Source appointment of PM_2.5 in Qingdao Port, East of China

Field measurements were conducted near Qingdao Port to characterize the particulate air pollutants, assess the spatial and seasonal characteristics of the pollutants, and identify the contribution from ship traffic emissions. By utilizing multiple statistical methods and data collected at two sites in Qingdao, we comprehensively explored the PM_2.5 seasonal characteristics and source apportionments of different PM_2.5 constituents, especially those originating from ship emissions, and identified potential source regions for samples collected in Qingdao. In this study, 118 concurrent daily PM_2.5 samples were collected from August 2018 to May 2019 at a port site (QH) and a coastal background site (BG). Vanadium (V) and Nickel (Ni) are the dominant metal elements from crude oil and crude oil combustion emissions. The significant correlations between V and Ni at both sampling sites, indicating that shipping emissions have a significant impact on the port and background area. Additionally, Ni and other metals showed significant correlations at the BG site, implying Ni also emission from the land-based oil at this site. The positive matrix factorization (PMF) model identified six main sources for the PM_2.5 samples in Qingdao, and they are coal combustion, industrial emissions/mineral dust, marine vessel emissions, secondary aerosols/biomass burning, sea salt/crustal emissions, and vehicle exhaust, respectively. Marine vessel emissions were the dominant contributor to PM_2.5 in Qingdao during the sampling periods (25.05%). The potential source contribution function (PSCF) analysis suggested that the Yellow Sea and Jiaodong Peninsula were the major sources regions for PM_2.5 in Qingdao. The Yellow Sea and Bohai Sea were the potential source regions for shipping emissions in Qingdao. Therefore, efforts to control shipping emissions should be strengthened not only at the Qingdao Port but also in surrounding ports.