| 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.
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