Absorption And Accumulation Capacity Of Afforestation Plants To Atmosphere Heavy Metal Pollutants In Yan’an City

In these years, along with the discharging of automobile exhaust and burning of fire coal,fuel oil, industry and household refuse in urban, lead (Pb), cadmium (Cd), copper (Cu) andmany atmosphere heavy metal pollutants are permeating in people’s life, and making athreaten to people’s health. Therefore,14common afforestation plants were used as researchobject in this research. On the basis of field survey, we applied pollutant contents analysis tostudy the absorption and accumulation ability of different pollution regions and afforestationplants to lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), zinc(Zn), at the same time,the membership function methods were used to select best afforestation plants for absorbingthe heavy metal. Then we used correlation analysis methods to discuss the relationshipbetween heavy metal accumulation quantity and atmospheric pollution index IPC ofafforestation plant leaves, and made a standard according to urban air quality estimation scale.In the end, we systematic assess the atmospheric heavy metal pollution status of Yan’an urban,and accumulate a scientific basis for recognizing the relationship of urban afforestation plantsand atmosphere heavy metal pollutants. At the same time, we provide theory and practicalevidence for Yan ’an urban environmental quality assessment and protection and urbangreening plan rationality. The results show that:(1) The atmospheric heavy metal pollution absorbing abilities of14commonafforestation plants in Yan’an urban were significantly different, while the same kind ofafforestation plant exist difference in absorbing different atmospheric heavy metal.(2) The14species afforestation plants in different atmospheric pollution areas havesignificantly difference in heavy metal content. In general, the leaves in larger traffic flowarea have higher heavy metal content than that in slight pollution area and pollution-free area.(3)14species urban afforestation plants in Yan’an City has significant positivecorrelation in heavy metal accumulation of Pb, Cd, Cr, Cu, Zn and its correspondingatmospheric pollution index (R>0.89). It is indicated that we can estimate the atmosphericheavy metal pollutant concentration according to its heavy metal content in different urbanafforestation plants leaves, and provided a basis for monitoring atmospheric pollution statusin different regions. (4) According the urban air quality evaluation hierarchy standard to systematic reviewthe heavy metal pollution situation in Yan’an City. The most atmospheric heavy metalpollutant is Pb, followed by Cd and Cr, and the most polluted areas are hundreds metersavenue in transportation junction and Bao-Mao expressway; Yaodian industrial park is amiddle level pollution region; Lijing house living quarters and North-West park are miredpolluted regions; Lantau Peak rest area is pollution-free region.(5) Analysis by synthesis of14species urban afforestation plants in Yan’an City withtheir absorbinf abilities of atmospheric heavy metal pollutant. Among them the arbor whichhave highest absorbing ability in atmospheric heavy metal pollutant are chinese ash（Fraxinuschinensis）, willow（Salix matsudana f. pendula）, purple-leaf plum（Prunus ceraifera cv. Pissardii）,ailanthu（sAilanthus altissima）, and Chinese scholartre（eSophora japonica）；the shrub which havehighest absorbing ability in atmospheric heavy metal pollutant is gold leaf privet（Ligustrumvicaryi）.