植物滞尘分析及其数学表达模式

在植被的树冠结构分析、植物滞尘机理和粉尘沉降速度半经验公式的基础上,建立了植物滞留大气颗粒物的数学表达式。利用Beta功能函数φθ(X)、叶面的投影面积、叶面积密度a(z)、叶投影面积分布参数Kx、Kz等描述不同植被冠层的结构特征,并分析了冠层内的空气动力变化和树冠内气溶胶的平衡公式。借鉴Slinn的颗粒物沉降半经验公式、Petroffa等的阔叶滞尘计算模式,植物滞尘沉降通量数学表达式以树冠中树叶的位置为变量、由颗粒物在单片树叶上的各物理机制的沉降速度积分而成。结合国内外植物上沉降速度的试验结果和植物滞尘沉降通量公式的分析结果对影响植物滞尘的主要因素进行了比较分析。     

CANOPY COVER AND SHADE DETERMINATIONS IN RIPARIAN ZONES1

ABSTRACT: Three instruments commonly used to measure stream canopy cover were evaluated: the clinometer, a modified spherical convex densiometer Model A, and a hemispherical image system. The hemispherical image system was also used to model shade. At each of five locations throughout Oregon, canopy cover above a stream was measured from the center of the stream along a series of transects. Vegetation along the reaches sampled ranged from a densely vegetated coastal forest stand to a sparsely vegetated eastern Oregon meadow. When techniques were compared within each site, canopy cover measured with the clinometer was similar to that measured with hemispherical imagery. The densiometer measurements, however, were typically lower than, though still highly correlated with, those derived from hemispherical images and from the clinometer. Because of site‐specific factors, the differences between all methods were significant in the Willamette and John Day Provinces. Canopy cover and shade were not equivalent for the streams studied.     

Biodegradation of Endosulfan by a Soil Bacterium

A bacterium capable of metabolizing endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine3-oxide) was isolated from cotton-growing soil and effectively shown to degrade endosulfan into endosulfan sulfate. The bacterium degraded 50% of the compound within 3 days of incubation. Endosulfan sulfate was the only terminal product and no other metabolites were formed during the incubation. Endosulfan and its metabolites were analyzed by gas chromatography. The metabolites formed indicated that the organism follows an oxidative pathway for metabolism of this pesticide. Therefore, the present study, microbial degradation of endosulfan by a soil bacterium, may provide a basis for the development of bioremediation strategies to remediate the pollutants in the environment.     

Estimating the removal of atmospheric particulate pollution by the urban tree canopy in Beijing北大核心CSCD

Urban green space, particularly the tree canopy, plays an important role in potential mitigation against atmospheric particulate pollution and protecting human health. In this study, current and future air particulate matter [including total suspended particulate (TSP), particulate matter 10 (PM10), and particulate matter 2.5 (PM2.5)] removal by the urban tree canopy of Beijing was estimated. A modeling approach was used based on the distributed measurement evaluation and a modified version. The urban tree canopy of Beijing, including mostly Platycladus sp., Pinus sp., Quercus sp., Robinia pseudoacacia, and economic forests, currently removes about 8.33 million kg/a air particulates, in which TSP accounted for 4.51 million kg/a, PM10 accounted for 2.74 million kg/a, and PM2.5 accounted for 1.08 million kg/a. The study on the removal of air particulates by different aged tree canopies showed that in coniferous trees, the ability to capture air particulates changed in the order of mature and over-mature > near-mature forest > young forest; in broadleaf forest, the ability changed in the order of near-mature forest > mature and over-mature > young forest. For total particulate matter, the biggest contribution was coarse particulates (60.74%); the contribution rate of fine particulates was different owing to different tree species groups. The results suggested that the ability of different trees to capture particles and age of forests varied widely and that suitable trees should be chosen to enhance pollution mitigation for city greening. © 2018 Science Press. All rights reserved.     

EVAPOTRANSPIRATION AND CANOPY RESISTANCE AT AN UNDEVELOPED PRAIRIE IN A HUMID SUBTROPICAL CLIMATE1

ABSTRACT: Reliable estimates of evapotranspiration from areas of wildland vegetation are needed for many types of water-resource investigations. However, little is known about surface fluxes from many areally important vegetation types, and relatively few comparisons have been made to examine how well evapotranspiration models can predict evapotranspiration for soil-, climate-, or vegetation-types that differ from those under which the models have been calibrated. In this investigation at a prairie site in west-central Florida, latent heat flux (λE) computed from the energy balance and alternatively by eddy covariance during a 15-month period differed by 4 percent and 7 percent on hourly and daily time scales, respectively. Annual evapotranspiration computed from the energy balance and by eddy covariance were 978 and 944 mm, respectively. An hourly Penman-Monteith (PM) evapotranspiration model with stomatal control predicated on water-vapor-pressure deficit at canopy level, incoming solar radiation intensity, and soil water deficit was developed and calibrated using surface fluxes from eddy covariance. Model-predicted λE agreed closely with λE computed from the energy balance except when moisture from dew or precipitation covered vegetation surfaces. Finally, an hourly PM model developed for an Amazonian pasture predicted λE for the Florida prairie with unexpected reliability. Additional comparisons of PM-type models that have been developed for differing types of short vegetation could aid in assessing interchangeability of such models.     

我国棉花主要病虫害综合防治技术研究的方向与对策

就棉花病虫害预测预报、防治指标与防治策略、抗病虫品种鉴定与选育、主要害虫抗药性监测与治理、农药新品种开发、天敌保护利用、应用基础研究、棉田玉米螟防治技术等综述了“八五”期间我国综合防治研究的进展和现状。并指出了当前存在的主要问题及今后棉花病虫综合防治的发展方向与对策。     

A Numerical Study for Turbulent Flow and Thermal Influence over Inhomogenous Canopy of Roughness Elements

A large-eddy simulation with transitional structure function(TSF) subgrid model we previously proposed was performed to investigate the turbulent flow with thermal influence over an inhomogeneous canopy, which was represented as alternative large and small roughness elements. The aerodynamic and thermodynamic effects of the presence of a layer of large roughness elements were modelled by adding a drag term to the three-dimensional Navier–Stokes equations and a heat source/sink term to the scalar equation, respectively. The layer of small roughness elements was simply treated using the method as described in paper (Moeng 1984, J. Atmos Sci. 41, 2052–2062) for homogeneous rough surface. The horizontally averaged statistics such as mean vertical profiles of wind velocity, air temperature, et al., are in reasonable agreement with Gao et al.(1989, Boundary layer meteorol. 47, 349–377) field observation (homogeneous canopy). Not surprisingly, the calculated instantaneous velocity and temperature fields show that the roughness elements considerably changed the turbulent structure within the canopy. The adjustment of the mean vertical profiles of velocity and temperature was studied, which was found qualitatively comparable with Belcher et al. (2003, J Fluid Mech. 488, 369–398)’s theoretical results. The urban heat island(UHI) was investigated imposing heat source in the region of large roughness elements. An elevated inversion layer, a phenomenon often observed in the urban area (Sang et al., J Wind Eng. Ind. Aesodyn. 87, 243–258)’s was successfully simulated above the canopy. The cool island(CI) was also investigated imposing heat sink to simply model the evaporation of plant canopy. An inversion layer was found very stable and robust within the canopy.     

棉浆粕综合废水的生物处理研究

浆粕厂在生产粘胶纤维原料时产生的有机废水，其组分较为复杂，废水治理具有一定的技术难度。采用水解酸化－好氧法与传统活性污泥法两种方案对棉浆粕生产综合废水进行生物处理的平行对照表明，驯化活性污泥可有效地去除废水中易生物降解的有机物。娄浆粕废水进水ＣＯＤｃｒ浓度在（１２００～１８００）ｍｇ／Ｌ范围内，ＣＯＤｃｒ负荷（１．８～２．８）ｋｇ／（ｍ＾３．ｄ）时，ＣＯＤｃｒ去除率可达５８％～６４％，ＢＯＤ５去除     

铁屑过滤—SBR工艺处理棉纺印染废水

采用铁屑过滤－ＳＢＲ工艺处理棉纺印染废水，结果表明，当进水ＣＯＤ为５００－１３００ｍｇ／Ｌ，色度为１００－２００倍，ＢＯＤ５１１２０－３００ｍｇ／Ｌ，时，ＣＯＤ去除率可达８５％，ＢＯＤ５去除率和脱色率均在９０％以上，出水达到了排放标准，该工艺较适合于中小型印染厂废水处理。     

底墒对小麦根冠生长及土壤水分利用的影响

在中国气象局固城农业气象试验基地大型水分试验场,进行了不同底墒处理对冬小麦根冠生长发育、产量构成因子和土壤水分利用影响的试验,不同底墒处理对应的播种时的土壤相对湿度分别为:>80％,75％～80％,70％～75％,65％～70％和<65％。结果表明:底墒对冬小麦的根、茎、叶等有不同程度的影响,其中对根的影响尤为显著。充足的底墒能够促进根系对土壤水分和养分的吸收,提高土壤水分利用率,使收获时土壤残留水分减少,扩充了土壤水库的库容,使其能够在汛期到来时,接纳蓄存更多的降水,充分发挥土壤水库的调控功能。叶的生长发育与底墒之间也存在明显的相关关系,底墒与叶面积指数存在着显著的幂函数关系;底墒对总穗数、穗粒数、千粒重和地上总干物重等有显著影响,小麦的穗粒重和底墒有显著的二次曲线(抛物线)关系,由此求得最佳底墒为85.37％(占田间持水量百分比)。