Study Of Distribution And Assessment On Heavy Metals Of Greenland Soil In Baoding City

Urban greenland as one of important urban land-use way,it keeps the closest contact with humans.Heavy metals in the urban greenland harm the lives and the health of man seriously through dusts or direct contacts,and the more serious thing is that this kind of contamination is secluded,long-term,aggregated in surface,irreversible and great harmful.For this purpose , soil conditions of Baoding greenland were investigated.Conventional methods have been used to analyze the pH and organic matter contents of soils from different types of greenland.National standard methods have been used to determine the contents and distribution characteristics of Cu,Zn,Ni,Cr,Pb,Cd in different greenlands,different vegetation and different levels of soil.The present pollution degree of heavy metals was evaluated by the contamination index of single item and comprehensive item,and the potential ecological risk of heavy metals was evaluated by the potential ecological risk index,in order that the results could provide important theoretical basis to the treatment of the heavy metal contamination in soils,the main results were summarized as followed:(1) The soil of Baoding greenlands was strongly alkaline (pH=8.53),the contents of organic matter were in the three-tier level of national standards,and the contents in the shelter greenland and the road greenland were significantly higher than that in the accessory greenland,the production greenland and the park greenland.(2) Correlation analysis showed that pH value of soil was significantly negatively correlated with the content of Zn,and was significantly positively correlated with the content of Cr;the contents between organic matter and Cu,Zn,Pb,Cd were a positive correlation;and the correlation among the four elements(Cu,Zn,Pb,Cd) were significant with each other.(3) The contamination of Cd was the most serious in Baoding greenlands,the next in order being Cu,Zn and Ni,and that of Cr and Pb was the lest.(4) The ranking order of the heavy metal contamination in different types of greenland was the road greenland>the shelter greenland>the park greenland>the accessory greenland>the production greenland.The potential ecological risk index of heavy metals in road greenland (RI=212.63) and shelter greenland (RI=191.12) have both reached a medium level,and that in park greenland (RI=91.36),accessory greenland (RI=80.19) and production greenland (RI=66.00) indicated slight ecological risk.(5) The contents of heavy metals in the soils under different vegetation showed that: in accessory greenland and road greenland,the contents of Cu,Zn,Pb,Cd under the arbores and bare land were kept a higher level,and which were kept a lower level under the shrubs and greenswards,the case in park greenland was reverse,the contents of Cu,Zn,Ni,Pb,Cd under the bare land were the lowest,and under the shrubs and arbores,the contents were relatively higher.(6) The distribution characteristics of heavy metal contents in different levels of soil showed that:the contents of Cu,Zn,Cr,Pb,Cd in the surface of soil were the highest and with the increase in depth,the contents were gradually reduced;the case of Ni was reverse,the content was the least in the surface of soil,and with the increase in depth,the content was gradually increased.The contents of Cu,Zn,Pb,Cd in the dust collected from the surface of leaves were much higher than that in the soils under the vegetation.