Numerous black balls of tar of a few centimeters in diameter appeared in the second week of October on the beaches of Coogee and Gordons Bay, in New South Wales in Australia and then appeared along a stretch of coast of almost 10 km in the area east of Sydney causing alarms and the closure of long stretches of beaches. This hydrocarbon-based polluting debris appeared completely unexpectedly, with no reports of accidents or inadvertent oil releases from passing ships or extraction platforms. For security reasons, the authorities therefore decided to prevent access to the beaches and to study these spheres, looking for information on their origin. Work for the removal and study of the spheres began immediately, also in view of the beach season arriving in the southern hemisphere.
The formation of these spheres It’s not a rare occurrenceand it can also happen following “natural” releases from the seabed, as happens on Californian beaches. What is unusual, however, is the appearance of a such a high number of spheres in just a few days. Events of this magnitude are usually linked to large releases of oil due to human activity. However, there are no known releases so abundant as to justify the numerous spheres on Australian beaches, and this makes these black spheres “mysterious”.
What the black spheres in Australia contain and how they might have formed
The analyses, conducted by the UNSW Mark Wainwright Analytical Centre, confirm the presence of hydrocarbons (molecules made up mainly of carbon and hydrogen) of fossil origincompounds typically present in petrolium. When oil is released into the sea it splits into two main fractions depending on the molecular weight, i.e. the size of the molecules: the lighter ones (volatile compounds) evaporate slowly, but the heaviest part (the compounds called asphaltenes) continue to floating in “blobs”.
Asphaltenes are substances hydrophobicthat is, not similar to water, as is, for example, the oil we use in cooking. In water, therefore, these molecules then tend to join together and to any floating objects: algae, pieces of wood, waste and so on. In the presence of waves, the floating spots can be “broken” into smaller parts and take, over time, spherical shape.
Even the relatively high percentage of volatile compounds still present in the spheres seems to indicate a massive release of oil: in natural losses from the seabed, oil usually undergoes greater environmental degradation, losing a large part of these compounds.
The possible health and environmental risks of this tar debris
The substances contained in these spheres are extremely harmful to marine fauna: they are toxic and if ingested they can easily block the intestinal tracts of fish or birds. In the latter they are also able to damage the plumage making it less waterproof and insulating.
Unfortunately, when such deposits are found on beaches, it is also likely that a good portion is crashed to the seabed: everything that cannot be collected could therefore pollute ecosystems for hundreds of yearsespecially if the asphalt has become bound to plastic waste.
As for the human healthmany of the compounds present in these tarry residues have carcinogenic effects: one more reason to avoid swimming in areas affected by these phenomena. Fortunately the risk of exposure is very reduced in case of solid residues like these spheres, but what causes concern are the volatile compounds and any residues still present in sea water of the affected areas.