The present paper is an overview of the presence and fate of pesticides as persistent organic pollutants in the environment as well as of the potential for their detoxification, also combined with chemical and physical treatment. It contains information gathered from a range of currently available sources. The fate of pesticides in the environment is analyzed considering the processes that determine their persistence and mobility, grouped into transport, transfer and transformation processes. Few pesticide characteristics such as persistence, mobility and biodegradability are emphasized. The fate of a pesticide and the potential for its persistence and mobility from the site of application are considered to be affected by the chemical and physical properties of the pesticide, site characteristics such as soil and groundwater individuality, climate and local weather conditions, biological population, and the handling practices of the pesticide user. Bioremediation, as one of the most environmentally-sound and cost-effective methods for the decontamination and detoxification of a pesticide-contaminated environment is discussed especially considering the factors affecting the biodegradability of pesticides such as biological factors and the characteristics of the chemical compounds. In situ and ex situ bioremediation as possible types of bioremediation activities are weighted up. Also, the paper includes some considerations for developing strategies regarding the choice of bioremediation technology, as well as advantages and disadvantages of the bioremediation of environmental components polluted with pesticides.

Fate of Pesticides in the Environment and its Bioremediation

Phytoremediation is a promising technology for the cleanup of polluted environments. The technology has so far been used mainly to remove toxic heavy metals from contaminated soil, but there is a growing interest in broadening its applications to remove/degrade organic pollutants in the environment. Both plants and soil microorganisms have certain limitations with respect to their individual abilities to remove/breakdown organic compounds. A synergistic action by both rhizosphere microorganisms that leads to increased availability of hydrophobic compounds, and plants that leads to their removal and/or degradation, may overcome many of the limitations, and thus provide a useful basis for enhancing remediation of contaminated environments. The review of literature presented in this article provides an insight to the nature of plant-microbial interactions in the rhizosphere, with a focus on those processes that are relevant to the breakdown and/or removal of organic pollutants. Due consideration has been given to identify opportunities for utilising the plant-microbial synergy in the rhizosphere to enhance remediation of contaminated environments. The literature review has highlighted the existence of a synergistic interaction between plants and microbial communities in the rhizosphere. This interaction benefits both microorganisms through provision of nutrients by root exudates, and plants through enhanced nutrient uptake and reduced toxicity of soil contaminants. The ability of the plant-microbial interaction to tackle some of the most recalcitrant organic chemicals is of particular interest with regard to enhancing and extending the scope of remediation technologies. Plant-microbial interactions in the rhizosphere offer very useful means for remediating environments contaminated with recalcitrant organic compounds. A better knowledge of plant-microbial interactions will provide a basis for improving the efficacy of biological remediations. Further research is, however, needed to investigate different feedback mechanisms that select and regulate microbial activity in the rhizosphere.

Utilising the Synergy between Plants and Rhizosphere Microorganisms to Enhance Breakdown of Organic Pollutants in the Environment (15 pp)

Management of soilborne pests and diseases in cropping systems is often highly challenging—in implementation of acceptable methodologies and in dealing with secondary problems. The phase-out of methyl bromide brings this into particularly sharp focus. There is a need for diversified options and alternatives to fill different roles across the soilborne pest and disease management spectrum, but flexibility is limited, as practicalities demand that they fit into a prophylactic methodology. It is against such a backdrop that expectations and promotion of alternatives must be set. There is also a need to recognize potentially serious problems that may have been masked under historical management regimes, but for which the nature of the system offers little scope to avoid or manage. Biofumigation is the beneficial use of Brassica green manures that release isothiocyanates chemically similar to methyl isothiocyanate, the active agent from the synthetic fumigant metam sodium, which is used as a substitute for met...

Biofumigation and Enhanced Biodegradation: Opportunity and Challenge in Soilborne Pest and Disease Management

Biodegradation of chlorpyrifos and its hydrolysis product 3,5,6-trichloro-2-pyridinol by Bacillus pumilus strain C2A1.

Fungicide impacts on microbial communities in soils with contrasting management histories.

Pesticide fate in the environment is affected by microbial activity. Some pesticides are readily degraded by microorganisms, others have proven to be recalcitrant. A diverse group of bacteria, including members of the genera Alcaligenes, Flavobacterium, Pseudomonas and Rhodococcus, metabolize pesticides. Microbial degradation depends not only on the presence of microbes with the appropriate degradative enzymes, but also on a wide range of environmental parameters. This review describes recent advances in biodegradation of pesticides by addressing the biology and molecular characterization of some pesticide degrading bacteria.

G. Lloyd-Jones

Papers

A review of bacterial degradation of pesticides