State Key Laboratory on Environmental Aquatic Chemistry, Research Center for Eco-Environmental Science, Chinese Academy of Science, P. O. Box 2871, Beijing 100085, PR China.
State Key Laboratory on Environmental Aquatic Chemistry, Research Center for Eco-Environmental Science, Chinese Academy of Science, P. O. Box 2871, Beijing 100085, PR China; University of Chinese Academy of Science, Beijing 100049, PR China.
Sci Total Environ. 2017 Apr 1;583:458-465. doi: 10.1016/j.scitotenv.2017.01.103. Epub 2017 Jan 22.
The processes and mechanisms through which phosphorus (P) is released from sediment and organic P is transformed, induced by the decomposition of plant (duckweed (Lemma minor L.)) debris, were studied experimentally. In the simulation experiments, the dissolved oxygen concentration, pH, and oxidation-reduction potential at the water-sediment interface first decreased rapidly. The lowest oxidation-reduction potential reached was 225.4mV, and the solution became weakly acidic (pH5.14) and anoxic (dissolved oxygen concentration 0.17mg·L). The dissolved oxygen concentration, pH, and oxidation-reduction potential then became stable. The soluble reactive P, total dissolved P, and total P concentrations in the overlying water all increased rapidly because of the particulate P and dissolved organic P released as the plant debris decomposed. P NMR analysis of the solution showed that orthophosphate monoesters were the main organic P compounds in the sediment. The orthophosphate monoester and orthophosphate diester concentrations were higher during the first 7d of the experiment (at 71.2 and 15.3mg·kg, respectively) than later (60.8 and 14.6mg·kg, respectively). The decomposition of the duckweed could have mineralized the orthophosphate monoesters and orthophosphate diesters to give orthophosphate. The results indicated that the decomposition of aquatic plant debris is a key factor in the release of P from sediment even when external P is excluded. It is therefore necessary to remove plant debris from freshwater ecosystems to control the release of P from plant debris and sediment.
本研究通过实验，探讨了植物（浮萍（Lemma minor L.））残体分解诱导的磷（P）从沉积物中释放和有机磷转化的过程和机制。在模拟实验中，水-沉积物界面的溶解氧浓度、pH 值和氧化还原电位首先迅速下降。最低氧化还原电位达到 225.4mV，溶液呈弱酸性（pH5.14）和缺氧状态（溶解氧浓度 0.17mg·L）。随后，溶解氧浓度、pH 值和氧化还原电位变得稳定。由于颗粒态 P 和溶解态有机磷的释放，上覆水中的可溶解性反应磷、总溶解磷和总磷浓度迅速增加。溶液的 P NMR 分析表明，正磷酸盐单酯是沉积物中主要的有机磷化合物。在实验的前 7 天（分别为 71.2 和 15.3mg·kg），正磷酸盐单酯和正磷酸盐二酯的浓度较高（分别为 71.2 和 15.3mg·kg），而后期（分别为 60.8 和 14.6mg·kg）的浓度较低。浮萍的分解可能将正磷酸盐单酯和正磷酸盐二酯矿化为正磷酸盐。研究结果表明，即使排除外部磷的情况下，水生植物残体的分解也是从沉积物中释放磷的关键因素。因此，有必要从淡水生态系统中清除植物残体，以控制植物残体和沉积物中磷的释放。
