Environmental Chemistry Cheat Sheet

The core ideas of Environmental Chemistry distilled into a single, scannable reference — perfect for review or quick lookup.

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Quick Reference

Biogeochemical Cycles

The pathways by which chemical elements and compounds move through the biotic (living) and abiotic (non-living) compartments of Earth, including the carbon, nitrogen, phosphorus, and sulfur cycles. These cycles are driven by biological, geological, and chemical processes.

Persistent Organic Pollutants (POPs)

Organic compounds that resist environmental degradation through chemical, biological, and photolytic processes. They bioaccumulate in food chains, are transported across international boundaries by air and water, and pose serious health risks to humans and wildlife.

Acid Rain

Precipitation with a pH below 5.6, caused primarily by emissions of sulfur dioxide ($\text{SO}_2$) and nitrogen oxides ($\text{NO}_x$) from fossil fuel combustion. These gases react with water vapor in the atmosphere to form sulfuric acid and nitric acid.

Eutrophication

The excessive enrichment of a body of water with nutrients, particularly nitrogen and phosphorus, leading to dense algal blooms. When the algae die and decompose, dissolved oxygen is depleted, creating hypoxic or anoxic conditions that kill aquatic organisms.

Ozone Depletion

The thinning of the stratospheric ozone layer caused by catalytic destruction of ozone molecules ($\text{O}_3$) by halogenated compounds, primarily chlorofluorocarbons (CFCs). Each chlorine atom released from a CFC molecule can destroy tens of thousands of ozone molecules.

Greenhouse Effect and Climate Change

The process by which greenhouse gases ($\text{CO}_2$, $\text{CH}_4$, $\text{N}_2\text{O}$, water vapor, and fluorinated gases) in the atmosphere absorb and re-emit infrared radiation, warming Earth's surface. Human activities have intensified this natural effect, driving global climate change.

Heavy Metal Contamination

The introduction of toxic metallic elements such as lead, mercury, cadmium, arsenic, and chromium into the environment through mining, industrial discharge, and improper waste disposal. Heavy metals do not degrade and can bioaccumulate in organisms.

Water Treatment Chemistry

The chemical processes used to make water safe for drinking or to treat wastewater before discharge. Key processes include coagulation, flocculation, sedimentation, filtration, and disinfection using chlorine, ozone, or ultraviolet light.

Bioremediation

The use of living organisms, primarily microorganisms, to degrade or transform environmental contaminants into less toxic or non-toxic forms. This approach leverages natural metabolic pathways and can be enhanced through bioaugmentation or biostimulation.

Photochemical Smog

A type of air pollution formed when sunlight drives chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the atmosphere, producing ground-level ozone, peroxyacetyl nitrate (PAN), and other secondary pollutants.

Key Terms at a Glance

Acid Deposition:The process by which acidic substances (wet or dry) are deposited from the atmosphere onto Earth's surface, including acid rain, fog, and dry particulate fallout.

Adsorption:The adhesion of molecules to a solid surface, distinct from absorption. Important in contaminant binding to soil particles and activated carbon filtration.

Bioaccumulation:The gradual accumulation of a substance in an organism when the rate of intake exceeds the rate of metabolism and excretion.

Biogeochemical Cycle:The pathway by which a chemical element or molecule moves through the atmosphere, hydrosphere, lithosphere, and biosphere.

Biomagnification:The increase in concentration of a persistent substance at successively higher trophic levels in a food chain.

Bioremediation:The use of biological organisms to remove or neutralize environmental contaminants from polluted sites.

BOD (Biochemical Oxygen Demand):The quantity of dissolved oxygen required by aerobic microorganisms to decompose organic matter in a water sample, used as a measure of water pollution.

Carbon Sequestration:The long-term capture and storage of atmospheric carbon dioxide in geological formations, oceans, soils, or biomass.

COD (Chemical Oxygen Demand):A measure of the total quantity of oxygen required for chemical oxidation of organic and inorganic matter in water.

Dissolved Oxygen (DO):The concentration of molecular oxygen dissolved in water, essential for supporting aquatic life.

Eutrophication:The enrichment of a water body with excess nutrients, leading to algal blooms, oxygen depletion, and ecological degradation.

Global Warming Potential (GWP):A measure of how much energy a mass of greenhouse gas absorbs over a given time period relative to the same mass of $\text{CO}_2$.

Half-Life:The time required for the concentration or amount of a substance to decrease to half its initial value through degradation or decay.

Heavy Metals:Metallic elements with high density and potential toxicity, including mercury, lead, cadmium, arsenic, and chromium.

Leaching:The downward transport of dissolved substances through soil by percolating water, potentially contaminating groundwater.

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