The global mass balance for chlorinated dioxins and dibenzofurans

• Main Author: Brzuzy, Louis P
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1995
• Subjects: Automotive engineering; Automotive materials; Civil engineering; Environmental science; Sanitation
• ISBN: 9798207836355

Chlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) are well-known, highly toxic, environmental pollutants that enter the atmosphere as by-products from combustion processes. In spite of our knowledge about the environmental behavior of PCDD/F, their mass balance in the atmosphere is unacceptable. It seems that 20 times more PCDD/F leave the atmosphere than enter it. There are two explanations for this mass balance discrepancy: (a) Atmospheric deposition is overestimated due to sampling bias. (b) The input estimates are low because of unrecognized sources. Because most PCDD/F measurements have been conducted in areas of significant human activity, deposition may be overestimated. To overcome this bias, a global PCDD/F mass balance was developed. To obtain a database of PCDD/F worldwide deposition measurements, a new technique using soils was developed. Studies of four soil cores showed that 80% of the PCDD/F load was contained in the top 15 cm of the core. Soils and lake sediments were collected in similar geographic regions, and the soil-derived and lake sediment-derived PCDD/F fluxes were compared. The relative standard deviation of four soil-lake sediment pairs ranged from $\pm$3% to $\pm$26%. Comparison of homologue profiles also showed good agreement. Analysis of field duplicate soil samples gave relative standard deviations ranging from $\pm$2% to $\pm$59%. The results of this study demonstrated that soils can be used to estimate the deposition of PCDD/F from the atmosphere. PCDD/F were then measured in 107 soil samples globally. Deposition to land surfaces was estimated by dividing the earth into five depositional zones based on climatic and geographical factors. Total global deposition from the atmosphere to land was estimated to be 12,500 $\pm$ 1,300 kg/yr. Based on limited data, deposition to the oceans was estimated to be only about 600 $\pm$ 1,500 kg/yr, yielding a total global deposition of 13,100 $\pm$ 2,000 kg/yr from the atmosphere. Emissions of PCDD/F to the global atmosphere were estimated from the literature. The major sources considered in this study were municipal waste incineration, biomass combustion, steel and copper mill emissions, cement kiln emissions, medical waste incineration, and emissions from automobiles. Total annual emissions were estimated to be about 3,000 $\pm$ 600 kg. Global deposition (see above) is roughly 4 times greater than annual emissions. This suggests that the sources of PCDD/F are not well characterized and more data is needed on emission factors and production rates of PCDD/F to the global atmosphere.