Soil Sorption Properties Ability of soil to bind various substances from the dispersion medium Polydisperse system is a mixture of particles of various shapes and sizes mixed with organic substances Coarse Dispersion Colloidal Dispersion Molecular Dispersion > 2 (1)  m (> m) 2 (1)  m – 1nm (10 -6 – m) < 1nm < m

Soil Colloids Mineral Colloids –C–Clay minerals –P–Primary silicates –I–Insoluble phosphates of Al, Fe –P–Polymeric silicic acids (H 2 SiO 3 ) –H–Hydrated oxides (Al, Fe, Mn), sesquioxides Organic Colloids –H–Humic substances –P–Protein, lignin Combined Colloids – Organo-mineral complexes

Electronegative – ACIDOIDS –N–Negatively charged –A–Adsorption of cations –(–(Clay minerals, humic substances, H 2 SiO 3 ) → most of the soil colloids Electropositive – BASOIDS –P–Positively charged –A–Adsorption of anions –(–(hydrates of sesquioxides) Ampholyte – AMPHOLYTOIDES –(–(hydrated polymers of sesquioxides)

Permanent –i–isomorphic substitutions in the crystal lattice of clay minerals –O–Octahedron : Al 3+ → Fe 2+, Tetrahedron: Si 4+ → Al 3+ Variable –p–pH-dependent charge –I–Is formed by the dissociation of carboxyl groups –n–negative charge increases with increasing of soil pH Origin of Soil Colloid Charge

Soil Sorption Complexes – mineral, organic, organo-mineral C.E.C.- (Cation Exchange Capacity) (amount of cations which a soil is able to attract at pH 7, or another suitable pH) –E–Effective (how much available binding sites the soil provides at the given pH) –P–Potential (The highest C.E.C. value which soil can achieve due to pH increase) Soil Sorption Complexes

K+K+ Na + Mg 2+ Ca 2 + H+H+ H+H+ Al 3+ Acid Cations Base Cations Soil Sorption Complexes H+H+

The diverse range of methods Index Ion Method (The sorption complex is saturated by the index ions → index ions are displaced and their concentration is determined) –S–Saturation of sorption complex by index ion –W–Washing of excess ions –D–Displacing of index ion and its determination Mehlich method Bower method Methods for C.E.C. Determination

Bower Determination using AAS washing K+K+ Ca 2+ Mg 2+ H+H+ + CH 3 COONa Na + + CH 3 COOH CH 3 COOK CH 3 COONa (CH 3 COO) 2 Ca + CH 3 COONH 4 NH 4 + C 2 H 5 OH + CH 3 COONa CH 3 COONH 4 Ca 2+ Na + (CH 3 COO) 2 Mg

Methodology Weight 2g of soil 1. Step - Saturation (3x) 2. Step - Washing (3x) 3. Step – Displacement of index ions (3x) 4. Complete filtrate in the volumetric flask by 1M CH 3 COONH 4 5. Measurement of index ion concentration using AAS Add 10ml of 1M CH 3 COONH 4 Let shake for 3 min Centrifuged Add 10ml of 1M CH 3 COONa (use pipette) Let shake for 3 min Centrifuged Empty supernatant from the cuvette into waste 1. Add10ml of 95% C 2 H 5 OH Let shake for 3 min Centrifuged Empty supernatant from the cuvette into waste 2. FILTRATE SUPPERNATANT into 50 ml volumetric flask 3.

Calculation C Na ……Concentration of Na ions (mmol/ml) V……… Volume of the volumetric flask (ml) n……… Weight of soil used for the analyses (2g) mmol(+)/100g

Evaluation C.E.C.mmol(+)/100g Sorption Complex V (%) Very high  30 Fully saturated 100 – 90 High30 – 25Saturated90 – 75 Upper middle24 – 18 Low saturated 75 – 50 Lower middle17 – 13Unsaturated50 – 30 Low12 – 8 Extremely unsaturated  30 Very low  8

C.E.C. Soil TextureC.E.C. mmol(+)/100g Sand2 – 10 Loam20 – 30 Clay40 – 50 Organic SoilUp to 150

Hydrolytic acidity Types of Soil Reaction Actual Soil Reaction → Active Reaction pH H2O Potential Soil Reaction → exchangeable soil reactionpH KCl, E.A. → Hydrolytic acidity Ha Ability of soil to change pH of hydrolytically fissile salt solutions CH 3 COONa

Methodology Weight 40g of soil + 100ml of 1M CH 3 COONa Let the soil with CH 3 COONa shake for 45 min Filter the soil suspension Pipette 50 ml of the soil extract (exactly) into the titration flask, add 3 drops of phenolphtalein Titration by 0.1M NaOH until a light pink color Note the NaOH consumption (a) and calculate the Ha value

Calculation Ha = a x f x M x 5 x 1.75 [mmol/100g of soil] aConsumption of NaOH for titration fFactor of NaOH MNaOH molarities 5Conversion to 100g of soil 1.75 Constant of the incomplete displacement

Ha Evaluation Ha (mmol(+)/100gEvaluation > 1.37Very strong 1.37 – 0.92Strong 0.92 – 0.63Medium 0.63 – 0.29Moderate 0.29 – 0.17Weak < 0.17Very weak

K+K+ Na + Mg 2+ Ca 2 + H+H+ H+H+ H+H+ Acid Cations Ha Base Cations S Soil Sorption Complexes C.E.C. = Ha + S Al 3+

Soil Sorption Complex - Evaluation S – sum of base cations S = C.E.C. – Ha (mmol/100g) BS – base saturation BS = S / C.E.C. * 100 (%)

Status and properties of sorption complex influence Directly: –C.E.C –Soil reaction and character and dynamic of soil reactions –Buffering soil properties Indirectly: –The structural condition of the soil –Biological activity in soil Soil Sorption Complexes

Soil Carbonates Important part of mineral soil component Their presence strongly influences soil properties –Soil buffering ability –Soil structure (coagulation, peptization) –Soil pH –Ensure saturation of sorption complex –Ca humates are favourable components of soil humus Source –PRIMARY – represented in the bottom of the soil profile, towards the surface are decreasing –SECONDARY – presented in topsoil and decrease towards soil bottom –Can be transported downward as Ca(HCO 3 ) 2 and crystallize again New formation- They are formed by transfer and accumulation of CaCO 3 Pseudomycelias, Hard hollow concretions

On the base of CO 2 formation 1.Measuring of pressure change due to production – BAROMETRIC METHOD 2.Measuring of CO 2 volume – VOLUMETRIC METHOD - CALCIMETER TENTATIVE DETERMINATION Soil Carbonates - Determination REACTION% OF CARBONATES Negligible effervescence< 0.3 Weakly effervescence Significant effervescence0-5 Wild effervescence> 5

1.Tentative determination on watch glass 2.Weight 20 g of soil into the developing flask – DECREASE THE SOIL WEIGHT IN THE CASE OF WILD REACTION 3.Fill the liquid in the calcimeter tube up to the mark 0 with the three-way valve (in horizontal position) connecting the calcimeter tubes with atmosphere 4.Fill the HCl into the storage bottle 5.Turn the three-way valve to close the storage bottle (rotate the three-way valve by 180º degrees) 6.Turn the three-way valve to connect the storage bottle and the calcimeter tubes 7.Slowly pour out the hydrochloric acid on soil sample and gently mix 8.Release the pusher to match the liquid level in both tubes 9.Read the carbonates amount from the calcimeter scale. If the soil weight differ from 20g, the carbonates amount has to be converted. 10.Evaluation Soil Carbonates - Methodology

Soil Carbonates - Evaluation