Lasers and the environment

Climate change is one of our most immediate challenges. Deforestation and the burning of fossil fuels are the likely causes for the increased concentrations of greenhouse gases in the Earth’s atmosphere.

Lasers can be used to analyse the concentrations of these gases and even to monitor their effects on ecosystems.

Lasers to monitor and understand climate change

Climate change and poor air quality are major challenges in a world of increasing industrialisation and urbanisation. Understanding and monitoring the Earth’s atmosphere is of crucial importance.

Observing the atmosphere from space can provide a global view of atmospheric composition and processes. An innovative research project, funded by the Natural Environment Research Council, called the Laser Heterodyne Radiometer (LHR) has involved the development of a prototype instrument that could potentially be the forerunner of a new generation of satellite-based infrared monitoring instruments. The LHR has been developed to provide a unique combination of high spatial resolution (to locate gaseous emission sources and observe between clouds), high spectral resolution (to discriminate between types of gases), and high sensitivity to detect the tiniest concentrations of atmospheric constituents.

Developed for Earth observation by a team of STFC scientists in collaboration with partners, a prototype LHR instrument has recently been successfully demonstrated at ‘the Rutherford Appleton Laboratory’ through ground-based measurements of atmospheric ozone, and is now being developed to monitor other key atmospheric trace gases.

 

Global cooling

Clouds are considered to have a substantial impact on climate change because of their role in both absorbing and reflecting heat transferred through the atmosphere.

Pollutants such as the organic compounds produced when fossil fuels are burnt, are believed to affect the formation and growth of water droplets in clouds.

Scientists working at STFC have been able to gain an insight into chemical reactions occurring on the surfaces of cloud droplets in the atmosphere. Typical experiments involve spraying a mist of particles into a model ‘cloud chamber’ and using a microscope to focus a laser beam into it. One of the droplets eventually finds its way into the centre of the laser beam and is held in position via the intense light-field pressure of the laser, which acts like ‘optical tweezers’. Analysis of laser light scattered by the droplet underpins the development of complex computer models of the atmosphere and contributes to improving our understanding of climate change.

 

Monitoring forests with lasers

Important properties of ecosystems such as those found in tropical forests can be measured using a system of lasers attached to the underside of aircraft. Often covered with dense vegetation, these forests tend to be difficult to study on the ground or even with satellites.

A combination of advanced spectroscopic imaging and laser remote-sensing technologies can measure differences in ground elevation to an accuracy of within a few inches. This technology can provide insights into how changes in climate and land use can affect the structure, composition and functioning of ecosystems.

 

Using lasers to tackle oil spills

Oil spills represent a major environmental risk, often taking many years to clean up. But, for some bacteria, oil is the perfect meal! By introducing colonies of hydrocarbon-digesting bacteria, it may be possible to lessen the impact of oil spills and clean them more efficiently.

Researchers at STFC’s ‘Lasers for Science Facility’, in collaboration with scientists from the Centre for Ecology and Hydrology, have been assessing the different types of bacteria that can digest hydrocarbons. By capturing individual bacteria in laser optical tweezers and analysing their spectra, scientists can establish whether the bacteria have broken down particular chemicals.

Potential future applications of this research range from cleaning oil spills at sea, to the contaminated land under petrol stations.

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