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Resource: used or used up in processes

Hydrogen ions

Appears in 28 processs and 56 steps. Everything below is linked: open a process to see it in context.

Top processes

Cation exchange, pH and soil solution chemistry

8 steps

Pyrite oxidation and acid sulfate weathering

7 steps

Oxygen oxidises pyrite: Fe2+ and sulfate are released, giving about 2 mol H+ per mol FeS2 before Fe2+ is oxidised
Fork: does solution pH fall below about 4 (no carbonate to buffer)
Fe2+ oxidation is rate-limiting; Acidithiobacillus ferrooxidans speeds it by orders of magnitude (about 10^5 to 10^6) below pH 3.5
and 4 more in this process

Mineral weathering and parent material

4 steps

Which weathering reaction dominates
Silicate hydrolysis releases base cations and silica, forms secondary clay
Silicate weathering rate control and CO2 drawdown
and 1 more in this process

Aluminium toxicity and liming of acid soils

4 steps

Sequential soil pH buffer systems

3 steps

Ocean carbon exchange and burial

2 steps

Show 22 more processes

Nutrient availability and leaching

2 steps

Soil sulfur cycling

2 steps

Nitrification-driven acidification of ammonium fertilised soil

2 steps

Soil nitrification, nitrate reduction and nitrogen gas losses

2 steps

Biochar and charcoal in soil

2 steps

Micronutrient availability: pH, redox and plant mobilisation of Fe and Zn

2 steps

Living soil system

1 step

Cation exchange, pH and soil solution chemistry

Roots and rhizosphere

1 step

Rhizosphere pH shifts from ion uptake

Bacteria and archaea

1 step

Sulfur oxidation and reduction

Silicate weathering rate control and CO2 drawdown

1 step

Proton-promoted dissolution of feldspar and mica releases base cations and silica

Soil CO2 and biotic enhancement of weathering

1 step

Carbonic and organic acids acidify microsites at mineral surfaces

Base cation cycling (calcium, magnesium, potassium, sodium)

1 step

Falling base saturation lowers pH buffering, raises Al3+ and hurts root growth

Clay mineralogy and organic matter set cation exchange capacity

1 step

Raising pH ionizes carboxyl and phenol groups on humus, adding negative charge

Redox ladder: sequential electron acceptors in waterlogged soil

1 step

Iron(III) oxides are reduced to Fe2+; pH converges toward 6.5-7.5

Volcanic ash weathering to allophane and imogolite (andic soils)

1 step

Fork: strongly acidic humus-rich soil versus weakly acidic to neutral soil

Pedogenic carbonate accumulation and calcrete formation

1 step

Calcite equilibrium buffers pH at 7.5 to 8.5; phosphate precipitates as Ca phosphates and Fe, Zn and Mn availability falls

Phosphate sorption on Fe and Al oxides and phosphorus availability

1 step

Liming to pH 6 to 7 reduces positive surface charge on oxides and modestly raises phosphate availability

Biofilms and quorum signalling in soil microcolonies

1 step

Alkaline pH and warmth hydrolyse the AHL lactone ring, so signals persist longer in acid, cool soil

Soil inorganic carbon: pedogenic carbonate formation and dissolution

1 step

Acidification from Nitrogen fertiliser, nitrification or acid rain dissolves carbonate and releases CO2

Rhizosphere phosphorus mobilization: phosphatases, organic acids and fast re-sorption

1 step

Roots and microbes exude citrate, malate and oxalate and extrude H+ to desorb phosphate from Fe and Al oxides and dissolve Ca phosphates

Chemical weathering: CO2-driven dissolution and CO2 consumption

1 step

Sulfide oxidation and other acids: weathering that does not take up CO2

Biological weathering by roots, mycorrhizal fungi and microbes (plants speed weathering about 2-10 fold)

1 step

Hyphae and roots exude organic acids (citrate, oxalate) and protons that dissolve minerals

Often found with

Soil solution 16 Plant roots 13 Aluminum 12 Aluminum 10 Sulfate 9 Calcium 9 Oxygen 8 Calcite 7 Iron 7 Clay minerals 6 Soil water 6 Iron oxides 6

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