采用连续分级提取法研究沉积物中磷的化学形态

沉积物中磷的潜在释放很大程度上取决于有机磷和无机磷的组分和分布. 为研究沉积物中不同形态磷的释放能力及其生物可利用性大小,采用连续分级提取法,以NH₄Cl、NaHCO₃、NaOH和HCl作为提取剂,同时对沉积物中有机磷和无机磷的赋存形态进行分析,将无机磷分为WA-P_i(弱吸附态无机磷)、PA-P_i(潜在活性无机磷)、Fe/Al-P_i(Fe/Al结合态无机磷)和Ca-P_i(Ca结合态无机磷)；将有机磷分为WA-P_o(弱吸附态有机磷)、PA-P_o(潜在活性有机磷)、MA-P_o(中活性有机磷)和NA-P_o(非活性有机磷),并以蠡湖表层沉积物样品为例,考察了该方法的回收率及蠡湖沉积物中的磷形态. 结果表明:①该方法具有较好的回收率,与SMT(标准测量和测试)法测定结果比较,连续分级提取法对TP、无机磷、有机磷的回收率分别为93.3%~112.1%、93.9%~111.5%、76.4%~119.9%,平均值分别为99.4%、101.8%、101.0%. ②蠡湖表层沉积物中的磷以无机磷为主,其质量分数在271.29~666.34 mg/kg之间,平均值为441.03 mg/kg,占w(TP)的62.91%；不同形态无机磷质量分数表现为w(Ca-P_i)>w(Fe/Al-P_i)>w(PA-P_i)>w(WA-P_i). 有机磷的质量分数在201.76~368.52 mg/kg之间,不同形态有机磷质量分数表现为w(R-P_o)(R-P_o为残渣态磷)>w(NA_NaOH-P_o)(NA_NaOH-P_o为NaDH提取非活性有机磷)>w(PA-P_o)>w(MA_HCl-P_o)(MA_HCl-P_o为HCl提取中活性有机磷)>w(WA-P_o)>w(MA_NaOH-P_o)(MA_NaOH-P_o为NaOH提取中活性有机磷). 改进后的连续分级提取法能够同时有效分离沉积物中无机磷和有机磷的化学形态,并且能兼顾沉积物生物可利用性磷分析测试的需要. 

Analysis of Phosphorus Fractions in Sediments by Sequential Extraction

The potential release of phosphorus in sediments depends largely on the composition and distribution of organic phosphorus and inorganic phosphorus. To study the release ability and bioavailability of different phosphorous fractions in sediments, the occurrence forms of organic phosphorus and inorganic phosphorus were analyzed simultaneously by sequential extraction using NH₄Cl, NaHCO₃, NaOH and HCl as extractants. Inorganic phosphorus in sediments was divided into four groups:weakly adsorbed inorganic phosphorus (WA-P_i), potential active inorganic phosphorus (PA-P_i), Fe/Al-bound inorganic phosphorus (Fe/Al-P_i) and Ca-bound inorganic phosphorus (Ca-P_i). Organic phosphorus was also divided into four groups:weakly adsorbed organic phosphorus (WA-P_o), potential active organic phosphorus (PA-P_o), middle-active organic phosphorus (MA-P_o) and non-active organic phosphorus (NA-P_i). The method recovery rate and phosphorus forms in sediment were studied in Lihu Lake. The results showed that:1) Compared with the SMT method, the recovery rate of the method was satisfactory. The recovery percentages of TP, inorganic phosphorus and organic phosphorus were 93.3%-112.1%, 93.9%-111.5% and 76.4%-119.9%, with mean values of 99.4%, 101.8% and 101.0%, respectively. 2) Inorganic phosphorus was the main phosphorus fraction in surface sediments of Lihu Lake. The content of inorganic phosphorus was 271.29-666.34 mg/kg, with mean value of 441.03 mg/kg, accounting for 62.91% of w(TP). The content of different inorganic phosphorus forms was in the order of w(Ca-P_i)>w(Fe/Al-P_i)>w(PA-P_i)>w(WA-P_i). The content of organic phosphorus was 201.76-368.52 mg/kg. The content of different organic phosphorus forms was in the order of w(R-P_o)>w(NA_NaOH-P_o)>w(PA-P_o)>w(MA_HCl-P_o)>w(WA-P_o)>w(MA_NaOH-P_o). The chemical forms of inorganic phosphorus and organic phosphorus could be effectively separated by the improved sequential extraction method simultaneously. The analytical needs for testing of bioavailable phosphorus should also be taken into consideration.