Natural pollution – gases, dust and pollen

FOSSIL fuel burning, greenhouse gas emissions and climate change all rank highly on the agenda of today’s environmental scientists. However, we sometimes overlook nature’s own contribution to the contaminated air we breathe. Without doubt, mankind has had a tremendous impact upon the changing composition of the Earth’s atmosphere, especially since the start of the Industrial Revolution in 1750. Since accurate meteorological recordings in the late 19th century, the Global Mean Surface Temperatures have increased. The first decade of our 21st century was the warmest on record.

Certainly the cumulative increase in greenhouse gases has prevented less of the earth’s infrared night radiation from escaping into space and thus warming our atmosphere. There are, however, other forces at work and very much beyond our control, for Mother Nature also contributes to climate change in more ways than we realise.

For example, natural sources of Nitrous Oxide (N2O) are found in eruptions, on ocean beds, in biological decay, lightning, and natural forest fires. These combined sources account for between 20 and 90 million tonnes of N2O gas emissions into the atmosphere. Only 24 million tonnes per annum are released from human resources. N2O has a lifespan of 114 years and absorbs 270 times more heat per molecule than of carbon dioxide.

Some 30 years ago, the United Nations Environment Programme estimated that between 80 and up to 288 million tonnes of Sulphur Dioxide (SO2) were naturally transmitted annually from our planet into the atmosphere together with only 69 million tonnes from man-made sources.

Volcanic eruptions

For six months up until to last February, the Bardarbunga volcano in Iceland emitted 12 million tonnes of SO2, exceeding the total emission of the whole of Europe in 2011. The Laki volcanic eruption of 1783 to 1784 with its sulphurous gases caused 10,000 deaths, in fact wiping out 20 per cent of Iceland’s population. The relatively recent eruption of Iceland’s Eyjafjallajokull volcano in 2010 sent vast plumes of volcanic ash high into the atmosphere disrupting European air travel for six days.

I remember it well, as my flight from KLIA to London Heathrow (LHR) airport was diverted to Charles de Gaulle Airport in Paris and we sat on the runway there for nearly two hours before LHR was officially cleared for landing later that morning.

The height to which volcanic ash is ejected into the atmosphere is well illustrated in the photo taken by my daughter, on a recent flight from Singapore to Bali. This was of the Mount Raung eruption on Java in August. The famous and mega eruption of Krakatoa in 1883 spurted so much volcanic dust into the atmosphere that skies worldwide were darkened for several years afterwards. This month the eruption of Mount Rinjani on Bali stranded thousands of travellers as it spewed ash and smoke for miles.

Volcanoes, because of the intense heat generated by eruptions, affect the atmosphere above their localities in convection currents leading to towering cumulonimbus clouds with lightning. Lightning produces vast quantities of N2O which, if mixed with rain, allows dilute nitric acid to fall on our heads.

Desert dust

As I write this, I know that, tomorrow, my dark blue car will need a good wash. It is coated in a layer of fine sandy dust, which has been blown from the Sahara Desert on a southerly airstream over Southern England and has landed on my car in rain. For millions of years, fine dust from the Gobi Desert has been lodged in loess deposits over China, creating fertile soils and is the reason why the Yellow River was so named.

Pollen grains

Plant pollen produces yet another form of pollution to which animals and humans are subjected, although without pollination plants would not survive. As I walk my dog in grass and flower-filled meadows in summer, she will often snort and mucus comes from her nose. She formerly lived in an urban environment before we rescued her to now live deep in the countryside.

Hay fever affected many of my former colleagues in urban areas with the symptoms of runny noses, swollen eye lids, headaches and rashes. Nature takes its toll and this is the price we pay for being so close to vegetation. Even our cars today are fitted with pollen filters.

Carbon dioxide emissions

Recently, American researchers at Oregon State University with colleagues at Boston College concluded that the glacial melt at the end of the last Ice Age is attributed to rising levels of CO2 and other greenhouse gases. Their evidence suggests that that between 19,000 years BP (Before the Present) to 7,000 years BP the CO2 content of our atmosphere increased from 180 parts per million (ppm) to 280 ppm. Subsequently, over the last 265 years, since the start of the Industrial Revolution, the CO2 content in our air has leapt from 280 ppm to 400ppm.

Whilst it is a staggering leap, we must appreciate that snow fields and ice caps together with forests are the biggest natural absorbers of CO2. If forests are cut down without replanting schemes and if glaciers continue to melt, then even more naturally absorbed CO2 will riddle our atmosphere. These findings are a wake-up call to all nations.

Methane gas

This colourless and odourless gas was first identified in the late 18th century by an Italian scientist, Volta, in the marshlands adjoining Lake Maggiore in Northern Italy.

Chemists refer to this gas as CH4. It emanates from swamps, wetlands, paddy fields and from the ocean floor. It is often referred to as ‘bubbling gas’ as the bubbles burst on water surfaces.

Actually, cattle and other ruminants daily emit this gas through belching and flatulence. Termites, through the bacterial action in their guts, readily contribute to the atmosphere’s methane content. Cattle belches produce 16 per cent of the annual natural emissions of this gas. The daily output from one cow is equivalent to the daily output from a single car.

The gradual thawing of the permafrost layers in the tundra areas of Northern Canada and Siberia have seen a significant rise in methane levels there in recent years.

Whilst this gas is found in much lower concentrations in our atmosphere than CO2, it absorbs 21 times more heat per molecule than CO2 and accounts for 20 per cent of ‘the greenhouse effect’ with a 12-year lifespan, compared with the lifespan of 30 to 95 years for CO2.

It is a slight consolation to us all, to appreciate that we are not the sole contributors to atmospheric pollution and the air quality that we daily breathe.

Whilst we may glibly say, ‘Let nature take its course’, with an ever-increasing world population and more mouths to feed daily, and with forever increasing industrial development we, too, should not overlook our inputs in terms of atmospheric pollution and air quality.

As the 21st century progresses our regional climates, our environment, and indeed our own health all gradually become riskier. We can do something about anthropogenic sources of pollution even if we cannot tame nature.