2. The Lithosphere
The lithosphere
• most superficial layer of Earth
• solid and molten portions of Earth
Soil
• uconsolidated material covering Earth surface
• mixture of particles derived from disintegrated rock
• natural medium for plant growth and a habitat for a number
of animals
• plays a role in water circulation
3. Soils have five key roles to play:
1. Support plant growth;
2. Reserve and purify water;
3. Function as nature's recycling systems;
4. Provide habitats for living organisms;
5. Supply engineering materials and building
foundations
4. Soil’s main components:
• minerals of different sizes (clay, silt, & sand)
• organic materials from the remains of dead plants
and animals
• open space that can be filled with water and air
(pore space)
• plant roots and other living organisms
5. Plant nutrients
Elements considered necessary for optimum
growth, development and food values in
plants.
Obtained from water and air: carbon, hydrogen,
oxygen.
• macronutrients: nitrogen, phosphorus, potassium,
calcium, magnesium and sulfur.
• micronutrients: iron, manganese, copper, zinc, boron,
chlorine and molybdenum.
6. Justus Liebig's law of the minimum
The growth of any plant is limited most by the
essential plant growth factor that is present in
the least relative amount.
7. Trophic cycle - heavy metals
• Soil - a basic element in the trophic cycle (soil-plant-
animal-human)
• Soil contaminated by heavy metals from agricultural
and industrial wastes produces unhealthy food.
Heavy metals enter the food chain and are consumed
by human beings
• Toxic metals do not degrade, but remain in a
potentially toxic form as long as they reside in the
soil
8. Lead contamination - soil
• Lead particles are deposited in the soil from:
– flaking lead paint,
– incinerators (and similar sources),
– motor vehicles that use leaded gasoline.
– waste disposal.
9. Lead contamination
• Lead ions (PbOH+, PbOH4--) are taken by plants from
the superficial layers of soil and become deposited in
various parts of the plants (stems, roots, leaves).
Toxic lead influence on plants is expressed by dark-
green colouring, fading, root shortening,
photosyntesis disturbances and water circulation
perturbations.
• Humans get intoxiacted from eating the lead-loaded
plants. Besides being absorbed by GI tract lead can
also enter human body via respiratory tract (dust/
pollution).
10. Lead poisoning
• Long term exposure - lead absorption - cumulation in the human body
(bones, soft tissues). The most exposed organs: liver, kidneys, bone
marrow, brain.
• Symptoms of long-term exposure to lower lead levels – anaemia, damage
to the nervous system (impaired mental function), appetite loss,
abdominal pain, constipation, fatigue, sleeplessness, irritability and
headache.
• The characteristic signs of long-term exposure - blue lead line on gum
margins, greyish skin tone.
• Short-term exposure to high levels of lead - vomiting, diarrhea,
convulsions, coma or even death.
• Even small amounts of lead can be harmful, especially to infants, young
children and pregnant women.
11. Lead poisoning in children
• Lead exposure is most serious for young children because
they absorb lead more easily than adults and are more
susceptible to its harmful effects. Preschool-age children and
fetuses are usually the most vulnerable segments of the
population for exposure to lead. Among children, those in the
2-3 year-old age bracket may be most at risk for exposure to
lead-contaminated soil.
• Even low level exposure may harm the intellectual
development, behavior, size and hearing of infants. During
pregnancy, especially in the last trimester, lead can cross the
placenta and affect the unborn child. Female workers exposed
to high levels of lead have more miscarriages and stillbirths.
12. Lead poisoning in children
• Studies on the effects of lead in children have
demonstrated a relationship between exposure to
lead and a variety of adverse health effects:
– impaired mental and physical development,
– decreased heme biosynthesis,
– elevated hearing threshold,
– decreased serum levels of vitamin D.
• The neurotoxicity of lead is of particular concern
because neurobehavioral effects, such as impaired
academic performance and deficits in motor skills,
may persist even after Pb blood levels have returned
to normal.
13. Cadmium soil contamination
• Cadmium compounds are primarily released into the
environment:
• by copper, lead and zinc smelters
• municipal incinerators
• by the application of phosphate fertilizers or sewage sludge to
soils.
• the most common uses of cadmium compounds are
in batteries, metal plating, pigments and plastics.
• inadequate disposal of waste containing cadmium at
industrial sites in past decades has contaminated the
lands and groundwater
14. Cadmium poisoning
• Small amounts of naturally occurring cadmium are present in many foods.
• Increased levels may be carcinogenic - lung cancer is one potential result
of chronic inhalation of fine-particle cadmium compounds, particularly
cadmium oxide, which readily dissolves in the body.
• Ingestion of the compounds in food results from the fact that plants and
fish absorb and retain cadmium, and hazardous levels can be reached
when consuming food from areas where cadmium contamination has
been generated at industrial sites or by the use of phosphate fertilizers.
Adverse health results from long-term, high-level ingestion of cadmium
include kidney damage and kidney stones, and debilitating effects on
bones and the skeletal structure.
15. Nuclides
• Long-lived components of a nuclear release may enter food
chains posing a risk to human health:
– caesium-137 with 30 years half-life,
– caesium-134 with 2 years,
– strontium-90 with 28 years half-life,
• As a result of atmospheric nuclear tests, strontium-90 is
dispersed in soil. Because of its chemical similarity to calcium,
it is readily taken up in the tissues of plants and animals; it
may enter the human food supply, mainly in milk. Particularly
dangerous for growing children - easily deposited in the
bones, believed to induce bone cancer and leukemia.
• All the nuclides may cause chromosomal abberrations
16. Soil pathogens
• Soil - a reservoir of many pathogens
• The main sources:
– communal wastes
– application of biowaste materials
– composting the organic fraction
• Soil pollution from bio-medical waste is caused due
to infectious waste, discarded medicines, chemicals
used in treatment and ash and other waste
generated during treatment processes
17. Pathogenic bacteria present in soil
• Escherichia
• Enterobacter
• Bacillus spores (infection with B.anthracis can adopt
skin, pulmonary or enteric form)
• Clostridium (C.tetani or C.perfringes produce toxins
especially affecting the nervous tissue).
18. Sanitary evaluation of soil
• Chemical methods (determination of chlorine ions, organic
and non-organic natrium)
• Bacteriological methods (general number of bacteria,
number of spore-forms, of nitrificating and thermophilic
forms)
• In addition evaluation of Escherichia coli titer (indicates
recent contamination), Enterobacter aerogenes titer (for
older contamination), and Clostridium perfringens spore
forms (the oldest contaminations) might be performed.
19. Coli-Titer/ Cl. Perfringens Titer
• measurement scales to determine bacteriological qualities of
soil
• Coli / Cl. pefringens titer - the minimum amount of soil in
which E. coli bacteria/ Cl. perfringens spore forms can be
detected
• also the estimated quantity of bacteria in 100 cm3 of the
dried soil sample
20. Bacteria present in soil
• permanently present (nitrificating bacteria and
Actinomyces)
• appearing only following decomposition of organic
matter
21. Streptomyces
• filamentous bacteria of the family Streptomycetaceae
• single-celled and small
• have filamentous structures (mycelia) like fungi
• no nucleus (procaryota)
• important roles in the decomposition of organic matter
• produce antibiotics (S. griseus makes streptomycin, S.
venezuele – chloromycetin, S. aureofaciens – aureomycin
• some species pathogenic for humans
23. Soil Fungi
• very important in the soil ecosystem
• their decomposition of organic matter releases plant nutrients
into the ecosystem for other organisms to use
• particular fungi form mycorrhizal associations with plant roots
- plants provide the fungi with food
• some fungi are important in other ways: mushrooms are
important food products; many molds, like Penicillium,
produce useful materials such as antibiotics. Fungal hyphae
also play a role in the developement of soil structure
24. Dermatophytes - the main group of
human pathogenic fungi
• capable of infecting animals and humans.
• species originating from the soil are called geophilic.
• keratinophilic and capable of invading keratinized tissues –
skin, hair and nails and causing tinea.
25. Hair perforation test
• Used to detect the presence of dermatophytes
in soil
• Since dermatophytes are able to perforate
hair in vitro, sterilized human hair are placed
in a sample of soil.
• Hair are examinated microscopically after
three weeks incubation for formation of hair
perforators and the presence of micro- and
macroconidia.
26. Dermatophytes - morphology
• on Sabouraud’s agar dermatophyte’s colonies are
downy, and of white colour, some of them produce
brownish pigment diffusing into the medium.
• microscopic examination:
• unpigmented, mostly tear-shaped, smooth-walled, one
celled microconidia
• cigar-shaped and spindle-shaped, multicelled
macroconidia
• spirally twisted hyphae
• chlamydospores
28. Fungi found in soil
• Histoplasma,
• Blastomyces and
• Sporotrichum genera
• Cryptococcus neoformans (cause of organ or
general cryptococcosis, often resulting in
death).
