For hundreds of millions of people around the world groundwater is the main source of fresh water. For example, in many regions of Asia and South America they are used for irrigation of agricultural crops — drought conditions do not allow rains to reach these areas. Others often use groundwater as alternative water source for drinking, believing that it is healthier. However, scientists have found that in some countries the use of such waters can be dangerous due to the high concentration of such hazardous substances as arsenic. And poisoned they can not only while drinking this water, but also in the use of, for example, rice, which it watered.
Thanks to many years of research, scientists from the Swiss Federal Institute of aquatic science and technology has developed a map of the distribution of arsenic in groundwater worldwide. They spent about 200 thousand analyses of water in China, Mexico, South and South-East Asia, USA and some other countries. Still it was impossible to ascertain the risk of arsenic poisoning by drinking spring water because it required the use of water resources in different regions and characteristics of agriculture in the country.
Ground water imagine a layer of fluid in the loose rocks of the earth. They are formed by the seepage into the ground rainfall, and the waters of rivers, lakes, reservoirs and other water bodies. Often they come to the surface in the form of springs.
At the same time, not to be confused with ground water from artesian sources. Artesian water is located much more deeply underground and is characterized by the presence of strong pressure.
According to the standard world health organization (who), allowable concentration of arsenic in drinking water is not more than 10 milligrams per liter 1. However, scientists have identified several places on Earth where it is higher (more than 50 milligrams per 1 liter), mostly in South Asia. The nidus of arsenic in water have also been found in the United States and in Argentina.
Red represent arsenic concentrations greater than 50 milligrams per 1 liter
As physically impossible to measure the content of hazardous substances in the groundwater at each location of the planet, researchers using mathematical modeling made a map to identify previously unknown areas of contamination with arsenic. The most dangerous pattern is still observed in Asia and South America. The citizens of Europe and Russia and participants can not worry — in their groundwater, most likely, the arsenic concentrations not high enough to cause any health problems. However, if to speak about Russia, then on the map you can track that in groundwater in the Western part of the country arsenic is considerably less (no more than 0.2 milligram per liter), whereas closer to Asia is purely can reach up to 0.6.
the Alleged picture of the distribution of arsenic in groundwater of the Earth
According to the final risk assessment, the threat of slipping arsenic into the body is exposed to up to 220 million people around the world. This raises some concerns because in Asia, for example, groundwater is widely used for water projects. And thanks to the springs for local residents collect them from drinking water.
What are the dangers of ingestion of arsenic in the human body? First, it is a very toxic chemical element. Known cases where even in dentistry, the doctors incorrectly calculated necessary concentrations for the patient (not taking into account chronic diseases and allergic reactions), and eventually the man died. In a small amount of arsenic leads to skin diseases and nervous system, but if its concentration is higher, arsenic may cause diseases of the cardiovascular system and the rapid development of cancer.
However, there are among living beings, and exceptions. For example, last year scientists discovered in the Pacific ocean microbe, which . This form of life was almost forced to breathe poison — under water, very little oxygen, so the adaptation was the only way to survive. In addition to arsenic, micro-organisms can breathe sulfur and nitrogen — researchers have to conduct laboratory experiments to carefully study what is happening inside them.
A at the expense of the citizens of San Antonio de Los Cobres in Argentina is able to drink water, arsenic levels which exceed safe 80 time. The gene allows the body to process arsenic, not allowing it to accumulate in dangerous concentrations, so the owners of these microscopic mutants can eat as much arsenic as long as they like. However, such "immunity" is only 6 000 people in the world.
How arsenic ended up in the groundwater of the Earth? It is contained in iron-containing minerals near aquifers and due to chemical processes is slowly released into the water. This process is time-consuming, and unlikely even after 100 years the concentration of arsenic will be a threat worldwide, but now this element can trigger the growth of dangerous diseases in the Asian region where not only drink mainly only ground water, but also cook with it and grow food crops.
Groundwater isthe only source of fresh water for millions of people.
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