环境保护论文代写:After effects of man-made chemicals

环境保护论文代写:After effects of man-made chemicals

3.3.6 Soil Washing

Soil washing uses water to remove contaminants from soils. The principle of soil washing lies in separating the most polluted portion from the cleaner portion of the soil by scrubbing it. This scrubbing process reduces the amount that needs to be cleaned, and we get two fractions of soil; clean and polluted.

3.4Selection Criterion

After understanding the different technologies applicable for the remediation, we have to identify the suitable technique for the soil. General selection criterions followed are:

The selection of a suitable remedial technology, thefollowing steps are necessary (US EPA 1991):

• Determination of remedial objectives and identification of response action: This step identifies existing site problems using preliminary remedial investigation data
• Technology screening: This step identifies and screens potential applicable remedial technologies. It focuses on eliminating those technologies which have severe limitations for a given set of waste-and site-specific conditions.
• Development and screening of remedial action alternatives: These alternatives represent workable number of options that appear to adequately address all site problems.
• Detailed evaluation of remedial action alternatives, and remedial alternative selection: The alternative technologies are then subjected to detailed evaluation. For each remedial alternative, the following factors are analysed:

• Technical considerations
• Environmental concerns
• Public health concerns.
• Institutional concerns.
• Costs.

• Remedial alternative selection: After detailed evaluation of action alternatives, each of the alternatives is summarized relative to each of the criteria described above.

These criteria should limit improper and irresponsible use of the solutions.

4. MODEL ASSESSMENT USING DIRECT SHEAR TEST

4.1 General

The shear strength is one of the most important engineering properties of a soil, because it is required whenever a structure is dependent on the soil’s shearing resistance. The shear strength is needed for engineering situations such as determining the stability of slopes or cuts, finding the bearing capacity for foundations etc.

4.2 Direct Shear Test

The direct shear test is one of the oldest strength tests for soils. In this laboratory, a direct shear device will be used to determine the shear strength of cohesion less soil. From the plot of the shear stress versus the horizontal displacement, the maximum shear stress is obtained for a specific vertical confining stress. After the experiment is run several times for various vertical-confining stresses, a plot of the maximum shear stresses versus the vertical (normal) confining stresses for each of the tests is produced. From the plot, a straight-line approximation of the Mohr-Coulomb failure envelope curve can be drawn, f may be determined, and, for cohesion less soils (c = 0), the shear strength can be computed from the following equation:

s = stanf

Equipments:Direct shear device, Load and deformation dial gauges, Balance.

4.3 Procedure

The procedure which is followed in performing direct shear test is as follows:

1. Measure inner side or diameter of shear box and find the area.
2. Make sure top and bottom halves of shear box are in contact and fixed together.
3. Weigh out 150 g of sand.
4. Place the soil in three layers in the mold using the funnel. Compact the soil with 20 blows per layer.
5. Place cover on top of sand.
6. Place shear box in machine.
7. Apply normal force.

Two soil specimens were chosen for the test.

Sample one: Clean and not contaminated with weight of 16 kg

Sample two: Contaminated with fuel ash with weight of 8 kg

4.4 Calculations

1. Determine the dry unit weight.
2. Calculate the void ratio, e
3. Calculate the Normal stress and Shear stress

4.5 Results

As explained in the procedure above, two soil samples were tested. After the test, following results were obtained:

1. Load at failure for sample one = 57.6 N
2. Load at failure for sample two = 32 N

The contaminated sample will be used for the design project to asses it is commercial viability.

4.5 Remedial Solution

In order to get the remedial solution to the given problem with fuel ash as a contaminant, some more information is required concerning the physical and chemical properties, the distribution and migration behavior of the contaminants as well as concerning the geological and hydro-geological conditions of the contaminated site. So, the steps given below should get us to the remedial solution.

1. State of aggregation and properties like stability, water solubility of the pollutant fuel ash.
2. Location of the fuel ash i.e. in the soil-air, solved in the soil-water, adsorbed at soil particles or located in all phases.
3. Description of soil payers
4. Hydro-chemical characterization of the soil water

So, now the next step is to carry out an assessment of the resulting environmental risk depending upon the above mentioned steps. For acute high risks, in-situ procedures can be excluded as they are time consuming. So, final remedial solution should be selected considering the aspects such as costs and requirement of local authority.

5. CONCLUSIONS

• The above report comprises of the discussion of Soil contamination with its causes and effects.
• Various remediation technologies have been developed and used extensively. Appropriate technology is chosen according to the type of contaminant and environmental requirement.
• For the example assessment, a contaminated soil sample with fuel ash is chosen which is tested for its shear strength using Direct Shear Test.
• Results of the direct shear test are presented in terms of the load at failure for two different soil specimens. From results, it is inferred that the load at the failure for the contaminated soil specimen is quite less than that of clean soil specimen.
• As observed due to the various unwanted components the shear strength of the contaminated soil is reduced, thereby hampering its utility and value.
• Using the results of test and environmental conditions, the appropriate solution can be selected in accordance with the selection criteria.
• Soil is an essential component of natural ecosystems as environmental sustainability relies largely on soil ecosystem. Therefore, the contamination of soil is a very big social problem because of its importance for environment protection and human health.

REFERENCES

• Berrow, M.L. (1986) An overview of soil contamination prob­lems. In: Proc. Int. Conf. Chemicals in the Environment. Lester, Perry and Sterrit (eds.) London, Selper, pp. 543-552.
• J.W. Doran, M. Sarrantonio, M.A. Liebig , Soil Health and Sustainability,Advances in Agronomy, Volume 56, 1996, Pages 1-54
• ASTM (2000). Standard Guide for Developing Conceptual Site Models, American Society for Testing and Materials. Report No. E1689-95.
• Bardos, P., Nathanail, J. & Pope, B. (2002). General principles for remedial approach selection. Land Contamination & Reclamation 10(3): 137-160.
• Oliver, M.A., 1997. Soil and human health: a review. European Journal of Soil Science 48, 573-592.
• Environment Agency (2003) Model Procedures for the Management of Land Contamination. Report CLR 11. Consultation draft v2/2.
• Adriano, D.C., Chlopecka, A. and Kaplan, K.I. (1998) Role of Soil Chemistry in Soil Remediation and Ecosystem Conserva­tion. Soil Sci. Soc. Am. Spec. Public. Madison, WI.
• Reducing soil contamination: economic incentives and potential benefits Agriculture, Ecosystems & Environment, Volume 67, Issues 2-3, February 1998, Pages 275-288,François Bonnieux, Alain Carpentier, Robert Weaver
• Adriano, D.C., Chlopecka, A., Kaplan, D.I., Clijsters, H. and Vangronsveld, J. (1995) Soil contamination and remediation: philosophy, science and technology. In: Contaminated Soils, R. Prost ed. INRA Les olloques, n° 85, Paris. pp. 465-504
• Environment Agency (2003) Model Procedures for the Management of Land Contamination. Report CLR 11. Consultation draft v2/2.
• http://www.env.go.jp/en/water/soil/contami_cm.pdf
• Engineering Properties of Soils Based on Laboratory Testing ,Prof. Krishna Reddy, UIC