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Agricultural Erosion Indicated by 137Cs Redistribution: I. Levels and Distribution of 137Cs Activity in Soils
Author(s) -
Brown R. B.,
Cutshall N. H.,
Kling G. F.
Publication year - 1981
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1981.03615995004500060035x
Subject(s) - erosion , transect , hydrology (agriculture) , soil water , sedimentary depositional environment , environmental science , surface runoff , plough , sediment , tracer , deposition (geology) , floodplain , alluvium , geology , soil science , geomorphology , geography , archaeology , ecology , oceanography , physics , geotechnical engineering , cartography , structural basin , nuclear physics , biology
Modern agricultural erosion was studied using 137 Cs fallout as an indicator of erosion and sedimentation in the hilly margin of the Willamette Valley, Ore. Objectives of this phase of the study were (i) to identify areas most severely eroded over the period of fallout (since early 1954), and (ii) to identify areas that had been subject to net deposition over the same period. Along each of eight transects, sampling sites were selected in ridgetop, steep sideslope, and concave footslope positions. Also sampled were a single convex ridge shoulder, a high ridgetop, two alluvial fans, two floodplain sites, and two sites in an 8‐year‐old pond. Soil cores were collected at each site and analyzed by depth increment for 137 Cs activity. Depth distribution patterns of 137 Cs activity suggested that fallout 137 Cs was retained in surface soils and was, therefore, a good tracer in erosion/sediment studies. Depositional sites tended to have overthickened 137 Cs profiles and high total contents of 137 Cs. Average total 137 Cs activity in depositional sites was about 12 pCi/cm 2 . Sideslopes and ridgetops, with average total 137 Cs activities of about 8 pCi/cm 2 , were indistinguishahle from each other. Failure to distinguish sideslopes from ridgetops based on 137 Cs signature was attributed to (i) widespread runoff from these lands, (ii) damping effects of plowing and continuing input of fallout 137 Cs, and (iii) an apparent lack of erosion severe enough to have depleted preferentially the 137 Cs‐rich surface soils of sideslopes.