ACCESS NUMBER: 30660-19920 

STUDY TITLE: Biodegradation of Aromatic Heterocycles from Petroleum Produced 

Water, and Pyrogenic Sources in Marine Sediments 

REPORT TITLE: Biodegradation of Aromatic Heterocycles from Petroleum Produced 

Water, and Pyrogenic Sources in Marine Sediments 

CONTRACT NUMBER: 14-35-0001-30660-19920 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA: Gulfwide 

FISCAL YEAR OF PROJECT FUNDING: 1994 

COMPLETION DATE OF REPORT: October 2000 

CUMULATIVE PROJECT COST: $97,000 

PROJECT MANAGER: W. James Catallo 

AFFLIATION: Louisiana State University 

ADDRESS: Department of Veterinary Physiology, Pharmacology & Toxicology, Baton 

Rouge, LA 70803 

PRINCIPAL INVESTIGATOR: W. James Catallo 

KEY WORDS: Gulf of Mexico; Louisiana; Marine Sediments; Aromatic Heterocycles; 

Biodegradation; Bioremediation; Bioavailability; Toxicity 

BACKGROUND: The wetland and coastal marine environments are being impacted by 

discharges from OCS production and other industrial activities. The potential exists for 

the impairment of function and quality for habitat and other living resources. 

Biodegradation and bioremediation research attempts to develop treatment approaches 

that detoxify pollutant mixtures as well as remove these compounds from affected 

systems. This requires detailed knowledge of the transformation rates and pathways of 

chemicals under different environmental conditions as well as data on the results of 

these reactions in terms of bioavailability and toxicity. 

OBJECTIVES: Marine sediment is being collected and exposed to oxidized and 

reduced conditions in microcosms where each sample is exposed to mixtures of 

heterocycles. The microcosms are incubated and sampled for heterocycles and their 

intermediates. Attempts are being made to enhance the biodegradation of heterocycles 

by selecting for effective microbial communities. This work examines in detail the 

biodegradation pathways and rates of degradation for toxic organic chemicals in marine 

sediments by indigenous microflora. A series of heterocyclic chemicals found in 
ACCESS NUMBER: 30660-19920 

produced waters and pyrogenic products is being examined for biodegradation under 

different physicochemical conditions in sediment-water microcosms maintained in the 

laboratory. 

DESCRIPTION: This report summarizes laboratory studies and associated technical 

development on the influence of hydrology on biogeochemical processes, particularly 

those that govern the transport and transformation of pollutant organic chemicals in 

wetland sediments. The goals were to: 1) determine the effects of static vs. dynamic 

hydrology on biogeochemical behavior of tidal wetland sediment systems, with respect 

to central variables (e.g., redox potential dynamics) and pollutant transformation, 2) 

design and build hydrodynamic microcosms for this purpose that are reproducible, well 

controlled, and adequately monitored in the laboratory and, 3) develop analytical 

approaches for target pollutant chemicals that allow for detection of small but significant 

concentration differences between time points and treatments. The pollutant chemicals 

examined here included representative N-, O-, and S- heterocycles (NOSHs) that occur 

in coal chemicals, crude oils, and pyrogenic mixtures. The target analytes were 

quinoxaline, 2-methylquinoxaline, 2,3-dimethylquinoxaline, benzothiazole, dibenzofuran, 

phenazine, dibenzothiophene, phenothiazine, acridine, and phenanthridine. These and 

other NOSHs are found in in pollutant mixtures near certain industrial activity, 

hazardous waste sites, and major harbors. They are of interest because of their 

apparent stability in aquatic sediments except for certain (turbulent, well-oxidized) 

conditions under which they are labile. Further, many NOSH compounds are acutely 

toxic, with some also mutagenic and/or carcinogenic in mammals. 

SIGNIFICANT CONCLUSIONS: It was found that the physcochemical and biological 

behavior of the sediments in the microcoms was similar to that observed in natural 

settings, and in accord with prevailing theory. Redox potential time series and sediment 

trace gas signatures from the different treatments were analogous to those encountered 

in field settings continuously flooded and drained systems had reduced (mean - 428 

mV) and oxidized (+ 73 mV) Eh values, respectively, with no evidence of daily or longer 

periodic variation. The tidal systems exhibited oscillating Eh values, with significant 

amplitudes (40 – 180 mV/0.5 d). Biogeochemical gas mixtures leaving the sediments 

also reflected the hydrological status of the treatments: the major gases observed were 

CO2 from microbial respiration (drained) vs. CO2 with small sulfide and methane outputs 

(tidal), vs. relatively large amounts of sulfides and methane. Transformation of the 

NOSH analytes was different in each of the hydrologic regimes, with the rate of 

transformation and the number of NOSHs degraded decreasing in the following order: 

drained > tidal > flooded. 

STUDY RESULTS: The results indicated that sediments and associated biota exposed 

to tidal pulsing (analogous to a streamside salt marsh ecophene) removed more NOSH 

compounds faster and to lower levels than a flooded sediment (analogous to a flooded 

interior ecophene or an impounded system). Of the two wetland possibilities (tidal vs. 

flooded), the tidal systems were better able to transform the NOSH compounds. From a 

contaminated sediment perspective, an optimal remediation strategy for these NOSHs 

would encompass dredging of affected areas followed by upland placement and tilling to 
ACCESS NUMBER: 30660-19920 

maintain well-oxidized conditions. From an ecological perspective, promoting in situ

remediation of NOSHs and other organic pollutants would involve exposing as much 

contaminated sediment as possible to the action of tides, while minimizing the area 

exposed to prolonged flooding. 

STUDY PRODUCTS: W. J. Catallo. 2000. Biodegradation of Aromatic Heterocycles 

from Petroleum-Produced Water and Pyrogenic Sources in Marine Sediments. OCS 

Study MMS 2000-060. A final report by the Louisiana State University for the U.S. 

Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, 

New Orleans, LA. Contract No. 14-35-0001-30660-19920.