The presence of trace phosphine in Lake Taihu water

Phosphine (PH3) is a natural constituent in phosphorus (P) chemical cycles. The discovery of phosphine will shed new light on the mechanisms of P supplement and biogeochemical cycles. Since phosphine is converted to phosphate after complex oxidation via hypophosphite and phosphite, if it were present in the water column, understanding its production and emission could enhance our understanding of P speciation. Assuming that phosphine in the gas phase is an ideal gas and at equilibrium between water and gas interface, phosphine in water solution can be quantified from the equilibrated concentration in gas phase using the Henry's Law. Application of this approach to Lake Taihu, China, phosphine in unfiltered and filtered water samples (0.45 mu m) was analysed. Results showed that phosphine was universally present in Lake Taihu water. Phosphine concentration in unfiltered water ranged from 0.16 to 1.11 pg L-1, and was much less (0.01 to 0.04 pg L-1) in filtered samples. Over 90% of phosphine was adsorbed onto or incorporated into suspended materials with 510% dissolved in the water. Higher phosphine concentrations could be observed in warm seasons. Positive relationships were found between PH3 and TP (average R-2 = 0.59 +/- 0.22) and TSP (average R-2 = 0.37 +/- 0.13).