Detailed picture of Rena oil emerging
October 22, 2011
Detailed picture of Rena oil emerging thanks to University of Waikato scientists
Scientists at the University of Waikato have made good progress in understanding the chemical composition of the fuel oil aboard the stricken container ship Rena.
Professor Alistair Wilkins from the university’s chemistry department has examined oil from the ship’s tanks, from surface slicks and from ‘tar balls’ found on the Mt Maunganui beach.
“Oil from the Rena grounding contains polycyclic aromatic hydrocarbon compounds (PAHs), which are known to be harmful to humans and wildlife,” says Professor Wilkins. The levels of these compounds will likely determine when it is safe to eat shellfish and other marine species again.
“These hydrocarbon compounds are the same as those found in fuel oils from around the world but we have yet to determine how much of each compound is present in the Rena oil.”
All of the samples collected contain similar substances to those found in diesel fuel bought from the pump but the proportions of different sized compounds in the mixture is different with Rena oil containing a greater proportion of larger compounds than diesel fuel. It is these large compounds that cause the fuel oil to have the consistency of Vegemite at room temperature.
When the oil from the ship enters the water, the smaller, lighter compounds begin to evaporate rather like paint drying and the end result is a tarry solid such as we have seen deposited on the beach.
Once on the beach, weathering and bacterial action will slowly degrade these deposits but it’s not easy to predict how long this will take. Compounds have also been seen in the oil which may make it possible to distinguish Rena oil from local sources of oil using hydrocarbon ‘fingerprinting’ techniques.
University of Waikato scientists will continue detailed analysis of the oil and it is expected that this information will assist researchers that are already studying the effects of the spill on the coastal environment.
The University of Waikato has been heavily involved since the Rena ran aground on the Astrolabe Reef earlier this month. The Chair in Coastal Science Professor Chris Battershill, other University of Waikato scientists, PhD students, and student volunteers have all been involved from the outset.
Caption for graph:
Graph shows the profile of compounds present in an oil slick sample collected 1.5 km south of the Rena. Straight chain hydrocarbon peaks are labelled. Other hydrocarbons and polyaromatic hydrocarbons (PAHs), including naphthalene and methyl naphthalenes (*) are interspersed between the labelled peaks.