Simultaneous Monitoring of Phosphine and of Phosphorus Species in Taihu Lake Sediments and Phosphine Emission from Lake Sediments

摘要

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.