Tar Balls Sully Goan Beaches
By Marianne de Nazareth
14 September, 2010
Countercurrents.org
There was a recent flurry of media stories on the fact the many beaches in Goa were blackened with Tar balls. Especially in South Goa which is known for its pristine white beaches, tar balls continued to muck up the beaches jeopardizing the coming tourist season. The state tourism minister Swapnil Naik announced that manual cleaning had begun, but many locals complained that it was virtually impossible to walk on the Valesao beach especially where the balls had gathered a foot thick along the sea line.
Talking to the National Institute of Oceanography (NIO) about the phenomenon and checking as to how this has happened, they said that this phenomenon has been occurring way back since the ‘70’s. Since Goa is a tourist destination, the tar balls are more noticeable, but apparently according to the NIO this phenomenon occurs elsewhere too along all the coastal areas of India. On the west coast the tar balls appeared mainly from May to October. So, if the media is making an issue of an old phenomenon as per NIO’s records, then threats to the environment are being taken seriously now and hopefully something will get done to sort the issue.
The NIO explained the problem and how it occurs messing the coastline as a consequence. “Tarballs along the coast of Goa arise whenever an oil-slick occurs in the vicinity of the coastline. One common cause for such a slick is dumping oil overboard by a passing ship. But then, why would any ship dump oil overboard? A scenario resulting in such dumping is the following. Consider an oil tanker that routinely transports oil (say diesel) from Mumbai, where it picks up the oil, to Kochi, where it is offloaded. Let us assume that such a tanker operating in coastal areas of India travels along a route that has depth of about 20 m. Along the west coast of India, this would be at a distance of about 20 km from the coastline. After offloading the oil at Kochi, the ship returns, and while on the way, Captain of the ship decides that one of the tanks needs to be cleaned. Though aware that such cleaning would violate internationally accepted norms for preventing oil pollution, he decides to go ahead, since he is aware that enforcement of the norms is not effective along the Indian coast. The cleaning gets done by spraying the tank with jets of heated sea water and then flushing overboard the water now having lot of sticky diesel that was coating the tank. In essence, this operation leads to an “oil-spill”, albeit a minor one, at a distance of about 20 km from the coast. During the first few hours of a spill, the oil spreads into a thin slick. Winds and waves tear the slick into smaller patches that are scattered over a much wider area. Various physical, chemical, and biological processes change appearance of the oil. These processes are generally called “weathering,” says the NIO report.
There could be other ways were a collision between ships could rupture the hull leading to leakage, but this is rare says the NIO. However the NIO points a finger to ‘unscrupulous ships’ violating international rules regarding the cleaning of tanks. Then a number of factors, including characteristics of weathering of spilled oil, and nature of winds at the time of the spill are behind the phenomenon.
The NIO explains: “After a spill, initially, the lighter components of the oil evaporate much like a small gasoline spill. In the cases of heavier types of oil, such as crude oil, much of the oil remains behind. At the same time, some crude oils mix with water to form an emulsion that often looks like chocolate pudding. This emulsion is much thicker and stickier than the original oil. Winds and waves continue to stretch and tear the oil patches into smaller pieces, or tar balls. While some tar balls may be as large as 30 cm in diameter, most are coin-sized or a bit bigger.
Weathering processes eventually create a tar ball that is hard and crusty on the outside and soft and gooey on the inside. Turbulence in the water or beach activity from people or animals may break open tar balls, exposing their softer, more fluid centers. Temperature has an important effect on the stickiness of tar balls. As air and water temperatures increase, tar balls become more fluid and, therefore, sticky-similar to an asphalt road warmed by the summer sun. Another factor influencing stickiness is the amount of particulates and sediments present in the water or on the shoreline, which can adhere to tar balls. The more sand and debris attached to a tar ball, the more difficult it is to break the tar ball open. These factors make it extremely difficult to predict how long a tar ball will remain sticky. In case density of the tar balls happens to be more than density of the ambient waters, then the tar balls sink to the sea floor and can remain there for a long time. More worrisome are the tar balls whose density is less than that of ambient water. These float and can be carried to other places, including to beaches along a coast.”
A lot of this research has been done by Dr. X.N. Verlencar and Dr. Classy D’Silva from the NIO. They explain that the direction of movement of floating tar balls is dependent on winds, waves on the surface of a sea, and currents. The wind pushes a slick (including tar balls) in the direction of wind-flow. Stronger and more persistent the wind, faster is the movement of a tar ball. Waves on sea surface can also push tar balls in the direction in which the waves go. The stronger the waves, the more effective they are in transporting tar balls. Currents carry the tar balls with them and studies by NIO researchers during 1970s showed that chance of occurrence of tar balls along the beaches of the west coast of India is high during May-October. The question arises as to why this should occur only at this time when erring ships that violate code or conduct regarding oil pollution at sea would be passing by the west coast throughout the year. Why then is the occurrence of tar balls higher during May-October?
Apparently along this region, there are three causes - winds, wind-waves, and currents but the factor that propels the tar balls is the wind. Winds along the coast have a well defined annual cycle. Normally winds start blowing towards the coast in May. They keep getting stronger as the monsoon sets and are strongest in July-August. In September and October the winds weaken, and by November they are no more oriented towards the coast. The strength of waves on the ocean surface along the west coast exhibits a pattern that is pretty much the same as the winds: waves get stronger in May, and continue to increase in strength as the monsoon picks up. As a result, the waves are bigger, and the sea much rougher, during the monsoon. These waves move towards the coast and the stronger the waves are, the more effective is the transport of tar balls by them.
Our oceans desperately need to be saved, therefore laws should be put in place to prevent these unscrupulous ships from dumping their waste that is causing this crisis. Education of the negative impacts on the oceans of the sailors manning the ships will go a long way in curbing the problem. Decades have passed since the ‘70‘s but it’s a strong signal if the media has picked up the issue. That is the only way we can put the brakes on this shameful lack of environmental consciousness.
Marianne de Nazareth is Robert Bosch Stiftung fellow, Freelance Journalist and Adjunct faculty St. Joseph's College & COMMITS
http://mariannedenazareth.blogspot.com/
