First determination of 1,4-dioxane and chlorinated solvents in sediment of Masan Bay in Korea.

1,4-Dioxane, a widely used industrial solvent and former stabilizer for chlorinated solvents, has emerged as a contaminant of global concern due to its persistence and toxicity. Although co-occurring with chlorinated solvents in groundwater and wastewater effluents, their presence in sediments has not been reported, due to absence of analytical method. This study developed a static headspace gas chromatography/mass spectrometry (HS-GC/MS) method for the simultaneous analysis of 1,4-dioxane and three chlorinated solvents, including 1,1,1-trichloroethane (TCA), 1,1-dichloroethene (1,1-DCE), and trichloroethylene (TCE), in marine sediment. Compared to solid phase extraction (SPE) after sonication method, the static HS-GC/MS method minimized compound loss and exhibited high sensitivity, with method detection limits (MDLs) below 0.13 ng/g wet weight and recoveries of 107-140 %. Developed method was applied to 23 sediment samples from Masan Bay, South Korea, and its inflowing streams. 1,4-Dioxane was mainly detected in stream sediments and estuarine areas (up to 0.96 ng/g), influenced by freshwater input and salinity barrier. Detection of 1,4-dioxane near a wastewater treatment plant (WWTP) outlet suggests effluent discharge as point source. In contrast, 1,1-DCE was widely distributed in the bay, due to atmospheric deposition. Risk assessment showed negligible ecological risk to sediment-dwelling organisms. These findings provide the first field evidence of differing environmental behaviors between 1,4-dioxane and chlorinated solvents in coastal environments and underscore the need for robust analytical methods for seawater.