【作者】 刘玉燕；

【导师】 刘敏； 许世远；

【作者基本信息】 华东师范大学 ， 自然地理学， 2009， 博士

【摘要】 长期以来,人们对铂(platinum,即Pt)及铂族元素(the platinum group metals,即PGEs)的毒性并非十分明确,一直认为它们是无毒的,但近几年的研究表明,PGEs及它们的化合物是一类高发生率的致敏物,部分PGEs化合物还具有致癌效应,能以很低的含量对微生物产生影响。为了治理汽车尾气污染,Pt、Pd、Rh被作为催化剂广泛用于汽车尾气催化转化器(VehicleExhaust Catalysts,即VECs)装置。虽然VECs在净化空气方面功不可没,但在净化尾气的同时,PGEs颗粒物随尾气排放出来,成为一种新的环境污染源。机动车PGEs排放带来的环境问题已成为近年来欧美发达国家十分关心的问题,而我国对此方面的研究还涉及较少。为此,论文选择上海市为主要研究区,以PGEs为研究对象,分析和探讨了上海市道路灰尘PGEs时空累积特征、建立了城市典型道路(城市快速干线、城市主干道、城市次干道、郊区高速、郊区公路)灰尘PGEs的分布模型,揭示PGEs地表累积过程、迁移转化过程及影响机制,对道路环境PGEs进行人为污染程度评价,提出PGEs污染的防治对策。论文取得的主要认识与结论如下:上海市内环—中环区间的道路灰尘PGEs含量最高,从此区域分别往城区内和城区外,PGEs含量逐渐降低,至郊区(外环-郊环)道路,灰尘PGEs含量达到最低;除次干道Pt浓度高于主干道外,其他类型道路PGEs平均浓度水平均表现为:快速路(包括环线)＞主干道＞次干道＞高速公路＞郊区公路;车流量、车速、车辆行驶特征及高污染车辆限行范围对道路灰尘PGEs含量影响深刻。上海市道路灰尘PGEs比例与Ely等的研究结论有不符现象,VECs不同发展阶段中PGEs比例结构发生改变是主要致因;PGEs间相关性很好,说明道路灰尘PGEs来源相同,且均来源于汽车VECs;同为交通污染排放的元素,Cr与PGEs的相关性很好,Cu与PGEs之间有一定相关性,Zn只与Pt有相关性,而Pb与PGEs都没有相关性,Pb、Zn为汽车催化剂毒物是主要原因。灰尘和土壤PGEs含量表现出明显的季节变化:PGEs含量在春夏季节低,秋冬季节高;降雨量对灰尘和土壤PGEs的季节变化起了重要的影响作用;土壤PGEs受季节风向变化的影响很小,郊区道路灰尘PGEs受季节风向变化影响明显,而市区道路灰尘PGEs受季节风向变化影响微弱,市区高大建筑物减弱了风速是主要致因;2007年上海市道路灰尘PGEs高于2003年,Rh、Pd、Pt年均增长率为11%-19%,与上海市机动车保有量的年均增长状况相吻合。如以道路1.5-1.6 km长度为单位,主干道、次干道及快速路灰尘PGEs的分布呈波浪型;两端为路口的郊区公路,灰尘PGEs的分布呈“(?)”半圆弧型;一端为收费口的高速公路,灰尘PGEs分布呈“(?)”折线型;车辆行驶特征的差异是造成典型道路PGEs分布模式不同的主要原因;主干道、次干道及快速路路口PGEs含量不一定高于远离路口的位置,频繁的怠速和加减速使得远离路口的地方也常出现怠速是主要原因;高速公路及郊区公路路口(或收费口)PGEs含量往往高于远离路口处;高速公路及郊区公路车流量都较大,但灰尘PGEs含量并不高,车流中许多车辆未安装VECs,PGEs总排放量小是主要原因。大风和降雨对PGEs的增长具有明显的抑制作用;连续降雨后,PGEs浓度与负荷达到下限值,继续降雨,PGEs浓度及负荷不再降低;连续干燥无大风天气会使PGEs浓度与负荷达到上限值,若天气继续保持无雨无大风,两值不会再上升,变化趋于和缓;PGEs累积过程符合Sigmoidal曲线,与重金属等其他污染物的累积过程相似。道路灰尘PGEs在125-63μm的粒径部分含量最高;其次是＜63μm的粒径部分,1000-500μm粒径部分占总量的比值最低;Rh、Pd、Pt粒径效应很明显,且完全相同,其中,Pd和Pt的粒径效应要更明显于Rh;国外很多研究都假定PGEs含量在＜63μm的粒径部分含量最高,由此选用＜63μm的粒径部分含量进行PGEs富集率及其他研究,因此,这些研究很可能都低估了环境中PGEs的含量水平。在灰尘-雨水口-受纳水体的迁移路径中,PGEs含量表现为:道路灰尘＞雨水口沉积物＞河流沉积物,Cd、Cu、Pb与PGEs表现出相同的迁移特征;Pd的可溶性强于Rh和Pt,导致雨水口Pd含量降低,Pt/Pd升高;河流沉积物中Pt/Pd降低,河流接纳了含Pd量较大的污水厂污水可能是主要原因。在灰尘-土壤-植物的迁移路径中,PGEs含量表现为:灰尘＞土壤＞植物;路边植物对道路灰尘PGEs吸附能力表现为Pt＞Pd＞Rh,其中,对Pt、Pd吸附作用非常明显,而对Rh几乎不存在吸附作用;路边植物对土壤PGEs的吸收能力为Pd＞Rh＞Pt,Pd的生物有效性最大;土壤剖面中,Rh与Pd分布规律很相似,都表现为随深度增加,含量逐渐降低的特征,而Pt最高值并没有出现在最表层,而是出现在距地面2-5 cm的位置。河流因有其他来源PGEs汇入,导致河流沉积物PGEs比例不同于其它环境介质。除此之外,在整个城市环境的迁移循环过程中,PGEs比例比较稳定,所有介质PGEs比例范围都很接近或出现重合现象。上海市各种介质中(除河流沉积物外)Pt/Pd和Pt/Rh均低于国外同类研究,但却与2000—2002年VEC中PGEs比例很接近甚至重合,VECs类型变化及使用历史是决定因素。上海市道路灰尘Rh、Pd、Pt平均含量分别为27.68 ng/g、107.1 6 ng/g、34.59 ng/g,分别是是参照点的18.28(Rh)、11.06(Pd)、65.54(Pt)倍,超过地壳丰度值两个数量级以上和其他国家的城市相比,Pd含量处于较高水平,而Pt与Rh含量处于较低水平;Rh、Pd、Pt平均CER值分别为17、＞40、＞40水平,为显著人为影响、非常强烈人为影响、非常强烈人为影响。路边土壤Rh、Pd、Pt平均含量分别为8.84 ng/g、29.92 ng/g、12.82 ng/g,是参照点的5.61(Rh)、9.62(Pd)、20.55(Pt)倍,超过地壳丰度值两个数量级以上;和其他国家的城市相比,Pd含量处于较高水平,Rh含量水平居中,而Pt处于较低水平;Rh、Pd、Pt平均CER值分别为6、9、20,为显著人为影响、显著人为影响及非常强烈人为影响。路边植物Rh、Pd、Pt平均含量分别为2.82 ng/g、6.32 ng/g、0.65 ng/g,均高于参照点植物;与同类研究比较,Rh和Pd的含量较高,而Pt含量几乎达到了最低水平。道路环境PGEs主要防治对策有:通过用Pd代替Rh和Pt、采用非贵金属催化剂等手段调整TWCs的组成,从源头防治PGEs污染;通过限速、限制最长怠速时间、限制私家车、扩大公共运输、积极发展轨道交通、引导自行车交通的出行、大力推行智能交通系统等手段倡导绿色交通,实施有效的交通控制与管理,降低PGEs污染。更多还原

【Abstract】 For a long time,platinum and platinum group metals were considered innocuous,but the latter study showed a high prevalence of sensitization to PGE.Certain Pt compounds were also known to be cytotoxic,and have mutagenic and carcinogenic effects and have some effects on microorganisms at very low concentrations.In order to Control the pollution of vehicle exhaust gas, Pt,Pd,Rh were widely used in Vehicle Exhaust Catalysts.PGEs purified vehicle exhaust gas but had become new environmental pollution source.Environment problems caused by emissions of PGEs were evidently concerned by developed countries in Europe and the United States in recent years,while the study of environment medium PGEs were also few in china.The paper chose Shanghai as the main research area,took PGEs as research object,analyzed space-time cumulation rule,established distributing model of typical road(trunk road;secondary road;elevated road;expressway;suburb road),opened accumulation and transfer process,made the appraisal related environmental effect and proposed the countermeasure related PGEs pollution.The main conclusion of the paper as follows:Highest pollution occurred between interior ring and medium ring,while lowest values were presented from outer ring to suburb ring.Except Pt of trunk road,PGEs concentrations of different types road showed:elevated road＞trunk road＞secondary road＞expressway＞suburb road. Vehicle flow,vehicle speed and driving characteristics as well as limit range of high pollution vehicle had profound Influence on PGEs concentrations of road dust.Meanwhile,the average PGEs ratios of road dust samples from Shanghai were inconsistent with Ely’s result.These differences were contributed by the change of VECs type.Pd,Pt and Rh showed strongly positive correlation,Preliminary results for the anthropogenic Rh,Pd and Pt emissions in Shanghai,based on dust samples,indicated a common traffic-related source of these metals.PGEs in these samples were not correlated with Pb and only Pt were correlated with Zn, though positive correlations with Cr and Cu were evident.This lack of statistically significant relationships can be explained that Pb and Zn are known as poisoning agents for autocatalysts.PGEs concentrations in dust and soil had obvious seasonal change that were lower in spring and summer,higher in autumn and winter,and rainfall were main effect factors,PGEs in the soil received the influence of the season wind was small,PGEs in the dust of rural road received the influence of the season wind was obvious,but PGEs in the dust of urban road received the influence was weak,because the big building in the urban can weaken the wind speed.The comparison of levels of PGE between 2003 and 2007 showed that PGEs concentrations in road dust had increased over the period of 4 years with 11%-19%of average annual growth rate because of the rapid increase in the number of vehicles in Shanghai.If we took 1.5-1.6 km as length unit,the distributing model of PGEs in trunk road,secondary road and elevated road showed wavy type,suburb road showed semi-circle type,elevated road showed polygonal line type.The distributing model of PGEs had difference because of dissimilarity of vehicle run character.The content of PGEs in trunk road,secondary road and elevated road was possible low,the main reason was the vehicles decelerates frequently at the place away from the junction.The content of PGEs in elevated road,suburb road was often higher, the main reason was many vehicles had not installed the VECs,the total emissions of PGEs were small.Gale and precipitation caused the short-term change of PGEs.The concentrations and mass loading of PGEs touched bottom after durative precipitation,and came to head after durative weather without gale and precipitation,but both concentrations and mass loading of PGEs were unable to vary without limit.PGEs accumulation process accorded with Sigmoidal curve and conformed to heavy metal accumulation process.The grain size effect of PGEs were similar,and Pd,Pt were more obvious than Rh.A major finding of this study was that in the finest grain size fraction sampled(＜63μm)had lower concentrations.So these data suggest that autocatalyst PGEs flux estimates into the environment will be significantly underestimated if only a fine grain size fraction is analyzed.PGEs concentrations in migration path of dust-gully-receiving water showed:road dust＞gully sediment＞river sediment,and migration Characteristics of PGEs were similar to Cd,Cu,Pb. Pd concentration in gully decreased,and value of Pt/Pd increased because of solubility of Pd was stronger than Rh and Pt.Value of Pt/Pd in river sediment decreased by reason of admission of river for Pd from wastewater.The concentrations of PGEs in dust were higher than that in soil and in plant.Meanwhile,PGEs concentrations in plant were lower than that in dust,and closed to that of soil.The implementation of the automobile emission standard only in central city of Shanghai didn’t cause obvious correlation between PGEs in Multimedia and traffic volume.The plant adsorption capacity for PGEs of road dust showed:Pt＞Pd＞Rh,while its absorptive capacity for PGEs of soil was:Pd＞Rh＞Pt.PGEs ratios in Multimedia were not completely coincident but in the range of PGEs ratios of road dust in Shanghai,which indicated a common traffic-related source of these metals.In soil section,distributing rules of PGEs were same except Pt,which showed concentration gradually decreased along with increase of depth..PGEs ratio of river sediment differed from others environment medium because of admitted PGEs of other source. PGEs ratio in course of transfer and circulation were steady.The value of Pt/Pd and Pt/Rh in multi-medium were under same study in overseas,but were the same with PGEs ratio of VECs in 2000—2002 year.The PGEs concentrations in road dust were as following:27.68 ng/g(Rh),107.16 ng/g(Pd), 34.59 ng/g(Pt),higher by two orders of magnitude than the crustal abundance.Rh,Pd and Pt increased 18.28,11.06 and 65.54 times,compared to reference point,respectively.Pd concentrations were in the higher level,Rh and Pt concentrations were lower,in comparison with International cities.Average CER of Rh,Pd、Pt were 17,＞40,＞40,which respectively reached significantly artificial effect,very strongly artificial effect and very strongly artificial effect.The PGEs concentrations in roadside soil were as following:8.84 ng/g(Rh),29.92 ng/g(Pd),12.82 ng/g(Pt),higher by two orders of magnitude than the crustal abundance.Rh,Pd and Pt increased 5.61,9.62 and 20.55times,compared to reference point,respectively.Pd concentrations were in the higher level,Rh concentrations were in the midle level and Pt concentrations were lower,in comparison with International cities.Average CER of Rh,Pd,Pt were 6,9,20,which respectively reached significantly artificial effect,significantly artificial effect and very strongly artificial effect.The PGEs concentrations in roadside plant were as following:2.82 ng/g(Rh),6.32 ng/g(Pd),0.65 ng/g(Pt),higher than reference point.Rh and Pd concentrations were in the higher level,Pt concentrations were nearly in lowest,in comparison with international similar research work..Finally,it put forward the management practice of PGEs pollution in Shanghai city which based on the figure of Shanghai city and experimental results.Controling PGEs pollution from source was replacing Rh and Pt by Pd,replacing PGEs by non-noble metal catalyst. Other countermeasures were enlarging public transportation,developing actively rail transit and guiding bicycle going by speed limiting,idle speed time limiting and private cars limiting, Advocating green transportation by carrying out Intelligent Transportation System etc.更多还原