Comparison of the Contents of Pd,Cd,Cl and S in the Leaves of 18 Greening Tree Species

In order to reveal the differences in the capabilities of the greening tree leaves to absorb atmospheric pollutants,such as lead,cadmium,chlorine,and sulfur,18 greening tree species occurring in Xinxiang,Henan Province were selected for the study.The results indicated that depending on the types of pollutants and tree species,the trees tested could absorb atmospheric pollutants to different extents.Differences in the capabilities of absorbing 4pollution elements were significant,and generally,the capacities for the trees to accumulate chlorine and sulfur were higher than lead and cadmium.Higher lead contents were found in the leaves of Eriobotryajaponica,Ulmus pumila and Populus deltoides,while E.japonica,Magnolia grandiflora,Paulowniaand Populus deltoides demonstrated high cadmium accumulation capability,and;Euonymus alatus,Buxus megistophylla,Populus deltoides,U.pumilaand Ailanthus altissima could enrich chlorine;and Populus deltoides,E.alatus,Paulownia and Viburnum awabuki were found to enrich sulfur.Tree species tested were grouped into three categories by subordinate function based on their capabilities to absorb pollutants.Populus deltoides and E.japonica were in the first category,the second category included E.alatus,B.megistophylla,Paulownia,M.grandiflora,U.pumilaand Koelreuteriapaniculata.Ginkgo biloba,V.awabuki,A.altissima,Platanus hispanica,Broussonetia papyrifera,Acer palmatum,Pittosporum tobira,Fraxinus chinensis,Sophora japonica and Yucca gloriosa were classified to the third category.