南漪湖沉积物磷的赋存形态及对上覆水的影响

以宣城市南漪湖为例,采用改进的无机磷分级提取方法对全湖共39个点位沉积物中磷(P)赋存形态进行系统研究,并分析其与上覆水体、间隙水等相互关系。结果表明,南漪湖水体磷污染水平已经处于高位,沉积物间隙水磷与上覆水体磷空间分布特征具有密切关系。南漪湖沉积物中总磷(TP)含量变化范围为463.3~1016.6mg/kg,其中各形态磷空间分布具有明显的差异性,与外源磷输入等密切相关。赋存形态含量大小、相对比例顺序依次为:钙结合态磷(Ca-P)>铁结合态磷(Fe-P)>铝结合态磷(Al-P)>还原剂可溶性磷(RS-P)>残渣态磷(Res-P)>弱吸附态磷(L-P)。沉积物中TP含量与Fe-P、RS-P、Res-P极显著正相关,与L-P含量显著正相关。外源磷输入和水产养殖对南漪湖沉积物内源磷中Fe-P和RS-P贡献可能较大。南漪湖沉积物内源磷对上覆水体的潜在风险较高,其中生物有效性较高的L-P、Al-P、Fe-P和Rs-P的总和相对比例可达60%左右。沉积物中磷形态与间隙水磷浓度关系较密切,其中Al-P、Ca-P对间隙水中磷迁移转化具有重要影响。南漪湖主要出入湖河口沉积物磷的吸附解吸平衡浓度(EPC₀)变化范围为0.009~0.014mg/L,均表现为EPC₀<总溶解性活性磷浓度(SRP),主要河口沉积物目前仍为外源磷输入的汇。

Characteristics of phosphorus fractions in sediments and its influence on the water quality of Lake Nanyi

Fractions of phosphorus (P) in sediments were investigated by using an improved sequential extraction procedure for inorganic P in 39 sampling sites from Lake Nanyi, Xuancheng city, Province of Anhui, China. The relationships between P fractions in sediments, concentrations of P in the overlying water and pore water were analyzed. Results show that the concentrations of total P (TP) in the overlying water of Lake Nanyi were in a high level, which were closely related with concentrations of TP in the pore water. Contents of TP in the sediments of Lake Nanyi ranged from 463.3 to 1016.6 mg/kg. Spatial distribution of P fractions in sediments was significant difference, which was closely related with the inputs of external P. Contents and their relative percentages were decreased in the order that calcium-bound P (Ca-P)>iron-bound P (Fe-P)>aluminium-bound P (Al-P)>reduced soluble P (RS-P)>residual P (Res-P)>loosely absorbed and dissolved P (L-P). Contents of TP in the sediments were significantly correlated with Fe-P, RS-P, Res-P and L-P. Input of external P and aquiculture was likely contributed large of internal Fe-P and RS-P in sediments from Lake Nanyi. The potential risk of internal load of P in sediments was high, which bioavailable P fractions including L-P, Al-P, Fe-P, and Rs-P accounted for 60% approximately. Concentrations of P in pore water were closely related with the spatial distribution characteristics of P fractions in sediments. The main compositions of P including Al-P and Ca-P have important influence on migration and transformation of P in the pore water. The zero equilibrium P concentration (EPC₀) value of the sediments from the area of main river estuary ranged from 0.009 to 0.014 mg/L, which showed that the EPC₀