Seed dispersal of desert annuals

We quantified seed dispersal in a guild of Sonoran Desert winter desert annuals at a protected natural field site in Tucson, Arizona, USA. Seed production was suppressed under shrub canopies, in the open areas between shrubs, or both by applying an herbicide prior to seed set in large, randomly assigned removal plots (10-30 m diameter). Seedlings were censused along transects crossing the reproductive suppression borders shortly after germination. Dispersal kernels were estimated for Pectocarya recurvata and Schismus barbatus from the change in seedling densities with distance from these borders via inverse modeling. Estimated dispersal distances were short, with most seeds traveling less than a meter. The adhesive seeds of P. recurvata went farther than the small S. barbatus seeds, which have no obvious dispersal adaptation. Seeds dispersed farther downslope than upslope and farther when dispersing into open areas than when dispersing into shrubs. Dispersal distances were short relative to the pattern of spatial heterogeneity created by the shrub and open space mosaic. This suggests that dispersal could contribute to local population buildup, possibly facilitating species coexistence. Overall, these results support the hypothesis that escape in time via delayed germination is likely to be more important for desert annuals than escape in space.     

温度、pH值及盐度对龙须眼子菜吸附镉、铅的影响

以龙须眼子菜(Potamogeton pectinatus)干样为材料,研究了不同温度、pH值和盐度对龙须眼子菜吸附镉、铅离子的影响.结果表明,不同温度及不同pH值下龙须眼子菜对镉吸附符合Langmuir模型,对铅的吸附符合Freundlich模型.与5 ℃、10 ℃、30 ℃处理相比,20 ℃时龙须眼子菜对镉、铅的吸附能力较强.当其它条件不变时,在pH值为3～7的范围内,龙须眼子菜对镉的吸附随pH值升高而增加,对铅的吸附随pH值升高而减少.在0.5～10 g·L-1的盐度范围内,随着溶液盐度的增加龙须眼子菜对镉吸附减少,但对铅的吸附却增加.龙须眼子菜是一种对镉、铅有很强的吸附能力的沉水植物,对温度、酸碱度、盐度适应范围也很广,因而可作为生物吸附剂用于含镉、含铅废水的处理.     

沼液的综合利用

沼液是厌氧发酵的残留物，由于其富含营养物质及微量元素，可提高动植物的抗病能力，故已在农业、畜牧业、养殖业等方面得到广泛应用。阐述了沼液的基本性质，并就其作为饲料掺拌剂、肥料、浸种剂、农药等的应用现状做了综述。     

降雨诱发公路滑坡灾害危险性评价动态权重系统

本文通过深入分析影响降雨诱发公路滑坡灾害危险性的因素,构建了考虑不同降雨强度的动态评价指标体系,并用改进的层次分析法测算各分项指标的权重,最终以童家湾滑坡为例对动态权重系统应用于危险性评价的效果进行了检验。研究结果显示,随降雨工况的变化,表征各因素对评价系统影响程度的权重系统呈动态非线性变化趋势,由此导致滑坡危险性相对...     

华北山区大气气溶胶浓度及其尺度谱分布的研究

1980年3月,我们在北京北部山区,用光学粒子计数器观测了“干净”地区近地层大气气溶胶浓度与尺度谱分布。发现“有霾”大气气溶胶的浓度及其尺度谱分布的变化特征具有特殊性。计算表明,三参数谱模式的拟合效果较好。     

Effect of scale on flame speeds of methane-air

Explosions are the main types of accidents causing casualties in underground coal mines. Research on the mechanisms of gas explosions is needed as a basis for the development of techniques and strategies for explosion prevention, suppression, and mitigation. The prevention of loss in explosion accidents and inquiries into their causes require understanding of the explosion process of methane in air. Because of the high cost and safety issues in full scale experiments, the experiments with small scale ducts have become a key alternative approach. Whether the experimental results at small scales agree with those at full scales needs to be investigated to validate the significance of the experimental results at small scale. Numerical simulation was used to obtain the explosion characteristics of a methane-air mixture in a gallery or duct. If the grid size is too fine in the numerical simulation for a methane-air explosion it is difficult to calculate using the present computer resource. If the grid size is too coarse, the considerable error may result. The effect of grid size on results of calculation depends on the scenario being investigated. The effect of grid sizes on simulation accuracy was analyzed in this work. The overpressure and temperature distributions and the flame propagation for the deflagration of methane-air mixtures in a gallery or duct were obtained by the AutoReaGas code at three different scales. The geometry of investigated objects and the grids in the calculation domain were similar in the three cases. The calculated overpressures vary with the scale. The calculated temperatures do not vary with the scale for the three cases.     

光催化剂TiO_2改性技术的研究进展

根据近年来TiO2 光催化技术的研究成果 ,对如何提高TiO2 光催化活性的途径作了综述。     

广东省海水养殖对海区环境影响的夏季调查

在2000年夏季对广东省汕头、惠阳、珠海、阳江和湛江等沿海地区一些养殖区域与非养殖区域水体中氮、磷和浮游动植物等指标进行测定,分析夏季海水养殖给海区水环境造成的压力.结果表明,养殖区总氮、颗粒态总氮、总磷、颗粒态总磷含量分别为0.506～1.244μmol/L、0.367～1.066μmol/L、0.¨2～0.232μmol/L、0.054～0.157μmol/L,这些指标在养殖区高于非养殖区;养殖区与非养殖区的溶解态总氮、溶解态总磷、总氮总磷比值、溶解态总氮溶解态总磷比值无显著性差异.5个地点养殖区与非养殖区的浮游植物主要是角毛藻属Chaetoceros中的种类占优势;而浮游动物中占优势的主要是桡足类,包括成体与无节幼体.水产养殖对养殖海区浮游动植物的种类数目总个体数均无显著影响,但影响了生物多样性,并对某些浮游生物种类有促进作用或抑制作用.     

固定化混合菌处理高盐含油废水

对固定化微生物的除油性能进行研究,结果表明:以甘蔗渣和海绵为载体的固定化微生物的除油效果比游离状态的微生物除油效果好。甘蔗渣的最佳投加量为20 g/L(干重),最佳固定化条件为:固定化时间为36 h、pH为6、温度为40℃,在最佳固定化条件下菌种接入废水24 h后,除油率达62%;海绵的最佳投加量为5 g/L(干重),最佳固定化条件为:固定化时间48 h、pH为7、温度为35℃,在最佳固定化条件下菌种接入废水24 h后,除油率达75.8%;以甘蔗渣为载体的固定化微生物在处理时间为108 h时,除油率达最高为84.5%,以海绵为载体的固定化微生物在处理时间为96h时,除油率达82.4%。