Eksamen Flashcards
(128 cards)
1
Q
mac
When calculating carbon stock, what are the calculations based on?
A
Soil Depth
How deep into the soil are you measuring? (e.g. 0–10 cm)
Carbon Concentration
How much carbon is in the soil? (usually given in %)
Bulk Density
How heavy the soil is per volume (g/cm³)
2
Q
How can tillage affect
- bulk density
- Carbon concentration
A
🔄 What it does:
- Breaks up the soil
- Exposes organic matter to air (oxygen)
🧱 Bulk Density:
- Short-term: Makes soil looser
→ lower bulk density
- Long-term:** Can cause compaction under the surface
→ higher bulk density over time
🌿 Carbon Concentration:
- Speeds up decomposition of organic matter
→ lower carbon concentration
3
Q
How can heavy maschinery affect
- bulk density
- Carbon concentration
A
🔄 What it does:
- Presses down on soil, especially when wet
🧱 Bulk Density:
- Increases compaction
→ higher bulk density
🌿 Carbon Concentration:
- Can reduce root growth and microbial activity
→ lower carbon over time
4
Q
How can adding compost affect
- bulk density
- Carbon concentration
A
🔄 What it does:
- Adds organic material to the soil
🧱 Bulk Density:
- OM is lighter than mineral soil
→ lowers bulk density
- Makes soil more porous/fluffy
🌿 Carbon Concentration:
- Adds carbon-rich material
→ increases carbon concentration
5
Q
How can no/reduced tillage affect
- bulk density
- Carbon concentration
A
🔄 What it does:
- Minimizes soil disturbancel
🧱 Bulk Density:
- Keeps soil structure more stable
- Over time, may reduce compaction
→ lower bulk density
🌿 Carbon Concentration:
- Less disturbance = slower carbon loss
- Encourages carbon buildup at the surface
→ higher carbon concentration
6
Q
How does carbon content affect bulk density?
A
Minerals = heavy & dense
→ high bulk density
OM = Light & fluffy
→ Low bulk density
7
Q
Carbon Mass
A
= just the weight of carbon (e.g. grams)
8
Q
Mass area
A
= g / m²
= g m⁻²
= carbon spread over land
9
Q
Mass volume
A
= g / m³
= g m⁻³
= carbon in a soil layer (e.g. g/cm³)
10
Q
How does water and temperature affect decomposition:
A
Warm and wet speeds up SOC loss
cold/dry or flooded slows it down
11
Q
How MAOM affect SOC persistence
A
POC = carbon hidden inside dirt clumps
MAOC = carbon glued to tiny minerals
- SOC (sorbs) forms ionic, covalent, or hydrogen bonds with:
o Clay minerals
o Oxides of iron (Fe), aluminum (Al), and calcium (Ca) - These bonds are strong and resist microbial decomposition.
👉 This protects mineral-associated organic carbon (MAOC)
12
Q
How Aggregation / Occlusion affect SOC persistence
A
= SOC is physically protected inside clumps of soil
- Microbes and enzymes can’t easily access the carbon inside.
- This limits decomposition and protects carbon from microbial respiration
13
Q
Two ways soil protect carbon
A
Aggregate formation = carbon gets physically trapped in clumps
Mineral sorption = carbon gets chemically stuck to minerals
👉 Both help soil hold onto organic carbon longer
14
Q
What is the key to stable carbon when it comes to clays?
A
Clay & silt = key to stable carbon:
Clay acts like a “sticky sponge” that protects and stores carbon.
o More surface area for chemical bonding with SOC
o Better aggregate formation = physical protection
15
Q
How does Biotic Factors affect SOC
A
- Their activity determines how fast SOC is broken down into CO₂ or transformed into stable forms
- Microbes also help form organo-mineral complexes through their dead biomass (necromass)
16
Q
How can Plant Type and Root Traits affect SOC?
A
Key idea: Roots are a primary source of long-term SOC
more roots = more stable carbon
- Different plants produce different amounts and types of biomass (leaves, roots, exudates).
- Deep-rooted plants (like perennials) push carbon deeper into soil = more stable SOC.
- Roots also release exudates (sugars, amino acids) that feed microbes and promote aggregate formation.
- Grasses vs legumes vs trees = very different carbon input profiles.
17
Q
How does litter quality affect SOC?
A
*Key idea: “Tougher” litter breaks down more slowly and contributes to stable SOC.
Refers to chemical composition of plant residues (leaves, stems, roots).
- High-quality litter : Rich in sugars/proteins → fast decomposition , low persistence.
- Low-quality litter : High in lignin/waxes → slow decomposition , higher stability.
- C:N ratio is a common indicator of litter quality.
18
Q
POC and MAOC
A
POC = carbon hidden inside dirt clumps
MAOC = carbon glued to tiny minerals
19
Q
How are aggreagtes made?
A
- Particles bind:
Clay, silt & humus stick together - Microbial glue:
Fungi & bacteria secrete sticky substances (e.g. glomalin)
- become necromass - Roots help:
- exude carbon
- physically entangle particles (fungi too)
20
Q
What can negatively affect aggregates, why?
A
Moisture
tillage
freeze thaw
21
Q
How does microbial communities affect SOC
A
Microbes drive both carbon loss (respiration) and carbon stabilization (via residues and byproducts).
- Microbes (bacteria, fungi, actinomycetes) break down organic matter.
- Their activity determines:
- decomposition rate
- SOC formation
- They also produce byproducts that can become stable SOC.
- Diversity and function of microbial communities matter:
o Fungi promote aggregate formation.
o Some microbes can form carbon compounds that resist decay.
22
Q
How different plant roots affect SOC
A
Key idea: Root systems are the primary pathway for long-term SOC input, especially below 30 cm depth.
o Grasses (e.g. prairie species) → high root biomass, deeper carbon input.
o Legumes fix nitrogen → boost microbial activity and decomposition.
o Perennials vs. annuals → longer vs. shorter carbon input durations.
23
Q
Another name for Megatonne
A
Metric tonne
24
Q
Gt, number
A
= Gigatonne
= Giga × tonne
= 10⁹ tonne
= 10⁹ × 10³ kg
= 10⁹ × 10³ × 10³ g
= 10¹⁵ g
= Pg
= Petagram
25
Pg
Gt
26
Hectare
10 000 m²
27
Decare
1 000 m²
28
Are
100 m²
29
Acre
4 047 m²
30
NPP
= Net Primary Production
= GPP - Respiration
31
POM =
Particulate organic matter
- Young/fresh Carbon (OM)
- Tiny bits of decomposing OM
- Breaks down quickly
- Fastfood
- Does not keep Carbon in soil for very long
- protected inside lumps of soil
32
MAOM
Mineral-Associated OM
- Old/stable Carbon
- Stuck to tiny soil minerals
- Beaks down slow
- Stores carbon in the soil for a long time
33
What is the "**4 per mille" (4 ‰)** soil carbon initiative?
🌱 Increase soil organic carbon (SOC) stocks by 0.4% (or 4‰) per year.
34
What is pF 2.0?
Field capacity
35
pF 0 - 2.0
Water that is always drained by gravity after the soil has been saturated
Also effective porosity
This is the volume of pores that are connected and allow gravity to drain the soil
36
pF 2.0 - 4.2
Available water
Field capacity - wilting point
37
pF 4.2
Wilting point
The soil is too dry for plants to be able to use the water
38
pF 0
Soil if fully saturated
39
What two factors affect satureated water flux?
40
Constant head method
(transport)
Keep water volume above the soil constant
41
Big, visible, deep channels or ditches in the land made by running water
Gully
Think: big cracks or mini-valleys in farmland or slopes.
42
Which can be fixed with plowing, gully or rills?
Rills
43
What caues gullies to form?
Gullies form when:
- ↑ Surface runoff (rainfall, snowmelt)
- ↓ Crop cover (soil is bare)
- ↑ Steep slopes
- Poor structure
- Loose sand or fine silts
- Too much surface runoff (heavy rain or fast-flowing water)
- Soil is bare (no plants or roots to hold it together)
- The slope is steep (gravity speeds up water)
- Soil is easily eroded (like loose sand or fine silt)
How:
- Rain hits the ground and starts flowing downhill.
- Water picks up speed and starts cutting into the soil.
- Small channels (rills) form.
- If not stopped, they grow deeper → gullies form.
- Gullies get bigger over time from more water flow and erosion.
44
Hva er jordarbeidingserosjon?
Når jord flyttes eller blir mer utsatt for erosjon fordi den løsnes av jordbruksredskaper — spesielt i skrått terreng
- Traktor med plog eller harv går gjennom åkeren.
→ Jorda kan flyttes fysisk av redskapene (for eksempel nedover en skråning)
→ Gjør jorda mer sårbar for regn og vind etterpå
På skrått terreng, kan løs jord skyves nedover litt for hver gang.
Over tid → tap av topplag og mer erosjon i nedre del av feltet.
45
Hva er konsekvensene av jordarbeidingserosjon på dyring av mat?
Mister fruktbar jord
Mer erosjon senere (f.eks. ved regn)
Ujevn næringsfordeling i jorda (mer næring nederst i åkeren)
Kan føre til lavere avlinger
46
🛑 Hvordan kan man redusere jordarbeidingserosjon?
Pløy på tvers av hellingen (konturpløying)
Bruke redusert jordarbeiding eller ingen jordarbeiding (no-till)
Ha planterester igjen på jordoverflaten
Terrassering i bratt terreng
47
Measures that can reduce effects of erosion:
- Protect soil surface from particle displacement
- Crop cover
- Water waysLage forsenkninger der vannet samler seg
- Increase soil infiltration
- Sub-surface piping
- Capture and retain soil particles & nutrients
- Buffer zones
- Sedimentation ponds (som v/Årungen)
48
How does bufferzones help reduce off-site issure with erosion?
- Slows down water
- Traps sediment
- Roots hold soil together
- Improves water infiltration
- Slower water has more time to soak into the ground instead of running off.
- Less runoff = less erosion.
- Reduces nutrient and pesticide runoff
- Buffers can also trap chemicals and nutrients before they reach water bodies — bonus environmental benefit!
49
Examples of unstable winter conditions
- Some crops are poor erosion protectors
- Freezing/thawing: Impacts aggregate stability
- Rainfall on partly frozen soil → High erosion
50
CEC is operationally defined, with different extractants:
- 1 M NH4Ac (buffered at pH 7)
- 1 M NH4NO3 (neutral salt, measured at soil pH)
Bruker ulike løsninger for å "måle" aciditet basert på hvor man er i verden
**NH4Ac is also used to test biavailable fraction of trace metals**
51
What is soil acidification?
* ↓ Base cations (uptake or leaching):
* ↓ pH
* ↓ Acid neutralising capasity
* ↓ Base saturation (CEC)
* ↑ Exchangeable acidity (Al³⁺ & H⁺)
* ↑ Oxidation
52
At low pH phosphate precipitate with
- Iron
- Aluminium
53
At high pH phosphate precipitate with
Calcium
54
How much of the reactive nitrogen is organic?
57 %
55
Anthropogenic N-sources
- Haber - Bosch
- Fossil fuel combustion sources
- Cultivating N-fixating plants
56
How much of annually converted nitrogen is natural?
Ca. 12 %
57
What is it called when there is a** temporary N depletion**, because **N is locked up in microbial biomass**?
**Nitrogen immobilization**
58
Which four nitrogen processes consume acids?
- Reduction of N
- Denitrification
NO₃⁻ + H+ → N₂
- Nitrogen fixation
N₂ + **8H⁺** → NH₄⁺
- Biological uptake of NO₃⁻
- Ammonification (Mineralization)?
59
What causes dead zones?
Eutrophication
Nutrients cause massive algal blooms.
When the algae die:
- They sink to the bottom.
- Bacteria break them down, using up oxygen in the process.
- This leads to oxygen-depleted waters.
- Fish, crabs, and other marine life either flee or die.
- Disrupts marine ecosystems.
60
What are Coastal dead zones?
Areas in oceans or large lakes near coastlines where **oxygen levels in the water become so low that most marine life cannot survive**.
61
What is **Cross-shelf exchange**?
How stuff moves back and forth between the coast and the open sea.
62
What is **Permanent O₂ minimum zone (OMZ)**?
A **layer in the ocean where the concentration of dissolved oxygen (O₂) is at its lowest** compared to the layers above and below.
Can create **stressful or uninhabitable environments** for many marine organisms
63
What is the risk with dead zones and Permanent O₂ minimum zone
They are expanding, and may cause long term / semi-permanent changes.
64
How much of N used by plants come from soil organic N?
60 % <
Less mineral N, the higher N efficiency
65
What is sodic soils?
Why is it problematic?
High sodium levels relative to other cations
Low soil permeability
Compacted or hard soil:
Crusting
Nutrient imbalance (Na2+ competes)
Osmotic stress
Toxicity
66
Hvilket ion av antimon (Sb) er mest giftig?
Sb (III) > Sb (V)
67
Three reasons Cr(VI) more toxic than Cr(III)
Cr(VI) ↑ mobile
Cr(VI) ↑ readily taken up by organisms
Cr(VI) = strong oxidizing agent
68
Examples of 7 cationic metals
Al²⁺
Cd²⁺
Cu²⁺
Fe³⁺
Ni²⁺
Pb²⁺
Zn²⁺
69
What amendmens types can be source of trace metals?
- Amendments
- Sewage sludge/biosolids
- Inorganic fertilizers (rock)
70
At what pH does led (Pb) have the lowest solubility?
pH 10
71
At what pH are trace elements normal least soluble?
pH 6-10
72
At what pH is iron (Fe) least soluble?
pH 8
73
How does complexation affect mobility of elements?
Enhances mobility
74
Which trace elements are important when testing?
As – Arsenic
Cr – Chromium
Cd²⁺ – Cadmium(II) ion
Cu – Copper
Hg²⁺ – Mercury(II) ion
Ni²⁺ – Nickel(II) ion
Pb²⁺ – Lead(II) ion
Zn²⁺ – Zinc(II) ion
75
Law of mass action
- How the speed of a chemical reaction depends on the concentrations
Slower < [trace element ]= faster reaction (up to a point)
It helps predict how chemical reactions will behave.
Used in chemistry to understand equilibrium and reaction rates.
76
Three ways trace elements can sorb to surfaces:
- Surface complexation
- Ion exchange
- Specific binding
77
Which soil colloids/particles have **permanent charge** and which do not?
2:1 Silicate clay minerals
Not
- 1:2 Silicate clay minerals
- Humus
- (Hydr)oxides
78
Which clay minerals have high activity (CEC)?
Why?
Which do not?
2:1 Silicate clay minerals
- ↓ weathered
- ↑ effective surface area
1:1 Silicate clay minerals
- ↑ weathered
- ↓ effective surface area
79
How can clay be used when it comes to pollutants? What side effects do we have to consider?
- Add clay to sorb cations
- Makes soil more dense
80
Name of something that **can act like both an acid and a base**, depending on the situation.
Amphotheric
(hydr)oxides
81
The point where the amount of a trace element sticking to a surface suddenly jumps.
Adsorption edge
This happens when the pH of the solution changes, making the surface (like soil or metal oxide) more likely to attract and "stick" the trace element.
82
The link between:
- Electron activity
- Redox potential
- How many electrons are available or free to participate in a redox reaction.
- A measure of how likely those available electrons are to actually undergo a certain redox reaction, due to a substances tendency to gain/lose electrons.
83
Living organisms change the chemicals they come into contact with
Biotransformation
A substance is broken down, modified, or transformed by a living organism
- Usually involves enzymes
84
Saturated hydraulic conductivity (Ks, Ksat)
A measure of a **soil's ability to transmit water when the soil is fully saturated with water**
The rate at which water can move through the soil when saturated
85
pF curve
soil water retention curve
86
Leaching is increased by
- Solubility
- Low SOM
- Sandy soil
- Many macropores
- High rainfall periods?
87
Why is the hydraulic conductivity higher in saturated soils, than in unsaturated soils?
When there is air in the soils (unsaturated), capillary forces are working on the water, slowing down its ability to move freely in the soil.
88
Pugge: **Important factors for biodegradation**
1. Microbial community
2. Contaminant structure
3. Contaminant concentration
4. Sorption/desorption
5. Environmental factors
a. Redox conditions (aerobic/anaerobic)
b. pH, temperature, salinity
89
PAF
Potentially affected fraction (of species)
90
PEC/PNEC < 1
Low to no risk
- Predicted Environmental Concentration
- Predicted No Effect Concentration
91
PEC/PNEC ≥ 1
Potential risk
- Predicted Environmental Concentration
- Predicted No Effect Concentration
92
MTR
Maximum Tolerable Risk
- 95 % are protected
- 5 % die
93
SR
Severe risk
50 % protected (HC50 / LC50)
94
50 % protected
Severe risk !!
HC50 or LC50
95
Stepwise risk assesment:
1. **Source analysis**
- Identify and describe the pollution
2. **Transport analysis**
- how pollutants move from the test site to other environments
3. **Recipient analysis**
- who/what may be exposed and at risk.
96
Passive samplers
Measuring the bioavailable fraction of pollutants, **without the need for pumps or power sources**.
- Rely on diffusion or partitioning (natural processes)
- Focus on the dissolved or gaseous phase—what is most relevant for exposure and toxicity
- Mimic how pollutants are taken up by organisms
- Provide time-integrated measurements (vs. snapshot samples)
97
Two main problems with risk assesment
- Safety factors are very uncertain
- Kd: Solubilty is very uncertain
98
Why do we need safety factors in risk assesment?
We have few data
There may be other species in the biota
99
"Equilibrium" passive samplers
Uses thin plastic strips to sorb pollutants (various thickness)
100
Passive samplers are useful for
Providing estimates of contaminant concentrations water / freely dissolved contamination.
101
# ****
Xenobiotic compounds
Compounds that are foreign to the biological system - not naturally produced by living organisms
102
Which elements make organic compounds soluble?
N, O, S
103
Compounds fate in enviroment is determined by (compound specific, 4 points)
- Density
- Vapour pressure
- Solubility
- Octanol-water distribution
104
Air-water partitioning
Distribution of a substance between the gas phase (air) and the liquid phase (water) at equilibrium
105
Compounds fate in enviroment is determined by:
- Air-water partitioning
- Density
- Degradation
- Octanol-water distribution
- Solubility/sorption
- Vapour pressure
106
Incomplete biodegradation is caused by:
(8 reasons)
- Appropriate enzym is not present
- Partially degraded molecules are more complex or stable than parent compount
- Too low / high concentrations of OP
- High sorption
- Low solubility
- Level of microbial activity
- Steric hindrance (branching or functional groups)
- Cometabolism
107
What is cometabolism?
**Degradation that happens when the organism is doing something else.**
- Not a nutrient or energy source for the microbe
- May only partially break down the pollutant
- Primary function: Side-effect of microbial metabolism
- Pollutant use: Not used for energy or growth
- Enzymes involved: Broad-specificity (can act on structurally similar pollutants; often oxygenases)
108
Which biodegradation reaction provide energy for the organism?
Energy sources: Oxidation of organic molecules
109
Slower degradation because reaction sites are blocked by branching or functional groups.
What is this called:
Steric hindrance
The hindrance increase as size of functional groups increase
110
Two names for reduction of Cl containing compounds
- Reductive dechlorination
- Dehalogenation
111
Volatilization rates depend on:
- "Internal" properties of the chemical
- Concentration
- Soil properties
- Environmental factors
112
"Internal" factors that make compounds likely to volatilize
- Small in size
- Less polarity & polarizability
- Less soluble
- Higher vapor pressure
- Low boiling point
113
How does soil properties increase (↑) volatilization?
Lots of AIR
↓ Organic material
↓ Moisture
↑ Sand
114
How does environmental conditions increase (↑) volatilization?
Lots of AIR
↓ Humidity (moisture in air)
↑ Temperature
↑ Wind
↑ Sun
115
Dioxin
116
How are Microaggregates formed?
Microaggregates (<250 µm):
Formed mostly by:
- Clay-organic matter interactions
- Microbial exudates (e.g. bacterial polysaccharides)
Soil organisms involved:
Bacteria (produce binding agents)
Fungi (start structure but less dominant here)
Soil organisms help, but physical-chemical processes dominate.
117
How are macroaggregates formed?
Macroaggregates (>250 µm):
Formed by:
- Binding of microaggregates + organic matter
- Soil organisms are key players:
Fungi (especially mycorrhizae) → hyphae penetrate thoughts microaggregates & OM, creating a "net"
Roots → physically bind microaggregates and OM + release exudates
Earthworms & fauna → mix and structure soil
(Earthworms ingest soil → Mix it in their gut and excrete it as casts
Many soil invertebrates secrete sticky compounds → temporary binding agents)
118
Soil washing, mechanical
Physical Separation Methods
(Used in mineral processing – sorting stuff based on physical traits)
1. Density separation
Heavy vs. light materials
Tools: jigs, shaking tables
2. Size separation
Big vs. small particles
Example: sieving or screening
3. Mechanical screening
Like a filter or sieve – lets small stuff through
4. Hydrodynamic classification
Uses water and flow
Tool: hydrocyclones (spin things to separate by size or weight)
5. Surface property separation
Based on how surfaces behave in water/air
Example: flotation (bubbles stick to some materials and lift them)
6. Magnetic separation
Uses magnets to pull out magnetic stuff
119
How does Chemical extraction cleans soils
Chemical extraction cleans soils by removing contaminants, especially metals and other inorganic pollutants, using acids or chelating agents. Here’s how each method works:
1. Acid extraction
Acids like HCl, H₂SO₄, and HNO₃ dissolve metal-containing minerals and displace metal ions bound to soil particles.
This releases metals (like lead, cadmium, arsenic) into a solution, from which they can be removed.
Effective especially for heavy metals that are weakly adsorbed or present in carbonates or oxides.
Mechanism:
Lower pH breaks down mineral structures and increases metal solubility.
Protons (H⁺) compete with metal ions for binding sites.
2. Chelating agents (e.g. EDTA)
Chelators form stable, soluble complexes with metal ions.
EDTA binds metals like Pb²⁺, Cu²⁺, Zn²⁺, etc., pulling them off soil particles and keeping them in solution.
Mechanism:
Chelators wrap around metal ions and form a ring-like structure (chelate complex).
Prevents metals from re-binding to soil or precipitating out.
Summary:
Both methods mobilize and extract pollutants from soil particles, making it possible to remove contaminants through washing or flushing, thus "cleaning" the soil
120
How to cover tailings
Proposed Fix: Covering Tailings – Folldal
What's the problem?
Tailings (mining waste) are spread over a big area.
These tailings can make acid – especially near mine shafts (high APP = Acid Producing Potential).
Mine water causes secondary minerals to form.
Rain/runoff carries pollution to the Folla river.
River has about 10 units of copper (too high).
Goal:
Stop the pollution at the source.
Reduce harmful water leaking out (leachate) by 60–90%.
Solution:
Cap (cover/seal) the tailings to block oxygen and water.
This slows down acid production and metal release.
121
Different soil amendments (7)
122
What chemicals are good for binding lead?
Which do notm
Good:
PO₄ (phosphate) – good for reducing lead solubility
CO₃ (carbonate) – also helps bind lead
Bad:
SO₄ (sulfate), OH⁻, H₂O – have varying effects, sometimes increase solubility
123
What is called when plant covering are used to stabilize a soil and keep pollutants trapped/stabilized?
Phytostabilization
124
What is this called: Using plants to absorb harmful metals from soil into their roots and leaves.
Phytoextractation
125
Difference between
Linear
Freundlich
Langmuir
Linear isotherm:
Straight line.
More stuff = more adsorption (no limit).
Freundlich isotherm:
Curved line.
Good at low concentrations, but no clear max.
Langmuir isotherm:
Curves and levels off.
Has a max limit (like seats on a bus).
---
Summary:
Linear = simple and endless
Freundlich = flexible but no max
Langmuir = limited spots, fills up
126
List of how to test for bioavailability
🧪 Shake & See = Leaching
🌊 Mild Rinse = Weak extractants
🧲 Metal Magnet = Chelators like EDTA
⚡ Catch the Freebies = Free ion measurement
🧻 Metal Sponge = DGT
🧠 Virtual Soil Science = Models
🧪 Peel the Onion = Sequential extraction
🌱 Let It Grow = Plant uptake
127
Explaining list of how to test for bioavailability
🧪 1. **Leaching Tests** – "Shake & See"
What: Mix soil with a liquid to see what metals come out.
Why: Mimics rainwater washing through soil.
Types:
- Batch tests: Mix soil + solution in a jar, shake, then test the liquid.
- Column tests: Pour liquid through a soil column and collect what's drained.
🌊 2. **Weak Extractants** – "Mild Rinse"
What: Use gentle solutions to get the easily available metals.
Why: These pick up metals plants might absorb directly.
Examples:
Water 💧
CaCl₂, NaNO₃, NH₄NO₃ 🧂
Citric or acetic acid 🍋
🧲 3. **Chelating Agents** – "Metal Magnet"
What: Stronger chemicals that "grab" metals out of soil.
Why: Simulates what happens in the root zone when plants release similar compounds.
Examples: EDTA, oxalate 🧪
⚡ 4. **Direct Measurement of Ions** – "Catch the Freebies"
What: Measure free-floating metal ions (the most available form).
Tools:
Ion-selective electrodes
Stripping voltammetry
Why: Tells you what's immediately ready to be taken up.
🧻 5. **DGT (Diffusive Gradients in Thin Films)** – "Metal Sponge"
What: A little device that soaks up metals over time.
Why: Mimics plant roots pulling metals out of the soil.
🧠 6. **Computer Models** – "Virtual Soil Science"
What: Use software to predict how metals behave.
Why: Helps understand how metals move and change form in soil.
Examples: MINTEQ, PHREEQC, WHAM
🧪 7. **Sequential Extraction** – "Peel the Onion"
What: Remove metals step-by-step using different chemicals.
Steps: Targets metals in different "layers" or forms in soil.
Warning: Not perfect—can mess with metal forms while extracting.
🌱 8. **Real-World Testing (Plants!)** – "Let It Grow"
What: Grow plants in the soil and measure metal uptake in roots and shoots.
Why: Ultimate proof of what’s truly bioavailable.
128
What it shows:
This diagram explains how metals in soil can or cannot be taken up by plants.
---
Layers (from bottom to top):
1. Soil matrix (bottom)
Metals here are locked away in crystals or stuck forever = not available to plants.
2. Mineral surface
Some metals are stuck on soil particles:
Very strongly adsorbed = barely moves
Weakly adsorbed = might move into water → Maybe available depending on conditions.
3. Pore water (middle)
Metals here are dissolved in soil water:
Free ions = easiest for plants to take
Complexed with organic or inorganic stuff = still available → This is what plants can absorb through roots.
4. Root surface → Plant (top)
Metals go through the root membrane, then:
Move around the plant
Stored or cause damage → This is accumulation or toxic effect.
---
Main idea:
Only a small part of total metal in soil is actually bioavailable = plants can take it up.
Thick arrows show the most important paths.
---
Bonus tip:
If you're trying to clean soil with plants (like phytoextraction), the metals need to be in the pore water, not stuck deep in the soil matrix.
