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Natural causes of air pollution: Wind Erosion

Wind Erosion definition

People in many areas aren’t conscious that wind erosion is a serious environmental problem and one of the most important natural causes of air pollution. There are places where this phenomenon is most likely to cause problems, especially in flat and bare areas or dry and sandy soils. However, to a greater or lesser extent, we all suffer from the air pollution this event provokes.

What is wind erosion? It is a natural process that moves soil from one location to another by wind power, often causing significant economic, health and environmental impact. At this point you might have thought about extreme cases, where a strong wind lifts a large volume of soil particulate matter into the air to create dust storms. However, light wind rolls soil particles along the surface, and this is the most common type of wind erosion.

At the end, it is wind who causes erosion, but the external facts, such as landscape or land condition, are the ones that determine the severity and the impact of this phenomenon. The following is a list of wind erosion examples:

  • Rock formation
  • Dunes
  • Canyons
  • Sand and dust storms

After wind erosion, wind deposition occurs, and it is the geological process wherein soil particles or sediments are deposited and added to the mass of landforms.

Types of wind erosion

Suspension, Saltation and Surface Creep

There are 2 types to divide wind erosion, and one of them is through suspension, saltation and surface creep:

  • Suspension: it is when particles are lifted into the wind, and once in the atmosphere, these dust and dirt particles can be transported very high through long distances, creating harmful environments for those who breath them.  
  • Saltation: it is when particles are lifted into the air, but this time they are drift horizontally. When these strike the ground again the velocity determines if they rebound back into the air or knock other particles into the air.
  • Surface Creep: in this process, the particles are rolled across the surface because wind is not too strong or the particles are too heavy to be lifted.

Deflation and Abrasion

Deflation and abrasion are another way to categorize the types of wind erosion. Deflation occurs when wind moves particles that are loose and abrasion is when an area is eroded directly by airborne particles. In other words, deflation and abrasion indicate what agent is causing the erosion.

Causes of Wind Erosion

Wind erosion occurs when something causes a reduction to the ground cover below 50% or/and removes trees and scrub that act as windbreaks. Some example are land clearing, overgrazing by livestock or cropping.

However, as the name suggests, wind is the principal cause of erosion. It can happen anywhere and any time the wind blows and it is more strong where the soil or sand is not compacted or is of a finely granulated nature.

What can prevent wind erosion?

Wind erosion prevention is topic which governments globally should focus more, as it has a huge impact on land production. The loss of nutrients affects directly the ability of the soil to properly produce drops, and soil production is one of the main elements for human race to survive. The following facts are the five main ways to prevent or control wind erosion:

Surface/crop residues

The surface form and crop residues can help prevent wind erosion. If placed at the right angle, which is perpendicular to the existing wind, it protects the removal of soil particles and maintain the nutrients of the soil.

After the harvest, when the soil is highly exposed to wind erosion, it is recommended taking any harvest residues and spread them throw the soil, so these residues act as a protection layer for the soil particles and its nutrients.

Permanent vegetation cover

A permanent vegetation cover is not only for wind erosion protection, but also for the conservation of water and air resources. This vegetation cover includes growing grass, shrubs, trees, vegetables or legumes.

Surface roughening

In large areas or areas where a permanent vegetation cover isn’t enough to protect the soil from wind erosion, three extra surface roughening methods come up: soil crusts, crosswind ridge, and clod-forming tillage.

Reshaping the land

Giving the land the ideal shape to protect it from wind erosion is key, specially on agricultural activities. It may not be available for everyone since it is a bit expensive in some cases, but it is a very effective way to lessen the potential for erosion.


It is one of the best ways to lessen the erosion of soil since the wind force finds it difficult to carry the soil particles on a wet surface. However, too much water on a soil affects negatively the soil and its nutrients, and some very hot and dry areas cannot apply this technique.

Wind Erosion as an Air Pollution Source

Appart from the economic costs, airborne particulate matter and dust are harmful to humans when inhaled. It is highly recommended having a dust mask if you live in an area where dust storms are common.

Airborne dust is directly related to the probability of asthma and other health problems. You can refer to our blog post on health effects of air pollution to know everything about it.

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Natural causes of air pollution: Volcanic Eruptions

Volcanic Eruption Definition

A volcano is an open fissure on the surface of the earth. Active volcanoes are those from which lava, volcanic ashes, rocks, dust and gas compounds escape on a regular basis (10.000 years are considered regular with volcanoes, so you can feel safe if you have one around) due to the phenomenon of volcanic eruptions.

In the world there are several active volcanoes which cause air pollution, danger to life forms and massive destruction of the land and the environment. Indonesia is the country with most active volcanoes in the world with 76 of them and total of 147 volcanoes.

Causes of Volcanic Eruptions

There are many causes that can lead to a volcanic emissions, many of them are still unknown by humans, which volcano eruptions very hard to predict. However, volcanologists have made some researchers to determine a few catalysts of them:

  • Movement of tectonic plates: whether it is because one is pushed under another one or two tectonic plates are moved away from each other, this creates a massive movement on the layers of planet earth (changing the structures of magma, sediments and seawater) and cause a volcano to erupt.
  • Decreasing temperatures: the volume of magma changes when it crystalizes, so it can push away liquid magma and create a volcanic eruption.
  • Decrease in external pressure: this fact provokes an increase in the internal pressure of the volcano and causes and eruption if it is not capable of holding back the lava.
  • Buoyancy of the magma: if the density of the magma between the zone of its generation and the surface is less than that of the surrounding and overlying rocks, the magma reaches the surface and erupts.
  • Pressure from the exsolved gases: andesitic and rhyolitic magma compositions contain dissolved volatiles (gases) such as water, sulfur dioxide and carbon dioxide. This gas bubbles are held by magma, but just like a carbonated drink, the bubbles of gas rise to the surface of the magma chamber creating a volcanic eruption.
  • Injection of a new batch of magma into an already filled magma chamber: this phenomenon causes some magma to move up and spill or even erupt at the surface.

Effects of Volcanic Eruptions

Volcanoes have huge impact on our society and environment when they erupt, here there are some of the many positive and negative effects of volcanic eruptions:

  • Negative effects: volcanic eruptions, which sometimes generate earthquakes, can destroy landscapes, natural resources, wildlife and human lives and their properties. This phenomenon can also discharge ashes very high into the atmosphere, having negative consequences on the ozone layer. Moreover, ash and mud can mix with rain and melting snow and create situations like lahars (also called mudflows) or acid rain. In other words, volcanic eruptions can destroy civilizations, like what happened to Pompeii.

  • Positive Effects: sometimes eruptions can leave an extraordinary beautiful and natural scenery, attacking tourists to the area. However, one of the most useful positive effects is that they often leave potential for geothermal energy, making life more easy for those around the area. Finally, some volcanic eruptions provide valuable nutrients for the soil, which are later used as fertile soils for agriculture.

Types of Volcanic Eruptions

Air Pollution of Volcanic Eruptions

Volcanic Eruptions release massive quantities of solid pollutants and gases, forming enormous clouds that can affect areas miles away from the volcanic eruption. Therefore, volcanoes are an international form of air pollution, but not just for us, as a lot of this greenhouse gases and aerosols go directly into the atmosphere.

Every volcanic eruption is different on impact, and therefore different on the quantity and a variety of pollutants emitted. On average the outgassed composition release is 79% water vapor (H2O), 11,6% carbon dioxide (CO2), 6,5% sulphur dioxide (SO2) and 2,9% of other pollutants.

However, the range of pollutants released on a volcanic eruption include: carbon dioxide (CO2), sulphur dioxide (SO2), hydrogen sulfide (H₂S), hydrogen (H₂), hydrogen fluoride (HF), hydrogen chloride (HCl), bromide oxide (BrO) and carbon monoxide (CO). Highly exposure to these gases has detrimental impact on living organisms both terrestrial and marine.

On the other side, particulates are another source of air pollution produced by volcanic eruptions. Mainly ashes and including all types of sizes, the ones that help forming toxic clouds are usually PM10, PM2.5, PM0.3 and thinner.

These pollution clouds can travel major distances, like crossing oceans, dangerously affecting people and environments who didn’t even notice the eruption. If you are facing a polluted cloud caused by a volcanic eruption, you may want to have a look at the following content on what to do and how to prevent these events.

What to do before, during and after a Volcanic Eruption

Before a Volcanic Eruption

There are several precautions you have to take into account before a volcanic eruption, and it is good to discuss them with your family members (including kids) before the event to prevent nerves and panic.

The first step is to have a household evacuation plan (that includes your pets). If you need guidance creating one you can find all you need to know and some templates here.

Secondly, as during the volcanic eruption you might lose electric supply, you need to have a flashlight, a battery radio and extra batteries for both. It is important to keep yourself up to date. We will write about it below, but during the previous days stay informed about the governmental media, community’s risk and response plans.

Thirdly, you will need health protection to ashfall and air pollution. To protect your eyes it is recommended having a pair of goggles, and to protect your respiratory system you should buy industrial protection face masks. Note that the majority of common pollution masks are not valid, you should have one approved for industrial and extreme purposes.

Finally, as any scenery is possible, you need to be prepared to live indoors for long periods without electricity power nor drinking water so buy food (if possible durable goods) and bottled water to survive you and your family members a few weeks. Make sure to have all the outdoor stuff and you want to keep safe inside, volcanic eruptions can damage any furniture, machinery or material.

During a Volcanic Eruption

If your outdoors you should quickly look for a shelter indoors. If it is not possible stay out of designated restricted zones, areas downwind of the volcano and river valleys downstream of the volcano. Take into account that even if you are miles away from the eruption you can experience harmful consequences.

In the case you get caught by an ashfall wear goggles (never contact lenses), a dust mask prepared for industrial and extreme purposes and a keep as much of your skin covered as possible.

On the other hand, if you are indoors you should be constantly listening to a local station on the battery radio for updated emergency information and instructions. It important because your area can be at any moment evacuated. During the indoor period, make sure to close all window, doors, and dampers to keep volcanic ash from entering.

In case of evacuation, strictly follow the instructions issued by local or national authorities and put your previously studied household evacuation plan. This rule is the most important one because even though it may look safer to stay home, take into account that your life must be in danger.

After a Volcanic Eruption

If you pass a volcanic eruption you will surely never forget it. There are some tips you should take into account to return to normality as soon as possible.

Firstly, you should not stop listening to local news for authorities updates, if you were evacuated, don’t return home until the authorities say to do so because it is safe. If people around you are injured, check the zone is safe for you and then call an ambulance and provide first aid (if you know something about it). Your family and friends might be worried as well, so tell everyone you are safe.

Secondly, even though the eruption has passed, if possible stay indoors and use the pollution mask (indoors and outdoors), because pollution particles (mainly ashes) will still be floating in the environment, and these can be extremely harmful. Moreover, keep animals away from ashes and wash them to prevent them from eating ashes.

Emotional recovery can be difficult because you may see some astonishing images and receive some terrible news. Here is a link to help you with this recovery.

If you have to return home try not to drive on heavy ashes roads because these are extremely harmful not just to humans health, but also to car engines. Never stop wearing any of the protective clothes, you cannot allow to expose yourself even for 30 seconds.

Once you get there, take pictures of the damages caused by the volcano for insurance purposes. The next step is to start cleaning your house from ashes and other volcanic materia, starting by the roof and gutters, which can cause your house to collapse. To help you with this task, read the following link for proper guidance.

Last Volcanic Eruption

Here comes an interesting fact about volcanic eruptions: any time there are several volcanoes on an eruption process. Volcanic activity is much more powerful and regular than we usually think. To know what volcanoes are erupting today, click the following link.

Largest Volcanic Eruption

World’s history has seen some supervolcano eruptions, often called big bangs on the earth, and science explains that these major catastrophes occurred before human life was born.

However, during humans history there has been some major eruptions as well, and since 1980 we have been measuring their impact throw the VEI (Volcanic Explosivity Index) indicator. VEI is measured just like earthquakes, on a scale from 1 to 8, and each number is ten times greater than the previous one.

In the last 10.000 years there haven’t been any VEI-8 volcanic eruptions, luckily for us, but on the following list we name some of the most recent major volcanic eruptions:

  • Tambora – April 10, 1815
  • Krakatoa – August 27, 1883
  • Santa María – October 25, 1902
  • Novarupta – June 6, 1912
  • Pinatubo – June 15, 1991
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Natural causes of air pollution: Radon Emissions

What is radon?

Radon (which has the symbol Rn and its atomic number is 86) is a chemical element belonging to noble gases, very radioactive, colorless, odorless and tasteless. This is the reason why radon is also called invisible gas or “the silent killer”. In solid form it is reddish. It is the earth’s only naturally produced radioactive gas and comes from the breakdown of radium, uranium in soil, rock, and water.

This air pollutant is highly radioactive in nature, and it can cause some serious health damages to people who breathe it. In fact, it is the second largest contributing factor to lung cancer in human beings after smoking. It causes an estimated 1,100 deaths from lung cancer every year.

Because the level of radioactivity is directly related to the number and type of radioactive atoms present, radon and all other radioactive atoms are measured in picocuries.

Radon decay

Radon is diffused out of the air all the time in variable quantities depending on the pressure drop. Such pressure drops can accompany or precede the shearing of rocks in an earthquake. It disperses and decays very quickly, with a half-life of 3.8 days.

Radon decay products (RDPs) such as polonium (218), lead (214) and bismuth (214) are measured in working levels (WL).

Radon at home

Why do some houses have high levels of indoor radon while nearby houses do not? The reasons lie primarily in the geology of radon, the factors that govern the occurrence of uranium, the formation of radon and the movement of radon, soil gas, and groundwater.

It can seep into buildings through cracks and holes in its foundations, where it can build up to dangerous levels. In Britain in 2018, the number of homes designated at risk was increased five-fold (from 100,000 to between 500,000 and 600,000), rendering millions more people officially vulnerable.

If you smoke or someone at home smokes, your family is exposed to radon, and therefore probabilities of lung cancer increase. Moreover, the only thing you can do to eradicate this type of gas is quit, and any time is good to reduce its exposure.

Due to health risks of radon exposure, it is recommended testing radon concentration before buying a house or while building it. However, if you want to analyze indoor air quality of your current home there are easy and fast techniques to test radon emissions by your own, for example with charcoal or digital tests.

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Natural causes of air pollution: Methane Emissions

Methane is an odorless, colorless greenhouse gas with the chemical formula of CH4. It is mainly used as a component of natural gas.

Natural sources create 36% of global methane emissions, long before humans existed there has been methane emissions into the atmosphere. However, methane expulsion is mainly man-made, in activities such as landfills and livestock farming. As a fact, it may seem interesting to know that daily methane emissions from cows (through belching and flatulence) and from cars are pretty similar.

It can lead to severe asphyxiation if someone is highly exposed to methane gas in the air. Building construction must take into account this factor, since the presence of methane in the airways of the building can lead to dire consequences.

Methane levels have more than doubled over the last 150 years. This is because of human activities like fossil fuel use and intensive farming. Before the Industrial Revolution, natural sinks kept methane levels in a safe range.

Methane is twenty times more powerful greenhouse gas than carbon dioxide when released into the ozone layer. It is also highly inflammable when it combines with other elements in the air and it massively contributes to global warming. Bellow you will find the main natural sources of methane.


A wetland is a distinct ecosystem that is inundated by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other landforms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play numerous roles in the environment, principally water purification, flood control, carbon sink and shoreline stability.

Wetlands are the largest natural source of methane producing 78% of natural methane emissions. Microbes need environments with no oxygen and abundant organic matter, thus wetlands are perfect for them to be born.

Wetlands are estimated create 147 million tonnes of methane each year. Part of these emissions are absorbed by methane-consuming microbes. However, the majority of these emissions are released into the atmosphere and the ozone layer.


Termites are eusocial insects that you probably know due to they can break into your house and destroy all the wood structures. However, do you know these little insects produce large amounts of methane?

Termites eat cellulose, but rely on micro-organisms in their gut to digest it. During the normal digestion process of a termite, methane gets produced.

At this point you are probably thinking: no way, this tiny insect cannot produce amount of methane I should worry about. You are right if you have just one termite, but if you take into account the total population of termites numbers add up.

Termites produce 12% of natural methane emissions, being a total of 23 million tonnes of methane per year. Surprising right? If you have termite infestation at home, be aware that you and your family can be highly exposed to methane.


Everyone knows what an ocean is, but almost nobody knows these are a major natural source of methane. In fact, oceans don’t produce itself methane, but these are the perfect environment for microbes to live and emit this type of pollution gas.

According to scientists from the University of Illinois and Institute for Genomic Biology, the ocean-based microbe Nitrosopumilus maritimus produces methane through a complex biochemical process the researchers referred to as “weird chemistry.”

Oceanic methane emissions often gets produced in deeper sediment layers of productive coastal areas. The methane created by these microbes mixes with the surrounding water. After some time in the water, it gets emitted to the atmosphere from the ocean surface.

At the end oceanic methane emissions are 10% of natural methane emissions and 19 million tonnes of methane per year.

Arctic’s methane issue

It is estimated that there are billions of cubic metres of natural methane gas trapped underneath huge areas of permafrost in Siberia, and under the frozen wastes of the Arctic. When methane is enclosed in frozen water it is called methane hydrate.

The Arctic has warmed more quickly than any other area of the planet. As the ice has melted, naturally formed methane gas, which would otherwise be trapped under the ice, is bubbling to the surface.

Currently, there are thousands of sites in the Arctic where methane gas is being released into the atmosphere and it could have serious ramifications for global warming.

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Natural causes of air pollution: Forest Fire

What are Forest Fires?

Forest fire originated by natural causes, or in other words without human activity involved, are also known as bushfires or wildfires. These are given when fire has place in highly dense vegetation areas.

Furthermore, bushfires also contribute to deforestation, what indirectly affects air quality in forests and jungles, that are considered Earth’s lungs.

Australia is well known as a country with plenty of vegetation and wildlife. However, the country has an important issue with bushfires, as they cost more than £180 million each year (both natural and man-made).

Unfortunately, there are a huge amount of notable bushfires in history. Some examples of most important wildfires worldwide have been:

  • China (1987) burning over 72.000km2 and Indonesia (1997) burning over 97.000km2.
  • Currently the U.S. and Canada have been the most active countries last 10 years with bushfires burning around 6.6 and 6.2 acres/year respectively.

A long time ago, palaeowildfires burnt plant material leading to fossil charcoal formation. Nowadays, fossil charcoal is being used as an indicator of palaeoclimatology in order to study evolution on bushfires over the years.

Causes of Bushfires

There are several different causes that lead to forest fire, but these are made more likely when the weather is hot and dry. Fallen leaves, dry grass or branches easily light up and can cause serious trouble to both urban and rural areas.

These terrible events often pass in just a few minutes, but they can last days, or in very unfortunate situations even months. The real threat when it comes to bushfires are high winds because these fan the flames and spread the blaze.

Forest Fire Pollution

Forest fire release pollutants like smoke, sulphur dioxide, nitrogen dioxide, ozone, particulate matter and carbon monoxide into the atmosphere. The bigger the bushfire, the bigger emissions.

In small amounts, carbon monoxide is present human bodies. The problem is that when inhaled in large amounts, and large amount of this gas are emitted on bushfires, it becomes toxic and can cause death.

Particulates on forest fire are either solid or liquid and consist of soot, tars, and other volatile organic substances. These particles can have different sizes: PM10, PM2.5, PM0.3 and smaller. They can cause cardiovascular and respiratory problems if they penetrate deeply into humans lungs.

Nitrogen oxides and sulphur dioxides are minor problems when it comes to forest fire. Nitrogen oxides are only released in big bushfires, as they only appear at greater temperatures than 1,500 degree centigrade. On the other hand, except when peat and muck soil are involved, sulphur dioxide only appears to be less than 0,2%.

Health effects of wildfires

Wildfire in California during the summer 2018 caused hazardous air conditions across the state, prompting air quality alerts and forcing many residents to take refuge indoors to avoid unhealthy exposure to bad air.

It is not just about foggy and hazy skies, human’ risks and exposure are real. The air pollution from wildfires includes huge percentage of particles PM10, PM2.5, PM0.3 and thinner. Therefore, the health effects of wildfires are very similar to the ones explained during the blog post about Particulate Matter.

These health effects of forest fires include coughing, sore throats, extreme wheezing, cardiovascular illnesses and problems into lungs and bloodstream. Of course, sensible groups like children or elderly, are more likely to acquire these symptoms.

However, what do you have to do in the event of a forest fire? Firstly, you should be worried about the dangers of wildfires, so stay tuned to a local station for recommendations. Additionally, to protect yourself from air pollution: wear some kind of pollution mask, avoid staying outdoors and close all the opening from your house to prevent air pollution to enter. Finally, avoiding riding cars will help reduce SMOG, as this is produced with the mixing of combustion gases and the air pollution produced in forest fires.