Suspended sediment sources and transport distances in the Yellowstone River basin

Abstract

The activity of fallout radionuclides ( 7 Be, 137 Cs, and 210 Pb) was measured on upland and fl oodplain soils and on suspended sediments to quantify sources of fi ne sediment and to estimate sediment transport distances in stream channels in the Yellowstone River basin. Samples were collected seven times during snowmelt and runoff at nine locations from the headwaters of Soda Butte Creek to Billings, Montana, a 423-km-long reach of channel. The inventory of radionuclides in soil increases with precipitation and is highest in the headwaters. The activity of radionuclides in suspended sediment decreases downstream, and more activity is observed earlier than later in the fl ood hydrograph.The radionuclide activity of sediment derived from erosion of upland soils differs from that derived from bank erosion. Fine suspended sediment has an intermediate radionuclide signature that is quantifi ed in terms of the relative contribution of these two sources of fi ne sediment. At sites high in the drainage, soils contribute 50% to the suspended load and this value decreases to 11%-26% downstream. Fine sediment transport distances were calculated from the exponential decrease in radionuclide concentration below a point source. Transport distances increase from a few kilometers in the headwaters to hundreds of kilometers downstream. These estimates are consistent with transport distances estimated from the settling velocity of the particles and from the distribution of mine tailings downstream from a dam failure. This study of a large watershed confi rms earlier results from smaller basins and suggests that transport distances increase with basin size.

Surficial redistribution of fallout131iodine in a small temperate catchment

“…We demonstrate that these zones, even in low-order streams, may sequester significant quantities of fine particulate material, contaminants, and nutrients (33). The continuous processes of fluvial redistribution in small catchments are, in turn, important in supplying organic material (34,35,36) and soil carbon (37,38) to larger river systems, lakes, wetlands, and estuaries (39,40). By extrapolation the same may be expected of iodine (41,42,4).…”

“…By extrapolation the same may be expected of iodine (41,42,4). To the extent that iodine remains particle-bound during long-term cycling in the soil system, its continued removal from a landscape will follow mechanisms and time scales of soil erosion previously described using 7 Be, 210 Pb, and 137 Cs radionuclide tracers (43,38,44). However, the active focusing of iodine to surface soils, likely mediated by microbial activity, may enhance the susceptibility of iodine to surficial transport relative to other tracers.…”

An investigation on suspended solids sources in urban stormwater runoff using 7Be and 210 Pb as tracers

“…Several studies used the above radionuclides as tracers to identify the fingerprint characteristics in sediment erosion sources from agricultural watersheds (Walling et al 1999;Matisoff et al 2005;Whiting et al 2005).…”

Fine sediment sources in Conservation Effects Assessment Project watersheds

“…The theory behind the method is detailed by Matisoff et al (2005), Whiting et al (2005), and Wilson et al (2008a). The method utilized the activities of two naturally occurring radioisotopes, Beryllium-7 ( 7 Be) and Pb xs ) , as tracers and a simple two end-member mixing model.…”