Moisture effects on carbon and nitrogen emission from burning of wildland biomass
1Division of Atmospheric Sciences, Desert Research Institute, Reno, NV 89512, USA
2Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, NV 89512, USA
3Division of Hydrological Sciences, Desert Research Institute, Reno, NV 89512, USA
Abstract. Carbon (C) and nitrogen (N) released from biomass burning have multiple effects on the Earth's biogeochemical cycle, climate change, and ecosystem. These effects depend on the relative abundances of C and N species emitted, which vary with fuel type and combustion conditions. This study systematically investigates the emission characteristics under different fuel moisture contents, through controlled burning experiments with biomass and soil collected from a typical alpine forest. Fuel moisture in general lowers combustion efficiency, shortens flaming phase, and introduces prolonged smoldering before ignition. It increases emission factors of incompletely oxidized C and N species, such as carbon monoxide (CO) and ammonia (NH3). Substantial particulate carbon and nitrogen (up to 4 times C in CO and 75% of N in NH3) were measured mainly from the pre-flame smoldering of fuels with high moisture contents; this process emits particles larger than soot agglomerates commonly observed in flaming smoke. Hydrogen (H)/C ratio and optical properties of particulate carbon from the high-moisture fuels show their resemblance to plant cellulous and brown carbon, respectively. These findings have implications for modeling biomass burning emission and impacts.