The chlorinated flame-retardant Dechlorane Plus (DP; C18H12Cl12), which is used as a substitute for Dechlorane (also called Mirex), is widely used in hard plastic electrical connectors in televisions and computer monitors, wire coatings, and furniture. It has been found to have similar properties to persistent organic pollutants (POPs), and these properties include its bioaccumulation potential, its persistence in the environment, and its potential for long-range transport to remote regions.

Locations of soil, sediment and passive air sampling sites are shown. Credit: ©Science China Press

Scientists from Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences collected air samples, soil samples, and surface sediment samples in the vicinity of a DP production facility in East China to assess the concentrations and spatial distribution of DP. The sample were analyzed using a gas chromatography-mass spectrometry instrument (2010 Ultra; Shimadzu, Kyoto, Japan) with an electron capture negative ionization ion source.

The concentrations of the two DP isomers and of the total DP (the syn-DP plus the anti-DP concentrations) in the active air samples ranged from 5.52 to 3,332 pg/m3. DP was detected in both the particle phase and the gas phase fractions of the samples, but more than 95 % of the DP was found in the particle phase.

The highest DP concentration in passive air (3,332 pg/m3) was found inside the DP plant. High DP were detected at four other sites around the plant. The lowest concentration (5.52 pg/m3) was found at site P2, which was some distance from the plant. The level in winter was a little higher than that in the other seasons, and the spatial trends were similar to those in the active air samples.

All the soil samples contained detectable DP concentrations, with concentrations ranged from 0.50 to 2,315 ng/g dw. The highest DP concentration in soil (2,315 ng/g) was also inside the plant. This was in the same order of magnitude as the DP found at a sampling site close to the plant found by Wang et al.. The lowest DP concentration (0.497 ng/g dw) was found at site S4, which was 7.6 km from the plant.

The log KOW value for DP is rather high (9.3 for both the syn-DP and anti-DP stereoisomers), so both DP isomers could easily become sorbed by organic matter in environmental media and would eventually be partitioned between the organic matter and other phases in the environmental media. However, no correlation was found between the TOC contents of the soil samples and the DP concentrations in the samples. Besides the TOC content of soil, the land use, wet deposition, degradation of DP in the environment, and atmospheric transport of DP could all affect the DP distribution in soil and sediment. In addition, the source of DP emissions could clearly affect the distribution of contaminants in the area surrounding the source, and this could disturb the balance between the pollutant concentrations in the soil organic matter and the other soil components.

The total DP concentrations in the sediment samples ranged from 0.32 to 20.5 ng/g dw. The highest DP concentration in sediment was found near a drainage outlet from the DP plant. This indicates that wastewater from the DP plant might supply DP to the surrounding water bodies.The concentrations in several Chinese cities, and the North American Great Lakes are generally lower than the concentrations in this study. However, DP concentration from a reservoir close to an e-waste recycling plant in South China (7,590 ng/g) was much higher than that in our study.

The anti-DP fractional abundance (fanti) is generally used to assess the fate and distribution of DP in the environment. Commercial DP products contain about 65 % anti-DP and 35 % syn-DP, giving an fanti value of 0.65. The isomer ratio can vary substantially during production. Commercial DP products from the DP manufacturing plant in our study area were analyzed, and their fanti values were 0.68 ± 0.01.

The mean fanti values for the soil, sediment, and air samples that were analyzed are shown in Fig. 3. The fanti values in the passively collected air samples ranged between 0.57 and 0.71 (mean 0.64), which was slightly lower than that for the commercial product but similar to the fanti values found in ambient air collected in other urban and rural areas in China and at sites near Niagara Falls. Furthermore, the mean fanti values in the soil, sediment, and actively collected air samples were 0.67, 0.68, and 0.70, respectively, and these were similar to the fanti value for the commercial product. This suggests that both DP isomers are stable in the environment and that no obvious stereoselective process has occurred in the environment around the production plant.

This paper suggested that DP concentrations decreased as the distance of the sampling site from the plant increased, and anti-DP was the predominant isomer. The fanti value was close to that in the commercial products produced at the plant, indicating that the DP production activities release DP to the environment around the plant. The results provide further confirmation that DP can potentially be transported from a production facility to the surrounding environment. The results will be of use when assessing the environmental impacts of a DP manufacturing plant on its surrounding environment.

This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB14010100), ''One-Three-Five'' Strategic Planning of Chinese Academy of Sciences (YSW2013B01), and the National Natural Science Foundation of China (21321004, 21277165 and 21107122). (EurekAlert!)