| China's ionic rare earth mining has been going on for more than 40 years.Due to the limitations of mining technology and supervision in the early years,a large number of abandoned mines have been formed and left unattended over the years,which has caused serious and large-scale ecological damage and environmental pollution.Huge number of leached tailings were left unprotected in the abandoned mine area.Under the action of environmental erosion,serious soil erosion occurs,forming large areas of local desertification.Leached tailings are extremely poor in physiochemical and biological properties as a soil,and especially,with high acidity,sandy texture and poor soil nutrition,have degraded into extremely harsh habitat conditions.At present,the ecological restoration of abandoned rare earth mines is mainly aimed at realizing the re-greening of mine areas.The commonly used restoration strategy is "engineering technical measures plus vegetation screening and optimal allocation and planting technology".However,in terms of actual effect,this strategy does not fundamentally solve the serious problem of soil erosion in the mining areas.With the passage of time,the degradation of artificial vegetation is serious,which leads to little guarantee for the stability and long-term effect of the restored artificial vegetation.In this paper,with the successful experience drawn from the application of artificial biological soil crusting technology in soil and water loss control in desertification area,the screening,purification and application effect of rare earth tailing specific biological soil crusting bacteria were studied.The main research results are as follows:(1)Eight rare earth tailing specific Cyanobacteria isolates were obtained through screening and isolation,all shown considerable capacity in forming biological soil crusts(BSCs)on the top soil of leached rare earth mine tailings.And with proper cultivation measures,all BSCs can evolve into the higher forms,such as of mosses and lichens,through succession.They were named JP-1,JP-2,JP-4,JP-5,JP-6,JP-8,JP-16,JP-17,respectively.(2)In comparison with the control,all isolates can grow well on the surface of tailing soil and gradually forming bryophyte sclerotium,which can effectively improve the content of organic matter,pH,particle agglomeration,bulk density,and microbiota of the top soil,and the effects were significantly positively correlated with the biomass of BSCs formed.Among the 8 isolates,there are 3 isolates that are relatively better and demonstrated significantly higher capacity in terms of BSCs formation and soil improvement with similar inoculation doses.They are JP-16,JP-17,respectively.(3)Through experiments of inoculation & BSCs cultivation and soil erosion simulation,the capacity in forming BSCs and therefore inhibiting tailings erosion,of the 8 isolates,were comparatively analyzed.The results showed that the BSCs of JP-6,JP-16,and JP-17 are relatively better in terms of tailings erosion inhibition.Compared with the control,the BSCs of the 3 isolates significantly reduced the Runoff flushing in terms of volume,velocity,sand content and volume of sand transported.(4)Taking into consideration of the comprehensive capacity in BSCs formation,soil improvement and erosion inhibition,isolate JP-16 was selected as the best candidate for preparation and development of commercialized biological soil crusting agents.Scaling-up culture condition of JP-16 was studied,and the results showed that a culture condition of pH 8.0,temperature 26 ?,lighting 2000 lux,day/night ratio 12:12,culture media BG-11. |
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