MOdern River archivEs of Particulate Organic Carbon: MOREPOC

Abstract

Abstract. Riverine transport of particulate organic carbon (POC) associated with terrigenous solids to the ocean has an important role in the global carbon cycle. To advance our understanding of the source, transport, and fate of fluvial POC from regional to global scales, databases of riverine POC are needed, including elemental and isotope composition data from contrasted river basins in terms of geomorphology, lithology, climate, and anthropogenic pressure. Here, we present a new, open-access, georeferenced, and global database called MOdern River archivEs of Particulate Organic Carbon (MOREPOC) version 1.1, featuring data on POC in suspended particulate matter (SPM) collected at 233 locations across 121 major river systems. This database includes 3546 SPM data entries, among them 3053 with POC content, 3402 with stable carbon isotope (δ13C) values, 2283 with radiocarbon activity (Δ14C) values, 1936 with total nitrogen content, and 299 with an aluminum-to-silicon ratio (Al / Si). The MOREPOC database aims at being used by the Earth system community to build comprehensive and quantitative models for the mobilization, alteration, and fate of terrestrial POC. The database is made available on the Zenodo repository in machine-readable formats as a data table and GIS shapefile at https://doi.org/10.5281/zenodo.7055970 (Ke et al., 2022).

Low But Persistent Organic Carbon Content of Hyperarid River Deposits and Implications for Ancient Mars

“…The median of global suspended sediment TOC was 1.24% and the median of global bank sediment TOC was 1.0%. This is consistent with larger grain sizes (found in bar sediments as opposed to suspended particles and overbank deposits) having lower amounts of OC (Bianchi et al, 2007;Ke et al, 2022;Stecko & Young, 2000). The Amargosa River bank contained on average 0.15 ± 0.09% (n = 28) organic carbon.…”

“… (a) Histogram with global suspended sediment TOC dataset from MOREPOC (Ke et al., 2022). (b) Histogram overlaid of bank sediment TOC measurements compiled in a global dataset for this study (both are normalized as probability distribution functions).…”

“…Figure 6 compares the Amargosa bank sediment TOC values to the global dataset of bank sediment TOC values (compiled for this study, data in Table S2) and the global suspended sediment TOC compiled by Ke et al (2022). For suspended TOC, only 85 points were more than 20%.…”

“…Organic carbon is better preserved at locations with rapid sedimentation or saturated pore waters because the molecules are exposed to oxygen for a shorter period of time (Hartnett et al., 1998). Mineral‐bound organic carbon is able to persist for millennia compared to free organic carbon in oxygenated environments, especially with smaller grain sizes due to greater surface area (Bianchi et al., 2007; Hemingway et al., 2019; Ke et al., 2022; Stecko & Young, 2000). Redox availability and mineral catalysts have the opposite effect, accelerating microbial degradation of organic matter (Kleber et al., 2021).…”

“…Rivers transport significant amounts of inorganic carbon as particles and are dissolved in the water column. Particulate organic carbon (POC) associated with sediment in active suspended fluvial transport on Earth typically contains 1%–2% OC with some outliers up to 90% (Ke et al., 2022). Though OC content is typically higher in finer grained sediments, many other factors such as precipitation, tectonics, and temperature impact OC loading.…”