Forensic analysis of soil

Soil composition, layers, examination is described

1. FORENSIC ANALYSIS OF SOIL Sivakrishnan .R MSc. Sem I Submitted to- Ketan Sir Shri V aishnav Institute of Forensic Science

2. INTRODUCTION Definition : Soil is the upper layer of earth in which plants grows, a black or dark brown material typically consist of mixture of minerals, water, gases, and other organic decaying remains. Weathering is the mechanical or chemical process by which rocks are broken down into smaller pieces. As rocks are broken down, they mix with organic materials, which are those materials that originate from living organisms. For example, plants and animals die and decompose, releasing nutrients back into the soil. Soil is highly heterogeneous in nature and varies widely from place to place due to the effects of wind, water, living organisms, mining and agriculture. Thus, Soil from different places will have different individual characteristics. 2 Sivakrishnan.R | MSc. Sem 1

3. TYPES OF SOIL Soil can be categorised into : Sand Clay Silt Peat Chalk Loam 3 Sivakrishnan.R | MSc. Sem 1

4. Sandy soil Sandy soil are light, warm, dry and tend to be acidic and low in nutrients. Sandy soils are often known as light soils due to their high proportion of sand and little clay (clay weighs more than sand). These soils have quick water drainage and are easy to work with. The addition of organic matter can help give plants an additional boost of nutrients by improving the nutrient and water holding capacity of the soil. 4 Sivakrishnan.R | MSc. Sem 1

5. Clay soil Clay soil are heavy soils that benefit from high nutrients. Clay soils remain wet and cold in winter and dry out in summer. These soils are made of over 25 percent clay, and because of the spaces found between clay particles clay soils hold a high amount of water. Because these soils drain slowly and take longer to warm up in summer, combined with drying out and cracking in summer, they can often test gardeners. 5 Sivakrishnan.R | MSc. Sem 1

6. Silt Soil Silt soil are light and moisture retentive soils with a high fertility rating. As silt soils compromise of medium sized particles they are well drained and hold moisture well. As the particles are fine, they can be easily compacted and are prone to washing away with rain. By adding organic matter, the silt particles can be bound into more stable clumps. 6 Sivakrishnan.R | MSc. Sem 1

7. Peat Soil Peat soil are high in organic matter and retain a large amount of moisture. This type of soil is very rarely found in a garden and often imported into a garden to provide an optimum soil base for planting 7 Sivakrishnan.R | MSc. Sem 1

8. CHALK SOIL Chalk soil can be either light or heavy but always highly alkaline due to the calcium carbonate or lime within its structure. As these soils are alkaline they will not support the growth of ericaceous plants that require acidic soils to grow. If a chalky soil shows signs of visible white lumps then they can’t be acidified and gardeners should be resigned to only choose plants that prefer an alkaline soil. 8 Sivakrishnan.R | MSc. Sem 1

9. Loam Soil Loam soil   are a mixture sand, silt and clay that are combined to avoid the negative effects of each type. These soils are fertile, easy to work e of with and provide good drainage. Depending on their predominant composition they can be either sandy or clay loam. As the soils are a perfect balance of soil particles, they are considered to be a gardeners best friend, but still benefit from topping up with additional organic matter. 9 Sivakrishnan.R | MSc. Sem 1

10. SOIL HORIZONS Soil horizons are distinct layers of soil that form naturally in undisturbed soil over time. The formation of soil horizons is called soil geomorphology and the types of horizons are indicative of the soil order. Like other natural processes, the age of the horizon increases with depth. Soil Horizon Names and Descriptions O: Decaying plants on or near surface A : Top Soil, Organic Rich B : Subsoil, Most Diverse Horizon and the Horizon with the most sub classifications  C : Weathered/aged parent material R : Bedrock 10 Sivakrishnan.R | MSc. Sem 1

11. METHODOLOGY Simple Observations Microscopical Observation with Chemical Regents Ignition Test pH Measurement Particle size distribution Density distribution 11 Sivakrishnan.R | MSc. Sem 1

12. Simple observations ( Stereo-microscope capable with high magnification range.) Take some soil sample on a clean microscopic slide/ glass plate and make its thin layer. Place the slide/plate with soil on viewing stage of stereo-microscope and using different magnifications. take the microscopic observations of soil sample retained in each sieve during the sample preparation separately in the following manner: Observe the colour of soil particles after drying at 105oC. Observe the nature of particles as- geometrical shape, black particles (coal dust, black minerals), red particles (brick dust, red ash, iron oxide or metal oxide), colourless particles (quarts grains, colourless mineral fragments), green minerals, particles of vegetation (grass, leaf fragments, seeds, moulds, fungi, micro-organism etc. Find out the traces of foreign materials as -dung cloth fibres, glass fragments, hair, wooden particles etc. Note every observation and compare with control soil sample. 12 Sivakrishnan.R | MSc. Sem 1

13. Microscopical Observation with Chemical Regents Place the soil sample on the stage of microscope in the same manner as described above and examine. Moisten a small portion of soil with water and then add a small drop of concentrated hydrochloric acid (HCl) on it. Observe the nature of reaction as- bubbles and colour. Bubbles arising from solid particles indicate insoluble carbonates such as chalk, dolomite or lime stone. Similarly yellowing colour indicates the presence of soluble iron it can be confirmed by appearance of green colour on adding a few drops of potassium ferrocynide solution to the sample 13 Sivakrishnan.R | MSc. Sem 1

14. Ignition Test Apparatus : Analytical balance with an accuracy 0.0002 gm, Standard Weights, Alumina crucible (porcelain dish may be used), Muffle furnace of high temperature range (1000 14 °C), Method: Take an exactly weighed quantity (one gm) of soil sample from sieve fractions dried at 105°C in a alumina crucible and keep it in a muffle furnace. Heat it at temperature between 750-800°C for 1 hr. And then, cool it to room temperature. Reweigh accurately and record the loss in weight and change in colour on ignition. Calculate the percentage of loss on ignition to the nearest 0.1 and compare it with a control soil sample. Calculation: Initial weight of soil sample taken = Wo g Weight of soil sample after ignition = W1 g Weight loss on ignition = ( Wo - W1) g Percent weight loss =( Wo - W1)/ (W0) * 100 14 Sivakrishnan.R | MSc. Sem 1

15. pH Measurement of Soil Sample In order to observe the acid-alkali behaviour of the soil, pH value of soiL sample can be determined as follow: Apparatus: a pH-meter with standard electrolytes (buffers) solution of pH 7 and 4. Method: First, standardize the pH-meter with respect to buffers solution of pH 7 and 4 by using the usual process as it is mentioned in its operating manual. Dissolve weighed quantity ( one gm of soil sample in 100 ml distilled water and stir thoroughly. Filter it. Take the filtrate and measure the pH value. Adding 10 ml, 20ml, 30ml, 40ml, and so on successively in solution, measure the pH values after each dilution and observe their variations. Similarly, measure the pH values for control soil sample in the same conditions and compare with suspect soil sample. 15 Sivakrishnan.R | MSc. Sem 1

16. Particle size distribution Requirements : Set of sieves (ranging in size from ASTM No.5 to 200), Motor-driven sieve shaker, standard weights.   Procedure: Take an accurately weighed quantity (50)gm of soil sample. Arrange all the set of sieve in numerical order and shake the soil. Collect the soil retained in the each sieve separately and reweight accurately calculate its percentage as given below . Percentage of soil retained on sieve No.=   (Weight of soil retained on sieve) x 100 (Total weight of soil taken) 16 Sivakrishnan.R | MSc. Sem 1

17. Density distribution of Soil particles This analysis depends upon the principle that an object will be suspended in a liquid of same density. it will sink in a liquid that is less dense and float in a liquid that is more dense. When two different liquids of different density are mixed together, they will diffuse into one another and its density will as: D1 = [(V1d1) + (V2d2)] (V1) + (V2)     Where: d1 = density of liquid I (more dense; bromoform ) d2 = density of liquid II ( less dense; xylene ) V1 = volume of liquid I ( bromoform ) in ml V2 = volume of liquid II ( xylene ) in0 ml 17 Sivakrishnan.R | MSc. Sem 1

18. Particle size distribution Requirements : Set of sieves (ranging in size from ASTM No.5 to 200), Motor-driven sieve shaker, standard weights.   Procedure: Take an accurately weighed quantity (50)gm of soil sample. Arrange all the set of sieve in numerical order and shake the soil. Collect the soil retained in the each sieve separately and reweight accurately calculate its percentage . 18 Sivakrishnan.R | MSc. Sem 1

19. FORENSIC IMPORTANCE Soil is a common form of physical evidence found at the scene of crime such as Hit and Run accidents, Automobile collisions, Rape and Burglaries. A number of physical and chemical methods have been used for identification of source as well as for comparison of two soils. 19 Sivakrishnan.R | MSc. Sem 1

20. Reference Saferstein, Richard, 1978, Criminalistics- An Introduction to Forensic Science, Prentice-Hall of India Pvt. Ltd. New Delhi (INDIA). Nicholls, L.C. 1956, The Scientific Investigation of Crime, Butterworth & Co. (Publishers) Ltd. LONDON. Laboratory Procedure Manual- Forensic Physics Kirk, Paul, 1960. Crime Investigation, Inter science Publishers Inc. New York (USA). 20 Sivakrishnan.R | MSc. Sem 1