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Splash on Earth: A Case Study on the Influence of Flour-Based Eco-Paint on Urban Soil Quality

(This article is in reference of Emily Xu’s research paper currently under review for the Journal of Student Research)




Over the last year, I have conducted research on an environmental-art event that I slowly watched grow: Splash on Earth. As an event that redirects food waste from landfills and transfers it into something that can be used for entertainment, I wanted to investigate the biochemical and environmental benefits Splash on Earth has.


Abstract

Environmental health and soil quality is a growing concern in urban communities as environmental degradation becomes more prevalent. In order to raise awareness on environmental issues, Splash on Earth is an initiative that has been implemented in communities around Toronto, Canada, utilizing flour-based eco-paint to create temporary ground mural drawings and bring attention to food waste. As the eco-paint becomes a byproduct when it rains and inevitably seeps into nearby soil, it raises questions on whether its interaction with soil microorganisms can positively increase soil microbial activity and function. As an indicator of soil quality, a healthy soil microbiome community is essential to supporting efficient decomposition rates, moisture, and nutrient levels while also being a defense against pollutants and heavy metal contaminants. In this study, a mixed study that includes four main tests were used to determine the potential influence flour has on soil microbial in three soil samples, including: CO2 concentration, plant growth, cotton strip degradation, and worm survival rates. From these tests and the known interrelationship between each factor, this research effectively identifies the impact flour has on microbial activity in soil, analyzes potential limitations to revising soil health, and provides reasoning for Splash on Earth’s environmental benefits.


Introduction

With growing awareness of environmental issues and the need for local change to solve this global climate crisis, sustainability initiatives are recognized as an efficient method to promote climate action. One community initiative that successfully engages communities around Toronto, Canada is Splash on Earth, which utilizes eco-friendly paint made from expired flour for temporary ground mural drawing. While the exponential rate of participation illustrates the social benefits of this initiative, the use of food waste has sparked questions as to whether the eco-paint has environmental benefits or drawbacks on soil quality in the parks where events are conducted. This case study will help identify the potential impact of flour-based paint on microbiological activity in soil—a key indicator of soil quality.


Current Findings:

There are several main concepts that are of focus when understanding the significance of soil quality. As stated by the Natural Resources Conservation Service in the USA, soil quality can entail: habitat provision roots, soil organisms, element cycling, decomposition, soil structure maintenance, biological population regulation, water cycling (infiltration, retention, percolation), and organic matter cycling (humus formation, C sequestration) (Bünemann et al., 2018). Numerous other studies have worked to confirm the relationship between soil quality and the benefits of maintaining productivity in ecosystems.


In more recent literature, there is a growing focus on the interconnection between various environmental concepts. For instance, questions about the significance of healthy soil and human well being are being asked and investigated. But on top of this, issues related to soil microbiomes, nutrient levels, pollutants, and the quality of plant growth are being researched more frequently.


In order to conduct my research, I narrowed the element of investigation to focus on carbon dioxide levels. This preliminary set of data is predicted to also influence plant growth, rate of cotton decay and worm survival, and provide a better understanding on soil microbial levels. Numerous studies, such as the paper published by Schloter et al. on microbial indicators, investigate soil quality have utilized these simple testing methods as a way to better understand how living organisms in soil interact with a whole ecosystem.


Testing CO2 (ppm) levels released from soil is a potential indicator of bacteria and microorganism populations. While soil is known as a carbon sink, CO2 is also a byproduct of aerobic respiration (the chemical process by which oxygen is used to convert carbohydrates into consumable energy) by microbial communities (National Cancer Institute, n.d.). In most cases, this is a process when enzymes catalyze the depolymerisation of soil macromolecular constituents. The dissolved and exposed organic carbon is then uptaken by microbial cellular metabolism to produce CO2 and other biomasses. Soil microbial provides reference to the health and population density, which also play a significant role to other ecosystem processes such as photosynthesis and decomposition. A positive feedback of healthy soil microbes is elevated CO2, which increases atmospheric CO2 and stimulates photosynthesis. This relationship between CO2 levels, microbial health, and plant photosynthesis is further measured through plant growth.


On the other hand, the purpose of using cotton is because the polymers that it is composed of is similar to leaves. Given that carbohydrate is the main component of plant litter and compost, and the most abundant organic polymer on earth, the Cotton Strip Soil Test can effectively predict the rate of decomposition of natural organic matter by mimicking it (Colas et al., 2020).


Additionally, worms were used to identify liveability of the soil. As suggested by the Agriculture and Horticulture Development Board, earthworms are sensitive to pH, waterlogging, compaction, and the availability of organic matter (Bennett, n.d.). The amount of worms that survive under new experimental conditions should tell us more about the important qualities used to measure soil quality–and potential changes in composition.


In this study, the treatments are organized as shown in the tables below.


Table 1

Different Flour Treatments for Each Soil Sample

Table 2

Mass of soil used for each experiment.

On top of the different experimental measurements, this research performs a mixed study, using three different soil samples: store-bought potting soil, backyard soil that experiences minimal maintenance, and lastly, from a park located near a road. It is assumed that there is a range in soil quality between the three samples, with the potting soil being the healthiest and fertile, and the sample from the side of the road being the most polluted.


So, what were the results?

Based on the two methods used to measure CO2 concentration, higher concentrations of flour-treatment resulted in greater levels of CO2. This positive trend is the same for all three soil samples and is illustrated in Figure 1, 2, and 3.


Figure 1

CO2 concentration measured using PASCO sensors for Soil Sample 1


Figure 2

CO2 concentration measured using PASCO sensors for Soil Sample 2


Figure 3

CO2 concentration measured using PASCO sensors for Soil Sample 3

As for plant growth, with higher concentrations of flour, the average height of both radishes and lettuces increased.


Figure 5

Lettuce Height After 21 Days in Different Soil Samples and Flour Treatments (g)


Figure 6

Radish Height After 21 Days in Different Soil Samples and Flour Treatments (g)



Both the cotton degradation and worm survival rate experiments further present the same positive trend; with higher flour concentrations, the amount of cotton strip degraded and the rate of worm survival increased.

Image 1

The four cotton strips sowed and extracted from Soil Sample 1, Control (0 g

of flour)


​Image 2

The four cotton strips sowed and extracted from Soil Sample 1, Treatment 1 (25 g of flour)


Image 3

The four cotton strips sowed and extracted from Soil Sample 1, Treatment 2 (50 g of flour)


​Image 4

The four cotton strips sowed and extracted from Soil Sample 1, Treatment 3 (75 g of flour)


Image 5

The four cotton strips sowed and extracted from Soil Sample 1, Treatment 4 (100 g of flour)



Overall, for each experiment, soil samples that were treated with 100g of flour showcased characteristics associated with improved soil quality. However, it is also important to note that statistical analyses calculated in this research—such as comparing linear regression data and ANOVA test—also suggest some discrepancies that are possibly due to the presence and quantity of contaminants originally in soil. Additionally, limitations related to the timing of experiments, differences in physical characteristics of soil samples, and the scope of data are all challenges that might limit the significance of the conclusion made by my research.


In order to further replicate realistic outcomes of hosting Splash on Earth, food colouring and natural dyes can be analyzed. Specifically, the consideration of natural or chemically synthetic dye can be measured to identify its potential effects on improving soil quality as seen in soil treated with pure flour. Additionally, with the support of advanced experimental instruments, the ability to identify specific microbial communities and their densities could provide a more confident conclusion of the relationship between flour treatments and microbial activity. Testing for the DNA of specific microorganisms and changes in their population is another way to confidently measure soil quality.


This study reveals the significant environmental impact a simple community initiative can accomplish and confirms the hypothesis that flour-based eco-paint can improve soil quality. While the conditions that each soil sample experiences might not be an accurate representation of the amount of flour that actually decomposes into soil, a positive trend is nevertheless observed.


If you would like to see the full report of my research, please keep an eye out for an official publication!


Thank you to my sister and amazing mentors, Dr, Tescuiba and Mr. Grisé, for all their guidance and support throughout this research journey. Thank you to SOLVITA for providing me with their carbon dioxide testing probes. As I continue off to university, I am excited to continue understanding various topics related to soil health and even delve into new and arising climate issues.


Reference:

Bennett, A. (n.d.). Soil macrofauna – earthworms. AHDB. https://ahdb.org.uk/knowledge-library/soil-macrofauna-earthworms


Colas, F., Woodward, G., Burdon, F. J., Guérold, F., Chauvet, E., Cornut, J., Cébron, A., Clivot, H., Danger, M., Danner, M. C., & Pagnout, C. (2019). Towards a simple global-standard bioassay for a key ecosystem process: organic-matter decomposition using cotton strips. Ecological Indicators, 106(105466). https://doi.org/10.1016/j.ecolind.2019.105466


National Cancer Institute. (n.d.). Definition of aerobic respiration - NCI Dictionary of Cancer Terms - NCI. National Cancer Institute.


Schloter, M., Nannipieri, P., Sørensen, S. J., & van Elsas, J. D. (2018). Microbial indicators for soil quality. Biology and Fertility of Soils, 54, 1-10.

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