is the third most abundant element in the earth's crust. Calcium is a component of bones and teeth and plays an important role in cell metabolism, the nervous system (muscle contraction) and blood clotting. As a natural component of water, together with magnesium it stabilizes the pH value and influences water hardness.
Magnesium, together with other alkaline earth ions, is responsible for water hardness. Hard water has a high / soft water only a low content of alkaline earth ions.
Magnesium naturally enters the environment almost everywhere, as it is present in rainwater, rivers and seawater. Since many minerals, such as dolomite (calcium magnesium carbonate) contain magnesium, it is washed out of rocks and into bodies of water. It is also an ingredient in fertilizers and an additive in livestock feed, from where it also readily enters the environment.
Magnesium is vital to almost all living things (except insects).
As the central atom in the chlorophyll molecule, it is necessary for photosynthesis in plants.
Humans need about 200-300mg of magnesium daily. It is present in the body in an amount of about 25g (60% in the skeleton/ 40% in muscles and other tissues).
Magnesium is a component of many enzymes and is jointly responsible for membrane functions, transmission of stimuli, muscle contractions, the building of proteins and the duplication of DNA.
Magnesium and calcium often have the same functions in the human body, but also often act as antagonists (opponents).
Since there are no adverse effects to humans or animals from magnesium, there is no guideline for magnesium levels in drinking water.
Sodium is a vital element and is found in practically all water. If ion exchangers are used for water softening, the hardness components calcium and magnesium are exchanged for sodium. This can lead to a considerable increase in the sodium concentration. Infants are particularly sensitive to sodium because their kidneys are not yet fully mature. Increased intake also affects the child's intestinal flora. Water softeners should therefore be adjusted so that the balance between calcium, magnesium and sodium is not upset and the water hardness is not too low.
Nitrate enters the soil through mineralization of organic matter, inputs of nitrogen oxides as nitrous acid, nitrification of ammonium nitrogen from manure and slurry, and via mineral fertilizers. If the supply of nitrate is higher than the demand of the plant or if there is an increased supply of nitrate in the soil outside the growing season, there is a risk of leaching into the groundwater. This is not only an economic loss and a deterioration of fertilizer efficiency, but also a danger to groundwater. Nitrate itself is relatively harmless to humans and is excreted through the kidneys. What is dangerous about nitrate is that it can be reduced to nitrite in the stomach. A high intake of nitrate or nitrite poses a considerable health risk to humans. So-called methemoglobinemia (cyanosis) can occur in infants. Another risk is that nitrosamines can form from nitrite and amines (protein building blocks). These are considered carcinogenic. A limit of 50 mg/l would be set for nitrate, and 0.5 mg/l for nitrite. The sum of the nitrate concentration divided by 50 and the nitrite concentration divided by three must not be greater than 1.
The toxicity of ammonium is low. However, ammonium is an indicator of contamination of well water by sewage, manure or slurry. A limit value of 0.5 mg/l applies.
Sulfate occurs in all waters and is an essential mineral constituent. Between 20 and 50 mg sulfate/l are found in uncontaminated groundwater. In well systems, elevated sulfate levels may be due to geology (e.g., gypsum kuper), but may also indicate contamination by fertilizers and wastewater, since it is easily washed out. From 250 mg and more, it disturbs the stomach and intestines and has a laxative effect. The taste of the water is then also impaired.
The total hardness of tap water is the sum total of the alkaline earths calcium and magnesium dissolved in the water. It depends on the geological origin of the water. The higher the content of calcium and magnesium, the higher the total hardness. This degree of hardness is expressed in German degrees of hardness, or °dH for short. If the hardness is too high, the aroma of coffee, tea and cocoa suffers because the tannins precipitate as lime salts. From a hardness level of 21 °dH, softening is recommended.