Soru

An excerpt from an academic oral presentation delivered at an environmental engineering symposium states:

"During our three-year watershed study at Lake Atitlán, Guatemala, our team investigated three distinct ecological intervention zones to mitigate severe water degradation. In Sector A, along the northern municipal shorelines, high concentrations of urban phosphates triggered recurring cyanobacterial blooms, which we addressed by deploying twenty thousand square meters of native tule reed (*Schoenoplectus californicus*) floating bio-islands to absorb excess dissolved nitrogen and phosphorus. In Sector B, across the steep southern agricultural basin, severe soil erosion deposited approximately two hundred thousand metric tons of topsoil into the lake each year; here, we engineered vegetative contour terraces stabilized with vetiver grass and stone retaining bunds. Finally, in Sector C, along the western tributary where artisanal coffee processing mills operate, untreated pulping effluent with a biochemical oxygen demand exceeding three thousand milligrams per liter was captured using decentralized anaerobic biodigesters coupled with biochar filtration cells."

Based on the oral presentation transcript, match each intervention sector with the specific environmental problem, supporting metric, and engineering solution described by the speaker.