沉积物磷形态空间分布特征及释放风险评估——以沱江流域为例

为阐明沉积物磷赋存形态的空间分布特征及潜在释放风险,提供更准确合适的风险评估指标, 分析了沱江干流及其支流12个样点表层沉积物的磷赋存形态,测定了水溶性磷(WSP)及磷平衡浓度(EPC0),计算沉积物磷吸附指数(PSI)、磷吸附饱和度(DPS)及其衍生的磷释放风险指数(ERI).结果表明,沉积物5种形态磷含量顺序为:铁/铝结合磷(CDB-P,60.63%)>钙磷(Ca-P,30.84%)>有机磷(OP,3.92%)>亚铁磷(Fe(Ⅱ)-P,3.48%)>松散态磷(Loosely-P,1.13%).CDB-P是沉积物磷的主要存在形态(0.468~2.287mg/g),由上游至下游逐渐降低,这主要与上游工业污染有关.DPS、EPC0和PSI在空间分布上均呈现由上游至下游逐渐增大的趋势,变化范围分别为44.28%~80.39%、0.012~0.084mg/L和0.153~1.526L/g;上游大部分采样点ERI均超过了25%;各指标综合表明:上游存在较高的磷释放风险.回归分析与相关性表明,EPC0与上覆水磷、CDB-P、OP、有机质(OM)以及粒径均呈极显著相关性,且相关性远高于其他指标(ERI,DPS,PSI,WSP).因此,EPC0是评估沱江流域沉积物磷释放风险潜力更准确高效的指标,Fe/Al含量、粒径的增加以及有机质的减少会增加磷释放风险,因此应控制工业污染以及农业面源污染的输入.

Spatial distribution characteristics and release risk assessment of phosphorus forms in sediments: A case study of the Tuojiang River Basin

In order to clarify the spatial distribution characteristics of the phosphorus (P) in sediments and provide more accurate and suitable indicators for assessing P release risk, samples of surface sediments were taken from 12 sites in the main stream of the Tuojiang River and its tributaries for determining water-soluble phosphorus (WSP), equilibrium P concentration (EPC0), sediment P adsorption index (PSI) and adsorption saturation (DPS), and the derived P release risk index (ERI). The results show that the order of the P contents in the five forms of sediments is as follows: iron/aluminum combined P (CDB-P, 60.63%) > calcium P (Ca-P, 30.84%) > organic P (OP, 3.92%) > ferrous P (Fe(Ⅱ)-P), 3.48%) > loosely P (Loosely-P, 1.13%). CDB-P is the main form of sediment P (0.468~2.287mg/g) and decreases gradually from the upstream to the downstream, which is mainly related to upstream industrial pollution. The spatial distribution of DPS, EPC0and PSI tends to gradually increase with downstream, varying from 44.28% to 80.39%, 0.012 to 0.084mg/L and 0.153 to 1.526L/g, respectively. ERI exceeded 25% at the most upstream sampling sites, indicating a higher risk of P release in the upstream. Regression analysis and correlation show that EPC0 and the overlying water P, CDB-P, OP, OM, and particle size were significantly correlated. Therefore, EPC0can be thought to be a more accurate and efficient indicator for assessing the potential of P release from sediments in the Tuojiang River Basin. An increase in Fe/Al content, particle size, and the reduction of organic matter will elevate the P release risk, so the input of industrial pollution and agricultural non-point source pollution should be controlled.