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171.
调查发现广州市屋顶自然生长的维管植物有49科109属128种,植物种类较多的科为菊科、禾本科、桑科、景天科、茜草科和鸭跖草科;屋顶自然生长的植物种类数量与环境受污染程度成反比,而与周围植物的多少成正比;屋顶自然生长的植物由于长期适应屋顶的极端环境,形成了的一些独特的生态生物学特征。基于上述结果配置相应的植物组合,设计适于屋顶绿化的生态系统箱、配制相应土壤并进行技术集成,观测其生长和隔热效应。同时进行空白对照、黑网荫蓬对照、生态隔热层对照、普通土壤种植区对比试验,发现生态隔热层和生态系统箱具有成本低、易维持、隔热好、景观美的效果。 相似文献
172.
A Numerical and Field Investigation of Surface Heat Fluxes from Small Wind-Sheltered Waterbodies in Semi-Arid Western Australia 总被引:1,自引:0,他引:1
Shelterbelts are used for a variety of purposes in agricultural environments, primarily because of their ability to improve the downwind microclimate. Excessive evaporative losses from small, agricultural water supply reservoirs in semi-arid Western Australia motivated a combined numerical modelling and field investigation into the potential for using shelterbelts to reduce evaporation from these open waterbodies. A numerical model of the disturbed momentum and turbulence fields in the region modified by the wind-shelter was employed and accounted for the presence of a waterbody downwind. The model was coupled with conservation equations for heat and moisture and sensible and latent heat fluxes were estimated from the simulated momentum, temperature and humidity fields. The numerical simulations were tested against four days of field data from two experiments conducted in the agricultural districts of southwest Western Australia that measured boundary-layer evolution over a variety of small waterbodies protected by artifical and natural wind-shelters. The model provided good predictions of windspeed during neutral conditions, but inadequate specification of the upwind boundary during non-neutral stabilities resulted in the model failing to capture any sensitivity to atmospheric stability as seen in the field data. Despite this limitation, the temperature and humidity fields were adequately captured by the model, and evaporative mass flux predictions also agreed well with estimates taken from water-balance measurements. It is concluded that well-designed wind-shelters can reduce evaporation from open waterbodies by 20–30% as a result of reductions in the velocity scales responsible for removing moisture from the water surface. The model can be used to estimate the values of various shelterbelt design parameters (e.g., porosity, height) that could be applied in the field to provide optimum evaporation reductions. 相似文献
173.
马尾松纯林及其与阔叶树混交林的凋落量与养分通量 总被引:7,自引:0,他引:7
在25a生马尾松林下分别套种1a生火力楠、闽粤栲、苦槠、格氏栲、青栲和拉氏栲等阔叶树种的幼苗,16a后形成郁闭的针阔混交异龄林.通过定位监测和化学分析,对上述6种混交林类型及林下未套种阔叶树的马尾松纯林的森林凋落量及养分通量进行了研究.统计结果显示,6个混交群落的年凋落量分别为7137.3kghm-2、6741.1kghm-2、8041.7kghm-2、7151.3kghm-2、7533.2kghm-2和6149.1kghm-2,而马尾松纯林的年凋落量仅3442.8kghm-2.在所有林分的凋落物组成中,枯叶占绝对优势,占凋落物总量的49.7%~71.5%,其余依次为枯枝(5.7%~26.1%)、其它组分(5.5%~17.1%)、树皮(7.7%~18.9%)和果实(0.7%~2.0%).各混交林分中来自马尾松的凋落物占50.4%~58.0%,而来自阔叶树的凋落物占42.0%~49.6%,且两者的组成存在明显差异.各林分总凋落量的季节动态呈双峰型,第1次峰值出现在2~4月份,第2次峰值出现在8、9月份.凋落物中主要养分元素的含量依林分类型、凋落物组分和凋落时间不同而异,N、P、K、Ca和Mg的含量范围依次为3.25~12.98gkg-1、0.23~0.97gkg-1、0.42~4.02gkg-1、7.34~32.57gkg-1和1.34~5.58gkg-1.不同的林分类型,凋落物中各养分元素的年通量大小均为:Ca>N>Mg>K>P.马尾松纯林中,通过凋落物的5种养分元素的年流通量为142.01kghm-2;而在林下分别套种上述6种阔叶树后,其养分年流通量依次增加到204.95kghm-2、223.93kghm-2、304.12kghm-2、288.46kghm-2、213.77kghm-2、238.05kghm-2.图3表4参13 相似文献
174.
175.
M. A. Arthur G. B. Coltharp D. L. Brown 《Journal of the American Water Resources Association》1998,34(3):481-495
ABSTRACT: Forest land managers are concerned about the effects of logging on soil erosion, streamflow, and water quality and are promoting the use of Best Management Practices (BMPs) to control impacts. To compare the effects of BMP implementation on streamwater quality, two of three small watersheds in Kentucky were harvested in 1983 and 1984, one with BMPs, the other without BMPs. There was no effect of clearcutting on stream temperatures. Streamflow increased by 17.8 cm (123 percent) on the BMP watershed during the first 17 months after cutting and by 20.6 cm (138 percent) on the Non-BMP watershed. Water yields remained significantly elevated compared to the uncut watershed 8 years after harvesting. Suspended sediment flux was 14 and 30 times higher on the BMP and Non-BMP Watersheds, respectively, than on the uncut watershed during treatment, and 4 and 6.5 times higher in the 17 months after treatment was complete. Clearcutting resulted in increased concentrations of nitrate, and other nutrients compared to the uncut watershed, and concentrations were highest on the non-BMP watershed. Recovery of biotic control over nutrient losses occurred within three years of clearcutting. The streamside buffer strip was effective in reducing the impact of clearcutting on water yield and sediment flux. 相似文献
176.
177.
178.
A pilot scale anoxic/oxic membrane bioreactor (A/O MBR) for woolen mill dyeing wastewater treatment 总被引:5,自引:0,他引:5
A pilot-scale( 10 m^3/d) anoxic/oxic membrane bioreactor( A/O MBR) was tested for dyeing wastewater treatment of woolen mill without wasting sludge in 125 days operation. Results showed that the effluent quality was excellent, i.e. effluent COD less than 25 mg/L,BOD5 under 5 mg/L, turbidity lower than 0.65 NTU, and colour less than 30 DT, and met with the reuse water standard of China. The removal rates of COD, BOD5, colour, and turbidity were 92.4%, 98.4%, 74% and 98.9%, respectively. Constant-flux operation mode was carried out in this study, and backwash was effective for reducing membrane fouling and maintaining constant flux. Membrane fouling had heavy impact on energy consumption. More attention should be paid on pipe selection and design for the sidestream MBR system, too. 相似文献
179.
投加粉末活性炭对一体式膜-生物反应器膜污染的影响研究 总被引:8,自引:1,他引:8
通过试验考察了粉末活性炭(PAC)对一体式膜-生物反应器中膜污染的影响.在2种类型的污泥(膨胀污泥和非膨胀)中,投加适量PAC可以减轻膜污染,表现为临界膜通量的提高和连续运行中膜污染增长速率的降低.当污泥性质和浓度不同时,最佳PAC投加范围亦不同.PAC投量过大会引起临界通量下降.PAC的投加显著降低了混合液中溶解性物质的浓度,减轻了溶解性物质的吸附和膜孔堵塞污染,并改善了絮体结构.污泥比阻与污泥混合液膜过滤性能之间有很好的相关性,可作为污泥混合液膜过滤性能的快速评价指标. 相似文献
180.