DOC sources and DOC transport pathways in a small headwater catchment as revealed by carbon isotope fluctuation during storm events

International audienceMonitoring the isotopic composition ( 13CDOC) of dissolved organic carbon (DOC) during flood events can be helpful for locating DOC sources in catchments and quantifying their relative contribution to stream DOC flux. Highresolution ( 2 ‰), and others yielding a very restricted range of values ( 80% of the stream DOC flux flows through the most superficial soil horizons of the riparian domain and (ii) the riparian soil DOC flux is comprised of DOC coming ultimately from both riparian and upland domains. Based on its 13C fingerprint, we find that the upland DOC contribution decreases from ca. 30% of the stream DOC flux at the beginning of the high-flow period to < 10% later in this period. Overall, upland domains contribute significantly to stream DOC export, but act as a sizelimited reservoir, whereas soils in the wetland domains act as a near-infinite reservoir. Through this study, we show that 13CDOC provides a powerful tool for tracing DOC sources and DOC transport mechanisms in headwater catchments, having a high-resolution assessment of temporal and spatial variability