上海郊区小城镇街道灰尘理化性质及重金属时空分布特征

TEMPORAL AND SPATIAL DISTRIBUTION OF PHYSICAL-CHEMICAL PROPERTIES AND HEAVY METALS IN STREET DUST OF SHANGHAI SUBURBAN SMALL TOWNS

为了解上海郊区不同类型小城镇街道灰尘的基本理化性质和重金属的时空分布特征,分别于2003年7月(夏季)和2004年4月(春季)在枫泾镇、松江新城和朱家角镇采集街道灰尘样品共计90个,分析了样品的pH、粒度、有机质和重金属的含量。结果表明:3个小城镇街道灰尘的理化性质和重金属时空分布特征具有较好的一致性,pH值为8.41～11.37,呈碱性;有机质的平均含量为34.13g/kg;粒度主要呈单峰和双峰分布特征,粒径平均值为173.6μm,以砂粒为主。各重金属的平均含量均高于上海市土壤环境背景值。Cr和Ni含量夏季高于春季,但区域分异不显著。城镇中心区域和镇级公路Cd、Cu、Pb和Zn含量明显大于乡村。Cr-Ni,Cu-Pb-Zn,Fe-Mn之间具有极显著的相关性,有机质是街道灰尘重金属的重要载体。

Heavy metal concentrations and basic properties including pH values,particle size and content of organic matter were analyzed in a total of 90 street dust samples collected in July,2003 and April,2004 from three small towns in Shanghai suburban area.The results showed that the three different small towns presented similar temporal and spatial distribution characteristic for pH,particle size and organic matter as well as heavy metals.The pH values of the street dust were 8.41~11.37,which assume alkaline.The average content of organic matter in street dust was 34.13 g/kg.The street dust had coarser particle size than soil around,and the average particle size was 173.6 μm.Sand grain was the main particles in street dust with the average volume fraction 70%.The particle size of street dust mainly showed unimodal or bimodal distribution spectrum,where the first mode was 250~300 μm,and the second was 30~50 μm.The average heavy metal concentrations were much higher than the soil background values of Shanghai city,but lower than those of Shanghai urban area.Cr and Ni concentrations showed significant seasonal change,which were higher in July（summer） and lower in April（spring）.Higher concentrations of Cd,Cu,Pb and Zn were distributed mainly in the towns residential area,commercial area and scenic area as well as the township roads than in rural area.The prominent correlation between Cr and Ni,Cu and Pb,Cu and Zn,Pb and Zn,Fe and Mn might suggest the two possible sources of heavy metals in street dust;one might be related to vehicle transportation,and the other might be natural source such as soil.Moreover,significant correlation between organic matter and heavy metals indicated that organic matter was the carrier of heavy metals in street dust.