A High-Throughput Enrichment Device for Rapid Separation of Dissolved Organic Matter from Seawater

Marine dissolved organic matter (DOM) plays an important role in the global carbon cycle. However, the low DOM concentration in seawater makes it difficult to obtain sufficient DOM samples, which significantly limits the research on DOM chemical compositions, reactivity and transformation mechanisms. To resolve this problem, this study designed and developed a high-throughput seawater DOM separation and enrichment system using tangential flow filtration (TFF). This system uses modified polyethersulfone (30 kDa) and polypiperazine amide (1 kDa) membrane packages, reaching a processing capacity of 500 L/h seawater, under cross-flow ratios of 4 and concentration factors >50. Three trials were performed to examine the performance of this system, processing and enriching DOM in 7000 L of surface seawater from the coastal waters. The enriched DOM samples were characterized using Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The DOM recovery rate is between 55.7%–70.3%, based on dissolved organic carbon measurement. The C/N ratio is close to the non-treated seawater. The enriched DOM exhibited a higher abundance of humus-like and terrestrial components. FT-ICR MS analysis indicated that the enriched DOM contains more nitrogenous compounds and codensed aromatic compounds, compared with the DOM extracted by the PPL-SPE. This study provides a high-throughput seawater DOM enrichment device that is capable of acquiring qualified and representative DOM samples in large quantities (g), which would significantly contribute to the research in both marine and aquatic DOM cycling.