Effects Of Ionic Rare Earth Mining In Southern China On Soil Characteristics And Microbial Community In Mining Areas

The ion-type rare earth deposits are unique in South China.Because of their increasing preciousness and scarcity,their international strategic status becomes increasingly prominent,and they also make significant contributions to the development of national economy.However,the exploitation of southern ionic rare earth resources has caused serious pollution in mining area and the surroundings,which has attracted much attentions.In this paper,the soil of ionic rare earth mining areas,raw ore soil(unexploited mining soil),and surrounding soil(soil around the mining area)were the research objects.The basic physical and chemical properties were determined according to the national standard method.The fractions of rare earth elements were extract by the community bureau of reference(BCR)and analyzed by inductively coupled plasma mass spectrometry(ICP-MS).The results showed that mining activities not only aggravated soil acidification in the mining area,increased the content of ammonia nitrogen and rare earth elements(REEs)in the surrounding soil,but also changed the fractions of rare earth elements of mining soil.The fertility and metal pollution risk assessment of three types of soils showed that the soil fertility in mining areas and surrounding soils was low due to mining activities.The metal pollution in mining areas was caused by direct or indirect potential effects of REEs.Although the geo-accumulation indices of the surrounding soil were not high,there were still potential metal pollution risks.The correlation analysis between soil geochemical characteristics showed that the bioavailability and fractions of REEs were regulated by p H,ammonia nitrogen,moisture content and TC.And the change of environmental conditions may cause that REEs transformed into bioavailable fractions,bringing potential threaten to the ecological security of mining area and surrounding soil.Real-time PCR and Illumina Miseq high-throughput sequencing were used to investigate the abundance and community structure of bacteria,archaea and ammonia-oxidizingmicroorganisms in different soil types.The results showed that there was no significant difference in the abundance of bacteria and archaea between three types of soil,but the abundance of bacteria was higher than that of archaea in each sample.The correlation analysis between soil physicochemical properties and microbial abundance quantitative and α-diversity showed that the microbial abundance and diversity of different types of soil showed different correlations with basic physicochemical properties and fractions of metal.Network analysis reflected that interaction between archaea or bacterial communities could help them resist harsh environments and improve living conditions.In addition,the relationships between bacterial or archaeal in the non-mining soil was stronger than that in mining area,indicating that frequent disturbance activities lead to stronger interaction between the bacterial or archaeal community.The abundance of ammonia-oxidizing archaea(AOA)was significantly higher than that of ammonia-oxidizing bacteria(AOB),and it was difficult to detect AOB in many soil samples.AOA was the major contributor in ammonia oxidation.Chloroflexi,Proteobacteria,Actinobacteriota,Acidobacteriota and WPS-2 of bacterial phyla,Crenarchaeota,Thermoplasmatota of archaea phyla,AOA phylum Thaumarchaeota,and AOB phylum Proteobacteria were the main microflora that played an important role in nutrient cycling and improved the ecological environment of the mining area.This study provides a theoretical basis for a comprehensive understanding of the damage to soil environment and ecological risk assessment caused by in-situ leaching,reveals the relationships between microorganisms and its habitat,and provides a scientific basis for directional regulation of pollution remediation in mining areas in the future.