Volatile organic compounds in Gulf of Mexico sediments

Volatile organic compounds (VOC), concentrations and compositions were documented for estuarine, coastal, shelf, slope, and deep water sediments from the Gulf of Mexico. VOC were measured (detection limit {dollar}>{dollar}0.01 ppb) using a closed-loop stripping apparatus with gas chromatography (GC) and flame ionization, flame photometric, and mass spectrometric detectors. The five primary sources of Gulf of Mexico sediment VOC are: (1) planktonic and benthic fauna and flora; (2) terrestrial material from riverine and atmospheric deposition; (3) anthropogenic inputs; (4) upward migration of hydrocarbons; and (5) transport by bottom currents or slumping.; Initially sediment VOC concentrations are controlled by the amount and type of VOC sources. VOC are then modified and redistributed by biological, geological, physicial and chemical processes. Total VOC concentrations range from 8 ng/g to greater than 7000 ng/g. GC patterns of VOC have recognizable fingerprints that are source specific. VOC in the Green Canyon sediments were a very complex mixture ({dollar}>{dollar}400 individual VOC). VOC at this location result from the upward migration of petroleum hydrocarbons. Similar sediment VOC were observed in Mississippi Canyon and Orca Basin sediments. In contrast, simple mixtures of VOC are found in the Sigsbee Deep, Garden Banks, and Mississippi River delta sediments. The VOC contain less than 40 compounds (generally {dollar}<{dollar}1.0 ppb). The major source of VOC at these sites is biological activity and debris as evidenced by the predominance of functionalized compounds. At several sites (i.e. the Sigsbee Deep and the Mississippi River delta) functionalized compounds are a majority of the VOC. Houston Ship Channel and Galveston Bay sediment VOC are sourced from biological debris, petroleum (shipping activities), automobile exhaust, and industrial complexes.; Detected organo-sulfur compounds include alkylated sulfides, thiophene, alkylated thiophenes, and benzothiophenes. Benzothiophenes are petroleum related. Low molecular weight organo-sulfur compounds result from the biological oxidation of organic matter. A lack of organo-sulfur compounds in the reducing environment of the Orca Basin may result from a lack of free sulfides (H{dollar}sb2{dollar}S) which are necessary for their production.