Historical trends in halogenated flame retardants in dated sediment from a semi-enclosed bay of Korea

Abstract

Polybrominated diphenyl ethers (PBDEs) are one of the most widely known and used as flame retardants (FRs). Due to the toxicity and persistence of PBDEs, PBDEs have been regulated in many countries. Under the regulations of PBDEs, novel brominated flame retardants (NBFRs) and dechlorane plus (DP) are being produced and used as replacements for PBDEs. Three sediment cores were collected from a semi-enclosed bay (Masan Bay) of Korea, to examine historical trends in halogenated FRs including PBDEs and their alternatives. Total 22 PBDEs, eight NBFRs and four DP were measured using a gas chromatography coupled with a triple quadrupole tandem mass spectrometer (GC/MS/MS) under the multiple reaction monitoring mode. PBDEs, NBFRs, and DP were detectable in all of the dated sediments, implying ubiquitous contaminants in coastal environment of Korea. The concentrations of PBDEs, NBFRs, and DP in all dated sediment samples ranged from 0.01 to 46.5 (mean: 5.62) ng/g dry weight, 0.01 to 3.56 (mean: 0.37) ng/g dry weight, and 0.01 to 1.08 (mean: 0.13) dry weight, respectively. Among HFRs, BDE 209, DBDPE, and BTBPE were predominant in all sediment samples, suggesting that 1,2-bis(pentabromophenyl)ethane (DBDPE) and 1,2-bis(2,4,6- tribromophenoxy) ethane (BTBPE) were preferentially replaced into regulated brominated FRs such as PBDEs. The highest concentrations of HFRs for sediments were found at the location close to the outfall of a wastewater treatment plant (WWTP), suggesting a potential contamination source of FRs in coastal environment. Historical trends in PBDE concentrations showed a clear increase since 1980s and the highest peak in 1990s, and then decreased with increasing time. This was consistent with domestic and global consumption patterns of PBDEs. Similar trends in PBDEs were found for BTBPE and DP, suggesting contemporary consumption for these FRs. However, the concentrations of DBDPE gradually increased since 2000s and then slightly decreased to the present, implying consumption of DBDPE as alternatives for regulated FRs. Gradual increase in the ratio of DBDPE/BDE 209 over time indicates the effectiveness of regulation on PBDEs in Korea. Historical trends in HFRs in dated sediments were well coincided with the consumption patterns and time-series of regulation in domestic and global scales. Our findings support that retrospective study using sediment core samples is a good tool to understand historical trends in halogenated toxic substances associated with regulatory actions in terrestrial and marine ecosystems.