Insights into the provenance implication of leaf wax n-alkanes along the lower Yellow River

Serving as one of the largest rivers in terms of both sediment and organic carbon transport fluxes in the world, the Yellow River plays a crucial role in regional biogeochemical process as well as in the global carbon cycle. However, although a large number of studies have been carried out on the flux, composition, source and seasonal variation of total particulate organic carbon in the Yellow River so far, studies on molecular biomarkers at different spatial and temporal scales are still scarce. In this study, we focus on the molecular and hydrogen isotopic properties of leaf wax n-alkanes among different types of samples which obtained from different seasons (flood vs. non-flood) along the lower Yellow River. The molecular distribution of n-alkanes show that the riparian topsoils are subject to inputs from the overlying vegetation, while the suspended sediments from the flood season are characterized by the mixing of soil materials which originate from various stratigraphy with different ages on the Chinese Loess Plateau. Due to the contrasting hydrodynamic conditions, the n-alkanes in suspended sediments also show distinct molecular composition between flood and non-flood seasons. Additionally, considering the effect of climatic factors, the proportion of monocots in flood-season suspended sediments is calculated from a semi-quantitative perspective using δ²H_wax. Our findings may bring to light new considerations for the interpretation of leaf wax proxies in studies of organic matter sources of Yellow River.