Qualitative and quantitative changes in traffic and waste incineration PCDD/Fs in urban air and soils under different seasonal conditions (Metropolitan Area of Barcelona)

Abstract

A sampling and analysis scheme was implemented to discriminate between inputs of polychlorodibenzo-p-dioxins and polychlorodibenzofurans (PCDD/Fs) at low concentrations in urban areas. Ambient air and soils were sampled and analyzed in five stations in the Metropolitan area of Barcelona (2018–2019); one located in a reference urban traffic site and four in the area of influence of an integrated waste management facility (IWMF) that included a solid waste incinerator. Seasonality was the main factor determining the PCDD/F composition, and involved lower values in the warmer months. This seasonal effect was related to enhanced photooxidation of PCDDs compared to PCDFs and faster depletion of the less chlorinated congeners due to volatility at higher ambient temperature; consistent with the compounds' octanol-air partition coefficients. The ratio 2,3,7,8-tetrachlorobenzofuran/1,2,3,4,6,7,8-heptachlorobenzofuran allowed, for the first time, identifying cases of preferential contributions of IWMF and traffic inputs, i.e. values of 0.06 and 0.32, respectively. Combination of this ratio with the airborne PCDD/F levels illustrated that the quantitative PCDD/F levels were not a useful criterion for elucidation between IWMF and traffic inputs.

PCDD/Fs levels in soils ranged between 9.0 and 22 pg WHO-TEQ/g in the two sites closest to the IWMF, while the other sites, including the traffic site, showed values between 0.8 and 1.9 pg WHO-TEQ/g. The levels in the former group were higher than those observed in other urban areas and above 5 pg WHO-TEQ/g, which is a limit reference value in several European countries. The C7 and C8 observed congener distributions in all soils examined were different from those in the air samples and similar to those reported in sewage sludge from waste water treatment plants, not showing influences from IWMF or traffic PCDD/F inputs.