澳门特别行政区土壤自然消减能力与污染背景

Natural attenuation capacity and urban background contamination in soil in Macao

澳门是我国人口密度最大的城市.选择澳门特别行政区不同功能区绿地土壤为研究对象,首先,通过野外布点采样,调查分析了表层土壤中9种重金属元素(Cr、Ni、Cu、Cd、Pb、Cr、Zn、As、Hg)和16种优先控制多环芳烃(PAHs)的分布特征;其次,利用累积频率分布曲线法估算了土壤重金属和PAHs的土壤污染背景;最后,基于土壤物理、化学性质,利用熵权法与改进的EPX模型对土壤自然消减能力进行定量评估,并在城市土壤自然消减能力的格局特征及其影响因素的分析中纳入城市土壤污染背景的分析.结果表明:澳门特别行政区土壤中Cu、Cd、Pb和Zn 4种重金属的累积受到人为干扰的显著影响,其中,Cd、Pb和Zn的土壤污染背景高于广东省土壤背景值,成土母质来源是决定澳门城市土壤中重金属元素分布特征的主要影响因素;由于受到人为干扰的影响,商住区和交通区土壤PAHs高污染背景样点数量多于其他功能区,并且两类功能区中高环多环芳烃(HMW PAHs)污染背景也较高;澳门半岛的土壤自然消减能力高于离岛区域,不同功能区土壤自然消减能力由大到小依次为:商住区>交通区>公园>保护区>海岸带;重金属污染背景与土壤自然消减能力无显著的相关关系(p>0.05),受到人类活动影响较大的8种PAHs(Nap、Acy、BaA、Chry、BbF、BaP、InP、BghiP)污染背景与土壤自然消减能力呈显著正相关(p<0.05).因此,在城市环境管理过程中,通过改良土壤理化性质等措施能有效改善城市土壤环境质量,提高土壤自然消减能力,增加土壤对污染物的环境容量.

Macao is a peninsula city with the densest population in China.The spatial distribution characteristics of 9 heavy metals,namely,Co,Ni,Cu,Cd,Pb,Cr,Zn,As,Hg and 16 priority control polycyclic aromatic hydrocarbons(PAHs)in soil of the green lands of different functional areas in Macao were investigated.The cumulative frequency distribution curve method was used to estimate the background contamination of heavy metals and PAHs.Based on the physical and chemical properties of the soil,the natural attenuation capacity of urban soil in Macao was quantitatively evaluated by the entropy weight method and the improved EPX model.And the background contamination of urban soil was included in the analysis of the spatial pattern of the natural attenuation capacity of urban soil as well as the impacting factors.The results showed that the accumulation of Cu,Cd,Pb and Zn in soil of Macao was significantly affected by human activities.The background contamination of elements Cd,Pb and Zn were higher than the corresponding natural backgrounds of soil in Guangdong Province.It was suggested that sources of heavy metals came from soil parent materials determined their spatial distribution in soil of Macao.In the soil of commercial and residential and traffic areas,the amounts of samples with high background contamination of total PAHs as well as HMW PAHs were significantly more than those in the other functional areas due to strong human disturbance.The soil natural attenuation capacity of the Macao Peninsula was higher than that of the outlying islands,and its order of different functional areas was as following:commercial and residential areas>traffic areas>parks>protected areas>coastal zones.There was no significant correlation between the background contamination of heavy metal and the natural attenuation capacity in soil(p>0.05),while there was a significantly positive correlation between the background contamination of eight PAHs greatly affected by human activities(Nap,Acy,BaA,Chry,BbF,BaP,InP,BghiP)and the natural attenuation capacity(p<0.05).Therefore,measures improving the physical and chemical properties of soil can effectively elevate the environmental quality of urban soil through increasing the natural attenuation capacity of soil during urban environmental management,and thus help to increase the environmental capacity to contaminants in urban soil.