一定的影响, 表现在控制排水位越低, 土壤中铵态氮的含量越小.     

Organic–Inorganic Hybrid Coatings for the Modification of Barrier Properties of Poly(lactic acid) Films for Food Packaging Applications

Organic–inorganic hybrid coatings based on poly(ε-caprolactone), poly(ethylene oxide) or poly(lactic acid) as organic phase and silica from tetraethoxysilane as inorganic phase were prepared by the sol–gel approach. Coatings were applied onto poly(lactic acid) films for food packaging in order to improve its barrier properties towards oxygen and water vapour. All the prepared coatings were dense, homogeneous layers characterized by a good adhesion to the substrate. The permeance of the coating layers resulted one order of magnitude lower than that of the uncoated poly(lactic acid) (PLA) film. The hydrophilic character of the coating did not permit to gain a significant decrease in the water vapour permeance. The perfect visual transparency of the coatings allows their application without worsening of the esthetical properties of the substrate PLA film.     

Method for the determination of selected organochlorine pesticides and polychlorinated biphenyls in human serum based on a gel permeation chromatographic clean-up

A gel permeation chromatographic (GPC) clean-up based method was developed for determination of selected organochlorine pesticides and polychlorinated biphenyls in human serum. The method permits automation of the sample extract clean-up stage and is designed to work with small amounts of sample. Different working variables were studied in its development, including injection volume, flow rate, and fat amount as the most representative coextract. The method provides solvent and time savings. Initial extraction was performed using 96-well solid-phase disk extraction plates, and quantification was performed by gas chromatography with electron capture detection and mass spectrometry. Recoveries of PCB congeners 28, 52, 101, 118, 138, 153, and 180 and organochlorine pesticides HCB, β-HCH, γ-HCH, heptachlor epoxide, p,p′-DDE, and p,p′-DDT at two spiking levels ranged from 55% to 115% with relative standard deviations ranging from 2.0% to 14.6%. Limits of quantification ranged from 0.06 to 0.16 ng mL⁻¹ for PCBs and from 0.12 to 0.36 ng mL⁻¹ for organochlorine pesticides. Finally, the method was applied to the analysis of 38 serum samples and the results were compared with those of another procedure validated at the laboratory.     

Validation of a QuEChERS-based gas chromatographic method for analysis of pesticide residues in Cassia angustifolia (senna)

A simple multi-residue method based on modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach was established for the determination of 17 organochlorine (OC), 15 organophosphorous (OP) and 7 synthetic pyrethroid (SP) pesticides in an economically important medicinal plant of India, Senna (Cassia angustifolia), by gas chromatography coupled to electron capture and flame thermionic detectors (GC/ECD/FTD) and confirmation of residues was done on gas chromatograph coupled with mass spectrometry (GC-MS). The developed method was validated by testing the following parameters: linearity, limit of detection (LOD), limit of quantification (LOQ), matrix effect, accuracy–precision and measurement uncertainty; the validation study clearly demonstrated the suitability of the method for its intended application. All pesticides showed good linearity in the range 0.01–1.0 μg mL^?1 for OCs and OPs and 0.05–2.5 μg mL^?1 for SPs with correlation coefficients higher than 0.98. The method gave good recoveries for most of the pesticides (70–120%) with intra-day and inter-day precision < 20% in most of the cases. The limits of detection varied from 0.003 to 0.03 mg kg^?1, and the LOQs were determined as 0.01-0.049 mg kg^?1. The expanded uncertainties were <30%, which was distinctively less than a maximum default value of ±50%. The proposed method was successfully applied to determine pesticide residues in 12 commercial market samples obtained from different locations in India.     

交错齿槛型泥石流排导槽研究初探

排导槽是一种常见的泥石流防治措施,提出了交错齿槛槽定义,即该类槽是指由两束流侧墙及置于其间交错排列的梯级齿槛群构成的一种新型泥石流排导槽,根据流域面积与沟床纵比降可分为3种类型;详细分析了交错槽的结构特征,并根据泥石流的不同阶段阐述了泥石流在交错槽中的流态形式;最后从消能机制、冲刷磨蚀、生态效益等方面将交错槽与东川槽等常规阶梯深潭系统做了比较,指出交错齿槛槽具有明显的优势,为进一步研究泥石流与交错齿槛的作用机制、泥石流在其中的排导特征等打下基础。     

SAPS处理酸性矿山废水的模拟应用研究

根据硫酸盐还原菌(SRB)的生物矿化原理设计了一套连续碱度产生系统(SAPS)反应器,以市政污水处理厂的活性污泥为SRB提供源,南方常见的香芋柄为有机物碳源,选用石灰石为反应器中碱度层填充物,进行实验室模拟SAPS处理酸性矿山废水(AMD)的应用研究,实验结果表明,SAPS处理酸性矿山废水的方法是具有技术可行的:SRB利用有机碳源生长代谢,产生碱度、还原SO2-4和降解COD。最终废水p H从进水4.0左右上升到出水7.0左右;出水COD降低到约200 mg/L;SO2-4还原为各种硫化物,其还原率约为61%;不同金属离子在有机层和碱度层发生反应产生沉淀,其中Fe2+、Cu2+和Zn2+的去除效率分别约为76%、78.5%和82%,而主要靠物理吸附作用的Mn2+去除率较低;初次模拟SAPS运行到56 d时,系统最终因有机碳源不足而各项指标不再改变。     

烧结法赤泥的强度演化规律

筑坝堆存是现在处理赤泥的主要方式,为了堆场安全继续向上堆载,对烧结法赤泥强度的演变规律进行了研究。通过对比不同深度处赤泥的抗剪强度,表明赤泥强度的形成与堆载时间没有必然的联系;再通过对新进场的赤泥进行强度追踪,得到赤泥强度形成过程中抗剪强度与滤水固结时间的关系曲线,从时间因素上为赤泥的安全堆载提供一个理论依据。     

Characterization of an urban landfill soil by using physicochemical analysis and solid phase microextraction (SPME)—GC/MS

We have aimed at characterizing top soil samples taken in-situ from five different locations of the unregulated dumping site in Eskişehir/Turkey for a period of six months. The study is the first attempt in the city and in Turkey, regarding particularly the SPME (Solid Phase Microextraction Technique) analysis method utilized. A comprehensive research has been conducted to produce critical soil data to be used for indicating current risks as well as the urgency of rehabilitating the site and establishing a sanitary landfill in the site. Conventional physicochemical analytical methods and SPME technique were used to analyze the samples. Physicochemical analyses were performed for determining the pH, total dried matter, volatile matter, total nitrogen, phosphorus, macro elements and heavy metals. Meteorological data were also recorded for the same period. SPSS.10.0 statistical program was used to determine the correlation between meteorological data and physicochemical analysis results. Mean values were used in the correlation analyses. These data indicated that the air temperature and precipitation have significant effects on soil characteristics. SPME, coupled with GC/MS, was used to identify eighty six volatile and semi-volatile organic compounds contained in soil samples. The samples were extracted by headspace SPME with heating (δHS-SPME). SPME analyses were conducted using a commercially available polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber having a film thickness of 65 μm (Supelco) as a capture medium. The experimentally optimized headspace sampling conditions were arranged (15 min. at 50^˚C) before a 30 min. sampling period.     

Deriving ozone dose-response of photosynthesis in adult forest trees from branch-level cuvette gas exchange assessment

Branch-level gas exchange provided the basis for assessing ozone flux in order to derive the dose-response relationship between cumulative O3 uptake (COU) and carbon gain in the upper sun crown of adult Fagus sylvatica. Fluxes of ozone, CO2 and water vapour were monitored simultaneously by climatized branch cuvettes. The cuvettes allowed branch exposure to an ambient or twice-ambient O3 regime, while tree crowns were exposed to the same O3 regimes (twice-ambient generated by a free-air canopy O3 exposure system). COU levels higher than 20mmolm(-2) led to a pronounced decline in carbon gain under elevated O3. The limiting COU range is consistent with findings on neighbouring branches exposed to twice-ambient O3 through free-air fumigation. The cuvette approach allows to estimate O3 flux at peripheral crown positions, where boundary layers are low, yielding a meso-scale within-crown resolution of photosynthetic foliage sensitivity under whole-tree free-air O3 fumigation.