Uncovering Hidden Pollution: Diffuse Contaminant Sources in a Sparsely Industrialized Estuarine System

Understanding sediment contamination in low-industrial
activity
areas remains a critical but understudied issue, particularly in estuarine
ecosystems subject to diffuse pollution sources. This study employed
nontarget screening with high-resolution mass spectrometry to analyze
sediment samples from Ganggu Estuary, South Korea, to evaluate the
composition and distribution of sediment contaminants in a region
lacking heavy industry but influenced by agriculture, fisheries, and
tributary discharges. The investigation revealed that contamination
stems from multiple sources, including streams, agricultural runoff,
and fish market discharges. A total of 678 chemicals were identified,
including human and veterinary drugs (8.7%), food additives (6.5%),
pesticides (2.8%), and PFAS (1.9%), with spatial variability confirmed
by total organic carbon (TOC) analysis. Notably, this study is the
first to report the detection of dinoseb, a banned herbicide in estuarine
sediments, identified with high confidence alongside key pollutants
such as 6:2 fluorotelomer sulfonic acid and 2,4-di-tert-butylphenol. We linked contamination hotspots to U-shaped river
bends, streamwater and sediment inputs, and agricultural runoffs,
and highlight the role of natural processes in pollutant deposition
in a region where heavy industry is absent, yet diffuse sources still
drive significant contamination.