研究生知识库

经济发展使人们对于交通的需求也日益增加，道路建设和汽车生产都是必不可少的，除了对于资源的消耗外，汽车生产过程和使用过程都对环境产生了一定的影响。汽车行驶过程中所排放的尾气，刹车片、轴承等的磨损，以及轮胎与地面磨损过程中所产生的颗粒物等均含有大量的重金属，这些重金属（颗粒物）在风和地表径流的作用下会向道路两侧迁移沉降。迄今道路交通过程产生的重金属的分布特征和环境效应的研究还非常有限。 本研究以贵州省的第一条高速公路贵黄公路作为研究对象，贵黄公路自1991年建成使用，二十余年来为贵州省的经济发展作出了很大的贡献。通过研究道路两侧重金属元素Cr、Cd、Cu、Zn和Pb的分布特征以及对环境的危害了解道路的发展对环境的影响。该道路目前虽部分被并入省道，但车流量仍很高，巨大的交通流量所带来的汽车尾气排放、汽车部件磨损颗粒的排放以及轮胎与路面的摩擦所产生的颗粒都会造成道路周围植被和土壤的重金属污染。为避免降雨的影响，研究选择在连续一周无降雨的干燥的天气条件下采样。沿线选择了三个采样点，远离人群居住和工业污染地区，分别采集了路面灰尘、道路两侧土壤以及植物样品，针对样品进行了重金属含量及其他地球化学参数研究。从本研究所获得的主要结论和认识如下： 1.道路两侧所采样品（土壤、灰尘）中重金属含量平均值大小顺序为Zn>Cr>Pb>Cu>Cd。在道路两侧随着距离的增加Zn、Cu和Cr的含量总体呈现先逐渐增加再减少的趋势，Cd和Pb则是随着距离的增加逐渐降低；而在高度上，随着距离地面高度的增加Zn和Cu呈现先增后减的趋势，Cr、Cd和Pb为逐渐增加，污染来源和传输途径可能是控制这些分布特征的主要控制因素。 2.对重金属含量的相关性分析中可知，样品中重金属Cu与Cr、Zn呈正相关；Cr与Pb呈正相关；Cd与Zn呈正相关，与Pb呈负相关。重金属间呈现的正相关关系说明这两种重金属的共同来源占有较高的贡献比例，无相关关系说明重金属来源不是单一的，多重来源和贡献比例的差别都会导致出现不同的结果。从土壤和灰尘样品的富集因子来看均呈现较高的富集，人为源占有很大的比例。 3.从地积累指数以及潜在生态风险评价计算中得知样品中所含的重金属Cr、Zn、Cu、Cd和Pb均对环境存在一定的风险危害，其中Zn的地积累指数达到偏中度污染，而Cd虽然含量不高，但其环境风险响应系数达到30，表明其对环境危害最大，达到了害高的生态风险。虽然除Cd外其他重金属元素对于环境的的危害均属于无危害或是轻危害，但总的重金属生态风险影响仍达到了中度风险。 通过本研究，对道路两侧重金属的分布特征有了一定的认识，并对重金属的排放来源做了初步的解析，为之后的系统研究奠定基础；以及对重金属排放所造成的环境影响进行了估算。

With the rapid economic growth, the demand for transportation is ever increasing. Since the road construction and automobile production are both indispensable, the process of car production and use both exerting impact on environment at some degree in addition to the resource consumption. Heavy metals are found in the exhaust gas emitted by vehicles, the wear of brake pads and bearings, as well as the particles produced in the process of ground wear of tires. And these heavy metals (particulate matter) can migrate and settle on both sides of the road through wind and surface runoff. Until now, to our best knowledge, the distribution characteristics and environmental effects of heavy metals produced during and through road traffic are not well constrainted and remain unclear. This study takes Guihuang Highway, the first expressway in Guizhou Province, as the research object. It has been built and since 1991 and has made great contribution to the economic development of Guizhou province in the past 20 years .By studying the distribution characteristics of heavy metal elements such as Cr, Cd, Cu, Zn and Pb on both sides of the road and their harmfulness to the environment, in order to understand the impact of road development on the environment. Although part of the road has been incorporated into the provincial highway at present, the traffic flow is still very high. The heavy metal pollution of the vegetation and soil around the road can be caused by the exhaust emission of the vehicle caused by the huge traffic flow, the emission of wear particles of automobile parts and the particles generated by the friction between tires and the road surface.To avoid the influence of rainfall, samples were collected in dry weather without rainfall for a consecutive week. Three sampling sites were selected along the route, far away from people's living and industrial pollution areas, and the road dust, soil and plant samples on both sides of the road were collected respectively. The heavy metal content and other geochemical parameters of the samples were studied.The main conclusions derived from the study are as follows: 1.The average content of heavy metal in the samples (soil, dust and plants) collected on both sides of the road increased in an order of Zn>Cr>Pb>Cu>Cd. With the increasing distance outward on both sides, the content of Zn、Cu and Cr showed an overall first gradual increase and then decrease, while Cd and Pb decreased. In terms of height, Zn and Cu tend to increase first and then decrease with the increase of height from the ground, while Cr、Cd and Pb gradually increased. Source contribution and transmission mechanisms might be the main controlling factors for these distribution characteristics. 2.According to the correlation analysis of heavy metal content, Cu is positively correlated with Cr and Zn. Cr was positively correlated with Pb. Cd is positively correlated with Zn and negatively correlated with Pb. The positive correlation between heavy metals indicates that the common sources of these two heavy metals account for a high proportion of contribution. In addition, the lack of correlation indicates that the source of heavy metals is not single, and the difference in multiple sources and contribution ratio will lead to different results. According to the enrichment factors of soil and dust samples, they all show high enrichment, and anthropogenic sources account for a large proportion. 3.Based on the assessment of all index of geoaccumulation and potential ecological risk, the heavy metals investigated here as Cr, Zn, Cu, Cd and Pb would all show certain risks and harms to the environment. Among them, the index of geoaccumulation of Zn reached moderate pollution, the environmental risk response coefficient of Cd reached 30 while the content of Cd is not that high. It stated that Cd was the most harmful to the environment and has reached the highest ecological risk, and Zn would be the second one. Although other heavy metals showed no harm or slight harm index, they implied still a moderate risk. Through this study, we have certain understanding of the distribution characteristics of the two heavy metals on the road, and preliminary analysis of the sources of heavy metals emissions, laying the foundation for the subsequent systematic research, and estimated the environmental impact caused by heavy metals emissions.