Bioremediation of Soil Ecosystems from Triazine Herbicides

Abstract

Microorganisms play an important role in maintaining ecosystem environmental quality, including pesticide removal from soil and water. Triazine herbicides are among the most commonly used pesticide worldwide. Moreover, they are ubiquitous soil and water contaminants. Atrazine, simazine, and terbuthylazine removal from environment depends on abiotic (photolysis and hydrolysis) and above all biotic degradation; only the latter is able to mineralize these herbicides. The presence of an abundant and varied microbial community is a necessary prerequisite for a prompt and effective triazine elimination from contaminated soil and water. Degradation rates can be highly variable, depending on the history of the herbicide treatment and on site-specific characteristics (e.g., soil depth, texture, mineralogy, organic carbon (OC) content, and pH). Several microorganisms able to remove atrazine from soil and water have been identified and can be used for bioremediation (bioaugmentation and biostimulation) purposes. They comprise prokaryotic cells and fungi which can use triazines for growth (catabolic degradation) or transform these herbicides by cometabolism. Some plants can partially degrade and detoxify triazines, however the effectiveness of phytoremediation in removal of triazines is hampered by their intrinsic toxic effects (they act on photosynthesis and glycogenesis, inhibiting the photosystem II) and depends on a plant capability to resist to its biocide effect and to form synergic interactions with microorganisms.