It has recently been reported that air quality around Marsa has improved significantly particularly with regards to sulphur oxide emissions, a notable decrease for which has been registered.
This success has been attributed, almost logically, to the definitive closure of the Marsa power station in the wake of the much-awaited developments in the power generation sector. Marsa has been replaced entirely by the works of the submerged interconnector cable that now links Malta’s power grid with the Sicilian mainland.
In the meantime the new natural gas-fired power plant is nearing completion and cleaner air should also be registered in the Marsaxlokk environs by when the shift away from heavy fuel oil shall at long last be complete.
The time shall soon be over when the Marsa and Delimara power generation facilities could conveniently be blamed for reduced air quality in the urban south. Back then, especially when Marsa still relied on coal combustion until the mid-1990s, the black dust inconvenience only served to mask a more serious malaise: that of the black particles themselves, carbonaceous soot by their very own nature, serving as surfaces for chemical reaction between other pollutants leading to the formation of potentially even more harmful secondary pollutant species.
One particular study in the early 1990s had clearly linked emissions from the Marsa plant to the deposition of sulphate on limestone surfaces of buildings in localities surrounding the plant. Another study focusing mainly on the nature of particulate emissions from heavy fuel oil combustion had shown that the relatively high content of the heavy metals nickel and vanadium in particulate matter in ambient air could easily be traced, in almost fingerprint fashion, to furnaces burning the HFO at elevated temperatures comparable to that of power stations.
The presence of nickel and vanadium in these particulates, fine enough to be inhaled and possibly exposing residents to health problems due to prolonged exposure – practically on a daily basis – would be enough to catalyse a host chemical reactions in ambient air increasing the toxicity of the atmospheric broth that surrounds us.
It is a well-known fact in empirical chemical science that metal surfaces provide ideal niches where chemical reactions can proceed at a much faster rate, facilitated by the typically warm and humid climate that characterises the Maltese environment.
One of my most salient moments used to be in the early morning on very cold wintry days when I used to enjoy a pensive stroll in the streets of Mdina and, looking down south while taking a breath of chilly cold air on the bastions, I used to glimpse at the brown haze engulfing Marsa, Paola, Fgura and the surrounding areas.
That was – and still is – not just particulate matter from the power station. It is a concoction of noxious pollutant gases including nitrogen oxides, technically referred to as NOx, that are released from both heavy fuel oil combustion when the Marsa plant was still active and also petrol and diesel engines in vehicles.
Weather conditions play a crucial part in the air pollution story: very cold nights with stagnant air only make it worse on the following morning as a result of the temperature inversion that makes it virtually impossible for the pollutants to disperse and hence, though not much of a consolation, to be diluted in the bigger air volumes beyond the street canyons we drive ourselves through, hectically, at every single break of dawn.
An understanding of air pollution chemistry is essential to appreciate the extent to which transport in Malta needs to be urgently addressed
As the sun rises and the air gradually heats up turbulence sets in and it slowly becomes more possible for the pollutants to disperse but, simultaneously, the sunlight activates the pollutant particles to react even more triggering an immensely complex mechanism of chemical processes that yield toxic substances like tropospheric ozone, hydrogen peroxide, formaldehyde and peroxyacetylnitrates. Each time we set foot on a petrol station and smell the heavy odours of hydrocarbons, reminiscent of kerosene, we should recall that the fugitive emissions are all so-called volatile organic compounds (VOCs) that rise into the air while petrol and diesel are being fed into car fuel tanks.
The fact that most petrol stations are sited in densely populated urban areas on main roads certainly does not help but, admittedly, there is no easy solution to what practically is an inevitable situation that has been evolving over many years.
A very recent study by the UK Air Quality Expert Group (UK AQEG) to the Department for Environment, Food and Rural Affairs, the Scottish and Welsh governments, and the Department of the Environment in Northern Ireland has focused on the effectiveness of photocatalytic paints containing titanium dioxide, TiO2, to reduce air pollution.
Photocatalytic paints are sensitive to sunlight, particularly ultraviolet wavelengths, such that upon exposure their TiO2 content renders itself an ideal surface over which pollutants such NOx can be destroyed by conversion, chemically, into other airborne species. The study focused on the ability of passive surfaces coated with this special type of paint to curb what has long emerged into not just a national cause for concern in most countries, industrial and otherwise and including ours, but also tantamount to a scourge across Europe as transport emissions remain steadily on the rise.
In all of this, the economic dimension cannot be ignored. A 2015 study by Maria Attard, Philip Von Brockdorff and Frank Bezzina of the University of Malta has revealed that locally the external costs of transport for 2012 can be estimated at €274 million in accidents, air pollution, climate change, noise and congestion, the estimates being estimated to rise to €317 million by 2020 and €322 million by 2030 under a ‘no policy change’ scenario. In all years air pollution and climate change costs made up a substantial portion of the estimate.
The study by the UK AQEG concluded that in spite of all the initial investment in the research and optimism, resorting to photocatalytic paints does not really serve much to obliterate the air pollution problem arising from NOx emissions in ambient air. Whereas indeed NOx would tend to react and be destroyed over the photo-activated TiO2 rich surface such as glass or stone-walls, the effect would be too localised to exert an overall positive effect on a broader scale given the dissipation of pollution across large air volumes.
The UK AQEG further concluded that even though TiO2 based paints can indeed act as surfaces over which NOx pollution is chemically destroyed, this effect easily yields undesirable consequences just as well, not least due to the formation of formaldehyde and other toxic pollutants from NOx and VOC interactions. The initial thought that perhaps the application of photovoltaic paints across buildings and roads in urban areas could provide an effective remedy to the vehicular emissions problem thus dissipates in thin air.
An understanding of air pollution chemistry is essential to appreciate the extent to which transport issues not just in Malta but anywhere else need to be urgently addressed. The worst approach to the challenge that lies ahead to address transport issues would be unconstructive political blame-gaming in the hope that one political party scores brownie points at the expense of the other.
From a purely environmental health perspective there has never been an instance, perhaps, where the political maturity of so few was so direly needed to safeguard the interests of so many.
sapulis@gmail.com
Alan Pulis specialises in environmental management.