PM2.5 source profiles and relative heavy metal risk of ship emissions: Source samples from diverse ships, engines, and navigation processes

PM2.5 (particulate matter) samples from ship emissions were collected using the portable dilution tunnel sampler in a Chinese port city. A fishing boat, three navigation processes (departing, cruising and arriving) of a roll-on/roll-off (ro-ro) passenger ship and a freighter vessel were tested for seven source profiles during on-board sampling campaigns. The chemical composition properties of profiles were obtained based on carbonaceous material (organic carbon and element carbon), elements and water-soluble ions (NH4+, NO3- and SO42-). Unique characteristic of each source profile was evaluated by COD and RMSD values. The results showed that PM2.5 from ships shared similar signatures in which OC (30.4%-46.1%), EC (6.6%-24.0%) and SO42- (1.1%-5.9%) comprised a large amount. Heavy metals such as Ni and V can be regarded as trace markers for heavy fuel oil burning in the ship emissions. COD and RMSD values between each pair of profiles revealed differences of source profiles. The fishing boat (FH) source had prominent differences from the rest source profiles, besides, the freighter sources were similar with the ferry main engine (FME) source. For navigation processes, it was found that arriving process can be clearly distinguished from the other two processes. Analyses of relative non-cancer and cancer risks of PM-bound heavy metals indicated that Cr heavily contributed to both non-cancer risk and cancer risk of heavy metals (above 75%) for fishing boats and freighters. The Cr, Co and Ni played important roles in risk of FME. The relative risk influences of Co increased and those of Cr decreased from departure to arrival of FME. Besides, the As showed more serious cancer risk in FAE and FMEA.