Location: Commodity Utilization ResearchTitle: Characterization of organic phosphorus in lake sediments by sequential fractionation and enzymatic hydrolysis Author
Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2013
Publication Date: 7/15/2013
Citation: Zhu, Y., Wu, F., He, Z., Guo, J., Qu, X., Xie, F., Giesy, J.P., Liao, H., Guo, F. 2013. Characterization of organic phosphorus in lake sediments by sequential fractionation and enzymatic hydrolysis. Journal of Environmental Science and Technology. 47:7679-7687. Interpretive Summary: Phosphorus (P) is the limited nutrient in most natural ecosystems. As external P inputs were gradually reduced last decades, release of internal P accumulated in lake sediments becomes an important source of P in lake ecosystems. Therefore, interests in P transformation, bioavailability and exchange between sediment and the overlying water have been increased in recent years. In this study, 18 surface sediments samples were collected from Dianchi Lake, an eutrophic lake in Southwest China. Sequential extraction coupled with phosphatase hydrolysis was used to identify the bioavailability of different P pools in these eutrophic lake sediments. Data in this work show that a large share of the allochthonous P input was inorganic or apatite-bound form. Organic matter and organic P in the sediments were mainly from autochonous sources. In other words, eutrophication of lakes would accumulate the organic matter and also bioavailable Po in the sediments. This study warrants further investigation of the biogeochemical process of organic P by enzymatic hydrolysis in the lake sediments, especially the relationship between this process and eutrophication, and also the origin and fate of inositol phosphates.
Technical Abstract: Knowledge of the phosphorus (P) fractions and their bioavailability in sediments is fundamental for understanding the biogeochemical process of P cycle and its role on eutrophication in the lake ecosystems. In this study, 18 surface sediments samples were collected from Dianchi Lake, an eutrophic lake in Southwest China. Sequential extraction coupled with phosphatase hydrolysis was used to identify the bioavailability of different P pools in these samples. The relative abundance of inorganic P (Pi) was in the order of HCl-Pi > NaOH-Pi > NaHCO3-Pi > H2O-Pi and the abundance of organic P (Po) pool was in the order of NaOH-Po > NaHCO3-Po > HCl-Po > H2O-Po. Hydrolysis of Po in these fractions was characterized by enzymatic incubation with alkaline phosphatase, phytase, phosphodiesterase combined with alkaline phosphatase or their all combinations. The percentage of hydrolyzable Po was in the order of H2O > NaHCO3 > NaOH. Specifically, alkaline phosphatase released 0%~33.4% in the bicarbonate soluble Po, whereas a combination of phosphodiesterase and alkaline phosphatase hydrolyzed a little greater portions (i.e., 18.3%~63.7% in the bicarbonate soluble Po). The phytase preparation also hydrolyzed from none to 100% of bicarbonate soluble Po. The combination of all these 3 enzymes hydrolyzed much greater portion of Po (i.e., 63.2%~130.5% in the bicarbonate soluble organic P). The sum of Po extracted and hydrolyzed was positively related to the content of total organic carbon in the sediments, which implied that eutrophication of lakes would accumulate the organic matter and also bioavailable Po in the sediments.