The spatial distribution of phosphorus and their correlations in surface sediments and pore water in Lake Chaohu, China

Abstract

The study presents the spatial distribution of different forms of phosphorus in the sediments in Lake Chaohu, a large eutrophic Chinese lake, and their correlation with phosphorus content in pore water. The sediment and pore water samples were taken from 19 sampling sites. A sequential extraction was used to determine the contents of different forms of phosphorus in the sediments. The compositions and spatial distribution of different forms of phosphorus in the sediments and their correlation with orthophosphate and total phosphorus content in the pore water were studied. The following results were obtained: (1) the mean content of total phosphorus was 474.7 ± 20.5 mg/kg, with 390.8 ± 82.4 mg/kg for the eastern lake (N = 5), 469.0 ± 53.9 mg/kg for the western lake (N = 5), and 524.5 ± 185.3 mg/kg for rivers (N = 9); (2) the order of the proportions of the different forms of phosphorus was occluded phosphorus (Oc-P, 52.4%) > debris phosphorus (De-P, 14.2%) > auto-calcium-bound phosphorus (ACa-P, 13.5%) > aluminum-bound phosphorus (Al-P, 9.8%) > organic phosphorus (Or-P, 6.8%) > exchangeable phosphorus (Ex-P, 2.1%) > iron-bound phosphorus (Fe-P, 1.3%); (3) Ex-P, Al-P, and Fe-P had significantly positive correlations with orthophosphate and total phosphorus content in pore water, which showed that these forms of phosphorus were released more easily and had an indirect impact on lake eutrophication.