Sustainable remediation of mercury contaminated soils by thermal desorption

Abstract

Mercury soil contamination is an important environmental problem that needs the development of sustainable and efficient decontamination strategies. This work is

focused on the application of a remediation technique that

maintains soil ecological and environmental services to the

extent possible as well as search for alternative sustainable

land uses. Controlled thermal desorption using a solar furnace at pilot scale was applied to different types of soils,

stablishing the temperature necessary to assure the functionality of these soils and avoid the Hg exchange to the other

environmental compartments. Soil mercury content evolution (total, soluble, and exchangeable) as temperature increases and induced changes in selected soil quality indicators are studied and assessed. On total Hg, the temperature at

which it is reduced until acceptable levels depends on the

intended soil use and on how restrictive are the regulations.

For commercial, residential, or industrial uses, soil samples

should be heated to temperatures higher than 280 °C, at

which more than 80 % of the total Hg is released, reaching

the established legal total Hg level and avoiding eventual

risks derived from high available Hg concentrations. For

agricultural use or soil natural preservation, conversely,

maintenance of acceptable levels of soil quality limit heating

temperatures, and additional treatments must be considered

to reduce available Hg. Besides total Hg concentration in

soils, available Hg should be considered to make final decisions on remediation treatments and potential future uses.