|
Urban forest vegetation as a \Therefore, in the process of rapid development of China's urban, urban forest has become important to the form and content of the eco-city construction. The thesis for the study of the the Changsha urban forest soil, in accordance with the city center in Changsha, the edge of the city, the cities surrounding three gradient were set 11 soil sampling areas, collected 93 samples of soil bulk density, organic matter, total N, total P, Cu, Zn, Mn, Cd, Pb content were measured, and the results of the variance and statistical analysis. Space to explore the urban forest soil heavy metals distribution and sources of comparative study of different greenbelts types of heavy metal content and the degree of pollution, intended to reveal the different urban forest type, degree of urbanization, the impact of different green lands on the content of heavy metals in urban soils potential law, aimed find Changsha Green factor of heavy metal pollution and its contamination pathways, the Changsha urban green space greening tree species selection, soil heavy metal pollution prevention and repair and improve the quality of the urban environment, to provide a scientific basis for protection of population health. The main conclusions of the study are as follows: (1) Changsha urban forest soils the average content of the order of five kinds of heavy metals: Mn (166.34mg-kg-1) gt; Zn (50.22mg kg-1) gt; Pb (31.12 mg-kg-1) gt; Cu (23.56mg-kg-1) gt; Cd (0.16mg · kg-1). More Xiaoyuan Park of 11 in the study area, the southern suburbs Park, the osmanthus Park and the Central South University of Forestry Science and Technology 4 study area with five kinds of heavy metal content, and away from the crowd Shiyan Hu, Dashanchong the Tomb Park Park of heavy metals The content is relatively small. Differences in the distribution of the five kinds of heavy metals in the urbanization gradient forest soil in varying degrees, the general rule is: the city center gt; the urban fringe gt; around the city. (2) absorption of different forest types for different kinds of heavy metals migration, accumulation capacity. Migration and accumulation of four heavy metals Cu, Zn, Pb, Cd absorption ability are osmanthus Du Yinglin best for Mn purification effect is a sweet-scented osmanthus forest. Greenbelt there are some differences in reduction of the role of heavy metals by different plant species, reduction of the role of woodland on heavy metal is significantly higher than the lawn. Lawn for the absorption of Cu, Cd and Pb migration role less than woodland. Woodland Mn absorption, migration is substantially lower than the lawn. (3) in the same forest type, soil, Cd and Zn from the same sources of pollution likely Pb and Mn from the same source of contamination may be low. The same study area soil, osmanthus Parks Botanic Garden soil heavy metals from different ways. Martyrs' Park, Linke campus soil heavy metal elements Zn, Pb, Cd, most likely derived from a common source of contamination. Cu, Zn, Cd, Yuelushan soil from the same pollution sources may be large. Xiaoyuan Park soil Cu, Pb, Zn and Cd from a common source of contamination. Changsha Tomb Park soil Pb and Zn, Pb and Cd may come from a common source of contamination. Nanjiao Park, black Mi peaks, Shiyan Hu, Dashanchong sources of soil heavy metals may be more than one. In different research area, Cu and Zn, Cd and Pb, Cd and Mn, there may be a different source. Pb and Cd, Zn and Mn, Pb, Zn, Cd and Zn in different research areas may have the same source of pollution. (4) in different urban forest types, different heavy elements with the same soil chemical indicators different, the same heavy metal elements with different soil chemical indicators correlation is not the same. The study area due to the degree of human activities and the natural environment, the same soil chemical indicators with different heavy metals is different, different soil chemical indicators of heavy metal with the same correlation is also different. Soil organic matter, total P, total N, and in different environments in the same heavy metal elements are different. (5) higher Changsha part of the heavy metal content of the forest soil may be mainly derived from traffic pollution, may be derived from living sources of pollution or industrial activities. Urban forest soil sources of heavy metals is very complex, and at the same time, the metal elements of the natural sources of change and deposition granularity might be interested in the content of heavy metals have some impact. Therefore, this paper mainly restricted to the analysis of the sources of heavy metals in forest soils, Changsha qualitative description. (6) in the urban forest soils in the study area from a single pollution index, Pb pollution index, the highest degree of pollution, Cd pollution levels for Zn pollution index followed by the smallest, lowest pollution levels. From the comprehensive pollution index, soil heavy metal pollution level of Changsha City Forest City: clean, Shangqing Jie, mild, pollution. (7) the urbanization gradient Forest soil heavy metal pollution degree of pollution levels in descending order: city center gt; the urban fringe gt; outskirts of the city. Forest soil types in different cities, from a single pollution index, the lowest Zn pollution index the Pb pollution index is the highest, by the size of the pollution index Sort: Pb gt; Cd gt; of Cu gt; Zn. Comprehensive pollution index, Changsha soil heavy metal pollution of forest types have reached the the Shangqing Jie (warning limits) level, where pine forest soil heavy metals Composite Index up to a mild level of contamination, belongs to the most polluted, osmanthus Elaeocarpus mixed forest integrated Pollution Index (API) minimum. Therefore, the angle of heavy metals from the purification of urban forest soil in the city should reduce the pine forest, appropriately increase osmanthus Elaeocarpus mixed forest and other broad-leaved forest. (8) In a different type of urban greening the lawn heavy metals pollution index was significantly higher than the woodland, lawn belonging to a mild level of contamination, and the woodland belonging to the the Shangqing Jie (warning limits) level. Forests of heavy metals Cu, Zn, Cd, Pb purification capacity is higher than the lawn. Seen, in the process of urban greening, as much as possible to create a woodland building less lawn. (9) is recommended in the planning of urban greening, should as much as possible to create a woodland building less lawn. According to the planting the content of heavy metals in soils of different regions corresponding to the kinds of heavy metal to good forest absorption capacity. Generally speaking, the angle of heavy metals from the purification of urban forest soil in the city should be reduced by pine forests, appropriately increase osmanthus Elaeocarpus mixed forest and other broad-leaved forest.
|