Temporal and spatial distributions of phosphine in Taihu Lake, China

Abstract

Phosphine is a natural gaseous carrier of phosphorus in its geochemical cycles, and it might be of importance to the phosphorus balance of eutrophic lakes. Phosphine concentration levels in Taihu Lake, a typical shallow eutrophic lake in China, were intensely investigated in this work. Results show that in the period of 2002 the variation of phosphine concentration in the atmosphere near Taihu Lake is significant, with a maximum value 2.85 pg/l. Concurrent sampling of phosphine in surface and bottom water of the lake had no distinct change. The mean concentration of phosphine in the water ranged from 1.92 to 3.01 pg/l. Approximately 84–90% of the phosphine was removed from lake water during passage of the sample through a 0.45 μm pore size filter, i.e. the average phosphine concentrations of filtered lake water in all sampling locations were from 0.37 to 0.40 pg/l with the highest value 0.73 pg/l and the lowest 0.08 pg/l, whereas phosphine concentrations in unfiltered samples were 5–9 times higher. Phosphine levels in lake sediments were positively correlated with different contamination of the samples. The concentration levels of phosphine were also higher in severe polluted sites. The local average values of the phosphine concentrations were from 21 550 to 563 100 pg/kg. Its highest value was 919 238 pg/kg at 6# site (Zhihu harbor), a severely polluted sampling site.