# K isotopes trace temporal silicate weathering intensity

## TL;DR

Potassium isotopes in river water can track changes in silicate weathering intensity over time, offering a new tool to study Earth's climate and rock interactions.

## Contribution

The study establishes a new empirical relationship linking K isotope ratios to silicate weathering intensity using seasonal river data.

## Key findings

- K isotopes show strong seasonality due to aluminosilicate neoformation after silicate dissolution.
- An empirical relationship δ41Krw = −0.07 × ln(W/D) − 0.38 was derived to trace silicate weathering intensity.
- Riverine K isotopes can track temporal changes in silicate weathering intensity in the Chinese Loess Plateau.

## Abstract

Silicate weathering alters the biogeochemical compositions of the lithosphere, hydrosphere, and atmosphere, and thereby regulates both nutrient cycling and habitable temperatures on Earth, but tracing silicate weathering effectively remains a challenge. Potassium (K) isotopes have been proposed as a tracer of silicate weathering intensity spatially, but there is a significant gap in how and why K isotopes trace silicate weathering temporally. Here we investigate seasonal variations in dissolved K isotopes in the middle Yellow River, which drains a large area of homogeneous loess that represents the average geochemical composition of the upper continental crust, and experiences significant climatic seasonality driven by the East Asian monsoon. We find that K isotopes show strong seasonality as a function of aluminosilicate neoformation following silicate dissolution, and thus could serve as a tracer of silicate weathering intensity. We derive an empirical relationship of δ41Krw = −0.07 × ln(W/D) − 0.38, where W(silicate chemical weathering)/D(denudation) refers to silicate weathering intensity.

Seasonal variation in K isotopes of rivers that drain the Chinese Loess Plateau indicates that riverine K isotopes can trace changes in silicate weathering intensity over time, offering a tool to track Earth’s climate–rock interactions.