Characterization of plant-derived carbon and phosphorus in lakes by sequential fractionation and NMR spectroscopy

Authors: LIU,, SHASHA - Chinese Research Academy Of Environmental Sciences; ZHU, YUANRONG - Chinese Research Academy Of Environmental Sciences; WU, FENGCHANG - Chinese Research Academy Of Environmental Sciences; MENG, WEI - Chinese Research Academy Of Environmental Sciences; He, Zhongqi; GEISY, JOHN - Chinese Research Academy Of Environmental Sciences

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2016
Publication Date: 6/6/2016
Citation: Liu, S., Zhu, Y., Wu, F., Meng, W., He, Z., Geisy, J.P. 2016. Characterization of plant-derived carbon and phosphorus in lakes by sequential fractionation and NMR spectroscopy. Science of the Total Environment. 566-567:1398-1409.

Interpretive Summary: Debris from aquatic macrophytes is one of the most important endogenous sources of organic matter (OM) and nutrients in lakes. Death and decomposition of aquatic macrophytes play an important role on biogeochemical cycling of nutrients including carbon (C), and phosphorus (P) in lakes. In this study, a three-step fractionation procedure was applied to separate C (organic matter) and P of aquatic plants into four pools, and characterized by chemical analysis and 31P and 13C NMR spectroscopy. Per the observations in this work, we proposed that those forms of C and P in the H2O, NaOH and HCl fractions are labile and bioavailable components, and the residues would be accumulated and preserved in sediments. The results would be helpful in understanding contributions from aquatic macrophytes and biogeochemical cycling in eutrophic lakes.

Technical Abstract: Although debris from aquatic macrophytes is one of the most important endogenous sources of organic matter (OM) and nutrients in lakes, its biogeochemical cycling and contribution to internal load of nutrients in eutrophic lakes are still poorly understood. In this study, sequential fractionation by H2O, 0.1 M NaOH and 1.0 M HCl, combined with 13C and 31P NMR spectroscopy, was developed to characterize C and P in six aquatic plants collected from Tai Lake (Ch: Taihu), China. Per total organic carbon (TOC), organic matter unequally distributed in H2O (21.2%), NaOH (29.9%), HCl (3.5%) and residual (45.3%) fractions. For P in aquatic plants, 53.3% can be extracted by H2O, 31.9% by NaOH, and 11% by HCl, with 3.8% in the residual fractions. Predominant OM components extracted by water and NaOH were carbohydrates and aliphatic acids, whereas inorganic P (Pi) was the primary P species in water fractions, organic P (Po) was primary P species in NaOH fractions. The subsequent HCl extracted fewer C and P species. Per these observations, we proposed that those forms of C and P in the H2O, NaOH and HCl fractions are labile and bioavailable components. Thus, 54.7% of OM and 96.2% of P in debris of aquatic plants were evaluated as potential bioavailable. The residues would be accumulated and preserved in sediments. The results would be helpful in understanding contributions from aquatic macrophytes and biogeochemical cycling in eutrophic lakes.