PVDF/PMMA与PVDF/TPU共混膜抗污染性能研究及应用

观察新型五孔PVDF共混改性纤维膜SEM形貌特征,采用逐级通量法测定PVDF/PMMA和PVDF/TPU共混改性膜的临界通量,研究在次临界和超临界通量下A(PVDF/PMMA)与B(PVDF/TPU)2种管式膜组件的过滤和抗污染性能,并在次临界通量下处理地表水。结果表明,PVDF共混改性膜具有优良的微观结构,且膜B性能较好;膜A、B的临界通量分别为12 L/(m2.h)和10 L/(m2.h);膜组件B比膜组件A抗污染性能好。次临界通量下膜组件的运行比超临界通量下的稳定。与采用单独超滤处理某市地表水相比,2种膜组件采用混凝+超滤工艺的运行处理效果更好,且膜组件B比膜组件A处理效果佳。     

大气汞的来源及其浓度分布特征研究进展

大气汞是全球性的污染物,其来源有自然源和人为源,亚洲地区是最大的人为大气汞排放源,占全球人为排汞量的67％(质量分数),其中又以中国为最.燃煤和有色金属冶炼对中国大气汞排放的贡献最大.环境界面的释汞通量是全球大气汞预算的重要组成部分,也是目前的研究热点之一.综述了不同环境界面的释汞通量及其影响因素,并比较了不同地区大气...     

草甘膦母液膜分离的电渗析预处理

研究了用电渗析法去除草甘膦母液中影响膜通量的亚磷酸根,主要考察了pH值、工作电压、反应时间和温度等因素对亚磷酸根去除率的影响,并对电渗析预处理后母液纳滤膜分离的膜通量进行实验验证。实验表明：淡化液、浓缩液流量为30 L/h,pH值约为8.1,工作电压为20 V,反应时间为2 h左右,温度〈30℃时,电渗析对母液中亚磷酸...     

Seasonal and diurnal gas exchange differences in ozone-sensitive common milkweed (Asclepias syriaca L.) in relation to ozone uptake

Stomatal conductance and net photosynthesis of common milkweed (Asclepias syriaca L.) plants in two different soil moisture regimes were directly quantified and subsequently modeled over an entire growing season. Direct measurements captured the dynamic response of stomatal conductance to changing environmental conditions throughout the day, as well as declining gas exchange and carbon assimilation throughout the growth period beyond an early summer maximum. This phenomenon was observed in plants grown both with and without supplemental soil moisture, the latter of which should theoretically mitigate against harmful physiological effects caused by exposure to ozone. Seasonally declining rates of stomatal conductance were found to be substantial and incorporated into models, making them less susceptible to the overestimations of effective exposure that are an inherent source of error in ozone exposure indices. The species-specific evidence presented here supports the integration of dynamic physiological processes into flux-based modeling approaches for the prediction of ozone injury in vegetation.     

Estimation of emission fluxes from a horizontal flux budget method, exemplified with determination of pesticide volatilization

The paper describes an experimental set-up designed to measure the volatilization of different pesticides after application under full-scale field conditions. The pesticides were sprayed around the circumference of a circle and measurements of meteorology and air concentrations of pesticides were taken in the centre of the circle. The paper describes how the dimensions like the radius of the circle and height of the mast in the experimental set-up are found from theoretical considerations. A method to increase the confidence of the flux calculations is described. It utilizes that several substances were applied simultaneously and that a certain parameter in the fitted concentration profiles depends on turbulence only and thus have the same value for all substances. The design was used during two campaigns, conducted on the same location, one during fall on bare soil and one in spring on a barley crop.     

Distributions,Land-source Input and Atmospheric Fluxes of Methane in Jiaozhou Bay

CH₄ concentrations in both the surface and bottom waters of Jiaozhou Bay were determined during four surveys in 2003, which showed variability with both seasons and tidal cycles. Atmospheric fluxes of CH₄ in Jiaozhou Bay showed obvious seasonal and spatial variations, with the highest values occurring in summer and the lowest in winter. The annual emission of CH₄ from Jiaozhou Bay was estimated to be . CH₄ in the water column of Jiaozhou Bay was found to come from several land-sources including riverine water input, sewage water input and groundwater input. The spatial and temporal variation in distributions and atmospheric fluxes of CH₄ in Jiaozhou Bay was influenced mainly by the input of polluted river waters and the sewage effluents along the eastern coast, which highlights the effects of human impacts on CH₄ emission rates.     

有有效时间约束的最大流问题及其算法

交通运输在抗震救灾中起着非常重要的作用,无论是运输量的多少或是时间的及时与否,都直接影响着救灾的效果.而前人的单发点最短路径算法,难以满足救灾中多处救援物资及时到达和救援物资量上的需要.本文设计了确定救援站点(发点)的快速搜索程序,并在此基础上将单发点的救援路线问题扩展为多发点问题.同时考虑各条路段的最大运输量,使得出的紧急救援路线,不仅能满足救援物资的及时到达,同时又能满足对救援物资等运输量上的需求.     

酸沉降下韶山森林氮的输入、输出通量变化特征

以韶山蔡家塘森林小流域2001年实地监测的大气降水、穿透水和地表水数据为基础,对酸沉降作用下韶山森林N的输入、输出的月均通量及变化特征进行了研究.结果表明:2001年N输入通量为53.81 kg/hm2,主要以NH₄+ 形式(占总输入的64%)输入该森林生态系统;2001年N输出通量为3.57 kg/hm2,主要以NO₃-形式(占总输出的64%)输出该森林生态系统.韶山森林2001年N净滞留量达到50.24 kg/hm2.月均输出通量极大值出现在降雨量较多的5-7月,其N输出通量占全年N总输出通量的59%.从N的总输入通量、总输出通量的变化来看,N输出并不随输入的增加而增加,N的输出主要受到降水量的影响.      

A process-based model designed for filling of large data gaps in tower-based measurements of net ecosystem productivity

In this paper we present a simple hybrid gap-filling model (GFM) designed with a minimum number of parameters necessary to capture the ecological processes important for filling medium-to-large gaps in Flux data. As the model is process-based, the model has potential to be used in filling large gaps exhibiting a broad range of micro-meteorological and site conditions. The GFM performance was evaluated using “Punch hole” and extrapolation experiments based on data collected in west-central New Brunswick. These experiments indicated that the GFM is able to provide acceptable results (r² > 0.80) when >500 data points are used in model parameterization. The GFM was shown to address daytime evolution of NEP reasonably well for a wide range of weather and site conditions. An analysis of residuals indicated that for the most part no obvious trends were evident; although a slight bias was detected in NEP with soil temperature. To explore the portability of the GFM across ecosystem types, a transcontinental validation was conducted using NEP and ancillary data from seven ecosystems along a north-south transect (i.e., temperature–moisture gradient) from northern Europe (Finland) to the Middle East (Israel). The GFM was shown to explain over 75% of the variability in NEP measured at most ecosystems, which strongly suggests that the GFM maybe successfully applied to forest ecosystems outside Canada.