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I l- I I , I f J J t t -' I I , J I I t II 001553 Introduction Polycyclic aromatic hydrocarbons (PAH) are composed of hydrogen and carbon atoms arranged as two or more benzene rings (Eisler 1987). Basic structures of naphthalene, phenanthrene and benzo[a]pyrene are shown below in Figure 1. As the molecular weight of these compounds increases, solubility in lipids increases and resistance to oxidation and reduction decreases. Therefore, PAHs will vary in their behavior in the environment and in their biological effects. Low molecular weight PAHs such as naphthalene and phenanthrene are highly mobile in the aquatic environment and present significant acute toxicity to many organisms. Also, many higher molecular weight PAHs such as benzo[a]pyrene have been shown to be highly carcinogenic (Eisler 1987). co,.. '.;;:: :-.. I ~3 Naphthalene GoHs ; mol. wt. 128.16 Phenanthrene qlli.o; mol. wt.178.22 Benzo[a]pyrene c;JI12; mol. wt. 252.3 Figure 1. Chemical structures and molecular weights of naphthalene, phenanthrene and benzo[a]pyrene (adapted from Eisler 1987). PAHs are ubiquitous in the environment, produced in small quantities through terrestrial vegetation and microbial synthesis and volcanic activity and on a larger scale by forest and prairie fires as well as man's anthropogenic processes (Eisler 1987). Anthropogenic activities which distribute PAH contaminants throughout the San Juan River basin include petroleum production and refining, coal mining, fossil fuel power generation, disposal of municipal and domestic sewage, and agricultural irrigation projects. Throughout the basin, there are in excess of 20,000 oil and gas wells and several petroleum processing plants, including oil refineries, gas processing plants, and conveyance pipelines. These energy- development facilities can all contribute heavily to the release of fossil fuel related contamination, including PAHs, into the surrounding environment. (Petty et al.1992) Some PAH compounds have received much attention because of their suspected or confirmed carcinogenic and mutagenic nature (Eisler 1987). Exposure of biota to PAHs can cause deleterious effects at the site of contact and via the circulatory system, throughout the various organs and tissues (Lee and Grant 1981). Laboratory animals exposed to PAHs have exhibited carcinogenic responses and bottom dwelling fish from PAH polluted waterways have produced oral, dermal, and hepatic neoplasms (Pucknat 1981; Couch and Harshbarger 1985). The presence of pollutants such as BaP in fish taken from contaminated environments generally reflects sedimentary PAH concentrations (Johnston and Baumann 1989). Because of the variation among these compounds and individual species response, it is difficult to make generalizations regarding the class of PAH metabolites (Lee and Grant 1981). However, biliary concentrations of specific PAHs can be compared between fish from polluted waterways with those from reference sites (Krahn et al 1984). The San Juan River basin is important habitat for a wide array of fish and wildlife resources. Major habitat types include aquatic, riparian, grassland, desert shrub, pinon/juniper woodland, ponderosa pine, mixed conifer, and alpine tundra. One hundred :t,,-