Concentrations of atmospheric black carbon and organic carbon. Seasonal variations of atmospheric BC (left panel) and atmospheric OC concentrations (right panel). The BC concentrations were measured both from PM₁₀ collected in Haiphong City using the CTO method (plain box) and from real-time measurements in Halong Bay using the aethalometer (hatched box). Box-and-whisker plots showing median (straight line) and average (dashed line) concentrations. Note different scales for the y-axes. DOI: https://doi.org/10.1525/elementa.255.f5