Environmental Science Terms: Waste, Ozone, Carbon and Nitrogen Cycles

Key Environmental Science Terms

Waste (Residuo)

Residual product resulting from the manufacture, consumption and use of products that has no economic value. Proper handling is essential.

Incineration (Incineración)

A waste elimination method consisting of the controlled combustion of solid waste at high temperatures, producing ash and gases such as _CO2, _H2O, and SO₂. Burning plastic can release toxic dioxins.

Hazard (Peligrosidad)

The probability of occurrence of a potentially harmful phenomenon within a given time and space.

Exposure

The total number of people or living beings affected by a determined risk (RISG) within a population.

Ozone

A pale blue gas that is irritant and pungent. It is essential in the stratosphere but is a harmful contaminant in the troposphere, where it cannot be breathed safely.

Soil (Suelo)

A natural body formed by the action of climate, organisms and natural ecosystem factors. It is a non-renewable natural resource.

Trophic Chain (Cadena trófica)

The linear nutritional relationship between organisms, such as producers, primary consumers, secondary consumers, and so on.

Compost

A product obtained through the controlled decomposition of organic matter from diverse origins, used as a fertilizer.

Ozone Layer (Capa de ozono)

A layer of the atmosphere located 15 to 20 kilometers high, naturally rich in ozone molecules that absorb most of the potentially harmful ultraviolet radiation reaching the biosphere.

Biogeochemical Cycles

Carbon

Carbon is found as CO₂ in the atmosphere and as bicarbonate in the hydrosphere. Plants capture CO₂ and transform it into organic matter through photosynthesis. Consumers obtain carbon by eating plants, and it is incorporated into their bodies. When organisms die, decomposers break down their remains, releasing CO₂ back into the atmosphere. Volcanoes, forest fires and coal combustion also add CO₂ to the atmosphere.

Nitrogen (Nitrógeno)

Gaseous nitrogen cannot be used directly by most plants. Bacteria oxidize and transform it into nitrites and nitrates, which plants can absorb. Some leguminous plants host symbiotic bacteria in their root nodules, which enrich the soil, a practice used in crop rotation. The atmosphere also generates contaminants through reactions with hydroxyl radicals.

Phosphorus

Most phosphorus is found in rocks. After weathering, it is absorbed by plants or carried to the sea. Phosphorus that reaches the sea is consumed by phytoplankton, and when these organisms die they may sink and form sediments, eventually returning to land through geological processes. Marine birds and their excrement also return phosphorus to the earth.

Sulfur

Plants absorb sulfur dissolved in water. It passes to herbivores, then to carnivores. After death, sulfur compounds are decomposed by bacteria and sulfur is released again. Sulfur concentrations increase due to coal combustion. In clouds, sulfur dioxide is transformed into sulfuric acid and returns to the earth as acid rain.

Acid Rain

Sulfur dioxide (SO₂) and nitrogen oxides emitted mainly from coal combustion react with sunlight and water vapor. Sunlight excites molecules that produce hydroxyl radicals (OH), which transform nitrogen oxides into nitric acid and SO₂ into H₂SO₄, producing acid rain.

The Greenhouse Effect

Greenhouse Effect (Efecto invernadero)

A natural phenomenon in which the presence of certain gases in the atmosphere retains part of the heat from the sun, maintaining the planet's temperature. Because of gases such as CO₂, human activity has increased this effect, causing the planet's temperature to rise.