Novel Insights Into the Molecular Characteristics of Dissolved Organophosphorus in Biomass Burning Smoke: Implication on the Environmental Stability and Cycling of Atmospheric Organophosphorus

Abstract With increasing wildfire and crop residue burning, organic P in biomass burning smoke‐derived dissolved organic matters (BBS‐DOMs), as an important source of atmospheric P, plays a growingly crucial role in P cycling on the Earth's surface. However, the limited understanding of the molecular characteristics of this organic P hampers our ability to comprehend its environmental stability and cycling processes. To address this knowledge gap, this study synthesized various BBS‐DOMs and used FT‐ICR‐MS to analyze their molecular characteristics and potential environmental stabilities. Herein, CHOP compounds (the capital letters in these compound names indicate their elemental compositions) were the dominant organic P component in most BBS‐DOMs, followed by CHONP and CHONSP compounds. However, high content of N in biomass enabled CHONP compounds to become the primary component during the burning process. Furthermore, CHOP compounds exhibited higher polarity and aliphaticity, lower molecular mass and aromaticity than CHONP and CHONSP compounds. Among these compounds, CHOP compounds predominantly existed as hydrolysis‐available P (phosphate esters with three P‐O‐C/H groups), accounting for >76% of the total organic P. Differently, CHONP and CHONSP compounds exhibited comparable oxidation‐available P (containing P‐C bond or incompletely oxidized P) and hydrolysis‐available P levels. These findings suggested that CHOP compounds had a lower environmental stability and shorter turnover cycle than CHONP and CHONSP compounds. Additionally, the (cellulose + hemicellulose)/lignin ratio of biomass and the burning temperature co‐regulated the aromatic degree and available state of organic P compounds in BBS‐DOMs. This study provides critical molecular‐level insights into the biogeochemical process of atmospheric P from biomass burning.