Blog Post #1

Finding A Topic

When I started AP Research, I had little to no idea what I wanted to study. Based on my interests, I wanted to stay science based, but that has endless possibilities. During my summer research, I tried to focus on my interests in human biology. Notably, I found a few studies that looked at plant vascularity and I tried to compared it to the human vascular system. However, humans and plants are completely different species, but I held onto this idea. I decided to keep my focus on plants because they are so vital to the environment and survival of all organisms.

Then, one day, on social media, I saw a post showing how microplastics were found all the way on Mount Everest and even in Arctic ice. The prominent, expansive nature of these particles made me curious. I decided to look further into what we know about the impacts of these particles on the environment. I found that there are many studies done to try to collect data, however, there were many gaps that I knew I could work to solve. Depending on the results, I might be able to draw a general conclusion on the future of the environment. Additionally, since it's known that humans are constantly ingesting these particles, I may be able to draw a conclusion on how the side effects on humans will be increased.

In a final effort to emphasize the importance of these microscopic plastics, I will outline the future threats and suggest policies and laws that could help to limit the potential harm.

Current Research

As studied by the Department of Environmental Health in South Korea, a research team found evidence that the aquatic plant species, Lemna minor or duckweed, was affected by MNPs (Cui, Rongxue et al. 2023). This research project specifically looked at the effects of polyethylene terephthalate over a period of 3-day spans and over 10 generations. They studied specific areas like photosynthesis, root length, and growth rate. Their key findings proved that over the short-term project, the smaller particles had a stronger effect while over generations, the larger particles had a larger impact. These particles were <200 um, 200-300 um, and 300-500 um. The study proved that there are significant changes to plants with different sizes of MNPs, but they largely focus on physical plant health in an aquatic plant.

Another research team reviewed multiple studies and noted that their main objectives were to study MNP uptake, translocation and accumulation by focusing on a more plant-centric view (Hasan, Md Mehedee et al. 2024). Similar to Cui’s experiment, Hasan looks at plant growth, physiology, and health with exposure to MNPs specifically with soil properties and soil microbes. However, given the team's expertise in Agriculture, this experiment was set to understand long-term food security, which is another major concern. Notably, in their conclusion they present a few novel solutions like biodegradable alternatives to MNPs and advancements in waste management, along with basic policies that could reduce plastic production. With the increasing threat of plastics entering our ecosystems, these solutions are significant. Their findings suggest that soil structure is extremely important for proper plant growth and that MPs may interact with other pollutants, including heavy metals, potentially making the soil more toxic.

Additionally, a team in the Department of Agriculture in South Korea and Bangladesh point out that many studies lack a variety of particles (Y. M., Lozano et al. 2021). They often use just one size, which makes it challenging to compare plant root uptake, translocation and accumulation of MNPs. Given my parameters of budget and resources, and the fact that my main goal is to have the MNPs go into the roots, I need to get specific sizes of the particles that will go into the plants guaranteed. However, plant roots often greatly vary in width, some being 2.5 mm and others being 0.4 mm or smaller, especially when using Lactuca sativa. With this said, I plan to just use one size that will be small enough to fit into the roots, which will be around 100 nm.

Methodology

Supplies

Three hydroponic tanks with a bubbler
- From Amazon
Two sizes of microplastics
- Monodisperse Silica Microspheres (2.0g/cc, 1.54um, 1g)
- Monodisperse Silica Microspheres (2.0g/cc, 0.166um, 1g)
  - From company Cospheric (They gave a 75% discount for high schoolers in STEM)

At least nine lettuce plants - Seeds

Outline

I will have one control group and two experimental groups. A group of researchers focused on ecology and agriculture in South Korea proved that microplastics are increasingly impacting terrestrial ecosystems due to particle translocation (Hasan, Md Mehedee et al. 2024). This team notes that translocation of MNPs is highly dependent on particle size, polymer, and plant species.

With this said, I plan on studying two sizes of microplastics to see how a smaller and larger size will change the impacts. Specifically, I have two sizes of microplastics, one that is on average 1.54 um and the other that is 0.166 um, while lettuce roots can span from 2.5 mm to 0.100 um in diameter. With these two groups separate, I will be able to compare how size of the particles changes the impacts. I will separate these particles into two hydroponic tanks and using bubblers to ensure they are constantly being mixed around the tank.

*For each factor studied, I will find statistic significance*

Water Uptake

I have based my methods from a study that focused on plant water use in a controlled experiment. They outline a method called the “Reservoir Mass Method”, which requires me to weigh the entire reservoir, subtract mass loss in the evaporation-only control container and divide by number of plants (Cichello, et al. 2023). Notably, I need an evaporation-only control container to account for extra water lost. I will record these masses daily and keep them in a google spreadsheet to ensure uniformity and to make a visual at the end.

Plant Health

Once the plants start sprouting, and specifically growing roots and shoots, I will be taking a picture of the plants and rating them on a scale of 0-5 from each tank each day. Each number indicates health of the plant based on leaf color, necrosis, wilting, root browning, root length & branching and number of leaves. Then 0 indicates death, 1 is severe stress (chlorosis, necrosis, severe wilting), 3 is moderate (partial yellowing, slowed growth) and 5 is healthy (firm leaves, vivid color, no browning). This scale is often referred to as a simple scale to get overall health over periods of time.

Biomass

If I can get materials needed to dry the plants, I will have the shoots and roots dried at 60°C for 72 h, and then record their mass. I will find the average mass across the three groups to determine if there was a significant change.

Relevance

A chemical specialist, Robert Hale, emphasizes that microplastics are a result of plastics breaking down. He outlines that there has been an abundance of plastic use because of its low production cost, stability, and versatility. In fact, the website Our World In Data states that plastic production has increased 230 fold since 1950. As these plastics have broken down, there has been more exposure of the particles arising from land disposal, wastewater treatment, tire wear, paint failure, textile washing, and at‐sea losses. Notably, in recent times, microplastics have been found in Arctic sea ice, the Antarctic, remote mountain ranges, and even deep ocean trenches. The author outlines these areas to show how expansive the exposure of these particles is.

On that note, it’s important to define how these particles have impacted humans and other organisms throughout the globe. With their abundance in the air, soil, meat, plants, water, etc., it’s impossible not to consume microplastics in some way. According to a group in the Department of Medicine at Shenzhen University Medical School led by Ghulam Abbas, there are known long term consequences of microplastics (Abbas, Ghulam et al. 2025). This group identifies that human studies are still limited, especially over long-term time frames, but it is still clear that microplastics are in our bodies and can cause inflammation in our pulmonary tract, cardiovascular system and digestive organs. As microplastics enter our bodies through ingestion, inhalation, skin contact and bioaccumulation, it's important to find solutions to preventatively reducing that contact.

Now, my research question outlines how plants are affected by microplastics, looking at both their qualitative and quantitative impacts. I will be using Lettuce to see how it is affected by the plastics to then draw a larger significance on how this will impact the future with human consumption and plant health. If there are significant impacts on Lettuce plant health and evidence that microplastics went into the plant roots, this may offer insight that humans are consuming these particles through this type of plant. Additionally, if the plants begin to deteriorate, this may suggest that future implications of microplastics will lead to a decrease of food availability for humans and other species that rely on lettuce.

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