Our Proposal

Rationale

In analyzing the soil in a rain garden, we invested how much of an impact they are making to our environment. Normally when it rains, water is collected along with a lot of other bacteria, good and bad, as well as other pollutants. This is called water runoff, and it can pollute our water and cause flooding. (Soak Up the Rain: What's the Problem? | US EPA, 2023). In many urban cities, water runoff becomes incredibly dangerous with the extensive amounts of petroleum and other hydrocarbons included in it (Hong et al., 2023). With rain gardens however, pollutants are collected along with the water since it will instead be collected by rain gardens, for which it will not be as harmful. Not only were pollutants collected, but with the addition of gardens, it is possible to increase the diversity of plants and help to improve our neighborhoods. Plants need the essential nutrients and bacteria that can come from water runoff, and many studies have even shown that plants are very important in removing pollutants from the ecosystem. Rain gardens are therefore helpful for plants' health and for our health (Microbial Communities in Bioswale Soils and Their Relationships to Soil Properties, Plant Species, and Plant Physiology). 

Study Aim

Our aim of study is to analyze the differences in pH between the two sample sites and analyze the differences in bacterial biodiversity between the two sample sites. We will determine if there is any relationship between how diverse the soil is with where the sample was taken from.

Experimental Plan

Our study evaluated the differences in soil pH, soil moisture content, functional, and genetic bacterial biodiversity. The pH of a soil sample influences the availability of nutrients to the organism present in the soil (Soak Up the Rain: What's the Problem? | US EPA, 2023). The closer the pH of a soil is to 7 (a neutral pH) the more nutrients are available in the soil - allowing the soil to support a larger microbial population. The pH of a soil also affects what minerals are available in the soil for the plant - which affects what place can thrive in a given soil sample (Repp, 2019). We measured the pH of the soil from a control site and a rain garden site to determine if there is a significant difference in the pH of the two sites. This provided insight into whether rain gardens have different abilities to hold certain nutrients than non-rain gardens or not. 

Soil moisture is a measure of the dryness of a soil sample (Soil Moisture Guide, n.d.). Different types of soil have different moisture contents. Loam soil is dark brown soil that holds water well but is crumbly when touched. Sandy soil is lighter in color, gritty in texture, and water drains from it quickly. Clay soil slowly absorbs the most water, it tends to be heavier and to take longer to release nutrients. We tested the moisture content of both samples and determine if they are the same soil type. 

We used EcoPlate to measure the functional biodiversity of bacteria of each of the soil samples. We also measured genetic biodiversity of the soil samples through the use of genomic DNA 16S rRNA microbiome sequencing. Classifying the microorganisms present in the soil sample through DNA offered insights on the biodiversity of these sites in order to assess contamination and pollution in the samples. 16S rRNA sequencing was used to target a specific region of the genome of a bacterial organism that is highly variable in different species (Robertson, 2023). The functional biodiversity affects the carbon and nitrogen process within the soil - thus affecting the plant life - which could influence the ability of the soil to remove pollutants (Weng et al., 2021). The bacterial community present in a soil sample influences the material conversion and nutrient cycling in a sample. Soil biodiversity likely influences the carbon cycle in a region - which could influence the breakdown of carbon based pollutants.