Unveiling the Presence\nof Short- and Medium-Chain\nChlorinated Paraffins in the Hadal Trenches of the Western Pacific\nOcean

This study delves into the unexplored distribution and\naccumulation\nof chlorinated paraffins (CPs), pervasive industrial contaminants\nused as flame retardants and plasticizers, within the hadal trenches,\nsome of Earth’s most isolated marine ecosystems. Analysis of\nsediments from the Mussau (MS) and Mariana trench (MT) reveals notably\nhigh total CP concentrations (∑SCCPs + ∑MCCPs) of 10,963\nand 14,554 ng g<sup>–1</sup> dw, respectively, surpassing those\nin a reference site in the western Pacific abyssal plain (8533 ng\ng<sup>–1</sup> dw). In contrast, the New Britain Trench (NBT)\nexhibits the lowest concentrations (2213–5880 ng g<sup>–1</sup> dw), where CP distribution correlates with clay content, δ<sup>13</sup>C and δ<sup>15</sup>N values, but little with total\norganic carbon and depth. Additionally, amphipods from these trenches\ndisplay varying CP levels, with MS amphipods reaching concerning concentrations\n(8681–16,138 ng g<sup>–1</sup> lw), while amphipods\nin the MT-1 site show the lowest (4414–5010 ng g<sup>–1</sup> lw). These bioaccumulation trends appear to be primarily influenced\nby feeding behaviors (δ<sup>13</sup>C) and trophic levels (δ<sup>15</sup>N). Utilizing biota-sediment accumulation factor values and\nprincipal component analysis, we discern that CPs in sediment may\ncome from surface-derived particulate organic matters, while those\nin amphipods may come from the above carrion. Our findings elucidate\nthe profound impacts of the emerging pollutants on the Earth’s\nleast explored marine ecosystems.