NY/T 1121.3-2006 Soil testing Part 3: Determination of soil mechanical composition
Some standard content:
ICS13.080.05
Agricultural Industry Standard of the People's Republic of China
NY/T1121.3—2006
Soil Testing
Part 3: Method for determination of soil mechanical composition2006-07-10 Issued
2006-10-01 Implementation
Ministry of Agriculture of the People's Republic of China
NY/T1121 "Soil Testing" is a series of standards, including the following parts: Part 1: Collection, processing and storage of soil samples Part 2: Determination of soil pH
Part 3: Determination of soil mechanical composition
Part 4: Determination of soil bulk density
Part 5: Determination of cation exchange capacity of calcareous soils Part 6: Determination of soil organic matter
Part 7: Determination of available phosphorus in acidic soils Part 8: Determination of Available Boron in Soil
Part 9: Determination of Available Molybdenum in Soil
Part 10: Determination of Total Mercury in Soil
Part 11: Determination of Total Arsenic in Soil
Part 12: Determination of Total Arsenic in Soil
Part 13: Determination of Exchangeable Calcium and Magnesium in Soil
Part 14: Determination of Available Sulfur in Soil
Part 15: Determination of Available Silicon in Soil
Part 16: Determination of Total Water-soluble Salt in Soil
Part 17: Determination of Chloride Ion Content in Soil
Part 18: Determination of Sulfate Ion Content in Soil.
This part is Part 3 of NY/T1121.
The appendices in this part are normative appendices. This part is proposed and managed by the Ministry of Agriculture of the People's Republic of China. NY/T1121.3—2006
The drafting units of this part are: National Agricultural Technology Extension Service Center, Institute of Agricultural Resources and Agricultural Zoning of Chinese Academy of Agricultural Sciences, Beijing Soil and Fertilizer Workstation, Anhui Soil and Fertilizer Station. The main drafters of this part are: Tian Youguo, Xin Jingshu, Ren Yi, Xu Aiguo, Zhu Li, Zhang Yifan. I
1 Scope of application
Soil testing
Part 3: Determination of mechanical composition of soil
This part is applicable to the determination of mechanical composition of various types of soil. 2 Principle of determination
NY/T1121.3—2006
The sample is processed into a suspension. According to Stokes' law, the change of suspension density is measured at different times using a special type A soil hydrometer, and the soil particle size and its content percentage are calculated based on the sedimentation time, sedimentation depth and hydrometer readings. 3 Main instruments and equipment
3.1 Soil hydrometer
Scale range: 0g/L60g/L
3.2 Sedimentation cylinder (1L)
3.3 Washing sieve
Diameter: 6cm, pore size: 0.2mm
3.4 Stirring rod with rubber pad (with holes)
3.5 Constant temperature drying oven
3.6 Electric heating plate
3.7 Stopwatch
4 Reagents
0.5mol/L sodium hexametaphosphate solution
Weigh 51.00g sodium hexametaphosphate (chemically pure), Add 400mL of water, heat to dissolve, cool and dilute to 1L with water, its concentration c[1/6(NaPO))=0.5mol/L
4.20.5mol/LSodium oxalate solution
Weigh 33.50g sodium oxalate (chemically pure), add 700mL of water, heat to dissolve, cool and dilute to 1L with water, its concentration c(1/2Na2C2Oa)=0.5mol/L
4.30.5mol/LSodium hydroxide solution
Weigh 20.00g sodium hydroxide (chemically pure), add water to dissolve and dilute to 1L. 5 Analysis steps
1) See Appendix A for the determination of natural soil moisture content. 2) Weighing: Weigh 50.00g of the sample with a 2mm aperture sieve into a 500mL conical flask, add water to moisten the suspension. Preparation of suspension: add different dispersants according to soil pH (calcareous soil, add 60mL0.5mol/L sodium metaphosphate solution; neutral soil, add 20mL0.5mol/L sodium oxalate solution; acidic soil, add 40mL0.5mol/L sodium hydroxide solution), and then add water to the conical flask to make the soil liquid volume about 250mL. Put a small funnel at the mouth of the flask, sow evenly, let it stand for 2h, then put it on the electric heating plate to heat, and microfilter for 1h. During the boiling process, shake the conical flask frequently to prevent the particles from settling at the bottom of the bottle and forming lumps. NY/T1121.3—2006
Put a washing sieve with a pore size of 0.2mm in a funnel, and then put the funnel on a sedimentation tube. After the suspension cools down, pass the washing sieve through the sedimentation tube until the water flowing out of the sieve is clear, but the amount of washing water cannot exceed 1L, and then add water to the 1L mark. The sand particles left on the washing sieve are washed with water into a lead box of known mass, evaporated on a hot plate and moved into an oven, dried at 105±2C for 6h, weighed after cooling (accurate to 0.01g), and the percentage of sand content is calculated. 4) Measure the temperature of the suspension: insert a thermometer into the sedimentation tube with water, and place it together with the sedimentation tube containing the suspension to be tested, and record the water temperature, which represents the temperature of the suspension.
5) Determine the density of the suspension: Place the sedimentation tube containing the suspension on a platform with small temperature changes, and stir it up and down with a stirring sample for 1 minute (30 times up and down each time, and do not lift the porous piece of the stirring rod out of the liquid surface). When stirring, if bubbles are generated in the suspension and affect the observation of the hydrometer scale, add a few drops of 95% ethanol to remove the bubbles. Start timing immediately after stirring. Gently put the hydrometer vertically into the suspension 10s~15s before reading, and slightly change the glass rod of the hydrometer by hand to prevent it from shaking up and down or left and right. Measure the hydrometer readings at 30s, 1min, and 2min after the start of sedimentation (each time, the upper edge of the meniscus is used as the standard) and record them. Take out the hydrometer, put it in clean water, wash it and set it aside.
According to the specified sedimentation time, continue to measure the hydrometer readings at 4min8min, 15min.30min, 1h2h, 4h.8h.24h, etc. Place the hydrometer in the suspension 15 seconds before each reading. Take out the hydrometer immediately after the reading and wash it in clean water for later use. 6 Result calculation
1) See Appendix A for the calculation of natural soil moisture content. 2) Calculation of the mass of dried soil:
Mass of air-dried sample, g
Mass of dried soil, B natural density of sample + 1000×1000..
3) Calculation of the content of coarse sand particles (2.0mmD>0.2mm): Content of coarse sand particles between 2.0mm and 0.2mm, % Mass of particles dried on a 0.2mm hole × 100.. (2) Mass of dried sample
4) Calculation of the cumulative content of particles below 0.2mm in diameter and smaller than a certain diameter: - hydrometer reading + hydrometer scale meniscus correction value + temperature correction value - dispersed amount smaller than a certain diameter
Mass of dried sample
Content of particles with a diameter less than a certain diameter, %
5) Calculation of soil particle diameter. The effective diameter (D) of particles below 0.2mm, which is smaller than a certain particle size, can be calculated according to the Stokes formula: 1800m
981(d,-d2)
Wherein:
soil particle diameter, in millimeters (mm); soil particle density, in grams per cubic centimeter (space/cm); water density, in grams per cubic centimeter (g/cm); d2
soil particle effective settling depth, in centimeters (cm) (can be found in Figure 1); soil particle settling time, in seconds (s);
water viscosity coefficient, in grams per centimeter per second (g/em*s) see Table 1: gravity acceleration, in centimeters per square second (cm/). Table 1 Viscosity coefficient of water (n)
Temperature, °C
.g/cm*s
Temperature,
g/cm*s
Temperature, C
Surface (1) Swimming*
.g/cms
0.009.810
Table 1 (continued)
Hydrometer reading
Temperature, C
The L value in the relationship diagram of hydrometer reading and effective settlement depth in Figure 1 can be found from the relationship diagram of hydrometer reading and effective settlement depth of soil particles (Figure 1). 6
NY/T1121.3—2006
7-g/ams
0.007.840
Drawing of particle size distribution curve: Based on the particle size values calculated by screening and hydrometer readings and the corresponding cumulative percentage of soil particles, the particle size distribution curve is drawn on semi-logarithmic paper with the cumulative percentage of soil particles as the ordinate and the particle size value as the abscissa (Figure 2).
Calculate the percentage of each particle size to determine the soil texture. From the particle size distribution curve, find the cumulative percentage of each particle size <2.0mm, <0.2mm, <0.02mm and <0.002mm. Subtract the upper and lower levels to get the percentage content of each particle size of 2.0mm≥D>0.02mm, 0.02mm≥D>0.002mm, and D<0.002mm. Example: If the cumulative percentages of particle sizes <2.0, <0.2, <0.02, and <0.002 mm are 100.93, 42, and 20, respectively, then
NY/T1121.3—2006
Number of soil weight less than the diameter of the vegetable
90808330
Soil particle size (mm)
Figure 2 Particle size distribution curve
Clay (D<0.002 mm) content, %=20
Powder ( Sand) particle (0.02mmD>0.002mm) content, %=42-20=22 Fine sand (0.2mmD>0.02mm) content, %=93-42=51 Coarse sand (2.0mm~0.2mm) content, %=100-93=798858888
0.2mmzD>0.02mm and 2.0mmzD>0.2mm, that is, the sum of the fine sand and machine sand content is the sand grade (2.0mmD>0.02mm) content. In this case, the sand grade content is 58%. 7 Precision
Parallel determination results allow absolute difference of clay grade ≤3%; silt (sand) grade ≤4%. 8 Notes
a) Correction of effective settlement depth (L) of soil particles. The hydrometer reading not only indicates the density of the suspension, but also indicates the sedimentation depth of the soil particles, that is, the distance (I) from the suspension surface to the center of the hydrometer bubble volume is used to indicate the sedimentation depth of the soil particles. However, in the experimental measurement, when the hydrometer is immersed in the suspension, the liquid level rises, and the distance (L) from the reading (i.e. the tangent point between the suspension surface and the hydrometer) to the center of the bubble volume is not the actual depth of the soil particle sedimentation (i.e. the effective sedimentation depth of the soil particles L). Moreover, the I value represented by the same reading of different hydrometers is different due to the form and reading of the hydrometer. Therefore, before using the hydrometer, it is necessary to first calibrate the effective sedimentation depth of the soil particles (Figure 3) to find the relationship between the hydrometer reading and the effective sedimentation depth of the soil particles. The calibration steps are as follows.
1) Determine the volume of the hydrometer bubble: Take a 500mL measuring cylinder, pour about 300mL of water, place it in a constant temperature room or a constant temperature water tank, keep the water temperature at 20C, and measure and record the volume scale at the water surface of the measuring cylinder (based on the lower edge of the meniscus). Place the hydrometer in the measuring cylinder so that the water level just reaches the lowest scale of the hydrometer (based on the lower edge of the meniscus), and then measure and record the volume scale of the measuring cylinder at the water surface (based on the lower edge of the meniscus). The difference in volume between the two is the volume of the hydrometer bubble (V). Take the arithmetic mean of the two measurements twice as the V value (mL).
2) Determine the center of the volume of the hydrometer bubble: Under the above-mentioned constant temperature of 20℃, adjust the water level in the measuring cylinder to a certain scale, place the hydrometer in the water, and when the volume of the liquid surface rises to 1/2 of the volume of the hydrometer bubble, the point where the water surface is tangent to the bubble (based on the lower edge of the meniscus) is the center line of the bubble volume (Figure 3). Fix the hydrometer on the tripod and use a ruler to accurately measure the vertical distance from the water surface to the lowest scale of the hydrometer (12L2), that is, the vertical distance from the center line of the bubble volume to the lowest scale. 3) Measure the inner diameter of the measuring cylinder (R) to 1mm) and calculate the cross-sectional area of the measuring cylinder (S): S=1/4 yuan R yuan~3.14. Figure 3 Soil particle sedimentation depth L correction diagram
4) Use a ruler to accurately measure the distance (L) from the lowest scale of the hydrometer to each scale on the glass rod, measure once every 5 grids and record. 5) Calculate the effective sedimentation depth of soil particles (L
LL'--L+
Where:
L is the effective sedimentation depth of soil particles, in centimeters (cm); L is the distance from the liquid surface to the center of the hydrometer bubble volume, in centimeters (cm); L is the distance from the lowest scale to each scale on the glass rod, in centimeters (cm): 12L2 is the distance from the center of the hydrometer bubble volume to the lowest scale, in centimeters (cm); V is the volume of the hydrometer bubble, in cubic centimeters (cm); S is the cross-sectional area of the measuring tube, in square centimeters (cm?) (5)
6) Draw a curve of the relationship between the hydrometer reading and the effective sedimentation depth of soil particles (L). Substitute the different L values measured into formula (5), calculate the corresponding L values, and draw a curve of the relationship between the hydrometer reading and the effective sedimentation depth of soil particles (L) (Figure 1). Or the hydrometer reading can be directly listed on the right side of the effective settlement depth line in the Stokes formula nomogram. In this way, not only can the hydrometer reading be directly converted into the effective settlement depth (L) value of the soil particles from the curve, but the hydrometer reading and other values can also be used to find the corresponding soil particle diameter (D) on the Stokes formula nomogram. b) Hydrometer scale and meniscus correction.
The hydrometer must be calibrated before use, which is the scale correction. In addition, the hydrometer reading was originally based on the lower edge of the meniscus, but in actual operation, due to the turbidity of the suspension, only the upper edge of the meniscus can be used for reading, so the meniscus correction is necessary. During calibration, scale correction and meniscus correction can be combined. The calibration steps are as follows: Step 1: Prepare standard solutions of different concentrations: According to the values listed in the third column of the scale and meniscus calibration calculation example table of type A hydrometer (Table 2), accurately weigh the sodium chloride dried at 105°C, prepare the sodium fluoride standard series solution (the second column in Table 2), make up to the volume in a 1000mL volumetric flask, and pour into the sedimentation cylinder respectively. The liquid temperature is kept at 20°C during preparation, which can be carried out outside the constant temperature room or in a constant temperature water tank. Step 2: Determine the actual reading of the hydrometer: Place each sedimentation cylinder containing different complex sodium standard solutions in a constant temperature room or a constant temperature water tank. 5
NY/T1121.3—2006
The liquid temperature is kept at 20°C, and the solution in the cylinder is stirred with a stirring rod to make it evenly distributed. Place the hydrometer to be calibrated in the sedimentation cylinder containing each standard solution (from small to large concentration) in turn, and measure the actual reading of the hydrometer (based on the upper edge of the meniscus) at 20°C, measure twice in a row, and take the average value (the fifth column in Table 2). The difference between the theoretical reading of the hydrometer (i.e., the accurate reading, see the first column in Table 2) and the actual average reading (the fifth column in Table 2) is the scale and meniscus correction value (the sixth column in Table 2). In practical applications, pay attention to the positive and negative signs of the correction value to avoid mistakes. Table 2 Example of calculation for scale and meniscus correction of Type A hydrometer Table Accurate reading of hydrometer at 20℃, g/L
Standard solution at 20℃
1.004.465
1.035 631
Amount of sodium chloride required per liter of standard solution, g
Temperature when reading,
Average reading measured by the hydrometer during calibration, g/
Scale and meniscus correction value, L
Step 3: Draw the scale and meniscus correction curve of the hydrometer: Based on the actual average reading and correction value of the hydrometer, draw the scale and meniscus correction curve on grid paper with the actual average reading of the hydrometer as the horizontal coordinate and the correction value as the vertical coordinate (Figure 4). According to this hydrometer number
hydrometer scale
Figure 4 hydrometer scale and meniscus correction curve, the actual correction can be made to the readings measured when the hydrometer is used for particle analysis. c) Temperature correction.
Soil fill hydrometers are all calibrated at 20℃. The change of measurement temperature will affect the bubble volume and water density of the hydrometer. Generally, correction is made according to Table 3:
d) Soil particle specific gravity correction.
The scale of the hydrometer is based on the soil particle specific gravity of 2.65. When the soil particle specific gravity changes, the hydrometer reading can be multiplied by the correction value listed in Table 4 for correction. If the difference in soil particle specific gravity is not large, it can be ignored. e
If the calibration of the hydrometer is not considered, a blank determination is made in the hydrometer method (i.e., the same amount of dispersant as that added to the sample is added to the reduction tube, and distilled water is added to 1L, and the determination is carried out under the same conditions as the sample to be tested), and the blank value is subtracted during the calculation, the steps of meniscus correction, temperature correction and dispersant correction can be omitted.) Many tedious calculations and drawings of soil particle analysis can be processed by microcomputers. NY/T1121.3—2006
name) When adding dispersant to disperse the sample, in addition to the boiling method, the vibration method and grinding method can also be used. 3 Type A hydrometer temperature correction table
Suspension temperature,
10.0~10.5
14.0-14.5
Specific gravity of soil particles
Correction value
Correction value
Sensing liquid temperature,
Soil particle weight
Correction value
Type A hydrometer soil particle gravity correction value
Correction value
Soil particle gravity
Suspension temperature,
Correction value
Specific gravity of soil particles
Correction value
Correction value
NY /T1121.3—2006
A.1 Scope of application
Appendix A
(Normative appendix
Determination of natural soil moisture content
This method is applicable to the determination of moisture content of various types of soil fills except organic soil (soil containing more than 200/k of organic matter) and soil containing a large amount of stone sound.
A.2 Summary of the method
The soil sample is dried in a constant temperature drying oven at 105℃±2℃ to a constant weight, and the soil fill moisture content is calculated from the change in soil mass. A.3 Main instruments and equipment
1) Balance: sensitivity 0.01g.
2) Electric constant temperature drying oven.
3) Aluminum box.
4) Desiccator: Contains color-changing silica gel or anhydrous calcium chloride. A.4 Analysis steps
Take an empty aluminum box, number it, and place it in a 105°C constant temperature drying oven for 2 hours. Move it into a dryer and cool it for about 20 minutes. Weigh it on a balance to an accuracy of 0.01gmo). Take about 10 of the sample to be tested and spread it flat in the aluminum box. Weigh it to an accuracy of 0.01g (m1). Tilt the box lid on the aluminum box and place it in a constant temperature drying oven preheated to 105°C ± 2°C for 6h~8h (generally, samples are dried for 6h, and samples with high water content and heavy texture need to be dried for 8h). Take it out, cover the box lid tightly, move it into a dryer and cool it for 20min~30min. Weigh it to an accuracy of 0.01g (m2). Two parallel determinations should be performed for each sample.
A.5 Result calculation
2ml-m2×1000
Moisture (analytical basis), g/kg=
m1-m2x1000
Moisture (dry basis) g/kg
Where:
Mass of the dried empty aluminum box, in grams (g): moWww.bzxZ.net
Mass of the aluminum box plus the sample before drying, in grams (g); m2Mass of the aluminum box plus the sample after drying, in grams (g). The results of parallel determinations are expressed as arithmetic mean values, and integers are retained. A.6 Precision
The absolute difference allowed for parallel determination results is: for moisture content <50g/kg, the absolute difference is ≤2g/kg; for moisture content 50~150g/kg, the absolute difference is ≤3g/kg; for moisture content >150g/kg, the absolute difference is ≤7g/kg. A.7 Precautions
1) The desiccant anhydrous calcium nitride or color-changing silica gel in the dryer should be replaced or treated frequently. 8
Strictly control the constant temperature conditions. If the temperature is too high, the soil organic matter is easy to carbonize and escape. NY/T1121.3—2006
According to the conditions of the analysis steps, the sample can be dried to a constant weight after 6 hours. The accuracy of weighing should be determined according to the requirements. If the measurement requires 3 significant figures, the weighing should be accurate to 0.001g. 4)
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