On-ship aerosol sampling was conducted on the R/V Dong Fang Hong-3 during a cruise to the western North Pacific from October 31 to December 1, 2019 (Chief Scientist Zaohui, Chen of the Ocean University of China, (chenzhaohui@ouc.edu.cn)). The ship sailed from Qingdao, China (36°1'56"N, 120°13'56"E) to the western North Pacific (14°0'2"N, 149°35'56"E). Two portable aerosol particle samplers (model 2030, Qingdao Laoying Environmental Technology Co.) were used with a filter size of 9 centimeters (cm) O.D. (outer diameter). The GF/F filters were precombusted (550 degrees Celsius (°C), 4 hours) before use, and the sampling period was 18 to 72 hours for each filter with an air flow rate of 100 liters pers minute (L/min) based on the cruise track. A total of 16 samples were collected during the cruise.

For the aerosol samples, measurements were made of the concentrations of aerosol particulate organic carbon (POC), total nitrogen (TN), and carbon isotope (¹³C and ¹⁴C) compositions of aerosol OC. All measurements were conducted at the Center for Isotope Geochemistry and Geochronology (CIGG) at the Qingdao National Laboratory for Marine Science and
Technology (QNLM) in Qingdao, China. For atmospheric POC measurements, a cut piece of filter containing particles was acidifed first with 10% high-purity HCl to remove inorganic carbon and then dried at 50°C. Concentrations of POC and TN were measured using an elemental analyzer (Elementar vario Isotope select) with analytical standard deviations of ±0.03% for OC, and ±0.04% for TN (n = 6). The δ¹³C values of POC were measured using a Thermal Delta V Advantage isotope ratio mass spectrometer coupled with an Elemental Analyzer-IsoLink CN. Values of δ¹³C were reported in ‰ relative to ¹³C standards (IAEA-CH-3, cellulose, and IAEA-600 caffeine), and the analytic precision was ≤0.2‰ (n = 10). For POC ¹⁴C measurements, the pretreated filters were placed separately in double quartz tubes (precombusted at 850°C for 2 hours) with CuO and Ag wires added. The tubes were then evacuated on a vacuum line, flame sealed, and combusted at 850°C for 2 hours (Druffel et al., 1992). CO₂ resulting from POC oxidation was collected cryogenically and quantified monometrically on a vacuum line. The purified CO₂ was converted to graphite using the closed tube iron reduction method (Xu et al., 2007; Walker et al., 2019) and ¹⁴C was measured by accelerator mass spectrometry (AMS, NEC 0.5MV XCAMS). Δ¹⁴C results were reported, and conventional radiocarbon ages [years before present (BP)] were calculated based on the study by Stuiver and Polach (1977).