Deciphering the significant role of biological ice nucleators in precipitation at the organic molecular level

Abstract

Biological particles, as a fraction of organic particles, potentially play a crucial role in ice nucleation processes. However, the contributions and relationships of biological components and organic matter (OM) to atmospheric ice nucleation are still largely unexplored. Here, droplet freezing assays, high-throughput sequencing technology and ultrahigh-resolution mass spectrometry were performed to detect the INPs, microorganisms and OM molecules in precipitation collected at the summit of Mt. Lu, China, respectively. Results revealed a predominant biological composition (71.7% and 93.2%) of total and nanoscale INPs (< 0.22 μm) at temperatures above −15°C. Specifically, bacterial INPs accounted for 36.1% of the biological INPs at temperatures above −15°C. A notable correlation between sulfur-containing compounds, mainly proteinaceous and lignin-like substances, and INPs was uncovered, with a co-occurrence network linking these compounds to Gram-positive bacteria and Agaricomycetes. This study underscored the possible significance of sulfur-containing compounds in biological INP efficiency, which could further help shed light on the ice nucleation mechanisms and potential sources of biological INPs.