SOIL CONTAMINATION DUE TO LEATHER WASTE

TITLE OF THE PROJECT

            “SOIL CONTAMINATION DUE TO LEATHER WASTE”-

              “KNOW YOUR SOIL USAGE TO THEIR EXTENT”

INTRODUCTION

We know we belong to the land, and the land we belong to is grand!

-Oscar Hammerstein

“Know your Soil”

Soil  is a natural body consisting of layers (soil horizons) of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics.^[1] 

It is composed of particles of broken rock that have been altered by chemical and environmental processes that include weathering and erosion. Soil differs from its parent rock due to interactions between the lithosphere, hydrosphere, atmosphere, and the biosphere.^[2] It is a mixture of mineral and organic constituents that are in solid, gaseous and aqueous states.^[3][4]

Soil particles pack loosely, forming a soil structure filled with pore spaces. These pores contain soil solution (liquid) and air (gas).^[5] Accordingly, soils are often treated as a three state system.^[6] Most soils have a density between 1 and 2 g/cm³. ^[7] Soil is also known as earth: it is the substance from which our planet takes its name. Little of the soil composition of planet Earth is older than the Tertiary and most no older than the Pleistocene.^[8] In engineering, soil is referred to as regolith, or loose rock material.

Soil pollution

Soil pollution is defined or can be described as the contamination of soil of a particular region. Soil pollution mainly is a result of penetration of harmful pesticides and insecticides, which on one hand serve whatever their main purpose is, but on the other hand, bring about deterioration in the soil quality, thus making it contaminated and unfit for use. Insecticides and pesticides are not to be blamed alone for soil pollution, but there are many other leading causes of soil pollution too. Let us have a look at some of them in the following text

 Introduction to Sources of soil pollution:

Soil pollution is caused mainly by solid wastes and chemicals. One of the major problem of large cities are disposal of solid wastes, chemicals, garbage, paper, plastics, rubber, leather, metals and dead animal remains. The following are the main sources of soil

pollution

1. Chemical pollutants

2. Industrial effluents

3. Biological agents

4. Metallic pollutants

5. Agricultural wastes

6. Radioactive pollutants

7. Pesticides and fertilizers

Major Sources of Soil Pollution

1. Chemical pollutants-A number of industries like textiles, pesticides, pharms, fertilizer, paper, sugar, petroleum and glass industries pour their hazardous effluents into soil. Salts and chemicals dumped in soil deposit on the upper layer and make soil unfit for cultivation. Toxic organic compounds and phenols destroy the fertility of the soil.

2. Industrial effluents- The effluents from water, waste water and industrial waste water treatment facilities are included in this category. Almost all of the factories and industries are known to discharge their effluents or waste water into the neighboring land or water sources thus causing soil pollution.

3. Biological wastes-These mainly include food wastes resulting from food preparation, street sweepings, litter, dead animals and hospital wastes. These waste materials harbor microorganisms and are likely to spread diseased due to their unhygienic way of disposal.

4.metallic pollutants- These pollutants which include heavy metals like mercury, cadmium, chromium etc are released from industries such as batteries, tanneries, steel and other dyeing industries. These heavy metals stay in the soil and through the uptake through plants may pose risk in human food chain.

5. Agricultural wastes-This category of wastes is generated in the process of farming and other agricultural practices. The plant wastes generated after harvesting, farm animals. Residues and other farm wastes. These wastes are mainly generated in rural areas where agriculture is the main form of livelihood.

6. Radioactive pollutants-Atomic reactors, nuclear radioactive devices and nuclear weapons releases radioactive wastes which enter the land and accumulate there causing soil pollution. Sr 90,Cs137,Ba 40 isotpes released are hazardous for man. Radioactive waste material deposited in the land cause gamma radiations which are harmful to plants, aquatic life and human beings.

7. Pesticides and fertilizers - An increasing concern in agriculture is that the increased use of pesticides and fertilizers to improve crop yield are leaving their residues in soil, thus reducing the micro fauna in soil and decreasing the fertility of soil. Pesticides are known to be non biodegradable and therefore enter food chain and result in biomagnifications.

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“Our theme”-leather effluent

Leather:

Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.

The leather manufacturing process

The leather manufacturing process is divided into three fundamental sub-processes: preparatory stages, tanning and crusting. All true leathers will undergo these sub-processes. A further sub-process, surface coating, can be added into the leather process sequence but not all leathers receive surface treatment. Since many types of leather exist, it is difficult to create a list of operations that all leathers must undergo.

The preparatory stages are when the hide/skin is prepared for tanning. Preparatory stages may include: preservation, soaking, liming, unhairing, fleshing,splitting, reliming, deliming, bating, degreasing, frizing, bleaching, pickling and depickling.

Tanning is the process which converts the protein of the raw hide or skin into a stable material which will not putrefy and is suitable for a wide variety of end applications. The principal difference between raw hides and tanned hides is that raw hides dry out to form a hard inflexible material that when re-wetted (or wetted back) putrefy, while tanned material dries out to a flexible form that does not become putrid when wetted back. Many different tanning methods and materials can be used; the choice is ultimately dependent on the end application of the leather. The most commonly used tanning material is chromium, which leaves the leather, once tanned, a pale blue color (due to the chromium); this product is commonly called "wet blue". The hides once they have finished pickling will typically be between pH 2.8 and 3.2.At this point, the hides would be loaded in a drum and immersed in a float containing the tanning liquor. The hides are allowed to soak (while the drum slowly rotates about its axle) and the tanning liquor slowly penetrates through the full substance of the hide. Regular checks will be made to see the penetration by cutting the cross-section of a hide and observing the degree of penetration. Once a good, even degree of penetration exists, the pH of the float is slowly raised in a process called basification. This basification process fixes the tanning material to the leather and the more tanning material fixed, the higher the hydrothermal stability and increased shrinkage temperature resistance of the leather. The pH of the leather when chrome tanned would typically finish somewhere between 3.8 and 4.2

Crusting is when the hide/skin is thinned, retanned and lubricated. Often, a coloring operation is included in the crusting subprocess. The chemicals added during crusting have to be fixed in place. The culmination of the crusting subprocess is the drying and softening operations. Crusting may include the following operations: wetting back, sammying, splitting, shaving, rechroming, neutralization, retanning, dyeing, fatliquoring, filling, stuffing, stripping,whitening, fixating, setting, drying, conditioning, milling, staking, and buffing.

For some leathers, a surface coating is applied. Tanners refer to this as finishing. Finishing operations may include: oiling, brushing, padding, impregnation, buffing, spraying, roller coating, curtain coating, polishing, plating, embossing, ironing, ironing/combing (for hair-on), glazing and tumbling.