Comparisons of three plant species in accumulating polycyclic aromatic hydrocarbons (PAHs) from the atmosphere: a review

Environmental Science and Pollution Research - Plant leaves play a key role in the accumulation of PAHs, as they are able to capture PAHs from the air. In this paper, the mechanism, including...     

蚯蚓对土壤中有机化学成分组成的影响

蚯蚓是最为重要的土壤动物之一,不仅可以改良土壤结构和肥力,还能促进土壤矿物风化。为研究蚯蚓风化土壤矿物的机理,弄清蚯蚓对土壤中有机化学成分的影响,我们以甲醇为浸提剂浸提蚯蚓处理过的土壤和无蚯蚓的土壤,对提取物硅烷化衍生处理后,用GC-MS进行了分析。结果发现无论是蚯蚓处理过的土壤还是无蚯蚓的土壤,提取物中种类最多的化学物质是烃类,其次是酯类;腈类种类虽非常少,但相对含量却非常高。蚯蚓处理的土壤与无蚯蚓的土壤二者之间有机化学成分确实有很大的不同:从蚯蚓处理过的土壤中共发现了22种特有成分,从无蚓蚓的土壤中共发现了26种特有成分。虽然蚯蚓处理的土壤和无蚯蚓的土壤均检测到了微量的有机酸,但无论是酸的种类还是数量二者间均无明显差异。另外,检测结果也未发现铁载体。因此,蚯蚓诱导的微生物对土壤矿物的风化应该是在土壤矿物局部区域发挥作用,其风化机理用连宾的综合效应假说解释更为合理。     

Mercury enrichment in <Emphasis Type="Italic">Brassica napus</Emphasis> in response to elevated atmospheric mercury concentrations

Mercury enrichment in response to elevated atmospheric mercury concentrations in the organs of rape (Brassica napus) was investigated using an open top chamber fumigation experiment and a soil mercury enriched cultivation experiment. Results indicate that the mercury concentration in leaves and stems showed a significant variation under different concentrations of mercury in atmospheric and soil experiments while the concentration of mercury in roots, seeds and seed coats showed no significant variation under different atmospheric mercury concentrations. Using the function relation established by the experiment, results for atmospheric mercury sources in rape field biomass showed that atmospheric sources accounted for at least 81.81%of mercury in rape leaves and 32.29% of mercury in the stems. Therefore, mercury in the aboveground biomass predominantly derives from the absorption of atmospheric mercury.

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Preparation and characterization of activated carbons from tobacco stem by chemical activation

Activated carbons were prepared from tobacco stem by chemical activation using potassium hydroxide (KOH), potassium carbonate (K₂CO₃), and zinc chloride (ZnCl₂). The effects of the impregnation ratio (activating agent/precursor) and activating agents on the physical and chemical properties of activated carbons were investigated. The textual structure and surface properties of activated carbons were characterized by nitrogen (N₂) adsorption isotherm, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), and thermogravimetry (TG). ZnCl₂, acting as a superior activating agent compared to the others, produced much more porosity. The maximum specific surface area reached 1347 m²/g, obtained by ZnCl₂ activation with an impregnation ratio of 4.0. Moreover, ZnCl₂ activation yielded products with an excellent thermostability, attributed to different activation mechanisms. Various oxygen functions were detected on the activated carbon surface, and hydroxyl and ester groups were found to be in the majority.

Implications: Tobacco stem, the residue from cigarette manufacturing, is usually discarded as waste, leading to serious resource waste and environmental problems. This study provides an effective utilization available for this solid residue by using it as the starting material in the preparation of activated carbon with chemical activation. Activated carbons with high specific area and various surface functions have been prepared, and the effects of the amount and type of activating agents on the physical and chemical properties of activated carbon were investigated as well.     

“混凝气浮-膜生物反应器”处理林化废水工程运行调试研究

本文中根据林化废水特征确定使用“混凝气浮一膜生物反应处理器”的工艺进行处理。工程中硫酸铝的投加量为40mg／L,PAM的投加量为3mg／L,在废水pH值为7～8时进水COD、SS、OIL为279mg／L、20mg／L、26mg／L,进行混凝气浮后,出水的COD、SS、OIL浓度依次为135mg／L、9．6mg／L、9．5mg／L,去除率分别达到了52％、50％、64％。膜生物反应系统的调试,以污泥接种的方式进行污泥培养驯化。初期以面粉作为营养源清水培养污泥,按照7天左右的周期按每次30m3／d的污水进水量逐渐增加污水的比例,直到完全进水,调试驯化期污泥浓度控制在2500～3000mg／L。正常运转中污泥浓度可达到5000mg／L左右,出水水质COD、SS、OIL浓度分别达到30mg／L、6mg／L、3mg／L,符合处理目标要求。     

Modeling the longitudinal profiles of streamwise velocity in an open channel with a model patch of vegetation

This paper proposes a model for predicting the longitudinal profiles of streamwise velocities in an open channel with a model patch of vegetation. The governing equation was derived from the momentum equation and flow continuity equation. The model can estimate the longitudinal profiles of velocities both inside and outside a vegetation patch. Laboratory experiments indicate that the longitudinal profiles of velocities inside a patch and in the adjacent bare channel have the same adjustment distance in the longitudinal direction, but the profiles have different trends because the vegetation drag drives the flow from the patch to the adjacent bare channel. The model considers different dimensionless parameters in two flow adjustment regions upstream of and inside the patch. Sixteen sets of experimental data from different sources are used to verify the model. The model is capable of modeling the longitudinal profiles of velocities inside and outside patches of cylinders or cylinder-like plants. Compared to a previous model, the current model improves the modeling accuracy of longitudinal profiles of velocities.

     

城市环境空气中PM2.5和NO2浓度的相关性研究

以湖南省长沙市为研究区域,对城市环境空气中的PM2.5和NO2浓度进行自动监测,并对数据进行相关性分析.结果表明,PM2.5和NO2浓度的季节性变化大,且两者的变化规律一致,均为冬季＞秋季＞春季＞夏季;在一天内,NO2浓度的最低值一般出现在午后,但PM2.5浓度的最低值、峰值出现时间不确定;就功能区分布而言,NO2浓度最高值出现在商业区,而PM2.5浓度分布的区域规律不明显.PM2.5与NO2浓度变化以正相关为主,PM2.5浓度高时,NO2浓度高,反之亦然,两者容易产生叠加污染.总体上,冬、秋季节为PM2.5和NO2主要控制季节.     

“混凝气浮-膜生物反应器”处理林化废水工程运行调试研究

本文中根据林化废水特征确定使用"混凝气浮-膜生物反应处理器"的工艺进行处理。工程中硫酸铝的投加量为40mg/L,PAM的投加量为3mg/L,在废水pH值为7～8时进水COD、SS、OIL为279mg/L、20mg/L、26mg/L,进行混凝气浮后,出水的COD、SS、OIL浓度依次为135mg/L、9.6mg/L、9.5mg/L,去除率分别达到了52%、50%、64%。膜生物反应系统的调试,以污泥接种的方式进行污泥培养驯化。初期以面粉作为营养源清水培养污泥,按照7天左右的周期按每次30m3/d的污水进水量逐渐增加污水的比例,直到完全进水,调试驯化期污泥浓度控制在2500～3000mg/L。正常运转中污泥浓度可达到5000mg/L左右,出水水质COD、SS、OIL浓度分别达到30mg/L、6mg/L、3mg/L,符合处理目标要求。     

汞的微生物甲基化与去甲基化机理研究进展

甲基汞具有强烈的生物毒性和生物积累性,环境中甲基汞的产生主要与微生物相关,同时微生物也能通过去甲基化作用使甲基汞转变为无机汞.然而,目前国内外研究主要集中在汞的甲基化机理及影响因素,对汞的微生物去甲基化研究甚少.本文综述了汞的微生物甲基化、去甲基化研究史,以及微生物的主要作用机理,并对相关研究进行了展望,指出微生物酶促甲基化与氧化去甲基化机理研究将是以后工作的重点.