白洋淀典型区域清淤前后沉积物的氮磷扩散通量研究

清淤是治理湖泊内源污染、控制水体富营养化的一项重要措施.本文对白洋淀示范工程区清淤前后沉积物的上覆水与间隙水中氮磷的含量与扩散通量进行了研究，评估清淤示范工程对白洋淀内源氮磷污染负荷的控制效果.结果表明：清淤前，南刘庄和采蒲台示范区沉积物的表层间隙水中氨氮（NH₄⁺-N）浓度分别为0.31~8.93、0.25~5.64 mg·L^-1，磷酸盐（PO₄^3-）浓度分别为0.03~1.61、0.01~0.07 mg·L^-1，由于表层间隙水中NH₄⁺-N、PO₄^3-浓度较高，导致沉积物-水界面氮磷的扩散通量较高.南刘庄和采蒲台示范区沉积物-水界面NH₄⁺-N平均扩散通量分别为3.17、2.72 mg·m^-2·d^-1，PO₄^3-平均扩散通量分别为0.071、0.018 mg·m^-2·d^-1，表明NH₄⁺-N与PO₄^3-的潜在内源释放风险很高.清淤后，示范区表层间隙水中NH₄⁺-N与PO₄^3-浓度有明显的下降趋势，南刘庄和采蒲台示范区沉积物表层间隙水中NH₄⁺-N浓度分别为0.19~5.50、0.43~4.33 mg·L^-1，PO₄^3-浓度分别为0~0.07、0~0.03 mg·L^-1.南刘庄和采蒲台示范区沉积物-水界面NH₄⁺-N平均扩散通量分别为0.752、0.747 mg·m^-2·d^-1，PO₄^3-平均扩散通量分别为0.011、0.003 mg·m^-2·d^-1，可见清淤后NH₄⁺-N与PO₄^3-的潜在释放风险显著降低.由此充分说明，清淤工程有效地控制了白洋淀沉积物的内源氮磷污染负荷.

Nitrogen and phosphorus diffusive fluxes across the sediment-water interface before and after dredging typical areas of Baiyangdian Lake

Dredging is an important measure for lake endogenous pollution treatment and water eutrophication control. In this study, the content and diffusive fluxes of nitrogen and phosphorus in the overlying water and pore water from two demonstration areas in Baiyangdian Lake before and after dredging were investigated, and the effect of the dredging demonstration project on the control of endogenous nitrogen and phosphorus pollution loadings in lake sediments was evaluated. Before dredging, the NH₄⁺-N concentrations in surface pore water from Nanliuzhuang and Caiputai demonstration areas varied from 0.31 to 8.93 mg·L^-1 and from 0.25 to 5.64 mg·L^-1 respectively, and the PO₄^3- concentrations in surface pore water from the two demonstration areas varied from 0.03 to 1.61 mg·L^-1 and from 0.01 to 0.07 mg·L^-1 respectively. The high concentrations of NH₄⁺-N and PO₄^3- in the surface pore water resulted in high diffusive fluxes of nitrogen and phosphorus across the sediment-water interface. The average diffusive fluxes of NH₄⁺-N from the two demonstration areas were 3.17 mg·m^-2·d^-1 and 2.72 mg·m^-2·d^-1 respectively, and the average diffusive fluxes of PO₄^3- were 0.071 mg·m^-2·d^-1 and 0.018 mg·m^-2·d^-1 respectively, which suggested a high risk of endogenous-nutrients releasing. After dredging, the concentrations of NH₄⁺-N and PO₄^3- in the surface pore water from both demonstration areas decreased significantly. The NH₄⁺-N concentrations in surface pore water varied from 0.19 to 5.50 mg·L^-1 and from 0.43 to 4.33 mg·L^-1 respectively, and the PO₄^3- concentrations in surface pore water were lower than 0.07 mg·L^-1 and 0.03 mg·L^-1 respectively. Moreover, the average diffusive fluxes of NH₄⁺-N decreased to 0.752 mg·m^-2·d^-1 and 0.747 mg·m^-2·d^-1 respectively, and the average diffusive fluxes of PO₄^3- decreased to 0.011 mg·m^-2·d^-1 and 0.003 mg·m^-2·d^-1 respectively, which suggested a significantly reduced risk of NH₄⁺-N and PO₄^3- releasing in demonstration areas after dredging. The study demonstrates that dredging can effectively control the endogenous nitrogen and phosphorus pollution loadings in Baiyangdian Lake sediments.