We investigate gaps in our understanding of “super pollutant” black carbon, the knock-on effects on mitigation efforts, and the need for accurate monitoring.
Black carbon – light-absorbing carbon particles released during combustion – is known as a “super pollutant” because of its impacts on our health and climate. However, monitoring and policy frameworks are less developed than for other key air pollutants.
In this article, we look at three areas of black carbon research that need further characterisation. Accurate black carbon monitoring underpins all of these, and can be ensured with Aerosol Magee Scientific’s world-leading instrumentation, supplied by Cura Terrae. Read more below or get in touch with our team.
1) Better data
More data are needed in order to improve emission inventories and better model the impacts of black carbon. Emission inventories are accounts of the pollution released into the environment by specific activities or processes over time. They enable governments to understand and act on pollution levels.
However, the UK’s National Atmospheric Emissions Inventory (NAEI) assigns a 20% to 50% uncertainty range to its black carbon data. Inventory data is usually derived from calculations. For example, by multiplying the amount of pollution produced by an activity (the “emission factor”) by the amount of activity, such as quantity of fuel burned, product manufactured, or kilometres driven.
Collecting more empirical data on black carbon will improve the accuracy of the parameters used in these equations. Inventory data and direct measurements can then be used in models to simulate, understand, and predict the climate-warming or public health impacts of black carbon.
For modelling, we also need to understand how the particles change the further they travel and longer they exist in the atmosphere, as this could affect how much radiation they absorb. So-called “optical properties” are a black carbon research focus identified in a recent academic review.
Finally, better data can also contribute to the creation of black carbon metrics. Widely recognised and understood metrics are a key tool in environmental reporting, communication, target-setting, accountability, and cooperation. Often, they incentivise action. Examples include global warming potential (GWP) and global temperature potential (GTP), which have long been used by intergovernmental bodies such as the UNFCCC and IPCC. However, the Clean Air Fund writes that there is not currently a metric that fully captures the impacts of black carbon.
How is black carbon measured?
The aethalometer is the benchmark instrument for measuring black carbon and has a relatively straightforward measurement principle: air containing black carbon particles is drawn through a filter. The particles collect on the filter and, when light is shone through it, they absorb some of the light. The reduction in light reaching the detector indicates the amount of black carbon present in the sample.
As different particles absorb different wavelengths of light, aethalometers often utilise multi-wavelength technology. This can reveal the sources of the black carbon in the sample, such as traffic pollution or biomass burning (“source apportionment”). Cura Terrae now provide Aerosol Magee Scientific’s range of aethalometers, as well as instruments for total carbon analysis. View the product collection here.
2) Policy design
Currently, there are no international frameworks dedicated to black carbon. Being both a climate forcer and an ambient air pollutant, black carbon has fallen through the cracks of the global climate and air pollution agendas. To remedy this, black carbon should be incorporated into the United Nations’ climate change convention, the UNFCCC. Research is needed on how best to do this.
The Clean Air Fund recommend linking black carbon to Article 2 of the UNFCCC, which emphasises the need for rapid action on climate change. As black carbon is a short-lived pollutant, mitigation measures could contribute considerably to this aspect of the convention. Black carbon should also be included in countries’ plans to meet the goals of the Paris Agreement, which are known as Nationally Determined Contributions.
Black carbon was added to the Gothenburg Protocol in 2012, which is part of the Convention on Long Range Transboundary Pollution (LRTAP). However, it does not occupy its own specific target, instead included in targets for fine particulate matter (PM2.5). Component-specific targets are needed, as reductions in particulate matter do not necessarily lead to proportional reductions in black carbon. Monitoring particle number, not only particle mass, can facilitate this.
At a national level, there should be collaboration between ministries of health and environment, so that the issue of black carbon does not continue to suffer lack of ownership and consequent inaction. Governments should focus first on black carbon-rich sectors, such as those utilising black carbon-rich fuels, heavy vehicles, machinery, and material combustion. This includes the transport and energy industries.
Phasing out super-emitting diesel vehicles is essential and can be supported by roadside sensing to identify the worst emitters. Domestic heating, specifically wood burners, are the largest source of small particle pollution in the UK. More stringent regulations for wood-burning appliances are needed, as eco-designs may meet particulate matter standards but lead to higher relative amounts of black carbon due to different combustion conditions.
3) Regional disparities
A study published this summer found that black carbon levels in the Global South are far higher than anticipated. Comparison of model outputs with empirical observations indicate that, in some parts of the world, black carbon pollution is underestimated by an average of 38%. For some cities, such as Dhaka in Bangladesh and Adis Abba in Ethiopia, predictions were inaccurate by more than half.
A possible reason for this is that different countries are associated with different black carbon-producing activities. In the Global South, this might be brick kilns, commercial street cooking, and kerosene lamps. Consequently, data (such as emission factors) developed in high income countries and inputted into models do not accurately represent the situations of many countries.
Development of local emission factors and activity datasets is an urgent need to address black carbon pollution in many parts of the world. In addition, in the case of lack of political will or funding, the Clean Air Fund suggest a sub-national approach: taking action at the level of state or province, with sub-national agencies or departments in order to reduce black carbon emissions.
Get in touch
Accurate black carbon monitoring is critical to addressing these knowledge gaps and developing mitigation strategies that reduce the burden of black carbon pollution on communities and the environment. Cura Terrae Air has four decades of experience in air monitoring. We can provide your black carbon monitoring solution whatever your role – whether you’re an academic, policymaker, or facility manager.
Get in touch with our expert team.
Read more: Ever wondered what the difference between black carbon, particulate matter, and dust is? Find out more here.
