Study On The Response Of Soil Humus Oxidation To Gaseous And Thermal Gradient In Reclaimed Soil Filled With Coal Gangue

The dynamic changes of carbon footprint and carbon carrying capacity in coal resource-based cities reflect the changes of regional carbon pool.The dynamic changes of soil humus can reflect the decomposition and transformation of soil carbon pool on the microscopic scale.Based on the field investigation,in some ecological restoration area in Huainan and indoor simulation,this paper tries to clarify the response mechanism of the humus in the surface of reclaimed soil filled with coal gangue to the gas-thermal release of the bottom gangue.The main conclusions are as follows:?1?During the period from 2005 to 2016,Huainan's carbon footprint increased at a rate of 4.20% annually,and its carbon carrying capacity increased at a rate of 9.10% annually.The contribution rate of Huainan to Anhui's carbon footprint decreased from 7.25% to 5.84%,while the contribution rate to its carbon carrying capacity increased from 0.71% to 2.07%.Net carbon footprint per capita,carbon footprint density,carbon footprint intensity and carbon pressure index were all higher than Anhui in the same period,but the gap was decreasing.It can be observed that,as a coal resource-based city,Huainan has made some achievements in implementing its policies and strategies to reduce carbon emissions,but the pressure is still relatively large.In addition,the regional coal mining subsidence area is constantly expanding,which may have a certain impact on the regional carbon bearing capacity,and put forward new requirements and challenges for the development of regional industry and the adjustment of land planning.?2?Water soluble substances?WSS?of topsoil in the restoration area are relatively abundant,while humic acid?HA?,fulvic acid?FA?and Humin?HM?are relatively inadequate.The HE of the soil profile is mainly HA,while FA is the main component in the soil profile in the control area,and FA is transferred from the organic layer to the mineral layer.Results of PQ and HA's E4/E6 showed that the humification degree of the topsoil with thicker topsoil thickness is larger than that with thinner topsoil thickness.There is a significant correlation between humus components.Soil physical and chemical properties were significantly correlated with water-soluble substances,but were not related to other components of humus.The thinner topsoil thickness may increase the temperature sensitivity of topsoil,thus affecting the process of soil respiration and chemical oxidation of gangue matrix to release gas and heat.?3?CO₂ supply at the bottom significantly increased the CO₂ concentration of the soil profile distribution,and formed a gas gradient in the reconstructed soil profile.The CO₂ concentration in the lower layer was greater than in the upper layer.The variability of WSS during the experiment was larger,and this fluctuation may be related to the alternation of dry and wet soil.Under different treatments,the variation trend of humus components was consistent.The decomposition of HA and FA was significant,and HM increased,which may mean the transformation of HA and FA to HM.Bottom gas treatments inhibited the decomposition of HA and FA during the test.At the end of the experiment,the inhibition decreased or disappeared.The gas supply inhibited soil microbial activity to some extent,but did have no impact on the microbial activity of the topsoil.During the experiment,the humification degree of soil increased,but the HA molecule was simplified.Overall,the effect of bottom gas supply on topsoil humus oxidation is not significant.?4?Under the condition of heating on the bottom,the reconstructed profile forms a temperature gradient gradually decreasing from the bottom and the surface.Surface soil temperature was less affected by heating on the bottom.The trend of WSS,HA and FA is relatively consistent,while the component HM is relatively stable.Jeating on the bottom promoted the decomposition of the components of the topsoil humus.At the same time,the undecomposed or semi-decomposed plant and plant residues in the soil,the test period and the soil water condition influenced the degree of promotion.Overall,the influence of heating on the bottom of topsoil humus oxidation is not obvious.