Hydrodynamic sorting and transport of terrestrially derived organic carbon in sediments of the Mississippi and Atchafalaya Rivers

摘要: Abstract Over the course of two years, four cruises were conducted at varying levels discharge in lower Mississippi and Atchafalaya Rivers (MR AR) where grab samples collected from sand- mud-dominated sediments. The tetramethylammonium hydroxide (TMAH) thermochemolysis method was used to determine sources terrestrially derived organic carbon (OC) these sediment types, examine effects hydrodynamic sorting on lignin river Average concentrations MR 1.4 ± 1.1 mg gOC −1 English Turn (ET) 10.4 ± 27.4 mg gOC Venice. Using concentrations, annual fluxes Gulf Mexico, tidal estuarine mud remobilization ET Venice, 3.1 ± 2.5 × 10 5  kg 11.4 ± 30.0 × 10  kg, respectively. Much lignin-derived materials muddy sediments appeared be non-woody grass-like – which should decay more quickly than woody typically found sandy deposits. average total OC% (1.93 ± 0.47) sands yields an flux 0.34 ± 0.09 × 10 9  kg. Lignin (3.6 ± 2.6 mg gC ) using numbers above would 12.2 ± 9.4 × 10 extensive amounts sand-sized (coffee-grinds) both AR are likely plant materials. This is first time it has been demonstrated that provide equally important pathway (compared muds) for transport matter northern Mexico. %OC sand (1.16 ± 0.72), we estimated OC shelf 0.13 ± 0.07 × 10 12.4 ± 12.1 × 10 Despite high error associated with numbers, observe Mexico comparable MR. These results further support likelihood grain-size related Rivers, suggesting there a distinct fraction contributed by major rivers global cycle.