Atmospheric Concentrations and Sources of PCBs, PCNs, and PCDD/Fs near Ranches on a Steppe in North China

Abstract

Atmospheric concentrations and sources of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzo-p-dioxin/furans (PCDD/Fs) were investigated on a steppe in North China. The concentration ranges of trichlorinated to heptachlorinated biphenyls, trichlorinated to octachlorinated naphthalenes, and 17 PCDD/Fs in the ranch samples were 1498–2168, 454–803, and 8.76–18.2 fg/m3, respectively. Trichlorinated biphenyls, which were the main PCBs emitted from combustion processes and PCB commercial products, accounted for 67.4%–78.9% of the total PCBs. CN14/24, the indicator of coal and wood combustion, was the main contributor to the PCNs. Interestingly, CN61, which has been obviously detected in PCB commercial products in the past, was present in the ranch samples. Source apportionment conducted using the positive matrix factorization (PMF) model confirmed that wood and coal combustion was the dominant contributor to PCBs (71%) and PCNs (49%) in the ranch samples. Legacy capacitor impregnating agents and transformer oils in the steppe were a significant source of PCBs and PCNs. The PCDD/Fs were dominated by highly chlorinated homologs and mainly affected by combustion sources. Air mass back trajectories simulated showed that long-range transport was not the main source of the persistent organic pollutants (POPs) in the ranch atmosphere during the sampling period.