LOSS OF ORGANIC-MATTER FROM RIVERINE PARTICLES IN DELTAS

In order to examine the transport and burial of terrigenous organic ma tter along the coastal zones of large river systems, we assessed organ ic matter dynamics in coupled river/delta systems using mineral surfac e area as a conservative tracer for discharged riverine particulate or ganic matter (POM). Most POM in the rivers studied (n = 6) is tightly associated with suspended mineral material; e.g., it is sorbed to mine ral surfaces. Average organic loadings in the Amazon River (0.67 +/- 0 .14 mg C m(-2)), the river for which we have the lar est dataset, are approximately twice that of sedimentary minerals from the Amazon Delta (similar to 0.35 mg C m(-2)). Stable carbon isotope analysis indicate that approximately two-thirds of the total carbon on the deltaic part icles is terrestrial. The combined surface-normalized, isotope-disting uished estimate is that >70% of the Amazon fluvial POM is not buried i n the delta, consistent with other independent evidence (Aller et al., 1996): Losses of terrestrial POM have also been quantified for the ri ver/delta systems of Columbia in the USA, Fly in New Guinea, and Huang e-He in China. If the losses of riverine POM observed in these river/d elta systems are representative of rivers worldwide, then the surface- constrained analyses point toward a global loss of fluvial POM in delt a regions of similar to 0.1 x 10(15) g C y(-1). Copyright (C) 1997 Els evier Science Ltd.