Sublacustrine faults discharge as an important source of nutrients into a tectonic lake

IF 3.6 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Chemical Geology Pub Date : 2025-08-13 DOI:10.1016/j.chemgeo.2025.123010

Weigang Su , Qiugui Wang , Yujun Ma , Xiuzhen Ma , Chengcheng Tian , Jinlong Wang

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Abstract

In tectonic lake systems, fault-driven lacustrine groundwater discharge (F-LGD) plays a critical role in regulating lacustrine water and nutrient budgets. This study quantifies F-LGD fluxes in Lake Qinghai by analyzing the spatial distribution of radium isotopes (²²³Ra, ²²⁴Ra) and stable isotopes (δ¹⁸O, δD) across horizontal and vertical gradients during July 25–August 19, 2021. Results demonstrate that mean radium activity in bottom layers exceeds pelagic zones (attributable to sediment diffusion and an additional Ra source), with significantly elevated activities and δ¹⁸O enrichment in bottom waters proximal to sublacustrine faults. These findings confirm that sublacustrine faults act as conduits for groundwater influx. The estimated F-LGD flux ranges from 9.56 × 10⁸ to 13.24 × 10⁸ m³ yr⁻¹, equivalent to 60–80 % of combined precipitation and surface runoff inputs. Critically, fault-derived fluxes of dissolved inorganic phosphorus (DIP), dissolved inorganic nitrogen (DIN), and dissolved silica (DSi) surpass those from atmospheric wet deposition and riverine sources. To our knowledge, this work provides the first quantitative assessment of sublacustrine fault-driven water transport in a tectonic lake, demonstrating that F-LGD is a dominant controller of hydrological and biogeochemical cycling in such systems. Further investigation of fault-mediated material exchange is essential to refine lake-scale circulation models.

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湖底断裂为构造湖泊提供了重要的营养物质来源

在构造湖泊系统中，断层驱动的湖泊地下水排放在调节湖泊水和营养收支中起着关键作用。通过分析青海湖2021年7月25日至8月19日期间镭同位素（223Ra、224Ra）和稳定同位素（δ18O、δD）在水平和垂直梯度上的空间分布，定量研究了青海湖F-LGD通量。结果表明，由于沉积物扩散和额外的Ra源，海底的平均镭活度超过了上层区域，在靠近湖底断裂的底部水域，镭活度和δ18O富集显著升高。这些发现证实了湖底断层是地下水流入的管道。估算的F-LGD通量范围为9.56 × 108 ~ 13.24 × 108 m3 yr - 1，相当于降水和地表径流联合输入的60 - 80%。重要的是，断层衍生的溶解无机磷（DIP）、溶解无机氮（DIN）和溶解二氧化硅（DSi）的通量超过了大气湿沉积和河流来源的通量。据我们所知，这项工作首次提供了构造湖泊湖底断裂驱动的水输送的定量评估，表明F-LGD是此类系统中水文和生物地球化学循环的主要控制者。进一步研究断层介导的物质交换对完善湖泊尺度环流模型至关重要。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Chemical Geology 地学-地球化学与地球物理

CiteScore

7.20

自引率

10.30%

发文量

374

审稿时长

3.6 months

期刊介绍： Chemical Geology is an international journal that publishes original research papers on isotopic and elemental geochemistry, geochronology and cosmochemistry. The Journal focuses on chemical processes in igneous, metamorphic, and sedimentary petrology, low- and high-temperature aqueous solutions, biogeochemistry, the environment and cosmochemistry. Papers that are field, experimentally, or computationally based are appropriate if they are of broad international interest. The Journal generally does not publish papers that are primarily of regional or local interest, or which are primarily focused on remediation and applied geochemistry. The Journal also welcomes innovative papers dealing with significant analytical advances that are of wide interest in the community and extend significantly beyond the scope of what would be included in the methods section of a standard research paper.