Characteristics and sources of organic carbon in coastal and marine atmospheric particulates over East China

To understand the influences of emission sources, transport and environmental factors on the characteristics of organic carbonaceous aerosols in the marine area, organic carbon (OC) and water-soluble organic carbon (WSOC) were measured in atmospheric samples collected from the coastal region and over the Bohai and Yellow Seas from 2015 to 2016. Compared with the averages of 19.28 and 10.61 μg·m−3 in the coastal samples, the average concentrations of OC and WSOC decreased to 2.17 and 1.54 μg·m−3 in the marine aerosol samples, respectively. WSOC contributed 60% to OC in Qingdao, while 68.4% to OC over the ocean, suggesting that WSOC is likely influenced by the dissolved organic carbon (DOC) in surface seawater. The highest OC/EC ratios (6.56) were observed in the samples collected from the air masses originating from the north land source, indicating that OC mainly comes from anthropogenic sources. The OC concentrations in the air mass samples from marine sources were only 50% of those in the samples from terrestrial sources. A negative correlation between the WSOC and transport distance over the sea and decreased OC/EC ratios were observed, which indicated that the contribution of secondary organic carbon (SOC) to OC decreased during the transport from land to sea. OC increased by 88.5% under the influence of Asian dust, while WSOC did not exhibit substantial changes. The positive matrix factorization (PMF) model showed that anthropogenic sources were the major source of carbonaceous aerosols, contributing 70% of the OC in Qingdao. The positive correlation between OC and particulate matter (PM) suggested that the OC affected the air quality.