SOIL ANALYSES PROPOSED BY MOCA
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Méthodes |
Description |
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NF X31-516 |
Granulométrie : % d’éléments grossiers |
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NF X31-107 Méthode interne |
Texture : Détermination du pourcentage de sable, de limon et d’argile :
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PAF à 500°C |
MO : Détermination de la teneur en matière organique |
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NF ISO 11464 NF ISO 18512 |
Prétraitement des échantillons en vue des analyses physico-chimiques Lignes directrices relatives au stockage des échantillons |
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NF ISO 11465 |
Détermination de la teneur pondérale en matière sèche et en eau résiduelle |
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NF ISO 10390 |
Détermination du pH (pH H2O et pH KCl 1M) |
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NF ISO 11265 |
Détermination de la conductivité électrique spécifique |
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NF ISO 10694 NF ISO 13878 NF ISO 15178 NF ISO 11261 |
Mesure élémentaire du C, N, S et ratio C/N
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NF X31-108 NF ISO 11260/14254 Méthode interne |
Capacité d’échange Cationique (Bases échangeable, acidité d’échangeable et taux de saturation) :
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Méthode interne NF ISO 12789-1 NF ISO 12789-2 NF ISO 12789-3 NF ISO 12789-4/5 |
Extractions sélectives
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NF ISO 14869-1 NF ISO 14869-2 Méthode interne Méthode interne NF ISO 12914
NF ISO 17586 NF ISO 11466
NF ISO 22036 |
Analyses chimiques élémentaires par ICP : Analyses totales, Eléments traces (ETM), Oligo-éléments, terres rares et éléments spécifiques
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Méthode de Dyer
Méthode de Joret-Hébert
Méthode de Olsen
Méthode de Lakanen et Irvio Méthode interne |
Analyses chimiques mono-élément par ICP : exemple du Ptotale Porganique , Pinorganique et Passimilable
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Méthode interne Méthode interne Méthode interne |
Analyses organiques :
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Physical and chemical analyses
Coarse particles
The coarse particles (i.e., gravels) are the mineral constituents with a dimension greater than 2 mm. They constitute the mineral reservoir in the soil and provide important roles, such as soil permeability, soil warming... The proportion of coarse particles is determined by gravimetry after passing through sieves of different mesh sizes.
Soil texture (clays / silts / sands)
Soil texture corresponds to the distribution of <2 mm-mineral particles: coarse sands (>200 µm), fine sands (between 50 and 200 µm), coarse silts (between 20 and 50 µm), fine silts (between 2 and 20 µm) and clays (<2 µm). Their determination is based on their sedimentation rate (according to Stockes law).
Depending on the soil type, different treatments can be considered: organic matter destruction by hydrogen peroxide, acid attack for calcareous soils (pH > 7.8), particle dispersion using Na hexametaphosphate, particle dispersion using cationic resin for Fe oxides-rich soils...
Organic matter
In addition to the mineral components, the soil is composed by organic matter (OM, including living organisms, decaying plant/animal/microbial residues, and humus). The decomposition of fresh OM produces various soil organic particles more or less stabilized (humus) and ultimately will lead to assimilable mineral elements (CO2, NO3−, NH4+). Soil OM has a great influence on the soil cation exchange capacity and can be measured by loss on ignition at 500 °C. It can also be calculated on the basis of the organic carbon (Corg) content (conversion factor OM/Corg of 1.72 for agricultural horizons or 2.0 for forest horizons).
Soil pH and electrical conductivity
Soil pH characterizes the soil as acidic (pH < 6.5), neutral (6.5 < pH < 7.5) or alkaline (pH > 7.5). It is determined from a soil/solution suspension using either a water solution (pHH2O) or a 0.1 M KCl solution (pHKCl). Using the 0.1 M KCl solution allows the release of all H+ ions, including those retained on organic matter or clay minerals. The difference between pHKCl and pHH2O gives an idea of the potential acidity of the soil. The pHKCl is also more stable over time.
The electrical conductivity of an aqueous soil extraction gives an indication of the content of soluble electrolytes.
Residual moisture
Residual moisture is the difference between air-dried soil (max: 40 °C) and 105 °C-dried soil. Results are expressed relative to the 105 °C-dried soil.
C, N, and S elemental analysis and C/N ratio
The C, N, and S contents are determined by dry combustion (according to the Dumas method). By heating to a temperature of at least 900 °C (1150 °C for S) in a stream of oxygen, C is transformed into CO2, N into NOx, and S into SO2. The measurement is performed using a thermal conductivity detector (TCD).
The C/N ratio gives an estimate of the degree of degradation of organic matter and makes it possible to adapt the manure inputs in agricultural soils (ideal C/N ratio between 10 and 25).
Nitrogen is a special case. In soil, it can take many forms (organic nitrogen, urea nitrogen, nitrate, nitrite, and ammonium). None of the methods can detect all chemical forms. In addition to the Dumas method for determining organic N, nitrate, and nitrite, the Kjedhal method allows the quantification of organic N, urea, and ammonium forms. This method is modified according to ISO-11261 by adding the Devarda mixture and allowing the conversion of nitrates into ammonium.
Cation exchange capacity (base cations, exchange acidity, and base saturation)
Cation exchange capacity (CEC) represents all the negative charges allowing cations fixation available on clays, organic materials and, to a lesser extent, silts.
There are two categories of cations: (1) alkaline and alkaline-earth cations (Ca2+, Mg2+, K+, and Na+, formerly called "base" cations) and (2) acid cations (Al3+ and H+). The sum of these two categories represents the CEC and the ratio of base cations to the CEC indicates the base saturation of the soil.
There are two types of CEC: one determined at soil pH (effective CEC determined using BaCl2 or cobaltihexammine) and one determined at pH 7 (potential CEC determined using ammonium acetate according to the Metson method).
Selective extractions (sodium pyrophosphate, ammonium oxalate, sodium dithionite…)
Metal ions in soils and sediments are distributed among the different soil constituents, such as organic matter, oxyhydroxides (Fe, Al, and Mn), silicates, carbonates, and sulphides. These metal ions are retained by different processes (ion exchange, adsorption, etc.).
Selective extractions provide detailed information on the origin, biological and physico-chemical availability, mobilization, and transport of metals. This involves: (1) the use of chemicals with specific ionic strengths and (2) the element measurement in different fractions by ICP. Most methods distinguish between five fractions:
- the "exchangeable" fraction using BaCl2 or ammonium acetate,
- the "adsorbed and/or bound to carbonates" fraction using an acetate buffer at pH 5.5,
- the oxidizable fraction linked to "organic matter" using Na pyrophosphate,
- the reducible fractions linked to "Fe- or Mn-oxyhydroxides" using hydroxylamine or Tamm's reagent (ammonium oxalate),
- the fractions linked to the oxides crystallized using dithionite (Mehra and Jackson, 1960),
- the residual fraction.
ICP elemental analysis: total fractions, major elements, trace elements (metals, metalloids, rare earth elements), and specific elements
Mineral element measurement of soil requires a prior matrix dissolution: complete dissolution using alkaline fusions or HF/HClO4 acid attacks or partial dissolution using aqua regia attacks (following the new soil decree in Wallonia for trace metals).
Once in solution, measurement is performed by ICP-AES or ICP-MS to quantify:
- major elements: Al, Ca, Fe, K, Mg, Mn, Na, P, S
- trace elements: As, B, Cd, Co, Cr, Cu, Li, Mo, Ni, Pb, Se, Ti, V, Zn…
- rare earth elements: Ce, Dy, Eu, Er, Gd, Ho La, Lu, Nd, Pr, Sc, Sm, Tb, Tm, Y, Yb
- other specific elements (Si, assimilable P, etc.)
Organic pollutant analysis: PAHs, PCBs…
The MOCA platform has a set of liquid or gas chromatography instruments (HPLC-DAD-FLD-ELSD, UPLC-MS, GC-ECD-FID, and GC-MS) allowing determination and quantification of organic pollutants, such as PCBs, PAHs, organochlorine pesticides, etc.