取代苯胺和苯酚类化合物对大型蚤的毒性及PH值对其毒性的影响

测定了２４个取代苯胺和苯酚类化合物在不同ＰＨ下对大型蚤的２４ｈ半数抑制浓度２４ｈ－ＩＣ５０。结果表明,苯胺类的毒性随ＰＨ的升高而增大,酚类的毒性随ＰＨ的升高而减小。     

单甲脒盐酸盐的酸性、中性和碱性水解的动力学过程

单甲脒盐酸盐的酸性、中性和碱性水解的动力学过程颜文红，雷志芳，叶常明（中国科学院生态环境研究中心，北京１０００８５）关键词：单甲脒盐酸盐；水解；酸碱度。１引言单甲脒碱，化学名称为Ｎ—（２，４－二甲苯基）—Ｎ＇－甲基甲脒，简称ＤＭＡ，是一种新型高效的有...     

膜生物反应器短程硝化脱氮处理生活污水的研究

采用膜生物反应器处理模拟生活污水,研究了短程硝化生物脱氮的效果,试验结果表明:在中温(25～30℃),曝气量为0.15m3/h、pH值为7～8的条件下,COD去除率平均值为89.0%(最高达95.4%),出水氨氮在5.0mg/L以下(平均3.1mg/L),NO2-得到了富集,出水中基本监测不出NO3-,总氮去除率平均为86.2%(最高达94.0%),且系统对有机物与氮源的耐冲击负荷能力较好;曝气量和pH值是短硝化过程的重要影响因素。     

废水的硝化作用

硝化作用是废水生物脱氮中的关键。本文介绍了硝化作用的生化反应、硝化细菌的类群、硝化反应动力学和影响硝化作用的主要环境因子：溶解氧、ｐＨ、温度和毒物。     

水体pH和曝气方式对藻类生长的影响

利用水族箱微宇宙研究了藻类在不同pH和曝气条件下的生长和种类变化.使用天然湖水,一组试验每天调节pH,使其分别保持在8.0、8.5、9.0和9.5;另一组试验是设定不同的曝气方式,分别为不曝气、完全曝气、昼间曝气和夜间曝气,定期测定水体叶绿素a和藻类组成.pH试验结果显示,在pH 8.0～9.5范围内,pH 8.5下藻类生长状况最好,pH 9.5下生长最差,人为改变pH使其远离8.5能够抑制藻类生长.曝气试验结果显示,曝气不能抑制水体中藻类的生长,昼间曝气甚至还有明显的促进作用.     

Toxicity of tributyltin to willow trees

BACKGROUND: Tributyltin is an organotin compound, used as an antifouling agent in ship paint, with heavy impact on the marine environment. Contaminated dredged harbor sludge is now dumped on land. The toxicity of tributyltin (TBT) to trees has not yet been quantified. Eventually, a vegetation cover on the dumped sludge could be established for the purpose of non-food cash crop production and phytoremediation. METHODS: The phytotoxicity of tributyltin chloride (TBTCl) and tributyltin hydride (TBTH) was measured at pH 4 and at pH 7 using the willow tree transpiration test. Different pH levels of the nutrient solutions were achieved by adding ammonium salt (low pH) or nitrate (high pH) as nitrogen source. RESULTS AND DISCUSSION: At low pH (pH 4), all trees showed symptoms of poor health. Transpiration decreased at concentrations above or equal to 0.1 mg TBTCl/l and 1 mg TBTH/L. The TBT toxicity was more pronounced at pH 7. The trees survived even the highest dose of 10 mg/l TBTCl or TBTH, although their growth and transpiration was strongly reduced. CONCLUSION: In contrast to other organisms, TBTCl and TBTH were less toxic to higher plants. RECOMMENDATIONS AND OUTLOOK: The toxicity of TBT is no hindrance for establishing vegetation on TBT-contaminated sludge. Phytoremediation and cash crop production could be possible with suitable plants.     

MBR工艺短硝化反硝化处理生活污水的研究

以模拟生活污水为对象,研究了中温(25～30℃)条件下,膜生物反应器-短硝化反硝化生物脱氮的效果,试验结果表明,在曝气量为0.15 m3/h,pH值为7～8的条件下,出水COD保持在100 mg/L以下(平均49 mg/L),出水氨氮在5.0 mg/L以下(平均3.1 mg/L),NO2-得到了富集,出水中基本监测不出NO3-,总氮去除率平均为86.2%,最高达94.0%,且系统的耐冲击负荷能力较好;曝气量和pH值是短硝化过程的重要影响因素.     

An experimental ecotoxicological study and its application to the behavioural study of organic mercury (CH3HgCl) in the environment: influence of temperature and pH

Laboratory experiments were carried out to study the influence of temperature (24, 28 and 30 °C) and pH (1–10) on organic mercury (CH₃HgCl) transfer and accumulation in an experimental ecotoxicological model. We followed the evolution of CH₃HgCl in a basic model (water+air) by varying temperature and pH. In a second step, we completed the model by adding sediment and fish. We added CH₃HgCl to water at the beginning of each experiment which was repeated at least three times. Results demonstrated that mercury was released from methylmercury into the air regardless of water pH and its concentration in the air increased with increasing pH. By contrast, in presence of sediment, almost all the mercury was fixed onto the sediment and no mercury was traced in air or in water. Interestingly, in the presence of sediment, the life span of fish under methylmercury exposure lasted longer despite their higher mercury body level content at their death. These results indicate that water is a bad exposure indicator for aquatic pollution. In case of chronic pollution, sediments, fish and aquatic plants are more appropriate indicators.     

Kinetic studies of adsorption of thiocyanate onto ZnCl2 activated carbon from coir pith, an agricultural solid waste

The adsorption of thiocyanate onto ZnCl₂ activated carbon developed from coir pith was investigated to assess the possible use of this adsorbent. The influence of various parameters such as agitation time, thiocyanate concentration, adsorbent dose, pH and temperature has been studied. Adsorption followed second-order rate kinetics. Two theoretical adsorption isotherms, namely, Langmuir and Freundlich were used to describe the experimental results. The Langmuir adsorption capacity (Q₀) was found to be 16.2 mg g⁻¹ of the adsorbent. The per cent adsorption was maximum in the pH range 3.0–7.0. pH effect and desorption studies showed that ion exchange and chemisorption mechanism are involved in the adsorption process. Thermodynamic parameters such as ΔG⁰, ΔH⁰ and ΔS⁰ for the adsorption were evaluated. The negative values of ΔH⁰ confirm the exothermic nature of adsorption. Effects of foreign ions on the adsorption of thiocyanate have been investigated. Removal of thiocyanate from ground water was also tested.     

根际pH值与烤烟产量和质量的关系研究

主要研究了根际ｐＨ值对烤烟生长及其烟叶产质量的影响．结果表明，烤烟在伸根期和旺长后期对根际ｐＨ值的生长反应明显不同，微酸性的根际环境促进烟株前期生长，而微碱性则有利于烟株中后期烟叶的发育与成熟．烟叶产量和单叶重随ｐＨ上升至８．０而增加．根际ｐＨ值在５．５－７．５范围内变化时，烟叶外观质量变化不大．烟叶化学成分同样受到根际ｐＨ值的显著影响．