| Hunan Xiangtan Manganese mine is located in Hunan Xiangtan Beijiao crane Ling town.After many years of production,soli heavy metal pollution is very serious in mining area.In recent years,a series of measures have been carried out in the manganese mine area,and the ecological environment of the mining area has been repaired.In this paper,the Landsat images of the Manganese mine region in 1996,2000,2004 and 2016 are selected.On the basis of fully consulting the previous data,the Manganese mine is divided into the background area covering the whole image,the main Manganese mine area as main mine area and far away from the main mine area as the contrast area.By analysis and comparison the date in time and space two scales,the number of land use changes in the three areas is obtained,and according to the vegetation parameters of farmland and woodland in the three areas,the difference ratio,STD/MEAN and STD/RANGE were obtained.Using these data,the change of land use in the three areas was analyzed,and the heavy metal stress of vegetation in manganese mine area was obtained.The heavy metal pollution in manganese mine area and the restoration effect of ecological restoration project in Manganese mine area were also evaluated.This article has obtained the following main results:(1)The change of land use in Manganese mine area:1996-2000 Manganese mine area is greatly reduced,the area of the water surface is rising year by year in 1996-2016,and the area of woodland increases slowly and the area of farmland decreases slightly,but the vegetation cover area in the Manganese mine area in 2016 is higher than that in 1996.This shows that the restoration of ecological environment in Manganese mine have been made some good result.(2)Heavy metal stress status of vegetation in Manganese mine area:The NDVI mean of farmland in main mine area,background area and contrast area was decreased from 1996 to 2016,the heavy metal stress of farmland vegetation in all areas increased year by year.And the difference ratio of the main mining area with the background area and the contrast area is increasing year by year,it is means the deterioration of the stress status in main mine area was lower than that the other two regions.And the difference ratio of the main mining area with the background area and the contrast area in woodland was less than 0,and the NDVI mean of the woodland in three regions has decrease in 1996 to 2000,increase in 2000 to 2016.Those shows the heavy metal stress in the forest vegetation in the main mine area in 1996 to 2000 was deteriorated,but it was improved year by year in 2000-2016,and the heavy metal stress degree in main mine area is more serious than the contrast area and the background area..(3)The condition of soil heavy metal pollution:Heavy metal pollution in manganese mine and its surrounding area mainly depends on rainwater and rivers.Heavy metal pollution in farmland is increasing year by year,but the increase rate of heavy metal pollution in the main mine area is lower than that of other two regions.Heavy metal pollution in woodland has been controlled,the pollution situation in the main mine area has been improved gradually in 2000 to 2016.(4)The evaluation about restoration of ecological environment in Manganese mine area.The ecological environment restoration project of manganese ore and its surrounding areas reduced the bare soil area and increased the coverage of vegetation.The ecological environment restoration project made pollution of heavy metals in the manganese mine areas got better,and made the heavy metal pollution of the farmland in the main mine area deteriorated slower.And the artificial ecological environment restoration and natural conservation measures in all areas got good restoration results both,and the effect of artificial ecological restoration in the main mine area is better than the natural conservation effect in the background area. |
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