Daw Daw! Do Now: How can soil evidence be valuable even if the site of the crime has not been ascertained? What is a mineral and how can minerals be important in the comparison of soil samples? HW: Ch 12 #5,10,24-26 and p479 #3 Be sure to look over the case on pg 473 for tomorrow…hint hint

What Is Soil? Mixture of organic and inorganic material May range from 100% inorganic (sand) to nearly 100% organic (peat) Inorganic part is minerals Organic part is decayed plant and animal material and is sometimes called humus

Soil primarily made of: weathered rock air H2O bacteria Humus soil formation process is what makes soils unique influenced by temperature, rainfall, chemicals and minerals present

Forensic Significance of Soil Soil is class evidence - cannot be individualized to a particular location Soils can be easily transported Soils within a few meters horizontally or vertically differ

Soil Composition Three main grain sizes Sand largest Silt Clay  smallest Three sub categories of soil Loam  sand, silt, clay Peat  more than 20% decaying material Chalk  Alkaline, solid but soft rock

Soil Type Comparison

Horizons in a Soil Sample

Horizons O Horizon A Horizon E Horizon Humus- decaying organic material A Horizon “top soil” soil is dark in color mixture of Humus and mineral particles This is where seeds sprout and plant roots grow E Horizon Light in color Made of sand and silt H2O drips through this layer and carries away most of the minerals and clay originally present

Horizons cont’d B Horizon C Horizon R or D Horizon “subsoil” contains clay and mineral deposits that have leached from layers above C Horizon layer is made up of partially broken rock no humus or plant roots R or D Horizon soild rock

Chemistry of Soil Nutrients: NPK Nitrogen Phosphorus Potassium promotes chlorophyll production needs a pH >5.5 to be dissolved in H2O and contained within the soil Phosphorus necessary for root development and increases flowering ability and size needs a pH between 6.0-7.0 Potassium guards against disease and aids in draught protection and cold tolerance

pH Review NPK dissolves more easily in slightly acidic or alkaline environment Rainfall, pollution, acid rain, and fertilizer can all affect pH

Results of nutrient Deficiencies

Sand Formed by Weathering action of wind and water on rocks collisions break rock into smaller and smaller pieces grains are usually 0.05mm to 2mm in diameter Shape is rounded or angular Crystal- if sand only contains one type of mineral Fragment- if the grain consists of 2 or more minerals

Sand Rounding Immature or Young Mature or Old can take millions of years to complete Immature or Young contains a large portion of clay grains have a high % of fragments Found in bottom of bays, lagoons, swamps or river plains Mature or Old No clay and fewer fragmented edges Found in beaches and desert dunes lots of H2O and weathering

Sand Composition

Continental contains quartz, micas, feldspar, hornblede, magnetite if present then the sand probably came from a temperate, polar climate, or a high latitude in warm, tropical climates it weathers away quickly Quartz high % means that the sand is very old weathers very slowly

Mineral Components of Sand

Volcanic usually dark in color because of black basalt or green olivine From mid-ocean volcanoes, hot-spot volcanoes (Hawaii) sometimes contains volcanic cinders or other volcanic debris very young and has little to no quartz

Skeletal made from marine organisms: younger type of sand microogranisms shells corals younger type of sand Coral is found only in tropical regions Large amounts of CaCO3  creates bubbles with the addition of acid

Precipitate contains dissolved minerals when H2O evaporates minerals come out of solution and form crystals CaCO3 can precipitate out of sea water forming a coat of hard particles that resemble an onion eventually form small, round particles oolites

Soil Collection collect all samples as soon as possible collect at surface baseline and samples that appear different or out of place from the rest of the environment collect at least 4 tbsp of material from several locations at the scene. (Plastic Vials) sketch the crime scene and note where the samples were obtained be careful not to remove soil stuck to shoes, clothing, or tools found at the crime scene. Package these items separately in appropriate containers (Paper Bags) carefully remove soil from vehicles and package the soil samples separately Document all samples by taking photographs, drawing sketches, and labeling the evidence collection containers Collect additional soil samples from the four compass point (N,S,E,W) within a few feet of the crime scene. Collect another set 20-25 feet from the crime scene

Soil Examination compare characteristics of the soil samples from suspect or crime scene to those from a known location layers of soil or mud from shoes or wheels can show that a suspect was present at a series of locations compare size, shape, color by looking macroscopically soil type, amount of organic material, particle size Can be identified and compared by density moisture content chemical testing for mineral content X-ray Diffraction

To identify the minerals in rock and soil samples, the Curiosity will lean heavily on X-ray diffraction technology X-ray diffraction is the most reliable way to identify minerals, but this is the first time it will be used on a mission to Mars. When samples are collected, an X-ray beam will be focused at it, and the sample will scatter the X-rays in different directions

each mineral has a trademark diffraction pattern, allowing scientists to identify what mineral they're looking at NASA’s Curiosity rover has completed the first-ever detailed X-ray analysis of Martian sand, determining that it contains minerals similar to volcanic soil found at places like the Mauna Kea shield volcano in Hawaii

Soil Observation Activity Visually examine the soil on each plate and take notes about each sample. Write down which samples you believe came from the same location. Explain your conclusions