The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, 5 Yushan Road, Qingdao, 266003, Shandong, China.
Function Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, 1 Wenhai Road, Qingdao, 266003, Shandong, China.
Environ Sci Pollut Res Int. 2023 Jan;30(2):4245-4257. doi: 10.1007/s11356-022-22542-7. Epub 2022 Aug 15.
Human activities and climate change input more reactive nitrogen into alpine lakes. Alpine saline lakes are usually located in endorheic watersheds at high-altitude areas, with no other drainage methods than evaporation, and are prone to accumulate nutrients. Meanwhile, alpine saline lakes are usually oligotrophic and sensitive to reactive nitrogen inputs, and even modest reactive nitrogen inputs may have significant effects on them, such as eutrophication. Nitrate is the main form of reactive nitrogen in lakes; therefore, clarifying the sources and transformations of nitrate in alpine saline lakes is important to prevent or mitigate eutrophication in alpine saline lakes. In this study, the sources and transformations of nitrate in Qixiangcuo Lake and its inflow rivers in the northern Tibetan Plateau were identified using dual nitrate isotopes and hydrochemistry. The results show that (1) the ranges of NO concentrations, δN - NO, and δO - NO values were 3.6 ~ 26.1 μg/L, - 10.5 to + 6.0‰, and - 10.4 to + 9.2‰ in Qixiangcuo Lake and 194.4 ~ 728.1 μg/L, + 5.8 ~ + 8.8‰, and - 1.9 to + 2.4‰ in its inflow rivers, respectively. The NO concentrations and δN - NO values were significantly lower in Qixiangcuo Lake than in its inflow rivers (P < 0.05). (2) The main sources of nitrate in both surface water and bottom water of Qixiangcuo Lake were ammonium in atmospheric deposition (mean probability estimate (MPE) 41.0% and 32.2%, respectively) and livestock manure (MPE 28.9% and 21.7%, respectively). The main sources of nitrate in the inflow rivers of Qixiangcuo Lake were domestic sewage (MPE 35.7%) and livestock manure (MPE 29.6%). (3) The main nitrogen transformation process in Qixiangcuo Lake was nitrification. The conservative mixing of multiple sources controlled the nitrate concentration and isotopic composition of Qixiangcuo Lake. Improvement in grazing area planning and the installation of sewage treatment facilities are effective measures to prevent eutrophication in Qixiangcuo Lake and its inflow rivers.
人类活动和气候变化向高山湖泊输入了更多的活性氮。高山盐湖通常位于高海拔地区的内陆流域，除蒸发外没有其他排水方式，容易积累养分。同时，高山盐湖通常是贫营养的，对活性氮输入敏感，即使是适度的活性氮输入也可能对其产生重大影响，例如富营养化。硝酸盐是湖泊中活性氮的主要形式；因此，阐明高山盐湖中硝酸盐的来源和转化对于防止或减轻高山盐湖的富营养化非常重要。在本研究中，使用双硝酸盐同位素和水化学方法确定了青藏高原北部七香河及其入流河流中硝酸盐的来源和转化。结果表明：(1)七香河及其入流河的硝酸盐浓度、δN-NO 和 δO-NO 值范围分别为 3.626.1μg/L、-10.5 至+6.0‰和-10.4 至+9.2‰，以及 194.4728.1μg/L、+5.8 至+8.8‰和-1.9 至+2.4‰。七香河的硝酸盐浓度和 δN-NO 值明显低于其入流河（P<0.05）。(2)七香河表层水和底层水硝酸盐的主要来源分别是大气沉降中的铵盐（平均概率估计值（MPE）分别为 41.0%和 32.2%）和牲畜粪便（MPE 分别为 28.9%和 21.7%）。七香河入流河硝酸盐的主要来源是生活污水（MPE 为 35.7%）和牲畜粪便（MPE 为 29.6%）。(3)七香河的主要氮转化过程是硝化作用。多种来源的保守混合控制了七香河的硝酸盐浓度和同位素组成。改善放牧区规划和安装污水处理设施是防止七香河及其入流河富营养化的有效措施。
