ill. (some color), maps; "Printed October 28, 1998." - T.p.; Bibliography: p. 29-35
EXECUTIVE SUMMARY The objective of the present investigation was to conduct the first comprehensive assessment of the levels and distribution of petroleum hydrocarbons in Crater Lake water and sediments. Samples representative of different inputs were collected and analyzed to assess hydrocarbon concentrations and compositions. Various sampling sites were selected to best represent the distributions and concentrations of hydrocarbons, BTEX and PAH products from petroleum combustion sources. The results show that boat fueling and tour and research boat operations are unavoidably introducing petroleum hydrocarbons and their combustion residues to the lake. The primary petroleum hydrocarbons found in surface slicks have been identified as exhaust products and motor lubricating oil residues from internal combustion engines. Chemical analysis shows that normal and isoprenoid alkanes and an envelope of an unresolved complex mixture (UCM) of branched and cyclic hydrocarbons, typical of petroleum, are detectable in surface slicks at different sites of Crater Lake. The measured level of total surface slick petroleum hydrocarbons as n-alkanes ranges from 800-1600 |Lig/m2, which is an upper concentration limit equivalent to background. The concentrations and distributions of total polycyclic aromatic hydrocarbon (PAH) products on the lake surface, as a thin film, are essentially constant at about 0.080 |Lig/m2 and reflect background levels. The PAH components are shown to be derived strictly from engine exhaust and not from wood smoke in aerosol fallout. In the water column, the BTEX products (benzene, toluene, ethylbenzene, xylenes), from gasoline combustion, were not found at concentrations above the procedural blanks used for this analysis (<5.0 ug/l). Thus, the BTEX concentrations in the water column are not significant. Analyses for heavier petroleum hydrocarbons dissolved in the water column were not conducted because their solubilities are low and they were at background concentrations in surface slicks. Petroleum hydrocarbons in the water column are adsorbed to particulate material which ultimately sinks to the lake sediments. All shallow sediments near the boat docks show the presence of petroleum residues from motor exhaust, mainly from boat traffic. In nearshore sediments collected at Cleetwood Cove and at the Cleetwood Cove boat mooring area, the impact of the increased boating activity is obvious. The concentrations of petroleum n-alkanes in sediments collected at 5 m water depth at the Cleetwood Cove boat mooring area (1.44 mg/kg) exceed the petroleum and plant n-alkane concentrations for all other sediment sampling sites. The petroleum n-alkane concentrations are greater than plant n-alkane concentrations in all near shore sediments which indicates that boating activities impart a detectable level of petroleum hydrocarbons to I the sediments. Aliphatic petroleum hydrocarbons are at background levels in the sediments of North Basin (616 m water depth, 16 ug/kg). The UCM was a minor component in shallow sediments and was not found at levels above the instrument detection limits in deep sediments. The PAH concentrations in all sediments range from 15.5 (616 m water depth) to 40 ug/kg (5 m water depth) and reflect background levels. The trace but recognizable occurrence of petroleum biomarkers, such as the tricyclic terpanes, hopanes and steranes, further confirms petroleum product input to shallow sediments. Aerosol fallout was identified as a potential minor contributor of petroleum hydrocarbons to surface water of the lake via atmospheric particle deposition. Extractable and elemental carbon analyses of aerosols collected near the caldera rim show that anthropogenic hydrocarbons associated with particles are present at detectable concentrations. There is also a seasonal component of natural hydrocarbons from higher plants in the aerosols during spring through summer. Overall, the total petroleum hydrocarbon concentrations in Crater Lake are low and are found at concentrations similar to background levels in all environmental samples. However, boating activities are introducing petroleum hydrocarbons and their combustion residues to the lake, as is evident from chemical analysis of environmental samples. The effect of this contamination on the natural environment of the lake is not known at this time. It is well documented that petroleum products (e.g., UCM, biomarkers) and their combustion residues (e.g., PAH) are persistent in the environmental compartments of soil, water and sediment. Their increasing presence in the lake can ultimately pose problems depending on their concentrations, partitioning behavior between environmental and biological compartments, and lifetimes. ii
EXECUTIVE SUMMARY The objective of the present investigation was to conduct the first comprehensive assessment of the levels and distribution of petroleum hydrocarbons in Crater Lake water and sediments. Samples representative of different inputs were collected and analyzed to assess hydrocarbon concentrations and compositions. Various sampling sites were selected to best represent the distributions and concentrations of hydrocarbons, BTEX and PAH products from petroleum combustion sources. The results show that boat fueling and tour and research boat operations are unavoidably introducing petroleum hydrocarbons and their combustion residues to the lake. The primary petroleum hydrocarbons found in surface slicks have been identified as exhaust products and motor lubricating oil residues from internal combustion engines. Chemical analysis shows that normal and isoprenoid alkanes and an envelope of an unresolved complex mixture (UCM) of branched and cyclic hydrocarbons, typical of petroleum, are detectable in surface slicks at different sites of Crater Lake. The measured level of total surface slick petroleum hydrocarbons as n-alkanes ranges from 800-1600 |Lig/m2, which is an upper concentration limit equivalent to background. The concentrations and distributions of total polycyclic aromatic hydrocarbon (PAH) products on the lake surface, as a thin film, are essentially constant at about 0.080 |Lig/m2 and reflect background levels. The PAH components are shown to be derived strictly from engine exhaust and not from wood smoke in aerosol fallout. In the water column, the BTEX products (benzene, toluene, ethylbenzene, xylenes), from gasoline combustion, were not found at concentrations above the procedural blanks used for this analysis (<5.0 ug/l). Thus, the BTEX concentrations in the water column are not significant. Analyses for heavier petroleum hydrocarbons dissolved in the water column were not conducted because their solubilities are low and they were at background concentrations in surface slicks. Petroleum hydrocarbons in the water column are adsorbed to particulate material which ultimately sinks to the lake sediments. All shallow sediments near the boat docks show the presence of petroleum residues from motor exhaust, mainly from boat traffic. In nearshore sediments collected at Cleetwood Cove and at the Cleetwood Cove boat mooring area, the impact of the increased boating activity is obvious. The concentrations of petroleum n-alkanes in sediments collected at 5 m water depth at the Cleetwood Cove boat mooring area (1.44 mg/kg) exceed the petroleum and plant n-alkane concentrations for all other sediment sampling sites. The petroleum n-alkane concentrations are greater than plant n-alkane concentrations in all near shore sediments which indicates that boating activities impart a detectable level of petroleum hydrocarbons to I the sediments. Aliphatic petroleum hydrocarbons are at background levels in the sediments of North Basin (616 m water depth, 16 ug/kg). The UCM was a minor component in shallow sediments and was not found at levels above the instrument detection limits in deep sediments. The PAH concentrations in all sediments range from 15.5 (616 m water depth) to 40 ug/kg (5 m water depth) and reflect background levels. The trace but recognizable occurrence of petroleum biomarkers, such as the tricyclic terpanes, hopanes and steranes, further confirms petroleum product input to shallow sediments. Aerosol fallout was identified as a potential minor contributor of petroleum hydrocarbons to surface water of the lake via atmospheric particle deposition. Extractable and elemental carbon analyses of aerosols collected near the caldera rim show that anthropogenic hydrocarbons associated with particles are present at detectable concentrations. There is also a seasonal component of natural hydrocarbons from higher plants in the aerosols during spring through summer. Overall, the total petroleum hydrocarbon concentrations in Crater Lake are low and are found at concentrations similar to background levels in all environmental samples. However, boating activities are introducing petroleum hydrocarbons and their combustion residues to the lake, as is evident from chemical analysis of environmental samples. The effect of this contamination on the natural environment of the lake is not known at this time. It is well documented that petroleum products (e.g., UCM, biomarkers) and their combustion residues (e.g., PAH) are persistent in the environmental compartments of soil, water and sediment. Their increasing presence in the lake can ultimately pose problems depending on their concentrations, partitioning behavior between environmental and biological compartments, and lifetimes. ii