曝气对潜流人工湿地中木本植物的影响

为了增加人工湿地植物的多样性,本文将花叶冬青(Ilex aquifolium)、月季(Rosa chinensis)和八角金盘(Fatsia japonica)3种木本植物引入潜流人工湿地,比较曝气前后系统对污水处理效果,植物的生物量与对TN、TP负荷减少的贡献率,根系形态与内部结构、根际微生物与基质酶活性的比较研究。结果表明,木本植物潜流人工湿地系统曝气后可以提高COD、NH4+-N、TN、TP的去除率,分别为6.99%、4.91%、10.25%、8.09%。湿地曝气有利于3种木本植物的生长,在曝气后比曝气前生物量增加了381.75、606.25和896.88 g/m2。曝气会促使木本植物长出大量须根,且曝气后的根系具有大量由薄壁细胞组成的通气组织的水生根特征。同时,曝气后增加了硝化菌数量,各处理单元中硝化菌增量分别为A:0.28 MPN×104/g,B:4.23 MPN×104/g,C:7.7 MPN×104/g。另外,曝气后植物根际基质中磷酸酶和尿酶的含量增加量大约在50%以上,这与系统中N和P的去除率提高的规律一致。     

Bioavailability of copper and cadmium in sediment of nanjing section of Changjiang river to aquatic organisms

Bioavailabilities of metals in sediment to aquatic organisms depend on the strength of metal bonding to particulates. The accumulation tests of Cu and Cd in carp and in snails have been studied in vitro with the solution containing semisynthetic sediment samples in which the contents of various speciation of metal in sediment have been extended. For carp, the accumulation of Cu and Cd is related to the concentration of dissolved metal which in turn is affected by the distributions of speciations in sediment under given environmental conditions. It is another pattern for snails, various speciations of metal in sediment can contribute indirectly to metal accumulation. The contribution ratio, or relative importance of various speciations of metal in sediment can be expressed by multiple linear regression formulas. The contribution of ion‐exchangable speciation and coprecipition with carbonate speciation is 10⁵ times larger than that of residue speciation in sediment.     

Characteristics of geological hazards in South China coastal areas and impact on regional sustainable development

Prevention and treatment of geological hazards is important for the sustainable development of human society. Surface geological hazards alone caused direct economic losses of ¥3.47 billion, with 768 deaths and 785 injuries in Guangdong Province, South China, from 1994 to 2005. The major factors causing geological hazards can be categorised into three types: geo-environmental, climatic-meteorological and human activity. Accompanied by rapid economic development and population growth, human activities can cause geological hazards that are as serious as those caused by natural factors. The authors propose some suggestions for prevention and treatment of geological hazards to achieve sustainable development on the Chinese coast.     

The effect of macrophytes on retention times in a constructed wetland for wastewater treatment

Retention times of treated water in a constructed wetland (CW) with horizontal subsurface flow were determined both in the vegetative and non-vegetative periods of 2005. Tracer experiments were performed using fluorescein, an organic compound detectable at extremely low concentrations. Nominal and tracer retention times were determined and compared. Winter tracer retention time (TRT 194 h) and nominal retention time (nHRT 190 h) were nearly exactly equal, while summer TRT (335 h) was approximately twofold higher than nHRT (158 h). Residence time distribution function (RTD) was used to compare retention times obtained for the vegetative and non-vegetative periods. The obtained results document a significant influence of dense common reed vegetation on retention characteristics of the studied system. Common reed can convert a significant volume of water from liquid to gas via evapotranspiration (ET) and thus prolong water retention times in the system. This is very important both technically and ecologically. Longer retention times mean a longer time for microbiological decay of wastewater. Water converted from liquid to gas causes cooling of the microclimate, which is very important, especially in intensively cultivated areas with a lack of water.     

Crystalline mesoporous transition metal oxides: hard-templating synthesis and application in environmental catalysis

Mesoporous silicas such as MCM-41 and SBA-15 possess high surface areas, ordered nanopores, and excellent thermal stability, and have been often used as catalyst supports. Although mesoporous metal oxides have lower surface areas compared to mesoporous silicas, they generally have more diversified functionalities. Mesoporous metal oxides can be synthesized via a soft-templating or hard-templating approach, and these materials have recently found some applications in environmental catalysis, such as CO oxidation, N₂O decomposition, and elimination of organic pollutants. In this review, we summarize the synthesis of mesoporous transition metal oxides using mesoporous silicas as hard templates, highlight the application of these materials in environmental catalysis, and furnish some prospects for future development.     

One-pot preparation of graphene oxide magnetic nanocomposites for the removal of tetrabromobisphenol A

A simple solvothermal method was used to prepare monodisperse magnetite (Fe₃O₄) nanoparticles attached onto graphene oxide (GO) sheets as adsorbents to remove tetrabromobisphenol A (TBBPA) from an aqueous solution. These Fe₃O₄/GO (MGO) nanocomposites were characterized by transmission electron microscopy. The adsorption capacity at different initial pH, contact duration, and temperature were evaluated. The kinetics of adsorption was found to fit the pseudo-second-order model perfectly. The adsorption isotherm well fitted the Langmuir model, and the theoretical maximum of adsorption capacity calculated by the Langmuir model was 27.26 mg?g^-1. The adsorption thermodynamics of TBBPA on the MGO nanocomposites was determined at 303 K, 313 K, and 323 K, respectively. The results indicated that the adsorption was spontaneous and endothermic. The MGO nanocomposites were conveniently separated from the media by an external magnetic field within several seconds, and then regenerated in 0.2 M NaOH solution. Thus, the MGO nanocomposites are a promising candidate for TBBPA removal from wastewater.     

热解底泥对两种氟喹诺酮类抗生素和双酚A的吸附

将滇池断桥底泥在不同炭化温度(200℃—500℃)下制成热解底泥,用元素分析仪表征其元素组成.以诺氟沙星(NOR)、氧氟沙星(OFL)和双酚A(BPA)为代表化合物,研究人工合成有机污染物在热解底泥上的吸附行为,从而深入了解热解底泥的吸附特性以及其施用对有机污染物的环境行为和风险的影响.结果表明,热解底泥随炭化温度的增加,芳香性升高,极性降低,阳离子交换量降低,对NOR、OFL和BPA的吸附非线性增强.热解底泥的吸附性能比原始底泥更强,随炭化温度的升高,对NOR的吸附依次减弱,对OFL的吸附变化不大,对BPA的吸附依次增强,这与热解底泥极性和阳离子交换量,以及吸附质的极性相关.在原始底泥和热解底泥上,NOR和OFL的吸附均明显强于BPA,这主要因为NOR和OFL与底泥中无机矿物组分可通过阳离子交换作用和阳离子桥接作用使其吸附强于BPA,并且NOR和OFL相比于BPA官能团多且复杂.     

Selective recovery of Cu, Zn, and Ni from acid mine drainage

In Korea, the heavy metal pollution from about 1,000 abandoned mines has been a serious environmental issue. Especially, the surface waters, groundwaters, and soils around mines have been contaminated by heavy metals originating from acid mine drainage (AMD) and mine tailings. So far, AMD was considered as a waste stream to be treated to prevent environmental pollutions; however, the stream contains mainly Fe and Al and valuable metals such as Ni, Zn, and Cu. In this study, Visual MINTEQ simulation was carried out to investigate the speciation of heavy metals as functions of pH and neutralizing agents. Based on the simulation, selective pH values were determined to form hydroxide or carbonate precipitates of Cu, Zn, and Ni. Experiments based on the simulation results show that the recovery yield of Zn and Cu were 91 and 94 %, respectively, in a binary mixture of Cu and Zn, while 95 % of Cu and 94 % of Ni were recovered in a binary mixture of Cu and Ni. However, the recovery yield and purity of Zn and Ni were very low because of similar characteristics of Zn and Ni. Therefore, the mixture of Cu and Zn or Cu and Ni could be recovered by selective precipitation via pH adjustment; however, it is impossible to recover selectively Zn and Ni in the mixture of them.     

模拟日光照射下三种抗生素的光降解行为

选取四环素、土霉素、红霉素等3种国内普遍使用的抗生素,研究其在模拟日光(1.7 kW氙灯,300 nm≤λ≤400 nm)下的降解动力学行为.结果表明,3种抗生素在模拟日光下均能发生光降解,3 h的降解率分别达到66.87%、90.55%和92.80%.降解过程均符合准一级反应动力学方程,速率常数(k)分别为:0.0064、0.0138 min-1和0.0155 min-1;半衰期(t1/2)分别为:108.30、50.23、44.72 min.采用LC-MS分析推断3种抗生素主要降解产物,探讨了它们可能的光解途径.     

基于仿真实验的导轨结合面刚度建模方法研究

以分形理论和分形理论与域扩展因子为基础,设计了四种导轨动态接触刚度的理论计算模型,并将结果分别应用于仿真分析中,获得了四种不同方案下的有限元仿真分析结果;设计搭建了一种仅含导轨结合面的实验平台,并进行了模态试验;通过各方案仿真分析结果与实验的比较,获得了导轨结合面刚度建模方法的最优方案。