道路灰尘中重金属的污染特征及其与道路等级的关系——以北京和郑州为例

Pollution characteristics of heavy metals in road dust and its relationship with road levels: Taking Beijing and Zhengzhou as examples

为了探究交通活动对道路灰尘重金属(Ni、Cu、Zn、Mn、Co、Cr、As、Ag、Cd、Pb)空间分布及人体健康风险的影响,本研究分别采集北京市和郑州市主干道、次干道、支路、交通枢纽和公园道路的灰尘样品共64个,进而运用地积累指数法对其进行污染评价,并运用美国EPA健康风险评估模型进行人体暴露评估和健康风险评价.结果表明,北京市道路灰尘中重金属浓度的高低顺序依次为Zn>Mn>Cr>Ni>Pb>Cu>As>Co>Ag>Cd,郑州市道路灰尘中重金属浓度的高低顺序依次为Zn>Mn>As>Cr>Pb>Ni>Cu>Co>Cd>Ag.北京市道路灰尘中Ag、Cd污染水平较高,而郑州市道路灰尘中Ag、Cd、As浓度明显高于河南省土壤元素背景值.总体而言,郑州市支路灰尘中重金属的浓度最高,次干道其次,主干道浓度最低;而北京市不同规格道路灰尘中重金属的浓度并无明显规律,这与城市发展水平和交通密度的空间分布有直接关系.进一步对比交通枢纽与公园道路灰尘样品发现,道路灰尘中重金属元素可以分为两类,一类受交通活动影响较大,包括Ni、Cu、Zn、Cr、Pb、Cd 6种元素,其在交通枢纽与公园道路灰尘样品中污染水平存在显著差异.另一类受交通影响较小,包括Mn、Co、Ag、As 4种元素,其在交通枢纽和公园道路灰尘中的浓度相差不大.

In order to explore the spatial distribution of heavy metals (Ni, Cu, Zn, Mn, Co, Cr, As, Ag,Cd,Pb） in urban road dust and the influence of traffic activities, 64 dust samples were collected from the main roads, collector streets, bypasses, traffic intersections and park paths of Beijing and Zhengzhou, China. Geo-accumulation index was used to evaluate the contamination level of heavy metals, and human health risk assessment was conducted using the USEPA model. The results showed that the concentrations of heavy metals in road dust decreased in the following order： Zn 〉 Mn 〉 Cr 〉 Ni 〉 Pb 〉 Cu 〉 As 〉 Co 〉 Ag〉Cd for Beijing, and for Zhengzhou the order was： Zn 〉 Mn 〉 As 〉 Cr 〉 Pb 〉 Ni 〉 Cu 〉 Co 〉 Cd 〉 Ag. The contamination levels of Ag and Cd in road dust from Beijing were much higher than the other elements, and that of As, Ag and Cd in road dust from Zhengzhou were remarkablely higher. Generally, the concentrations of heavy metals in road dust from bypasses were tbe highest, followed by collector streets, and the lowest concentrations were found for the main roads in Zhengzhou. However, there was no obvious variation patterns for heavy metals in dust from different levels of roads in Beijing. This might be due to the differences in urbanization level and spatial distribution of traffic activities between the two cities. By comparing heavy metals in dust from traffic intersections with those from park paths, it＇s found that heavy metals could be divided into two categories. In one category the heavy metuls including Ni, Cu, Zn, Cr, Pb and Cd might be influenced significantly by traffic activities. The spatial distribution of other four elements including Mn,Co,Ag and As was not influenced obviously by road level.