Key Lab of Freshwater Animal Breeding, Ministry of Agriculture and Rural Areas, College of Fisheries, Huazhong Agricultural University, 430070, Wuhan, China; Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, 430070, Wuhan, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, 210008, Nanjing, China.
Wuhan Changjiang Waterway Rescue and Salvage Bure, 430013, Wuhan, China.
J Environ Manage. 2024 Feb 14;352:120053. doi: 10.1016/j.jenvman.2024.120053. Epub 2024 Jan 10.
The combination of chemical phosphorus (P) inactivation and submerged macrophyte transplantation has been widely used in lake restoration as it yields stronger effects than when applying either method alone. However, the dose effect of chemical materials on P inactivation when used in combination with submerged macrophytes and the influences of the chemicals used on the submerged macrophytes growth remain largely unknown. In this study, we investigated P inactivation in both the water column and the sediment, and the responses of submerged macrophytes to Lanthanum modified bentonite (LMB) in an outdoor mesocosm experiment where Vallisneria denseserrulata were transplanted into all mesocosms and LMB was added at four dosage levels, respectively: control (LMB-free), low dosage (570 g m), middle dosage (1140 g m), and high dosage (2280 g m). The results showed that the combination of LMB dosage and V. denseserrulata reduced TP in the water column by 32%-38% compared to V. denseserrulata alone, while no significant difference was observed among the three LMB treatments. Porewater soluble reactive P, two-dimensional diffusive gradient in thin films (DGT)-labile P concentrations, and P transformation in the 0-1 cm sediment layer exhibited similar trends along the LMB dosage gradient. Besides, LMB inhibited plant growth and reduced the uptake of mineral elements (i.e., calcium, manganese, iron, and magnesium) in a dosage-dependent manner with LMB. LMB may reduce plant growth by creating a P deficiency risk for new ramets and by interfering with the uptake of mineral elements. Considering both the dose effect of LMB on P inactivation and negative effect on macrophyte growth, we suggest a "small dosage, frequent application" method for LMB application to be used in lake restoration aiming to recover submerged macrophytes and clear water conditions.
化学除磷（P）与沉水植物移植相结合已广泛应用于湖泊修复，因为它比单独使用任何一种方法的效果都要强。然而，化学物质在与沉水植物结合使用时对 P 固定的剂量效应，以及化学物质对沉水植物生长的影响在很大程度上仍不清楚。在这项研究中，我们在户外中观实验中研究了水柱和沉积物中的 P 固定以及沉水植物对镧改性膨润土（LMB）的响应，在所有中观实验中移植了密齿苦草，并分别添加了四种剂量的 LMB：对照（无 LMB）、低剂量（570 g m）、中剂量（1140 g m）和高剂量（2280 g m）。结果表明，与单独使用密齿苦草相比，LMB 剂量和密齿苦草的组合使水柱中的总磷（TP）降低了 32%-38%，而三种 LMB 处理之间没有显著差异。水相可溶解性反应磷、二维扩散梯度薄膜（DGT）-可利用磷浓度和 0-1 cm 沉积物层中的磷转化在 LMB 剂量梯度上表现出相似的趋势。此外，LMB 以剂量依赖的方式抑制植物生长并减少矿物元素（即钙、锰、铁和镁）的吸收。LMB 可能通过为新分株创造 P 缺乏风险和干扰矿物元素的吸收来降低植物生长。考虑到 LMB 对 P 固定的剂量效应及其对大型植物生长的负面影响，我们建议在湖泊修复中采用“小剂量、频繁应用”的 LMB 应用方法，以恢复沉水植物和清水条件。
