PM2.5-bound polyhalogenated carbazoles (PHCZs) in urban Beijing, China: Occurrence and the source implication

Polyhalogenated carbazoles (PHCZs) are recently raising much attention due to their toxicity and ubiquitous environmental distribution. However, little knowledge is known about their ambient occurrences and the potential source. In this study, we developed an analytical method based on GC-MS/MS to simultaneously determine 11 PHCZs in PM_2.5 from urban Beijing, China. The optimized method provided low method limit of quantifications (MLOQs, 1.45-7.39 fg/m³) and satisfied recoveries (73.4%-109.5%). This method was applied to analyze the PHCZs in the outdoor PM_2.5 (n = 46) and fly ash (n = 6) collected from 3 kinds of surrounding incinerator plants (steel plant, medical waste incinerator and domestic waste incinerator). The levels of ∑₁₁PHCZs in PM_2.5 ranged from 0.117 to 5.54 pg/m³ (median 1.18 pg/m³). 3-chloro-9H-carbazole (3-CCZ), 3-bromo-9H-carbazole (3-BCZ), and 3,6-dichloro-9H-carbazole (36-CCZ) were the dominant compounds, accounting for 93%. 3-CCZ and 3-BCZ were significantly higher in winter due to the high PM_2.5 concentration, while 36-CCZ was higher in spring, which may be related to the resuspending of surface soil. Furthermore, the levels of ∑₁₁PHCZs in fly ash ranged from 338 to 6101 pg/g. 3-CCZ, 3-BCZ and 36-CCZ accounted for 86.0%. The congener profiles of PHCZs between fly ash and PM_2.5 were highly similar, indicating that combustion process could be an important source of ambient PHCZs. To the best of our knowledge, this is the first research providing the occurrences of PHCZs in outdoor PM_2.5.

Contamination characteristics of polychlorinated naphthalenes in the agricultural soil of two industrial cities in South Korea

This study investigates the contamination characteristics of polychlorinated naphthalenes (PCNs) in the rice paddy soils of two industrial cities (Pohang and Ulsan) in South Korea. The paddy soils were collected from 40 sites in the paddy fields near industrial complexes in both cities. The mean concentration of Σ₅₅ PCNs was 145.9 ± 101.7 pg/g and 95.4 ± 41.4 pg/g for the soils in Pohang and Ulsan, respectively. The toxic equivalents (TEQs) of Σ₂₈ PCNs ranged from 0.007 pg-TEQ/g to 0.069 pg-TEQ/g in Pohang, and 0.015 pg-TEQ/g to 0.046 pg-TEQ/g in Ulsan. The PCN profiles were dominated by lower chlorinated homologues such as tetra- and tri-CNs for both cities, which are associated with the historical use of technical products, or more specifically, Halowaxes (HW 1099, 1031, 1013, and 1001). The results of the principal component analysis (PCA) indicate that the historical residues from the technical products contributed to the PCN contamination, but the influence of combustion sources was also observed with a high fraction of combustion-related congeners. Based on this study, we can expect that rice grown in these paddy fields will accumulate PCNs and other combustion-related pollutants, strongly suggesting the necessity for multimedia (e.g., air, soil, water, and rice) monitoring and human exposure assessments of PCNs.