Achiral and chiral analysis of polychlorinated biphenyls (PCBs) in the aquatic and riparian food webs in Twelve Mile Creek, South Carolina

• Main Author: Dang, Viet D
• Format: Dissertation
• Language: English
• Subjects: biology, ecology; engineering, environmental; environmental sciences
• ISBN: 0549159037; 9780549159032

Polychlorinated biphenyls (PCBs) contamination in the Twelve Mile Creek arm of Lake Hartwell, South Carolina, has been an issue for decades. Lake Hartwell, which is a reservoir located on the border between the states of South Carolina and Georgia, was contaminated with an estimated 440,000 pounds of PCBs. PCBs were released from the Sangamo-Weston capacitor plant located on Town Creek, which feeds into Twelve Mile Creek and ultimately Lake Hartwell. The Twelve Mile Creek tributary connecting the Sangamo-Weston plant to Lake Hartwell has had little attention. Understanding PCBs contamination in the aquatic and riparian food webs of Twelve Mile Creek has not been comprehensively investigated to date. With the dominant properties of this class of organochlorine compounds such as low solubility, and high lipophilicity, PCBs are considered resistant to degradation in the environment. Therefore, the goal of this thesis was to evaluate the pattern of the PCBs contribution to the aquatic and riparian food webs and biological processes governing transfer of PCBs through food webs in Twelve Mile Creek.
PCB analyses were conducted on sediments, aquatic and riparian organisms from Twelve Mile Creek, which were collected as part of a larger project by the US Environmental Protection Agency. Achiral PCBs analysis provided insight into total PCBs content of various trophic levels, and also on biomagnification of PCBs through the food webs. Chiral analysis of atropisomeric PCBs provided insight into biological discrimination between PCB congener enantiomers during uptake and biodegradation processes. Atropisomeric PCBs analysis is a useful tool to track the potential biotransformation activity of chiral PCB atropisomers in the environment.
The aquatic food web including sediments, clams, mayflies, and yellowfin shiner (fish), was sampled in Fall 2005 from four sites along Twelve Mile Creek. Riparian species including spiders (tetragnathidae, dolomedes , and garden spiders) and amphibians (frogs, salamanders, and lizards) were collected in Spring, Summer, and Fall 2005 along Twelve Mile Creek from four sites. Achiral PCBs analysis demonstrated that total PCB concentrations were characterized by species-dependent patterns in the aquatic food web. No site or time-dependent patterns were consistently observed for total PCB levels in the riparian species. This observation demonstrated that PCBs biotransformation in the riparian was more variable than in the aquatic species. The observation is preliminary since the number of riparian species investigated was limited. Tetra-, penta-, and hexa-chloro biphenyl groups were almost always found as the most predominant contribution in the aquatic and riparian species accounting for 70% to 80% of the total PCB concentrations. PCB congeners 118 (245-34), and 153 (245-245) were almost always found to be abundant, confirming their highly persistent nature. PCBs 118 and 153 are present in Aroclor 1254 by a weight percent of 10.49 and 3.77, respectively. Aroclor 1254 was one of Aroclors mixture, which was released into the Lake Hartwell from the Sagamo-Weston plant during its manufacturing processes.
Enantiomers of atropisomeric PCBs were quantified to investigate the hypothesis that selective PCB biotransformation occurs in the food webs of the Twelve Mile Creek. Eight selected PCB atropisomers, 84 (236-23), 91 (236-24), 95 (236-25), 132 (234-236), 136 (236-236), 149 (236-245), 174 (2345-236), and 176 (2346-236) were measured in terms of enantiomeric fractions (EFs). Enantioselectivity was observed for PCBs 84, 91, 95, 136, and 149, but not at all sites studied. Meanwhile, enantioselectivity for PCB 174 was not observed. Evidence of metabolism was found for atropisomeric PCBs 84, 91, 95, and 149. However, only PCB congeners 95 and 149 were observed consistently between the aquatic and riparian species, which are also similar to previous observations for aquatic and riparian biota in Lake Hartwell, SC. A change in EF for PCB 149 occurred consistently in almost all sampling sites and seasons in the riparian species, but the EF of PCB 95 did not change consistently in most species investigated. The EF values for PCB 149 were found to be less than 0.5 in all species. The EF values for 95 were found to be less than 0.5 in clams, mayflies, and amphibians, while the values were found to be nearly racemic in fish and spiders. This observation lends support to the hypothesis that metabolism of PCB congeners occurs in the higher trophic levels.