BEHAVIOR OF ORGANIC POLLUTANTS IN THE SOIL ENVIRONMENT. SPECIAL FOCUS ON GLYPHOSATE AND AMPA

Abstract

In industrialized countries, soil and groundwater contamination by various forms of harmful substances is a contemporary problem in this highly industrialized age. In this document, the state of the art regarding the main mechanisms, processes and factors governing the fate and behavior of organic contaminants in the soil-ground water system is reviewed. The behavior of organic contaminants in soils is generally governed by a variety of complex dynamic physical, chemical and biological processes, including sorption–desorption, volatilization, chemical and biological degradation, uptake by plants, run-off, and leaching. These processes directly control the transport of contaminants within the soil and their transfer from the soil to water, air or food. The relative importance of these processes varies with the chemical nature of the contaminant and the properties of the soil. Both the direction and rate of these processes depend on the chemical nature of the organic contaminant and the chemical, biological, and hydraulic properties of the soil. Some organic contaminants are degraded in the soil within a certain time. On the other hand some are degraded only slowly or are sequestered within soil particles thus being inaccessible for microbial degradation. Persistence in soils increases the potential for environmental consequences. Mobility in soil environments is a key factor in assessing the environmental risk. Compounds interacting weakly or not at all with soil surfaces will be leached together with the soil solution and have the potential for contaminating surface or ground water reservoirs far from the point of getting into the soil. Clays, oxides and organic matter are the primary constituents in soils responsible for the sorption of organic contaminants. Among the organic contaminants used in agriculture, one of the most world-wide applied herbicides is glyphosate, an organophosphonate product, with broad spectrum of application. Results of two field experiments conducted in two sites of Austria show the influence of different tillage systems, vegetation cover, and site specific properties on the risk of surface run off of glyphosate. Better understanding of the behavior of glyphosate is needed (e.g. adsorption conditions, environmental influence, specific soil parameters, soil microbes behavior) for a better risk assessment of environmental pollution. Based on this knowledge time-dependent adsorption, degradation rates and consequently risks of contamination for surface and groundwater involved can be estimated.