Tracing Organic Carbon Sources With Ramped Pyrolysis/Oxidation

Tracing sources of organic carbon (OC) is a critical aspect of studying surface carbon cycling. Previous methods, such as carbon and nitrogen isotopes, have struggled to separate different sources in some case studies. This study introduces a new approach for quantifying OC sources by using ramped pyrolysis/oxidation (RPO) thermograms without RPO-fraction radiocarbon analysis. We applied matrix calculations to decompose thermograms into different endmembers contributions. This method was tested on two-, three-, and four-endmember systems. The results show that the deviation in source contribution estimates is within 5%. The method was applied in tracing sources of particulate organic carbon (POC) of the Buha River, northeastern Tibetan Plateau. By analyzing the thermograms of riverine suspended sediments and their potential sources, the RPO-based mixing model estimated that soil, vegetation, and rocks contributed approximately 89 ± 3%, 4 ± 3%, and 6 ± 3% of the POC, respectively. This study highlights the applicability of RPO in tracing OC sources.