Sunlight and Seaweed by Tim Flannery

Author:Tim Flannery
Language: eng
Format: epub
Publisher: The Text Publishing Company
Published: 2017-06-20T16:00:00+00:00

CHAPTER 6

The Big Clean-up

The history of Europe and the USA of the late twentieth century shows that it is possible to clean up rivers and other waters following decades—even centuries—of gross industrial pollution. It is also possible, at a small scale at least, to detoxify soils in a cost-effective manner. But something more will be needed to clean up, rapidly and cost effectively, the unprecedented diversity and scale of pollution facing us globally today. Some applications and technologies can help clean up pollution at the same time that they help grow food as well as draw CO2 out of the atmosphere. Soils illustrates the interconnected nature of the various problems we face.

Soil pollution results from many sources, is varied in its nature, and is often hidden. Cleaning up cadmium pollution offers a valuable insight into how soil pollution as a whole can be tackled. Cadmium-contaminated soils have been successfully treated in Europe and the USA. The clean-up of the 2012 London Olympics site is one famous example. Located in the city’s east end, in an old industrial area whose soils had been severely polluted for centuries by a cocktail of pollutants that reads like a guidebook to hazardous wastes, the site represented a formidable challenge. The solution settled on involved washing the soil kilogram by kilogram, then disposing of the condensed toxic fraction in a special landfill. This resulted in the removal of all major pollutants from the site—a complete remediation—which has allowed life, both human and wildlife, to thrive. Today, waterways and parklands have transformed the once-toxic dump into a vibrant and beautiful haven.

If east London’s industrial wastelands can be cleaned up, there is no doubt that the knowledge exists to clean up China’s soils. The problems, however, are cost and scale. It would take centuries to wash China’s agricultural soils kilogram by kilogram, an undertaking that would probably bankrupt the nation. So other means must be found. One time-honoured method involves simply diluting the pollution until it is reduced to safe concentrations. This can be achieved by removing most of the soil and replacing it with clean soil, or diluting polluted soils by mixing them with clean soil. But when the problem affects nearly 20 per cent of all agricultural lands, the issues of disposal and transport are overwhelming. Alternatively, pollutants can be leached from the soil using acids. But the water and chemicals containing the pollutant then need to be cleaned themselves. Soil pollutants can also be bound into larger molecules, which makes them harder for crop plants such as rice to take up, but this method is most effective where the level of contamination is low. Using electricity to convey pollutants from the soil is also being tested. In the most extreme cases, such as with plutonium contamination, or where a very deadly pollutant is at high levels or very difficult to remove, the soil itself can be sacrificed by heating it in a kiln, or using in-situ electrical-arc processes until it is melted into glass or artificial rock, thereby neutralising the pollutant but also destroying the soil.

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