Carbon dioxide (CO₂) is the primary greenhouse gas responsible for global warming. It is released into the atmosphere through human activities such as burning fossil fuels, deforestation, and industrial processes.

Acid rain is primarily caused by the burning of fossil fuels, which releases sulfur dioxide (SO₂) and nitrogen oxides (NO_x) into the atmosphere. These gases react with water vapor to form sulfuric acid (H₂SO₄) and nitric acid (HNO₃), which contribute to acid rain.

Industrial wastewater, agricultural runoff, and municipal sewage are all major sources of water pollution. Industrial wastewater can contain toxic chemicals, heavy metals, and other pollutants. Agricultural runoff can carry fertilizers, pesticides, and animal waste into waterways. Municipal sewage contains human waste and other organic matter, which can contribute to eutrophication and other water quality problems.

Bioremediation, phytoremediation, and chemical remediation are all processes by which pollutants are removed from the environment. Bioremediation involves the use of microorganisms to break down and remove pollutants. Phytoremediation involves the use of plants to absorb and remove pollutants from the soil or water. Chemical remediation involves the use of chemical reactions to break down and remove pollutants.

Particulate matter (PM), ground-level ozone (O₃), and nitrogen dioxide (NO₂) are all major air pollutants. PM refers to small particles of solid or liquid matter suspended in the air, such as dust, smoke, and soot. Ground-level ozone is a gas that is formed when sunlight reacts with other pollutants in the air. Nitrogen dioxide is a gas that is released into the air from burning fossil fuels.

Soil contamination, soil pollution, and soil degradation all refer to the process by which soil becomes contaminated with pollutants. Soil contamination can occur through a variety of sources, including industrial activities, agricultural practices, and improper waste disposal.

Heavy metals, pesticides, and petroleum hydrocarbons are all common soil contaminants. Heavy metals can accumulate in the soil over time and pose a risk to human health and the environment. Pesticides can be harmful to beneficial soil organisms and can also contaminate groundwater. Petroleum hydrocarbons can contaminate soil and groundwater and can also pose a fire hazard.

Environmental transport, environmental fate, and environmental distribution all refer to the process by which pollutants are transported through the environment. Pollutants can be transported through the air, water, or soil. The fate of a pollutant depends on its chemical properties, the environmental conditions, and the presence of other pollutants.

Pesticide resistance, groundwater contamination, and harm to beneficial insects are all major environmental risks associated with the use of pesticides. Pesticide resistance can develop when pests evolve to become resistant to the effects of pesticides. Groundwater contamination can occur when pesticides leach into groundwater supplies. Harm to beneficial insects can occur when pesticides kill beneficial insects, such as bees and ladybugs, which can disrupt ecosystems.

Degradation, mineralization, and transformation all refer to the process by which pollutants are transformed into less harmful or non-toxic substances. Degradation involves the breakdown of pollutants into smaller molecules. Mineralization involves the conversion of organic pollutants into inorganic compounds. Transformation involves the conversion of pollutants into different chemical forms.

Eutrophication, groundwater contamination, and air pollution are all major environmental risks associated with the use of fertilizers. Eutrophication can occur when excess nutrients from fertilizers enter waterways and cause algal blooms. Groundwater contamination can occur when fertilizers leach into groundwater supplies. Air pollution can occur when nitrogen fertilizers are converted into nitrous oxide, a greenhouse gas.

Natural attenuation, biodegradation, and phytoremediation all refer to the process by which pollutants are removed from the environment by natural processes. Natural attenuation involves the breakdown of pollutants by natural chemical and biological processes. Biodegradation involves the breakdown of pollutants by microorganisms. Phytoremediation involves the removal of pollutants from the environment by plants.

Plastic pollution, marine debris, and microplastics are all major environmental risks associated with the use of plastics. Plastic pollution refers to the accumulation of plastic waste in the environment. Marine debris refers to plastic waste that ends up in the ocean. Microplastics are small pieces of plastic that can be harmful to marine life and human health.

Emission, discharge, and release all refer to the process by which pollutants are released into the environment. Pollutants can be emitted into the air, discharged into water, or released onto land.

Climate change, air pollution, and water pollution are all major environmental risks associated with the use of fossil fuels. Climate change is caused by the release of greenhouse gases, such as carbon dioxide, into the atmosphere. Air pollution is caused by the release of pollutants, such as particulate matter and nitrogen oxides, into the air. Water pollution is caused by the release of pollutants, such as oil and heavy metals, into water bodies.