Distribution of organic pollutants in water and sediment : an international comparison

• Main Author: Wei, Si (韋斯)
• Format: Thesis
• Language: unknown
• Published: City University of Hong Kong 2008
• Subjects: Organic water pollutants; Contaminated sediments; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/2031/5404; http://lib.cityu.edu.hk/record=b2339790

Increased awareness of the global distribution of organic pollutants in the environment was the starting point for this study. This major objectives of this research were to modify existing methods and/or develop new methods and apply these methods to determine the concentrations of organic pollutants in different environmental matrices, including water and sediment, collected from various locations around the world and make comparisons between different regions. Recent studies have indicated the occurrence of a wide range of trace organic contaminants, including polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the Hong Kong environment. These contaminants are potentially harmful to ecological systems, particularly in coastal areas. However, there is little information on the historical trends of these pollutants in Hong Kong. In this study, DDTs (p,p’-DDT, o,p’-DDT, p,p’-DDD, o,p’-DDD , p,p’-DDE and o,p’-DDE), HCHs (α, β, γ and δ), HCB, heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin, kepone and chlordanes (α and γ) and PCB were analyzed in two sediment cores from Hong Kong. DDTs (p,p’-DDT, o,p’-DDT, p,p’-DDD, o,p’-DDD and p,p’-DDE), HCHs (α and γ), HCB, and PCBs were detected in both cores, whereas other pollutants were all below detection limits. Many OCPs have not been produced or used for many years due to toxicological or environmental concerns and the use of PCBs is prohibited in Hong Kong. However, some compounds were still found to be widely distributed in the environment in recent years, likely because of pollutant inputs from the highly industrialized Pearl River Delta region. These results provide important information on current and historical contamination in Hong Kong, and help to reconstruct the pollution history of these trace organic pollutants in Hong Kong coastal waters. Apart from the traditional organic pollutants, perfluorinated compounds (PFCs) are known to be important emerging global contaminants of concern. They are persistent and widely distributed in the environment. A total of fourteen PFCs were quantified in surface seawater samples collected between Asia and Antarctica. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were the two dominant compounds, with mean concentrations ranging from <5 to 72 pg/L and <5 to 442 pg/L, respectively. The greatest concentrations of PFOS and PFOA were measured in water samples from two locations near Shanghai, a major industrial urban center in China. In contrast, the concentrations of these compounds in water samples from the open ocean were very low. Different ratios of perfluorosulfonates (PFSAs) and perfluorocarboxylates (PFCAs) were observed in different locations indicating that the sources of PFCs in these regions are different. Although there have been many reports about PFCs such as PFOS in biota, little attention has been paid to the presence of these compounds in sediment because of their occurrence at low concentrations and the difficulty of analysis. As a result, the ultimate environmental fate and cycling of this emerging class of chemical contaminants are not known. In particular, very little is known about the sorption potential of these chemicals to environmental solids. The need for analytical methods to determine PFCs in relevant environmental matrices such as sediments is of great importance in order to understand their occurrence, behaviour, and impact in the environment. In this project, a new method for the extraction and measurement of individual PFCs in sediment samples at pg/g levels using high performance liquid chromatography / tandem mass spectrometry (HPLC-MS/MS) was developed. Liquid solvent extraction methods followed by an Envi-Carb and solid-phase extraction (SPE) clean-up step coupled with HPLC-MS/MS instrumental analysis were optimized for the determination of PFC concentrations in sediment. The Envi-Carb clean-up and modified SPE procedures removed matrix components sufficiently and minimized the co-extraction of compounds that might cause interference in the instrumental analysis. The LOQs of all of the analysed PFCs were 2-10 pg/g, and the recoveries of most PFCs (78%-116%) were acceptable and consistently and reproducibly quantitative. The newly developed method was applied to the analysis of sediment samples collected from three Asian areas—Hong Kong, mainland China and Japan—and the USA and Poland. PFOS, perfluoroundecanoic acid (PFUnDA), PFOA and 2-(N-ethyl perfluorooctane sulfonamido) acetate (N-EtFOSAA) were the most frequently detected and predominant chemicals in the samples with concentrations ranging from 6.1 - 3160 pg/g wet wt, from 6.6 - 693 pg/g wet wt, from 6.8 - 516 pg/g wet wt and from 13.0 - 3160 pg/g wet wt, respectively. Perfluorohexane sulfonate (PFHS), perfluorooctane sulfonamide (PFOSA), perfluorooctadecanoic acid (PFOcDA), perfluorohexadecanoic acid (PFHxDA), perfluorododecanoic acid (PFDoDA), perfluorodecanoic acid (PFDA), Perfluorononanoic acid (PFNA), perfluoroheptanoic acid (PFHpA), Perfluorohexanoic acid (PFHxA) and Perfluoropentanoic acid (PFPeA) were detected in the samples at lesser frequencies and at lower levels, while perfluorobutane sulfonate (PFBS), Perfluorotetradecanoic acid (PFTeDA) and 8:2 fluorotelomer unsaturated acid (8:2 FTUCA) were below LOQs in most of the samples and N-ethyl perfluorooctane sulfonamide (N-EtFOSA) and 8:2 Fluorotelomer acid (8:2 FTCA) were not detected in any of the samples. Relatively higher concentrations of PFCs were found in sediments from USA and Japan than in those from Hong Kong, China and Poland, possibly due to the diverse categories of industries and intensive use of PFC-related products in USA and Japan. Analysis of sediment cores from Hong Kong and Japan provided historical trend of PFCs in these regions. There were generally increasing trends of PFCs in the sediment cores in the past 50 years, which is coincident with the usage of PFC-related products in these regions. Data from this study suggest that PFCs occur widely in sediments at the low pg/g to ng/g level. Furthermore, substances that may be transformed to PFOS, such as N-EtFOSAA, are present in sediments at levels often comparable to PFOS. These results also indicate that some PFCs such as PFOS and N-EtFOSAA may strongly adsorb to solids, which may have important implications with regard to long-term retention and release of these chemicals to the environment. In a conclusion, this study provided information on the distribution pattern, current and historical contamination status of PCBs, OCPs and PFCs in different regions of the world. It is recommended that future studies should be carried out to identify the potential sources of these pollutants in the environment. CityU Call Number: TD427.O7 W45 2008 xvi, 144 leaves : ill. 30 cm. Thesis (Ph.D.)--City University of Hong Kong, 2008. Includes bibliographical references (leaves 119-139)