分光光度法对白洋淀各形态氮磷分布特征及源解析的研究

氮磷是引起湖泊富营养化的关键限制因子，对于水体和底泥中各形态氮磷的分布特征和源解析的研究能有效地揭示水体富营养化的过程与机制并分析其污染来源。白洋淀作为雄安新区最重要的水源之一，其水体富营养化状况严重，氮磷污染不容乐观。对于各形态氮磷含量分布特征及源解析的研究有助于全面分析该地区氮磷污染状况及污染来源，而目前同时研究底泥和水体两种介质各形态氮磷的分布规律，并利用模型定量分析各污染源对于各形态氮磷贡献的研究较少。利用分光光度法研究白洋淀水体和底泥两种介质各形态氮磷分布特征，利用主成分分析法综合评估白洋淀各区域氮磷综合污染状况，基于绝对主成分得分-多元线性回归(APCS-MLR)模型分析不同污染源对于各形态氮磷的贡献量。研究结果表明，白洋淀水体中总氮(TN)含量(1.41～4.64 mg·L-1)严重超标，均为重富营养化；水体中总磷(TP)含量(0.043～0.273 mg·L-1)污染也相对严重，95.8%的采样点为Ⅳ类及以上水质。水体中可被藻类和植物直接吸收利用的氨氮(NH+₄-N)和硝态氮(NO-₃-N)总占比达到54.9%；另外，对水体富营养化贡献大的溶解性无机磷(DIP)和溶解性有机磷(DOP)两种磷形态总占比达到52.8%。水体氮磷总量和形态的分布规律表明：白洋淀的水体富营养化状况不容乐观，对水体富营养化影响大的各形态氮磷占比大，其中白洋淀景区和淀边缘区污染相对严重。底泥生物可利用性氮(EN和HCl-N之和)占TN的比例为17.9%～66.4%，生物可利用性磷(BAP)的含量占TP的比例为8.50%～28.0%。以上结果表明，白洋淀底泥存在较大氮磷释放风险。主成分分析结果表明，白洋淀景区相较于其他区域氮磷污染严重。APCS-MLR模型分析结果表明生活源污染对于各形态氮磷(尤其底泥中)的贡献量大，农业污染、动植物残体分解、养殖业对各形态氮磷含量也有较大贡献。

Study on Distribution Characteristics of Different Nitrogen and Phosphorus Fractions by Spectrophotometry in Baiyangdian Lake and Source Analysis

Nitrogen and phosphorus are the key limiting factors of lake eutrophication. The study on the distribution characteristics and source analysis of nitrogen and phosphorus fractions in water and sediment can effectively reveal the process and mechanism of water eutrophication and analyze the pollution sources. As one of the most important water sources in the Xiongan New Area, the eutrophication of Baiyangdian Lake is serious, and the pollution of nitrogen and phosphorus is not optimistic. The study on the distribution characteristics and source analysis of nitrogen and phosphorus fractions is helpful to the analysis of nitrogen and phosphorus pollution in this area. However, there are few studies on the distribution of nitrogen and phosphorus fractions in sediment and water simultaneously, and the quantitative analysis of the contribution of nitrogen and phosphorus fractions by various pollution sources using models. In this study, the distribution characteristics of nitrogen and phosphorus in water and sediments of Baiyangdian Lake were studied by spectrophotometry. The contribution of different sources to nitrogen and phosphorus fractions was analyzed based on absolute principle components score combined with multivariate linear regression (APCS-MLR) model. The results showed that the content of total nitrogen (TN) (1.41～4.64 mg·L-1) in the water of Baiyangdian Lake exceeded the environmental quality standards and were all heavy eutrophication; the total phosphorus (TP) content (0.043～0.273 mg·L-1) in the water was also relatively seriously polluted, 95.8% of the sampling point were water quality of Class Ⅳ and above. The total proportion of ammonia nitrogen (NH+₄-N) and nitrate nitrogen (NO-₃-N) that could be directly absorbed and utilized by algae and plants reached 54.9%. In addition, the dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP), which contributed a great deal to the eutrophication of water accounted for 52.8%. The distribution regularity of nitrogen and phosphorus total amount and fractions showed that the eutrophication of Baiyangdian Lake was not optimistic, the pollution of Baiyangdian scenic area and margin area was relatively serious, and the proportion of nitrogen and phosphorus fractions which had great influence on water eutrophication was large. The ratio of bioavailable nitrogen (the sum of EN and HCl-N) to TN was 17.9%～66.4%, and the proportion of bioavailable phosphorus (BAP) in TP was 8.50%～28.0%. These results indicated a great risk of nitrogen and phosphorus release in the sediments of Baiyangdian Lake. The results of the principal component analysis showed that nitrogen and phosphorus pollution in Baiyangdian scenic area was more serious than that in other areas. The results of the APCS-MLR model showed that the contribution of domestic source pollution to nitrogen and phosphorus fractions were large, especially in sediments, agricultural pollution, animal and plant residues decomposition and aquaculture also contributed significantly to the content of different nitrogen and phosphorus fractions.