The effect of commuting microenvironment on commuter exposures to vehicular emission in Hong Kong

Vehicular exhaust emission has gradually become the major air pollution source in modern cities and traffic related exposure is found to contribute significantly to total human exposure level. A comprehensive survey was conducted from November 1995 to July 1996 in Hong Kong to assess the effect of traffic-induced air pollution inside different commuting microenvironments on commuter exposure. Microenvironmental monitoring is performed for six major public commuting modes (bus, light bus, MTR, railway, tram, ferry), plus private car and roadside pavement. Traffic-related pollutants, CO, NO_x, THC and O₃ were selected as the target pollutants. The results indicate that commuter exposure is highly influenced by the choice of commuting microenvironment. In general, the exposure level in decreasing order of measured pollutant level for respective commuting microenvironments are: private car, the group consisting light bus, bus, tram and pavement, MTR and train, and finally ferry. In private car, the CO level is several times higher than that in the other microenvironments with a trip averaged of 10.1 ppm and a maximum of 24.9 ppm. Factors such as the body position of the vehicle, intake point of the ventilation system, fuel used, ventilation, transport mode, road and driving conditions were used in the analysis. Inter-microenvironment, intra-microenvironment and temporal variation of CO concentrations were used as the major indicator. The low body position and low intake point of the ventilation system of the private car are believed to be the cause of higher intake of exhaust of other vehicles and thus result in high pollution level in this microenvironment. Compared with other metropolis around the world and the Hong Kong Air Quality Objectives (HKAQO), exposure levels of commuter to traffic-related air pollution in Hong Kong are relatively low for most pollutants measured. Only several cases of exceedence of HKAQO by NO₂ were recorded. The strong prevailing wind plus the channeling effect created by the harbor, the fuel used, the relative abundance of new cars and the successful implementation of the vehicle emission control program are factors that compensate the effect of the emission source strength and thus lead to low exposure levels.     

纳米银在水环境中的环境行为和毒性效应研究进展

纳米材料的环境行为和生态效应是目前国内外研究的热点,其中纳米银颗粒(Ag NPs)是使用量最高的纳米材料。本文主要总结了Ag NPs在水环境中的赋存、Ag NPs的环境行为、Ag NPs对不同种类微生物的毒性效应以及影响Ag NPs毒性效应的因素,最后对Ag NPs在河口区的研究进行了展望。     

Leaching variations of heavy metals in chelator-assisted phytoextraction by Zea mays L. exposed to acid rainfall

Chelant-enhanced phytoextraction method has been put forward as an effective soil remediation method, whereas the heavy metal leaching could not be ignored. In this study, a cropping-leaching experiment, using soil columns, was applied to study the metal leaching variations during assisted phytoextraction of Cd- and Pb-polluted soils, using seedlings of Zea mays, applying three different chelators (EDTA, EDDS, and rhamnolipid), and artificial rainfall (acid rainfall or normal rainfall). It showed that artificial rainfall, especially artificial acid rain, after chelator application led to the increase of heavy metals in the leaching solution. EDTA increased both Cd and Pb concentrations in the leaching solution, obviously, whereas EDDS and rhamnolipid increased Cd concentration but not Pb. The amount of Cd and Pb decreased as the leaching solution increased, the patterns as well matched LRMs (linear regression models), with R-square (R ²) higher than 90 and 82% for Cd and Pb, respectively. The maximum cumulative Cd and Pb in the leaching solutions were 18.44 and 16.68%, respectively, which was amended by EDTA and acid rainwater (pH 4.5), and followed by EDDS (pH 4.5), EDDS (pH 6.5), rhamnolipid (0.5 g kg⁻¹ soil, pH 4.5), and rhamnolipid (pH 6.5).

     

FGD脱硫废水处理工艺及其优化设计

阐述了脱硫废水中污染物的去除机理,介绍了化学-机械沉降去除脱硫废水中悬浮物、重金属元素等物质的废水处理工艺,并对脱硫废水处理系统的优化设计进行了重点论述。     

Polybrominated dibenzodioxins and -furans from the pyrolysis of some flame retardants

Purified 2,4,6-Tribromophenol, Pentabromophenol, Tetrabromobisphenol A and Tetrabromophthalic anhydride were pyrolyzed at 700°C, 800°C and 900°C. DBrDD, T3BrDD, T4BrDD (up to 89.6%), PBrDD, DBrDF, T3BrDF, and PBrDF were formed from 2,4,6-tribromophenol. From pentabromophenol PBrDD, H6BrDD, H7BrDD, OBrDD, PBrDF, H6BrDF, H7BrDF and OBrDF were formed. The burning of tetrabromobisphenol A gave MBrDD, DBrDD, T3BrDD, T4BrDD, MBrDF, DBrDF, T3BrDF and T4BrDF. In the residues of thermal reactions from tetrabromophthalic anhydride no PBrDD/PBrDF could be found. In all these studies the maximum of PBrDD/PBrDF-formation was at 800°C. The absence of PBrDD(PBrDF from the pyrolysate of tetrabromophthalic anhydride may guide the development of new brominated flame retardants, since certain structural features may suppress the formation of PBrDD/PBrDF.     

超声强化混凝去除蓝藻实验研究

研究了超声波对藻类的混凝去除强化,证明超声波可以快速、高效地提高藻类混凝去除效率,减少混凝剂用量.在混凝剂投加量为0.8 mg/L时,5 s超声处理,藻类去除效果比对照样好30%.同样,藻类去除率都为92%时,5 s超声预处理可以将混凝剂投加量降低至1/3.超声预处理时间对强化混凝效果有很大的影响,在实验条件下,1～5 s的超声处理均可产生满意的结果,1 s为最优、最经济时间,而预处理超过30 s反而降低混凝效果.低频下不同处理频率对超声强化混凝效果影响不大,在80 kHz的频率下,最佳功率为50 W.最佳pH值在8～9范围内.     

反应沉淀一体式矩形环流生物反应器的传氧特性研究

设计制作了一种新型的反应沉淀一体式矩形环流生物反应器,通过清水实验研究了其结构特性(环流区内导流板顶端与液面的距离,固定宽度下环流区长度变化)对反应器充氧性能、气含率、气体上升速度和液体循环速度的影响,并在优选结构的反应器中进行了模拟污水试验.结果表明,当升流区截面长度、降流区截面长度、内导流板顶部液流截面高度三者相等时,传氧性能较好,在进水COD为300～400 mg/L的情况下,污泥浓度可以稳定保持在6000 mg/L左右.     

活性炭的电解氧化再生研究

通过比较饱和吸附苯酚的活性炭的交换再生和电解再生,揭示了电解再生比交换再生有更高的再生效率。无论是单独的阳极再生还是阴极再生,其再生效率均可超过80%,但由于阳极区的氧化性,可以时苯酚在活性炭的表面聚合,从而降低了再生效率和活性炭的吸附性能。同时,在研究的体系内,200 mA认为是电解过程中最佳的电流强度,这一电流强度不但可以有效地再生活性炭,还可以有效地去除再生出来的苯酚。较小粒径的活性炭不仅有较高的吸附效率,而且也有较高的电解再生效率。     

接种内生细菌对龙葵吸收积累镉的影响

通过在LB培养基中加入不同浓度的镉,从镉超富集植物龙葵植株内分离到3株很强的镉抗性内生菌株N1、N2、N4,最高耐受镉浓度达300 mg·L^-1.通过生理生化鉴定和16S rDNA序列分析,初步确定N1为芽孢杆菌属（Bacillus sp.）细菌,N2为肠杆菌属（Enterobacter sp.）细菌,N4为巨大芽孢杆菌（Bacillus megaterium）.将龙葵种植在含有一定镉（50 mg·kg^-1）的土壤中进行盆栽试验,以灌根的方式分别接种分离到的3株细菌及其混菌组合,并对其株高、生物量及镉吸收能力进行分析.结果显示,N4菌株处理的龙葵叶、茎、根部镉含量比不接菌对照分别增加32.94%、14.50%、23.44%,差异显著（p<0.05）;接种N1+N2+N4混菌的处理龙葵叶、茎和根干重分别比不接菌对照高出118.22%、109.83%和113.01%,植株地上和地下镉吸收总量分别增加109.53%和83.01%,差异显著.试验表明供试菌株能显著促进植株生长,强化龙葵吸收土壤中镉的能力.     

无机复合调理剂对污泥脱水性能的影响

针对污泥的固化填埋或建材化利用等后续处置方式,采用FeCl3与生石灰、粉煤灰两种骨架构建体为主要成分的无机复合调理剂对市政污泥进行调理.通过污泥真空抽滤、离心脱水及比阻测定实验,分别确定FeCl3、生石灰、粉煤灰的优化投加量为2.0 g.L-1、20.0 g.L-1、30.0 g.L-1.在优化投加量下,污泥比阻可降到...