Desborough, Jennifer L. (2012)
Ph.D. thesis, University of Birmingham.
Chiral signatures were utilised as a means of determining the pathways of PCBs in the environment. Concentrations of HBCD diastereoisomers, enantiomers and degradation products were also determined in top soils from both the UK and Australia.
Concentrations of PCBs 28/31, 52, 101, 118, 138, 153, and 180 and enantiomer fractions (EFs) of PCB 95 and 136 were determined in air, top soil and grass from an urban site in
Birmingham, UK. Samples were taken approximately every 14 days at 5 graduating heights from the ground in summer 2009 (114 days) and spring 2010 (84 days). EFs of PCB 95 in air at 3cm height (average of 0.453 in 2009 and 0.468 in 2010), differed significantly (p<0.05) from the racemic EFs in air at 10, 40, 90, and 130 cm. The EFs of PCB 95 in soil were on average 0.452 in 2009 and 0.447 in 2010 and matched those in air at 3cm particularly in the 2009 campaign. Grass displayed an average EF of 0.468 (2009) and 0.484 (2010); values which were intermediate between those in soil and the racemic EFs in air measured at 10 cm and above. These data imply that at the study site, PCBs volatilise from soil to an extent discernible only at the soil:air interface, and that PCBs in grass arise due to foliar uptake of volatile emissions from soil. Atmospheric concentrations of PCBs increased significantly (p<0.05) with increasing height above the soil surface. This combined with the PCB 95 chiral signature data, suggests that the influence of PCB emissions from soil on airborne concentrations decreases with height while emissions from indoor air increases.
HBCD chiral signatures were found to be racemic or near-racemic in all the air, grass and soil samples from the same urban site in Birmingham, UK used for sampling PCBs. Soils from 24 ii sites across the UK were also found to contain near racemic chiral signatures of HBCDs. This indicates that enantioselective microbial degradation is not occurring and the sites were unsuitable for a study like that used for PCBs to determine pathways of HBCDs into plants using chiral signatures.
Concentrations of ΣHBCD from soils from the UK (n=24) were found to be 22 ng/g ranging between <0.03 to 420 ng/g. By comparison, the average concentration of ΣHBCD in soils
from Australia (n=17) was 0.74 ng/g ranging between <0.0005 to 5.6 ng/g. Degradation products of HBCD, pentabromocyclododecenes (PBCDs) and tetrabromocyclododecadienes (TBCDs) were also semi-quantitatively determined in the soil samples. In the UK soils, PBCDs and TBCDs were determined in 7 and 6 of the soil samples respectively with concentrations ranging from 10-7300 pg/g for ΣPBCDs and 10-1300 pg/g for ΣTBCDs. In the Australian soils only TBCD was detected in soil at concentrations ranging from 2.3 to 450 pg/g ΣTBCDs. A preliminary environmental budget found soil to be the principal sink for HBCD in the UK.
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