Tar balls surface on Goa Colva beach

Tar balls have revisited one of the states pristine beaches, Colva, on Friday leaving an ugly 2-metre wide scar along its length. "They came with the tide in the morning," said Raju, a fisherman originally from Andhra Pradesh.These covered at least 2 metre wide stretch along the length of the beach and were globules of jelly like substance, they said, readying their boats for an early start.

However, the security supervisor on the beach said that these tar balls had made their presence for the past two days but in small quantities and most were washed back with the current. But today the size and the quantity was much greater, he added.

The fisherman as well as the security personnel said that the beach cleaners had cleaned up some of the tar balls. This phenomenon seems to be revisiting the state's famous beaches like clockwork, when the monsoon begins and when it is about to end, said people on the beach side. Studies done have pointed to the fact that this oil is most likely dumped from passing vessels as well as local vessels and settles at the bottom only to be brought to shore under special circumstances when the tide turns. NIO's researchers first came across them way back in 1970s. Research showed that their appearance on the west coast was usually seasonal, with high likelihood during May-October.

Ships clean their tanks, though aware that such cleaning would violate internationally accepted norms for prevention of water pollution. They clean the tanks by spraying it with jets of heated seawater and then flushing the water out. During the first few hours of a spill, the oil spreads into a thin slick. But the winds and waves tear the slick into smaller patches that are scattered over a much wider area. After physical, chemical, and biological processes the appearance of the oil is changed by a process known as 'weathering.'

Research shows that some tar balls may be as large as 30 cm in diameter, most are coin-sized or a bit bigger and the weathering process creates a tar ball that is hard and crusty on the outside and soft and gooey on the inside. The direction of movement of floating tar balls is very much dependent on winds, waves on the surface of a sea, and currents. 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.