Application of an integrated environmental monitoring model for natural hydrocarbon seeps in the Gulf of Mexico

An Integrated Environmental Monitoring (IEM) model was applied to study the fate and transport of Hydrocarbon (HC) discharge due to natural seepages in the Gulf of Mexico. The HC seeps that are manifested as a microlayer on the ocean surface that can be detected by remote sensing were chosen for IEM application.;A vertical transport model based on Discrete Particle Random Walk (DPRW) method was applied to obtain the spreading and dispersion of HC droplets in the water column. The horizontal extent of the spreading, dispersion and size of the footprint on the surface were determined from the model. Acoustic Doppler Current Profiler (ADCP) data was used to characterize the subsurface currents in the study area. The model was evaluated by actual field measurements of current speed and direction at different depths and by employing aircraft based remote sensing images of the seep footprints.;The particle tracking random walk model was applied, also, for determination of horizontal drifting extents and degradation of the microlayer. Time-series of wind speed and direction were used as input to the model along with degradation rates derived from literature. The shape and dimension of the microlayer detected and imaged in ERS1-SAR image was measured and employed for evaluation of the drift model. Longitudinal traverse analysis of microlayers from the satellite images was applied to estimate normalized spread of the microlayers. Microlayer covered waters and pristine water transects served as a baseline for comparison. Global Positioning System (GPS) based surface tracking drift buoy experiment in the study area estimated the rate of drifting due to currents and winds. Microlayers were sampled for geochemical analysis along the length to determine the rate of degradation as a function of surfaced time.