Chemical Safety, Atmospheric Chemistry, and Soil Chemistry Lecture Notes

Flashcards covering chemical safety principles, laboratory case studies, atmospheric composition and formation, water chemistry and pollution, and soil chemistry and decontamination techniques.

Petroleum ether (PE)

A chemical that caused an explosion in a domestic freezer after evaporating to a concentration exceeding the lower explosive limit of about $1.0\%$.

Flash point

The temperature at which a liquid transitions to a gas; for petroleum ether, this value is $-50℃$.

Anaerobic hood

An oxygen-free chamber used for working with bacteria that cannot survive in the presence of oxygen.

Hazard Communication

A system that allows workers to know the hazards and identities of the chemicals they are exposed to through labels, Material Safety Data Sheets, and training.

Material Safety Data Sheet (MSDS)

A document prepared by chemical manufacturers describing physical/health hazards, properties, routes of exposure, and emergency procedures.

Globally Harmonized System (GHS)

An international non-binding system for classifying chemical hazards and standardizing the format of labels and safety data sheets (SDS).

Toxicity

The inherent ability of a chemical to cause harm, often referred to as a hazard in general safety terms.

Risk

The likelihood of a material to cause harm under specific conditions of use.

Inhalation

A route of chemical exposure occurring through breathing in powders or fumes.

Ingestion

A route of chemical exposure occurring through entry via the mouth.

Injection

A route of chemical exposure through the skin caused by a foreign body.

Absorption

A route of chemical exposure through the skin or mucus membranes.

Acute exposure

Short-term chemical exposure resulting in immediate effects like eye irritation, nausea, or dizziness.

Chronic exposure

Long-term chemical exposure that may result in long-term illnesses.

Hierarchy of Risk Controls

Order of priority for safety measures: 1. Eliminate, 2. Substitute, 3. Engineering, 4. Awareness, 5. Administrative, 6. PPE.

Engineering controls

Safety measures such as fume hoods, engineered sharps, and eye wash stations designed to remove hazards.

Administrative controls

Safety measures involving training, procedures, instructions, and scheduling.

Personal protective equipment (PPE)

Items worn to minimize exposure to hazards, including gloves, lab coats, respirators, and face shields.

Sheharbano “Sheri” Sangji Case

The first criminal case resulting from an academic lab accident (UCLA, 2008), where a researcher died from a flash fire while working with t-butyl lithium.

Karen Wetterhahn Case

A case involving a Dartmouth professor who died from dimethylmercury exposure after a few drops permeated her latex gloves within $15$ seconds.

Dimethylmercury (DMM)

An extremely toxic metal compound that can raise blood mercury levels to $80$ times the toxic threshold from a single exposure.

Chemical Segregation

The use of physical barriers and/or distance to prevent incompatible materials from coming into contact during storage.

White storage code

A color-coded indicator used in chemical storage to signify compatible materials.

Red storage code

A color-coded indicator used in chemical storage to signify incompatible materials.

Major Spill (Response)

A spill requiring evacuation, avoidance of chemicals, finding the MSDS, and telephoning for help.

Minor Spill (Response)

A spill where one should remove contaminated clothing, use PPE, contain the spill, notify others, and seek advice from an MSDS.

Mercury disposal

A specific waste management procedure required for items like broken thermometers.

Primitive Atmosphere

The atmosphere $4.5$ million years ago, composed of Hydrogen, Helium, Ammonia, and Methane.

Secondary Atmosphere

An atmosphere formed by volcanic activity releasing water vapor, carbon dioxide, and ammonia, similar to Mars and Venus today.

Nitrogen (formation)

Atmospheric gas formed from the breakdown of ammonia due to sunlight.

Oxidizing Atmosphere

The current atmospheric state where oxygen was produced via water vapor dissociation, photosynthesis, and metal oxidation.

Ozone ($O_3$)

A gas formed when oxygen molecules absorb UV radiation, making life on Earth possible.

Atmosphere

A thick mixture of gases surrounding Earth, held near the surface by gravity, serving as a protective shield.

Karman Line

An imaginary line identifying the boundary between the Earth's atmosphere and outer space.

Residence Time

The average amount of time a gas spends in the atmosphere, calculated by dividing the total amount by the removal rate.

Nitrogen ($N_2$)

An inert gas fundamental to living systems, removed through nitrogen fixation and returned via biomass combustion.

Nitrogen Fixation

The process where atmospheric $N_2$ is reduced to form ammonia by soil bacteria or lightning.

Denitrification

The reduction of nitrates to gaseous nitrogen by microorganisms in a series of biochemical reactions.

Oxygen ($O_2$)

Atmospheric gas exchanged between the atmosphere and biosphere through photosynthesis and respiration.

Argon ($Ar$)

The third most abundant gas in the atmosphere, primarily derived from the radiogenic decay of potassium-40 ($^{40}K$).

Water Vapor (Concentration)

Concentrated in the lower atmosphere, with $99\%$ of it found in the troposphere.

Saturation Level (Humidity)

The capacity of air to hold water vapor, which is dependent solely on air temperature.

Energy/Heat Budget

The net flow of energy into Earth, mainly as shortwave radiation and infrared longwave radiation.

Carbon Dioxide ($CO_2$)

An important greenhouse gas with high absorption capacity for infrared radiation, exchanged through photosynthesis and respiration.

Water bonding

Two hydrogen atoms and one oxygen atom held together by strong covalent bonds.

Water structure bond angle (Liquid)

The bond angle between hydrogen atoms in liquid water is $105°$.

Water structure bond angle (Ice)

The bond angle between hydrogen atoms in ice is $109°6′$.

Water Isotopes

There are $3$ hydrogen isotopes and $3$ oxygen isotopes, allowing for $18$ possible water molecules.

Hydrogen Bond

A weak attraction between polar molecules where the hydrogen of one molecule is attracted to an electronegative atom of another.

Coordination Number

The average number of nearest neighboring atoms surrounding a central atom; liquid water's is higher than ice's.

Specific Heat (Water)

The energy required to raise temperature, defined as $1\,cal/g/°C$ for water.

Latent Heat of Fusion

The energy required to convert $1\,g$ of ice into water at $0°C$, which is $80$ calories.

Latent Heat of Vaporization

The energy required to convert $1\,g$ of water into steam at $100°C$, which is $540$ calories.

Cohesion

A property of water involving the attraction between similar water molecules.

Capillary action

The ability of water to flow in narrow spaces without the assistance of external forces.

Point Sources

Direct discharges of pollutants into water, such as domestic or industrial waste.

Non-Point Sources

Indirect pollution through environmental changes, such as farm, mine, or construction site runoff.

Water Pollutants

Substances that cause physical, chemical, or biological changes in water.

Siltation

A natural source of pollution caused by deforestation where loose soil is washed into rivers during rainfall.

Anthropogenic Sources

Human-caused pollution sources including sewage, wastewater, and agricultural waste.

Pathogens

Water pollutants from sewage and animal waste that cause foul odors and water-borne disease outbreaks.

Organic Pollutants

Substances like oil, pesticides, plastics, and detergents that disrupt marine life and cause toxicity.

Inorganic Pollutants

Fertilizers (phosphates/nitrates) and acids that cause algal blooms and eutrophication.

Methemoglobinemia

A health condition caused by high nitrate levels in drinking water.

Radioactive Materials

Pollutants from uranium mining, hospitals, and labs that cause cancer and genetic defects.

Thermal Stratification

The formation of non-mixing layers in water bodies due to temperature differences.

Epilimnion

The surface layer of a water body characterized by higher temperature and lower density.

Thermocline

The middle layer of a water body with heavy algae growth and high levels of dissolved oxygen.

Hypolimnion

The lowest, anaerobic layer of a water body where oxygen is consumed by biodegradable organic material.

Thermal Pollution

Occurs when water entering a body is warmer than existing water, often from nuclear power plant cooling water.

Dissolved Oxygen (DO)

Needed by aquatic organisms for respiration; low levels are the cause of most fish kills.

Alkalinity

A measure of water's capacity to neutralize acids and its buffer capacity, mainly due to salts of weak acids.

Acidity

Commonly caused by dissolved carbon dioxide in water, which makes the water corrosive.

Hardness

A condition in water caused by divalent metallic cations, primarily calcium and magnesium.

Soil

A heterogeneous mixture of air, water, inorganic/organic solids, and microorganisms.

Soil Chemistry

The study of the chemical composition, properties, and reactions of soil.

Environmental Soil Chemistry

The study of reactions between soils and nutrients, radionuclides, metals, and organic chemicals.

Peds

Aggregates of sand, silt, and clay particles that form larger soil structures.

Profiles (Soil)

Layers of varying texture, structure, color, and bulk density developed in loose surface material.

Pedon

The smallest unit that can be considered 'soil,' extending from the surface to geologic strata.

Polypedon

An area consisting of similar pedons.

Oxygen (Earth's crust)

The most prevalent element in soils, making up $47\%$ of the Earth's crust by weight and $90\%$ by volume.

Mineral

A natural inorganic compound with definite physical, chemical, and crystalline properties.

Primary Mineral

A mineral not chemically altered since deposition from molten lava, such as Quartz, Feldspar, or Micas.

Secondary Mineral

A mineral resulting from the weathering of a primary mineral, such as Kaolinite, Gibbsite, or Goethite.

Soil Organic Matter (SOM)

Also called humus, this includes total organic compounds in soils excluding undecayed tissues.

Organic residues

Undecayed plant and animal tissues and their partially decomposed products.

Soil biomass

Organic matter present in the soil as live microbial tissue.

Humic substances

High-molecular-weight, dark-colored substances formed by secondary synthesis reactions.

Nonhumic substances

Soil compounds belonging to known biochemical classes like amino acids, fats, and carbohydrates.

Humin

The alkali-insoluble fraction of soil organic matter.

Humic acid

Dark-colored organic material extracted from soil that is insoluble in dilute acid.

Fulvic acid

The colored organic material that remains in solution after acidification during extraction.

Hymatomelanic acid

The portion of humic acid that is soluble in alcohol.

Volatilization (Soil)

An in situ decontamination method using air venting to remove volatile organic compounds resistant to biodegradation.

Biodegradation (Soil)

An in situ technique that enhances naturally occurring microorganisms to degrade soil contaminants.

Phytoremediation

The use of plants like sunflowers (for uranium) or ferns (for arsenic) to decontaminate soil and water.

Leaching (Soil)

A technique where soil is washed with water and a surfactant, though it produces large amounts of wastewater.

Vitrification

The solidification of soil contaminants using an electric current, immobilizing them for up to $10,000$ years.

Land Treatment

A non-in situ technique where contaminated soil is excavated and spread over land to allow natural biodegradation.