The proposed efforts address how wetlands and shoreline environments recover from the impacts of dispersant-mixed oil which washed ashore from the Deep Water Horizon (DWH) event. The overall economic recovery of the Alabama coastal region is strongly linked to the environmental quality of its shoreline areas. The overall goal of this proposal is to conduct field and mesocosm studies to demonstrate and understand the recovery patterns of coastal marshes and shorelines.
Specifically, we will test the following research hypotheses:
1. Rate of coastal marsh recovery and the distribution of oil in the ecosystem will depend on the dominant species, weathered oil condition, and the amount of oil exposure
2. Recovery of beach environments can be tracked and demonstrated by tracing hydrocarbon (multiple PAH) levels using a GC/MS
A total of 32 wetland mesocosms will be established in Auburn, Alabama to evaluate how coastal marshes recover from oil and how oil is distributed throughout the ecosystem following various levels of exposure. Oil weathering can strongly influence plant response and we will examine how different levels of weathering coupled with exposure rates influence marsh plants. Plant structural and physiological conditions will be measured monthly and include photosynthesis rates, stem density, average plant height, and the number of inflorescence. As part of this study, we will track the distribution and content of oil constituents in the wetlands relative to the total exposure. The fate of oil in wetlands will be determined by measuring multiple PAH species (polyaromatic hydrocarbons) content in marsh soil and plant tissue using a GC/MS system.
We also propose to examine the fate of oil washed onto to sandy shorelines. This work will build on past sampling in the Orange Beach area--one before (background samples) and one after the arrival oil spill. We propose to continue and extend these sampling efforts along the beach (collect about 15 to 20 samples) and in the littoral zone.
Future sampling events will be also linked to hydrological forcing such as hurricanes or other major storm events. We will monitor the long-term recovery of the beach ecosystem by tracking more toxic chemical parameters such as PAH concentrations levels released from the residual hydrocarbon material buried in the near-shore environment. We will be using two types of sampling methods that would include grab samples using Ponar, and core sample using suction tube cores. These samples will be analyzed for PAHs and other indicators.
The Department of Civil Engineering team has recently received a National Science Foundation MRI grant to develop an advanced analytical facility that will house a Pyrolysis-coupled gas chromatographic system with quadrupole MS/MS mainframe (GC/MS/MS system). The GC-MS system when coupled pyrolysis is an efficient tool for rapid analysis of complex organic matrices, and it can provide specific fingerprints that can be used for structural identification of various oil components (Sicre et al. 1994). Our techniques provide well-known advantages, such as the small sample mass required, the minimal sample preparation and the opportunity of selective sample purification (Teran et al. 2009).
Py–GC/MS/MS based methods will also offer a unique opportunity to characterize asphaltenes, which are an important class of crude oil component which are difficult to extract from soils and are mostly too large to resolve by standard GC/MS techniques. Thus, tracking of asphaltenes could serve as a marker to determine the source of petroleum contamination even after many years of exposure. Our equipment is also programmed to measure over 25 PAH compounds using a specially designed main column fitted with a back-flush column. All of our PAH analysis will be completed using this method.