Sreelesh R, Rani G V Asha, Sreelash K, Maya K
National Centre for Earth Science Studies (NCESS), Thiruvananthapuram, India.
Cochin University of Science and Technology, Kochi, India.
Environ Geochem Health. 2025 Jul 31;47(9):349. doi: 10.1007/s10653-025-02658-8.
Monsoon-driven hydrological variability and anthropogenic pressures in tropical critical zones pose significant threats to water quality and public health. This study investigates the spatial and temporal distribution, sources, and human health risks of trace and heavy metals at the Munnar Critical Zone Observatory in the Western Ghats, India. Through integration of hydrogeochemical analyses, land use-land cover data, and health risk frameworks, revealed pronounced seasonal contrasts: monsoon rains drive two-threefold increases in Al, Fe, Pb, and Zn in surface waters due to intensified erosion of hornblende-biotite gneiss and agrochemical runoff from tea and eucalyptus plantations. Groundwater chemistry reflects aquifer lithology, while Cd and Pb enrichment during monsoon recharge is significantly influenced by anthropogenic sources. Multivariate statistical analyses attribute (PCA, HCA) 60-75% of metal variability to geogenic weathering (PC1: Al, Fe, Ti) and 15-25% to anthropogenic sources (PC3: Cd, Pb from agrochemicals). Pollution indices (WPI, HPI, HEI) classify contamination as low-to-moderate overall, yet Fe exceeds thresholds in rivulets during monsoon (notably at S1 and S6). Health risk assessments prioritise Co, Mn, and Pb as non-carcinogenic threats (HI < 1), while Cr and Cd pose significant carcinogenic risks, with children's ingestion risk 3-4 times higher than adults. Concentration-discharge relationships indicate consistent chemodynamic metal transport in river systems, contrasting with seasonally-variable behaviour in rivulets, where chemostasis occurs for specific elements during pre-monsoon. These findings underscore the need for regulating agrochemical use in erosion-prone catchments and prioritising Cr and Cd monitoring in vulnerable sites. This provides a holistic framework for managing water security in climate-sensitive, human-altered landscapes globally.
季风驱动的热带关键带水文变化和人为压力对水质和公众健康构成重大威胁。本研究调查了印度西高止山脉穆纳关键带观测站痕量金属和重金属的时空分布、来源及对人类健康的风险。通过整合水文地球化学分析、土地利用-土地覆盖数据和健康风险框架，揭示了明显的季节差异：季风降雨导致地表水铝、铁、铅和锌含量增加两到三倍，这是由于角闪石-黑云母片麻岩侵蚀加剧以及茶园和桉树林的农业化学径流所致。地下水化学反映了含水层岩性，而季风补给期间镉和铅的富集受人为来源的显著影响。多变量统计分析（PCA、HCA）将60%-75%的金属变化归因于地质风化（PC1：铝、铁、钛），15%-25%归因于人为来源（PC3：来自农用化学品的镉、铅）。污染指数（WPI、HPI、HEI）总体将污染分类为低到中度，但季风期间小溪中的铁超过阈值（特别是在S1和S6）。健康风险评估将钴、锰和铅列为非致癌威胁（HI<1），而铬和镉构成重大致癌风险，儿童摄入风险比成年人高3-4倍。浓度-流量关系表明河流系统中金属化学动力传输一致，这与小溪中季节性变化的行为形成对比，在季风前特定元素在小溪中发生化学稳定。这些发现强调了在易侵蚀集水区规范农用化学品使用以及在脆弱地点优先监测铬和镉的必要性。这为全球气候敏感、人类改变的景观中的水安全管理提供了一个整体框架。
