RELATIVE RATES OF EVAPORATIVE WATER LOSSES FROM OPEN AND VEGETATION COVERED WATER BODIES1

ABSTRACT: A review of literature pertaining to the relative rates of evaporation from vegetation covered and open water bodies is presented. The review indicates that the only reliable experiments capable of correctly addressing this question are those conducted in situ. Experiments of this nature show the ratio of vegetation covered (swamp) evaporation to open water evaporation to generally be less than unity over extensive surfaces and to only approach unity for vegetation that is young and vigorous. Recent experimental evidence presented within a theoretical context, however, indicates that even in the latter situation the ratio may never reach unity. Consequently, over large lakes and reservoirs, the presence of vegetation may actually be a water conservation mechanism, with the eradication of the vegetation leading to significantly increased evaporative water losses.     

Dynamics of Ammonia Exchange in Response to Cutting and Fertilising in an Intensively-Managed Grassland

Continuous micrometorological measurements of ammonia (NH₃)exchange were made for a period of 19 months (May 1998–November 1999) over intensively managed grassland in southern Scotland. This study focused on the influence of management activities, such as cutting and fertilising, on vegetation-atmosphere exchange of NH₃. Measurements were conducted within the European project GRAMINAE (GRassland AMmonia INteractions Across Europe) within which the Scottish site forms one of 6 sites in an E–W transect across Europe. NH₃ emissions were enhanced (up to 300 ng m^-2 s^-1) after cutting followed by larger emissions after fertilising (up to 1400 ng m^-2 s^-1). Annual budget calculations show the intensive grassland acted as a net source (1.8 kg N ha^-1 yr¹) although fluxes were bi-directional with deposition dominating in the winter and emission in the summer. Initial modelling of the NH₃ exchange using a `canopy compensation point' model has been conducted for key periods. The dynamics of the fluxes during these key periods, such as before and after cutting and fertilising, may be reproduced by introducing different values of the apoplastic ratio, = [NH₄ ⁺]/[H⁺].     

对氨基苯胂酸的生命周期评价

本文介绍了最常用的有机胂制剂——对氨基苯胂酸的主要用途和污染特征，从生命周期的角度识别并定量评价了其生产、使用和残留过程的环境影响，评价结果表明对氨基苯胂酸在土壤中最终残留的环境骰响占其整个生命周期的99％以上，指出了常规环境影响评价在评价其环境污染上的局限性，据此提出逐步减少或禁止有机胂制剂的生产和使用、并在一些特殊的建设项目环境影响评价中推广生命周期评价的建议。     

AFS-830型双道原子荧光光度计同时测定饮用水中砷、汞

主要探讨应用AFS-830型双道原子荧光光度计，在饮用水监测中同时测定水中砷、汞的方法和技术。此法是在硝酸介质，以硼氢化钠作还原剂，进行原子化，被测元素原子激发出荧光强度值在一定范围内与被测元素的浓度成正比。砷与汞的检出限分别为0．0618和0．0158ug／L。     

环境物探技术在岩溶勘察中的应用及其效果

将高密度电阻率法及工程地震映像法两种环境物探技术同时应用于实际的地质灾害(岩溶)勘察中,结果表明:对于岩溶这样的地质灾害,单一环境物探技术虽然能清楚反映其埋深、规模和发育情况,但各有缺陷。而多种环境物探技术的综合使用,相互补充,将能大大提高岩溶勘察的准确性,提高勘察效果和效率。     

Fe^0对饮用水中砷的去除效率及影响因素

研究零价铁（Fe^0）的除砷效果,试验考察了Fe^0投加量、接触时间、pH值、DO浓度、温度、腐殖质、竞争性阴离子（SO4^2-,NO^3-,SiO2^3-,H2PO3^-,HCO3^-）对Fe^0除砷效率的影响。结果表明,Fe^0（80目）投加量为2g/L,接触时间180min,pH值为6.5,DO值6.5mg/L的条件下,对质量浓度为1mg/L的含砷水样,Fe^0对As（Ⅴ）的去除率高达96.5%,而对As（Ⅲ）的去除率只有75.8%。降低水样pH值或提高DO可显著提高Fe^0的除砷效率,温度对Fe^0除砷影响不大,水体中的腐殖质、磷酸盐、硅酸盐的存在会由于竞争性吸附而导致Fe^0除砷效率下降。采用Fe^0颗粒去除饮用水中的砷高效、经济,具有良好的应用前景。实际应用中,对于DO值较低的地下含As水,可通过充氧提高Fe^0除As效率。当水体中腐殖质、磷酸盐或硅酸盐浓度较高时,应考虑采取相应的预处理措施。     

纳米二氧化钛处理含砷废水的研究

研究了无机纳米材料二氧化钛对含砷废水的处理效果.实验主要从纳米二氧化钛的溶液pH值、不同投加量、实验温度、吸附搅拌时间、静置时间等方面对除砷效率进行了研究,并通过模拟水样和实际水样的对比,分析了纳米二氧化钛处理含砷废水的实际可行性.     

Method of Testing the Penetration of Acid Solutions Through Safety Gloves

Because they cause burns that are difficult to heal, acids are dangerous, and steps should be taken to ensure that the human skin does not come into contact with them. For this purpose safety gloves are generally used by workers who have to handle acids. Such gloves need to be tested to ensure that they are acid resistant. Standard EN 374 (European Committee for Standardization [CEN], 1993c) specifies a method of testing the permeation of liquid chemicals, on a molecular level, through glove material, but it may be difficult to ensure the fitness of the joints of a two-compartment cell, when gloves are lined with jersey. To deal with this a simple pH-meter method to test the permeation of acid and alkali solutions through safety gloves has been developed. The permeation of H₂S0₄, HCI, HN0₃, and CH₃COOH through gloves made from neoprene, nitrile, and PVC was tested. This method seems to be simple and economical.     

Identification of a multixenobiotic resistance mechanism in Xenopus laevis embryos

In the '90's a membrane-associated transport protein, discovered in aquatic organisms, was considered to be expressed in response to environmental xenobiotics. Like the multidrug resistance protein found in mammalian tumor cell lines, this protein confers resistance in organisms in polluted areas by binding xenobiotics and transporting them out of the cells in an energy-dependent manner.This study investigates the expression and the activity of a P-glycoprotein (Pgp) involved in a multixenobiotic resistance mechanism (MXRW) during the early developmental stages and in tissues of adult Xenopus laevis.     

Structural-temporal organization of a rodent community in the Teletskaya Taiga,Altai Mountains

The structural-temporal organization of a murine rodent community in the taiga has been studied near Lake Teletskoe, Mountain Altai. The results show that the long-term dynamics of indices characterizing community diversity depend mainly on changes in the structure of dominance rather than on the population dynamics of species. The distribution of species in the factor space corresponds to their preference for certain biotopes, from dry to relatively moist. An analysis of relationships within the rodent community has revealed the synchronous dynamics of species abundance and antiphase pattern of changes in the structural indices of dominant species.