Soil Analysis Flashcards
soil
degraded material that lies on Earth’s surface
natural soil examples
- rocks
- minerals
- vegetation
- animal matter
natural soil range
can range from 100% inorganic to 100% organic
100% inorganic soil
sand
100% organic soil
peat
artificial/manufactured soil
- glass
- paint
- cinders
soil forensic importance
- easily transferred/transported/unnoticed
- class evidence
- exclusion/inclusion of known samples to questioned sample
where soil samples can be found
- boots
- shovels
- tires
- wildlife
crimes where soil evidence could be useful
- murder
- abduction
- rape
- burglary
- hit & run
variations in soil crime scene
if the soil is indistinguishable for miles surrounding the crime scene, it will have limited value in associating soil found on the suspect with that particular site
collection of soil
collected at various intervals within a 100-yard radius of the crime scene, as well as the site of the crime, for comparison to the questioned soil
how to collect soil of the body & objects
- must not be removed
- each object should be individually wrapped in paper & transmitted to the laboratory
soil collection for standard/reference samples
- only a tablespoon or two of the top layer of soil is collected, placed in individual plastic containers, & labeled according to location
- dry out samples
how is soil analyzed?
- color comparisons
- soil texture & structure
- microscopic examination for debris
- geologically for rocks & minerals
- density gradient tube technique
munsell soil color chart
- typically soil samples are uniformly dried & compared using standardized colors
- 1,100 distinguishable colors
- colors darker when wet
color of soil with low levels of organic matter
lighter
color of soil with high levels of organic matter
darker
low power magnification microscopic examination of soil
investigates presence of contaminants, plants, & animal debris
high power magnification microscopic examination of soil
- can classify rocks & minerals
- 1000s of minerals
high power magnification of 1000s of minerals
- 20 commonly observed in soils (4-5 found together)
- distinguished by polarized light microscopy
which is the largest: sand, silt, clay
sand
which is the smallest: sand, silt, clay
clay
sand size
2.00-0.05 mm
silt size
0.05-0.002 mm
clay size
< 0.002 mm
how to separate sand, silt, and clay
- sieves
- water separation
density gradient tubes
- these tubes are typically filled w/ layers of liquids that have different densities
- when soil is added to the density gradient tube, its particles will sink to the portion of the tube that has a density of equal value
ideal soil pH
5.5-8 is ideal pH range for plant growth
Differential Thermal Analysis
- DTA
- as soil is heated, reactions happen to physical state or chemical reaction
DTA reaction types
exothermic or endothermic
exothermic
reaction with the release of heat
endothermic
reaction with the absorption of heat
Thermogravimetric Analysis
- TGA
- monitor weight change as soil is heated at a constant rate
what is caused by an exothermic reaction?
loss of weight
Cation Exchange Capacity
- CEC
- negatively charged conditioner particles hold & store positively charged cations
- plant roots exchange hydrogen cations for essential nutrients it cannot produce for itself
- co-insides with soil textures
what type of evidence is soil?
class evidence
