Double-Arranged Mound-Mounted Shelterbelts: Influence of Porosity on Wind Reduction between the Shelters

Using a two-dimensional LDA-System, measurements in an atmospheric boundary layer wind tunnel have been made in the intermediate field of double-arranged, mound-mounted shelterbelts. The porosity of the shelterbelts ranged from 0% to 52%. For each porosity, seven different distances of the two windbreaks between 5 and 25 times the windbreak height were investigated. The efficiency of the windbreak systems is assessed by means of protection parameters considering the change of horizontal momentum on bodies immersed in the flow, of pedestrian comfort conditions and of momentum exchange in vertical direction. Furthermore recirculation zones and the change of kinetic energy are shown. The measurement results are given in the form of contour plots indicating flow quantities and protection volumes between the two windbreaks. The shelter efficiency of the investigated windbreak systems is compared to that of adequate single line windbreaks. It is shown that for certain windbreak configurations the wind-protected area in the intermediate field of consecutively arranged windbreaks becomes larger in comparison to a single windbreak.     

Sorption of lambda-cyhalothrin,cypermethrin, deltamethrin and fenvalerate to quartz,corundum, kaolinite and montmorillonite

Sorption to mineral surfaces may be important for retention and degradation of hydrophobic pesticides in subsoils and aquifers poor in organic matter. In this work the title pyrethroids have been used to investigate selective interactions with the surfaces of four minerals. Sorption of the four pyrethroids was quantified in batch experiments with initial pyrethroid concentrations of 1–100 μg/l. Sorption to centrifuge tubes used in the batch experiments accounted for 25–60% of total sorption. Net sorption was obtained from total sorption after subtracting the amounts of pyrethroids sorbed to centrifuge tubes used. All isotherms could be fitted by the Freundlich equation with n ranging between 0.9 and 1.1. Bonding affinities per unit surface area decreased in the order: corundum>quartz>montmorillonitekaolinite. A similar sequence as found for the total surface tension of the minerals. All minerals showed the same selectivity order with respect to sorption affinity of the four pyrethroids: lambda-cyhalothrin>deltamethrin>cypermethrin>fenvalerate, which shows that the most hydrophobic compound is sorbed most strongly. Stereochemical properties of the four pyrethroid formulations may also contribute to the selectivity pattern.     

Platinum emission rate of automobiles with catalytic converters

Inconsistent data presently available on the platinum emission rate of cars in Germany equipped with catalytic converters are evaluated. Automobile sources of Pt other than autocatalysts are quantified and found to be 1–6 orders of magnitudes lower than the Pt emissions attributed to catalytic converters. A transfer of emission rates derived from test stand experiments to more realistic street conditions reaches 0.8 μg Pt/km. In this manner, data from test stand experiments and from environmental investigations meet in the range of 0.5–0.8 μg Pt/km.     

TCE recovery mechanisms using micellar and alcohol solutions: phase diagrams and sand column experiments

Forty-one phase diagrams and fifteen sand column experiments were conducted to evaluate the efficiency of three types of washing solutions to recover trichloroethylene (TCE) at residual saturation and to identify the recovery mechanisms involved. This study demonstrates that: (1) an alcohol and a surfactant combination is more efficient than an alcohol used alone in water; (2) the prediction of the dominant recovery mechanism from the tie line slopes in phase diagram is accurate and can be reproduced in sand column experiments; and (3) TCE recovery efficiency in sand column experiments is generally well represented by the position of the miscibility curve in phase diagrams in the low concentration range. However, the miscibility curve alone is not sufficient to exactly predict the TCE recovery mechanisms involved. Tie line slopes and the critical tie line have to be taken into consideration to select the active matter as well as its concentration and to predict the dominant recovery mechanism in sand column experiments. The sand column experiments quantified the recovery efficiency of each solution and identified the proportion of the recovery mechanisms (mobilisation vs. solubilisation). Washing solutions with an active matter concentration above the critical tie line caused dominating mobilisation. Mobilisation was also dominant when the active matter of the washing solution partitioned into the organic phase and the active matter concentration was below the critical tie line. Solubilisation and emulsification were dominant for washing solutions containing active matter, which principally partitioned into the aqueous phase and an active matter concentration below the critical tie line.     

大气中有机汞样品的吸附采集及其解吸方法研究

用1:1的BOSP和DEGS色谱填料作为混合吸附剂,研究了大气中有机汞样品的吸附采集及其解吸方法,选择了最佳实验条件。     

Magnitude of pesticidal contamination in winter vegetables from Hisar,Haryana

Monitoring of 80 winter vegetable samples during 1997–1998 for pesticidal contamination was carried out on GC-ECD and GC-NPD systems with capillary columns following multiresidueanalytical technique. The tested samples were found 100%contaminated with low but measurable amounts of pesticideresidues. Among the four major chemical groups, residue levels oforganophosphorous insecticides were highest followed bycarbamates, synthetic pyrethroids and organochlorines. About 32%of the samples showed contamination with organophosphorous andcarbamate insecticides above their respective MRL values. On thebasis of observations made in these studies, it is suggested thatmore extensive monitoring studies covering all vegetable cropsfrom different agro-climatic regions of the state be carried outto know exact level of pesticidal contamination, which may serveas basis for future policy on chemical use.     

还原－衍生化高分辨气相色谱法测定复杂样品中痕量硝基多环芳烃（NO_2－PAH）的研究

研究了还原－七氟丁酸酐衍生化高分辨气相色谱－ＥＣＤ测定痕量硝基多环芳烃的方法，该法具有选择性好，灵敏度高的特点，适合于复杂样品痕量硝基多环芳烃的测定。建议采用以氨基多环芳烃ＨＦＢＡ衍生物为参比的ＨＦＢＡＰＡＨ保留指数体系，利用保留指数进行双柱定性成功地在碳黑样品提取物中检出包括１－ＮＯ＿２芘在内的９种ＮＯ＿２－ＰＡＨ并提出了定量结果。     

用毛细管色谱法和同位素技术研究呋喃丹及其有毒代谢物在棉籽和土壤中的残留

使用OV-101玻璃毛细管柱气相色谱法测定棉籽和土壤中的呋哺丹和3-羟基呋喃丹,减少了农药在柱上的吸附和分解,分开了农药与植物中的干扰物质,减少了样本的前处理步骤,其回收率分别约为80％,变异系数小于20％。以~(14)C标记呋喃丹测定各前处理步骤的损失率,表明农药的损失主要是由于酸解及固体物质的吸附。两年三地田间试验的结果说明,按照推荐药量在棉田使用呋喃丹,棉田和土壤中的残留均低于检测限。     

上浮式高速冲模设计

介绍了一种上浮式高速冲裁模的设计方法 ,适用于薄板冲裁 ,其在卸料方式、定位方法上有一定的特点