Sediment source variations and lead-210 inventories in recent Potomac Estuary sediment cores

AbstractAnthropogenic radionuclide signatures associated with nuclear testing are increasingly utilized in environmental science to explore recent sedimentation. In this study, we assess the suitability of Pu radioisotope analysis in floodplain lake environments in the Amazon Basin to form geochronologies during the 20thcentury. The240Pu +239Pu (240+239Pu) signatures in six sediment cores indicate sediment accumulation rates in the floodplain lakes of the major rivers; Amazon (2.3 mm year-1), Tapajos (10.2 and 2.4 mm year-1) and Madeira (3.4, 4.2 and 6.2 mm year-1). The results from this study show that240+239Pu fallout activities, and the well documented (240Pu/239Pu) atomic ratios of the above ground nuclear tests which began in the 1950’s, are sufficient and well preserved in Amazon floodplain lake sediments to infer chronologies. Lead-210 dating analyses in the same sediment cores produced comparable sediment accumulation rates at three of the six sites. The differences between dating methods may be attributed to the different time scale these dating methods represent and/or in the solubility between Pb and Pu along the sediment column. The geochronologies derived from the240+239Pu and210Pb dating methods outlined in this work are of interest to identify the effects of changing sediment accumulation rates during the previous century as a result of development, including deforestation, along the Amazon Basin which increased towards the middle of the 20thcentury. This study shows that Pu dating provides a viable alternative geochronology tool for recent sediment accumulation (previous ~60 years) along the Amazon Basin.

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Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

Hydrology and Earth System Sciences ◽

10.5194/hess-20-2295-2016 ◽

2016 ◽

Vol 20 (6) ◽

pp. 2295-2307 ◽

Cited By ~ 2

Author(s):

Matthew D. Berg ◽

Franco Marcantonio ◽

Mead A. Allison ◽

Jason McAlister ◽

Bradford P. Wilcox ◽

...

Keyword(s):

Sediment Yield ◽

Land Surface ◽

Sediment Cores ◽

Watershed Scale ◽

Landscape Changes ◽

Sediment Yields ◽

Dynamic Landscape ◽

Cesium 137 ◽

Lead 210 ◽

Runoff And Sediment Yield

Abstract. Rangelands cover a large portion of the earth's land surface and are undergoing dramatic landscape changes. At the same time, these ecosystems face increasing expectations to meet growing water supply needs. To address major gaps in our understanding of rangeland hydrologic function, we investigated historical watershed-scale runoff and sediment yield in a dynamic landscape in central Texas, USA. We quantified the relationship between precipitation and runoff and analyzed reservoir sediment cores dated using cesium-137 and lead-210 radioisotopes. Local rainfall and streamflow showed no directional trend over a period of 85 years, resulting in a rainfall–runoff ratio that has been resilient to watershed changes. Reservoir sedimentation rates generally were higher before 1963, but have been much lower and very stable since that time. Our findings suggest that (1) rangeland water yields may be stable over long periods despite dramatic landscape changes while (2) these same landscape changes influence sediment yields that impact downstream reservoir storage. Relying on rangelands to meet water needs demands an understanding of how these dynamic landscapes function and a quantification of the physical processes at work.

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Lead concentration profiles in lead-210 dated Lake Ontario sediment cores

The Science of The Total Environment ◽

10.1016/0048-9697(78)90057-8 ◽

1978 ◽

Vol 10 (2) ◽

pp. 117-127 ◽

Cited By ~ 7

Author(s):

John G. Farmer

Keyword(s):

Lead Concentration ◽

Sediment Cores ◽

Lake Ontario ◽

Concentration Profiles ◽

Lead 210

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Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

10.5194/hess-2015-540 ◽

2016 ◽

Author(s):

M. D. Berg ◽

F. Marcantonio ◽

M. A. Allison ◽

J. McAlister ◽

B. P. Wilcox ◽

...

Keyword(s):

Sediment Yield ◽

Land Surface ◽

Sediment Cores ◽

Watershed Scale ◽

Landscape Changes ◽

Sediment Yields ◽

Dynamic Landscape ◽

Cesium 137 ◽

Lead 210 ◽

Runoff And Sediment Yield

Abstract. Rangelands cover a large portion of the earth’s land surface and are undergoing dramatic landscape changes. At the same time, these ecosystems face increasing expectations to meet growing water supply needs. To address major gaps in our understanding of rangeland hydrologic function, we investigated historical watershed-scale runoff and sediment yield in a dynamic landscape in central Texas, USA. We quantified the relationship between precipitation and runoff and analyzed reservoir sediment cores dated using Cesium-137 and Lead-210 radioisotopes. Local rainfall and streamflow showed no directional trend over a period of 85 years, resulting in a rainfall-runoff ratio that has been resilient to watershed changes. Reservoir sedimentation rates generally were higher before 1963, but have been much lower and very stable since that time. Our findings suggest that (1) rangeland water yields may be stable over long periods despite dramatic landscape changes while (2) these same landscape changes influence sediment yields that impact downstream reservoir storage. Relying on rangelands to meet water needs demands an understanding of how these dynamic landscapes function and a quantification of the physical processes at work.

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A Multivariate Mixing Model for Identifying Sediment Source from Magnetic Measurements

Quaternary Research ◽

10.1016/0033-5894(89)90073-2 ◽

1989 ◽

Vol 32 (2) ◽

pp. 168-181 ◽

Cited By ~ 154

Author(s):

Lizhong Yu ◽

Frank Oldfield

Keyword(s):

Linear Programming ◽

Multiple Regression ◽

Magnetic Measurements ◽

Sediment Cores ◽

Mixing Models ◽

Sediment Source ◽

Sequential Method ◽

Source Component ◽

Quantitative Identification ◽

Quantitative Calculations

AbstractA sequential method for quantitative identification of sediment source components, based on magnetic measurements, has been developed and tested for sediments from the Rhode River, Maryland. Simulated mixing tests and multiple regression were employed to establish numerical relationships between source component proportions and the magnetic measurements of mixtures. On the basis of these multivariate mixing models, source components of three estuarine sediment cores were estimated by linear programming. The results strongly support the previous studies on this catchment which indicated a dramatic change in sediment source some 150 to 200 yr ago. Quantitative calculations are more useful and informative than purely qualitative descriptions.

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