Microbial and Photochemical Degradation of Polycyclic Aromatic Hydrocarbons in Estuarine Waters and Sediments

Abstract

Radiolabeled polycyclic aromatic hydrocarbons (PAH) containing up to three rings, including naphthalene, methylnaphthalenes, and phenanthrene, were degraded (measured by 14CO2 production) in water samples from both Narragansett Bay and southeastern United States. Higher weight PAH, including benz[a]anthracene, chrysene, fluorene, and anthracene, showed little, if any, degradation in water but were readily degraded when added to sediment–water slurries. In areas with low levels of petroleum in the water or sediment there was a lag before appreciable degradation began, and the rate of degradation fitted a first-order equation. Half-lives, calculated for the various PAH added to water or sediment–water slurries, were very low during winter months; [14C]methylnaphthalene added to water from Skidaway River, Georgia, in January (8 °C) was 57 d, while in September (28 °C) it was 3 d. PAH added to sediments or water from oil-treated areas or mesocosms were rapidly degraded with no lag phase and the degradation rate was linear. [14C]Methylnaphthalene added to water from control and oiled mesocosms in May (10 °C) had half-lives of 300 and 5 d, respectively. We plotted the changes in turnover times with changes in the concentration of PAH and calculated the natural turnover times and Vmax for PAH added to water or sediment from the oiled mesocosms. When [14C]dimethylbenz[a]anthracene was incubated in water in the dark no degradation occurred, but when exposed to sunlight, 0.3% was mineralized in 18 h. In addition, a variety of photooxidation products were produced. The production of 14CO2 in the light was due to microbial degradation of photooxidation products of [14C]dimethylbenz[a]anthracene.

PAH assessment in the main Brazilian offshore oil and gas production area using semi-permeable membrane devices (SPMD) and transplanted bivalves

“…Naphthalenes are volatiles and are more soluble than phenanthrenes and dibenzothiophenes. Furthermore, naphthalene degradation has been reported in waters from pristine and oil-contaminated ecosystems (Lee et al, 1978, Herbes and Schwall, 1978, Lee and Ryan, 1983, Massie et al, 1985. Naphthalene is relatively water soluble (31.2 mg L À 1 ) and has such a high vapor pressure (0.23 mmHg) that biodegradation and volatilization in open waters may be important processes that affects its fate in aquatic systems.…”

Triphenyltin and its degradation products in foliage and soils from sprayed pecan orchards and in fish from adjacent ponds

“…Carbon-14-triphenyltin hydroxide was added to each sample. After incubation at 27ЊC for 2, 7, and 14 d, respired 14 CO 2 was collected by trapping on phenethylamine-soaked paper and counted in a liquid scintillation counter [19]. Controls were soil samples containing 10% formalin.…”

Hydrocarbon Degradation Potential in Reference Soils and Soils Contaminated with Jet Fuel

“…'-C-labeled hydrocarbons were added to soil mixed with water (5 g soil with 10 mL water) in 250 mL flasks capped with silicon stoppers. After incubation at room temperature (20 C the respired 'CO 2 was collected by trapping on phenethylamine paper and counted in a liquid scintillation counter (for details of this procedure see Lee and Ryan 1983). Controls were soil samples containing 10 percent formalin.…”

“…This technique, often refen-ed to as hydrocarbon degradation potential, has been used to evaluate hydrocarbon degradation in natural waters and soils (Atlas 1979;Lee and Ryan 1983;Scheunen ei al. 1987).…”