Phosphorus cycling through phosphine in paddy fields

Phosphine emission fluxes from paddy fields, phosphine ambient levels in ai r, and the vertical profile of matrix-bound phosphine in soil have been mea sured throughout the growing season of rice in Beijing, China. It was found that both the seasonal and diurnal emission fluxes and ambient levels fluc tuate significantly. During the drainage period, phosphine released from th e soil with the highest diurnal average flux on the first period of drainag e (approx, 17.7 ng m(-2) h(-1)), whereas its highest ambient level (approx. 250 ng m(-3)) occurred at 06.00 h. During the flooded period, phosphine em ission was low, and the peaks of phosphine emissions occurred at midnight. The average Bm ol PH3 emission for the whole season was found to be approxi mately 1.78 ng m(-2) h(-1). The mais fraction of matrix-bound phosphine is approximately 0.18 similar to 1.42 X 10(-7) (m/m) part of organic phosphoru s or 3.4 similar to 9.2 x 10(-9) (m/m) part of total phosphorus in paddy so il. The amount of phosphine emitted to the atmosphere was only a small frac tion of the phosphine that remained in the soil in the matrix-bound form. S oil serves both as the source and the sink of PH3. (C) 2000 Elsevier Scienc e B.V. All rights reserved.