Chemical properties, sources and size-resolved hygroscopicity of submicron black-carbon-containing aerosols in urban Shanghai

Abstract. Refractory black carbon (rBC) aerosols play an important role in air quality and climate change, yet highly time-resolved detailed investigations on the physicochemical properties of rBC its associated coating are still scarce. In this work, we used a laser-only Aerodyne soot particle aerosol mass spectrometer (SP-AMS) to exclusively measure rBC-containing (rBCc) particles, compared their with those total nonrefractory submicron particles (NR-PM1) measured parallel by high-resolution AMS (HR-AMS) Shanghai. Observations showed that, overall, was thickly coated, average ratio core (RBC) ∼5.0 (±1.7). However, rBC-coating species NR-PM1 only 19.1 (±4.9) %; sulfate tended condense preferentially non-rBC so 7.4 (±2.2) %, while majority (72.7±21.0 %) primary organic (POA) were rBC. Positive matrix factorization revealed that organics emitted from cooking did not coat rBC, portion coated biomass burning; such unidentifiable NR-PM1. Small rBCc predominantly traffic, large-sized ones often mixed secondary components typically had thick coating. Sulfate (SOA) generated mainly through daytime photochemical oxidation (SOA formation, likely situ chemical conversion traffic-related POA SOA), nocturnal heterogeneous formation dominant for nitrate; also estimated time 5–19 h During short period affected ship emissions, characterized as having high vanadium concentration (on 6.3±3.1 ng m−3) mean vanadium/nickel 2.0 (±0.6). Furthermore, size-resolved hygroscopicity parameter (κrBCc) obtained based full characterization, parameterized κrBCc(x)=0.29–0.14 × exp⁡(-0.006×x) (where x ranges 150 1000 nm). Under critical supersaturations (SSC) 0.1 % 0.2 D50 values 166 (±16) 110 (±5) nm, respectively, 16 (±3) 59 (±4) number could be activated into cloud condensation nuclei (CCN). Our findings valuable advancing understanding BC chemistry well effective control atmospheric pollution.