Environmental Chemistry: Atmospheric Systems, Chemical Safety, Water Resources, and Solar Radiation

Comprehensive practice flashcards covering air quality, toxicology, environmental safety, atmospheric chemistry, aquatic resources, and solar radiation chemistry.

Cellular Respiration

The biological process in which oxygen ($O_2$) is used to extract energy from ingested food, producing carbon dioxide ($CO_2$) and water ($H_2O$) as products.

Air Inversion

An atmospheric condition in the troposphere where cooler air is trapped beneath a layer of warmer air or pollution, inhibiting the upward dispersion of pollutants.

Catalytic Converter

A motor vehicle emission-control device that catalyzes the conversion of carbon monoxide ($CO$) to carbon dioxide ($CO_2$) and reduces nitrogen oxides to nitrogen ($N_2$) and oxygen ($O_2$) gases.

Secondary Pollutant

A harmful substance that is not emitted directly into the air, but forms in the atmosphere via chemical reactions between primary pollutants (for example, tropospheric ozone, $O_3$, formed from $NO_2$ and VOCs in sunlight).

Green Chemistry

A design philosophy that aims to minimize environmental impact and pollution by reducing energy usage, eliminating hazardous waste, and replacing petroleum-derived reagents with renewable feedstocks.

Hazard

The inherent potential of a chemical substance, condition, or situation to cause harm or damage to biological systems or the environment.

Risk

A mathematical measure of the probability that harm will occur under specific defined conditions of exposure to a chemical hazard.

Carcinogen

A chemical agent, type of ionizing/UV radiation, or virus capable of causing or promoting cancer in living tissues.

Mutagen

A physical or chemical agent that alters the genetic material (DNA) of an organism or significantly increases the frequency of genetic mutations.

Teratogen

A chemical agent that causes structural malformations, damage, or birth defects to a developing embryo or fetus.

Neurotoxin

A toxic substance that specifically damages or impairs the functioning of the central or peripheral nervous system, causing neurological effects such as behavioral changes, learning deficits, or paralysis.

Hormonally Active Agent (HAA)

A synthetic chemical (such as bisphenol A, DDT, or phthalates) that disrupts the endocrine system by mimicking, blocking, or altering the behavior of endogenous hormones.

Median Lethal Dose ($LD_{50}$)

The calculated dose of a substance that kills $50\%$ of an animal test population within an 18-day period, typically reported in milligrams of substance per kilogram of body weight ($\text{mg/kg}$).

Multiple Chemical Sensitivity (MCS)

A medical condition characterized by heightened physiological sensitivity and adverse reactions to very low levels of multiple, unrelated environmental chemicals.

Biological Magnification

The progressive increase in concentration of persistent, fat-soluble toxins (such as DDT or PCBs) within organisms at successively higher trophic levels of a food web.

Precautionary Principle

The policy principle holding that when an activity or chemical poses plausible, irreversible threats to human health or the environment, preventive action should be taken despite lack of full scientific certainty.

Organophosphates

Synthetic phosphorus-containing chemicals widely utilized in insecticides, herbicides, and nerve agents that induce toxicity primarily by inhibiting neurotransmitter breakdown.

Pesticide Treadmill

A cycle where heavy pesticide use generates herbicide- or insect-resistant super-pests, forcing farmers to purchase newer, stronger, and more toxic chemical formulations.

NFPA 704 Hazard Identification Diamond

A standard hazard identification symbol utilized on Safety Data Sheets (SDS) and containers displaying ratings from 0 to 4 for health (blue), fire (red), reactivity (yellow), and specific hazards (white).

Corrosive Substance

A highly reactive acid or base that causes irreversible chemical destruction and necrosis of living biological tissues upon contact.

Nitrogen Fixation

The chemical conversion of relatively inert atmospheric dinitrogen gas ($N_2$) into bioavailable nitrogenous compounds such as ammonia ($NH_3$) and nitrates ($NO_3^-$).

Denitrification

The biological process in the nitrogen cycle through which nitrates ($NO_3^-$) are reduced sequentially to nitrites ($NO_2^-$), nitric oxide ($NO$), nitrous oxide ($N_2O$), and finally dinitrogen gas ($N_2$).

Juvenile Nitrogen

Nitrogen released directly from deep geological processes (such as volcanism) that has never previously circulated through the biological nitrogen cycle.

Stone Leprosy

The progressive erosion and chemical decay of limestone and marble ($CaCO_3$) structures triggered by dry and wet deposition of acidic sulfur dioxide and sulfuric acid: $CaCO_3(s) + H_2SO_4(aq) \rightarrow CaSO_4(s) + H_2O(l) + CO_2(g)$.

Photochemical Smog

A complex haze of secondary air pollutants, including nitrogen dioxide ($NO_2$) and ozone ($O_3$), produced when primary pollutants from vehicular exhaust ($NO$, $CO$, hydrocarbons) react under sunlight.

Radon-222 ($^{222}_{86}Rn$)

A radioactive, colorless, and odorless noble gas with a half-life of $3.82\,\text{days}$ produced from the natural radioactive decay of Radium-226 and Uranium-238, capable of accumulating in indoor spaces and basements.

Hydrogen Bond

A strong dipole-dipole intermolecular electrostatic attraction occurring between a hydrogen atom covalently bonded to a highly electronegative atom ($N$, $O$, or $F$) and a nearby electronegative atom possessing a lone pair.

Bond Dipole

The charge separation occurring across a covalent bond when electron density is unequally shared between two atoms of differing electronegativities, producing partial negative ($\delta^-$) and partial positive ($\delta^+$) ends.

Molarity ($M$)

A standard unit of solution concentration calculated as the number of moles of dissolved solute per liter of solution: $M = \frac{\text{moles of solute}}{\text{liters of solution}}$.

Electrolyte

A solute that dissociates into free ions upon dissolving in water, producing an aqueous solution capable of conducting electric current.

Surfactant

An amphiphilic chemical compound composed of a polar hydrophilic head and a nonpolar hydrophobic tail that lowers the surface tension between immiscible liquids.

Neutralization Reaction

An acid-base reaction in which hydronium ($H^+$) and hydroxide ($OH^-$) ions combine to form water and a dissolved ionic salt: $H^+(aq) + OH^-(aq) \rightarrow H_2O(l)$.

Ocean Acidification

The gradual reduction in ocean pH resulting from the sustained uptake and dissolution of anthropogenic carbon dioxide ($CO_2$) from the atmosphere, creating carbonic acid that dissolves marine calcium carbonate shells.

Reverse Osmosis

A membrane-based desalination method that employs high pressure to force salt water across a semipermeable membrane against natural osmotic pressure, separating purified water from concentrated brine.

UVC Radiation

The most energetic band of ultraviolet light, spanning $200\text{--}280\,\text{nm}$, capable of severing $O=O$ double bonds ($\lambda \le 242\,\text{nm}$) and completely absorbed by oxygen and ozone in the upper atmosphere.

UVB Radiation

Ultraviolet radiation with wavelengths between $280\text{--}320\,\text{nm}$ that is mostly absorbed by stratospheric ozone, with residual photons penetrating the epidermis and inducing sunburn and direct DNA lesions.

UVA Radiation

The lowest-energy ultraviolet band ($320\text{--}400\,\text{nm}$) that passes unhindered through the stratosphere, penetrating past the epidermis into the deeper dermal and subcutaneous skin layers.

Octet Rule

The chemical bonding principle stating that representative atoms tend to gain, lose, or share electrons until their valence shells are surrounded by eight electrons.

Chapman Cycle

The natural continuous set of four photochemical reactions in the stratosphere that balances ozone formation ($O_2 + h\nu \rightarrow 2O$ and $O + O_2 \rightarrow O_3$) and breakdown ($O_3 + h\nu \rightarrow O_2 + O$ and $O_3 + O \rightarrow 2O_2$).

Montreal Protocol

The 1987 landmark international environmental agreement dedicated to safeguarding the stratospheric ozone layer by freezing and phasing out the worldwide manufacture of chlorofluorocarbons (CFCs).

Sun Protection Factor (SPF)

A relative metric defining how much longer skin protected with sunscreen can resist UVB erythema (reddening) compared to completely unprotected skin.