Levels And Distribution Characteristics Of Polybrominated Diphenyl Ethers In Pine Needles And Soils: A Case Study In Dalian

Polybrominated biphenyl ethers (PBDEs) are widely used in a variety of industrial products as an important additive of brominated flame retardants. PBDEs, as a group of global contaminants, have been ubiquitously detected in many environmental media, and their concentrations have been increasing with years. Some PBDEs have been listed as persistent organic pollutants (POPs).Soil is one of the major sinks for PBDEs. Plant leaves can accumulate PBDEs from environment effectively. Conifers, being evergreen species, can accumulate POPs for several years compared to broadleaf species because of their longer leaf turnover time. Pine (Cedrus deodar) needles and soils were collected in urban area in Dalian. PBDEs concentrations in pine needles and soils samples were determined from Dalian and PBDE profiles and distribution characteristics were investigated.Firstly, procedures and methods for PBDEs analysis in pine needles and soils were developed. Ultrasonic extraction were employed for extraction of PBDEs from soils and Soxhlet extraction for pine needles. Concentrated sulfuric acid was employed to cleanup samples and neutral alumina to fractionate PBDEs. The final extracts were identified and quantified by gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) with internal standard method in the selective ion monitoring (SIM) mode. Results showed methods were reliable with high recoveries and good reproducibility.It was shown that concentration of (?)PBDEs (excluding BDE-209) in soils from Dalian ranged from 0.187 to 5.339 ng/g dw, with geometric mean of 0.795 ng/g dw. Compared with other studies, level of PBDEs (excluding BDE-209) in soils from Dalian was moderate or low. Concentration of (?)PBDEs from park sites was comparable or lower than background soils from other regions. Soils from point source were less polluted with concentrations of (?)PBDEs fallen in the range of woodland soils from UK remote/rural regions. Concentration of (?)PBDEs in pine needles from Dalian ranged from 0.312 to 3.132 ng/g dw, with geometric mean of 0.986 ng/g dw. Concentrations ofî–¯(?)PBDEs in pine needles from park sites were relatively high comparing with soils. Since pine needles sequestered PBDEs mainly from the gas phase and soils received PBDEs mainly through dry and wet deposition of particles, it was proposed that atmospheric long-range transport of PBDEs was of major importance for pine needles to accumulate PBDEs compared to soils.In pine needles and soils from Dalian, BDE-47 and-99 made the highest contribution to (?)PBDEs (excluding BDE-209). Besides 8 PBDEs of primary interest (BDE-28,-47,-99,-100,-154,-153,-183,-209), BDE-116 was frequently detected in pine needles and soils from Dalian. BDE-66 was detected in most pine needles as well. Owing to respective characteristics of PBDE congeners and different accumulation ways for soils and pine needles, it's reasonable that higher contributions of low brominated PBDE congeners, i.e. BDE-28 and BDE-47, were observed in pine needles than those in soils. On the contrary, high brominated PBDE congeners, i. e. BDE-153 and BDE-183, made lower contributions in pine needles.Major PBDE congeners (excluding BDE-209) pattern turned out to be similar with 2 penta-PBDE technical flame-retardant mixtures. Therefore it was speculated that peata-PBDE technical flame-retardant mixtures were the major sources of BDE-47 and-99 in soils and pine needles. Similarly, BDE-183 was supposed to originate from octa-PBDE technical flame-retardant mixtures.