Tire-Wear Particles and Grass Germination

ISEF Category: Earth and Environmental Sciences

Subcategory: Environmental Effects on Ecosystems  ·  Difficulty: Advanced  ·  Setup: School Lab  ·  Time: Full Year

The Hook

Tiny particles from car tires wash off roads every day. They can end up in gutters, streams, and soil. That matters because grass seeds are often the first step in restoring a damaged habitat. If those particles change which grasses sprout first, they could tilt the whole plant community.

What Is It?

This project looks at tire-wear microparticles, which are tiny bits released when tires rub against pavement. Rain can carry them into gutter sediment, the gritty material that collects along curbs and drains. You sort the particles by density, then test whether they change seed germination in soil-cup trials. Think of it like adding a small, dirty ingredient to a seed-starting mix and watching which seeds still manage to break through.

You can compare native grasses and invasive grasses side by side. Germination means a seed starts growing and sends out a root or shoot. A mixed-effects model lets you handle repeated cups, seed batches, and trial runs without pretending every seed is fully independent. That gives you a cleaner read on whether the particles matter, and whether one grass group is more sensitive than the other.

Why This Is a Good Topic

This is a strong science fair topic because you can test a real environmental exposure with clear outcomes, like percent germination, time to sprout, and early seedling growth. It connects to road runoff, soil health, and restoration ecology, so the work feels relevant outside the lab. You can learn how to collect field samples, separate particles, run controlled soil-cup trials, and analyze data with a mixed-effects model. Those are real research skills, not just classroom lab tricks.

Research Questions

• How does tire-wear microparticle concentration affect germination rate in native grasses?
• What is the effect of tire-wear microparticles on invasive grass seedling emergence?
• Does particle density fraction change the strength of germination suppression?
• To what extent do native and invasive grasses differ in sensitivity to tire-wear microparticles?
• Which soil-cup conditions best separate particle effects from moisture or sediment effects?
• How does seed batch variation influence the observed response to tire-wear microparticles?

Basic Materials

• Native grass seeds and invasive grass seeds with known species names.
• Gutter sediment samples from roadside collection points.
• Density separation setup, such as salt solutions, graduated cylinders, and filter paper.
• Small planting cups or cells with drainage trays.
• Potting soil or standardized sand-soil mix.
• Digital kitchen scale with 0.1 g accuracy.
• Spray bottle or measured watering system.
• Labels, permanent marker, and notebook.
• Ruler or calipers for seedling measurements.
• Smartphone camera for consistent photo records.

Advanced Materials

• Analytical balance.
• Centrifuge tubes and a benchtop centrifuge for fraction cleanup.
• Sieve set for particle-size sorting.
• Stereo microscope for particle inspection.
• Vacuum filtration setup.
• Drying oven or desiccator for sample mass control.
• Soil moisture probe.
• Light meter for growth chamber checks.
• Growth chamber or controlled-environment shelf system.
• Access to R, Python, or similar software for mixed-effects modeling.

Software & Tools

• R: Fits mixed-effects models and compares native versus invasive responses with reproducible statistics.
• RStudio: Gives you a clean workspace for coding, plotting, and model checking in R.
• Python: Helps you organize data tables, make figures, and run basic statistics if you prefer code.
• ImageJ: Measures seedling length or green area from photos under consistent lighting.
• Google Sheets: Tracks treatments, replicates, and germination counts in an organized spreadsheet.

Experiment Steps

1. Define the exposure variable you will change first, such as particle fraction, particle dose, or both.
2. Choose matching native and invasive grasses with similar seed size, dormancy behavior, and habitat context.
3. Plan how you will separate particle effects from sediment effects using controls and blank soil cups.
4. Build a sampling plan that treats each cup, seed batch, and collection site as separate sources of variation.
5. Decide which response measurements matter most, such as germination, emergence speed, and early seedling growth.
6. Design your analysis plan before collecting data so you can test fixed effects, random effects, and species differences clearly.

Common Pitfalls

• Using mixed roadside sediment without separating particle fractions, which makes it impossible to know whether tire wear caused the effect.
• Comparing different grass species with different dormancy patterns, which can hide or fake a treatment response.
• Letting moisture vary between cups, which changes germination more than the microparticles do.
• Counting sprouted seeds at inconsistent times, which distorts emergence speed and final germination rate.
• Treating every seed as fully independent, which inflates sample size and weakens the mixed-effects analysis.

What Makes This Competitive

A competitive version of this project would do more than report a yes-or-no effect. You would separate particle fractions carefully, compare native and invasive grasses with matched controls, and use a mixed-effects model that respects cup-to-cup and batch-to-batch variation. Strong projects also test whether the response changes with particle fraction or source site, not just total sediment load. That kind of design shows you understand both ecology and statistics.

Project Variations

• Test whether roadside runoff from different land uses changes the strength of germination suppression in native grass species.
• Compare tire-wear microparticles against other gutter particles, such as leaf litter or mineral sediment, to isolate the particle type that matters most.
• Measure seedling root length and shoot length instead of only germination, to see whether early growth responds more strongly than sprouting does.

Learn More

• USGS Water Science School: Search for background on urban runoff, stormwater transport, and sediment movement.
• NOAA National Ocean Service education pages: Look for clear explanations of pollution transport and watershed pathways.
• PubMed: Search review articles on tire wear particles, microplastics, and plant germination.
• USDA Forest Service research pages: Find studies on native plant establishment, invasive grasses, and restoration ecology.
• R for Data Science: A free online book that helps you clean data, make plots, and fit models in R. Search for the current online edition.