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HJ 1068-2019: Soil--Determination of particle size distribution--Pipette method and hydrometer method
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Soil--Determination of particle size distribution--Pipette method and hydrometer method
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Basic data | Standard ID | HJ 1068-2019 (HJ1068-2019) | | Description (Translated English) | Soil--Determination of particle size distribution--Pipette method and hydrometer method | | Sector / Industry | Environmental Protection Industry Standard | | Classification of Chinese Standard | Z18 | | Classification of International Standard | 13.080 | | Word Count Estimation | 18,189 | | Date of Issue | 2019 | | Date of Implementation | 2020-03-24 | | Issuing agency(ies) | Ministry of Ecology and Environment | HJ 1068-2019: Soil--Determination of particle size distribution--Pipette method and hydrometer method
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Soil--Determination of particle size distribution--Pipette method and hydrometer method
National Environmental Protection Standard of the People's Republic of China
Determination of soil particle size
Pipette method and hydrometer method
Soil-Determination of particle size distribution
-Pipette method and hydrometer method
2019-12-24 released
2020-03-24 implementation
Released by the Ministry of Ecology and Environment
i table of contents
Foreword ... ii
1 Scope ... 1
2 Normative references ... 1
3 Terms and definitions ... 1
4 Methodology ... 1
5 Interference and cancellation ... 1
6 Reagents and materials ... 2
7 Instruments and equipment ... 3
8 Sample ... 5
9 Analysis steps ... 6
10 Calculation and Representation of Results ... 8
11 Precision ... 12
12 Quality Assurance and Quality Control ... 13
13 Notes ... 14
Foreword
In order to implement the "Environmental Protection Law of the People's Republic of China"
Environment, protect human health, standardize the measurement method of soil particle size, and formulate this standard.
This standard specifies the pipette method and hydrometer method for determining soil particle size.
This standard is issued for the first time.
This standard is formulated by the Department of Eco-Environmental Monitoring, Laws and Standards Department of the Ministry of Ecology and Environment.
This standard was drafted. Hebei Ecological Environment Monitoring Center, College of Resources and Environmental Sciences, Hebei Agricultural University.
This standard is verified by. Department of Soil and Water Science, China Agricultural University, Laboratory of the Second Geological Brigade of Hebei Provincial Bureau of Geology and Mining
Hebei Huaqing Environmental Technology Co., Ltd., Laboratory of the Fourth Geological Brigade of Hebei Provincial Bureau of Geology and Mineral Resources, Hebei Province
Geological Brigade Laboratory, Hebei Geological Experimental Testing Center and Hebei Regional Geological and Mineral Investigation Research Institute Laboratory.
This standard was approved by the Ministry of Ecology and Environment on December 24,.2019.
This standard will be implemented from March 24, 2020.
This standard is explained by the Ministry of Ecology and Environment.
1 Determination of soil particle size Pipette method and hydrometer method
1 Scope
This standard specifies the pipette method and hydrometer method for determining soil particle size.
This standard applies to the determination of soil particle size.
2 Normative references
This standard refers to the following documents or clauses therein. For undated references, the valid version applies to this
standard.
GB/T 6003.1 Test sieve technical requirements and tests-Part 1. Wire woven mesh test sieve
Basic dimensions of GB/T 6005 test sieve, wire mesh, perforated plate and electroformed sheet
HJ 613 Soil dry matter and moisture determination by gravimetric method
HJ/T 166 Technical Specifications for Soil Environmental Monitoring
3 terms and definitions
The following terms and definitions apply to this standard.
3.1
Soil particle size distribution
Also known as soil particle composition or mechanical composition, it refers to the combination ratio of mineral particles of different particle sizes in the soil.
The percentage of the mass of the kernel is expressed.
3.2
Stokes's Law
Under the action of gravity, the falling speed of particles of different diameters is proportional to the square (r2) of the radius of the sphere (soil)
It is inversely proportional to the viscosity coefficient of the dispersion medium.
4 Method principle
A sample of air-dried soil passing through a 2 mm sieve was made into a suspension. Particles larger than 0.063 mm
Sub-sieve; particles smaller than 0.063 mm are determined by the pipette method or hydrometer method according to Stokes' law. according to
Calculate the percentage content of each level of particle mass, and plot the cumulative distribution of soil particle size on semi-logarithmic paper (see Figure 3).
And determine the soil particle size.
5 Interference and cancellation
5.1 Organic matter and salts (especially insoluble salts such as gypsum) will flocculate and affect the determination of samples.
2 powder to eliminate the effect.
5.2 Iron oxide and carbonate (especially calcium carbonate and magnesium carbonate) will interfere with the dispersion of soil particles and affect the determination.
Sodium sulfite and sodium acetate remove the interference of iron oxide, and the excess of hydrochloric acid solution is used to remove the interference of carbonate.
6 Reagents and materials
Unless otherwise specified, analytical reagents that comply with national standards are used in the analysis. The experimental water is freshly prepared distilled water.
Or deionized water.
6.1 Hydrogen peroxide. w (H2O2) = 30%.
6.2 Hydrochloric acid. ρ (HCl) = 1.18 g/ml.
6.3 Glacial acetic acid (CH3COOH).
6.4 Defoamer. 2-octanol [CH3 (CH2) 5CH (OH) CH3], ethanol (CH3CH2OH).
6.5 Sodium hexametaphosphate [(NaPO3) 6].
6.6 Anhydrous sodium carbonate (Na2CO3).
6.7 Sodium oxalate (Na2C2O4).
6.8 Sodium hydroxide (NaOH).
6.9 Calcium chloride (CaCl2).
6.10 Sodium dithionite (Na2S2O4).
6.11 Sodium acetate (CH3COONa).
6.12 Hydrochloric acid solution. c (HCl) = 1 mol/L.
Take 85 ml of hydrochloric acid (6.2) and dilute to 1000 ml with water.
6.13 Hydrochloric acid solution. 1 3.
6.14 Sodium oxalate solution. c (1/2Na2C2O4) = 0.5 mol/L.
Weigh 33.5 g of sodium oxalate (6.7), add 700 ml of water, heat to dissolve, and dilute to 1000 ml with water after cooling.
6.15 Sodium hydroxide solution. c (NaOH) = 0.5 mol/L.
Weigh 20 g of sodium hydroxide (6.8) and dissolve in an appropriate amount of water, and dilute to 1000 ml with water.
6.16 Dispersant solution.
Weigh 33 g of sodium hexametaphosphate (6.5) and 7 g of anhydrous sodium carbonate (6.6), dissolve in an appropriate amount of water, and dilute to 1000 ml with water.
Store in brown bottle, valid for 1 month.
The dispersant solution has a pH of about 9.8 and is suitable for most soils. For soils that still condense after adding the solution,
Add different dispersants according to its pH. neutral soil plus 25.00 ml sodium oxalate solution (6.14), acidic soil plus 25.00 ml
Sodium hydroxide solution (6.15).
6.17 Calcium chloride solution. c (CaCl2) = 1 mol/L.
Weigh 111 g of calcium chloride (6.9) in an appropriate amount of water and dilute to 1000 ml with water.
6.18 Sodium dithionite solution. ρ (Na2S2O4) = 40 g/L.
Weigh 40 g of sodium dithionite (6.10) and dissolve it in an appropriate amount of water, and dilute it to 1000 ml with water.
6.19 Sodium acetate solution. c (CH3COONa) = 0.3 mol/L.
Weigh 24.62 g of sodium acetate (6.11) in an appropriate amount of water and dilute to 1000 ml with water.
37 instruments and equipment
7.1 Suction tube (see Figure 1). The volume is 25 ml, which needs to be used in conjunction with a ball valve or an equivalent device (7.15).
Figure 1 Pipette
The volume of newly purchased pipettes should be accurately measured before use.
Measurement method. Wash and dry the pipette thoroughly, soak it up with water. Place the water in the pipette to a scale of known mass
In a measuring bottle (7.12), weigh (accurate to 0.0001 g). Calculate the pipette volume (Vc) based on the mass of the water (mc). on
The operation was repeated three times, and the average was taken to the nearest 0.05 ml.
The volume of the pipette is calculated according to formula (1).
4 (1)
In the formula. Vc--suction tube volume, ml;
mc--quality of water taken by pipette, g;
ρ--density of water at test temperature, g/ml, see Table 2.
7.2 Constant temperature room or constant temperature water bath. 20 ℃ ～ 30 ℃, ± 0.5 ℃.
7.3 Oscillation equipment. a flip-type oscillation device with a rotation speed of (30 ± 2) r/min
7.4 Air drying oven. 105 ℃ ～ 110 ℃.
7.5 Electric heating plate.
7.6 Centrifuge. The rotation speed is not less than 1000 r/min.
7.7 Analytical balance. Sensitivity is 0.0001 g.
7.8 Conductivity meter.
7.9 Metal washing sieve. A square-hole sieve with an aperture of 0.063 mm shall meet the requirements of GB/T 6005 and GB/T 6003.1.
7.10 Metal soil sieve. square-hole sieves with 2 mm, 0.60 mm, and 0.212 mm pore diameters shall comply with GB/T 6005
And GB/T 6003.1 requirements.
7.11 Glass measuring cylinder. 1000 ml capacity, with rubber stopper or stirrer (7.14).
7.12 Weighing bottle. glass or metal, 50 ml.
7.13 Centrifuge tube. organic material, leak-proof cap, 500 ml; 1000 ml conical flask can also be used.
7.14 Stirrer. metal or anti-corrosion plastic material, glass rod with rubber stopper can also be used, see Figure 2.
Figure 2 Blender
57.15 Ball valves or equivalent.
7.16 Hydrometer. The scale range is 0 g/L ～ 60 g/L, and the accuracy is 0.5 g/L.
Before using the hydrometer, the effective depth z should be calibrated according to the attached certificate.
7.17 Instruments and equipment commonly used in general laboratories.
8 samples
8.1 Sample collection and storage
The collection and storage of soil samples were performed in accordance with HJ/T 166.
8.2 Sample preparation
According to the relevant regulations of HJ/T 166, place the soil sample in an enamel pan and spread it into a thin layer of 2 cm to 3 cm.
Crush and turn from time to time to pick up foreign objects such as gravel, gravel, and plant debris. For sticky soils, when the sample is half dry,
Large pieces of soil are crushed or chopped with a wooden shovel to prevent them from forming into lumps when they are completely dry and difficult to crush and sieve.
Pour the air-dried sample on a plexiglass plate, crush it again with a wooden hammer, wooden roller, etc., pick up the foreign matter, and pass through 2 mm of soil
Sieve (7.10). The sample should be thoroughly mixed after sieving.
Note. For gravels larger than 2 mm, do not crush them. The topsoil attached to the gravels should be rubbed and separated through a sieve.
8.3 Preparation of test specimens
8.3.1 Weighing
Weigh an appropriate amount (ms, accurate to 0.01 g) of the soil sample (8.2) into a centrifuge tube or Erlenmeyer flask (7.13). Sampling volume based
The soil type is determined. The sandy soil is about 60 g and the clay is about 20 g.
Soil samples with low organic matter, soluble salt and gypsum, iron oxide and carbonate content can be directly analyzed after weighing.
(9.1); when the content is too high to interfere with the measurement, pretreatment according to 8.3.2.
8.3.2 Remove interference
8.3.2.1 Removal of organic matter
There are two ways to remove organic matter from the sample.
Method 1. When using a centrifuge tube, add about 30 ml of water to the tube to completely infiltrate the sample, and then add 30 ml of peroxygen
Hydrogen (6.1), stir well, when there is more foam, add an appropriate amount of defoamer (6.4) to defoam. Continue adding water to a volume of 150 ml ～
200 ml, left to stand overnight, centrifuge for 15 min (speed is not less than 1000 r/min), discard the supernatant. Repeat the above steps until
The supernatant was colorless or nearly colorless.
Note. When the supernatant is not well centrifuged, add 25 ml of calcium chloride solution (6.17), stir well, add water to 250 ml, and centrifuge after standing
15 min (speed is not less than 1000 r/min), discard the supernatant. Add 250ml of water and repeat the washing step until the color of the sample
shallow.
Method 2. When using an Erlenmeyer flask, add approximately 30 ml of water to the bottle to completely infiltrate the sample, and then add 30 ml of peroxygen
Hydrogen (6.1), stir well, when there is more foam, add an appropriate amount of defoamer (6.4) to defoam. Allow the reaction to stabilize overnight.
Carefully heat on a hot plate (7.5), defoam with a defoamer (6.4), and keep stirring. Keep samples moist, if necessary
6 Add appropriate amount of water to keep the suspension slightly boiling until the foaming phenomenon disappears. If there is still undecomposed organic matter, stop
After heating and cooling, continue to add hydrogen peroxide (6.1) and repeat the process until the color of the sample becomes light. Will be processed
The sample was transferred to a centrifuge tube, the volume of the solution was controlled between 150 ml and.200 ml, and centrifuged for 15 minutes (the conditions were the same as the method 1), discarded
Go to the supernatant.
8.3.2.2 Removal of soluble salts and gypsum
Add 250 ml of water to the above centrifuge tube or Erlenmeyer flask (8.3.2.1), close the lid, and shake on the shaker (7.3)
After shaking for 1 h, centrifuge for 15 min (the speed is not less than 1000 r/min), and discard the supernatant. Repeat the process until the supernatant
The conductivity is less than 40.0 mS/m.
8.3.2.3 Removal of iron oxides and carbonates
In the sample treated above (8.3.2.2), add sodium dithionite solution (6.18) at a solid-liquid ratio of 1.40.
And sodium acetate solution (6.19), add glacial acetic acid (6.3) to adjust the pH to 3.8, shake overnight, and centrifuge for 15 min (the speed is not small)
(At 1000 r/min), discard the supernatant.
Continue to add an appropriate amount of hydrochloric acid solution (6.12), then add water to 250 ml, and heat in a water bath at 80 ° C for 15 min.
Stir. After standing overnight, centrifuge for 15 min (the speed is not less than 1000 r/min), and discard the supernatant. Repeat the above process until
The conductivity of the supernatant was less than 40.0 mS/m.
Note. The amount of hydrochloric acid solution (6.12) is related to the carbonate content in the sample, which can be determined by the following methods. take an appropriate amount of soil sample (8.2)
Place it on a white porcelain plate and add hydrochloric acid solution (6.13) dropwise. If there is no air bubble in the soil sample or the air bubble is slowly released, and the sound is very small,
Add 25 ml of hydrochloric acid solution (6.12); if bubbles appear obviously, but disappear quickly, and the sound is loud, add 40 ml of hydrochloric acid
Solution (6.12); if bubbles occur strongly, boil, last for a long time, and have a loud noise, add 60 ml of hydrochloric acid solution (6.12).
9 Analysis steps
9.1 scattered soil samples
Transfer the pretreated sample to an Erlenmeyer flask (7.12), add an appropriate amount of water to control the solution volume to 150 ml ～
200 ml, then add 25.00 ml of dispersant solution (6.16). Put a small funnel on the bottle mouth and heat it on a hot plate (7.5)
For 1 h, maintain a slight boiling state. Shake the conical flask frequently during the boiling process to prevent soil particles from depositing on the bottom of the bottle and forming a hard mass.
Note 1. It is not necessary to remove the disturbed soil sample. After adding the dispersant, shake it and let it stand for 2 h, then place it on a hot plate (7.5) to heat it.
Note 2. The solution containing the dispersant can also be placed in a centrifuge tube and shaken on a shaker (7.3) for 18 h.
9.2 Wet screening
Place the washing sieve (7.8) in a large glass funnel and place the funnel neck in the graduated cylinder. The dispersed sample (9.1) is completely
Transfer to the washing screen, rinse the sample with a washing bottle until the filtrate is no longer turbid, and the total volume of the washing water cannot exceed 1000 ml.
Add water to the vector cylinder to 1000 ml to make a suspension.
Note 1. When the soil is difficult to pass through the sieve, a few drops of dispersant solution on the sieve plate can be used to wet the sieve beforehand, which will help the sieve.
Note 2. A glass rod or a plastic rod with a rubber sleeve can be used to agitate the suspension on the sieve to reduce the blockage of the sieve.
Rinse the sample on the sieve into an evaporation dish, evaporate to dryness on a hot plate, then transfer it to an oven at 105 ° C to 110 ° C
Bake for 6 h, place in a desiccator and cool to room temperature, then pass through 0.60 mm and 0.212 mm soil sieves (7.9), and weigh them separately
7 weights (accurate to 0.0001 g).
9.3 Settlement
Place the graduated cylinder containing the soil suspension (9.2) in a constant temperature environment (7.2) for at least 1 h; when using a water bath, ensure that the water
Immerse to the 1000 ml mark. Shake the graduated cylinder at a frequency of not less than 30 times/min for 2 minutes; also use a stirrer to vertical
Stir the suspension for 1 min, 30 times each, to ensure that no soil particles remain on the tube wall.
When the graduated cylinder is upright or immediately after stirring is stopped, start timing. If there is foam, add 1-2 drops of defoamer (6.4)
Defoaming.
After the sedimentation is completed, the pipette method or hydrometer method is selected for the next measurement as required.
9.4 Determination
9.4.1 Pipette method
9.4.1.1 Dispersant mass calibration
Pipette 25.00 ml of dispersant solution (6.16) into a glass measuring cylinder (7.9), add water to 1000 ml, and mix well
Place in a constant temperature environment (7.2) for at least 1 h. Aspirate the solution from the graduated cylinder with a pipette (7.1) and place it on a scale of known mass.
In a measuring bottle (7.11), evaporate to dryness on a hot plate, transfer to an oven, bake at 105 ° C to 110 ° C for 6 hours, and place in a desiccator.
After cooling to room temperature, weigh (mr, accurate to 0.0001 g).
9.4.1.2 Aspiration
The prepared soil suspension (9.2) was allowed to stand for the time specified in Table 1 and then aspirated with a pipette (7.1).
Table 1 Suspension time of suspension
Particle size
time
Temperature (℃)
0.063 mm 0.020 mm 0.006 mm 0.002 mm
min s min s min sh min s
20 0 28 4 39 51 35 7 44 17
21 0 27 4 32 50 21 7 33 9
22 0 27 4 25 49 10 7 22 30
23 0 26 4 19 48 2 7 12 18
24 0 26 4 13 46 54 7 2 7
25 0 25 4 8 45 52 6 52 51
26 0 24 4 2 44 51 6 43 35
27 0 24 3 57 43 52 6 34 46
28 0 23 3 52 42 53 6 25 58
29 0 23 3 47 41 58 6 17 38
30 0 22 3 42 41 5 6 9 45
8 About 15 s before aspiration, close the valve and insert the aspiration tube vertically from the center of the suspension to below the liquid surface (100 ± 1) mm
Office. Try to avoid disturbing the suspension during operation, and the above operation should be completed within 10 s.
After opening the valve to fill the pipette with the sample, remove it completely from the suspension. Sampling operation should be completed within 10 s
to make.
Drain the suspension in the safety ball neck of the pipette through the outlet tube into the waste bottle and rinse with water until there is no suspension in the safety ball neck
Liquid residue.
9.4.1.3 Weighing
Place a weighing bottle (7.11) of known mass under the pipette, open the valve, and transfer the suspension to the weighing
In the bottle. Rinse the inner wall of the pipette with water until no suspension remains. Put the rinse water in a weighing bottle and evaporate it on a hot plate.
Transfer to an oven and bake at 105 ° C to 110 ° C for 6 h. After cooling to room temperature in a desiccator, weigh (ms1, accurate to
0.0001 g).
Clean the residues attached to the outside of the pipette. According to the time given in Table 1, follow the same steps to suck different particles.
Diameter sample, weighed (msx, accurate to 0.0001 g).
9.4.2 Hydrometer
9.4.2.1 Preparation of Dispersant Calibration Solution
Pipette 25.00 ml of dispersant solution (6.16) into a glass measuring cylinder (7.10), add water to 1000 ml, and mix well.
Prepare a dispersant calibration solution and place in a constant temperature environment (7.2).
9.4.2.2 Measurement
Immerse the hydrometer (7.16) slowly and vertically into the prepared soil suspension (9.2) (slightly lower than the floating position, and
Allow it to float freely), take a hydrometer reading from the edge of the meniscus at 0.5 min, 1 min, 2 min, and 4 min,
Recorded as m '(g).
After reading, gently remove the hydrometer, rinse with water, dry, and place it in a graduated cylinder (9.4.2.1) containing a dispersant calibration solution.
Read in the same way and record it as mo '(g). Re-insert the hydrometer into the soil suspension. After settling for 8 min, 30 min,
The readings were taken at 8 h and 24 h and recorded as m '(g).
9.4.2.3 Determination of dry matter content of samples
The dry matter content of the samples was determined in accordance with HJ 613.
10 Calculation and representation of results
10.1 Calculation of pipette results
The mass of particles in 1000 ml suspension was calculated according to formulas (2) to (4).
(2)
9 (3)
(4)
In the formula. m0.020 ～ 0.063—mass of particles with a particle size between 0.020 mm and 0.063 mm, g;
m 0.002 ～ 0.020--mass of particles with a particle size between 0.002 mm and 0.020 mm, g;
m < 0.002--mass of particles with particle size < 0.002 mm (minus the mass of dispersant), g;
msx--the mass of the solid substance in the pipette during the xth (x represents the first and 2x times) pipetting, g;
mr--corrected mass of dispersant, g;
VC--pipette volume, ml.
The mass percentage of particles at each level is calculated according to formulas (5) to (11).
(5)
(6)
(7)
(8)
(9)
(10)
(11)
In the formula. w0.60 ～ 2.00--mass percentage of particles with a particle size between 0.60 mm and 2.00 mm,%;
w0.212 ～ 0.60--mass percentage of particles with particle size between 0.212 mm and 0.60 mm,%;
w0.063 ～ 0.212--mass percentage of particles with a particle size between 0.063 mm and 0.212 mm,%;
w0.020 ～ 0.063--mass percentage of particles with a particle size between 0.020 mm and 0.063 mm,%;
w0.002 ～ 0.020--mass percentage of particles with particle size between 0.002 mm and 0.020 mm,%;
w < 0.002--mass percentage of particles with particle size < 0.002 mm,%;
m0.60 ～ 2.00—mass of particles with a particle size between 0.60 mm and 2.00 mm, g;
m 0.212 ～ 0.60--mass of particles with particle size between 0.212 mm and 0.60 mm, g;
m0.063 ～ 0.212--mass of particles with a particle size between 0.063 mm and 0.212 mm, g;
mt--the total mass of soil particles at all levels (the sum of the mass of soil particles passing through the 0.063 mm sieve and the sedimentation at all levels), g.
Note. In this calculation method, the total mass mt of soil particles at all levels is the level after removing organic matter, soluble salts and gypsum, iron oxide and carbonate
Sum of particle mass instead of soil mass ms as measured in 8.3.1.
The cumulative mass percentage of particles at all levels is calculated with reference to formulas (12) to (16).
(12)
(13)
(14)
(15)
(16)
In the formula. w < 2.00--cumulative mass percentage of particles with particle size < 2.00 mm,%;
w < 0.60--cumulative mass percentage of particles with particle size < 0.60 mm,%;
w < 0.212--cumulative mass percentage of particles with particle size < 0.212 mm,%;
w < 0.063--cumulative mass percentage of particles with a particle size of < 0.063 mm,%;
w < 0.020--Cumulative mass percentage of particles with a particle size of < 0.020 mm,%.
10.2 Calculation of hydrometer results
The true reading of the hydrometer is calculated according to formula (17).
(17)
In the formula. m--the true reading of the hydrometer, g;
m '-observed hydrometer reading, g;
mo '-The hydrometer reading in the graduated cylinder containing the dispersant calibration solution, g.
The particle size is calculated according to formula (18).
(18)
Where. dp--particle size, mm;
η--the viscosity coefficient of water at the test temperature, g/m · s, see Table 2;
z--effective depth, mm;
ρs--particle density, uniformly specified as 2.65 g/cm3;
ρw--suspension density, 1.00 g/cm3;
g--gravitational acceleration, 981 cm/s2;
t--settling time, s;
Table 2 Water density and viscosity coefficient
Temperature (℃) Density ρ (g/ml) Viscosity coefficient η (g/m · s)
20 0.9982 1.002
21 0.9980 0.978
22 0.9978 0.955
23 0.9975 0.933
24 0.9973 0.911
25 0.9970 0.891
26 0.9968 0.871
27 0.9965 0.852
28 0.9962 0.833
29 0.9959 0.815
30 0.9957 0.798
The cumulative mass percentage of particles at all levels is calculated according to formula (19).
(19)
In the formula. w--the cumulative mass percentage of particles at all levels,%;
m--true reading of hydrometer, g;
ms--quality of soil sampling, g;
wdm--dry matter content of soil,%.
10.3 Representation of results
The measurement result is retained to one digit after the decimal point, and a maximum of 3 significant digits are retained. The final result is to accumulate quality
The percentage of the amount is the ordinate, the corresponding particle size is the abscissa, and the soil particle size is plotted on a semi-logarithmic coordinate paper.
...
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