Yuan Hezhong, Wang Haixiang, Cai Yiwei, Yin Hongbin, Zeng Qingfei, Liu Enfeng, Li Qiang, Wang Yu
Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China.
Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China.
Water Res. 2023 Oct 15;245:120661. doi: 10.1016/j.watres.2023.120661. Epub 2023 Sep 22.
The reduction of exogenous emissions of phosphorus (P) is a crucial measure for resolving eutrophication in lakes. However, the input of terrigenous materials still potentially contributes to an increase of P load in lake systems. In this study, we examined the phosphate oxygen isotope (δO) of various P fractions in soils and sediments in a small lake watershed, namely, Shijiuhu watershed. The high-resolution in-situ diffusive gradients in thin films (DGT) technology was also used to survey the dynamic processes of P diffusion from sediment particles to the water. The results demonstrated that lighter δO values (16.2-19.5‰) for individual P fractions in lake sediments were detected compared to other land-use patterns, indicating the cumulative biological P recycling on anaerobic condition. Fe bound P (Fe-P) overall had heavier δO values (17.3-24.8‰) than some of Ca bound P (Ca-P) and equilibrium values, suggesting that Fe-P conserved the parental isotope signatures from terrigenous source and could act as the ideal tracer for the lake sediments. The mixing effect of terrigenous detrital input and biological mineralization made the source identification uncertain by using Ca-P, which had a wider range of δO values (13.0-26.6‰). Additionally, significantly positive correlation (r = 0.551-0.913, p<0.05) between soluble reactive P (SRP) and Fe in interstitial water obtained using DGT measurement revealed the conspicuous release and desorption of solid Fe-P toward the water. High diffusion fluxes from the sediments toward the overlying water further demonstrated that the desorption of Fe-P in the soil-originated sediments toward the solution conspicuously facilitated the accumulation of SRP in lake water. The first-time application of δO isotope combined with in-situ DGT techniques certified that it's feasible for the contribution confirmation from terrigenous to lacustrine environments, and presented the direct evidence for management strategy making about P control and eutrophication restoration at the catchment scale of lakes.
减少磷（P）的外源排放是解决湖泊富营养化的关键措施。然而，陆源物质的输入仍可能导致湖泊系统中磷负荷增加。在本研究中，我们检测了一个小型湖泊流域——石臼湖流域土壤和沉积物中各种磷组分的磷酸盐氧同位素（δO）。还采用了高分辨率原位薄膜扩散梯度（DGT）技术来研究磷从沉积物颗粒向水体扩散的动态过程。结果表明，与其他土地利用模式相比，湖泊沉积物中各磷组分的δO值较轻（16.2 - 19.5‰），表明在厌氧条件下存在累积的生物磷循环利用。总体而言，铁结合态磷（Fe-P）的δO值（17.3 - 24.8‰）比一些钙结合态磷（Ca-P）和平衡值更重，这表明Fe-P保留了陆源的母本同位素特征，可作为湖泊沉积物的理想示踪剂。陆源碎屑输入和生物矿化的混合效应使得利用δO值范围较宽（13.0 - 26.6‰）的Ca-P进行源识别变得不确定。此外，利用DGT测量得到的间隙水中可溶性活性磷（SRP）与铁之间存在显著正相关（r = 0.551 - 0.913，p < 0.05），这表明固体Fe-P向水体有明显的释放和解吸。沉积物向上覆水体的高扩散通量进一步表明，土壤源沉积物中Fe-P向溶液的解吸显著促进了湖水中SRP的积累。首次将δO同位素与原位DGT技术结合应用证明，确定陆源对湖泊环境的贡献是可行的，并为湖泊流域尺度上磷控制和富营养化修复的管理策略制定提供了直接证据。
