Heavy Metal Mobility and Essential Nutrient Cycles
Heavy Metals in the Food Chain
One of the primary mechanisms by which heavy metals reach human beings is through plants, which absorb metals through their roots. In turn, animal species consume these plants, allowing the metals to enter the food chain. The metals most dangerous to all life forms are mercury, cadmium, and lead. Additionally, iron, aluminum, copper, and zinc are particularly hazardous for salmon populations.
Mobility and Soil Retention of Heavy Metals
Heavy metals can be retained in the soil, either dissolved in soil solutions or fixed by adsorption, complexation, and precipitation. Their mobility is characterized by the following processes:
- Absorption: Metals are absorbed by plants and incorporated into food chains, or they may pass into the atmosphere through volatilization.
- Mobilization: Metals can move into surface water or groundwater systems.
Volcanic Sources of Heavy Metals in Chile
Natural sources of heavy metals in Chile include volcanic activity from the Llaima and Chaitén volcanoes.
Essential Nutrient Cycling in Nature
What is a Nutrient?
Cycles in nature occur continuously to sustain life. A nutrient is a necessary component required for organisms to nurture themselves and provide better conditions for the soil. Nutrients considered essential and enriching to the soil include nitrogen, phosphorus, potassium, and sulfur.
The Nitrogen Cycle
Nitrogen is a fundamental element present in living organisms like plants and animals. It is also an important part of non-living matter, such as the air and the ground. Nitrogen atoms do not stay in one place; they move slowly between living and dead matter, air, land, and water. Organisms employ nitrogen in the synthesis of proteins, nucleic acids (DNA and RNA), and other basic molecules of metabolism.
The Phosphorus Cycle
Phosphorus is released from rocks into the soil, where it is used by plants to perform vital functions. Animals obtain phosphorus by eating plants or other animals that have eaten them. During the bacterial decomposition of organic matter, phosphorus is released as orthophosphate (H2PO4-), which can be used directly by green plants to form organic phosphate (plant biomass). Rainwater can carry this phosphate to the ocean or aquifers.
The Importance of Potassium
Potassium (K) is an essential element for plants, animals, and humans because it is involved in photosynthesis and chemical processes within cells, and it helps maintain cellular water balance. This is why potassium, along with nitrogen and phosphorus, is an essential element for living organisms.
The Sulfur Cycle
Sulfur is a key component of proteins. Plants and other primary producers obtain it mainly in the form of the sulfate ion (SO42-). These organisms incorporate it into protein molecules, which then pass to higher trophic level organisms. When organisms die, their sulfur-protein derivatives enter the sulfur cycle and are transformed so that plants can use them again as sulfate ions.
The Fundamental Water Cycle
The water cycle is the process that water follows as it passes from the Earth to the atmosphere and back to Earth. Through this cycle, various bodies of water are maintained, including seas, rivers, and lakes. The primary processes occurring in this cycle include:
- Evaporation
- Condensation
- Precipitation