State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China.
State Key Laboratory of Environment Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
Environ Sci Pollut Res Int. 2017 Oct;24(30):23518-23527. doi: 10.1007/s11356-017-9996-z. Epub 2017 Aug 28.
As a primary factor responsible for lake eutrophication, a deeper understanding of the phosphorus (P) composition and its turnover in sediment is urgently needed. In this study, P species in surface sediments from a Chinese large eutrophic lake (Lake Taihu) were characterized by traditional fractionation and P nuclear magnetic resonance (NMR) spectroscopy, and their contributions to the overlying water were also discussed. Fractionation results show that NaOH-P predominated in the algal-dominated zone, accounting for 60.1% to total P in Zhushan Bay. Whereas, refractory fractions including HCl-P and residual-P were the main P burial phases in the macrophyte-dominated zone, the center and lakeshore. Recovery rates of the total P and organic P were greatly improved by using a modified single-step extraction of NaOH-EDTA, ranging from 22.6 to 66.1% and from 15.0 to 54.0%. Ortho-P, monoester-P, and pyro-P are identified as the major P components in the NaOH-EDTA extracts by P NMR analysis. Trace amount of DNA-P appeared only in sediments from algal- and macrophyte-dominated zones, ascribing to its biological origin. The relative content of ortho-P is the highest in the algal-dominated zone, while the biogenic P including ester-P and pyro-P is the highest in the macrophyte-dominated zone. Moreover, ortho-P and pyro-P correlated positively with TP and chlorophyll a in the overlying water, whereas only significant relationships were found between monoester-P, biogenic P, and chlorophyll a. These discrepancies imply that inorganic P, mainly ortho-P, plays a vital role in sustaining the trophic level of water body and algal bloom, while biogenic P makes a minor contribution to phytoplankton growth. This conclusion was supported by the results of high proportion of biogenic P in algae, aquatic macrophytes, and suspended particulate from the published literature. This study has significant implication for better understanding of the biogeochemical cycling of endogenous P and its role in affecting lake eutrophication.
作为湖泊富营养化的主要因素之一，迫切需要更深入地了解沉积物中的磷（P）组成及其转化。本研究采用传统的分级法和磷核磁共振（NMR）光谱法对中国大型富营养化湖泊（太湖）表层沉积物中的磷形态进行了研究，并讨论了它们对表层水的贡献。分级结果表明，在以藻类为主的区域，NaOH-P 占总磷的 60.1%，而在以大型水生植物为主的区域，HCl-P 和残留-P 等难溶态磷则是磷的主要埋藏相，主要分布在湖心和湖岸。采用改良的 NaOH-EDTA 一步提取法，总磷和有机磷的回收率大大提高，范围分别为 22.6%66.1%和 15.0%54.0%。通过磷 NMR 分析，NaOH-EDTA 提取物中的主要磷组分为正磷酸盐（ortho-P）、单酯磷（monoester-P）和焦磷酸盐（pyro-P）。痕量的 DNA-P 仅出现在藻类和大型水生植物为主的区域的沉积物中，这归因于其生物来源。在藻类为主的区域，正磷酸盐的相对含量最高，而在以大型水生植物为主的区域，生物源磷（包括酯磷和焦磷酸盐）的含量最高。此外，正磷酸盐和焦磷酸盐与表层水中的总磷（TP）和叶绿素 a 呈正相关，而只有单酯磷、生物源磷和叶绿素 a 之间存在显著关系。这些差异表明，无机磷（主要是正磷酸盐）在维持水体富营养化和藻类水华方面起着至关重要的作用，而生物源磷对浮游植物的生长贡献较小。这一结论得到了文献中报道的藻类、水生植物和悬浮颗粒物中生物源磷比例较高的结果的支持。本研究对更好地了解内源磷的生物地球化学循环及其对湖泊富营养化的影响具有重要意义。
