# Preliminary Evidence of Exogenous Hydrogen Peroxide Formation via Plant Transpiration: Toward a Nature-Based Solution for Air Quality and Climate Mitigation

## TL;DR

Plants may produce hydrogen peroxide through transpiration, offering a new natural way to improve air quality and combat climate change.

## Contribution

This study provides the first evidence that plants can generate exogenous hydrogen peroxide via transpiration and condensation.

## Key findings

- Hydrogen peroxide concentrations of 1–5 ppm were detected near leaf surfaces under transpiration and light conditions.
- H2O2 production was distance-dependent, with minimal levels beyond 40 cm from leaves.
- No H2O2 was detected in controls without plants or under dark conditions.

## Abstract

Plants play critical roles as nature-based solutions to maintaining air quality and regulating biogeochemical cycles, yet the mechanisms underlying these complex systems remain poorly understood. Hydrogen peroxide (H2O2), a globally present atmospheric oxidant, shows well-documented diurnal variation, but no direct link to plant transpiration has previously been reported. This study aimed to determine whether plants can produce exogenous H2O2 through transpiration and condensation, thereby revealing a novel pathway by which plants influence proximal and potentially global atmospheric chemistry. To investigate this, we examined a natural plant system undergoing photosynthesis and transpiration; our work was inspired by recent laboratory findings where spontaneous H2O2 was generated during the condensation of water vapour into microdroplets in engineered systems. Condensed water collected near leaf surfaces revealed H2O2 concentrations of 1–5 ppm, verified using both commercial peroxide test strips and spectrophotometric titration. Importantly, H2O2 production occurred only under light conditions when plants were transpiring, while controls without plants or without light showed no detectable levels. A strong distance-dependence was also observed, with minimal to no H2O2 detected beyond 40 cm from leaves. These findings suggest that plant-driven formation of water vapour and subsequent condensation produces measurable H2O2, establishing a previously unrecognized mechanism with implications for air quality improvement, atmospheric oxidation processes, and climate change modelling and mitigation.