The Characteristics of Methylsiloxane Distribution in the Marine Surface Sediment, Masan Bay, Korea, in August 2018 and Suggesting Directions for Further Studies

The present study determined the distribution of fifteen methylsiloxane compounds (total methylsiloxanes, TMSs), including four cyclic (CMSs) and eleven linear (LMSs), in the marine surface sediment of Masan Bay, Korea, in 2018. The levels ranged from 76.6 to 2320 (median 264 ± 680), 5.00 to 3570 (median 359 ± 1310), and 81.6 to 5890 (median 607 ± 1940) ng/g-dw., in ΣCMSs, ΣLMSs, and ΣTMSs, respectively. The CMSs: LMSs ratio was 34:66, and the most dominant compound was D5 (27%), followed by L11 (22%) and L12 (20%). Principal component and cluster analyses categorized the ten sampling points into four groups based on the point sources: Group A (MS1) representing the industrial wastewater from the Changwon National Industrial complex; Group B (MS2) representing the ship movements; and Groups C (MS3, MS5, MS6, and MS7) and D (MS4, MS8, MS9, and MS10) representing the organic carbons. The present study hypothesized that the missing link between the methylsiloxane levels in 2013 and 2021 was due to the considerable industry recession in the bay. This was verified by positive correlations between the median ΣCMSs and the monthly production, the median ΣLMSs and ΣTMSs and the monthly employment in the complex. However, the hypothesis should be supplemented with the following perspectives: (1) selecting the sampling areas representing only the industrial wastewater, (2) considering the seasonal fluctuations, (3) estimating half-lives, and (4) investigating time series. This study is the first to link methylsiloxane levels and social issues in the bay, providing insights into illuminating the distribution characteristics of various pollutants.