蓝藻暴发对巢湖表层沉积物氮磷及形态分布的影响

以巢湖表层沉积物及上覆水体为对象,于蓝藻暴发前(4月)和蓝藻暴发期(7月)采集水样及沉积物样品,分析了氮磷及其形态赋存特征,并探讨了沉积物氮磷及其形态与蓝藻暴发的关系.结果发现,蓝藻暴发时,巢湖表层沉积物总磷减少,总氮增加,同时削弱了磷在空间上分布的异质性.从氮磷形态来看,蓝藻暴发未造成巢湖表层沉积物氮形态(NH4+-N、NO3--N和Org-N)含量和比例的明显波动,但却造成了活性磷(弱吸附态磷和铁铝结合态磷之和)含量及比例的下降,钙结合态磷(Ca-P)以及有机磷(OP)含量及比例增加,生物有效性磷(AAP)的含量的减小.相关性分析表明,上覆水中叶绿素a(Chl-a)的浓度与铁铝结合态磷(Fe/Al-P)以及有机磷(OP)的含量显著相关(P<0.05),却与氮形态(铵态氮,硝态氮和有机氮)相关性不显著.巢湖沉积物磷(Fe/Al-P及AAP)对巢湖水体蓝藻暴发具有促进作用,而氮及其形态对蓝藻暴发作用较弱.

Influence of algae bloom on distribution of total and speciation of nitrogen and phosphorus in the surface sediments from Lake Chaohu

Surface sediment and overlying water from Lake Chaohu were sampled before (in April) and after (in July) algal bloom. Total and speciation of nitrogen and phosphorus in the sediments were analyzed, and their relationship with algal bloom was discussed. Algal bloom could increase the concentrations of nitrogen and decrease the concentrations of phosphorus from surface sediments, and therefore weaken the heterogenicity of sediment phosphorus concentrations. The algal bloom did not cause the obvious fluctuation of concentrations and proportion of nitrogen speciation (NH4+-N, NO3--N, Org-N), but decrease the concentrations and proportion of reactive phosphorus (LP and Fe/Al-P) rather than the proportion and content of Ca-bound P (Ca-P) in surface sediments. Meanwhile, algal boom decrease the concentrations of surface sediment bioavailable phosphorus (AAP) in whole lake. Correlation analysis indicated that the concentration of Chlorophyll-a correlated significantly with Fe/Al-bound P (Fe/Al-P) and organic phosphorus (OP) (P<0.05) but with the nitrogen forms (NH4+-N, NO3--N, Org-N) in surface sediments. These results indicated that phosphorus mainly Fe/Al-P and AAP in surface sediment played an important role in promoting algae bloom in Lake Chaohu and indicated that nitrogen and its fractions in surface sediment contributed less to the algal bloom in Lake Chaohu.