What are liners commonly made of to prevent contamination from landfills?

Liners in landfills are specifically designed to prevent the leachate—the liquid that results from the decomposition of waste—from contaminating surrounding soil and groundwater. The materials commonly used to construct these liners are clay, synthetic materials, or PVC.

Clay is naturally occurring and has low permeability, which allows it to effectively restrict the flow of leachate. Synthetic materials, such as high-density polyethylene (HDPE), provide a durable and reliable barrier that can withstand environmental stressors. Similarly, PVC is a well-regarded liner material due to its versatility, resistance to chemicals, and strong physical properties.

While the other options include materials that may have applications in construction or other contexts, they do not possess the specific qualities required for landfill liners. For instance, metals and glass do not offer the impermeability needed to prevent leachate infiltration, while wood and rubber are not suitable due to their potential for degradation and reduced effectiveness over time in harsh landfill environments. Thus, the answer highlighting clay, synthetic materials, or PVC reflects the best practice for material selection in landfill liner construction.