Abstract
The overall purpose of this study was to conduct a detailed comparison of particle size distributions in soil samples collected from distinct environments: a river basin and a garden. These environments present unique soil compositions, and textures influenced by their respective ecological and functional roles. By employing the Beckman Coulter Laser Diffraction Particle Analyzer, this study provides precise measurements and insights into the physical structure of the soil particles from each respective location. The river samples included clay-rich soils and saturated sediments retrieved from beneath the riverbed, representing a dynamic and water influenced nature of fluvial systems. On the other hand, the garden soil collected originated from a cultivated area used for food production, proven by the soil’s nutrient-rich and tilled composition. The results revealed notable differences in particle size distribution curves, reflecting the contrasting formation processes and usage of these soils. While similarities were observed in the general structure of the particle size across the two samples, key distinctions emerged especially in the proportion of fine particles such as silt and clay. River basin soils were found to have a higher fraction of fine particles, indicative of sediment deposition under aquatic conditions, whereas garden soil exhibited a more balanced distribution, optimal for agricultural productivity. These differences between the two different types of soils underscore the critical role of soil texture in influencing water retention, nutrient availability, and overall ecosystem health. These findings also highlight the importance of particle size analysis in understanding soil functionality in diverse environments. This research goes on to provide valuable data to the field of soil science and emphasizes the necessity of integrating soil composition studies into sustainable land management practices.
Keywords: Laser Diffraction Particle Size Analyzer, Soil Particle Analysis, Silt, Wet-Soil, Clay-like Soil, Measure of Central Tendencies
Introduction
River basins are one of the most pivotal ecosystems on earth, from providing abundant water resources essential to human life, to aiding in agriculture, river basins are vital for the well being of the earth. Unfortunately, due to contamination, destruction of environments by human beings, exploitation of natural resources, and declining cleansing capacities of river basins themselves, river basins are under serious threat. Likewise, gardens play a major role in human life. For the average person, 30% of the food they eat comes straight from their own or another garden. Unlike river basins, however, gardens over the last few years have been growing exponentially. In the past five years, spending on food gardening has increased by over 40%, the number of urban gardeners has grown by about 30%, and gardening has become a prominent feature in many backyards. The main similarity between river basins and gardens comes at the bottom of both systems, the soil. Soil is one of the largest systems on earth and is the reason foods and crops grow and flourish. Soil is a natural body composed of solids, minerals, and organic matter. Nevertheless, soil performs vital functions to sustain plant and animal life. It helps regulate water flow in certain areas, filters and buffers pollution, and provides physical stability to all organisms dependent on it. In this study soil samples from river basins are compared to soil samples from gardens to find similarities and differences of the two types of soils performing two completely different functions. To achieve this, soil particle analysis is implemented. Soil Particle Analysis is a widely used method for comparing soil samples from various sources. The Soil Particle Analysis method used for this study includes the use of the Laser Diffraction Particle Size Analyzer. The method helps configure the multitudes of the individual soil particles inside the sample. When multiple samples are analyzed, similarities and differences can be identified. Key comparisons include the level of soil acidity, micronutrients, organic matter, heavy metals, particle sizes, soluble salts, and even levels of nitrogen. Although soil analysis has many different implementations, it is mostly used in predicting natural occurrences such as erosions and landslides. In addition, soil analysis can also be used during crime scene investigations. Soil samples are used in forensics to identify blood traces or other small details that help with identifying criminals. In this study two different types of soil samples from the same river basin are compared with garden soil collected from a garden two miles from the river. The aim of the study is to identify all of the similarities and differences between wet soil from a creek, silt a few miles away from the creek, and garden soil from the same distance. Garden soil and natural soil exhibit many differences. Garden soil, which has been modified to be optimal with gardening and planting vegetation is topsoil, enriched with compost and other organic matter making it more nutrient rich. Additionally, garden soil also has a heavier texture, and holds much more water for a longer period of time. There are many differences associated with garden soil and natural soil, but there are some similarities. Garden soil consists mostly of natural soil and in addition both soil types have similar acidity levels.1
Methodology
Particle Analyzer Analysis
The Laser Particle Size Analyzer is a device used to measure the size distribution of sediment particles. For this study, the Laser Particle Size Analyzer was utilized to measure the sizes of varying sediments and materials from three distinct sediment samples. The Laser Particle Size Analyzer gives a detailed graph of the particle sizes, the measure of central tendency, and percentages of each category size to make interpreting the results easier. The following image (Figure 6) gives an example of how the Laser Particle Size Analyzer functions and analyzes the particles.
Experiment
The experiment was set out to compare and contrast three types of soils: garden soil, commonly used for growing vegetation; silt; and wet soil, which was scooped out of a riverbed. This research allows for comparisons among those samples, answering questions about similarities and differences in their particle size distribution and hence showing their differing properties and uses. The first sample was collected from a specific geographic location: latitude and longitude coordinates of 37.545798, -121.962586, within the bed of the stream flowing out of Lake Elizabeth in Fremont, California (Figure 1). This site was chosen for sampling because it represents unique environmental conditions that influence the size distribution of particles in the soil as a result of the constant flow of water through it and the deposition of sediments that occurs in stream beds. The second sample came from another location close to Lake Elizabeth, from a picnic area with coordinates 37.545449, -121.962650. This specific site was selected because, while still proximal to the stream, it is a more stabilized location where soil erosion and sediment deposition would presumably be unlike that occurring within the stream bed. The final garden sample was collected from a residential house garden several miles away from the lake and stream. This garden was selected for its rich soil and easy accessibility. This soil is expected to have different attributes as garden soil has different properties than subsoil from the river.
Method Selection
Located in Santa Cruz, California, this high-tech equipment was a vital part of the research. It provided reliable data required for comparing the different types of soils. Other methodologies that were considered for this study in particle size analysis were the Near-Infrared Spectroscopy method and the Soil Penetrometers method. Each of these methods works in their own way and has its own set of benefits and limitations. Near-infrared spectroscopy is a method in which scattered light measures samples to determine a number of properties such as chemical composition and molecular structure. This method is very efficient and productive, however, has very low sensitivity due to the low absorption coefficients of the analyzed materials. Additionally, this technique is also indirect as multivariate calibration models have to be developed to correctly interpret the data given. The Soil penetrometer is a device to measure soil depth. It does not have the capabilities to analyze size distribution and is more commonly used to assess the strength of soil layers. Lastly, the Laser Particle Size Analyzer stands out as the most suitable method for this particular study. Its straightforward structure and high efficiency allow for in-depth research and ease of use. This method has gained significant popularity in recent scientific research as it involves high repeatability along with excellent user convenience. Very small quantities have to be produced to receive accurate and reliable results. Furthermore, the machine is designed to recover quickly, saving an abundance of time for the scientist. Utilizing the way light behaves on particles, accurate size measurements are produced. The accuracy, efficiency, and simplicity of its operation makes the Laser Particle Size Analyzer the most optimal tool for this study.
Results/Discussion
The results of this study come down to the analysis of the three samples. Sample 1, wet soil from underneath the river bed, Sample 2, clay-like soil a couple feet away from the same river bed, and Sample 3, a soil collection from a residential garden two miles away from the river basin. The images below represent the average of multiple tests run for each sample. This was done as a means to limit the margin of error and provide the most accurate statistical data.
The first variable tested from the particle analyzer included a control variable to calibrate the machinery. To initialize the machine it is vital that the volume was at 100% and there was a fine spread across the graph, which can be identified in figure 3 (the control sample). The control variable itself consisted of a saline solution stored ahead of time for the purpose of calibrating the machinery. The next sample tested was Sample 1, wet soil from beneath the riverbed. This sample was expected to have varying sizes from 0.4 to 2000 micrometers of particles and it was also expected that there would be more particles in the 40 micron range than any other size range.
Although the results shown in Figure 4 give a fine graph with varying sizes from 0.4 to 2000 micrometers, most of the particles seemed to fall under the 200 – 400 micron range condemning the prediction as false. The measures of central tendency for this sample includes a mean of 116.1 micrometers, a mode of 245.2 micrometers, and a median of 174.5 micrometers. This sample out of all the other samples had the highest moisture content as this sample was directly taken out from the lake.
The next test, Sample 2, is another sample from the river bed. However, this sample had a different texture than Sample 1. To recall Sample 1 was wet soil, Sample 2 however, had purposely been collected to be a different texture of soil, a fine soil called silt. This sample was also predicted to have a smooth curve throughout the graph. But unlike Sample 1 this sample was expected to have much larger particles as soil from a couple feet away from the river had assumed to be larger in particle size than soil underneath a river bed. The measures of central tendencies were also anticipated to be larger than for sample 1.
Just as expected, the graph for Sample 2 demonstrated a smooth curve throughout the particles analyzed; most of the particles were associated with the 400 – 2000 micrometer range, much larger than the size group for Sample 1. The central measures of tendencies also proved to be quite large compared to Sample 1. Sample 2 had a mean of 123.7 micrometers, a median of 249.5 micrometers, and a mode of 993.6 micrometers. This proves the prediction to be correct and shows us that silt soils collected away from riverbeds at Lake Elizabeth tend to have a higher differential volume than wet soils collected beneath riverbeds. Since silt has a higher differential volume than wet soil it is predicted to share more similarities with garden soil. Along with this silt has a lower moisture content than wet soil, although this is apparent as the silt is not directly connected to the water source.
Sample 3, the outlier in this study is a soil sample collected from a residential garden in Fremont, CA. This sample unlike the other two samples has a completely different function. Soil in gardens is primarily focused on helping nourish the plant and provide good nutrition. Meanwhile soil in creek beds are primarily focused on the filtration of water and the transportation of key nutrients for plant growth. Sample 3 is predicted to have the largest particle size from the three samples due to the fact that there is no factor of water. The sample graph is also predicted to be a smooth curve varying in sizes. Meanwhile the central measures of tendencies are anticipated to be far greater than Sample 1 and definitely greater than Sample 2.
Test 3 had a smooth curve along the different particle diameters like the other samples, however, surprisingly Sample 3 has a lower measure of central tendency than Sample 2. Although the mean of the garden sample is higher than that of fine soil from the river, both the median and mode of the garden soil are lower. Also, for Sample 3, the size group with the most particles associated with it is the 400 – 1600 micrometer range which is significantly lower than the group relating to Sample 2. This fact was surprising due to the presumption that garden soil has the largest particles among all soils. Meanwhile comparing this garden soil sample with the Sample 1 (wet soil), Sample 3 has a significantly higher measure of central tendency. What this final sample tells us about this study includes how the particle sizes of the garden soil sample correlate more towards very fine silt rather than the wet sediment from beneath the river bed. As predicted earlier the moisture content aided with making this conclusion since the moisture content of the garden soil also shared many similarities with the silt soil collected.
To summarize the results, all three samples, Sample 1: wet sand from beneath the river bed, Sample 2: silt from near the river bed, and Sample 3: garden soil from a residential household, exhibit similarities and differences. The similarities between the three samples include how they all include particles for almost every value given on the x axis, showing that the three samples are made up of varying sizes of particles. Along with that, all three samples have similar means as Sample 1 has a mean of 116.1 , Sample 2 has a mean of 123.7, and Sample 3 has a mean of 137.8 showing us that the overall particle composition was similar among all three samples tested. Even with all these similarities there were some factors that differed within the samples. Each sample has a significantly different measure of central tendency. Sample 1 has a rather low measure compared to the other two samples, Sample 3 falls in the middle, leaving Sample 2 with the highest measure. Additionally, each sample had a higher number of particles in a particle group and this group differed among the samples. Also, In comparison with other soils in the area such as sand, these particles have a significantly higher measure of central tendency. The conclusion we can take away from these results include how garden soil is more similar to very fine silt rather than wet soil. Another takeaway includes how very fine silt samples collected from near the river bed had the highest differential volume, while wet soil from beneath the river bed had the lowest volume. The results driven from this study also suggests many ecological implications that soil size has natural occurrences. For example, since garden soil was found to be more similar to very fine silt rather than wet soil, it may be more susceptible to erosion when introduced to water or wind. The difference in the soil composition can also influence a natural process referred to as “nutrient cycling”. Fine silt may trap organic matter and nutrients more effectively, leading to plant growth. Conversely, wet soil has lower nutrient availability, affecting overall productivity in aquatic areas.
Conclusion
It was determined that the particle size analysis between the garden soil and the riverbed soils showed a fair similarity, especially with the silt-like soils and the garden soil. A Particle Size Analyzer using Laser Diffraction technology, accounted for the successful and accurate analysis. Two sets of soil samples were gathered from two different locations in Fremont, California: the famous Lake Elizabeth and a residential backyard also located in the same city. The greater environmental issue this research raises is soil erosion. While, in most instances, it is part of the natural cycle and even sometimes quite beneficial to an ecosystem, human activities are also boosting this process to harmful levels. Several serious implications are involved with the acceleration of erosion, for if mismanaged, it could ultimately result in severe environmental degradation. Some of the major human activities, such as deforestation and habitat destruction, and some agricultural practices like the removal of trees, enhance this rapid erosion. Other human activities include overgrazing by livestock, and meddling with natural processes of plant and tree growth. This research reflects back to learning and respecting the balance of nature. It is very important that we work with nature, not against it. A lot of simple actions, like recycling, all add up to lessen the effect of global warming as a whole. Nevertheless, to bring about effective change, the public needs much more education and information on agriculture and environmental sciences. Undeniably, human activities have increased soil erosion, but this is not a trend that has to continue. Protection of land from erosion and maintenance of health for our planet can be assured only if we are sensitive to the environment by taking proactive steps for its protection and developing a deeper understanding of the impact of the actions we make.
Acknowledgements
I would like to thank my advisor Ms. Leanna Jensen from Integral for the valuable insight and research aid provided to me on this topic and my high school English teacher Catherine Martinez for her revisions and aid
Author
Ashwin Vijayasekaran is a Junior (Class of 2026) at Irvington High School in Fremont, California. This paper was inspired by his interest in biological and environmental sciences. He hopes that this independent research article will be the beginning of his journey in the field of biological sciences.
References
- Potts, Leanne. What Is the Difference Between Potting Soil, Garden Soil and Topsoil? (2024). [↩]
