[Estimation of releasing fluxes of sediment nitrogen and phosphorus in Fubao Bay in Dianchi Lake].

NH4(+)-N and PO4(3-)-P release from the sediment of Fubao Bay in Dianchi Lake were simulated using static incubations of intact sediment cores. The results showed that the releasing rates of sediment NH4(+)-N and PO4(3-)-P were 22.941-163.117 mg x (m2 x d)(-1) and 0.90-2.06 mg x (m2 x d)(-1), respectively, with large variation in different sampling areas. The lower releasing rates were associated with declined concentration gradients between sediment pore water and overlying water,which might be related to the high input of sewages in the bay. Using peeper (in situ dialysis membrane samplers) method, concentration gradients of NH4(+)-N and PO4(3-)-P were obtained at the interstitial water-overlying water profiles. Based on calculations using the Fick's First Law,the releasing rates of sediment NH4(+)-N and PO4(3-)-P were estimated at 2.85-81.96 mg x (m2 x d)(-1) and 0.118-0.265 mg x (m2 x d)(-1), respectively. Comparison of the two methods using to estimate the fluxes of sediment NH4(+)-N and PO4(3-)-P, the NH4(+)-N and PO4(3-)-P flux from the calculation using Fick's First Law was lower than that using static incubations. For the whole bay,the area-weighted releasing fluxes of NH4(+)-N and PO4(3-)-P from static incubations were estimated to be (49.9 +/- 8.8) t x a(-1) and (0.79 +/- 0.53) t x a(-1), respectively.