Fengxin Kang

Jiaodong Peninsula is one of the regions with the most abundant medium–low-temperature convective geothermal resources in the eastern coastal area of China. Analyzing geothermal fluid characteristics can help understand its hydrochemical discharge characteristics and renewal capacity, and these characteristics also exhibit distinct geochemical symmetry that reflects the genesis and evolution of geothermal systems. In this study, we conducted a water quality analysis of 15 natural hot spring geothermal fluids, as well as their adjacent bedrock and Quaternary water, in the Jiaodong Peninsula. We measured deuterium and oxygen isotopes, and the γ Na/γ Cl and γ SO₄/γ Cl ratios of geothermal fluids, focusing on the geochemical symmetry of these indicators to reveal the evolutionary rules of geothermal fluids. The hydrochemical types of geothermal fluids in the Jiaodong Peninsula included Cl–Na, Cl–Na·Ca, HCO₃·SO₄–Na, and SO₄·HCO₃–Na, with mineralization degrees of 0.45–7.68 g/L and pH values of 7.3–8.63. The geothermal fluid primarily originated from the infiltration recharge of atmospheric rainfall and had no hydraulic connection with the shallow Quaternary water and adjacent bedrock water near the geothermal field. The geothermal fluid in the study area had not yet reached water–rock equilibrium. For geothermal fields with higher γ Na/γ Cl and γ SO₄/γ Cl ratios, the corresponding geothermal fluid circulation depth was relatively shallow, indicating a poorly sealed hydrodynamic environment with strong renewal capacity, where the geothermal fluid is in a continuous supply–runoff–discharge process. The γ Na/γ Cl and γ SO₄/γ Cl ratios of some geothermal fields were close to those of seawater; this symmetric difference was caused by the large circulation depth and long residence period of the geothermal fluid, which had experienced a high degree of decarbonization. Our findings on the hydrochemical characteristics and geochemical symmetry of medium–low-temperature geothermal fluids in the Jiaodong Peninsula will help deepen the understanding of the formation and evolutionary mechanism of this type of geothermal resource.

The geothermal system in the Jiaodong Peninsula is situated within a continent–ocean transition zone, where complex interactions among meteoric water, geothermal fluids, and seawater produce diverse hydrogeochemical and isotopic signatures, complicating geothermal resource assessment and sustainable development. To constrain recharge sources and seawater mixing mechanisms, geothermal water samples were systematically collected from 15 geothermal fields and analyzed using integrated hydrogeochemical methods and multi-isotope tracers (δD–δ¹⁸O, δ³⁴S-SO₄²⁻, ⁸⁷Sr/⁸⁶Sr, and ³H). The results show that geothermal waters are predominantly recharged by meteoric precipitation, with δD–δ¹⁸O values distributed along the meteoric water line, while low d-excess values indicate prolonged circulation and significant water–rock interaction. Seawater mixing exhibits marked spatial heterogeneity: only 5 of the 15 fields show detectable marine influence. Chloride-based calculations suggest apparent seawater fractions of up to ~34% in BQ and <4% in DY, whereas the remaining fields show negligible mixing. Sulfur and strontium isotopes indicate contributions from external sulfate sources and continued water–rock interaction rather than simple mixing with modern seawater. Low tritium contents further imply involvement of deeply circulated paleo-seawater. The system is therefore interpreted as a fault-controlled seawater-mixing geothermal system, providing insights into coastal geothermal evolution and resource evaluation.

The development of the coastal economy, coupled with global climate change, has gradually made drought one of humanity’s major disasters. It causes significant harm to both the natural environment and the socioeconomic development of coastal areas. This study aims to combine deep learning algorithms and CMIP6 models to build a prediction method for hydrological drought under climate change in this area. The changes of regional hydrological drought in mid-century and late-century were analyzed, and the hydrological drought was calculated using Standardized Runoff Index (SRI) at different time scales. And then we use the copula function to calculate the joint recurrence period of mid-century hydrological drought. In this study, a better simulation algorithm EMD-LSTM was constructed to predict the change of hydrological drought in the Dagu River Basin in mid-century and late-century. The results show that the relative change in annual precipitation varied from 11 to 25% compared with the historical averages across both the mid- and late-century periods. Meanwhile, monthly average temperatures were all higher than historical averages, with a maximum increase of 3.8 °C (in the late-century under SSP5-8.5). The future trend of drought under different scenarios showed alternating dry and wet characteristics. Drought conditions were more severe in the mid-century compared to the end of the late-century. As the time scale increased, drought intensity decreased, but drought duration increased. This study provides a new potential method for accurate prediction of drought, offering a scientific basis for water resource management and protection.

《地球科学》(ISSN 1000-2383;CN42-1874/P) (原刊名《地球科学——中国地质大学学报》ISSN 1000-2383;CN42-1233/P)，创刊于1957年，是由教育部主管、中国地质大学主办的综合性地学学术理论期刊，月刊，2015年改名为《地球科学》,她以反映中国地质大学教学与科研最新的、高水平的基础地质、应用地质、资源与环境地质及地学工程技术研究成果为主要任务。