What can happen if landfills are not properly constructed?

Landfills that are not properly constructed can lead to significant environmental issues, particularly the pollution of aquatic resources. When a landfill is poorly designed or maintained, the potential for leachate—a toxic liquid formed when water filters through waste materials—increases. This leachate can contaminate groundwater and surface water, leading to severe ecological damage and posing health risks to local communities. Moreover, the presence of harmful chemicals and pathogens in the leachate can affect aquatic ecosystems, resulting in the degradation of water quality and harm to aquatic life.

In contrast, reduced waste volume, increased recycling opportunities, and improved treatment efficiency are not direct outcomes of landfill construction quality. Instead, these concepts are more related to comprehensive waste management practices rather than the structural integrity of a landfill. Thus, the correct answer highlights the critical environmental risks associated with improperly constructed landfills.