Question

An agricultural land prone to rainfall showed that the pesticides used over the crops have been washing off to the nearby lake due to surface runoff. Surface runoff is a process by which pesticides are transported in dissolved or particulate forms along the surface of sloping agricultural land. In addition, the soil has high permeability, initial site visit showed that vertical downward displacement of these pesticides through the soil profile and the unsaturated zone, finally reaching groundwater might also a high possibility. The results of the initial tests revealed that the highest concentrations were observed for organochlorine and organophosphate among other pesticides.

As an environmental engineer tasked with this site, Select the best bio-remediation option to deal with this problem and explain your reasoning, with advantages and disadvantages.

Answer 1

Bioremediation- it is process of using living organism to remove pollutants from contaminated sites. Bioremediation of soil that is affected by pesticides can be done by use of microorganisms, earthworms, plants, cell free enzymes.

Use of earthworms can be preferred in this case as in other methods cost of cell free enzymes are huge, use of plants take long time for the process, use of microorganism may not give optimal results as pesticides may interfere in growth of microorganism.

Earthworms can degrade the pesticides, either by releasing of pesticide-detoxifying enzymes gastrointestinal tract

or with the help of stimulation and dispersion of microorganisms those can degrade pesticides.

Advantages of the process-

1.) physiochemical and biological properties of soil treated by bioremediation is least affected.

2.) it is an ecofriendly process.

3.) it is a cost effective process.

4.) earthworm enhances microbial proliferation thus soil biodegradation capacity is enhanced. it can also increase pesticide bioaccessibilty which helps in microbial degradation.

disadvantages-

1.) survival of earthworm is highly dependent on soil conditions such as moisture, temperature.

2.) it is sensitive wrt toxicity of pesticides.