Water Research Institute, National Research Council, Via del Mulino, 19, 20861 Brugherio, Italy.
Water Research Institute, National Research Council, Via del Mulino, 19, 20861 Brugherio, Italy.
Sci Total Environ. 2023 Jan 15;856(Pt 2):159225. doi: 10.1016/j.scitotenv.2022.159225. Epub 2022 Oct 5.
This paper reports data from a southern-Italy reservoir (Lake Occhito) characterized by a strong riverborne sediment transport. Main hydrochemical, trophic, and nutrient variables were measured (over a twelve-month period) in both lake and tributaries. Lacustrine sediments were subjected to mineralogical characterization and to phosphorus fractioning, while a 6-day long batch experiment was carried out to evaluate the lake sediment orthophosphate adsorption capacity. A set of algal growth potential tests was also undertaken on the lake and its tributaries. Results highlight the presence of a strong gradient in nutrient availability among the inflows. Most of the nutrient loads were from the main tributary (20.3 t P a, 83 %), that showed the highest trophic potential (average: 56.8 mg L) and was nitrogen/phosphorus co-limited. The other inflows were phosphorus limited and characterized by a higher sediment transport. The lake showed the lowest nutrient concentrations (average total phosphorus: 21 μg P L) and was strongly phosphorus limited. Clays were the principal minerals in the lake sediments (51 %), while the main phosphorus fraction was apatite (~78 %). The batch experiment demonstrated the capability of the lake sediments to reduce orthophosphate concentrations in phosphorus-rich waters (initial orthophosphate: 320 μg P L; ~80 % reduction). The lake sediment orthophosphate kinetics of abatement was similar to that of a commercially available phosphorus sorbent (lanthanum modified bentonite), although the stability of phosphorus binding was higher for the commercial product. Theoretical average in-lake total phosphorus, chlorophyll-a, and transparency values, estimated through Vollenweider models, were approximately double of the average values measured in the lake. Therefore, the massive presence of riverborne clay sediments seems to markedly reduce the in-lake orthophosphate concentrations (and light penetration), inducing an overall lowering of the lake trophic state, as if the lake ecosystem were permanently subjected to a geo-engineering phosphorus sorbent treatment.
本文报告了来自意大利南部一个以河流输送大量沉积物为特征的水库（奥奇托湖）的数据。在 12 个月的时间里，对湖泊和支流的主要水化学、营养和营养变量进行了测量。对湖泊沉积物进行了矿物学特征和磷形态分析，并进行了为期 6 天的批量实验，以评估湖泊沉积物对正磷酸盐的吸附能力。还对湖泊及其支流进行了一组藻类生长潜力测试。结果突出了流入物中养分可用性的强烈梯度。大部分养分负荷来自主要支流（20.3 t P a，约 83%），该支流表现出最高的营养潜力（平均：56.8 mg L），并且氮/磷双限制。其他支流为磷限制，具有较高的沉积物输送。湖泊表现出最低的养分浓度（平均总磷：21 μg P L），且强烈受磷限制。粘土是湖泊沉积物中的主要矿物（51%），而主要的磷形态是磷灰石（78%）。批量实验表明，湖泊沉积物能够降低富磷水中的正磷酸盐浓度（初始正磷酸盐：320 μg P L；~80%减少）。湖泊沉积物中磷酸盐的消除动力学与商业可用的磷吸附剂（镧改性膨润土）相似，但商业产品的磷结合稳定性更高。通过伏伦威德尔模型估算的理论平均湖泊总磷、叶绿素-a 和透明度值约为湖泊实测平均值的两倍。因此，大量的河流输送粘土沉积物似乎显著降低了湖泊中的正磷酸盐浓度（和光穿透），导致湖泊整体营养状态降低，就好像湖泊生态系统一直受到地质工程磷吸附剂处理的影响一样。
