| The rapid development of industrialization and urbanization resulted in the increment of SO2concentration in the near-ground atmosphere and had serious influence on human health and economic development. It is important to estimate the pollution of SO2in atmosphere by measuring the sulfur content in blade. In this paper,31kinds of landscape plants in Wuhan Iron and Steel (Group) Corporation, Heping Park and the campus of Huazhong Agricultural University had been selected as the research object. The experimental configurations were HR-1024spectrometer and LI6400photosynthetic instrument which could measure hyperspectral reflectance and photosynthetic characteristic value in leaves and determine the sulfur content, water content and chlorophyll content of leaves at the same time. The analysis to the spectral and photosynthetic characteristics of the SO2polluted landscape plants furnished the theoretical basis for the trees selection which had strong sewage suction, high resistance to SO2pollution of the environment. The main results are as follows:(1)The changes of SO2content in the atmosphere was:the coking plant of Wuhan Iron and Steel (Group) Corporation> Heping Park> Campus of Huazhong Agricultural University. Wuhan Iron and Steel (Group) Corporation is as four point five times as Huazhong Agricultural University, and it is as four point two times as Heping Park.(2)In the22species of plants, the same plant in different polluted places had different sulfur content in leaves. The more serious pollution of the environment, the more content of sulfur in the leaves, that is:coking plant (9.292mg/gDW)> Heping Park (8.126mg/gDW)> Huazhong Agricultural University Campus (6.279mg/gDW). The sulfur content of different plants in same area had significant difference (p=0.002<0.01). The plants whose leaves contained higher sulfur content after cluster analysis were Nerium indicum Mill, Firmiana platanifolia, Platanus×acerifolia, Jasminum mesnyi, Ginkgo biloba, Viburnum odoratissimum var. Awabuki and Elaeocarpus sylvestris. Medium level of sulfur content plants contained Eriobotrya japonica, Phyllostachys pubescens, Osmanthus fragrans, Prunus ceraifera, Cinnamomum camphora, Pittosporum tobira, Broussonetia papyrifera, Lorpetalum chinense var.rubrum and Ligustrum lucidum. The low sulfur content plants had Magnolia grandiflora, Morus alba, Rhododendron simsii, Photinia serrulata, Reineckia carnea (Andr.) Kunth and Lagerstroemia indica.(3)Based on sulfur content of Huazhong Agriculture University plants, the sulfur assimilation trend of the same plant in different polluted areas is:coking plant> the Heping park. Different types of plant of the same area existed significant difference (p=0.001<0.01). The similar classification trend between the amount of sulfur assimilation and sulfur content in leaves had been found through the cluster analysis. Larger amount of sulfur absorption of the trees in coking plant and the Heping park had14kinds of plants, such as Prunus ceraifera, Ginkgo biloba, Firmiana platanifolia, Viburnum odoratissimum. var. Awabuki, Lorpetalum chinense var.rubrum, Reineckia carnea (Andr.) Kunth, Nerium indicum Mill, Eriobotrya japonica,Broussonetia papyrifera, Ligustrum lucidum, Magnolia grandiflora, Elaeocarpus sylvestris, Lagerstroemia indica, Osmanthus fragrans and so on, which could be used as greening plants in heavy polluted areas of SO2. The trees of Cinnamomum camphora, Morus alba, Jasminum mesnyi, Photinia serrulata and Phyllostachys pubescens had an absorption capacity of SO2in the Heping park while took a little function in coking zone due to the low threshold of SO2, which were suitable for repairing the environment of the lower SO2polluted area.(4)Research showed that soil’s sulfur content in coking plant (0.677mg/gDW)> Heping Park (0.282mg/gDW)> Huazhong Agricultural University Campus (0.215mg/gDW), which indicated that the higher the content of sulfur in the atmosphere, the more absorption to sulfur in soil. At the same time, the study showed the significant correlation between the sulfur content in leaves and the total sulfur content in correspondent soil, but the amount of sulfur content of the trees in pollution area was as7-30times as the total sulfur content in soils, which indicated that the sulfur in plant was mainly from atmosphere directly, absorbed from soil sulfur indirectly.(5)According to the leaf hyperspectral characteristics, our studies had acquired the difference of spectral characteristics in SO2polluted plants, using the methods of traditional multivariate statistics, spectral analysis for position variables and vegetation index, which filled the blank of high spectral study in this region at home and abroad. Different plant spectral curves were similar in shape. Reflectance were different in peak of Green, Red Valley and near infrared moisture sensitive wave band, but not obvious in the other band; With the aggravation of pollution, the same plant appeared the trend of Red Edge shifting to blue band, Green Peak shifts to the Red Edge and the reduction of the red and blue band amplitude.(6)Correlation analysis of the original spectrum, reciprocal spectrum, derivative spectrum and sulfur content showed that derivative spectrum had a great fluctuation but a significant correlation, which had a better reflection to reaction spectral information. Hyperspectral feature location, area parameter and the vegetation index were proposed generally according to the specific experimental conditions or a particular remote (remote sensing). However, these indexes were not very sensitive to data intensive and hyperspectral remote and had a medium inversion effect. The sulfur content of leaves in the22typical landscape plants were estimated with the methods of sensitive wave band and high spectral characteristic parameters. The results which obtained after conducting respective high spectral inversion of leaf sulfur content model of14kinds of trees and8species of shrubs and grasses indicated that inversion according to different types acquired higher prediction accuracy.(7)This paper selected the best model to estimate the amount of sulfur content in leaves and the results as followed:The best index model was Y=14.717*e-4.927I which was established with the largest derivative value of blue edge (Db) as variables, the R2=0.255. The best index model for trees was Y=34.54*e-0.809x, which was established with high spectral features of the ratio between green peak reflectivity and Red Valley reflectivity (Rg/Ro) as variables, R2=0.434. The best index model for shrubs and grasses was Y=9.743*e-14.39x, which was established with derivative spectra of856nm as variables, R2=0.546.(8)Compared with the results in non-SO2contaminated area, the landscape plants in SO2contaminated area had appeared a slight symptoms but the photosynthetic index has changed. Value of net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance(Gs), intercellular CO2concentration(Ci) and water use efficiency(WUE) all took on a reduction in SO2contaminated area, however, the leaf water vapor pressure deficit on leave (Vpdl) had a increasing trend. The anti-SO2pollution index values were calculated according to change rate of Pn, Tr, Gs, Ci, WUE, Vpdl, leaf water content, chlorophyll relative content (SPAD) and the leaf sulfur content. Depend on these values, comprehensive evaluation of18kinds of landscape plants’anti-SO2pollution were acquired by using the principal component analysis method and calculating the weight of each index. The strong anti-SO2included Nerium indicum Mill, Eriobotrya japonica, Ginkgo biloba, Platanus acerifolia, Pittosporum tobira, Magnolia grandiflora. The medium anti-SO2contained Elaeocarpus sylvestris, Ligustrum lucidum, Viburnum odoratissimum. var. awabuk, Cinnamomum camphora, Koelreuteria paniculata, Osmanthus fragrans, and the weak anti-SO2had Reineckia carnea (Andr.) Kunth, Lagerstroemia indica, Lorpetalum chinense var.rubrum, Prunus ceraifera, Rhododendron simsi, Photinia serrulata. |
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