| In order to study the effects of Vetiveria zizanioides L.on substrate of coal spoil-heaps soil,3rd,4th,7th,9th,and 14-year-old Vetiveria zizanioides L coal spoil-heaps soil were selected as the research object.To explore the changes of physicochemical properties and heavy metal content in the substrate of 0-50 cm depth of coal spoil-heaps soil under different ages of Vetiveria zizanioides L.community and the enrichment and transfer ability of Vetiveria zizanioides L.to heavy metal copper,zinc,cadmium,lead and arsenic.The main findings are as follows:(1)With the increase of age of Vetiveria zizanioides L.the substrate bulk density of 0-50 cm soil layer gradually decreased,and the bulk density of 0-10 cm soil layer changed most obviously.The substrate density of coal spoil-heaps soil of 4th,7th,9th,and 14-year-old Vetiveria zizanioides L.were respectively compared with the3-year-old Vetiveria zizanioides L.coal spoil-heaps soil,the substrate bulk density decreased by 5.63%,12.50%,18.5%,and 21.88%.In the vertical section,the bulk density of the coal spoil-heaps soil of the Vetiveria zizanioides L.community of different ages increased with the increase of the depth of the profile,showing that the improvement effect of 0-20 cm was significantly higher than that of 20-50 cm.The porosity and water content of the substrate are opposite to the bulk density as the age of Vetiveria zizanioides L.increases.In the 0-10 cm soil layer,the porosity of the 4th,7th,9th,and 14-year-old Vetiveria zizanioides L.coal spoil-heaps soil increased by4.09%,15.22%,and 21.14% ?30.09%,respectively,compared with the 3-year-old Vetiveria zizanioides L.coal spoil-heaps soil.Water content increased by 16.78%,23.85%,30.54%,59.63%,respectively.Both of the substrate profiles showed 0-10cm>10-20 cm>20-50 cm.The mechanical composition of the substrate of coal spoil-heaps soil,with the increase of Vetiveria zizanioides L.age,the sand content in0-50 cm soil layer gradually decreased,and the clay content and powder content gradually increased,14-year-old Vetiveria zizanioides L.coal spoil-heaps soilcontained less 3.79% sand,and the clay content and the power content increased by11.38% and 5.37%,respectively,compared with the 3-year-old Vetiveria zizanioides L.coal spoil-heaps soil.(2)With the increase of the age of Vetiveria zizanioides L.the content of organic matter,total nitrogen,alkaline nitrogen available phosphorus,and available potassium in the 0-50 cm soil layer of the plot all showed a gradual increase trend,In the 0-10 cm soil layer,the content of organic matter in the 4th,7th,9th,and 14-year-old Vetiveria zizanioides L.coal spoil-heaps soil was increased by 0.13%,6.37%,and 10.03%,18.84%,respectively,compared with the 3-year-old Vetiveria zizanioides L.coal spoil-heaps soil.total nitrogen increased by26.31%,26.31%,47.37% and 94.74%;Alkaline N increased by 15.12%,26.81%,48.08% and 71.37%,respectively;Available phosphorus increased by 11.35%,17.02%,22.69%,and 24.82%,respectively;and available potassium increased 9.29%,28.72%,40.27%,72.68%.The content of organic matter,total nitrogen,alkali-hydrolyzed nitrogen,available phosphorus,and available potassium of coal spoil-heaps soil in 10-20 cm and 20-50 cm soil layers did not increase more than 0-10 cm.The contents of organic matter,total nitrogen,alkali-hydrolyzed nitrogen,available phosphorus and available potassiumin substrate profile were 0-10 cm>10-20 cm>20-50 cm.It shows obvious apparent aggregation.The p H of the coal spoil-heaps soil is improved obviously with the increase of Vetiveria zizanioides L.age,and the effect of 14 years old Vetiveria zizanioides L.coal gangue sample was the best,and the substrate tended to be neutral.(3)With the increase of Vetiveria zizanioides L.age,the contents of copper,zinc,cadmium,lead and arsenic in the substrate showed a downward trend.Among them,in the 0-50 cm soil layer,the contents of copper,zinc,cadmium,lead and arsenic in14-year-old Vetiveria zizanioides L.coal spoil-heaps soil were respectively decreased by 5.36%,7.19%,25.00% and 79.58% compared with the 3-year-old Vetiveria zizanioides L.coal spoil-heaps soil sample plots.copper,zinc and cadmium in the substrate profile show 0-10 cm>10-20 cm>20-50 cm.lead and arsenic exhibit 0-10cm>10-20 cm>20-50 cm with increasing depth of the substrate profile.(4)The contents of heavy metals in Vetiveria zizanioides L.were all in theunder-ground> above-ground.With the increase of the age of Vetiveria zizanioides L.the total content of heavy metals in Vetiveria zizanioides L.increased gradually.The results showed that zinc>arsenic>copper>lead>cadmium;The enrichment coefficients of cadmium,lead,and arsenic in the under-ground and above-ground of the Vetiveria zizanioides L.were all greater than 1,and the enrichment coefficients of copper and zinc were less than 1.It showed that the under-ground and above-ground parts of the Vetiveria zizanioides L.had strong ability to enrich Cd,Pb and As.The transfer of heavy metals by Vetiveria zizanioides L.of all ages was less than 1.It shows that the absorption of heavy metals by vetiver is mainly concentrated in the roots. |
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