Source identification of carbohydrates and polycyclic aromatic hydrocarbons in a rural area near the Plitvice Lakes National Park, Croatia

Abstract

This study examines the levels and seasonal changes of organic compounds in terms of carbohydrates and polycyclic aromatic hydrocarbons (PAHs) in PM₁₀ collected at a rural site near the Plitvice Lake National Park (Croatia) to determine their source in airborne particles. Mass concentrations of PM₁₀ particles were higher during the summer compared to the winter season (14 ± 5.3 μg m⁻³ and 6 ± 3.4 μg m⁻³, respectively). Such seasonal variation is unusual for this part of Europe, where the winters are harsh and biomass for domestic heating is most common. The analysis of carbohydrates in PM₁₀ revealed the presence of anhydrosugars, sugar alcohols, and monosaccharides throughout the sampling period. Anhydrosugars were the most dominant compounds despite the season. The highest average mass concentrations of 124.1 ± 100.06 ng m⁻³, 8.0 ± 5.55 ng m⁻³, and 7.0 ± 7.62 ng m⁻³ for levoglucosan (LG), mannosan (MNS), and galactosan (GA), respectively, were reached in the winter season. Sugar alcohols were most pronounced during the summer, while the levels of monosaccharides contributed evenly through autumn and summer. The levels of PAHs were higher during winter and lowest during the summer season. Their concentrations in PM₁₀ were at least one order of magnitude smaller compared to carbohydrate concentrations. The highest average mass concentration was observed for benzo(b)fluoranthene (BbF) in spring (0.126 ± 0.068 ng m⁻³), pyrene (Pyr) in summer (0.038 ± 0.013 ng m⁻³), benzo(ghi)perylene (BghiP) in autumn (0.153 ± 0.107 ng m⁻³) and BbF in winter (0.283 ± 0.259 ng m⁻³). The annual average mass concentration of BaP was 0.086 ± 0.1028 ng m⁻³, which is lower than the European Union (EU) directive target value of 1 ng m⁻³. To determine the sources of organic compounds in airborne particles, different multi-statistical techniques were used; Spearman correlation, factor analysis, principal Component Analysis (PCA), as well as diagnostic ratio method, revealing the seasonal dynamics of various sources. The reason for these changes can be found in different human and nature activities in the rural background area. Data analyses indicated that in the spring season, there were mixed sources, including traffic, emissions from domestic heating or the combustion of grass/agricultural waste, and biogenic aerosols. In the summer, the dominant sources were biogenic emissions related to fungi spores and degraded material, biomass burning, and traffic. Vehicular emissions and biogenic sources were likely dominant at Plitvice Lakes during autumn, whereas domestic heating was the dominant source in the studied area during winter.