LAUSR

Abstract. Nitro-monoaromatic hydrocarbons (NMAHs), such as nitrocatechols, nitrophenols and nitrosalicylic acids, are important constituents of atmospheric particulate matter (PM) water-soluble organic carbon (WSOC) and humic-like substances (HULIS). Nitrated and oxygenated derivatives of polycyclic aromatic hydrocarbons (NPAHs and OPAHs) are toxic and ubiquitous in the ambient air; due to their light absorption properties, together with NMAHs, they are part of aerosol brown carbon (BrC). We investigated the winter concentrations of these substance classes in size-resolved PM from two urban sites in central and southern Europe, i.e. Mainz (MZ), Germany, and Thessaloniki (TK), Greece. The total concentration of 11 NMAHs ( ∑11 NMAH concentrations) measured in PM 10 and total PM were 0.51–8.38 and 12.1–72.1 ng m −3 at the MZ and TK sites, respectively, whereas ∑7 OPAHs were 47–1636 and 858–4306 pg m −3 , and ∑8 NPAHs were ≤90 and 76–578 pg m −3 , respectively. NMAHs contributed 0.4 % and 1.8 % to the HULIS mass at MZ and TK, respectively. The mass size distributions of the individual substances generally peaked in the smallest or second smallest size fraction i.e. or 0.49–0.95  µ m. The mass median diameter (MMD) of NMAHs was 0.10 and 0.27  µ m at MZ and TK, respectively, while the MMDs of NPAHs and OPAHs were both 0.06  µ m at MZ and 0.12 and 0.10  µ m at TK. Correlation analysis between NMAHs, NPAHs, and OPAHs from one side and WSOC, HULIS, sulfate, and potassium from the other suggested that fresh biomass burning (BB) and fossil fuel combustion emissions dominated at the TK site, while aged air masses were predominant at the MZ site.