ABSTRACT

Bioaugmentation involves using a consortium of microorganisms to depollute an impacted medium. Bioremediation of pollutants by natural attenuation requires no human intervention, whereas implementation of accelerated and controlled biotreatment-based processes may be directed to exploiting microbial technology and bioprocess engineering to optimize the rate or extent of pollutant degradation. Upon the foregoing, a study was undertaken to ascertain the comparative effects of fungal degradation of glyphosate on some physico-chemical properties of soil using Randomized Complete Block Design (RCBD). In this attempt, five Treatments were used viz: T1 (Fungi+herbicide+plant), T2 (No fungi+Herbicide+plant), T3 (Fungi-Herbicide+plant), T4 (Fungi+herbicide+plant) and T5 (- Fungi -herbicide-plant i.e.control). The results indicated that the addition of fungal strains imparted a significant difference (P=0.05) in organic matter content and pH of the studied soils when compared with the control. However, the mean value of exchangeable acidity, ECEC, textural properties and electrical conductivity in the soil were not significantly affected by the application of Treatments. The fungal isolates employed in this research further imprints some promises as ecofriendly and economical alternatives in managing the problems associated with the use of conventional herbicides.

 KEYWORDS: Glyphosate, Herbicides, Bioaugmentation.

CHAPTER ONE

                                     INTRODUCTION

1.1 Background of study

Pesticides are any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest (insects, rodents, nematodes, fungus, weeds and other forms of terrestrial or aquatic plant or animal (Mishra et al, 2001). Pesticides are directly toxic to pests, having indirect effects on soil microorganisms as well as soil properties (Mishra et al, 2001).Mishra et al, (2001) observed that physico-chemical properties of the soil, nature of substrates and environmental degradation determine the persistence of pesticides in nature. Excessive persistent and biological active residues endanger non-target organisms, prove hazardous and make the pest control operation uneconomical. In recent times there has been a steady increase in the number and amount of residues of pesticides in our food and soil (Behera and Mishra, 2001). While pesticides serve useful purposes, concern has been expressed regarding their possible effect on environment. Persistence of pesticides in soil depends on their dose as much as on the characteristics of the soil, such as physico-chemical properties, structure, temperature and moisture (Brusch, 2010).  The toxic effect of pesticides on humans and the environment can be direct or indirect. One of the possible side-effects of using herbicides involves some disturbance of the biochemical processes occurring in soil (Digrak and Ozcelik, 1998). Active substances found in many herbicides may hamper the rate of a series of biochemical processes, interfering with the soil enzymatic activity and microbial growth. Modifications in the count and activity of microorganisms may lead to upsetting the biological equilibrium of soil, which in turn depresses its fertility. All these considerations emphasize the importance of studies on the effect of pesticides on the biological activity of soil (Braschiet al., 2000), and particularly on soil enzymes, which can serve as a good indicator of the impact of pesticides on soil metabolism.

1.2 Contamination with Pesticides

Several hundred pesticides of different chemical nature are currently widely used for agricultural purposes throughout the world (Barceló, 1991), which resulted in mixed impacts. On the one hand, utilization of pesticides produces an enormous increase in agricultural productivity (Kuo and Regan, 1999). On the other hand, due to their widespread use, pesticides are currently detected in various environmental matrices such as soil, water and air (Barceló, 1991) and there is great concern about their potential environmental hazard (Sanninoet al., 1999). Inadequate management practices specifically involving the on-farm handling of pesticides appear to be a major source of pesticide contamination (Kuo and Regan, 1998). The wastes from spray and storage equipment are sources of contamination (Kuo and Regan, 1999) and soil disposal is the most common method of handling these diluted pesticide wastes (Schoen and Winterlin, 1987). Also of great concern are pesticide spills or waste disposal sites, which are characterized by the presence of large quantities of pesticides often in mixtures in localized areas of soil (Gan and Koskinen, 1998). When the concentration of a pesticide, its metabolites or by-products is significantly excessive, remediation is necessary to avoid migration to a more sensitive area of the environment (Kearney, 1998).The chemical properties of pesticides determine their retention and transport in soils (Kearney, 1998).

1.3 Aims and Objectives of the Study

The primary aim of this research is to verify the effect of pesticides contamination in the soil and the potential benefits of mycoremediation of pesticides contaminated soil as it affect physicochemical properties of the soil.

The following are the specific objectives of this work:

  1. To isolate from the soil in-situ, a pure strain of fungus that shall be subsequently deployed in the remediation experiment.
  2. To verify the effect of pesticide clean up on the soil using this fungus on some physico-chemical properties of the pesticide contaminated soil.

1.4   Statement of the Problem

Pesticides contamination is a major issue in our time. Soil can be degraded and the community of organisms living in the soil can be damaged by the misuse or over use of pesticides. Some pesticides are more toxic to soil organisms than others; some pesticides may break down quickly when applied to soils, while others may persist for longer periods. The type of soil and the type of pesticide can also affect pesticide persistence. Hence, the exploitation of the biochemical pathway of some naturally occuring components of the soil, particularly fungi (because fungi are known as nature’s primary recyclers) in reducing pollutant load in the soil is not only desirable but imperative.

For more project on Faculty of Science visit: project.edugist.ng/science