Remediation of soils polluted with inorganic contaminants: Role of organic amendments

Abstract

The use of amendments made with organic wastes for remediating degraded and polluted soils has shown to be an effective and low-cost treatment to increase soil quality. This improvement in soil quality is reflected in fertility levels, physical and biological quality of the soil, allowing and supporting vegetal covering of previously degraded areas. The addition of organic amendments in polluted soils is considered one of the most promising recovery techniques at present. This is because organic amendment makes use of waste which would in most cases be unutilized for any activities and cause other damage to the environment. Organic amendments, such as biochar, Technosols, sewage sludge and compost, seek to convert waste into environmental benefits at low cost. The use of these techniques accelerates processes such as sorption, precipitation and the formation of complexes that are produced naturally in the soils and which reduce the mobility and bioavailability of pollutants; additionally, its application may stimulate the microorganism development that acts in degradation of both organic and inorganic pollutants. Despite these benefits, the use of wastes as soil amendments has been questioned, as some of them contain high metal concentrations that aggravate the contamination of the degraded soils. Nevertheless, some studies have shown that most of the metals added to soils with the use of waste amendments are in the unavailable form for plants and that when managed properly, applied in appropriate concentrations or mixed treatments, can result in even greater benefits than previously analysed.