Dynamic Variation And Accumulation Characteristics Of Heavy Metals In Four Broadleaved Tree Rings In Harbin City

Based on the concentration analyses of Cr, Mn, Fe, Cu, Zn, As, Cd, Hg, and Pb in tree rings of rhizome, diameter at breast height (DBH),1/2and3/4tree height of Phellodendron amurense, Quercus mongolica, Fraxinus mandshurica, and Betula platyphylla, established in Northeast Forestry University’s Urban Forestry Demonstration Research Base in1950s, the radial and axial dynamic concentrations and accumulation characteristics of trace elements in the soil-tree system were studied. The results were showed as follows:Radial concentrations of nine heavy metals in the tree rings basically increased with tree age. The radial concentration of Fe in the period of2000—2007were6.1～18.8times of that in the minimum period except for the3/4tree height; Mn, Cu, Zn were2.3-5.5times except for the concentration of Cu in DBH and3/4tree height rings were1.3～1.9times; Cr, Hg, and Pb were1.3～1.9times except for the concentration of Pb in rhizome and3/4tree height rings were1.0～1.2; As, Cd were only1.0-1.2times.Radial mean concentrations of Cr and Hg in P. amurense, Fe and Cu in F. mandshurica, Mn and As in B. platyphylla were maximum. Fe, Mn and the rest heavy metals were1.7～28.0and1.2-4.5times of those tree species. The ratio of radial mean concentrations of Zn, Cd, and Pb in four species were only1.1～1.9.Axial concentrations of nine heavy metals in rhizome rings were larger than that of DBH in1958and1959—1962. The axial pattern of heavy metals during the period of1963—2007basically showed concave curves of which the minimum concentrations were in DBH or1/2tree height. The axial ratio between the maximum and the minimum concentrations of Mn and Fe; Cr; Cu, Zn, As, Hg; Cd and Pb in the same period were1.1～35.7,1.0～21.9,1.0～3.2, and1.0～1.2, respectively.The migration ratio of nine heavy metals from the rhizome to DBH,1/2and3/4tree height had little difference in four tree species, and the ratio is in the range of1.0～1.8. The mean migration ratio of Mn, Zn in Q. mongolica, Cr, Fe and As, Hg, Pb in B. platyphylla were1.1～2.3,4.0～8.9and1.3～2.1times of those tree species. The ratio of the migration rate of Cu, Cd in four species were only1.1～1.3.The order of the migration rate of nine heavy metals from the rhizome to DBH,1/2and3/4tree height in B. platyphylla, P. amurense, Q. mongolica, and F. mandshurica was as following Fe> Cr> Pb> Mn> As> Cd> Hg> Cu> Zn, As> Mn> Cu> Fe> Zn> Cd> Pb> Hg> Cr, Mn> As> Pb> Cd> Zn> Hg> Cr> Cu> Fe, Mn> Cu> Hg> Zn> Pb> Cr> Fe<As=Cd.The accumulation coefficient of Hg in trees was the highest, then Cd (except F. mandshurica), the order of Pb, Zn, Cu, Mn, As and Cr were varied with the tree species, and Fe was the lowest (except F. mandshurica). Q. mongolica, P. amurense for Hg and Q. mongolica, B. platyphylla were appropriate species for environment phytoremediation contaminated by Hg and Cd, and Q. mongolica was the best.Tree rings of F. mandshurica did not accumulate contamination by As and Cd, which indicated that F. mandshurica was not appropriate for tracing dynamic changes of As and Cd, and it had strong resistance to these two kind of heavy metals.The cumulants of As, Cd in Q. mongolica and B. platyphylla forest, Cr, Fe, Cu, Zn, Hg, Pb in F. mandshurica forest, Mn in B. platyphylla forest were1.5～2.3,1.3～5.8,1.3～14.2times of those species. The order of mean cumulants of nine heavy metals in four plantations was F. mandshurica forest> B. platyphylla forest> Q. mongolica forest> P. amurense forest. The order of total cumulants of nine heavy metal was Fe> Mn> Zn> Cu> Pb> Cr> Hg> Cd=As. The concentrations of heavy metals in tree rings are positively correlated with the one in their soil except for Hg.The concentrations of Fe, Cd and Pb, Cu and Zn in P. amurense, the concentrations of Zn, Cd and Pb, As, Cd and Pb, Mn and Fe in Q. mongolica, Cr, Fe and As, Zn and Cd, Mn, Cu and Zn in B. platyphylla, Cr and Fe, Mn and Fe, Cu and Hg, Fe and Pb in F. mandshurica are significantly positively correlated. The concentrations of Hg in P. amurense and Q. mongolica, Zn in F. mandshurica, Pb in B. platyphylla are negative correlated with the rest heavy metals (except Pb in F. mandshurica).