Black dust riddle solved as study points to power plant

The black dust that has plagued Fgura and its environs is generated by the Marsa power station, a University study has indicated.

The report’s author, Alfred Vella, who heads the Uni­ver­­sity’s Chemistry Department, concluded that the “most likely candidate source” for black dust collected from the Fgura area was the power plant.

Traffic pollution was ruled out as a possible source of the coarse and relatively big black dust particles that have been a nuisance to residents for more than a decade.

The study published yesterday was commissioned by the Malta Environment and Planning Authority and covers the period between August 2009 and March 2010.

A study conducted in 2000 by British experts had also concluded that the Marsa power station was the “likely” source of black dust in Fgura after traces of heavy metals were found in the samples.

However, in 2009, after mounting complaints from Fgura residents, a Mepa study proved inconclusive since no heavy metals were found.

The black dust phenomenon remained unresolved and criticism of the authority’s failure to pinpoint the problem eventually led to the formation of a parliamentary select committee that was tasked to investigate the matter.

The new study, endorsed by Mepa, is likely to close the chapter on the black dust blame-game even though residents have long maintained that the Marsa power station was to blame.

Prof. Vella said the black colour and structure of the larger particles were typical of particles emitted in a molten state from a high temperature source such as a combustion process or foundry.

The study also took note of wind conditions and found that a significant source of combustion-generated black dust was likely to be responsible for the black particles in atmospheric dust deposited in the south eastern direction at a distance of between one and three kilometres from the Grand Harbour. The worst affected towns were Fgura, Senglea and Tarxien.

The report concluded that the most likely candidate source was the Marsa power station.

“There are no other stationary combustion sources in the Grand Harbour area of such magnitude as to constitute credible alternative sources. While ships transiting the short distances within the harbour waters may also have emitted smoke particles, their intermittent short-lived contributions are likely to be very minor in comparison with the continuous output from the power station.”

The conclusion was corroborated by limited results of chemical analysis of the black particles found in the Fgura dust.

Some of the black spherical particles were found to contain carbon, sulphur, silicon, chlorine, iron, aluminium, calcium, nickel, vanadium and magnesium. The report did not enter into the potential health hazards of these particles.

Prof. Vella said the joint presence of carbon, nickel and vandamium “strongly suggested” that the dust originated from the combustion of fuel oil. The Marsa power station runs on heavy fuel oil.

“The presence of magnesium in the black particles can be explained by the fact that magnesium-containing chemicals are used as additives for the fuel,” Prof. Vella said, although the chemical is also found in rocks.

Traffic exhaust was ruled out as the source of the coarse black particles observed in the study. “Motor emissions produce a different kind of black dust which is much finer in size.

“It appears certain that the Marsa power station has been a constant source of emission of coarse black particles for a long time and that such a strong and constant source has left a clear mark or signature of pollution which is hard to miss,” Prof. Vella said.

He noted that a 1995 study on the impact of atmospheric pollution on church limestone surfaces had also reached the conclusion that the Marsa power station was a source of black dust contamination.

The new study was part of a larger work on the deposition of atmospheric coarse-sized particles in Malta and Gozo that focussed on the presence in such dust of chemical contaminants believed to originate almost exclusively from fireworks.

It was conducted by two university students and a German geologist as part of a thesis supervised by Prof. Vella and Bernardette Aquilina from the University’s chemistry department.

The report published yesterday by Mepa focussed solely on the black particles in dust and, despite its conclusions, Prof. Vella said these would have to be tested and confirmed by proper and sufficient scientific examination.

In a statement Mepa said that two years ago it established emission limit values for dust, sulphur dioxide and nitrogen oxides at the Marsa power station when it issued an environmental permit (Integrated Pollution Prevention and Control).

When Malta joined the EU in 2004 the Marsa power station was granted a temporary lifeline of 20,000 operational hours after which it had to be shut down. The time limit expired earlier this year and the government is currently in talks with the European Commission to get an extension until the Delimara power station extension becomes fully operational next year and the island is linked by cable to the European grid in 2013.

However, in a recent visit to Malta, European Environment Commissioner Janez Potocnik said the Marsa plant had to be upgraded in line with prevailing standards or else be closed down.

“Under the Large Combustion Plants Directive, there is no mechanism for an extension to either the number of operational hours or the dates applicable,” he said.

The Commission is evaluating new information on the matter that was sent by the government on August 8. It will assess whether the interpretation of Malta regarding the definition of operational hours can be accepted.

The black dust study and executive summary can viewed on the Mepa website www.mepa.org.mt/air-publications.

ksansone@timesofmalta.com