Enrichment factors and deterministic-probabilistic health risks of fluoride and nitrate in geothermal water: a case study from Northwestern Shandong, China.

Authors

Yuqi Zhang, Wei Liang, Meng Zhu, Ruoyi Huang, Zongjun Gao, Lu Xia, Jiutan Liu, Jichu Zhao, Xunchang Yang, Jinliang Du

Published in

Environmental monitoring and assessment. Volume 198. Issue 7. Jun 27, 2026. Epub Jun 27, 2026.

Abstract

The therapeutic and health benefits of geothermal water are widely recognized; its specific chemical components, particularly fluoride (F^-) and the increasing levels of nitrate (NO₃^-), have raised growing concerns about potential risks. Nevertheless, scientific understanding of the enrichment mechanisms and associated health threats of F^- and NO₃^- in geothermal water remains limited in Northwestern Shandong Province (NWS). This study systematically investigates geothermal waters in NWS by integrating hydrogeochemical analysis with deterministic-probabilistic health risk assessment models. The objectives are to reveal their hydrochemical characteristics, elucidate the enrichment mechanisms of F^- and NO₃^-, and evaluate their potential non-carcinogenic health risks to humans. The results indicate that the enrichment of F^- in NWS geothermal water is primarily governed by natural hydrogeochemical processes, manifested as the synergistic effects of fluoride dissolution, calcium-bearing mineral precipitation, alkaline environment, and positive cation exchange. In contrast, the elevated NO₃^- levels are clearly attributed to anthropogenic influences such as agricultural activities. Under the conventional exposure scenario of skin contact (e.g., bathing), both deterministic and probabilistic risk assessments consistently demonstrate that the non-carcinogenic risks for adults and children are generally acceptable (mean HI < 1, with zero exceedance probability). However, the critical risk arises from non-routine exposure pathways: assessment of accidental geothermal water ingestion reveals a significantly elevated non-carcinogenic risk for children, with the HQ exceedance probabilities (> 1) for F^- and NO₃^- reaching 44.25% and 43.68%, respectively, whereas the corresponding probabilities for adults are only 2.6% and 12.16%. Sensitivity analysis indicates that exposure duration and frequency (exposure opportunity) are the primary controlling factors for adults, whereas children exhibit extreme sensitivity to body weight parameters, with their lower exposure dose per unit body weight significantly amplifying health risks. This study reveals that accidental ingestion (especially by children) constitutes a significant but long-neglected health threat. Accordingly, it is recommended that geothermal resource management prioritize protective measures and educational interventions targeting children in areas lacking public awareness.

PMID:
42364028
Bibliographic data and abstract were imported from PubMed on 27 Jun 2026.

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