To most people the impact of black carbon is limited to the dangers of the particulate matter from diesel cars on human health, this is because it is heavily talked about in the media since the Volkswagen emissions scandal hit in 2015. I will talk more about this and the problems of diesel cars and why many cities want to now ban them in a later blog.
In this blog I want to explain how black carbon can be a valuable source of primary evidence for our past and could hold the key date the start of the Anthropocene Epoch.
What is the Anthropocene ?
The present day is referred to as the Holocene Epoch, many academics believe it should be referred to as the Anthropocene Epoch. This because there is evidence that human activity has influenced global environmental change during this period and the phenomenon is not a natural one. No formal start date is agreed for when the Anthropocene Epoch should begin. There is strong support for AD 1950 as it relates to the great acceleration of fossil fuels being burnt leading to a huge increase in global CO2 levels.
What are some of these particles that black carbon incorporates and can it hold the key to providing clear evidence for the Anthropocene ?
The term Black carbon (BC) refers to a wide array of substance cause by the incomplete burning of fossil fuels which can contain larger particles and smaller ones such a soot. There is no single definition, which means BC incorporates a wide variety of particles produced.
Fly- ash particles are produced from the burning fossil fuels, such as coal for electricity generation. The ash that is created is collected from the power plants and dumped into landfills.
There are two types of particles produced in fly-ash,
1) Inorganic ash spheres which originate from materials that cannot burn, present in fuels
2) Spheroidal carbonaceous particles (SCP), a clear component of black carbon. Below in Fig 1 is a photo of what it looks like.
SCP are produced at high temperatures of more then 1000 °C from coal and oil, an important note is there are no known natural sources that produce SCP. The more fossil fuels burnt, the more these black carbon balls SCP are released into the atmosphere.
Fig 1:Spheroidal carbonaceous particles (SCP) Source: Rose N (2015)
Why is Spheroidal Carbonaceous Fly ash particles useful for looking at the past ?
SCP are found in every part of the world in every sediment even very remote areas.They are well preserved such as in ice and lake deposits, providing a clear marker of anthropogenic fossil fuel use by humans. They are normally found in large concentrations in lakes where acid levels are high and this matches acidification trends.
Key benefits
- Large amounts of data can be extracted from sediments
- Sediments continually build up black carbon
- Very Reliable
- Long Chronologies
Rose N (2015).
They provide a clear advantage compared to other markers to show the effects that humans have had on the environment.
BC deposits can be clearly seen in the photo of the peat core in Figure 2, look towards the top, notice how it turns black, these are black carbon deposits from the atmosphere. Examples like this can be found all over the world even in remote locations with no known sources of pollution.
Figure 2: Source
What do Spheroidal Carbonaceous Fly-ash (SCP) particles tell us ?
In Neil Rose's 2015 study in which SCP data was collected from over 75 lakes sediments around the world. The data shows that
- Levels of SCP start to increase rapidly around the 1950 mark, as represented in figure 3.
- Caused by large demand for power and the introduction of cheap fuel oil and its combustion after the Second World War.
- Levels increase on a global scale.
- Shift in deposits - when SCP deposits start to reduce in Europe and North America in the 1970s. In Asia and North Africa levels are increasing, representing a shift in the geography of industrialisation.
- This region started to require more energy and power and used dirty cheap fuels like coal for rapid development, as production of goods were shifted from the West to countries where it was cheaper to produce like China.
Figure 3, SCP levels from sediments. Source Rose N (2015)
Swindles et al (2015) paper is a compilation of SCP results data from all around the world in which he condensed the trends into one graph, which is represented in figure 4. The graph clearly shows the rapid increase in the mid 20th century which links to the great acceleration in fossil fuel use during this period.
The data provides compelling evidence that black carbon can be one of the best primary markers which providing clear evidence of this new human epoch called the Anthropocene starting around the 1950's.
Figure 4, SCP levels in sediments from around the world. Source Swindles, G. T. et al (2015)
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