Manual for Soil Analysis-Monitoring and Assessing Soil Bioremediation Phần 3 pps

60 B M. Wilke • For assessment of the water retention characteristics • To determine water content at specific matric pressures (e.g., for micro- bial degradation studies) • To ascertain the relationship between the negative matric pressures and other soil physical properties (e.g., hydraulic conductivity, thermal con- ductivity) • To determine the drainable por e space (e.g., pollution risk assessment) • To determine indices for plant-available water in the soil (e.g., for irri- gation purposes) Principle. Undisturbed soil samples (soil cores) are used for the measure- men t at the high matric pressure range 0−100 kPa. The samples are satu- rated with de-aerated water or calcium sulfate solution (0.005 mol /L)and subsequently drained using sand, kaolin, or ceramic suction tables (for pressures from 0 to 20 kPa) and pressure plate extractors (f or determina- tion of pressures from −5 to −1,500 kPa). Atequilibrium status, soil samples are weighed, oven dried and reweighed to determine the water content. The results are given either as v olume fraction or mass ratio. The differences in volumefractionsatdifferentsuctionpressuresgivetheporevolume(e.g., medium pores in vol%), the differences in mass fractions give the water content retained in these pores. Two standardized (ISO 11274 1998) meth- ods are described, namely use of sand, kaolin, or ceramic suction tables fordeterminationofwatercontentsatpressuresof0to−50kPa,anduseof pressure plates f or determination o f pressures from −5 to −1,500 kPa. Theory . Soil water content and matric pressure are related to each other. At zeromatricpressurethesoilissaturatedandallporesarefilledwithwater. A s the soil dries matric pressure decreases and pores will empty according to their equivalent diameter. Large coarse pores (> 50 µm)willdrainat amatricpressureof> −6 kPa, tight coarse pores (10−50 µm)at−6to 30 kPa, medium pores at −30 to −1,500 kPa,andfineporesat< −1,500 kPa. ■ Sampling 1. It is essential that undisturbed soil samples be used for measurement at the matric pressure range 0 to −100 kPa, since soil structure has a strong influence on water-retention properties. Use either undisturbed cores or, if appropriate, individual peds for low matric pressure methods (< −100 kPa). Soil cores shall be taken in a metal or plastic cylinder of a height and diameter such that they are representative of the natural soil variability and structure. The dimensions of samples taken in the field are dependent on the texture and structure of the soil and the test 2 Determination of Chemical and Physical Soil Properties 61 Table 2.1. Recommended sample sizes (height × diameter) for the different test methods Test m et ho d Structure Coarse Medium Fine Suction table 50 × 100 mm 40 × 76 mm 24 × 50 mm Pressure plate 10 × 76 mm 10 × 50 mm method which is to be used. Table 2.1 gives guidance on suitable sample sizes for the different methods and soil structure. 2. To ensure minimal compaction and disturbance to structure, take soil corescarefully,eitherbyhandpressureinsuitablematerialorbyusing a suitable soil c orer. Takea minimumof three representative replicates for each freshly exposed soil horizon or layer; more replicates are required in stony soils. Dig out the cylinder carefully with a trowel, r oughly trim the two faces of the cylinder with a knife. If necessary adjust the sample within the cylinder before fitting lids to each end,and label the top clearly with the sample grid reference, the direction of the sampling (horizontal or vertical), the horizon number, and the sample depth. 3. Wrap the samples (e.g., in plastic bags) to prevent drying. Wrap ag- gregates (e.g., in aluminum foil or plastic film) to retain structure and prevent drying. Alternatively, excavate undisturbed soil blocks measur- ing approx. 30 cm 3 in the field, wrap in metal foil, wax (to retain structure and prevent drying), and take to the laboratory for subdivision. Store the samples at 1−2 ◦ C to reduce water loss and suppress b iological activity un til they can be analyzed. Treat samples having obvious macrofaunal activity with a suita ble biocide, e.g., 0.05% copper sulfate solution. ■ Sample Preparation 1. To prepare samples forwater-retentionmeasurementsa tpressuresgreat- er than −50 kPa, trim undisturbed cores flush with the ends of the con- tainer and replace one lid with a circle of polyamide (nylon) mesh (or similar close-weave material or paper if the water-retention character- istic is known) secured with an elastic band. The mesh will retain the soil sample in the cylinder and enable direct contact with the soil and the porous contact medium. Avoid smearing the surface of clayey soils. R emove any small projecting stones to ensure maximum contact and correct the soil volume if necessary. Replace the other lid to prevent dryingofthesamplebyevaporation.Preparesoilaggregatesforhigh matric pressure measurements by leveling one face and wrapping other 62 B M. Wilke faces in aluminum foil to minimize water loss. Disturbed soils should be packed into a cylinder with a mesh attached. Firm the soil by tapping and gentle pressure to obtain a specified bulk density. 2. Weigh the prepared samples. Ensure that the samples are brought to a pressure of less than the first equilibration point by wetting them, if necessary, by capillary rise, mesh side or leveled face down on a sheet of foam rubber satura ted with de-aerated tap water or 0.005 mol /L calcium sulfatesolution.Weighthewetsamplewhenathinfilmofwaterisseen on the surface. The time required for wetting varies with initial soil water content and texture. Soils are ideally field moist when the wetting is commenced. General guidelines fo r wetting times are: sand: 1–5 days loam: 5–10 days clay: 5–14 days or longer peat: 5–20 days. Very coarse pores are not water filled when the soil sample is saturated by capillary rise. 2.4.1 Determination of Soil W ater Characteristics Using Sand, Kaolin, and Ceramic Suction Tables Principle. Suction tables are suitable for measurement of water conten ts at matric pressure from 0 to −50 kPa. A negative matric pressure is applied to coarse silt or very fine sand held in a rigid watertight non-rusting container (a ceramic sink is particularly suitable). Soil samples placed in contact with the surface of the table lose pore water until their matric pressure is equivalent to that of the suction table. Equilibrium status is determined by weighing samples on a regular basis, and soil water content by weighing, oven drying, and reweighing. ■ Equipment • Large ceramic sink or other watertight, rigid, non-rusting container with outlet in base (dimensions about (50×70×25 cm) and close-fitting cover • Tubing and connecting pieces to construct a draining system for the suction table • Sand, silt, or kaolin, as packing material for the suction table (Com- mercially available graded and washed industrial sands with a narrow 2 Determination of Chemical and Physical Soil Properties 63 particle size distribution are most suitable. The particle size distribu- tions of some suitable sand grades and the approximate suctions they can attain are given in Table 2.2. It is permissible to use other packing materials, such as fine glass beards or aluminum oxide powder, if they can achieve the required air entry values. Alternatively to sand, silt, or kaolin suction tables, ceramic plates can be used. • Leveling bottle, stopcock, and 5-L aspirator bottle • Tensiometer system (optional) • Drying oven, capable of maintaining a temperature of 105 ±2 ◦ C • Balance capable of weighing with an accuracy of 0.1% of the measured value ■ Procedure 1. Preparesuction tables using packing material thatcanattain the required air entry values (Table 2.2). 2. Prep are soil cores as described (see above). 3. Weigh the cores and then place them on a suction table at the desired matric pressure. 4. Leave the cores for 7 days. The sample is than weighed, and thereafter weighedasfrequentlyasneededtoverifythatthedailychangeinmassof the core is less than 0.02%. The sample is than regarded as equilibrated. Table 2.2. Examples of sands and silica flour suitable for suction tables Type Coarse sand Medium Fine sand Silica flour Use Base of suction tables Surface of suction tables (5 kPa matric pressure) Surface of suction tables (11 kPa matric pressure) Surface of suction tables (21 kPa matric pressure) Typical particle size distribution Percent content > 600 µm 1110 200−600 µm 61810 100−200 µm 36 68 11 1 63−100 µm 12030 9 20−63 µm 1 3 52 43 < 20 µm 00547 64 B M. Wilke 5. Move the equilibrated sample to a suction table of a lower pressure or dryitinanovenat105± 5 C. 6. Samples which have not attained equilibrium should be replaced firmly onto the suction table and the table cover replaced to minimize evapo- ration from the table. ■ Calculation Soils Containing < 20% Stones (>2mm) 1. Calculate the water content mass ratio at a matric pressure p m using the formula: w(p m ) = m(p m )−m d m d (2.13) w(p m ) water content mass ratio at a matric pressure p m (g) m(p m ) mass of the soil sample at a matric pressure p m (g) m d mass of the oven-dried soil sample (g) 2. C alculate the water content on a v olume basis at ma tric pressure p m using the formula: θ  p m  = m  p m  − m d V ×p w (2.14) θ(p m ) water content mass ratio at a matric pressure p m (cm 3 water/cm 3 soil) m(p m ) mass of the soil sample at a matric pressure p m (g) m d mass of the oven-dried soil sample (g) V volumeofthesoilsample(cm 3 ) p w density of water (g/cm 3 ) Conversion of Results to a Fine Earth Basis The stone content of a laboratory sample ma y not accurately represent the field situation. Therefore, conversion of data to a fine earth basis may be requir ed. Conversion of results derived from suction methods to a fine earth basis (f) is required for soils containing stones (> 2 mm)according to the following equation: θ f = θ t  1− θ s  (2.15) 2 Determination of Chemical and Physical Soil Properties 65 θ f water content of the fine earth expressed as a volume fraction θ s volume of stones, expr essed as a fraction of total core volume θ t water content of the total soil, expressed as a volume fraction 2.4.2 Determination of Soil W ater Characteristics by Pressure Plate Extractor Principle. Pressure plate extractors are suitable for measurement of water contents at matric pressure −5 to −1,500 kPa. Several small soil cores are placed in contact with a porous ceramic plate contained within a pressure chamber. A gas pressure is applied to the air space above the samples and soil water moves through the plate to be collected in a burette/measuring cylinder or similar collecting device. At equilibrium status, soil samples are weighed, oven-dried, and reweighed to determine the water content at the predetermined pressures. ■ Equipment • Pressure chamber with porous ceramic plate • Sample retaining rings/soil cores with plastic discs or lids • Graduated burette • Air compressor (1.700 kPa), nitrogen cylinder, or other suitable pressur- ized gas • Pressure r egulator and test gauge • Drying oven capable of maintaining a temperature of 105 ±2.0 ◦ C • Balance capable of weighing to ±0.01 g ■ Procedure 1. Take small soil cores of approx. 5 cm diameter and 5−10 mm in height in situ or from larger undisturbed c ores. 2. Place at l east three replicates o n a pre-saturated plate o f appropriate bubbling pressure. 3. Wet the samples by immersing the plate and the samples to a level just above the base of the core and waiting until a thin film of water can be seen on the surface of the sample. 66 B M. Wilke 4. Cover the bottom of the extractor with water to create a saturated atmosphere. 5. Place a plastic disc lightly on top of each sample to prevent evaporation. 6. To apply the desired pressure, remove ex cess wat er from the porous plate and connect the outflow tube to the burette via the connector in the chamber wall. The pressure is supplied via regulators and gauges from a nitrogen cylinder or by a mechanical air compressor. 7. The pressure (from what ever source) should slightly exceed the lowest matric pressure required. 8. Apply the desired gas pressure p,checkforanygasleaks,andallowthe samplestocometoequilibriumbyrecordingonadailybasisthevolume increase in the burette. Whenthis remainsstatic, the samples have come to equilibrium; the matric pressure p m of the samples equals −p. 9. To remove the samples, clamp the outflow tube to prevent a backflow of water, and release the air pressure. 10. Weighthesamplesplussleeveimmediately. 11. Carry out sequential equilibration of the core at different pressures by removing and weighing the core at equilibrium, reinserting it, and resetting the pressure. 12. Moisten the ceramic plate with a fine spray of water to re-establish hydraulic c ontact. 13. When the last equilibrium has taken place, dry at 105 ◦ C and det ermine theoven-driedmassofthesoilplussleeve. ■ Calculation Stoneless Soils Calculate the water content volume fraction ( θ) using the formula: θ  p m  = m  p m  − m d V ×p w (2.16) θ(p m ) water content mass ratio at a m atric pressure p m (cm 3 water/cm 3 soil) m(p m ) mass of the soil sample at a matric pressure p m (g) m d mass of the oven-dried soil sample (g) 2 Determination of Chemical and Physical Soil Properties 67 V volumeofthesoilsample(cm 3 ) p w density of water (g/cm 3 ) Stony Soils Samples containing any stones (> 2 mm) shall not form part of the pressure chamber or membrane sample since the sample volume is very small. After oven-drying, determine the volume of stones in the original soil core from a field measurement and make a correction to convert θ f values to total soil ( θ t ). θ t = θ f (1 − θ s ) (2.17) θ f water content of the fine earth in the pressure vessel at equilibrium expressed as volume fraction θ s volume of stones, expr essed as a fraction of total core volume θ t water content of the total soil, expressed as a volume fraction For a soil containing a volume fraction of non porous stones of 0.05 the water content is: θ t = θ f × 0.95 (2.18) Evaluation of Results: Pore Size Distribution Pore volumes of coarse, medium, and tight pores in vol% of total soil volume can be calculated as follows: Large Coarse Pores (Equivalent Diameter >50 µm) V lcp =  θ pm0 − θ pm−6  × 100 (2.19) V lcp volume of large coarse pores (% of total soil volume) θ pm0 volumetric water content at water saturation (p m = 0 kPa) θ pm−6 volumetric water content at a matric pressure of p m = −6 kPa Tight Coarse Pores (Equivalent Diameter 10–50 µm) V tcp =  θ pm−6 − θ pm−30  × 100 (2.20) V tcp volume of large coarse pores (% of total soil vol ume) θ pm−6 volumetric water content at water saturation (p m = −6 kPa) θ pm−30 volumetric water content at a matric pressure of p m = −30 kPa 68 B M. Wilke Medium Pores (Equivalent Diameter 0.2–10µm) V mp =  θ −30 − θ pm−1500  × 100 (2.21) V mp volume of large coarse pores (percent of t otal soil volume) θ pm−30 volumetric water content at water saturation (p m = −30 kPa ) θ pm−1500 volumetric water content at a matric pressure of p m = −1,500 kPa Fine Pores (Equivalent Diameter <0.2 µm) V fp = θ pm−1500 × 100 (2.22) V fp volume of fine pores (% of total soil volume) θ pm−1500 volumetric water content at a matric pressure of p m = −1,500 kPa ■ Notes and Points to Watch • Ifacontainingsleeveisused,itshouldbeweighedandthemassdeducted from the total mass of the soil core to give m(p m ). • If stones are porous, c arry out separate water re tention m easurements and correct fine earth values according to their volume. 2.5 Soil pH ■ Introduction Objectives. Soil pH is one of the most indicative measurements of the soil chemical properties. All (bio)chemical reactions in soils are influenced by proton (H + ) activity, w hich is measured by soil pH. Values of pH of most natural soils (measured in 0.01 MCaCl 2 ) vary between < 3.00 (extremely acid) and 8.00 (weakly alkaline). Solubility of various compounds in soils is influenced by soil pH (e.g., heavy metals) as well as by microbial activ- ity and microbial degradation of pollutants. The optimum pH values for pollutant-degrading microorganisms range from 6.5 to 7.5 (Kästner 2001). Determination of soil pH is standardized in ISO DIS 10390 (2002). 2 Determination of Chemical and Physical Soil Properties 69 Principle. A pH measurement is normally made by either a colorimetric or an electrometric method. The former involves suitable dyes or acid-base indicators. Indicator strips can be used for rough estimation of soil pH. Normally, pH values of soils are measured by means of a glass electrode in a soil solution slurry that contains a fivef old volume of water containing 1 MKClor 0.01 MCaCl 2 . Theory Soil pH is a measure of the activity of ionized H (H + , H 3 O + )and defined as the negative logarithm of the H + /H 3 O + ion activity in mol/L. Soil acidity results from solu ble acids in the soil solution, e.g., organic acids and carbonic acid. Further acidic cations in the soil solution are Al 3+ and Fe 3+ . Al 3+ ion s exists in water as an [Al(H 2 O) 6 ] 3+ complex which dissociates into H 3 O + ions according to [Al(H 2 O) 6 ] 3+ + H 2 O ⇔ [Al(H 2 O) 5 ] 2+ + H 3 O + (pK a = 5.0). A stronger cationic acid producer is Fe 3+ (pK a = 2.2), which due to the low solubility of iron oxides only exists below pH 3. Soil pH is influenced by various factors, namely, the nature and type of inorganic and organic constituents (that contribute to soil acidity), the soil/solution ratio, the salt or electrolyte content, and the CO 2 partial pressure. A pH measurement in water includes easily dissociated pro- tons while 0.01 MCaCl 2 and 1 MKClsolutions also mobilize exchangeable H + . They are used to simulate soil solutions of arable soils (CaCl 2 )and forest soils (KCl) in temperate humid climates. Values of pH measured at constant salt concentrations reflect seasonal variations to a lo wer degree (Page et al. 1982); and those measured in 0.01 MCaCl 2 are 0. 6 ± 0. 2 units lower than pH H 2 O values, because H + and Al 3+ ions are partly exchanged by Ca 2+ . ■ Equipment • Shaking or mixing machine • pH meter with slope adjustment and temperature control (in case of pH values > 10, an electrode specifically designed for that range is to be used) • Glass electrode and a reference electrode or a combined electrode of equivalent performance • Thermometer capable of measuring to the nearest 1 ◦ C • Sample bottle (50 mL) m ade of borosilicate glass or p olyethylene with atightlyfittingcap • Spoon of known capacity (at least 5.0 mL) [...]... peroxide and heated again to 550 ◦ C for 1 h • The LOI is assumed to be equal in most surface soils Losses of crystalline water of clay minerals and gypsum may result in an overestimation of SOM contents The same is true for carbonate-rich soils, because decomposition of CaCO3 , which starts at temperatures of approx 500 ◦ C Therefore, the method is mainly recommended for sandy and carbonatefree soils and. .. of NO3 -N and NH4 -N in the soil extract (mg/L) b content of NO3 -N and NH4 -N in the blank extract (mg/L) w percentage of water content (m/ m) on the basis of the air-dried soil (Sect 2.1) 2 Determination of Chemical and Physical Soil Properties 87 2.9 Soil Nutrients: Phosphorus I Introduction Objectives Soil phosphorus is, besides nitrogen, potassium, calcium, and magnesium, a main nutrient for soil. .. solution It is useful for both acid and calcareous soils and has been standardized (ISO 112 63 1994) There are several methods for the quantification of P in soil extracts and soil solution, namely, spectophotometry (most common), ion chromatography, and inductively coupled plasma spectrometry (for details see Kuo 1996) The spectrophotometric method described below was developed by Murphy and Riley (1962)... 4 43 461 DIN 19684 3 (1977) Bodenuntersuchungsverfahren für den Landwirschaftlichen Wasserbau – Chemische Laboruntersuchungen – Teil 3: Bestimmung des Glühverlustes und des Glührückstandes Forster JC (1995a) Soil sampling, handling, storage and analysis – organic carbon – In: Alef K, Nannipieri P (eds) Methods in applied soil microbiology and biochemistry Academic Press, pp 59–65 Forster JC (1995b) Soil. .. JC (1995b) Soil sampling, handling, storage and analysis – soil nitrogen In: Alef K, Nannipieri P (eds) Methods in applied soil microbiology and biochemistry Academic Press, pp 79–87 Forster JC (1995c) Soil sampling, handling, storage and analysis – soil phosphorus In: Alef K, Nannipieri P (eds) Methods in applied soil microbiology and biochemistry Academic Press, pp 88– 93 Hartge KH (1968) Heterogenität... 16072 (2002) Soil quality – Laboratory methods for determination of microbial soil respiration ISO 36 96 (1987) Water for analytical laboratory use – Specifications and test methods ISO DIS 1 039 0 (2002) Soil Quality – Determination of pH ISO/TS 14256–1 (20 03) Soil Quality – Determination of nitrate, nitrite and ammonium in field moist soils by extraction with potassium chloride solution – Part 1: Manual method... alkali into NH3 , which 4 is collected in boric acid By this procedure ammonium borate is formed, which is titrated back to boric acid with hydrochloric acid according to the following equations: 2NH3 + H3 BO3 → (NH4 )2 HBO3 (NH4 )2 HBO3 + 2HCl → 2NH4 Cl + H3 BO3 80 I B.-M Wilke Equipment • Digestion flasks or tubes, of nominal volume 50 mL, suitable for the digestion stand • Digestion stand, glass tubes... determine phosphorus in soils Soil Sci Soc Am J 52: 130 1– 130 4 Bremner JM (1996) Nitrogen – total In: Bigham JM (ed) Methods of soil analysis, part 3, chemical methods Soil Sci Soc Am Am Soc Agron, SSSA Book, Series no 5, Madison, WI, pp 1085–1121 Danielson RE, Sutherland PL (1986) Porosity In: Klute A (ed) Methods in soil analysis, part 1, physical and mineralogical methods, 2nd edn Soil Sci Soc Am Am Soc... soil organisms and plants It exists in inorganic and organic fractions with varying percentages between 5 and 95% The soil organic P fraction may be derived from plant residues, soil flora, and soil fauna tissues and residues that resist rapid hydrolysis (Kuo 1996) Inorganic fractions consist of Ca-, Al-, and Fe-phosphates The most prominent phosphate mineral in soils is apatite (Ca5 (PO4 )3 OH) The total... of P from organic debris (Forster 1995c) Extracellular phosphatases are produced by microorganisms and roots and contribute to the mineralization of organic P Deficiency of P may limit the growth of plants and the microbial decomposition of pollutants in soil P is likely to be deficient in hydrocarbon-impacted soils and subsoils Therefore, its concentration has to be analyzed and, if necessary, adjusted . at 110−120 ◦ C for 2 h before use) in water and dilute to 1,000 mL at 20 ◦ C. • Buffer solution, pH 6.88 at 20 ◦ C: dissolve 3. 39 g of KH 2 PO 4 and 3. 53 g of Na 2 HPO 4 in water and dilute to. true for carbonate-rich soils, because decomposition of CaCO 3 , which starts at temperatures of approx. 500 ◦ C. Therefore,themethodismainlyrecommendedforsandyandcarbonate- free soils and peats p m (cm 3 water/cm 3 soil) m(p m ) mass of the soil sample at a matric pressure p m (g) m d mass of the oven-dried soil sample (g) V volumeofthesoilsample(cm 3 ) p w density of water (g/cm 3 ) Conversion