Acid rain is precipitation with a lower pH than normal, caused primarily by sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions. These pollutants react with water vapor in the atmosphere to form sulfuric and nitric acids, which fall back to Earth as rain or snow.
Eutrophication: A process where water bodies become enriched with nutrients, leading to excessive growth of algae and depletion of oxygen.
Greenhouse Effect: The trapping of heat in Earth's atmosphere by greenhouse gases, leading to global warming.
Biogeochemical Cycles: Natural processes that recycle nutrients in various chemical forms from the environment to organisms and back again.