Origins and Mobility of Phosphorus Forms in the Sediments of Lakes Taihu and Chaohu, China

Abstract

Phosphorus release from the sediment is generally an important factor for lake eutrophication. We have investigated phosphorus forms in surface sediments from Lake Taihu and Lake Chaohu by a chemical extraction method. The results showed that the concentrations of Fe/Al-bound phosphorus (Fe/Al-P) and organic phosphorus (Org-P) had significant correlations with those of amorphous Fe/Al oxides and organic matter in the sediments. Furthermore, Ca-bound phosphorus (Ca-P) concentrations were well related to total organic carbon (TOC) concentrations. The results also indicated that higher pH weakened the association of phosphates with the Fe/Al hydroxides and then resulted in Fe/Al-P release. The increase of pH was companied with autogenetic progresses of calcium carbonate and then elevated Ca-P concentrations in the sediments. In conclusion, external P loadings determine spatial distribution of P fractions, especially Fe/Al-P and Org-P, and partially contribute to additional Ca-P fractions in these highly human-disturbed lakes. The pH-induced phosphorus mobility in the sediments is very important for these lakes.

Keywords:

• Phosphate
• Phosphorus speciation
• Phosphorus release
• Eutrophic lakes
• Yangtze River

ACKNOWLEDGMENTS

This work is funded by a key project of the Chinese Academy of Sciences (Grant No. KZCX1-SW-12-II-32) and the National Key Project for Basic Research (Grant No. 2002CB412304).

Notes

^a A sediment reference material (GBW07301a, 1520 ± 70 mg P/g) certified by China Standard Bureau.

^a Correlation is significant at the 0.05 level (two-tailed).

^b Correlation is significant at the 0.01 level (two-tailed).