Biomarkers May Determine How Long Oil Lingers In The Environment

Brett Smith for – Your Universe Online

While oil from the 2010 Deepwater Horizon oil spill isn’t visible on the surface of the ocean, it continues to wash ashore in the form of small “patties” of oil and sand.

In an attempt to analyze and learn about this oil, researchers from the Woods Hole Oceanographic Institution in Massachusetts have developed a system for determining the source and fate of petroleum hydrocarbons in the environment, according to a new report published in the journal Environmental Science & Technology.

“We were looking at two questions: how could we identify the oil on shore, now four years after the spill, and how the oil from the spill was weathering over time,” said study author Christoph Aeppli, a marine chemistry and geochemistry researcher at WHOI during the research.

The study team applied extensive two-dimensional gas chromatography (GCxGC) to assess levels of degradation in biomarkers, or molecular fossils, found within the oil. Each source of oil has specific quantities of distinct biomarkers, which can serve as identifiers, like human fingerprints or DNA. These biomarkers are typically inert in reservoirs, but when subjected for a long period of time to the ecosystem, some are modified due to normal processes. Oil includes tens of thousands of compounds, and many of them can be broken down by bacteria or even sunlight. The new study was focused on figuring out the durability of specific biomarkers and to see how they performed when exposed to conditions on shore.

“We found that some biomarkers—homohopanes and triaromoatic steroids (TAS), specifically – degraded within a few years following the Deepwater Horizon spill,” said study author Chris Reddy, a marine pollution expert at WHOI. “These biomarkers are not as resilient as once thought and they may provide a future window into determining how much, and how quickly, these oil components may linger in the environment when exposed to air, sunlight, and the elements.”

The team also looked into the source of the biomarkers degradation via the analysis of the Gulf Shore “patties” collected over a 28-month period. The researchers reported most biomarker compounds were robust and could be used to identify oil from the 2010 spill. Some biomarkers, however, degraded too quickly.

“This knowledge is helping us improve our oil spill forensics,” Aeppli said. “It is providing a foundation for better, longer-term identification techniques that account for exposure of oil to wind, waves, sunlight, and microbial degradation over long times.”

In April – on the fourth anniversary of the spill – BP announced it had ended its “active cleanup” of Louisiana’s coast, which follows last year’s end of active cleanup in Florida, Alabama and Mississippi.

The Coast Guard announced it would be transitioning from its active cleanup phase to a new response phase in which crews and equipment will be pre-positioned for future response to cleanup if new reports of oil contamination surface.

“Our response posture has evolved to target re-oiling events on coastline segments that were previously cleaned,” said Coast Guard Capt. Thomas Sparks, the federal on-scene coordinator for the BP response to the spill. “But let me be absolutely clear: This response is not over – not by a long shot. The transition to the Middle Response process does not end clean-up operations, and we continue to hold the responsible party accountable for Deepwater Horizon cleanup costs.”

Image 2 (below): Years after the 2010 Deepwater Horizon Oil spill, oil continues to wash ashore as oil-soaked “sand patties.” Credit: Catherine Carmichael, Woods Hole Oceanographic Institution