Bioremediation: a Natural Way to Clean the Environemnt

                                                                                                                                                           by Khaled Mahmud Shams

It’s quite a recent technology, a ‘green technology’, that is flourishing in the last 20 years.
Using plants rather than any expensive mechanical or chemical way is becoming more
popular among the nature conservationists and small scale site remediation firms.

Plants can fight pollution. Although it’s already doing since the beginning of life on earth.
But this time, its use is more planned and object-oriented. Everything is an object,
contaminants too. Plants can be used targeting these contaminants to detoxify soil,
water and air. As plants need carbon-di-oxide for photosynthesis, a process to produce
glucose for plants, it cleans the air spontaneously. Recently more and more scientific
investigations are carried out to see the results for soil decontamination.

Soil can be contaminated from various sources: municipal, industrial, agricultural wastes.
As a result a natural clean soil gets toxic and the surrounding eco-system suffers the loss
of its natural harmony. Not only the human population but vegetation, birds and many other
positive microorganisms extinct from the environment with further deteriorating consequences.

Industrial (developed) countries follow the regulations and regular monitoring from different government agencies helps keep the nature
clean. But in developing countries like India, China, Bangladesh where huge population means cheap labor, it’s getting worse as these
countries are rushing fast to come to a level similar to the developed countries. As technologies are getting easily available, so now you will
find same quality products from the developing countries as like the highly industrialized ones.

As a result huge areas both residential, forests and rivers, are being used as disposal sites. Soil gets polluted and further leaching
downwards threatens the aquifers deteriorating the water quality and affecting public health.

Many of the less developed countries are not able take huge remediation steps towards decontaminating the wastes sites. Bioremediation
can be an easy and effective choice for this purpose. Selected plants can be used to remove, degrade or immobilize contaminants in
rhizosphere area. Plants that can accumulate more toxic metals in its leaves and stems than the soil are called hyperaccumulators.  
Chinese brake fern, a hyperaccumulator, can store Arsenic in its leaves as much as 200 times that present in the soil. Sunflower is
successfully used in Chernobyl to take radioactive elements Uranium. Indian mustard showed positive response towards lead

Bioremediation is a lengthy process that can take years to clean a contaminated land. Not every plant responses positively towards
accumulation of toxic metals. Most of the plants will die in the early stages. Many plants which show good results accumulating metals do
not grow its natural growth, hence limit metal extraction. Many plants can recognize the harmful substances and store only in their roots,
which is a kind of phytostabilization that can again spread in the environment depending on the change of chemistry of the subsurface.
Acidity of soil is a big factor in this case. As acidic soils dissolves more metals, so metals get more mobile in the environment.

On the other hand it’s a natural process and for large waste disposal sites bioremediation is the right choice. Seasonal plants can be
harvested while new plants can let grow for further extraction.

Bioremediation is still in its infancy state. More and more research is going on in this field and new results are emerging everyday. Some
research groups are also working on ‘genetic improvement’ of plants for specific response to specific toxic metals. It can boost the industry
very much although genetic changes can be put into question and long-term investigation is needed to see the final results of plants
behavior towards pollutants and environment.

Experimental plants in lab.