The morphological structure of leaves and the dust-retaining capability of afforested plants in urban Guangzhou, South China

Purpose

Air pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. The mass artificial plantation is very helpful to absorb dust and reduce pollution for conservation of the urban environment. The foliar surface of plants is an important receptor of atmospheric pollutants. Therefore, selection of suitable plant species for urban environment is very important.

Methods

The dust-retaining capability of urban trees in Guangzhou was determined at four different types of urban area, and the morphological traits of their leaves such as wax, cuticle, stomata, and trichomes were observed under a scanning electron microscope.

Results

It was determined that the dust-retaining capability of any given tree species is significantly different in the same place. Of the four studied tree species in the industrial area (IA) and commercial/traffic areas (CTA) type urban areas, the highest amounts of dust removed by Mangifera indica Linn was 12.723 and 1.482?g/m², respectively. However, in contrast, the equivalent maxima for Bauhinia blakeana is only 2.682?g/m² and 0.720?g/m², respectively. Different plant species have different leaf morphology. The leaf of M. indica has deep grooves and high stomata density which are in favor of dust-retained, and thus, their dust-retained capability is stronger, while B. blakeana has the cells and epicuticular wax with its stomata arranging regularly, resulting in poor dust catching capability. Leaf size was also shown to be related to dust capture for the four studied tree species.

Conclusions

The dust removal capacity of individual tree species should be taken into account in the management of greening plantation in and around an urban area. It was also shown that temporal variation in dust accumulation occurred over the 28-day observation period and this was discussed. Furthermore, spatial contrasts in dust accumulation were evidenced by the data. This reflected the differing pollution loadings of the four urban-type areas. The highest amount of dust accumulation was associated with the industrial area in which shipyard and steelworks occurred whilst the lowest dust accumulation was associated with the grounds of the University which was the control area.     

PCR-DGGE研究亚硝化-电化学生物反硝化全自养脱氮工艺细菌多样性

采用分子生物学手段PCR-DGGE技术对亚硝化-电化学生物反硝化全自养脱氮工艺细菌的多样性进行了研究。结果表明,亚硝化段内主要的细菌种群为相似于Nitrosomonas sp.(AJ224410)和Nitrosomonas sp.NM41(AF272421)的种群,相似性分别为97%和94%;电化学生物反硝化段细菌类群主要有β-proteobacteria类群、γ-proteobacteria类群和Chlo-roflexi类群。填料上生物膜细菌种群较底部泥水混合物丰富,两者细菌种群相似性为75%;底部泥水混合物样中存在与厌氧氨氧化菌Brocadia anammoxidans(AF375994)相似性为93%的菌种,而填料上生物膜中存在与Thioalkalivibrio sp.K90mix(EU709865)和Thiobacillus thioparus(AJ243144)相似性分别为94%、97%的菌种,其中Thiobacillus thioparus(AJ243144)是典型的硫自养反硝化菌,表明填料上生物膜中有大量的硫自养反硝化菌。     

CABR处理分散式生活污水抗短期有机负荷潜能

为考察填料式厌氧折流板反应器（CABR）处理分散式生活污水抗短期有机负荷冲击的稳定性,从宏观运行性能、中间产物累积以及微观微生物活性3个层次来研究不同温度下短期有机负荷冲击对CABR运行性能影响。结果表明：宏观运行性能指标TCOD沿程变化曲线在28℃时受到有机负荷冲击仍呈现＂L＂型,容积负荷去除率也由基准条件下0.27kg/（m3.d）提高至0.73 kg/（m3.d）,但随温度的下降,沿程曲线逐渐接近＂／＂型,容积负荷去除率的增加幅度也逐渐变小。中间产物积累指标中VFA/碱度比值小于0.11～0.14时,TCOD去除率可达80%以上;SMP/SCOD比值沿水流方向呈上升趋势表明CABR抗负荷冲击性能较佳。而微观微生物酶活性受基质浓度提高的促进效应和温度下降的抑制效应相互作用表现各异。总体而言,在高温（28℃）条件下,分散式生活污水的有机负荷冲击不会对CABR出水造成显著影响,但在中温（18℃）和低温（10℃）条件下,CABR抗有机负荷冲击的稳定性随温度的下降而下降。     

消毒剂和溶解氧对管网铁释放影响的中试研究

针对南水北调中线水源地丹江口水库水调入受水区城市后,可能引起管网铁腐蚀产物释放的问题,从北方某受水区城市的实际管网中挖取了原通地下水的3个地点的铸铁管道,在丹江口搭建了中试模拟系统,开展水源切换以及消毒剂和溶解氧对管网铁释放影响的中试研究。结果表明,实验管道管垢较薄且稳定性较差,在水源切换初期有"黄水"现象发生;增加进水硫酸根浓度,管网系统出水总铁浓度和浊度均有所增加;在0.3~3.6 mg/L的范围内改变进水自由氯浓度对实验系统铁释放的影响没有明显的规律;但进水氯胺浓度从1.3 mg/L增加到2.0 mg/L时,YS系统的铁释放有所升高;进水溶解氧浓度从8 mg/L增加到15 mg/L时,实验系统的铁释放都有明显的降低,但再增加到20 mg/L时,铁释放反而有所升高。     

Erratum to: Quantification of land use/land cover changes in Pearl River Delta and its impact on regional climate in summer using numerical modeling

Regional Environmental Change -     

基于高阶动力格式的基底隔震结构地震响应分析∗

隔震支座在强烈地震作用下将产生复杂的动力响应,精确掌握地震响应行为及其规律是研发高质量隔震支座和进行隔震结构设计的基础。在进行结构地震响应分析,特别是非线性分析时,采用传统逐步积分方法以及低阶格式建立起的动力时程分析方法都难以达到高精度,而采用传统高阶时间积分算法则会出现计算过程繁琐,工作量大等情况。本文采用一种基于高阶动力格式的显式时间积分新式算法,应用于基底隔震结构的地震响应分析中。首先通过自由度凝聚缩减原理,建立设置隔震支座钢筋混凝土框架结构简化计算模型;同时采用隔震支座恢复力双切线本构模型构建基底隔震体系运动方程,并转化为状态方程;进而基于微分求积（DQ）原理编制高阶动力格式算法求解状态方程;最后分析一高层基底隔震结构,在高、中、低不同频率地震波下地震响应,验证该方法适用性。结果表明,①利用静态凝聚技术建立隔震结构模型,从而构建地震响应状态方程,是高阶动力分析方法实施的基础。②结构高阶动力分析方法仅通过矩阵乘法运算即可获得结构动力响应,可较好且高效地用于解决非线性地震响应分析问题。③将结构高阶动力分析方法应用于基底隔震结构,能获得隔震结构较为精确的分析结果。     

典型南方水源溶解性有机物分子量分布变化及去除特性

用超滤膜法对以东江为水源的深圳水库水体溶解性有机物(DOM)进行物理分级表征,研究了2005年3～9月原水中DOM分子量分布的连续变化特性,以及各分子量范围的DOM组分与消毒副产物三卤甲烷生成势(THMFP)之间的关系结果表明,在此原水DOM中,相对分子量小于1000的有机物所占比例最高(平均值为41.15%(以DOC计)),这说明东江原水中DOM主要以小分子量有机物为主,此分子量范围有机物所产生的THMFP在原水中所占比例均值为32.23%水处理研究表明,常规工艺和深度处理工艺对其DOC和THMFP的去除率均不高.对原水总DOC的贡献占第二位的是分子量在104～3×104之间的有机物(均值为24.07%),其对总THMFP的贡献率为29.09%,常规工艺对此分子量范围有机物去除效果很好.     

垂直潜流人工湿地低温净化效果及其与微生物作用关系

人工湿地净化过程受基质、微生物及植物的多重作用,但有关湿地系统水质净化效果与微生物之间的关联及响应机制的认识较为匮乏.本文针对垂直潜流人工湿地,分析了其低温条件下水质净化效果,通过16S rDNA扩增子测序技术,在OTU水平上利用微生物丰度聚类热图和基于Bray-Curtis距离的NMDS分析,揭示了湿地基质微生物群落结构的时空变化及其与主要水质指标之间的相互作用关系.结果表明,湿地对TN、COD的去除效果较好,但对TP的去除效果不佳.基质微生物群落时空变化显著,与湿地净化效果密切相关,革兰氏阴性菌门类众多和假单胞菌属相对丰度较低,分别是TN去除效果较好和TP去除效果不佳的重要原因.COD、DO是影响微生物群落的主要因子,而氮含量在一定程度上影响脱氮微生物的活跃度.基质微生物在湿地运行2周后,对污染物去除的介导作用稳定,建议设立这一关键时间点,并辅以菌群、碳源投入等措施,提升湿地的净化效果.     

连续流动分析法测定水中总磷不确定度的评定

在实验室分析基础上对连续流动分析法测定水中总磷过程的不确定度进行评定。本文建立了数学模型,对不确定度来源进行了分析,并计算了不确定度分量、合成不确定度及扩展不确定度,最后给出了总磷测量结果的标准表示方法。     

Effect of Al(III) speciation on coagulation of highly turbid water

In Taiwan, the turbidity of raw water for fresh water treatments can sometimes reach as high as 40 000 NTU due to intensive rainfall, especially in typhoon seasons. In response, water works often apply large quantities of coagulants such as polyaluminium chloride (PACl). In this study, simulated and natural highly turbid water was coagulated with two PACls, a commercial product (PACl-1) and a laboratory product (PACl-E). The Al species distributions of PACl-1 and PACl-E under various pH conditions were determined, and the corresponding coagulation efficiency was evaluated. The PACl-E has a wider range of operational pH, while the efficiency of PACl-1 peaks at around neutral pH. For simulated water up to 5000 NTU, the PACl-E was superior to PACl-1 at low dosage and in the pH range studied. Similar results were discovered with natural water, except that when the turbidity was extremely high, the coagulation efficiency of PACl-E decreased significantly due to the presence of large amounts of organic matter. The coagulation of PACl-E was closely related to the content of polycationic aluminium (Al₁₃) while that of PACl-1 was dictated by the amount of Al_c. The sludge from PACl-E coagulation had better dewaterability when the optimum dosage was applied. The experimental results suggest that for natural water up to 5000 NTU, PACl containing high Al₁₃ species is recommended for coagulation. In cases when the water contains high organic matter, efficient coagulation depends upon enmeshment by amorphous aluminium hydroxide.