Seasonal dynamics of barbecue-derived PAH accumulation in recreational Nature Park soils: evidence from Bolu Gölcük, Türkiye

Polycyclic aromatic hydrocarbons are persistent and carcinogenic contaminants that accumulate in soils, posing ecological and public health concerns in recreational environments. This study examines the concentrations, ring-based composition, spatial distribution, and seasonal dynamics of 16 U.S. EPA priority PAHs in surface soils of Gölcük Nature Park (Bolu, Türkiye), a heavily visited recreational area where outdoor barbecuing is widespread. A total of 42 soil samples were collected during summer and winter 2016, and PAH concentrations were quantified using a rigorously validated high-performance liquid chromatography (HPLC) method incorporating matrix-matched calibration and procedural blank correction. ΣPAH₁₆ spanned 108.3-2587.8 ng/g dry weight (dw) in summer and 111.8-3125.8 ng/g dw in winter, with higher winter levels reflecting cumulative atmospheric deposition following intense late-summer and early-autumn recreational activities. Molecular-weight- and ring-based assessments revealed the consistent dominance of high-molecular-weight PAHs, particularly 5-6 ring species, driven by their low volatility and strong sorption. Spatial interpolation maps generated in MapInfo (IDW) identified pronounced seasonal shifts in ΣPAH₁₆ and HMW PAH hotspots, especially in the eastern lakeside picnic-barbecue zone, whereas shaded forested areas exhibited distinct photo-oxidative attenuation patterns. According to the Maliszewska-Kordybach classification, up to one-third of winter samples corresponded to heavily contaminated soils. Benchmarking against a reference lake and international datasets indicates that PAH levels in this protected nature park exceed those of many urban green spaces and approach concentrations typical of industrial settings. Overall, the findings demonstrate that recreation-derived emissions substantially degrade soil quality and highlight the need for evidence-based management strategies to prevent long-term ecological deterioration in protected natural areas.