Origin of PCDDs in Ball Clay Assessed with Compound-Specific Chlorine Isotope Analysis and Radiocarbon Dating
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- 作者：Henry Holmstrand ; Damien Gadomski ; Manolis Mandalakis ; Mats Tysklind ; Robert Irvine ; Per Andersson ; and Ö ; rjan Gustafsson
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：June 15, 2006
- 年：2006
- 卷：40
- 期：12
- 页码：3730 - 3735
- 全文大小：119K
- 年卷期：v.40,no.12(June 15, 2006)
- ISSN：1520-5851
文摘
Polychlorinated dibenzo-p-dioxins (PCDDs) of highconcentrations in a ball clay deposit from the MississippiEmbayment were found to be consistent with a naturalabiotic and non-pyrogenic origin by investigation with bulkradiocarbon analysis, compound-specific chlorine isotopeanalysis (CSIA-
37Cl) of octachlorodibenzo-p-dioxin(OCDD), and black carbon (BC) analysis. The conventionalradiocarbon date of total organic carbon from a depthof approximately 10 m in three parallel cores ranged from14 700 years to >48 000 years, indicating that the stratawith elevated levels of PCDDs have remained isolated fromrecent anthropogenic input in these >40 Ma old claysediments. The CSIA-37Cl of OCDD yielded a 37Cl of -0.2”,which is significantly higher than the postulated rangefor biotic chlorination by chloroperoxidase enzymes, -11to -10”, and falls within the known range for abioticorganochlorines, -6 to +3”. The absence of correlationsbetween concentrations of PCDDs and correspondingpyrogenic black carbon (BC), together with estimations ofBC sorptive loadings and the absence of polychlorinateddibenzofurans (PCDFs), suggest that vegetation fires did notform these ball-clay PCDDs. Results from this studyindicate that the high levels of the toxic and carcinogenicPCDDs found in kaolinite-bearing clays may result fromnatural abiotic formation via in situ surface-promoted reactionson the clay mineral, including a so-far unknown organicprecursor, rather than being the result of anthropogeniccontamination.
37Cl) of octachlorodibenzo-p-dioxin(OCDD), and black carbon (BC) analysis. The conventionalradiocarbon date of total organic carbon from a depthof approximately 10 m in three parallel cores ranged from14 700 years to >48 000 years, indicating that the stratawith elevated levels of PCDDs have remained isolated fromrecent anthropogenic input in these >40 Ma old claysediments. The CSIA-37Cl of OCDD yielded a 37Cl of -0.2”,which is significantly higher than the postulated rangefor biotic chlorination by chloroperoxidase enzymes, -11to -10”, and falls within the known range for abioticorganochlorines, -6 to +3”. The absence of correlationsbetween concentrations of PCDDs and correspondingpyrogenic black carbon (BC), together with estimations ofBC sorptive loadings and the absence of polychlorinateddibenzofurans (PCDFs), suggest that vegetation fires did notform these ball-clay PCDDs. Results from this studyindicate that the high levels of the toxic and carcinogenicPCDDs found in kaolinite-bearing clays may result fromnatural abiotic formation via in situ surface-promoted reactionson the clay mineral, including a so-far unknown organicprecursor, rather than being the result of anthropogeniccontamination.