Using Fallout Lead‐210 Measurements to Estimate Soil Erosion on Cultivated Land

Abstract

Naturally occurring fallout 210 Pb is strongly adsorbed by soils and sediments and has been widely used as a tracer to establish the chronology of deposited sediments in various sedimentary environments. This paper reports an attempt to explore the potential for using fallout 210 Pb to estimate rates of water‐induced soil erosion on cultivated land. Soil cores were collected from both cultivated and undisturbed areas in a small catchment in Devon, UK, and land use practices were shown to be the primary factor controlling the depth distribution of fallout 210 Pb. Based on existing knowledge of the behavior of 210 Pb in cultivated soils, a mass balance model has been developed that enables longer‐term (≈100 yr) rates of erosion and deposition to be estimated from values of unsupported 210 Pb inventory for individual sampling points. In order to estimate longer‐term soil redistribution rates, the mass balance model was applied to an 8.54‐ha cultivated field within the study catchment from which 167 bulk cores had been collected at the intersections of a 20 by 20 m grid. Soil redistribution rates within the field ranged from −5.9 kg m −2 yr −1 (erosion) to 6.4 kg m −2 yr −1 (deposition), and the mean erosion rate for the eroding area was 1.95 kg m −2 yr −1 The pattern of soil redistribution within the study field reflected the influence of topography on sediment mobilization and transport. The results obtained confirm the potential for using fallout 210 Pb measurements to estimate rates and patterns of water‐induced soil erosion on cultivated land.