137Cs and 210Pb 在土壤侵蚀中的应用.pdf

Geomorphology 119 (2010) 88–96 Contents lists available at ScienceDirect Geomorphology j ourna l homepage: www.e lsev ie / locate /geomorph137Cs and 210Pb derived sediment accumulation rates and their role in the long-term development of the Mkuze River floodplain, South Africa Marc S. Humphries a,?, Andrew Kindness a, William N. Ellery b,c, Jeffrey C. Hughes b, Claudia R. Benitez-Nelson d a School of Chemistry, University of KwaZulu-Natal, Private Bag X54001, Durban, 4000, South Africa b School of Environmental Sciences, University of KwaZulu-Natal, South Africa c Department of Environmental Science, Rhodes University, Grahamstown, 6140, South Africa d Department of Earth and Ocean Sciences, University of South Carolina, Columbia. SC 29208, USA? Corresponding author. Tel.: +27 312603090; fax: + E-mail address: marchump@ (M.S. Hump 0169-555X/$ – see front matter ? 2010 Elsevier B.V. A doi:10.1016/j.geomorph.2010.03.003a b s t r a c ta r t i c l e i n f oArticle history: Received 27 September 2009 Received in revised form 1 March 2010 Accepted 2 March 2010 Available online 7 March 2010 Keywords: Floodplain wetland Pb-210 Cs-137 Sedimentation ratesWetlands are well known to act as sinks for sediment and chemicals in the landscape. Within the Mkuze River floodplain in northern KwaZulu-Natal, South Africa, deposition of clastic sediment occurs predominantly in close proximity to the river channel, resulting in the formation of levees. Over time, this leads to channel avulsion, a process that may be accelerated by the activities of hippopotami whose trails create hydraulically favourable pathways. Sedimentation rates, determined using the isotopes 210Pb and 137Cs, indicate that the Mkuze River floodplain is a relatively rapidly aggrading system that should experience frequent avulsion, with average short-term rates in the order of 0.25 to 0.50 cm/y. Sediments on the floodplain are also an important sink for solutes, which concentrate in the groundwater and precipitate ou