针铁矿对Pb~(2+)的吸附特征及影响因素研究

通过恒温振荡平衡法研究了Pb~(2+)在针铁矿上的等温吸附和吸附动力学特征,探讨了吸附的影响因素.结果表明:(1)随Pb~(2+)平衡浓度和pH的增大,针铁矿对Pb~(2+)的吸附量逐渐增大.(2)针铁矿对Pb~(2+)的等温吸附可用Freundlich和Langmuir方程较好地拟合.(3)在相同温度和pH下,随离子强度的提高,针铁矿对Pb~(2+)的吸附量增大.(4)在相同离子强度和pH下,针铁矿对Pb~(2+)的吸附量总体随温度升高而增大.针铁矿对Pb~(2+)的吸附是自发进行的吸热反应.(5)针铁矿吸附Pb~(2+)的过程可分为初始的快吸附和随后的慢吸附2个阶段.pH影响吸附反应快慢,随pH增大吸附速率增大;随着pH的增大,达到平衡吸附的时间缩短.吸附动力学方程用Elovich方程拟合最佳.     

The world agricultural system and ethical considerations relating to the rural environment: Some perspectives on cause and effect in underdeveloped countries

Food is a basic human need and therefore a basic human right. While food output has increased to a level where there is enough food produced to feed the world, still millions starve. Using the concept of capitalist world economy as a framework, this paper provides a structural analysis of the food production and distribution system within monopoly capitalism and its implications for countries of the underdeveloped world. Focusing on the impact of a dominant world food supply system on indigenous systems (particularly through the rise of science, technology, and monopoly capital), considerations relating to environmental use and food production and distribution are raised. Finally a call is made for a new agricultural ethic.     

建设项目环境影响的医学评价方法研究

作者在对中国我人民解放军第４７医院病建项目所产生的大气环境影响进行了医学秤价和影响，并在预测的基础上，建立了完整的环境医学影响廉政价方法，由于该评价方法完全尊循了国内现行大气环境影响评价的基本要求和程序，因此，它在今后的环境影响医学评价中净有广泛的应用。     

ANALYSIS OF WIND- AND SHIP-INDUCED SEDIMENT RESUSPENSION IN DULUTH-SUPERIOR HARBOR1

ABSTRACT: Suspended solids and ammonium concentration profiles measured at five locations in Duluth-Superior Harbor during July-October 1985 were analyzed to quantify wind and ship effects on sediment resuspension and resulting harbor water quality. Wind components from the SE quadrant correlated strongly with depth-averaged suspended solids concentrations that were unaffected by ship passage or thermal stratification. Winds from that quadrant have the largest fetch in the harbor. The highest correlation (r²= 0.93) was with the 6-hour average of the ESE wind velocity component. Multiple linear regression analysis of data from post-ship passage concentration profiles yielded numerical estimates of settling velocities of 0.08 to 0.25 cm s^?1, typical of ship-resuspended sediments, and vertical eddy diffusivities of 4 to 13 cm² s¹. The results suggest that ambient vertical eddy diffusivities in the harbor are less than 4 cm² s^?1 in the absence of ship passages and with winds less than 5 m s^?1 (10 knots).     

Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in compost

The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or copolymers with 10% [P(3HB-co-10%3HV)] and 20% [P(3HB-co-20%3HV)] 3-hydroxyvaleric acid was studied in small household compost heaps. Degradation was measured through loss of weight (surface erosion) and changes in molecular weight and mechanical strength. It was concluded, on the basis of weight loss and loss of mechanical properties, that P(3HB) and P(3HB-co-3HV) plastics were degraded in compost by the action of microorganisms. No decrease inM _w could be detected during the degradation process. The P(3HB-co-20%3HV) copolymer was degraded much faster than the homopolymer and P(3HB-co-10%3HV). One hundred nine microbial strains capable of degrading the polymersin vitro were isolated from the samples used in the biodegradation studies, as well as from two other composts, and identified. They consisted of 61 Gram-negative bacteria (e.g.,Acidovorax facilis), 10 Gram-positive bacteria (mainlyBacillus megaterium), 35Streptomyces strains, and 3 molds.     

ASSESSING FLUSHING-FLOW REQUIREMENTS FOR BROWN TROUT SPAWNING GRAVELS IN STEEP STREAMS1

Flushing flows are re1eses from dams designed to remove fine sediment from downstream spawning habitat. We evaluated flushing flows on reaches proposed for hydroelectric diversions on seven streams in the eastern Sierra Nevada, California, with wild populations of brown trout (Salmo trutta). The stream reaches are steep (average map slopes range from 7 to 17 percent), are dominated by boulder cascades, and afford few opportunities for gravel deposition. Methods for estimating flushing flows from flow records, developed from studies in other localities, produced widely differing results when applied to the study streams, probably reflecting differences in the hydrologic and geomorphic characteristics of the streams on which the methods were developed. Tracer gravel experiments demonstrated that all sampled gravels were washed out by the flows of 1986, a wet year. Size analyses of gravel samples and hydraulic data from field surveys were used in tractive-force calculations in an attempt to specify the flow required to flush the gravels. However, these calculations produced some unrealistic results because the flows were nonuniform in the study reaches. This suggests that the tractive-force approach may not be generally applicable to small, steep streams where nonuniform flow conditions prevail.     

O&M SPENDING LEVELS IN THIRD WORLD IRRIGATION SYSTEMS: EXPLORING ECONOMIC ALTERNATIVES1

ABSTRACT: Third World irrigation and drainage systems have experienced major declines recently in both capability and performance. This is due initially to working them well beyond their design capaci-capacities; scouring, sedimentation, and overtopping result. Chronic O&M underfunding then adds heavily to this worsening malaise. International donors have assisted irrigation departments with rehabilitation projects and programs to improve O&M effectiveness on a grand (billions of dollars) scale. Despite their historical propensity to examine, almost fastidiously, program economic justifications (B/C, IRR, etc), the donors apparently have glossed over two basic analytic elements for (a) more spending on O&M as distinct from an equivalent spending on other means to provide farmers with an m³ of water; and (b) different levels of O&M spending on canals and drains. Surely those different levels provide differing benefits, in total, and at the margin. Which level is most economic? This paper identifies these latter analytical issues, posits methodologies key to an O&M spending level analysis, and discusses the information base. Particular attention is paid to identifying relevant costs and benefits, and to suggesting supplementary criteria for O&M spending level selection. The paper is an exercise in delineation of an imminently practical area of irrigation engineering economics.     

Purification and characterization of extracellular poly(3-hydroxybutyrate) depolymerases

Five extracellular PHB depolymerases of bacteria isolated from various sources were purified to electrophoretic homogeneity and compared with known extracellular PHB depolymerase fromAlcaligenes faecalis T1. The molecular mass of these enzymes were all around 40–50 kDa. Nonionic detergent, diisopropylfluorophosphate and dithiothreitol inhibited the PHB depolymerase activity of all these enzymes. Trypsin abolished PHB depolymerase activity, but not theD-3-hydroxybutyric acid dimer hydrolase activity of all the enzymes. These results showed that the basic properties of these PHB depolymerases resemble those of theA. faecalis T1 enzyme. Analysis ofN-terminal amino acid sequence of the purified enzymes revealed that these enzymes includingA. faecalis T1 enzyme fall into three groups.     

关于职工情境意识的研究综述

对情境意识的定义、活动机制、测量方法及强化方法等进行了述评。分析了关于情境意识研究的问题及趋势。     

五氯酚对环境污染及居民健康影响研究

中国长期以来使用五氯酚纳盐杀灭亡血吸虫的中间宿主──—钉螺．为评价它对环境的污染及居民健康危害，１９９０－１９９３年在我省开展了五氯酚环境污染及对居民健康影响研究．在研究区采集环境样品（空气、水体、土壤及底泥、蔬菜、肉、蛋、鱼等）共１７３份；生物材料（人血、尿）共４５７份，分析五氯酚浓度．结果在明，在五氯酚使用区，环境中ＰＣＰ浓度稍高于对照区，而生物材料尿、血中ＰＣＰ浓度明显高于对照区．全血胆碱脂酶活性用药区明显低于对照区，统计学分析有显著差异（Ｐ＜０．００１），证实了长期低剂量使用可造成环境及生物蓄积．