Measurement report: Seasonal trends and chemical speciation of chromium(III/VI) in different fractions of urban particulate matter – a case study of Radom, Poland

The paper assesses chromium occurrence in urban particulate matter – PM10, PM2.5, PM1, and PM0.25 – over a calendar year. The seasonality of both pseudo-total chromium content and its valence speciation are studied. Airborne aerosol was sampled in the city of Radom (Poland) using a Hi-Flow MOUDI model 130 cascade impactor from Copley. Crtot concentrations in the PM fractions investigated ranged from 0.08 to 4.09 ng m−3. The results point to a seasonality of Crtot concentration changes in PM. The concentration of Crtot in PM10 was maximum in winter (2.23 ± 0.53 ng m−3 on average) and averaged 1.71 ± 0.83 ng m−3 in the whole measurement period. The average Cr(VI) concentration did not exceed 0.40 ng m−3 and was maximum in winter, too (max 1.354 ng m−3). The Cr(VI) share in PM in the particular seasons varied from a low in summer (9.1 % of Crtot) to a high in winter (40 % of Crtot). The carcinogenic risk for the urban residents based on the Cr(VI) concentration in PM10 was below the US Environmental Protection Agency (EPA) threshold for significant risk (between 1 × 10−6 and 1 × 10−4) and amounted to between 1.11 × 10−6 and 5.78 × 10−6 for children and from 3.69 × 10−6 to 1.92 × 10−5 for adults. The non-carcinogenic health risk caused by the presence of Crtot was also lower than the safe level of 1 – the hazard quotient (HQ) values for both adults and children ranged from 1.32 × 10−2 to 3.92 × 10−2. The studies presented in the paper fill the research gap of Crtot and Cr(VI) measurements in particulate matter of different sizes in the air of a medium-sized city in central Poland.