River Basin Erosion Dynamics

Fallout Radionuclides (10Bem, 210Pbex, 10Bem (t1/2 = 1.39 myr) • • Atmospheric spallation reaction ~1.3 million atoms/cm² y-1 delivery rate Useful for assessing long-term erosion 210Pbex (t1/2 = 22.2 yr) • Naturally occurring as part of 238U decay series 1954-1963- 137Cs Carbon 226 Ra 222Rn. Fraction of total 210Pb in soil derived from 222 Rn gas that leaves soil Delivered back to soil through fallout 137Cs) 210pb Oxygen 7Be Cosmic rays Nitrogen Excess ph 210pb. Zupanc and Mabit, 2010 • • Integrates up to past 100 years of erosion 37Cs (t1/2 = 30.2 yr) Created from nuclear weapons testing in atmosphere Delivered to soil through fallout Only deposited globally from 1950's to 1970's Useful for assess erosion over past 50-60 years

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