天津城市道路灰尘重金属污染特征

Characteristics of heavy metal pollution in urban street dust of Tianjin

以天津城市道路灰尘重金属为研究对象,按照环线分布将天津市中心城区划分为内环以内、内环—中环、中环以外3个区域,总共设置93个采样点。对表层灰尘进行采样收集,预处理后测定样品的理化性质,采用原子吸收光谱仪测定道路灰尘中重金属Cd、Cr、Cu、Ni和Pb的含量,进而分析天津市道路灰尘重金属的含量水平,运用ArcGIS软件中的地统计分析方法内插得出其空间分布特征,通过Pearson相关分析和主成分分析判析重金属来源。研究结果表明:道路灰尘颗粒粒径表现为双峰,主峰对应粒径较小,且为非正态分布,大量小粒径颗粒的存在使重金属含量增高;市区和各环区有机质变异系数较大,道路灰尘中有机质的空间分布差异较大,因而人为因素影响广泛;市区道路灰尘中重金属Cd、Cr、Cu、Ni和Pb的平均含量依次为0.99、121.41、100.62、43.35和61.48 mg·kg-1,分别为天津土壤环境背景值的11.00倍、1.44倍、3.49倍、1.30倍和2.93倍;Cd、Cr和Cu的空间分布差异较大,Ni和Pb的空间分布差异较小;Pearson相关分析表明Pb-有机质(P<0.05),Cu-Ni(P<0.01)和Cr-Cu(P<0.05)之间存在显著正相关关系,主成分分析人为因素的积累贡献率为33.050%,自然因素的积累贡献率为57.315%,因此得出重金属受人为因素影响较大,交通尾气排放和工业污染为天津道路灰尘重金属污染的重要来源,且以多因子复合影响为主。

Dust samples were collected from 93 sites of urban streets in Tianjin for the heavy metals （Cd, Cr, Cu, Ni and Pb） pollution study. Atomic absorption spectrometer was applied for heavy metal content determination, and Kriging analysis of ArcGIS was applied to analyze the spatial distribution of heavy metals in street dust of urban area. Pearson correlative analysis and principal component analysis were used to distinguish the main sources of heavy metals. Results showed that the particle size of road dust presented two peaks distribution, main of the street dust was fine and the particle size was non-normal distribution which led to high contents of heavy metals. The coefficient of variance and the difference in the spatial distribution of organic matter was large because of the influence of intense human activities. The average contents of Cd （0.99 mg·kg-1）, Cr （121.41 mg·kg-1）, Cu （100.62 mg·kg-1）, Ni （43.35 mg·kg-1）, Pb （61.48 mg·kg-1） in street dust of urban area were 11.00 times, 1.44times, 3.49 times, 1.30 times and 2.93 times higher than them of the soil background in Tianjin city respectively. The spatial distribution of Cd, Cr and Cu had large deviation. Pearson correlative analysis indicated that there were significant positive correlation between Cu and Ni （P〈0.01）, Cr and Cu （P〈0.05）, Pb and organic matter （P〈0.05）. Principle component analysis indicated that human activities contributed 33.050% of the heavy metals accumulation in street dust, and nature factors contributed 57.315%. Heavy metals pollution in urban street dust of Tianjin mainly affected by the multi-factors, traffic and industrial activities were the important pollution sources of them.