经济快速发展区域的城市植被叶面降尘粒径和重金属特征

Particulate size and heavy metal accumulation in foliar dust from urban vegetation in rapidly developing cities

以广东惠州和广州海珠区为例,用粒径分析仪和ICP-AES测定了城市不同功能区植被叶面降尘的粒径和重金属特征.结果表明,两地降尘粒径为对称分布,粒径均小于1mm,60%粒径小于100μm.居住区、清洁区降尘颗粒小于商业交通区、工业区.降尘重金属,尤其Cd、Pb污染严重,惠州和广州降尘含量分别为Cd:6.8～12.8mg.kg-1,8.8～13.0mg.kg-1;Pb:434～512mg.kg-1,584～1182mg.kg-1.不同功能区重金属含量差异显著,污染水平递减顺序为:工业区、商业交通区、居住区、清洁对照区.降尘中重金属元素富集因子为18～746,反映其主要源于工业污染、交通排放、建筑物腐蚀剥落等人为源.叶面降尘与路尘以及叶面降尘之间大部分重金属显著相关,表明降尘和路尘重金属均来自外源输入.

The particulate size and total concentrations of heavy metals （HMs） in foliar dusts from urban vegetation in Huizhou （HZ） city and Halzhu district of Guangzhou （ GZ ） , Guangdong Province were determined with a Particle Sizer and ICP-AES. It was found that the particulate size was distributed symmetrically, with a range less than 1 mm and more than 60% under 100 μm. The dust particulate size in residential areas （RA） and control areas （CA） was finer than in commercial and traffic areas （CTA） , or industrial areas （IA）. The heavy metal contamination in foliar dust was serious; especially Cd and Pb. Concentrations for Cd in HZ ranged 6.8 ～ 12.8 mg· kg^- 1 and 8.8 ～ 13.0 mg· kg^ -1 in GZ. For Pb, the concentrations were 434 ～ 512 mg·kg^-1 in HZ and 584 ～1182 mg·kg^-1 in GZ. The overall pollution index in the different areas decreased in the order IA 〉 CTA 〉 RA 〉 CA, and the differences were statistically Significant. The enrichment factors ranged from 18 to 746, which indicated that the foliar heavy metals could be attributed to industrial pollution, vehicle emission, corrosion of building materials, and other anthropogenic sources. The heavy metals in the foliar dusts were highly correlated with those of road dust, showing that both dusts originated from extraneous source input.