沙打旺与柳枝稷单、混播种苗期水分利用和根冠生长的比较

在室内生长箱内盆栽沙打旺和柳枝稷的苗期生长阶段进行高土壤水分 (黄绵土土壤田间持水量FC的 80 % )和低土壤水分 (5 0 ?)处理 ,比较二者单、混播种植下水分利用与根冠生长差异 ,以探讨黄土高原半干旱丘陵区牧草植物的合理种植方式 .结果表明 :在水分利用方面 ,低水处理下混播使沙打旺和柳枝稷叶片瞬时水分利用效率均较单播提高 ,低水处理后混播群体水分利用效率也显著比单播柳枝稷增大 .在根冠生长方面 ,混播促进了柳枝稷地上部分植株高度生长 ,并使地下部分分配比重增大 ,根系绝对长度缩短 ;混播后沙打旺的植株高度降低 ,根系绝对长度增加 ,但干物质分配比重减小 .低水处理后 ,沙打旺和柳枝稷混播下的根冠生长趋向于资源的充分合理利用 ,表现在混播群体的根系生长有利于充分利用土壤深层水和表层来水 ,混播后地上部分高度的生长特征变化利于对光的利用 .因此 ,在水分和养分条件相对较差坡地占较大比例的半干旱黄土丘陵地区 ,采用沙打旺和柳枝稷混播种植相比各自单播利于促进苗期生长与提高土壤水分利用率 .图 2表 2参 10     

Distribution of Poly(β-propiolactone) Aerobic Degrading Microorganisms in Different Environments

The distribution of degading microorganisms of high molecular weight poly(-propiolactone) (PPL), whose individual structural units are similar to those of poly(-hydroxybutyrate) (PHB) and poly(€-caprolactone) (PCL), was examined. Despite the fact that PPL is a chemosynthetic polymer, many kinds of PPL-degrading microorganisms were found to be distributed as resident populations widely in natural environments. A total of 77 strains of PPL-degrading microorganisms was isolated. From standard physiological and biochemical tests, at least 41 strains were referred to as Bacillus species. Microbial degradation of fibrous PPL proceeded rapidly in some enrichment cultures but was not as complete as that of PHB. Most of the isolated PPL-degrading microorganisms were determined to be PCL degraders and/or PHB degraders. Therefore, it can be assumed that mostly PPL is recognized by the microorganisms as PHB or another natural substrate of the same type as which PCL is regarded. Microbial degradation of PPL was confirmed by some Bacillus strains from type culture collections. The similarity of microbial degradation between PPL and PCL was found to be very close.     

ECONOMIC AND WATER QUALITY EFFECTS OF VARIABLE AND UNIFORM APPLICATION OF NITROGEN1

ABSTRACT: Nitrogen (N) fertilizer rates for achieving optimum crop yields often vary within a field due to spatial variability in soil moisture and nitrogen content and other crop growth factors. When there is substantial within-field variability in these factors, uniform application of N (UAN) may not be economically efficient in terms of maximizing net return because N is likely to be over-applied in some areas and under-applied in other areas of the field. In addition, over-application can adversely affect water quality. A sample of fields in a Midwestern agricultural watershed is used to test for statistically significant differences in N application rates, crop yields, surface and ground water quality and net returns between UAN and variable application of N (VAN) for four cropping systems. Profitability and water quality benefits of VAN are sensitive to the distribution of soil types within a field. Water quality effects and profitability of UAN and VAN vary with cropping systems. VAN is not uniformly superior to UAN in terms of increasing net returns and improving water quality for the farming systems and watershed evaluated in this study.     

Particle emissions of a railway line determined by detailed single particle analysis

The goal of this study was to identify and quantify particles emitted from railway traffic. For that purpose PM10 samples were collected near a busy railway line using a wind direction and speed controlled sampling equipment consisting of five devices. Measurements taken perpendicular to the railway lines at 10, 36 and 120 m distance enable an identification and separation of particles caused by the railway traffic from background particles. Morphology and chemistry of more than 11,000 particles were analysed by computer controlled scanning electron microscopy (CCSEM). Based on chemical composition five particle classes are defined and assigned to their sources. The mass of the individual particles is determined by multiplying their volumes, calculated based on their morphology with a density assigned specifically to each particle class. The density of the particle classes is derived from their chemical composition. To estimate the PM10 contributions of the railway lines, the mass of PM10 at 120 m (background, not influenced by the railway lines) is subtracted from the mass of PM10 at 10 m. The emissions of the railway lines are dominated by ‘iron’ particles, which contribute 2.9 μg m⁻³ or 67% to the railway related PM10. In addition, ‘aluminium’ and ‘calcium’ particles contribute also to the railway related PM10 (1.0 μg m⁻³ or 23% for the ‘aluminium’ and 0.4 μg m⁻³ or 10% for the ‘calcium’ particles). These particles are assigned to abrasion of the gravel bed and re-suspension of mineral dust.Long-term gravimetric results of the contribution of iron to the mass of railway related PM10 from a study performed earlier at the same site are in good agreement with the data presented in this study.     

H2O2 formation from photocatalytic processes at the ZnO/water interface

The paper focuses on the production of H2O2 by photocatalysis over ZnO in an aerated aqueous phase. The presence of different reductants that increase the H2O2 production in the aqueous phase is analysed; particular attention is paid to nitrite, which has been shown to be the reductant that produces the most significant increments in the H2O2 production. The photocatalytic anodic decomposition of ZnO in the presence of the different reductants is also investigated. From the results obtained, the relevance of the ZnO photocatalysis in the formation of environmental hydrogen peroxide is estimated.     

水解酸化-缺氧法处理采油废水的污染物迁移降解试验研究

水解酸化．缺氧法对采油废水有较好的处理效果，采用GC／MS技术对水解酸化-缺氧法处理采油废水过程中污染物的迁移降解进行的研究表明：水解酸化段和缺氧段对采油废水中碳原子为C6-C9、分子量为100—140的有机物均有较好的降解能力。其中，在水解酸化段中酮类、芳烃得到较好的降解，缺氧段中酚类和醚类化合物降解明显。水解酸化-缺氧工艺对于采油废水中的甲苯和二甲苯具有较好的降解能力。     

取代芳烃对呆鲦鱼急性毒性的QSAR研究

应用密度泛函方法(DFT)在B3LYP/6-311G**水平上全优化计算25个取代芳烃的量子化学参数,结合疏水性参数与化合物对呆鲦鱼的急性毒性进行定量构效关系研究(QSAR)。经逐步回归筛选变量后,所建多元线性回归方程的相关系数R及去一法交互检验复相关系数R2cv分别为0.967和0.907。用预测集样本进行了外部预测,所得外部预测样本复相关系数R2ext和外部预测集交互检验Q2ext分别为0.881和0.836。模型结果显示:分子疏水性参数logP较大时具有较大的脂溶性,化合物的毒性较大;取代基的吸电子能力越强,苯环的正电性越大,化合物的毒性越大。