Geng Hao, Xiong Guiyao, Liu Mengwen, Han Cong, Cheng Yi, Wu Jichun, Cao Shaohua, Zhu Xiaobin
Key Laboratory of Surficial Geochemistry of Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.
Key Laboratory of Surficial Geochemistry of Ministry of Education, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China; Key Laboratory of Coastal Science and Integrated Management, Ministry of Natural Resources, Qingdao, Shandong Province 266061, China.
J Hazard Mater. 2025 Jun 16;495:138961. doi: 10.1016/j.jhazmat.2025.138961.
Nitrate dynamics in the coastal hydrological system is concerned with the impact of nitrate levels on ecological stability and plays an important role in the global nitrogen cycle. However, the complex nitrate source and transport processes in the coastal area and the contribution of nitrogen cycle transformation processes make it a challenge to reveal the nitrate dynamics in the coastal hydrological system. In this study, we investigated the effects of land use types and hydrological interactions on nitrate dynamics in the coastal region using nitrogen composition combined with multi-isotope and Bayesian mixing modeling, focusing on the differences in paleo-saltwater intrusion area (PSIA) and modern seawater intrusion area (MSIA). The results showed that for nitrate sources in PSIA, soil N contributed the highest proportion (45.8% - 77.7%), while the highest proportion is manure and sewage (36.0% - 45.0%) in MSIA. Land use type is the key factor controlling the nitrate dynamics by changing the source and hydrological interaction process. The main source in saline lands is soil N, while manure and sewage are the main source in urban lands. In agricultural lands, nitrate sources are mainly a mixture of fertilizer N, soil N, manure and sewage. Compared with modern seawater intrusion, factors such as deeper burial and strong closure of palaeo-saltwater have led to a slowdown in nitrogen source input, making soil N the main source in PSIA. Nitrification can be promoted within a certain range of TDS in MSIA and can be inhibited when TDS exceeds this range in PSIA. Denitrification was inhibited with elevated TDS in both areas. In addition, nitrification is suppressed in agricultural lands under the influence of palaeo-saltwater intrusion, resulting in lower levels of nitrate pollution than that in MSIA. Nitrate levels here are less related to external inputs and more related to internal nitrate accumulation.
沿海水文系统中的硝酸盐动态与硝酸盐水平对生态稳定性的影响有关，并且在全球氮循环中发挥着重要作用。然而，沿海地区复杂的硝酸盐来源和输送过程以及氮循环转化过程的贡献，使得揭示沿海水文系统中的硝酸盐动态成为一项挑战。在本研究中，我们利用氮组成结合多同位素和贝叶斯混合模型，研究了土地利用类型和水文相互作用对沿海地区硝酸盐动态的影响，重点关注古盐水入侵区（PSIA）和现代海水入侵区（MSIA）的差异。结果表明，对于PSIA中的硝酸盐来源，土壤氮贡献比例最高（45.8% - 77.7%），而在MSIA中比例最高的是粪便和污水（36.0% - 45.0%）。土地利用类型是通过改变来源和水文相互作用过程来控制硝酸盐动态的关键因素。盐碱地的主要来源是土壤氮，而城市土地的主要来源是粪便和污水。在农业用地中，硝酸盐来源主要是化肥氮、土壤氮、粪便和污水的混合物。与现代海水入侵相比，古盐水埋藏更深和封闭性更强等因素导致氮源输入放缓，使得土壤氮成为PSIA中的主要来源。在MSIA中，一定范围内的总溶解固体（TDS）可促进硝化作用，但当TDS超过该范围时，PSIA中的硝化作用会受到抑制。两个区域的反硝化作用均随TDS升高而受到抑制。此外，在古盐水入侵影响下，农业用地中的硝化作用受到抑制，导致硝酸盐污染水平低于MSIA。这里的硝酸盐水平与外部输入的关系较小，而与内部硝酸盐积累的关系更大。
