The Sorption Behavior and Bioavailability of Persistent Organic Pollutants (POPs) in Soils

Persistent organic pollutants (POPs) pose a threat to the environment because of their potential for long-range atmospheric transport, bioaccumulation and toxicity. The POPs behave dynamically in the environment according to their different processes e. g. volatilization, sorption, desorption and transportation. Environmental variables like temperature, soil pH and moisture have serious effects on POPs behavior in soil. Organic as well as inorganic compounds may react with the xenobiotics and play an important role in their transformation in soil. Manganese and iron oxides and clay minerals (e. g. smectites containing Fe(III)) had well-documented properties to promote the oxidation of a number of organic pollutants. Organic matter is considered the most important factor limiting the availability and mobility of POPs in soil and a substantial percentage of the organic contaminants applied to a soil might become associated with soil humic fraction. Organic pollutants strongly adsorbed to carbonaceous sorbents such as black carbon. In particular, activated charcoal (AC) had a strong adsorptive capacity due to its high specific surface area. Adsorption to activated charcoal could render hazardous organic pollutants in soils and sediments less available to organisms and hindered their dispersal into unaffected environment. Some studies also showed that some sorbents from natural organic materials, such as peat, soybean stalk and pine needle under superheated temperature/pressure conditions, significantly affected the sorption of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. Natural materials significantly decreased the extractability and bioavailability of POPs from contaminated soils. Organic matter also plays a vital role in controlling the contamination of POPs in soil. The rhizosphere effect is showing promising to control POPs contamination in the soil environment. This review evaluated the work on the environmental behavior and bioavailability of POPs in soils as affected by various environmental variables.