岷江干流表层沉积物中磷形态空间分布特征

Distribution of Phosphorus Fractions in Surface Sediments of Minjiang Mainstreams

近些年,岷江水体TP污染情况严重,而水体沉积物这一潜在污染源,对水质安全带来的威胁也不容忽视.为揭示岷江干流表层沉积物中磷形态的空间分布特征,于2016年12月,采集了岷江干流(阿坝~宜宾)表层沉积物样品,应用改进的SEDEX法对表层沉积物中的弱吸附态磷Ex-P、可提取态有机磷Org-P、铁结合态磷Fe-P、自生磷灰石磷Ca-P、碎屑磷De-P和非活性磷Res-P等6种磷形态质量浓度进行了测定.结果表明,岷江干流表层沉积物中总磷TP的质量浓度为522.17~979.22μg·g^(-1),已远超全国土壤磷素背景值700μg·g^(-1),表明岷江沉积物中TP浓度较高.从空间分布来看,岷江中游眉山河段中的表层沉积物是颗粒最细、有机质和TP质量浓度最高的区域.岷江干流表层沉积物磷的主要赋存形态为Ca-P和DeP,两者共占TP的质量分数为75%以上.同时,岷江干流表层沉积物中的生物可利用磷(Ex-P、Org-P和Fe-P总和)占TP的质量分数为10.31%~29.62%,其中以中游河段(尤其是眉山段、乐山段)质量浓度最高,这表明岷江中游河段表层沉积物中磷的生物可利用性较强,潜在环境风险较高.

In recent years,the total phosphorus pollution in Minjiang River was serious,and the surface sediments of the Minjiang River also threatened water quality. To study the spatial distributions of phosphorus in the surface sediments of the Minjiang River,samples of surface sediments were collected upstream（ Aba District） and downstream（ Yibin District） of the Minjiang River in December,2016. The sediments were analyzed with the modified sequential extraction method（ SEDEX） to obtain six forms of phosphorus,including exchangeable phosphorus（ Ex-P）,exchangeable organic phosphorus（ Org-P）,iron-bound phosphorus（ Fe-P）,authigenic phosphorus（ Ca-P）,detrital phosphorus（ De-P）,and refractory phosphorus（ Res-P）. The results indicated that the contents of total phosphorus（ TP） in surface sediments ranged from 522. 17 μg·g-1 to 979. 22 μg·g^（-1）,which were far more than the soil phosphorus background values（ 700 μg·g^（-1））. The spatial distribution characteristics of the TP of surface sediments indicated that the TP concentrations in sediments at the Meishan sections（ the middle reach of the Minjiang River） were higher than those in the other sections. This was related to the smaller particle size and higher OM contents in sediments in the Meishan sections. The main phosphorus forms in the sediments in the Minjiang River were Ca-P and De-P,with their concentrations accounting for 75% of TP in the sediments. The bio-available phosphorus,which included Ex-P,Org-P,and Fe-P,accounted for 0. 31%-29. 62% of TP in the sediments of the Minjiang River. The concentrations of bio-available phosphorus in sediments at the Meishan sections and Leshan sections（ the middle reach） were highest,indicating that bio-available phosphorus in the surface sediments was high,and its potential environmental impact risks were higher.