Fractionation of ultrafine particles from marine sediment for organic geochemical measurement

In traditional grain-size separation of marine sediment using the sieve technique, the majority of organic matter (OM) in the ultrafine sediment is yet hardly further separated. In this study, we suggest an inertial sieving method that utilizes an ultrafine particle separator (UPS), which consists of a suspended particle generator (SPG) combined with a particle size separating device (PSSD), to separate ultrafine particles from marine sediments. Specifically, our method can fractionate ultrafine particles (< 10 μm) into eight different grain size categories: 0.43–0.65, 0.65–1.10, 1.10–2.10, 2.10–3.30, 3.30–4.70, 4.70–5.80, 5.80–9.00, and 9.00–10.00 μm. We evaluate the effectiveness of this method in fractionating ultrafine marine sediment from the China Marginal Sea. Our study find that the inertial sieving method achieved a high mass recovery rate of 77.7–88.7% and a sieving accuracy of 75–94% for sediment samples. Additionally, we measure total organic carbon (OC) and stable carbon isotopes of OM associated with these eight ultrafine sediments. Overall, we suggest that the inertial sieving method has a high potential to effectively fractionate the marine sediments with particle sizes below 10 μm for further organic geochemical analysis on these grain size fractionated sediments.