Look Before You Leak

In January 1991, a disastrous oil spill occurred in the stormy Irish Sea. The cargo tanker Kimya capsized off England's Bodorgan Head, killing 10 crewmen. The ship eventually settled upright on the bottom, but in shallow water with some 1500 metric tons of oily cargo still in her tanks. The loss of lives and ship made for a significant disaster, but no one except the insurers worried much about the cargo. Unlike Torrey Canyon or Exxon Valdez, Kimya wasn't carrying crude oil; she wasn't carrying petroleum in any form. Her oil came from sunflowers, not rocks.

Sunflower oil, as everyone involved with the shipwreck knew, is a nontoxic product, so biodegradable that even people find it edible. The responsible parties assumed the oil would provide food for marine bacteria, which might benefit the whole local food chain. The bacteria lie near the base of that chain, and they are largely carbon limited; thus the carbon-rich sunflower oil could boost bacterial numbers.

So appealing and convincing was this picture, in fact, that during the next six months, divers were sent down to open and remove the valves on the sunken oil tanks. Kimya was to provide a nutritious oily soup for the local sea life.

Suspicions that this might not be what was happening arose soon after the first oil floated free. Local beachcombers reported finding what looked like wads of used chewing gum up and down the shore. Some of the offensive lumps were sent off to a laboratory for analysis. Back came the alarming results: the wads were polymerized sunflower oil.

It turns out that agitating sunflower oil in sea water causes some of the naturally short molecules composing the oil to link together into longer, more complicated molecules. Nobody had thought to check for this unexpected possibility, but it was easily duplicated in the lab. Sunflower oil in a flask of sea water polymerized when shaken. And shaking was all that was necessary. The plastic-like product formed in sterile or dirty sea water, in the presence of oxygen or with none.

In autumn 1991 the local sea received a fairly large-scale shaking in the course of another violent storm. The storm's action released considerably more oil from the sunken tanker. The oil reached the sandy beaches along Bodorgan Head, where it not only polymerized but bound to the sands. Together, sand and oil formed an aggregate, a kind of weak and pliable concrete. The living creatures of the shore were sealed beneath an impermeable, deadly cap. Pieces of this pavement-like aggregate were still visible as of mid-1994.

Furthermore, even when the oil drifted on calm seas so that it stayed recognizably sunflower oil, not gum or aggregate, the stuff caused trouble. In the first six months after the wreck, scientists found increased levels of sunflower-derived fatty acids in mussels growing on the rocky portions of the nearby shore.

Then the mussels began to die off. A graduate student fed aquarium-dwelling mussels small amounts of different types of vegetable oils along with their daily ration of algae, and discovered that all the oils killed at least some of the mussels. Sunflower oil wasn't the most deadly; even tiny amounts of linseed oil killed up to 70 percent of the captive mussels.

Marine bacteria thrived on all the oils--especially linseed--but only when the oils were not polymerized. Once the polymers formed, like the bacteria employed to chew up crude oil, they needed additional nutrients to accomplish much. In the laboratory, at least, adding more nitrate and phosphate to the sea water flasks led to faster degradation of the gummy lumps.

So it seems that nature still holds many surprises for humankind. It's worth remembering that biodegradable isn't the same as nontoxic; we should indeed look before we leak.