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.
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).