Bioaccumulation of Polyhalogenated Carbazoles and its Related Compounds from Soil to Plant: Impact Factors and Uptake Pathways

Little is known about the contamination and bioaccumulation of polyhalogenated carbazoles (PHCZs) in plants. This study investigated the concentrations and distributions of 11 PHCZs and two related compounds, carbazole (CZ) and benzocarbazole (BZCZ), in soil and herbs from Hangzhou. The concentrations of ∑11PHCZs, CZ, and BZCZ in herbs were 1.9–247.1 ng/g dry weight (dw), 0.05) and cos θ (0.706–0.998) indicated a lack of species-specific distribution of PHCZs. The mean bioconcentration factors (BCFs) for CZ, BZCZ, and PHCZs were 0.21, 3.62, and 0.08–10.52, respectively. 2,3,6,7-tetrachlorocarbazole, 2,7-dibromocarbazole, and 1,3,6,8-tetrabromocarbazole are bioavailable in herbs, whereas CZ and 3-bromocarbazole are not. The negative correlations between the BCFs and soil concentration provide evidence of the kinetic limitation of accumulation at higher levels of exposure. The correlation analysis indicated the potential influences of KOA and KOW on the transfer of PHCZs from soil to plants. The mass balance model suggests a predominance of the soil-root-leaf pathway compared to the soil-air-leaf pathway. KAW appeared to be a more important parameter to evaluate the accumulation in leaves than KOA. PHCZs with log KOW > 5 and log KAW close or < −6 would be hard to enter the plant via soil-related pathways. The BCFmodeling/BCFmonitoring ranged from 1.8 × 10-5 to 0.52, suggesting the existence of extra pathways, such as direct dry and wet deposition from the background air.