Soil erosion and sediment sources in an Ohio watershed using beryllium-7, cesium-137, and lead-210.
Soil cores and suspended sediments were collected within the Old Woman Creek, Ohio (OWC) watershed following a thunderstorm and analyzed for 7Be, 137Cs, and 210Pb activities to compare the effects of till vs. no-till management on soil erosion and sediment yield. The upper reaches of the watershed draining tilled agricultural fields were disproportionately responsible for the majority of the suspended sediment load compared with lower in the watershed (2.0-7.0 metric tons/km2 [Mg/km2] vs. 1.2-2.6 Mg/km2). About 6 to 10 times more sediment was derived from the subbasins that are predominantly tilled (6.8-12.4 Mg/km2) compared with the subbasins undergoing no-till practices (0.5-1.1 Mg/km2). In undisturbed soils the 210Pb activities decreased with movement toward the bottom of the cores to the constant supported 210Pb value at a depth of about 10 cm. There was a subsurface maximum in 137Cs activity within the top 10 cm. In contrast, the 210Pb and 137Cs distributions in soils that are currently or were previously tilled were nearly homogeneous with depth, reflecting continuing or previous mixing by plowing. The activities of 210Pb and 7Be were linearly correlated and were higher in suspended sediments derived from no-till subbasins than those derived from tilled subbasins, indicating that the soil surface is the source of suspended sediment. This study demonstrates that no-till farming results in decreases in soil erosion and decreases in suspended sediment discharges and that those eroded sediments have a radionuclide signature corresponding to the tillage practice and the depth of erosion.
Matisoff
Gerald
G
Department of Geological Sciences, Case Western Reserve University, Cleveland, OH 44106, USA. gxm4@po.cwru.edu
Bonniwell
Everett C
EC
Whiting
Peter J
PJ
D000383:Agriculture; D001608:Beryllium / Q000032:analysis*; D002588:Cesium Radioisotopes / Q000032:analysis*; D003247:Conservation of Natural Resources; D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments / Q000737:chemistry*; D007856:Lead Radioisotopes / Q000032:analysis*; D011868:Radioisotopes / Q000032:analysis*; D012987:Soil; D014872:Water Movements; D014873:Water Pollutants; D014875:Water Pollutants, Radioactive / Q000032:analysis*
D002588:Cesium Radioisotopes; D007856:Lead Radioisotopes; D011868:Radioisotopes; D012987:Soil; D014873:Water Pollutants; D014875:Water Pollutants, Radioactive; D001608:Beryllium