Phosphine in the urban air of Beijing and its possible sources

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 possib le sources, like paddy fields and water reservoirs, were selected for testi ng the hypothesis of the biological phosphine formation. Phosphine in the u rban air of Beijing was measured in different seasons. In the summertime ph osphine 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 Be ijing 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 fi eld), 135 (marsh gas, reservoir), 1062 (landfillgas) ng m(-3), and in the a mbient air samples 146 (air, paddy field), 166 (air, reservoir), and 71 (ai r, refuse tips) ng m(-3). In sediment samples, the highest matrix-bound pho sphine levels were 13 (paddy field), and 3.9 (reservoir) ng kg(-1). These c omparatively 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 pollutio n in China. However, more work has to be done to evaluate the different sou rces of atmospheric phosphine.