Fungi-Powered Phytoremediation: How Mycorrhizal Soil Amendments Enhance Spider Plant Formaldehyde Removal

Overview

This study builds on last year’s research demonstrating that spider plants (Chlorophytum comosum) reduce formaldehyde (HCHO) levels in polluted air in a sealed environment. This year, I tested whether arbuscular mycorrhizal fungi (Rhizophagus irregularis) and biochar – individually and combined – affect spider plant’s ability to remove HCHO. I hypothesized that the combination would have a better effect on the air quality than if they were alone, specifically on HCHO levels. Five treatments (n=4) were tested in sealed 75 Liter boxes: a no-plant/no-soil control, sterile soil, fungi-amended soil (0.25g/pot), biochar-amended soil (10% w/w), and fungi + biochar combined. Each box was exposed to pollution from a controlled fire, with HCHO levels recorded every 15 minutes for three hours using calibrated air-quality monitors under indirect sunlight. Soil treatments were the independent variable; HCHO and air-quality parameters were dependent variables; fire, box size, and duration were controlled. Soil pH was measured pre- and post-trial to see if treatment affected soil chemistry. One-way ANOVA revealed significant treatment differences (F(4,15)= 10.05, p= 0.0004). The no-plant control showed a ~96% HCHO increase, confirming the plant’s filtration role. Sterile soil reduced HCHO by 71%, biochar by 78% SD = 24.8% (p = 0.382 vs. sterile), fungi by 85% SD =2.64% (p = 0.021 vs. sterile), and fungi + biochar by 86.7% (p = 0.576 vs. fungi alone), showing no statistically significant benefit from biochar. pH analysis revealed biochar alone dropped soil pH to 3.5-4.0, creating a very acidic environment that possibly inhibited root function, explaining its high variability and non-significant results. Fungi alone raised pH to 7.0-8.0, optimizing microbial activity. The combination stabilized pH at 7.0-7.5, with fungi buffering biochar acidity. The hypothesis was not supported: fungi alone sufficed for enhanced phytoremediation. Using Claude AI and Google Colab assistance, a predictive model was created estimating HCHO from 75-180 minutes using only the first hour of data, achieving a MAPE of 6.9% or 93.1% accuracy. A custom web app built with Claude AI estimates the number of fungi-amended spider plants needed to reduce HCHO below the WHO-threshold of 0.1 ppm (Golden R. (2011) by room size and starting levels. In the future, I will extend the duration of trials, advancing a low-cost bioengineered solution for spacecraft, schools and low-income housing near freeways.

Competition history

• CSEF 2026 Earth & Environmental Sciences (Track 2) (Junior Division) · Entry J-09-13

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