| According to the characteristics and current situation of heavy metal pollution in the soil,based on the adsorption function of plants and the characteristics of heavy metal contaminated soil,the heavy metal migration and accumulation was studied.Using the field survey method combined with seedling planting experiment,carried out the following research contents:(1)to carry out quantitative analysis on pollution degree of soil heavy metals,determine the main types of metal pollutants;(2)the quantitative analysis on the accumulation ability of Larix gmelinii;(3)to carry out seedlings planting test,comparative analysis of heavy metal adsorption capacity of different growth stages of L.gmelinii and different tree species.The following results were obtained:(1)The distribution of the contents of the six kinds of heavy metals in the soil was not obvious,which indicates that the situation of heavy metal pollution in the forest soil was very complex in the experimental area,which needs to be further studied.The highest of the average content of six heavy metals in the soil was Zn,the lowest was Cr.The contents of Cr,Cu,Ni,Pb and Zn were much higher than the background value,the content of Cd was nearly 5 times higher than the background value,Pb also had more than 1 times;the content of Cr was low,less than the background value of 50%.In all of the 108 sampling points,the contents of all the six elements have a different number of sampling points higher than the background value,especially the Zn element was the most significant,Cd was the least.In addition to Ni,the average of Cd,Cr,Cu,Pb and Zn were not difference for the median,the coefficient of variation of six kinds of heavy metal elements in the sequence was Cr>Pb>Cd>Ni>Cu>Zn,did not exceed 1,belong to the medium variation,the distribution of heavy metals in soil had a very high uniformity.The distributions of Cd,Cr,Cu,Pb and Zn elements were the normal.(2)L.gmelinii had different levels accumulation for Cr,Cu,Ni,Pb and Zn,and Cd showed few detection.From the distribution of heavy metal elements,the rule was the highest in the bark,and secondly in the root,and the lowest in the xylem.Some heavy metals,the distribution were similar with the content of soil layer,such as Cr,Cu.The other elements was low coupling degree,even there is a complex distribution pattern,and no regularity were with soil layer,root,xylem and bark.From the correlation of the adsorption of five heavy metal elements,the Zn had negative correlation with other elements;Cr had a strong positive correlation with Ni and Pb.Enrichment coefficient and transfer coefficient of Cr,Cu,Ni and Pb showed the trend that up-ground was higher than under-ground and floor and the terminal higher than the front,there was a strong upward and outward migration;transport coefficient of 5 elements were higher than "the excellent plant of remediation heavy metals pollution"standard,so L.gmelinii can be play an effective role in the bioremediation of heavy metals in the experimentation area.(3)In L.gmelinii seeding,the stem was the highest and the leaf was the lowest;leaf/shoot was the highest and stem(xylem)was the lowest for adult tree.It can be speculated that:nutrient transportation distance was short because of low height in seedling stage,transfer power of heavy metals with water and nutrient transport from the roots to the ground to the terminal was weak,therefore,heavy metals much accumulated in the stem;with the plant growth,tree need strong force to transport nutrient and water up to the end,so it had more heavy metals in the branch and leaf parts.The transport ability of seedlings and trees for 5 heavy metals was different.In most cases,the transfer coefficient of tree and seedlings have no significant difference,and significant difference for Ni and Pb.In contrast with the transport capacity of seedling and tree for the same element,transport trend of different organs for heavy metals was roughly opposite,because the seedlings were small,the transport capac(?)y was weak,therefore,stem and branches were the higher transfer coefficient,and trees were tall,there is a strong upward transport power,which also showed a strong heavy metal transport,the transfer coefficient of leaves and branches were namely higher than the stem.(4)Pinus koraiensis,Piuus sylvestris ver.mongolica,L.gmelinii and Fraxinus mandschurica showed strong adsorption capacity for Zn,followed by Cu,and the adsorption capacity of the other three elements was lower than that of the former two.From the planting period for'influence on the adsorption capacity,P.koraiensis,P.sylvestris ver.mongolica,L.gvme,linii showed the adsorption capacity of Zn and Cu increased with time,for the rest of the three elements to increase was not obvious;while Fr.mandschurica decreased the adsorption capacity with age.The experiment pro-ved that P.koraiensis,P.sylvestris ver.mongolica,L.gmelinii can be used for the adsorption Zn and Cu,and it had the stable adsorption for Ni,Pb and Cr,through biomass increasing,adsorption effect increased year by year. |
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