Oil is damaging to turfgrass and surrounding soil, causing turf death and environmental issues even from a small spill. Damage occurs through physical suffocation and chemical toxicity, immediately disrupting the plant’s life processes. Understanding the mechanism of harm and the difference between oil types is the first step in effectively treating the affected area and detailing the measures required for successful soil remediation.
How Oil Kills Plant Life
Oil kills grass by attacking the plant both above and below the soil surface. When oil coats the grass blades, it physically blocks the tiny pores called stomata, which are responsible for gas exchange. This smothering prevents the absorption of carbon dioxide, halting photosynthesis and the plant’s ability to produce energy.
The hydrophobic nature of oil prevents moisture uptake and disrupts the soil’s structure. As the oil seeps into the ground, it coats the soil particles, displacing the air pockets necessary for root respiration. This leads to root suffocation, where the roots can no longer absorb oxygen or water in the oil-saturated medium.
Furthermore, hydrocarbon molecules within the oil penetrate the plant’s tissue and damage cell membranes. This cellular breakdown causes contents to leak and inhibits the transport of nutrients and water. This internal toxicity, combined with physical barriers to gas and water exchange, results in rapid yellowing and death of the turfgrass shortly after the spill.
The Difference Between Petroleum and Cooking Oils
The severity of the damage depends on the chemical composition of the spilled substance. Petroleum-based oils, such as motor oil, gasoline, or diesel, are complex mixtures of hydrocarbons containing toxic components. These products often include volatile organic compounds (VOCs) and heavy metals that are poisonous to plant cells and soil microorganisms. Petroleum is persistent in the environment, requiring a long time for naturally occurring microbes to break down the complex molecules.
In contrast, cooking oils, like canola or olive oil, are plant-derived triglycerides and are less chemically toxic. While they still cause immediate physical damage through smothering and creating a hydrophobic barrier, they lack the aromatic compounds that make petroleum dangerous. Cooking oils are biodegradable, meaning soil bacteria can break them down much more readily than petroleum.
The primary risk from cooking oil is the initial physical coating and suffocation of the grass and roots. Once the physical oil is removed, the remaining organic residue degrades faster, posing a lower risk of long-term soil contamination. Petroleum spills introduce persistent, toxic chemicals that require a more aggressive and long-term remediation strategy to restore the soil.
Practical Steps for Soil Remediation
The immediate action for any oil spill is to stop the source of the leak and contain the spill to prevent further spread. For small, surface-level spills, the initial step is using an absorbent material to soak up the liquid oil. Materials like cat litter, sawdust, or specialized granular absorbents should be applied generously and allowed to sit for several hours. The saturated material must then be collected and disposed of according to local environmental regulations, as it is considered hazardous waste.
After removing the bulk of the oil, the area can be treated with a household dish soap solution, which acts as a surfactant to break down remaining oil molecules. A solution of water mixed with a few tablespoons of grease-cutting detergent should be gently scrubbed into the area. The area should then be flushed lightly with water, ensuring no runoff enters storm drains. This emulsification step helps lift residual oil from the soil and grass blades.
For large or saturated spills where the oil has penetrated several inches into the soil, physical removal is the most effective solution. The contaminated topsoil, typically 2 to 4 inches deep or until the soil no longer smells strongly of oil, must be excavated and replaced with clean topsoil. The removed soil requires proper disposal at an approved facility due to its contamination.
Final remediation involves encouraging microbial activity to break down any residual contaminants left in the soil. This process, known as bioremediation, can be accelerated by keeping the area moist and aerated. Applying a specialized nitrogen fertilizer or commercial microbial product can boost the population of oil-eating bacteria, speeding up the natural cleansing process before reseeding.