Sequential fractionation of reactive phosphorus in the sediment of a shallow eutrophic lake——Donghu Lake, China

ＩｎｔｒｏｄｕｃｔｉｏｎＳｅｄｉｍｅｎｔｐｈｏｓｐｈｏｒｕｓｈａｓｂｅｅｎｔｈｅｆｏｃｕｓｏｆａｎｕｍｂｅｒｏｆｓｔｕｄｉｅｓｄｕｅｔｏｉｔｓｒｏｌｅｉｎｔｈｅｅｕｔｒｏｐｈｉｃａｔｉｏｎｏｆｌａｋｅｓ.Ｐｈｏｓｐｈｏｒｕｓｆｒａｃｔｉｏｎｓｉｎｓｅ?..

The bioavailability of phosphorus in lake sediment mainly depends on its forms. Therefore, reactive phosphorus (RP) pool of the sediment in a shallow eutrophic lake(Donghu Lake) was determined seasonally and spatially by sequential chemical extraction according to the scheme proposed by Psenner et al. (Psenner, 1985) and its modified version respectively. The ammonium chloride extracted 3%—7% of the total reactive phosphorus (Tot\|RP), while the distilled water extracted less(<3%). These two forms of P were significantly higher at the most eutrophic stations(I and IV). The sum of BD\|RP(reductant soluble P) and NaOH\|RP extracted accounted for 57%—81% of Tot\|RP, which could play significant roles in P cycling. The percentages of HCl\|extractable RP in the sediments of station III, however, were usually much more than those of other stations, which could reflect the original geochemistrical characteristics and trophic status of the sediments. It was noted that the sediment RP in different fractions varied in different months studied.