**ACCESS NUMBER: 30470.22**

**STUDY TITLE**: University Research Initiative on the Effects of
Offshore Petroleum Development in the Gulf of Mexico.

**REPORT TITLE**:

**CONTRACT NUMBER**: 14-35-0001-30470.

**SPONSORING OCS REGION**: Gulf of Mexico.

**APPLICABLE PLANNING AREA(S)**:

**FISCAL YEAR(S) OF PROJECT FUNDING**: 1992-1994.

**COMPLETION DATE OF REPORT**: January 1994.

**COST(S)**: FY 1992/93: \$86,827; FY 93/94: \$69,357.

**CUMULATIVE PROJECT COST**: \$155,983.

**PROGRAM MANAGER**: Paul W. Sammarco.

**AFFILIATION**: Louisiana Universities Marine Consortium (LUMCON).

**ADDRESS**: 8124 Highway 56, Chauvin, Louisiana 70344.

**PRINCIPAL INVESTIGATOR(S)\***: W. James Catallo and Robert P.
Gambrell\*.

**KEY WORDS**: N-, O-, S- heterocycles, azaarenes, marine/estuarine
sediments, degradation, transformation pathways, toxicity, mutagenicity,
environmental chemistry, microbes, molecular modeling, deuterated tracer
studies, mass spectrometry.

**BACKGROUND**: N-, O-, S- heterocycles (NOSHs) occur in crude oils,
coal- and petro-chemicals, produced waters, and pyrogenic products found
in marine systems. Detailed studies on the environmental chemistry and
toxicology of these compounds in marine sediment and water are necessary
for evaluating the impacts of energy development/transportation,
industry, and waste disposal in coastal marine systems.

**OBJECTIVES**: A. To provide quantitative data on the fates of
prominent NOSH compounds in three marine sediments under oxidized and
reduced electrochemical conditions. B. To determine the transformation
pathways of selected compounds and evaluate the toxicological
significance of NOSH transformation in situ. C. To provide information
on the environmental chemistry and microbiology of NOSHs introduced to
marine sediments from petroleum and pyrogenic sources.

**DESCRIPTION**: The fates and toxicological significance NOSH compounds
and mixtures in different marine sediments were evaluated in laboratory
microcosms. Methods were developed for chemical analysis, transformation
pathway determination, isolation microbial degraders, and deuterated
tracer/metabolic pathway experiments. Relative rates of degradation of a
complex mixture of NOSHs were determined in three marine sediments under
oxidized and reduced electrochemical conditions. The cytotoxicity of
water and sediment samples was determined over a time course of NOSH
compound degradation. The identities of stable transformation products
were determined using mass spectrometry, and deuterated tracer compounds
were synthesized and used to confirm product analysis and postulate
metabolic mechanisms involved in the transformations of selected NOSHs.
Microbes degrading the NOSHs were isolated and characterized. Mechanisms
of NOSH sediment chemistry also were evaluated.

**SIGNIFICANT CONCLUSIONS**: Many NOSH compounds can be degraded in
sediment water systems under oxidized and reduced conditions if those
sediments are constantly stirred. In quiescent sediment profiles
characteristic of natural marine systems, NOSHs are transformed to a
much lesser extent. In both stirred and unstirred systems, partial
transformation products accumulated. Several of these products were
mobile, toxic and/or potentially carcinogenic. Although not transformed
rapidly under natural conditions in sediments, NOSH compounds can be
mobile in heterogeneous sediment water systems. Mechanisms of NOSH
transport through these systems include complexation with soluble and/or
redox active metals (e.g., Fe), protonation to water soluble ion pairs,
electrochemical oxidation or reduction to polar species, and entrainment
in colloidal or soluble organic matter.

**STUDY RESULTS**: The effects of redox potential (Eh) and sediment
particle size distribution on NOSH degradation were examined using
stirred, controlled Eh sediment-water microcosms, and sealed, unstirred
microcosms approximating natural sediment profiles sediment-water
microcosms, and sealed, unstirred microcosms approximating natural
sediment profiles. Results from the controlled Eh microcosms showed that
most NOSHs were transformed in the mixed sediment slurries under
oxidized and reduced conditions. Unstirred microcosms simulating field
conditions showed much less NOSH degradation. In both stirred and
unstirred sediments, NOSH degradation proceeded more slowly and on fewer
compounds in fine grained clay than in coarse grained sand and silt. In
unstirred sediments, however, reduced redox conditions generally favored
NOSH compound degradation relative to oxidized conditions, while this
effect was attenuated under stirred conditions. The sediment microbial
communities of the microcosms were affected by NOSHs: within 7 days of
exposure to 19 NOSH compounds (50 ppm each), aerobic samples showed
reduction or elimination of gram (+) bacteria and termination of fungal
growth. The anaerobic community was not appreciably affected by NOSHs.
Microbes isolated from both oxidized and reduced NOSH microcosms showed
rapid growth on single and crude oils containing NOSHs. Single compound
growth favored mainly one or tow *Psuedomonas sp*., with an actinomycete
also observed when co-substrates were introduced along with the NOSHs
(e.g., alkanes and aromatics in the carbon black). The cytotoxicity of
aqueous phase samples from the stirred microcosms generally decreased
with time and progressive NOSH degradation. The level of measured
aqueous cytotoxicity, however, oscillated before becoming consistently
low after about 7 weeks. Under oxidized and reduced conditions, stable
NOSH transformation products accumulated. These tended to be oxygenated,
water soluble system with potentially significant chemical and
toxicological characteristics (e.g., redox cycling, metal complexation).
The major metabolic processes represented by the transformation products
were a) oxidation to phenols, ketones, carboxylic acids, and alcohols,
2) saturation of aromatic rings and disproportionation of heterocyclic
atoms (e.g., protonation of N and O, oxidation and S), 3) opening of
aromatic rings followed by b oxidation (or decarboxylation of oxidized
alkyl groups), and 4) a complex series of addition reactions (observed
with benzothiazole). Some NOSH products were structurally similar or
identical to know carcinogens, so the effects of microbial action was to
increase toxicity and availability of some NOSHs, at least temporarily.
Reactions including iron-NOSH complexation and chemical redox reactions
in situ were found to be important to NOSH fates in sediments. The
stirring and vigorous mixing of the sediments in the controlled Eh
microcosms obscured this effect, and stimulated the degradation of most
NOSH compounds under oxidized and reduced conditions. Hence the stirred
microcosms gave over-estimates of NOSH degradation in sediment-water
systems typical of most estuarine environments.

**STUDY PRODUCT(S)**: Catallo, W. James and Robert P. Gambrell. Fates
and Effects of N-, O-, and S-Heterocycles (NOSHs) from Petroleum and
Pyrogenic Sources in Marine Sediments. Final report submitted to the
U.S. Department of the Interior, Minerals Management Service, Gulf of
Mexico Region, OCS Office, New Orleans, LA. Contract Number:
14-35-0001-30470. OCS Study MMS 94-0056, 72 pp.

**\*P.I.\'s affiliation may be different than that listed for Program
Manager(s).**