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271.
为探究安全高效调控水绵生长的方法,本研究利用养殖水桶开展了两次生物操纵实验,分别观测了鲤(Cyprinus carpio)、鲫(Carassius auratus)和鲢(Hypophthalmichthys molitrix)在没有营养加富条件下,以及鲫和日本沼虾(Macrobrachium nipponense)在营养加富条件下,对水体中浮游态和固着态水绵(Spirogyra)生长的抑制效果.结果表明,在没有营养加富的水体中,鲤和鲫对水绵不仅没有调控效应,反而会促进水绵的生长.建议在水绵生长旺盛的水体中,一定程度上移除水体中这些鱼类反而可以有效控制水绵的生长.在营养加富条件下,日本沼虾对水绵的控制效应明显.鲫对水绵发挥的作用与水体营养状态存在交互作用,日本沼虾对水绵的抑制效应是否受水体营养状态的影响值得进一步探究. 相似文献
272.
Pathogenic viruses in drinking water are great threats to public health. Visible-light-driven photocatalysis is a promising technology for virus inactivation. However, the existing photocatalytic antiviral research studies have mostly been carried out in single-component systems, neglecting the effect of natural organic matter, which exists widely in actual water bodies. In this paper, electrospun Cu-TiO2 nanofibers were prepared as photocatalysts, and their photocatalytic antiviral performance in the presence of humic acid (HA) was comprehensively studied for the first time. The properties of the reaction mixture were measured during the reaction. In addition, the safety, reliability and stability of photocatalytic disinfection in the mixed system were evaluated. The results showed that the virus removal efficiency decreased with the increase of the HA concentration. The type of reaction solution, such as PBS buffer solution or water, did not affect the removal efficiency noticeably. Under acidic conditions, the electrostatic forces between photocatalysts and viruses were strengthened, leading to higher virus removal efficiency. As the reaction time went on, the pH value in the solution increased first and then tended to be stable, the conductivity remained stable, and the dissolved oxygen increased first and then decreased. The safety test showed that the concentration of Cu ions released into the solution was lower than specified by the international standards. No photoreactivation was observed, and the addition of HA significantly reduced the reutilization efficiency of the photocatalysts. 相似文献
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1 问题的提出 化学反应过程常常由于一些非预期的因素,如进料错误、杂质、反应器过热、冷却系统故障、外部火灾和搅拌失效等,使反应偏离正常操作范围,造成异常放热.若此时无法将所产生的热量迅速移除,则可能导致加速反应,形成自加速放热现象. 相似文献
276.
Shen H Virtanen HE Main KM Kaleva M Andersson AM Skakkebaek NE Toppari J Schramm KW 《Chemosphere》2006,62(3):390-395
The enantiomeric ratios (ER) of alpha-HCH and o,p'-DDT ((+)-isomer concentration/(-)-isomer concentration) and o,p'-DDD (first eluting enantiomer/second enantiomer) were investigated in 112 human placentas from Finnish boys collected 1997-2001. Both o,p'-DDD and alpha-HCH showed changes in their ER depending on the total concentration of the compound in the sample. Their ERs are approaching a value close to racemic mixture (ER=1) at high concentrations. At low concentrations they often differ from 1. The relationship between concentration and ER is clearly identified and it has been shown that it is not affected by analytical uncertainty. This relationship appears to be important for assessing tissue- and species-specific exposure and risk and it may indicate whether net uptake or metabolic activity is dominant in exposure for the resulting exposure of the enantiomers. 相似文献
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