Predicting the Fate of Sediment and Pollutants in River Floodplains
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- 作者：Daniel V. Malmon ; Thomas Dunne ; and Steven L. Reneau
- 刊名：Environmental Science & Technology
- 出版年：2002
- 出版时间：May 1, 2002
- 年：2002
- 卷：36
- 期：9
- 页码：2026 - 2032
- 全文大小：99K
- 年卷期：v.36,no.9(May 1, 2002)
- ISSN：1520-5851
文摘
Geological processes such as erosion and sedimentationredistribute toxic pollutants introduced to the landscape bymining, agriculture, weapons development, and otherhuman activities. A significant portion of these contaminantsis insoluble, adsorbing to soils and sediments after beingreleased. Geologists have long understood that much of thissediment is stored in river floodplains, which areincreasingly recognized as important nonpoint sources ofpollution in rivers. However, the fate of contaminatedsediment has generally been analyzed using hydrodynamicmodels of in-channel processes, ignoring particleexchange with the floodplain. Here, we present a stochastictheory of sediment redistribution in alluvial valley floorsthat tracks particle-bound pollutants and explicitly considerssediment storage within floodplains. We use the theoryto model the future redistribution and radioactive decay of137Cs currently stored on sediment in floodplains at theLos Alamos National Laboratory (LANL) in New Mexico.Model results indicate that floodplain storage significantlyreduces the rate of sediment delivery from upper LosAlamos Canyon, allowing 50% of the 137Cs currently residingin the valley floor to decay radioactively before leavingLANL. A sensitivity analysis shows that the rate of sedimentoverturn in the valley (and hence, the total amount ofradioactive 137Cs predicted to leave LANL) is significantlycontrolled by the rate of sediment exchange with thefloodplain. Our results emphasize that floodplain sedimentationand erosion processes can strongly influence theredistribution of anthropogenic pollutants in fluvialenvironments. We introduce a new theoretical frameworkfor examining this interaction, which can provide ascientific basis for decision-making in a wide range ofriver basin management scenarios.