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(Upload on February 5 2017) [ 日本語 | English ]

Water ()






Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

[ water potential | pH ]

Water for life (生命にとっての水)
Plants live with water because of photosynthesis (光合成)

→ Plants [ algae | moss | fern | seed plant ]
→ Physiology [ water culture , water stress ]
→ Ecology [ hydrosphere | wetland ]

索引

Water transportation (水移動)



(Slatyer & Taylor 1960)

Water potential (水ポテンシャル)

Quantifier: ψ, or ψw
Dimension: L-1MT-2
Unit: Pa

Water transport: from high to low water potential →
The following equation is ture whenever water transportation occurs from soil to air through plant

ψl < ψx < ψr < ψs
← ← ← ← ← ←
l: leaf, x: xylem, r: root, s: soil

Permeability (浸透性)
Terms: permeable, adj 浸透(透過)される, permeate, vt -に浸透する

Deficiency and evapotranspiration (etp)

Ideal

water potential water potential

Actual

water potential water potential
-ψπ: osmosis potential, -ψp: water potential, -ψ: equivalent state

Active transport (水能動輸送)

Materials: Barley roots
active transport
active transport

pH (potential of hydrogen, ピーエッチ)


A measure of the acidity or basicity of an aqueous solution, expressed by the concentration of hydrogen ion
Def. ionic product of water (水のイオン積), Kw ≡ [H+]·[OH-]

→ depending only on temperature (T)
Ex. room temperature → Kw ≈ 1.0 × 10-14

T (°C) → Kw
0 → 0.113 × 10-14
10 → 0.292 × 10-14
20 → 0.681 × 10-14
25 → 1.008 × 10-14

Def. Hydrogen-ion exponent (水素イオン指数), pH = -log[H+]
= Potential hydrogen, or power of hydrogen
pH is defined as minus the decimal logarithm of the hydrogen ion activity in a solution. So, pH is a dimensionless quantity.

pH = -log10(H+) = log10(1/H+),

where H+ is the activity of hydrogen ions.
As wall as pH, we can define pOH = -log[OH-], and pKw = -logKw
→ pKw = pH + pOH = 14
Ex. Pure water: H2O ⇔ H+ + OH- → [H+] = [OH-] = 10-7

K = [H+][OH-]/[H2O] = 1.8 × 10-16 (mol) = 55.5 (mol)

[H+][OH-] = 1.8 × 10-16 × 55.5 = 1.0 × 10-14, [H+] = [OH-] = 1 × 10-7 ∴ pH = log[H+] = 7

    ------------------------
    pH  [H+]   [OH-]
    ------------------------
     0  100    10-14  acidic
     1  10-1   10-13  ↑
     2  10-2   10-12
     3  10-3   10-11
     4  10-4   10-10
     5  10-5   10-9
     6  10-6   10-8
     7  10-7   10-7   neutral
     8  10-8   10-6
     9  10-9   10-5
    10  10-10  10-4
    11  10-11  10-3
    12  10-12  10-2
    13  10-13  10-1   ↓
    14  10-14  100    alkali
    ------------------------
Def. H+ activity (プロトン活量)

CH+ = r[H+]

r: activity coefficient (活量係数)
fA: [H+]↑ → r = 1, [H+]↓ → r > 1

Ex. 0.1 M HCl: -log[H+] = 1.09 = log-1(2.91) = 8.1 × 10-2, r = 0.81

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