Soil aggregates may stabilize carbon at mineral surfaces and in the interior, but resolving such micro-scale carbon (C) turnover at a scale of soil aggregates <2 mm is challenged by C contaminations during sample preparation such as from resin embedding. Here we introduce a novel C-free embedding method using silica gel for water glass formation, and applied it to soil aggregates from a C3/C4 vegetation change soil chronosequence (4, 10 and 19 years of Miscanthus cropping on former C3 soil) for subsequent δ¹³C and C turnover analyses using laser ablation isotope ratio mass spectrometry (LA-IRMS). We hypothesized that C-free embedding allows for the first time the comparison of C turnover at soil aggregates both in their center and at their outer surface. We found that using water glass embedding enabled δ¹³C analyses via LA-IRMS in all parts of the sample, free of any contaminations. There was a large micro-scale heterogeneity in δ ¹³C signals within aggregates, which increased with cropping duration (total range −5.5 to –41.5‰). Noteworthy, after 19 years Miscanthus materials were still found preferentially at soil aggregate surfaces and hardly in interior parts, documenting slow aggregate turnover but also success of the embedding technique for future micro-scale C dynamic analyses in environmental samples.

土壤团聚体可以稳定矿物表面和内部的碳，但是在小于2 mm的土壤团聚体规模下解决此类微型碳（C）转化问题受到样品制备过程中C污染（例如树脂包埋）的挑战。在这里，我们介绍了一种使用硅胶进行水玻璃形成的新型无碳包埋方法，并将其应用于C3 / C4植被变化的土壤时间序列（在以前的C3土壤上种植了4、10和19年的芒草）的土壤聚集体中，以便随后进行δ ¹³ C和C周转分析使用激光烧蚀的同位素比率质谱仪（LA-IRMS）。我们假设无碳嵌入技术首次允许比较土壤聚集体的中心和外表面的碳周转率。我们发现，使用水玻璃嵌入可启用δ通过LA-IRMS对样品的所有部分进行¹³ C分析，没有任何污染。有在δ大微尺度异质¹³ C信号聚集体内，其与裁剪的持续时间（总范围-5.5至-41.5‰）增加。值得注意的是，经过19年的研究，人们仍优先在土壤骨料表面发现了芒草材料，而在内部几乎没有发现芒草材料，这证明了骨料周转缓慢，但也成功地将包埋技术用于环境样品中未来的微尺度C动态分析。