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National Committee on Marine Sciences (NCMS)

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Author: search.filters.author.Lin, BaozhiHas files: No

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    Organic matter compositions and loadings in river sediments from humid tropical volcanic Luzon island of the Philippines
    Lin, Baozhi; Liu, Zhifei; Eglinton, Timothy I.; Blattmann, Thomas M.; Kandasamy, Selvaraj; Haghipour, Negar; Siringan, Fernando P. (American Geophysical Union, 2021-07)
    Tropical rivers deliver ∼60% of particulate organic carbon to the world ocean. However, compositions and loadings of sedimentary organic matter (OM) from tropical small mountainous rivers are largely unknown. Here, we provide an initial constrain on sources of sedimentary OM from 28 fluvial systems across Luzon in the Philippines by measuring total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ13C) and radiocarbon activity of TOC (expressed as fraction modern—Fm), as well as grain size and mineral surface area (SA) of sediments. Results indicate that sediments in Luzon rivers contain both contemporary and 14C-depleted OM (Fm: 0.71–1.06, mean 0.97 ± 0.07) with a wide range of δ13C values (−28.3‰ to −17.7‰, −24.9 ± 2.2‰). This is attributed to the OM sources originated from modern surface soil and 14C-depleted subsoil and deep soil vegetated by C3 and C4 plants, with mean fraction of C3 plant at 80% ± 11%. Minor input from bedrock may also contribute to the 14C-depleted OM in sediments, accounting for 6% ± 6%. Sediments in most rivers are featured by low OC loadings (OC/SA ratio < 0.4 mg C m−2), owing either to a less OM input or intensive OM degradation. The estimated yields of particulate OC from Luzon vary between 3.2 and 3.7 t km−2 yr−1, which is higher than most tropical large rivers.
    We thank Peter B. Zamora and Yulong Zhao for assistance during the fieldwork sampling, Daniel Montluçon, Yanli Li and all members of Ion Beam Physics Laboratory at ETH for technical and laboratory assistance, and Bingbing Wei for his help during preparation of this manuscript. This work was supported by the National Natural Sciences Foundation of China (Grant Nos. 41530964 and 91528304), the Swiss National Science Foundation (200020_163162) and the fellowship of China Postdoctoral Science Foundation (2020M671198). BL thanks the China Scholarship Council (20170260239) for the support during her stay at ETH Zürich (Switzerland).