Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 51, Issue 23, Pages 13723-13732Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.7b04232
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Funding
- National Key Basic Research Program of China [2014CB441103]
- National Natural Science Foundation of China [21407073, 21622703]
- NSF ERC on Nanotechnology-Enabled Water Treatment [EEC-1449500]
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences [KF2014-11]
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The fluvial export of dissolved black carbon (DBC) is a major land-ocean flux in the global black carbon cycle, affecting the size of refractory carbon pool: in the oceans. The aggregation behavior of DBC is a significant determinant of its transport and vertical mass flux. In this study, the aggregation kinetics and interaction energy of DBC leached from biochar were investigated. DBC was mainly stabilized by hydration force and underwent structural compacting in divalent cation solutions. Na+ and me had limited impact on the colloidal stability of DBC due to the strong hydration of these cations. Ca2+ and Ba2+ readily destabilized DBC by forming inner-sphere complexes, reducing, its hydrophilicity. Consistently, charge reversal of DBC was observed with high concentrations of Ca2+ and Ba2+ Simulated sunlight exposure led to photo-oxidation of DBC, increasing its colloidal stability. DBC behaved nonconservatively in laboratory mixing experiments using estuary water samples due to aggregation/sedimentation; while model aquatic humic acid behaved conservatively. Our results infer that there is a vertical mass flux of DBC and possible fractionation from the dissolved organic matter pool in the fluvial and estuarine systems, which have been overlooked in efforts to determine global carbon budgets and associated climate change implications.
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