土壤团聚体制备方法对其稳定性及固碳潜力评价的影响研究

为探讨不同土壤团聚体制备方法对评价城市土壤固碳潜力的影响,本研究采集北京市两种典型的不同利用类型土壤—城市绿地土壤和城郊农田土壤,分别采用干筛法和湿筛法制备土壤团聚体,对其团聚体组成、有机碳含量以及稳定碳同位素特征进行了解析.结果表明:干筛法制备的机械稳定性团聚体均以>0.25mm的大团聚体为主(城市绿地土壤:69.80%;农田土壤:71.36%);而湿筛法制备的水稳性团聚体均以<0.25mm微团聚体为主(城市绿地土壤:57.70%;农田土壤:52.14%).红外光谱解析发现,不同制备方法下,两类土壤中微团聚体中均是稳定有机碳比活性有机碳相对含量高;北京城郊农田土壤中稳定芳香碳的相对含量较多,而脂肪碳相对含量较少;城市绿地土壤则具有相反特征,说明城市绿地土壤中有机碳具有更高活性易在一定条件下被释放.结合稳定碳同位素比值解析发现,湿筛制备方法下¹³C在<0.053mm团聚体颗粒组中富集,更符合土壤团聚体胚胎发育模型,说明在土壤固碳潜力研究中,湿筛法比干筛法制备团聚体更具有实际评价价值,本研究为进一步评价我国城市土壤的固碳潜力具有参考意义.

Effects of soil aggregate preparation methods on the stability and carbon sequestration potential evaluation

To investigate the effects of different soil agglomerate preparation methods on the evaluation of agglomerate stability and its carbon sequestration potential, soils were collected from two typical land utilization types-urban road soils and suburban agricultural soils in Beijing. The soil aggregate was prepared by dry sieving and wet sieving methods, respectively, and its composition, organic carbon content and stable carbon isotope were analyzed. The mechanically stable aggregates prepared by the dry sieving method were dominated by the large (>0.25mm) aggregates (urban road soils:69.80%; agricultural soils:71.36%). In contrast, the water-stable aggregates prepared by the wet sieving method were dominated by the micro (<0.25mm) aggregates (urban road soil:57.70%; agricultural soil:52.14%). Infrared spectrum analysis showed that irrespective of the different preparation methods, the relative content of stable organic carbon in micro aggregates was higher than that of active organic carbon for the two types of soils. For the arable soil in the suburbs of Beijing, the relative content of stable aromatic carbon was more, while the relative content of fatty carbon was less. In the case of urban greening soil, the opposite characteristics can be observed, indicating that organic carbon in urban greening soil has higher activity and is easy to be released under certain conditions. Combined with the analysis of stable carbon isotope ratio, it is found that ¹³C is enriched in the aggregate particle group smaller than 0.053mm prepared by the wet sieve method, which is more fitted the soil aggregate embryo development model, indicating that the wet sieve method has more practical evaluation value than the dry sieve method in the study of soil carbon sequestration potential. This study has reference significance for further evaluating the carbon sequestration potential of urban soils in China.