Spatial distribution and accumulation patterns of quaternary ammonium compounds (QACs) in surface sediments of Lake Sihwa, South Korea

초록

Quaternary ammonium compounds (QACs) are widely used as disinfectants in industrial and consumer products. In this study, we investigated the distribution and accumulation patterns of 19 QACs in surface sediments of Lake Sihwa and its tributary creeks. Additionally, novel monoalkyl/dialkyl index (MDI) and QAC Accumulation Scenario Model (QASM) were applied to elucidate the role of total organic carbon (TOC) derived retention, and the distinction between recent and legacy contamination. The Σ19QAC concentrations in sediment ranged from 17.8 to 48,900 ng/g-dw (median 645 ng/g-dw), with the highest median concentrations found in inland creek sediments. Dialkyldimethylammonium compounds (DDACs) accounted for 71 % of the total QAC concentration, followed by alkyltrimethylammonium compounds (ATMACs, 17 %) and benzylalkyldimethylammonium compounds (BACs, 12 %). The concentrations of long alkyl-chain DDACs (C18) and ATMACs (C16 and C18) were higher than those of short-chain homologs (C8–C14). The accumulation of QACs in sediments was influenced by local inputs and TOC content, as revealed by the QASM model. Multivariate analyses revealed specific patterns of QAC concentrations within each location and homolog-specific distribution, with C16- and C18-DDACs dominating the inner reaches of lake sediments, while C10-BAC and C8-DDAC dominated the homolog profile in creek sediments. A clear spatial gradient in QAC concentrations suggested transport of these chemicals from creeks to lake inshore, with subsequent transport to offshore waters. Therefore, industrial creeks that act as major sources of QACs should be prioritized for future sediment monitoring and ecological risk assessment. © 2026 Elsevier Ltd

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