Simultaneous monitoring of phosphine and of phosphorus species in Taihu Lake sediments and phosphine emission from lake sediments

Phosphine (PH3) was monitored in the Taihu Lake in China by a GC/NPD method, coupled with cryo-trapping enrichment technology. Results showed that PH3 was universally detected in sediments, lake water and atmosphere of the Taihu Lake area. Total phosphorus ( TPs) and fractions of different phosphorus species in lake sediments were separately measured as dissolved phosphate (DP), phosphorus bound to aluminum (Al-P), iron (Fe-P) and calcium (Ca-P), occluded phosphorus (OP), and organic phosphorus (Org-P) by sequential chemical extraction. High PH3 levels were correlated with high TPs values in sediments and with eutrophication at different sites. In addition, a positive linear correlation equation was obtained between the concentrations of PH3 in lake sediments and of the phosphorus fractions. The resulting multiple linear regression equation is PH3 = - 165 + 63.3 DP + 0.736 Al-P + 2.33 Ca-P + 2.29 Org-P. The flux of PH3 across the sediment - water interface was estimated from sediment core incubation in May and October 2002. The annual average sediment - water flux of PH3 was estimated at ca. 0.0138 +/- 0.005 pg dm(-2) h(-1), the average yearly emission value of PH3 from Taihu Lake sediments to water was calculated to be 28.3 +/- 10.2 g year(-1), which causes a water PH3 concentration of up to 0.178 +/- 0.064 pmol dm(-3). The real importance of PH3 could be higher, because PH3 could be consumed in the oxic sediment - water boundary layer and in the water column. Spatial and temporal distributions of total phosphorus (TPw) and chlorophyll a (Chl-a) in the water column of Taihu Lake were measured over the study period. Higher water PH3 has also been found where the TPw content was high. Similarly, high Chl-a was consistent with higher water PH3. Positive relationships between PH3 and TPw (average R-2 = 0.47 +/- 0.26) and Chl-a ( average R-2 = 0.23 +/- 0.31) were observed in Taihu Lake water.