Matrix-bound phosphine in paddy fields under a simulated increase in global atmospheric CO2

Abstract

Environmental context. Although phosphine (PH3) is an important gaseous carrier in the phosphorus cycle, its production and environmental behaviour remain unclear. Paddy fields are thought to be one of the main sources responsible for the production and emission of PH3. Understanding the behaviour of PH3 in paddy fields under elevated CO2 concentration is crucial in understanding the phosphorus cycle and its response to rising global atmospheric CO2 concentration. Abstract. The behaviour of matrix-bound phosphine (MBP) in paddy fields under elevated [CO2] (ambient + 200 μmol mol–1) is investigated to understand the soil phosphorus cycle and its link to increasing global atmospheric [CO2]. MBP concentrations range from 17.0 ± 5.8 to 1035 ± 331 ng kg–1. Concentrations at the transplanting and harvest stages are significantly higher than during the growing stages. The MBP level (212 ± 61 ng kg–1) under elevated [CO2] is slightly higher than under ambient [CO2] (189 ± 44 ng kg–1). Root exudates and addition of inorganic phosphate fertiliser speed up the production of MBP, whereas fast paddy growth and increasing air temperature accelerate the emission of MBP into the atmosphere. Significant positive correlations are found between MBP and inorganic phosphorus and organic matter, indicating that MBP may be produced from the microbial reduction of inorganic phosphorus in paddy fields.