Black Carbon In Forest Soils In The Western Great Xing’an Mountains Distribution Characteristics And Determination Method

Forest soil black carbon research on forest ecosystem carbon library and carbon sinks function evaluation is important. The temperate coniferous forest region in the north of Great Xing’ an Mountains and the forest steppe zone of transition in the western slope as the area of fires strong interference, its soil black carbon needs special attention. In this paper, we choose the forest steppe zone of transition of Great Xing’an Mountains western slope (grey wooded soil) as the object, through sample to sample for soil samples, adopt the HF/HCl acid treatment- potassium dichromate oxidation method commonly used at home and abroad for the separation and determination of soil black carbon, systematic study on the overall number of characteristics and regional distribution of soil black carbon. At the same time, in view of the characteristic of soil black carbon of Great Xing’an Mountains forest region exists mainly by grain charcoal (carbon dust) form, the shallow weathering degree of soil, the low content of clay minerals, take the HF/HCl acid treatment-potassium dichromate oxidation method which commonly used at home and abroad for reference, through the design of different acid treatment schemes, acid treatment process was studied on measurement results of soil black carbon, discusses the feasibility of greatly simplify the experimental steps.The main results are as follows:(1) Overall quantity and distribution characteristics of soil black carbonSoil black carbon content in the study area range from 2.10 to 16.71 g·kg-1, there is great difference between different layers. Black carbon content in the soil surface is the highest, and decrease with soil depth gradual increase.0 to 40 cm soil layer of black carbon reserves accounted for over 80% of the profiles of black carbon, surface convergence phenomenon obviously. The ratio of black carbon to total soil organic carbon (BC/SOC) roughly between 15% and 25%, increased with the soil depth increase. BC content in soil and soil total organic carbon (SOC) content is a very significant positive correlation.Most of the soil black carbon content of the dark gray forest soil every soil layer were significantly higher than gray wooded soil, and every soil layer and the full profile of black carbon density were higher than gray wooded soil. However, each soil layer BC to SOC ratio had no significant difference. Gray wooded soil and dark gray forest soil downslope soil black carbon content were higher than upslope corresponding soil layer. Gray wooded soil and dark gray forest soil downslope each soil layer of black carbon content higher than upslope. Gray wooded soil and dark gray forest soil downslope every soil layer and the whole profile of the black carbon density were significantly higher than upslope The difference degree of gray wooded soil upslope and downslope BC density higher than dark gray forest soil. Gray wooded soil and dark gray forest soil downslope every soil layer BC to SOC ratio were significantly higher than the upslope.Because the dark gray forest soil distribute in the shady slope, the difference with aspect of slope in involves only a subclass of gray wooded soil types. Grey wooded soil shady slope every soil layer black carbon content were lower than the trend of the adret, including 10 to 20, 20 to 40 cm soil reached significant level. Every soil layer BC to SOC ratio and density of black carbon in the shady slope mostly below than the adret.(2) The determination method of soil black carbonThe effect of HF/HCl acid treatment process on measurement of soil black carbon: HF/HCl acid treatment-potassium dichromate oxidation method is the commonly used method of separation and determination of soil black carbon at home and abroad, but the method steps are complex, time-consuming, laborious, and many times centrifugal cleaning in the process of the experiment is very easy to cause the error. Research Findings, for Great Xing’an Mountains forest soil, treat the HF/HCl acid treatment process as a whole, black carbon content of the method without the acid treatment is higher than that of conventional acid treatment, but two plans measured numerical difference is not significant, and consider that increasing the experimental steps not only causes reagent and time waste, also will increases the experimental error, so relatively omitting HF/HCl acid treatment process and using potassium dichromate oxidation method directly separation and determination of soil black carbon seem to be more desirable. Three kinds of surface soil samples was separated and measured with seven different kinds of HF/HCl acid treatment plans, there is a significant difference between seven plans measured BC content; compare the differences between the acid treatment scheme, found that the acid treatment there is very great variability in each step, the value of omitting acid treatment method relative to the acid treatment measurements value is smaller variation, it is suitable to determine black carbon rule in different regions.And under the condition of omitting HF/HCl acid process, and compared with the appropriate concentration of oxidant (0.1M K2Cr2O7/2M H2SO4, v:v=1:1), the black carbon content used in high concentrations of potassium dichromate (0.1M K2Cr2O7/2M H2SO4) is significantly reduced. Therefore, choosing the appropriate K2Cr2O7/H2SO4 concentration is very important.At the same time, the study found that in the HF/HCl acid treatment and K2Cr2O7/H2SO4 oxidation process, ultrasonic treatment help BC and active organic carbon separation more thoroughly, improve the accuracy of analysis results.