Phosphine in the Urban Air of Beijing and Its Possible Sources

Abstract

Both as an air pollutant and as a gaseous component of the local phosphorus cycle, phosphine (PH3) was found in the urban air of Beijing. Other possible sources, like paddy fields and water reservoirs, were selected for testing the hypothesis of the biological phosphine formation. Phosphine in the urban air of Beijing was measured in different seasons. In the summertime phosphine levels typically peak in the early morning and then decline towards noon. The maximum concentration at 6.00 am was 65 ng m−3 whilst that at noon was 11 ng m−3. In spring and in wintertime, the phosphine levels in the urban air of Beijing were lowest. A first screening revealed phosphine also in gas and in sediment samples from a paddy field near Beijing, the Beijing Shisanling water reservoir, and the refuse tips Changping of Beijing as well as in the ambient air adjacent to these sampling sites. The maximum phosphine concentrations in these gas samples were 41 (marsh gas, paddy field), 135 (marsh gas, reservoir), 1062 (landfillgas) ng m−3, and in the ambient air samples 146 (air, paddy field), 166 (air, reservoir), and 71 (air, refuse tips) ng m−3. In sediment samples, the highest matrix-bound phosphine levels were 13 (paddy field), and 3.9 (reservoir) ng kg−1. These comparatively high concentrations of the readily oxidizable phosphine in air indicate hitherto unknown but important phosphorus emission sources, which might reduce the biomass growth in Chinese fields and forests by a general phosphorus limitation. Phosphine is also a constituent of the air pollution in China. However, more work has to be done to evaluate the different sources of atmospheric phosphine.