From hypotheses to real solutions

The issue of the emergence of black dust in the Fgura area is of concern to the Malta Environment and Planning Authority. Indeed, Mepa has been closely monitoring the situation, carrying out studies and addressing the concerns raised by the community.

The first appearance of this black dust incident goes back to 1999 and it was the then Ministry for the Environment that commissioned a report - now known as the Stacey Report - which analysed samples of the dust and attempted to define its origin. The Stacey Report had failed to make a comparison between the black dust samples and "fly ash" residues.

The conclusion of the report was that since the Fgura "fall out" samples are similar in appearance to "fly ash" commonly emitted by power stations and since trace amounts of vanadium and nickel were detected in these samples, then, the Marsa power station was indicated as the possible source of these particles.

In 2000, Enemalta proceeded to install electrostatic precipitators - in other words, equipment that reduces dust emission from boilers - and, in April 2004, changed the fuel used to one containing just one per cent sulphur in order to conform to EU standards on emission limit values for sulphur dioxide and fine dust. In fact, from the year 2000 onwards, no other occurrence of the black dust was recorded until 2007, when Mepa received fresh reports of incidents of this black dust falling in the same area.

Considering the lapse of time and the various new circumstances, which included the precipitators mentioned earlier, and the change in type of fuel used, Mepa decided to embark on a new investigation.

Samples were collected by the residents themselves. At the same time, Mepa officials collected "fly ash" samples from a boiler at the power station, grit samples from ship maintenance activities at Malta Shipyards and a soot sample from the engine of a diesel vehicle, in order to be able to make a proper comparison.

The study concluded that the "fly-ash" from the power station was made up of cenospheres, in simple terms, black particles generated by the combustion of fuel oil and which included vanadium, nickel, silicon, magnesium and sulphur.

The "fall out" samples collected by residents were also made up of black cenospheres but no nickel or vanadium was detected in these samples.

In layman's terms, nickel and vanadium are characteristic trace constituents of heavy fuel oil whereas magnesium is a constituent of a fuel additive in use at Marsa power station. This means that had these three elements - as well as sulphur - been present in the black dust samples collected by the residents, it would have been definitively confirmed that the Marsa power station was the likely source of this nuisance.

The absence of these elements meant that Mepa had no hard scientific evidence in favour of the hypothesis that the power station was the likely source.

Moreover, this analysis excluded that either Malta Shipyards or diesel engines were the source of this nuisance. As a result, it was decided that further analyses are carried out and to collect further samples. However, the problem again subsided.

In August 2009, Mepa received another set of complaints regarding fall out dust - yet again in the same areas - and Mepa opted to collect samples from the power station and from four residences in Fgura and send the samples abroad for characterisation. The samplers were installed on August 28 this year.

To make a proper analysis, the sample needs to contain 10g of dust collected. However, the problem again subsided and, as a result, to date the amount of dust collected in the samples has not yet reached anywhere near the quantity necessary to conduct proper tests. The moment the quantity of dust collected reaches the established amounts, the samples will be sent for further analysis.

Besides collecting the new samples from around the locality in Fgura, the planning authority is mapping the complaints from Fgura in order to investigate the possibility of there being a localised source of pollution. Mepa is committed to ensure that the source of this "nuisance" dust is identified and mitigated.

It must also be pointed out that monitoring data from Mepa's nearest monitoring station at Corradino clearly indicates that the ambient values for various pollutants, including PM10 (fine dust), in the area are well within the limit values set by the EU Air Quality Directive. However, one must keep in mind that this directive sets levels for very fine dust (less than 10 micrometres) as this is the fraction of most concern to human health. The dust typically seen by the human eye is far coarser (typically 70 to 300 micrometres) and does not have the same potential to lodge in the lungs or enter the bloodstream.

Mepa remains committed to finding a definitive and permanent solution to this issue. Over these past years it has introduced significant pollution control measures. Among these are the imposition of strict environmental permits and monitoring regimes on the Marsa power station and the Marsa thermal treatment facility as well as ongoing actions to enforce environmental permits on scrapyards and other facilities in the area.

While residents are understandably frustrated and concerned that no definitive solution has as yet been found to the occasional recurrence of this problem, Mepa's aim remains to find a definitive answer and it will continue with its efforts to provide real solutions and not conjectures and theories.

The author is Mepa director for environment protection.