Evaluation of heavy metal contamination in coastal aquifer groundwater of Alappuzha district (Kerala, India) using OSPRC framework

Trace amounts of certain heavy metals, including iron, zinc, and copper, are essential for human health; however, many others are toxic even at low concentrations, posing significant risks in vulnerable coastal regions. This study assessed concentrations of heavy metals in shallow groundwater (1–4 m depth) along the coastline of Alappuzha, Kerala (India) during the pre- (2021) and post-monsoon (2022) seasons, applying the Origin-Source-Pathways-Receptor-Consequence (OSPRC) framework. Concentrations of arsenic (As), cadmium (Cd), strontium (Sr), nickel (Ni), copper (Cu), iron (Fe), barium (Ba), chromium (Cr), lead (Pb), aluminum (Al), manganese (Mn), and cobalt (Co) were analyzed with respect to the WHO (2017) standards. Arsenic in 8–10% samples and aluminum in 8% samples across the seasons, exceeding the WHO limits, were largely from commercial debris, agricultural runoff, domestic sewage, and tourism-related activities. The elevated iron (4–8% of samples), however, was predominantly geogenic. The heavy metal pollution index (HMPI) indicated that 32% of pre-monsoon and 34% of post-monsoon samples exhibited medium to high pollution levels with the critical hotspots at Ambalapuzha, Anandheswaram, and Thottapalli for arsenic; Alappuzha, Kanjikuzhi and Paravoor for aluminum; and Paravoor, Alappuzha, Chennakari, and Ambalapuzha for iron. The presence of these trace metals at unsafe levels underscores an urgent need for comprehensive quality monitoring and mitigation strategies in this coastal zone. The findings in this study deliver a replicable model for integrating risk-based assessment frameworks like OSPRC into groundwater management practices for policymakers, public health authorities, and local communities to prioritize interventions for developing sustainable and long-term solutions.