Water and Soil: Resources, Usage, and Pollution
Water: A Vital Resource
The history of mankind has always been marked by the availability of water, which has encouraged the flourishing of civilizations. Water is essential for the existence and maintenance of organisms. It is vital for all necessary processes and reactions characteristic of living beings. A significant proportion of living things is water. Water flows on the earth’s surface between the oceans, atmosphere, and continents, in a process of continuous exchange called the hydrological cycle.
Drinking Water: A Scarce Resource
Most of the existing water (97%) is saltwater, forming the oceans and seas, and only 3% is freshwater. Part of it is in a solid state or in deep aquifers, making it difficult to use. The main source of water for human consumption and to meet the needs of other living beings is found in a liquid state in rivers, lakes, and relatively shallow aquifers. These accessible water sources represent less than 1% of the total terrestrial freshwater.
Water Use
Much of the water resources (70%) are used in agriculture, where often a significant proportion (up to 60%) is lost due to inefficient irrigation systems. Industry uses 22% of global water resources, and 8% is used for domestic purposes and services. In the last 70 years, consumption has increased six-fold, while the world population has tripled, which has doubled the consumption of water.
Water Pollutants
Emissions from agriculture, the livestock industry, and urban areas, including ranching and agricultural or industrial waste, can contain heavy metals and organochlorines.
- Physical contaminants: increase in temperature, radioactive particles, and suspended solids or particles of different sizes.
- Chemical pollutants: degradable substances, divided into biodegradable and non-biodegradable substances. Non-biodegradable substances are new to the system and do not have specific decomposers (e.g., plastics, medicines).
- Biological pollutants: viruses, bacteria, and other protoctists.
The Contamination of Surface Water
Decreased oxygen: Oxygen depletion is caused by the decomposition of organic matter contained in municipal and industrial discharges, which favors the proliferation of decay organisms. By raising these, oxygen consumption increases, which is called biological oxygen demand or BOD. Water eutrophication is due to the excessive growth of algae and cyanobacteria.
Contamination of Groundwater
Contaminants seep into the ground, contaminating groundwater. Other issues affecting groundwater are overexploitation and salinization.
Pollution of Seas and Oceans
Accidents involving oil freighters cause discharges known as oil spills.
Soil: A Foundation for Life
The soil is a material of the earth’s surface formed by the weathering of parent rock, which over time has turned into layers or horizons. It has physical and chemical characteristics that make it a biological medium that can harbor life within its interior and act as a substrate. It is differentiated from sterile soil by two types of components: mineral, formed by weathered material, and organic, named humus.
Origin of Soil
The process of soil formation starts with the colonization of bedrock by organisms with few nutritional needs, such as lichens. Over time, the remains are mixed with the eroded rock and transformed by decomposers, which eliminate waste toxicity and turn them into simple nutrients for plants. In the incipient soil, larger plants like mosses and ferns can be installed. This, together with plant remains and humic acids produced by plants, forms a progressively thicker layer of soil: mature soil.
Soil Erosion
Soil erosion is the loss of topsoil, rich in organic matter, due to the effect of wind or rain. The loss of topsoil is aggravated by the compaction of soil particles, which prevents the skidding of surface materials, and the reduction of vegetation.