| About 6 million hectares of land have been occupied or destroyed by mining in China.Land reclamation in mining areas is an effective way to alleviate the shortage of land resources.It is widely used at home and abroad because it can effectively utilize the waste rock and solid waste produced by mining.In the reclaimed mining area,the guest soil method mixed the fine soil rich in nutrients with the waste rock in the mining area for crop planting,and the guest soil introduced the soil organic matter of different quantity and quality,which caused the carbon cycle change of the reclaimed soil in the mining area.It is helpful to monitor the carbon balance of reclaimed soil in mining area and provide scientific basis for improving the quality of reclaimed soil.In this study,the iron ore waste rock mixed with fine-grained soil in different proportions is taken as the research object,and the plot test is set up.The volume ratios of iron ore waste to fine grained soil in the mixed soil were T1(1:1),T2(1:2),T3(1:4)and T4(0:1),respectively.Iron mine waste rock soil carbon emission monitoring since January 2019 to December 2019,from the daily and seasonal dynamic two time scales clear its dynamic characteristics,and reveal the soil temperature,the physical and chemical properties and the dynamic changes of the enzyme activity,to explore the iron mine waste rock mixed soil quality evolution characteristics and driving factors of carbon emissions,the main results were as follows:(1)The carbon emission of iron ore waste mixed soil has a large change range in April and July,and a small change range in October and December,showing a single-peak curve that gradually increases from 8:00 to 12:00 and then rapidly decreases;The maximum value of carbon emission from T1-T4 treatment was 5.41,6.40,4.81 and 11.95?mol·m-2·s-1,and the minimum value was from 4:00 to 6:00 in the morning.The carbon emission from T1-T4 treatment was-0.84,-0.40,-0.09 and 1.28?mol·m-2·s-1,respectively.When the temperature of mixed soil was low,carbon sink phenomenon occurred.On the whole,there is a significant difference in carbon emission between the T1?T2?T3 treatment and the T4 treatment.With the increase of the proportion of fine grained soil,the carbon emission of the mixed soil tends to increase.(2)Under different proportions of iron ore waste and fine soil treatment,the carbon emissions of mixed soil showed obvious seasonal variation characteristics,with the highest in summer and the lowest in winter;Appear in each processing carbon emissions peak summer(July),T4 treatment compared with T1?T2?T3treatment,the carbon emission was 57.38%,49.34%and 59.68%higher than that of T1?T2?T3 treatment,,the lowest in the winter(January),T1?T4 treatment processing mixed soil carbon in 0.09?0.36?mol·m-2·s-1,carbon emissions between the groups in 7?9 months only significant difference,the present T4(1-0)>T2(1:2)>T3(1:4)>T1(1:1).(3)The content of available phosphorus,total nitrogen,organic carbon and the activities of catalase and sucrase in the mixed soil of iron ore waste showed a trend of gradual increase with the increase of the proportion of fine soil.The maximum reduction in T1?T2?T3 treatment was 79.01%,60.19%,55.60%,54.22%and 66.89%,respectively,compared with that in T4 treatment.The pH of the mixed soil decreased gradually with the increase of the proportion of fine grained soil.The maximum reduction of T1?T2?T3 was 5.03%compared with that of T4.There was no difference in the activity of mixed soil urease between T1 and T3.The enzyme activity ranged from 0.70 to 1.63mg.(g.d)-1,and between 4.05 and 4.90mg.(g.d)-1 in T4 treatment.There was no significant difference in soil temperature and humidity,available potassium content and alkaline phosphatase activity.(4)Correlation and principal component analysis of carbon emission from iron ore waste rock mixed soil show that the key influencing factors of carbon emission from mixed soil are mixed soil temperature,C/N ratio,organic carbon content and sucrase activity.To sum up,the carbon emission of mixed soil in T1?T2?T3 treatment is significantly lower than that in T4 treatment,and the carbon emission of mixed soil tends to increase gradually with the increase of the proportion of fine grained soil.The addition of fine grained soil can improve the physicochemical properties and enzyme activity of mixed soil.Temperature,C/N ratio,organic carbon content,urinary enzyme activity and sucrase activity of mixed soil are the key factors affecting carbon emission of mixed soil.Research on dynamic change characteristics and influencing factors of carbon emission from iron ore waste mixed soil can provide theoretical and practical guidance for rational utilization of tailings resources,ecological restoration of land,and practice of low-carbon emission reduction in the research area. |
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