典型行业环境地表灰尘重金属污染比较研究

随着工业化和城市化进程的推进,行业环境重金属污染日益受到关注。选取北京市10个典型行业地表环境灰尘为研究对象,分析了灰尘不同粒径分布和Pb、Cr、Cu、Zn、Ni浓度及贡献率,并采用单因素污染指数和综合污染指数法评估了重金属在不同行业地表环境的污染水平。结果表明:批发行业、工业、餐饮业和交通运输业综合污染水平较高,文化体育业和教育行业综合污染水平最低。     

Prediction of dust cloud minimum ignition energy for organic dusts from modified hartmann tube data

The modified Hartmann tube apparatus is recognized to give realistic or safe indications of dust explosion violence. Evidence is presented that results from this apparatus can also be used to indicate minimum ignition energy. Published data show a correlation between minimum ignition energy and minimum explosible concentration, which is refined by also taking into account explosive violence. An empirical model has been derived, relating minimum ignition energy to minimum explosible concentration and explosive violence. The model allows estimation of probabilities of minimum ignition energy falling below specified values, such as those recognized as of practical importance by the relevant British Standard. A limited test of the model suggests that it can be applied to modified Hartmann tube data. It is anticipated that the model will be valuable as a screening tool, especially in the early stages of development of a project.     

Heavy Metal Contamination and Distribution in the Urban Environment of Guangzhou, SE China

Ever-increasing heavy metal accumulation in the urban environment of Guangzhou, the largest light industrial production base and one of the most rapidly developing cities in China, poses a serious threat to environment as well as to human health in the region. As a sink or source, urban deposits are good indicators of the level and extent of heavy metal accumulation in the surface environment. The aim of this preliminary study was to examine the distribution of heavy metal contamination in the urban environment of Guangzhou. It was based on a systematic sampling of road dusts and corresponding gully sediments along major roads running mainly through commercial and residential to industrial districts of the city. In addition to road dusts and gully sediments, ceiling dusts from the Pearl River Tunnel were also collected to characterize anthropogenic emissions dominated by traffic-related activities. In general, the level of Cd, Cu, Pb and Zn contaminations were more severe on the industrialized side of Guangzhou than on the western side where heavy traffic and industrial activities were limited. The primary determinants of the level of heavy metal contamination and the distribution of this contamination in the urban environment of Guangzhou were the site-specific conditions of its urban setting, particularly the types of industries, the nature of the traffic flow, sample residence times and variations in grain size of the particulate contaminants. This study highlights the complexity of the urban system and indicates that in just such a system individual urban components should be interlinked to assess the long-term environmental and health effects of heavy metal contamination. Among the heavy metals tested – Cd, Cu, Pb and Zn – the level of Zn contamination was the most severe and widespread, and thus requires immediate attention.     

Influence of inert materials on the self-ignition of flammable dusts

Flammable solid bulk materials, including dusts, often undergo spontaneous combustion and the spread of reaction fronts. By addition of inert substances, the ignition and combustion behavior can be influenced. In a series of experiments different types of coal were mixed with inert powders to study the effect of the composition on the self-ignition temperature and on the formal kinetic parameters.Hot storage tests as well as simultaneous-thermal analysis were used as experimental techniques with the latter being coupled to FTIR measurements to analyze the composition of gaseous reaction products.All conducted hot storage experiments led to the conclusion that the self-ignition temperature was increased by admixing inert material if the decomposition temperature of the inert matter was higher than the self-ignition temperature of the combustible component at the sample characteristic length. If (exothermic) decomposition of the inert material occurred before a noticeable growth of reaction rate of the combustible material, even a reduction in the self-ignition temperature could be observed. In addition, significantly higher maximum reaction temperatures were observed for the mixtures than for the combustible material alone.     

矿区家庭灰尘中重金属污染及其潜在生态风险

为进一步了解我国西南某矿区周边家庭灰尘中重金属的污染水平和潜在生态风险,选取西南某矿区周边3个村庄(A村、B村和C村)的家庭作为研究区域,分析了102个家庭灰尘样品中Cd、Cr、Pb、As、Hg 5种重金属的含量水平及其分布特征,并采用潜在生态危害指数法(RI)进行生态风险评价.结果表明,西南某矿区周边3个村庄家庭灰尘中重金属的含量水平从高到底的顺序为:w(Pb)>w(Cr)>w(Cd)>w(As)>w(Hg).Cd、Pb、Hg在不同家庭灰尘中均有不同程度的累积,其中Cd的累积程度最为严重,最高累积系数为226.30,其次为Pb和Hg;Cr和As在不同家庭灰尘中累积系数均小于1.分别对3个村庄家庭灰尘中重金属进行相关分析,结果表明:A村家庭灰尘中Cd和Pb、Cd和As、Cr和Hg、Pb和As均具有较好的相关性;B村家庭灰尘中Cd和Pb、Cd和Hg具有较好的相关性;C村家庭灰尘中各元素均不存在显著相关性.主成分分析结果表明,研究区域家庭灰尘中Cd、Pb和Hg主要来源于室外环境,包括周边铅锌矿采选和冶炼及汽车尾气排放等.潜在生态风险评价显示:A村、B村和C村家庭灰尘中重金属的综合潜在生态危害均达到了极强生态危害水平.     

宝鸡市街尘中As和Hg含量及其环境风险评价

利用原子荧光分光光度计对宝鸡市38个街尘样品进行分析测试,以研究街尘中As和Hg含量的水平及其空间分布特征,并与中国土壤及其他城市街尘中的含量进行对比.结果表明:宝鸡市街尘中w(As)为8.985～42.822 　μg/g,平均值为19.764 　μg/g,约为中国土壤元素背景值(11.2 　μg/g)的1.8倍,是其他城市街尘w(As)均值的2～4倍;w(Hg)为0.483～2.318 　μg/g,平均值为1.112 μg/g,约为中国土壤元素背景值(0.065 　μg/g)的17.1倍,为其他城市街尘w(Hg)均值的10倍.工业区街尘中w(As)相对较高,商业区街尘中w(Hg)相对较高.利用污染指数法和地积累指数法对宝鸡市街尘中As和Hg的环境风险进行评价,结果表明:宝鸡市街尘中As的污染指数平均值为1.765,地积累指数平均值为0.144,存在轻度的污染;Hg的污染指数平均值为17.106,地积累指数平均值为3.425,呈现出偏重污染.