Environmental Quality, Soil Remediation, and Sustainable Agriculture
Core concepts
Understand soil and water pollution sources-agricultural chemicals, excess nutrients, heavy metals, and organic contaminants-and the fate processes of adsorption, leaching, volatilization, degradation, and bioaccumulation. Know remediation approaches: physical (excavation, soil washing), chemical (stabilization, oxidation), and biological (phytoremediation, bioremediation, composting). Grasp sustainable agriculture principles: maintaining soil organic matter, reducing erosion, nutrient cycling, biodiversity, and integrated nutrient management. Understand eutrophication, greenhouse gas emissions from agriculture, and carbon sequestration in soils. Know the concepts of soil health indicators (physical, chemical, biological) and best management practices.
Traps in questions
Do not confuse phytoremediation (plants extract or stabilize contaminants) with bioremediation (microorganisms degrade contaminants). Remember that excess nitrogen and phosphorus cause eutrophication, with phosphorus often limiting in freshwater and nitrogen in marine systems. Watch for questions treating organic farming as automatically free of environmental impact-nutrient management still matters. Distinguish point-source from nonpoint-source pollution.
Worked example
A field receives 200 kg N/ha but the crop removes only 150 kg N/ha. The surplus 50 kg N/ha is at risk of leaching or denitrification. Rule of thumb: nutrient balance = inputs minus crop removal and losses; a positive balance signals potential environmental loss.
Rule of thumb
Reduce, retain, and remediate: reduce inputs at the source, retain nutrients on-site with cover crops and buffers, and remediate contaminated soils with the method matched to the contaminant.