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Halogenated flame retardants (HFRs) are ubiquitous in the environment, but little information is available about the bioaccumulation of HFRs in mangrove plants. In this study, three mangrove plant species were collected from Futian National Nature Reserve of Shenzhen City, South China to investigate the bioaccumulation of polybrominated diphenyl ethers (PBDEs) and several alternative halogenated flame retardants (AHFRs), including decabromodiphenyl ethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), hexabromobenzene (HBB), pentabromotoluene (PBT), tetrabromop-xylene (p TBX), pentabromoethylbenzene (PBEB) and dechlorane plus (DP). The mean concentrations of PBDEs, DBDPE, BTBPE, p TBX, PBT, PBEB, HBB and DP in mangrove plant species were 2010, 1870, 36.2, 18.7, 40.1, 17.8, 9.68 and 120 pg g−1 dry weight, respectively. PBDEs were the dominant HFRs in mangrove plant tissues, followed by DBDPE. The relative abundance of BDE 209 in three mangrove plant tissues were much lower than those in sediments. Significant negative relationships between log root bioaccumulation factors and log K ow , and between log TF r-s (from root to stem) and log K ow were observed, indicating that HFRs with low hydrophobicity were easily absorbed by mangrove roots and stems. A positive correlation between log TF s-l (from stem to leaf) and log K ow were found, suggesting that air-leaf exchange may occur in mangrove plants. This study highlights the uptake of HFRs by mangrove plants, which can be used as remediation for HFRs contamination in the environment. Image 1 • PBDEs and AHFRs were determined in natural mangrove sediments and plants. • PBDEs were the dominant HFRs in mangrove plant tissues, followed by DBDPE. • The root accumulation factor was regulated by log K ow of PBDEs and AHFRs. • Translocation of PBDEs and AHFRs from root to stem positively correlated with log K ow. • Mangroves are playing important roles in retaining PBDEs and AHFRs. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCDD) and dechlorane plus (DP) were measured in sediments collected from three mangrove wetlands of the Pearl River Estuary (PRE) in South China. This study aims to investigate the distribution of these halogenated flame retardants (HFRs) and the correlations between HFRs and microbial community structure in mangrove sediments. Concentrations of PBDEs, DBDPE, BTBPE, TBBPA, HBCDD and DP in mangrove sediments ranged from 6.97 to 216.1, 3.70–26.0, 0.02–0.73, 0.02–37.5, 0.44–127.5 and 0.07–2.23 ng/g dry weight, respectively. Higher levels of PBDEs, BTBPE, HBCDD and DP were observed in sediments from Futian mangrove wetland of Shenzhen, the only nature reserve located in the downtown of China. The highest concentration of TBBPA found in mangrove sediments from Guangzhou was proximate to a ferry terminal and a dockyard where TBBPA is widely used in the coatings. PBDEs were the predominant HFRs in mangrove sediments, with an average contribution of 63.0%. Mangrove sediments from Guangzhou and Zhuhai showed an enrichment of (−)- α -HBCDD, (−)- β -HBCDD and (−)- γ -HBCDD. Concentrations of HFRs in mangrove sediments from Guangzhou increased significantly from 2012 to 2015, which was probably due to the establishment and rapid development of Nansha Free Trade Zone of Guangzhou. Redundancy analysis showed that HFRs may cause a shift of microbial community structure in mangrove sediments and the variations were significantly correlated with TBBPA, syn -DP and BTBPE. Image 1 • HFRs and microbial community structure were determined in mangrove sediments. • Mangrove sediments from Shenzhen had higher levels of PBDEs, BTBPE, HBCDD and DP. • HFRs levels in Guangzhou mangrove sediments increased from 2012 to 2015. • Three mangrove wetlands had distinct distribution patterns of non-PBDE HFRs. • HFRs in mangrove sediments had significant relationships with the PLFA profiles. [ABSTRACT FROM AUTHOR]