Pine biomonitoring of PCDD/Fs: Seasonal dynamics, air-plant partitioning, and source apportionment

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are Stockholm Convention-listed persistent organic pollutants (POPs) known for their environmental persistence and toxicity. Due to their high lipid content, tree components are highly effective passive samplers for PCDD/F monitoring. Because no prior research has investigated PCDD/F levels in tree components in Türkiye, this study addresses this crucial knowledge gap. Accordingly, pine needle and branch samples were collected monthly for 1 year from an urban area of Bursa. Mean total PCDD/F concentrations for needles and branches were 15.6±5.62 pg/g dw (1.7±0.39 pg WHO-TEQ/g) and 19.6±3.77 pg/g dw (1.7±0.5 pg WHO-TEQ/g), respectively. These values align with concentration levels reported globally. Needle and branch sample levels negatively correlated with ambient temperature. Source apportionment analysis of needles and branches indicated vehicular emissions as the region's primary source of pollution. To model transfers between tree components and the atmosphere, ambient air sampling occurred alongside needle and branch collection. Ambient air concentrations (C_A) estimated via needle and branch models correlated significantly with measured atmospheric concentrations (r²=0.52 and r²=0.57, respectively) (p < 0.05). Model results indicated that low-chlorinated PCDD/F congeners tend to volatilize from tree components to air (C_A^∗/C_A = 3.42±2.22 and 2.97±1.56 for needles and branches, respectively), while high-chlorinated congeners predominantly deposit from air to tree components (C_A^∗/C_A = 0.31±0.3 and 0.93±0.62 for needles and branches, respectively).