九龙江河流-库区系统沉积物磷特征及其生态学意义

采用沉积物磷形态的标准测试方法 (SMT)分析了九龙江北溪河流-库区系统16个站位的沉积物磷含量和形态组成,探讨了该系统沉积物磷的空间分布、形态特征及其生态学意义.结果表明,沉积物总磷(TP)的含量为387～2 092 mg.kg-1,平均1 032 mg.kg-1.以无机磷(IP)为主要赋存形态,IP占TP的48%～98%,而IP中以铁铝结合态磷(Fe/Al-P)为主,占IP的43%～99%.TP和Fe/Al-P含量呈现上游高、下游低的空间分布规律,与表层水DTP含量和陆源污染负荷的分布一致.北溪沉积物TP含量的高低主要受Fe/Al-P控制.沉积物富磷、高Fe/Al-P比例(释放潜力大)以及"上游高下游低"的空间分布特征,加上九龙江上游水体较低的氮磷比值属于藻类生长磷弱限制,极可能是九龙江水华首先在上游暴发并向下游库区蔓延的主要原因.九龙江沉积物磷的这些特征在水华过程中具有重要的调控作用和生态学意义.

Characteristics of Sediment Phosphorus in the Jiulong River-Reservoir System and Its Ecological Significance

Sediment phosphorus (P) content and component ratio from 16 sites along the North Jiulong River-reservoir system were analyzed using the Standard Measurement and Test (SMT) procedure. The spatial pattern and characteristics of sediment P and its ecological significance in the Jiulong River-reservoir system were examined in combination with water measurement and watershed information. Total P content in sediments ranged from 387 to 2092 mg ·kg^-1 with an average of 1032 mg ·kg^-1. Inorganic phosphorus (IP) dominated P in sediment, accounting for 48%-98% of TP, and Fe/Al-bound phosphorus (Fe/Al-P) took 43%-99% of IP. The spatial pattern of sediment showed that TP and Fe/Al-P were higher in upstream and lower in downstream, corresponding to the spatial variation of surface water P and land-based loads from animal waste, human waste and fertilizer loss. Spatial variation of TP in sediment was controlled by Fe/Al-P along the North Jiulong River. The P-rich sediment with a great release potential due to the high ratio of Fe/Al-P, the typical spatial pattern, and the lower N/P ratio observed in upstream water (where phytoplankton growth tends to be weakly limited by phosphorus), are likely to explain the fact that algal blooms first appear in the upstream and then spread to downstream reservoirs along the North Jiulong River. Present findings concerning sediment P characteristics indicate an important regulating effect and the ecological significance on the process of algal blooms in the Jiulong River.