Read the notes, then try the practice. It adapts as you go.When you're ready.
Session Length
~17 min
Adaptive Checks
15 questions
Transfer Probes
8
Environmental chemistry is the scientific study of chemical and biochemical phenomena that occur in the natural environment. It encompasses the sources, reactions, transport, effects, and fates of chemical species in water, soil, air, and living organisms, as well as the influence of human activities on these processes. The discipline draws on principles from analytical chemistry, organic chemistry, physical chemistry, and biochemistry to understand how natural and anthropogenic chemicals interact within ecosystems.
The field emerged as a distinct discipline in the 1960s and 1970s, spurred by growing awareness of pollution and environmental degradation. Landmark events such as the publication of Rachel Carson's 'Silent Spring' in 1962, the discovery of the ozone hole, and the identification of acid rain as a transboundary problem catalyzed both public concern and scientific investigation. Researchers like F. Sherwood Rowland, Mario Molina, and Paul Crutzen earned the Nobel Prize in Chemistry in 1995 for their work on stratospheric ozone depletion, demonstrating the profound impact environmental chemistry has on global policy.
Today, environmental chemistry is central to addressing the most pressing challenges facing humanity, including climate change, water contamination, microplastic pollution, and persistent organic pollutants. Environmental chemists develop analytical methods to detect trace contaminants, model the transport and transformation of pollutants, design remediation strategies for contaminated sites, and assess the environmental fate of new chemicals before they enter commerce. The field informs environmental regulations, sustainable industrial practices, and public health protections worldwide.
One step at a time.
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.
Example: The nitrogen cycle involves nitrogen fixation by bacteria, nitrification, assimilation by plants, and denitrification, returning molecular nitrogen to the atmosphere.
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.
Example: DDT, once widely used as a pesticide, persists in soils for decades and biomagnifies through food chains, causing eggshell thinning in birds of prey like bald eagles.
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.
Example: Acid rain damaged forests across Scandinavia and northeastern North America in the 1970s-1980s, and acidified lakes to the point where fish populations collapsed.
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.
Example: Agricultural runoff carrying fertilizers into the Gulf of Mexico has created a seasonal hypoxic 'dead zone' spanning thousands of square kilometers.
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.
Example: The Montreal Protocol of 1987 phased out CFCs and other ozone-depleting substances, and the Antarctic ozone hole has shown measurable signs of recovery since the early 2000s.
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.
Example: Atmospheric CO2 concentrations have risen from approximately 280 ppm in pre-industrial times to over 420 ppm today, correlating with a global average temperature increase of about 1.2 degrees Celsius.
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.
Example: Mercury released from coal-fired power plants deposits into waterways, where microorganisms convert it to methylmercury, which biomagnifies through aquatic food chains and poses neurotoxic risks to humans consuming contaminated fish.
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.
Example: Municipal water treatment plants add aluminum sulfate as a coagulant to aggregate suspended particles into flocs that can be removed by sedimentation and filtration.
More terms are available in the glossary.
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Walk through a solved problem step-by-step. Try predicting each step before revealing it.
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