碳酸氢盐型盐化与富营养化对淡水生态系统水质及碳存量的影响

Effects of Bicarbonate Salinization and Eutrophication on Water Quality and Carbon Inventory in Freshwater Ecosystems

摘要: 随着全球气候变化与人类活动加剧，淡水盐化与富营养化已成为高原湖泊面临的双重挑战。本研究通过构建室外中宇宙模拟实验，设计了0~2000 mg/L的碳酸氢钠浓度梯度及两种营养水平，重点探讨碳酸氢盐型盐化与营养水平对水体理化稳态(pH、溶解氧、溶解性无机碳、二氧化碳)、营养盐(总磷、总氮)及有机碳组分(溶解性有机碳)的交互作用。研究发现：1) 随着碳酸氢钠梯度增加，水体DIC、CO₂与pH显著上升，高营养组DIC与CO₂浓度在同盐度下始终低于低营养组。2) 总磷随盐度增加而升高，且在高营养下增长更显著；而总氮在各组间保持相对稳态。3) 高营养组在盐度低于1450 mg/L时表现出更高的产氧水平，但超过该阈值后，溶解氧急剧下降且DOC大量积累。研究揭示了营养水平对盐化响应的双重作用，为气候变化背景下湖泊的盐化管理与生态修复提供了科学依据。

Abstract: Driven by global climate change and intensifying human activities, freshwater salinization and eutrophication have emerged as dual challenges for plateau lakes. This study utilized outdoor mesocosm experiments to establish a sodium bicarbonate (NaHCO₃) gradient (0~2000 mg/L) across two nutrient levels. We investigated the interactive effects of bicarbonate salinization and nutrients on physicochemical stability (pH, dissolved oxygen [DO], dissolved inorganic carbon [DIC], and carbon dioxide [CO₂]), nutrient dynamics (total phosphorus [TP] and total nitrogen [TN]), and organic carbon components (dissolved organic carbon [DOC]). The findings indicate that: 1) While DIC, CO₂, and pH rose significantly with increasing NaHCO₃, the high-nutrient group consistently maintained lower DIC and CO₂ concentrations than the low-nutrient group at equivalent salinities. 2) TP increased with salinity, a trend significantly amplified under high-nutrient conditions, whereas TN remained relatively stable across all treatments. 3) The high-nutrient group exhibited higher oxygen production levels at salinities below 1450 mg/L; however, exceeding this threshold triggered a sharp decline in DO accompanied by substantial DOC accumulation. This study highlights the dual role of nutrient levels in modulating ecosystem responses to salinization, providing a scientific framework for lake management and ecological restoration in the context of global climate change.