3. Characterization of a contaminated site

Industrialization and extraction of natural resources cause environmental pollution in the World. Large amount of toxic (more than 450 million kilograms) waste materials (containing heavy metal) are disposed into the environment (soil, water and air) every day. These contaminants are causing ecological problem in all living organisms. Decontamination of the polluted environment is an essential issue to maintain ecological balance. Extensive work has been devoted to the development of remediation techniques by developed countries.

Therefore, it is very important to assess and characterize the contaminated sites for:

•Determining concentration and spatial distribution of harmful pollutants under consideration.

•Determining the extent of site remediation (zonation) based on which the suitable remediation technique is selected.

•For assessing environmental and human health risk due to contamination.

More specific questions have to be answer for site characterization and assesment:

•What is the source of contaminants?

•What is the type and physical form of contaminants?

•Spatial and depth wise extent of contamination

•Whether the contaminants are stationery or movable?

•If they are movable, identification of the significant pathways

•Identification of the potential receptors of contaminants 

A suitable remediation method has to be selected based on the toxicity level of contaminants and the risk they pose to the environment. The remediation does not aim for entire decontamination. The major focus is to bring the contamination level well below the regulatory toxic limit. The sustainability of remediation technologies is extremely important to analyze the long-term effect to avoid any potential problems in future.

In order to select the appropriate remediation techniques, the following steps need to be followed.

Identify Information Gaps. A desk study should be undertaken to decide if enough information exists to carry out a satisfactory risk assessment to a required degree of confidence. If not, the objectives of a further investigation need to be defined.

Site Safety. The potentially hazardous nature of the site will require consideration from the outset in order to identify any safety measures needed to protect personnel or the environment.

Nature of the Investigation. Once the objectives of a further investigation have been established, a decision on the nature of the investigation necessary to obtain suitable data must be made.

Sampling Locations and Depths. The locations and depths at which samples are to be collected and the number of locations required must be considered.

Chemical Analyses. The specification of what analyses should be carried out on the samples obtained during the investigation will be determined through research on the history of the site and consideration of the conditions encountered on-site.

Sampling Methods. The methods by which samples are to be obtained, preserved, and transported to the chemical testing laboratory require consideration.

Consultants and responsible parties often agonize over which technology will be the most cost effective, yet still meet the cleanup goals. Cost is a key factor in the selection of a remediation system because securing and budgeting funding is a serious problem that requires innovative uses of technologies to address and resolve the contamination issue. Often a single remediation technology is unable to adequately remediate a site’s contaminated soil and/or groundwater to below acceptable levels.

Currently used environmental cleaning applications mainly involve conventional remediation techniques. However, advancements in biosciences and biotechnology allow development of highly effective new and sustainable remediation techniques utilizing biological agents (bioremediation) in cleaning polluted environment and maintaining a healthy ecological balance. It is expected that most of the conventional environmental cleaning techniques will be replaced successfully by sustainable bioremediation techniques in near future. Bioremediation has many advantagous features such as permanence, low cost (60-90% less than other technologies), low maintenance, no eyesore, capability of impacting source zones, decreasing site clean-up time, and full degration of contaminant.