Source of settling particulate matter during summer in the northern Taiwan Strait and its impact on sedimentary record

The settling of suspended particulate matter is significant for the vertical transfer and burial of organic carbon. Using time-series sediment traps, we collected settling particulate matter in the near-bottom layer (8 mab... [ view full abstract ]

The settling of suspended particulate matter is significant for the vertical transfer and burial of organic carbon. Using time-series sediment traps, we collected settling particulate matter in the near-bottom layer (8 mab [meters above bed]) over eight continuous days in the continental shelf waters of the northern Taiwan Strait and analyzed the particle size, clay minerals, and particulate organic carbon. The observation results indicated that the deposition flux in the continental shelf waters during summer in the northeastern Taiwan Straits is 0.86 g/m2•d ~10.68 g/m2•d; the corrected deposition flux is lower than the measured value by approximately 4.5%~30.6%; the average silt and clay content in the settling particulate matter is 81.28% and 16.42%, respectively; the average content of illite, chlorite, kaolinite, and smectite in the clay minerals is 56.24%, 25.69%, 14.42%, and 3.65%, respectively; the particulate organic carbon (POC) content is 0.589%~0.741%, with an average of 0.646%; and the δ13Corg‰ value is -20.74‰~-22.61‰, with an average of -21.45‰. In addition, the δ13C org‰ indicated that the settling particulate matter was primarily from marine sources at a contribution rate of 70%~88% with a mean value of 82%. Settling particulate matter was primarily a result of the re-suspension of submarine sediment, and the contribution was 65%~85%, with an average of 76%. The upward movement of the bottom thermocline and halocline, which enhanced the mixing intensity of the bottom water bodies, increased the contribution of re-suspension to the settling particulate matter.