无机微滤膜分离草浆黑液中木素的机理

选用50nm,0.2μm和0.8μm的无机微滤膜,研究了它们对黑液中木素的截留效果.结果表明,微滤膜能够有效地分离黑液中的木素,0.2μm α-Al₂O₃和ZrO₂膜的通量高于50nm和0.8μm膜的通量,当黑液SS较低时,随着SS浓度的增加各个微滤膜的通量急剧下降,当SS较高时,微滤膜的通量和SS浓度成线性关系.2g/L聚乙二醇4000(PEG4000)溶液不会显著影响0.2μm和50nm膜的通量,但却能使0.8μm膜的通量下降60%.2g/L聚乙二醇20000(PEG20000)溶液能使各个微滤膜的通量急剧下降.按照微滤膜污染模型的计算结果和实测被稀释黑液的粒径分布,膜面形成滤饼层和木素分子形成的絮体是引起膜通量下降并改变了膜的截留性能的原因.     

THE STATE OF LOUISIANA SUPERPORT AUTHORITY ENVIRONMENTAL PROTECTION PLAN – OIL AND OYSTERS1

ABSTRACT: The State of Louisiana created in 1972 the Deep Draft Harbor and Terminal Authority (commonly called Superport Authority) to plan, promote, and develop a deepwater (crude oil) terminal off the coast of Louisiana, and empowered it to establish an Authority development program to promote the economic and social welfare of its citizens. Simultaneously, the Authority was also charged with developing an environmental protection plan to preserve the environmental values of Louisiana's unique coastal marshland while permitting beneficial industrial and economic development. Consequently, in January 1974, an Environmental Protection Plan was promulgated, consisting of a series of regulations, design standards, and operating procedures aimed specifically at protecting the fragile estuarine environment of coastal Louisiana during the construction and ultimate operation of the superport. The paper describes the development of the Superport Authority's Environmental Protection Plan and the current status of the superport project.     

新建铁路站区对城市环境噪声影响特征及预测研究

在铁路车站噪声影响中,车站影响区域产生的次生噪声相对于站中心的原生噪声,是城区噪声污染的主要因素。根据不同规模车站区对周边社会及人文景观的影响程度,划分出站区噪声监测范围。通过监测对比分析,发现站中心噪声与车站规模具有显著的正相关关系,而车站影响区噪声值在中小规模车站中,二者有一定的正相关关系,但当车站发展到一定大规模后,影响区内的噪声反而略有下降并趋于平稳。通过分析认为,大规模车站的建立有利于促进周边城市更合理地规划布局。根据车站布局与兴建对城市环境噪声影响的关系,以及站区噪声源变化特点,建立了不同车站规模站区的噪声值预测模型,其预测结果为新建铁路路站在城市中的规划布局,提供了实用的参考依据及有价值的建议。     

ON THE MISMATCH BETWEEN DATA AND MODELS OF HYDROLOGIC AND WATER RESOURCE SYSTEMS1

ABSTRACT: Many difficulties exist in the matching of models with data. This paper identifies elements of this problem and discusses considerations involved in model evaluation. The well known multivariate linear regression model is used to illustrate the distinctions between accuracy and precision and between estimation and prediction (because the model is commonly misused.) No amount of additional data will improve the accuracy of a poor model. A high R², while indicative of a good matching between the observed data and model estimates, is a poor criterion for judging adequacy of the model to make good predictions of future events. Model evaluation also includes the problem of introducing secondary data and proxy variables into a model. Secondary data frequently enter, for example, the mass, energy and water budget equations because of difficulties in measuring the primary variables. Proxy variables arise because of a desire to collapse a vector of incomparable values, say, of water quality into a single number. Review of the above issues indicates that model evaluation is a multi-criterion problem, often imbedded in a larger framework where models are intended to meet multiple objectives. The mismatch of models and data has increasing legal and social consequences.     

The Precautionary Principle: Scientific Uncertainty and Omitted Research in the Context of GMO Use and Release

Commercialization of genetically modified organisms (GMOs) have sparked profound controversies concerning adequate approaches to risk regulation. Scientific uncertainty and ambiguity, omitted research areas, and lack of basic knowledge crucial to risk assessmentshave become apparent. The objective of this article is to discuss the policy and practical implementation of the Precautionary Principle. A major conclusion is that the void in scientific understanding concerning risks posed by secondary effects and the complexity ofcause-effect relations warrant further research. Initiatives to approach the acceptance or rejection of a number of risk-associated hypotheses is badly needed. Further, since scientific advice plays a key role in GMOregulations, scientists have a responsibility to address and communicate uncertainty to policy makers and the public. Hence, the acceptance of uncertainty is not only a scientific issue, but is related to public policy and involves an ethical dimension.     

Atmospheric Deposition of Reactive Nitrogen on Turf Grassland in Central Japan: Comparison of the Contribution of Wet and Dry Deposition

The atmospheric deposition of reactive nitrogen on turf grassland in Tsukuba, central Japan, was investigated from July 2003 to December 2004. The target components were ammonium, nitrate, and nitrite ions for wet deposition and gaseous ammonia, nitric and nitrous acids, and particulate ammonium, nitrate, and nitrite for dry deposition. Organic nitrogen was also evaluated by subtracting the amount of inorganic nitrogen from total nitrogen. A wet-only sampler and filter holders were used to collect precipitation and the atmospheric components, respectively. An inferential method was applied to calculate the dry deposition velocity of gases and particles, which involved the effects of surface wetness and ammonia volatilization through stomata on the dry deposition velocity. The mean fraction of the monthly wet to total deposition was different among chemical species; 37, 77, and 1% for ammoniacal, nitrate-, and nitrite-nitrogen, respectively. The annual deposition of inorganic nitrogen in 2004 was 47 and 48 mmol m⁻² yr⁻¹ for wet and dry deposition, respectively; 51% of atmospheric deposition was contributed by dry deposition. The annual wet deposition in 2004 was 20, 27, and 0.07 mmol m⁻² yr⁻¹, and the annual dry deposition in 2004 was 35, 7.4, and 5.4 mmol m⁻² yr⁻¹ for ammoniacal, nitrate-, and nitrite-nitrogen, respectively. Ammoniacal nitrogen was the most important reactive nitrogen because of its remarkable contribution to both wet and dry deposition. The median ratio of the organic nitrogen concentration to total nitrogen was 9.8, 17, and 15% for precipitation, gases, and particles, respectively.     

寒区湿地软土固结变形特性试验研究

软土的成因不同,其工程性质存在着一定的差异,路基的固结沉降也不一样。为了研究寒区湿地软土固结变形特性,弄清其固结和次固结系数变化规律,对两类软土进行了单向固结压缩试验。试验结果表明,软土在不同的固结压力作用下,其孔隙比-时间对数曲线展布特征有较大的不同,说明固结压力对寒区湿地软土的主、次固结的划分有影响;寒区湿地软土主固结系数随固结压力的增大而减小,次固结系数随固结压力的增大而增大,最后两者都趋于稳定。     

离子色谱法测定植物叶片中氟的探讨

植物叶片中氟的测定一般采用离子选择电极法,离子色谱法对其测定还鲜见报道,本文对用离子色谱方法测定植物叶片中的氟进行了探讨。     

城市污水二级处理出水中沙门氏菌的PCR检测

建立了一种利用PCR检测城市污水二级处理出水中沙门氏菌的方法.采用膜吸附-洗脱法浓缩二级出水水样中的沙门氏菌,通过选用一对涵盖性和特异性均较强的引物139和141,对浓缩后的沙门氏菌进行PCR检测.利用正交试验法,对沙门氏菌PCR体系进行五因素四水平的试验,建立了沙门氏菌PCR的最佳体系.通过梯度PCR考察了退火温度对检测结果的影响,选择65℃作为退火温度,优化后沙门氏菌PCR体系的检测灵敏度可达0.314ngL.通过对已知细菌浓度的水样进行检测,确定了该法检测水样中沙门氏菌的灵敏度为2130CFUL.与传统MPN法的相比,该法在检测效果和检测效率上都优于MPN法.     

Eperimental study of photooxidation products of ethylbenzene

Smog chamber experiments were performed to investigate the composition of products formed from photooxidation of aromatic hydrocarbon ethylbenzene.Vacuum ultraviolet photoionization mass spectrometer and aerosol time-of-flight mass spectrometer were used to measure the products in the gas and particle phases in real-time.Experimental results demonstrated that ethylphenol,methylglyoxal,phenol,benzaldehyde,and 2-ethylfurane were the predominant photooxidation products in both the gas and particle phases.However,there were some differences between detected gas phase products and those of particle phase,for example,2-ethylfurane,ethylglyoxylie acid,nitroethylbenzene,3,4-dioxopentanal and ethyl-nitrophenol were only existing in the particle-phase.The possible reaction mechanisms leading to these products were also discussed and proposed.