Characterizing Particle Size and Shape of Sediment and Soil from the Earth, the Oceans and the Moon

Soil gathered from various terrains consists of several characteristics, offering fingerprints to their origin. As per the International Union of Soil Science (IUSS) standard, the soil category could be categorized as clay, fine sand, silt, coarse grain, and gravel.

Image Credit: Bettersize Instruments Ltd.

One more standard system by the United States Department of Agriculture (USDA) classified the sand into eight classes, as displayed in Figure 1.¹

Figure 1. Classification of soil in different systems. Image Credit: Bettersize Instruments Ltd.

The primary categories of soil and sediment analysis consist of hydrology and geology studies. In hydrology studies, the analysis of sediments offers significant data for plate tectonics and environmental watershed sustainability. In geology studies, soil samples are studied to detect climate change and pollution.

Hydrology

River mark changes as a result of modifications in particle size. Sampling at the same site in different years is essential to track particle size fluctuations and evaluate the threat of flooding.

Examination of marine sediments is hard as the largest particles may be more than a centimeter, while the smallest particles are just a few micrometers in size. Sieving consists of a limited sensitivity to fine particles, and laser diffraction has the same issue on coarse particles.

A solution to this is to integrate the sieving technique and the laser diffraction method, where sieving eliminates the millimeter particles, and laser diffraction quantifies the minus-mesh particles.

Geology

The analysis of soils is important as the soil can impact the lives of human beings. Soil status is closely related to construction, agriculture, and the surrounding. Soils and sediments are also directly linked to ecology.

For the role of soil in ecology to be explored, researchers examine all chemical, physical, and biological ideas of the soil. An extensive analysis of the soil would include particle size, density, shape, fossil, organic compounds, elemental analysis, etc.

While examining the physical properties of soils and sediments, particle size and shape are the main parameters to quantify. Soil samples are known to be polymorphic and always cover an extensive size distribution range.

The Bettersizer S3 Series examines the particle size over an extensive range from 0.01 μm to 3.5 mm. This completely covers all classes from clay to gravel. The Bettersizer S3 Series integrates two methods in one instrument, executing both laser diffraction and dynamic image analyses.

Consequently, the particle size and shape of the soil sample could be examined in one measurement. The Bettersizer S3 Series is utilized in several universities and laboratories to quantify soils and sediments. The study lists three various applications spanning lunar desert, regolith, and marine sediments.

Measurements

Lunar Regolith²

The first sample is lunar regolith (LR) returned from the moon by the Chang’E-5 (CE-5) mission. The sample was obtained by Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology (CAST).

In history, the first lunar sample was collected in 1976, and only the Soviet Union and the United States had gathered lunar samples in the 20^th century. In 2020, CE-5 took 1,731 g of Lunar samples back to earth. Figure 2 displays the sampling site of CE-5.

The Qian Xuesen Laboratory was the first group of laboratories that have been authorized to examine the lunar regolith.

Figure 2. Chang’E-5 on-site image for before and after sampling. Image Credit: Bettersize Instruments Ltd.

The Bettersizer S3 Plus was utilized to offer both particle shape analysis and particle size measurement. As per the map of single-particle images in Figure 3, the soil includes very small particles as well as coarse particles.

Figure 3. Single-particle images, circularity, and particle size distribution. Image Credit: Bettersize Instruments Ltd.

As a whole, the 120,597 particles examined have a particle size distribution between 15.0 and 438.2 µm. The average circularity of particles is 0.875, and just 10% of particles consist of a circularity smaller than 0.805. In this instance, the lunar regolith at the CE-5 sampling site is even in shape.

Just as the several different terrains on earth fall into various categories, the same is true for various lunar terrains. The Bettersizer S3 Plus allows researchers to gain a better understanding of soil samples and sheds light on the history and the progress of the moon and the earth itself.

Marine Sediments

The marine sediment samples are obtained from the National Marine Environmental Monitoring Center with three distinct size distributions. The Bettersizer S3 executed the measurements at the Bettersize laboratory. As displayed in Figure 4, the particle sizes of three samples tend to increase from top to bottom.

Figure 4. Marine sediment samples. Image Credit: Bettersize Instruments Ltd.

Table 1. Bettersizer S3 size results on three samples. Source: Bettersize Instruments Ltd.

In Table 1, the particle size values are listed, denoting that all three samples span an extensive distribution range. Sample A has the smallest particle size distribution of the three samples, where there is a span of more than 400 μm between D10 and D90 values.

When compared to sample C, samples A and B have closer particle size values.

Sample B includes extremely coarse particles, which heavily impact the volume-based particle size distribution. By image analysis in Figure 5, single-particle images have been displayed, and it can be seen that the particle size of sample A is comparatively even, while sample B consists of oversized particles in it.

Figure 5. Image analysis of sample A (top) and sample B (bottom). Image Credit: Bettersize Instruments Ltd.

According to the graph of sample B in Figure 6, at least two peaks appeared, indicating different particle size groups.

Figure 6. Particle size distributions of the three samples. Image Credit: Bettersize Instruments Ltd.

The Bettersizer S3 Series has a high resolution in differentiating different particle size groups. The measurement used the combined test because the laser diffraction excels at the fine and middle ranges and the image measurement has high accuracy for the coarse range.

Desert and Standard Sand³

The Federal Institute for Geosciences in Hannover developed an experiment to compare desert sand and standard sand to examine if desert sand could replace standard sand that is utilized in the construction industry.

All three measurement modes are utilized: dynamic image analysis, laser diffraction, and a combination technique of laser diffraction and dynamic image analysis. From Figure 7, it can be observed that dynamic image analysis and integrated analysis display a similar particle size distribution graph for the standard sand sample.

Figure 7. Particle size distributions of desert and standard sand. Image Credit Bettersize Instruments Ltd.

The standard sand sample contains several coarse particles, which are lacking in the desert sand sample. As displayed in Table 2, the desert sand consists of a similar D10 value to standard sand, nearly 220 μm. But the D90 values of standard sand and desert sand are nearly 1800 μm and 740 μm, respectively.

Table 2. Typical percentage values for the particle size distribution. Source: Bettersize Instruments Ltd.

Table 3. Typical individual particles shape parameters. Source: Bettersize Instruments Ltd.

Parameters	Desertsand		Standard sand
Image
Diameter / μm	1986	1872	2576	2320
L/ D-value	2.554	1.662	1.537	1.255
Image
Diameter / μm	1464	1312	1555	1543
L/ D-value	2.13	1.518	1.197	1.47
Image
Diameter / μm	994.3	988.2	1032	1028
L/ D-value	1.463	1.849	1.014	1.034

Excluding the variations in size that laser differentiation exhibited, there are considerable differences in shape. As per the dynamic image analysis in Table 3, the comparable diameter of desert sand is smaller compared to the standard sand.

The big variation between them is the L/D value. As per Figure 8, the standard sand has an average L/D value close to 1, but the L/D value of the desert sand varies at greater values compared to that.

Figure 8. L/D value distribution of desert sand and standard sand. Image Credit: Bettersize Instruments Ltd.

It is not possible to apply desert sand as a construction material due to the lack of middle and large particles. However, if medium and coarse sands could be added to the desert sand in the correct ratio, desert sand can be utilized as a substitute for building material.

Conclusion

The most crucial challenge of soil and sediment measurements is precisely quantifying the wide distributed samples. The Bettersizer S3 Series consists of a dynamic image analysis system and a laser diffraction system. It is perfectly suited for quantifying wide-size distribution samples like soils.

The Bettersizer S3 Series offers reliable particle size and shape outcomes to suit customer needs.

References

1. Madhan Mohan.M and Prabhu Prasadini. 2019. Manual on Practical soil physics. Regional Agricultural Research Station, Tirupati-517 502, Andhra Pradesh, India. Pp 72.
2. H. Zhang, Size, shape, and composition of lunar samples returned by Chang’E-5 mission, Science China Physics, Mechanics & Astronomy. 65, 000000 (2022). https://doi.org/10.1007/s11433-021-1818-1
3. Suitability of desert or recycling sands as raw material for concrete production. 3P Instrument. https://www.bgr.bund.de/DE/Gemeinsames/Nachrichten/Aktuelles/2019/2019-08-06_wuestensand.html

This information has been sourced, reviewed and adapted from materials provided by Bettersize Instruments Ltd.

For more information on this source, please visit Bettersize Instruments Ltd.