Occurrence and seasonal distribution of persistent organic pollutants in air and soil across agricultural urban and industrial landscapes

Soil represents a major terrestrial reservoir of persistent organic pollutants (POPs) that influence their atmospheric concentrations through volatilization processes. This study examines the distribution, seasonal variability, and air–soil exchange of key organochlorine pesticides (OCPs) (i.e., ΣDDTs, ΣHCHs), and polychlorinated biphenyls (PCBs) in soils and air from industrial, agricultural, and urban areas in three Khyber Pakhtunkhwa cities (Peshawar, Swabi, Haripur), Pakistan. Results showed that measured OCPs concentrations in air were highest in agricultural sites (ΣDDTs: 0.02–21.7 ng m⁻ 3 ; ΣHCHs: 0.24–2.50 ng m⁻ 3 ), followed by urban sites (ΣDDTs: 0.23–29.8 ng m⁻ 3 , ΣHCHs: 0.10–2.29 ng m⁻ 3 ), and industrial sites (ΣDDTs: 80.13-16.1 ng m⁻ 3 , ΣHCHs 0.38-6.22 ng m⁻ 3 ), respectively. Sum of PCBs in air followed the same trend in concentration (0.03–2.46 ng m⁻ 3 ), (0.37–2.29 ng m⁻ 3 ), and (0.02-1.77 ng m⁻ 3 ) for urban, agriculture and industrial sites, respectively. Soil levels peaked in agricultural areas (ΣDDTs: 2.8-3488 pg/g; ΣHCHs: 2.5-826 pg/g; PCBs: 8-841 pg/g), then industrial (2.5-545, 3-348, 1.5-309 pg/g) and urban (3.6-80.3, 1.1-658, 2.7-249 pg/g). Historical and ongoing use of organochlorine pesticides (OCPs) has led to high contamination, primarily from manufacturing of technical DDT and agricultural runoff. Atmospheric POPs composition showed the trend in decreasing order of Peshawar > Swabi > Haripur, while in selected zone; agricultural > urban > industrial. Elevated levels of DDTs, HCHs, and PCBs were observed in both air and soil during warmer seasons (pre-monsoon and monsoon periods), likely indicating active sources such as legacy pesticide residues, combustion processes, or volatilization from contaminated surfaces. Fugacity calculations comparing monsoon and non-monsoon periods reveal that soils in certain areas act as secondary emission sources, remobilizing POPs into the atmosphere. These findings suggest the need for routine POPs monitoring, air-soil exchange studies, and mitigation of human activities to minimize and environmental impacts in Pakistan.