Spatial Distribution And Accumulation Characteristics Of Heavy Metals In Greenbelt Plants Along Xi’an South2nd Ring Road

Nowadays, the primary abilities for greenbelt plants selected were dust holding and noisefiltering. However, with the increasingly serious problem of heavy metal pollution caused bytraffic source in the soil, the adsorption capacity of plants to heavy metals has naturallybecome another necessary quality. This paper, taking the17greenbelt plants of south2nd ringwhich had the busiest traffic among Xi’an city and the5of relatively clean Yan Ta campus ofChang’an university as the research objects and determing the concentration of Cd, Cr, Cu, Ni,Pb, Zn in the plants and soil, had analyzed the spatial distribution pattern and accumulationcharacteristics of heavy metals in plants. The correlation of heavy metals betweenconcentration and form, accumulation and concentration, accumulation and soilphysicochemical property had been achieved by employing Statistical software SPSS18.0andExcel2010to investigated element correlation, bio-concentration and transfer ability. Aftercomprehensivly considering the heavy metal concentration, accumulation, ability to transferand survive, the plants which are suitable for Xi’an roadside could be selected. Specificresearch results are as follows:1. The spatial distribution of heavy metals in the plants did not show obvious regularity.For magaphanerophytes and suffruticosa plants, heavy metals concentrated in plant roots andbark. Differently, many heavy metal elements in plants concentrated in different areas. Inaddition, the research had illustrated that among the magaphanerophytes plants, spruce hadthe most special distribution of heavy metals and six kinds of heavy metals are rarelydistributed in leaf and root.2. To investigate whether the concentration of heavy metal elements in plants have acertain regularity due to its own properties, the concentration of different elements within thesame plant in underground and ground organs was compared by line chart in this paper. Theresults showed, with the increasing atomic number(Cr�'Pb), the heavy metal concentrationsof tree layer and shrub layer plants between different organs show "N" glyph change trend.Furthermore,the heavy metal concentrations in the underground organs of tree layer and shrublayer have the basic law of CZn＞CCu、CNi、CCr、CPb＞CCd."N" glyph change trend presentedby the ground organs of shrub plants was more flat, and Pb and Cr had the maximumconcenration and minimum concentration respectively.3. Taking the mean concentrations of plants’ different parts as comparability factor,magaphanerophytes and suffruticosa plants showed similar spatial distribution pattern. But the concentrations of heavy metals in bark were totally different between magaphanerophytes andsuffruticosa plants. It was little in magaphanerophytes plants, while the suffruticosa plants hadopposite situation. It was thus clear that the accumulation characteristics of heavy metals inbark were most related to natural features.4. Among magaphanerophytes plants, the heavy metals consistence in Ligustrumlucidum Ait and Pinus bungeana Zucc. were highest, while Nandina domestica andChimonanthus praecox among suffruticosa plants and Festuca arundinacea amongherbaceous plant.5. Pinus bungeana Zucc. was the most powerful magaphanerophytes plants in gatheringheavy metals, especially when enriching Zn (bioconcentration factor was1.123). Suffruticosaplants’ average power was better, and Nandina domestica was the best in them.6. Among magaphanerophytes plants, Picea asperata, Juniperus formosana andPhotinia serrulata Lindl., which concentration were little showed significant transfer abilities.The biological transfer factors of Picea asperata to six heavy metal elements were all above1.Among seven suffruticosa plants, Nandina domestica did best in transferring heavy metals.The biological transfer factors of it to Pb and Zn were1.141and1.418respectively.7. By the comprehensive comparison of heavy metal consistence and accumulationability of plants and the transfer ability of aerial portion, the paper chose Pinus bungeanaZucc. and Nandina domestica as preponderant plants for gathering heavy metals. Pinusbungeana Zucc. was good at the accumulation of Zn and Cd. However, Nandina domesticawas multi-metalpreponderant plants. It was good at Cd, Cu, Ni, Pb and Zn.8. Among the correlations of six heavy metal elements,6of them are remarkable bothin magaphanerophytes and suffruticosa plants. Cr and Ni were closest in magaphanerophytes,while Cu and Zn in suffruticosa. There was none significant correlated in herbaceous plants,but Pb had good correlations with Cu and Ni, Zn had a good correlation with Cd. Each of Cr,Pb and Zn’s concentrations of magaphanerophytes were influenced by Ni, which means Niwas an important factor in the multi-pollution of heavy metals. The concentrations of eachheavy metal element were into linear relationships only with one element in suffruticosa, andPb affected most. Cd affected most in herbaceous plants, which including Cr, Pb and Zn.9. The heavy metals’ concentrations in root were all positively correlated to the one ofthe effective states of heavy metals. Among the six elements, the correlation of Ni was best,while Pb was worst, which pointed out that magaphanerophytes was resisted against thepoisoned Pb.10. The accumulation of plants to heavy metals had no significant correlation with the heavy metals’ amount in the soil around root which means that the support of soilenvironment could not influence the accumulation ability of plants.11. Analyzing the correlation between BCF and the physical and chemical parameters ofsoil around root shows plants have reducing enriching abilities to other five elements beside Cu with growing pH value. However, though the enriching abilities of plants have positive correlation with pH value, this correlation is indistinctive. For these six metallic elements, their enriching abilities have negative correlation with soil salinity, but it is indistinctive as well. Furthermore, negative correlation between the enriching abilities of these six metallic elements and the soil conductivity indicates conductivity has control effects on heavey metals. In additionto Cd, plant enriching abilities have negative correlation with the rapid available phosphorusof soil aournd root. Therefore, phosphate pollution could obviously decrease the the effectivestate concentration of hevay metals and convert them into residual condition; plant enrichingheavy metals was consequently receded. The particle sizes of soil have postive correlation with plant enriching these six metallic elements.