Orographic and convective precipitation control meteoric 10Be wet depositional fluxes at low latitude

Meteoric beryllium-10 (¹⁰Be_m) is a valuable tracer for investigating land surface processes, and numerous studies have used it to assess soil ages and residence time, date sedimentary archives and quantify soil erosion rates at the hillslope and catchment scales. The flux of ¹⁰Be_m to the Earth's surface is influenced by e.g. solar activity, the Earth’s magnetic field, stratosphere-troposphere exchange dynamics and atmospheric circulation patterns that control ¹⁰Be_m production, transport, and deposition.

The control of precipitation on the flux of ¹⁰Be_m to Earth’s surface remains unclear at low latitude, where there is little observational data available. To study the impact of precipitation on deposition of ¹⁰Be_m at low latitude, we determined ¹⁰Be_m concentrations in rainwater along a 10-fold precipitation gradient on Santa Cruz Island in the Galápagos Archipelago (Ecuador) over one meteorological year. To elucidate spatial and temporal variations in ¹⁰Be_m concentrations, rainwater was collected at five sites spanning the precipitation gradient during the cool and warm seasons.

Our findings reveal a rise in ¹⁰Be_m deposition rates with precipitation that exceeds a linear increase, indicating a super-additive effect of precipitation on ¹⁰Be_m deposition. We attribute this to the presence of an inversion layer on Santa Cruz Island during the cool season, which limits atmospheric mixing. Furthermore, we observed a clear decline in ¹⁰Be_m concentrations with increased convective precipitation during the warm and rainy season. This suggests a dilution effect on atmospheric ¹⁰Be_m deposition during intense precipitation events. Our study highlights the spatial variability of ¹⁰Be_m deposition along a precipitation gradient and deepens understanding of how different types of precipitation influence ¹⁰Be_m fluxes.