Environmental Pollution and Waste Management Practice Test

Eutrophication in freshwater systems is driven by excess nutrients that fuel rapid growth of algae and aquatic plants. The key nutrients fueling this process are nitrogen and phosphorus, which are essential building blocks for biological molecules and are often available in amounts that exceed what the ecosystem can handle. When inputs from sources like agricultural runoff, wastewater, and detergents raise nitrogen and phosphorus levels, algae bloom intensely. As these blooms die and decompose, microorganisms consume a lot of dissolved oxygen, leading to hypoxic conditions that can harm or kill other aquatic life. In many freshwater environments, phosphorus is the limiting nutrient, so reducing its inputs often yields the biggest improvement, while nitrogen can also contribute to blooms, especially where phosphorus is already abundant. The other nutrient pairs listed do not drive eutrophication in the same way: calcium and magnesium affect water hardness rather than algal growth; sodium and potassium are important ions but not the primary growth-limiting nutrients in this context; chlorides and fluorides are trace constituents and not the main culprits of nutrient-driven algal blooms.