Why can there be a shortage of fresh water?
Drinking water shortages linked to impacts of change
According to statistics, almost 1/5 of the worldof the population lives in areas where there is a serious shortage of clean drinking water. In addition, 1/4 of the population lives in developing countries, which are experiencing water shortages due to the lack of infrastructure necessary for its withdrawal from aquifers and rivers.
One of the main problems is pollutionfresh water, significantly reducing the available reserves. This pollution is facilitated by industrial emissions and runoff, fertilizer runoff from the fields, and the penetration of salt water in coastal zones into aquifers due to pumping of groundwater.
How fresh water is polluted
- Pollutants enter fresh water in a variety of ways: through accidents, deliberate waste disposal, spills and leaks.
- The largest potential source of pollution isfarms that occupy almost 80% of the land in England and Wales. Some of the untreated animal manure that covers the soil enters fresh water sources.
- In addition, farmers in England and Walesthey apply 2.5 million tons of nitrogen, phosphorus and potassium to the soil, and some of these fertilizers end up in fresh water. Some of them are persistent organic compounds that enter the food chain and cause environmental problems. The UK is now phasing out the production of organochlorine compounds produced in large quantities in the 1950s.
- An increasing threat to freshwater reservoirs is posed by wastewater discharged by fish farms, due to the widespread use of pharmaceuticals to combat fish diseases.
- Rapid pollution of groundwater around cities. The source is the increasing number of contaminated wells due to improper operation.
- Forestry and open drainage - sourcesa large amount of substances entering fresh water, primarily iron, aluminum and cadmium. With the growth of trees, the acidity of the forest soil increases, and torrential rains form very acidic runoffs that are detrimental to wildlife.
- Atmospheric pollution of fresh water especiallydetrimental. There are two types of such pollutants: coarse (ash, soot, dust and liquid droplets) and gases (sulfur dioxide and nitrogen dioxide). All of them are products of industrial or agricultural activity. When these gases combine with water in a raindrop, concentrated acids are formed - sulfuric and nitric.
Global pollution of water bodies
- Ecological disasters. All serious cases of ocean pollution are associated with oil. As a result of the widespread practice of washing tanker holds, between 8 and 20 million barrels of oil are deliberately dumped into the ocean each year. In temperate climate sediments, the effects of oil spills can be observed for more than 9 months. In Arctic conditions, oil lasts much longer.
- Wastewater. In small quantities they enrich water and promote the growth of plants and fish, and in large quantities they destroy ecosystems. In two of the world's largest wastewater disposal sites - Los Angeles (USA) and Marseille (France) - specialists have been cleaning up polluted water for more than two decades. Satellite images clearly show the spreading of the wastewater discharged by the exhaust manifolds. Underwater filming indicates mass death of marine organisms.
- Metals and chemicals. Hazardous chemicals that can disrupt the ecological balance include heavy metals such as cadmium, nickel, arsenic, copper, lead, zinc and chromium. It is estimated that up to 50,000 tons of these metals are discharged annually into the North Sea alone. Even more alarming are the pesticides—aldrin, dieldrin, and endrin—that accumulate in animal tissue. The long-term effects of using such chemicals are not yet known.
- Impact on ecosystems. All oceans are affected by pollution, but coastal waters are more polluted than in the open ocean due to a much larger number of pollution sources: from coastal industrial installations to heavy shipping traffic. Around Europe and off the eastern coast of North America, shallow continental shelves are home to cages for oysters, mussels and fish that are vulnerable to toxic bacteria, algae and pollutants.
- Flowering water. First-order consumers cannot cope with the explosive growth of phytoplankton biomass, as a result of which most of them are not used in food chains and simply die off, sinking to the bottom. When decomposing the organic matter of dead phytoplankton, bottom bacteria often use all the oxygen dissolved in the water, which can lead to the formation of a hypoxic zone (with an oxygen content insufficient for aerobic organisms). Such zones lead to a reduction in biodiversity and biomass of aerobic benthos.
- Pollution from plastic waste. Accumulations of plastic waste form special garbage patches in the World Ocean under the influence of currents. There are currently five known large clusters of garbage patches - two each in the Pacific and Atlantic oceans, and one in the Indian Ocean. These waste gyres mainly consist of plastic waste generated by discharges from densely populated coastal areas of the continents.
How the world's water resources are distributed
About a third of all stocks are freshof water is concentrated in South America, a fourth of it is in Asia, and the countries of the post-Soviet space account for a little more than 20%. And only about 2% is distributed to the Middle East and North Africa.
The largest consumers of fresh waterconsidered India, China, USA, Pakistan, Japan, Thailand, Indonesia, Bangladesh, Mexico and Russia. At the same time, a particularly acute shortage of drinking water is observed in China, India and throughout Africa.
In addition to the lack of fresh water, there is anotherthe actual problem is its quality. Its deterioration directly depends on the increased level of environmental pollution. In most cases, this is due to human activities and overpopulation.
How to filter water so that it is not dangerous
Pure drinking water, strictly speaking, is calledit is impossible. From the point of view of a chemist, pure water is a distillate free from all impurities and microorganisms. For a microbiologist, clean water is an ideal environment for bacteria. For us, pure water is a liquid enriched with minerals, which can be drunk daily without risk to health.
Today there is no singlea universal method for purifying fresh water - its choice depends on the composition of the water, the requirements for it and the scope of further use. For example, there are ozone, osmotic, filtration and ionic purification systems, each of which has its own pros and cons.
The most promising technology so far isnanofiltration. This method will effectively eliminate even halogen organic and chlorine-containing impurities in water without the use of aggressive reagents. Nanofiltration is used in Holland, USA and France. This method is one of the most expensive, so it is not widely used. Even in countries where nanofiltration technology is used, they do it only for purifying water with a special purpose.
Water filtration methods of the future
- Nanofiber
Korean researchers have presented a newtechnology that makes sea water drinkable in a few minutes. The scientists used a membrane distillation process, which made it possible to achieve 99.9% purification of water from salt. They are confident the solution will ease the drinking water crisis worsened by climate change.
A new study details howseawater purification using a nanofiber membrane as a salt filter. Although scientists had used membrane distillation before, they encountered a problem that slowed down the process. If the membrane became too wet or flooded with water, it could no longer separate the salt.
Therefore, scientists had to wait for the membrane to dry, or come up with additional solutions, for example, using pressurized air to release trapped water from the pores.
- Latest desalination plants
Explorers from the Dalian MarineUniversities in China have developed a new desalination plant that can float on the surface of seawater, efficiently absorb solar energy, and use that heat to evaporate water.
The block itself consists of three layers:the main part is polyethylene foam, which helps it float and acts as a thermal insulator. The outside of the foam is wrapped in special paper - an absorbent material used in disposable diapers. It diverts water up to the surface.
It is important to note that the device manages to avoid one serious error - contamination due to the accumulation of salts on the surface. Over time, this reduces its effectiveness.
During tests, the team found that salineno layer has formed. This indicates that special pores on the block's coating drain the salt and dump it back into the seawater. Another benefit, the team said, is that the paper material can be reused more than 30 times.
- Palladium and Gold Nanoparticle Catalyst
Chemists at Cardiff University have created a catalyst for instant water disinfection based on palladium and gold particles.
The authors of the work discovered that in the processThe synthesis of H2O2 produces many other molecules containing oxygen, which interact with microbes tens and hundreds of millions of times more actively than peroxide and bleach.
A similar level of bactericidal activity of these compounds,as noted by Hutchins and his colleagues, it allows for almost instant water purification from microbes, spores and other organic contaminants that can negatively affect human health.
- Flexible membrane
Chemists at the University of California, Berkeley have found a way to make it easier to remove toxic metals such as mercury and boron from water.
A new membrane-based method removes almost 100%toxic metals and releases valuable metals for later use or disposal. According to the authors, the membrane is easy to integrate into current water treatment systems.
Under development, chemists from CaliforniaThe University of Berkeley has synthesized flexible polymer membranes with nanoparticles that can be tuned to absorb specific metal ions, such as gold or uranium.
The membrane can be tuned to a specific type of particles that it will absorb.
- Wood filters
Scientists at the Massachusetts Institute of Technology used the sapwood of non-flowering trees to create a filter for drinking water from natural materials.
They made new xylem filters thatfilter out pathogens such as E. coli and rotavirus. Laboratory tests have confirmed that their development removes bacteria from contaminated springs and groundwater. Scientists have also developed simple methods to extend the shelf life of filters. As a result, wood discs can purify water for at least two years.
Consequences of water scarcity
Lack of clean water forces peopleuse water from unsafe sources for drinking, which is associated with an increased risk of harm to health. Consumption of contaminated fresh water leads to deterioration of living conditions and the development of serious diseases, including death.
Due to the lack of water, there is a practice of storingwater in homes, which can significantly increase the risk of pollution and create favorable conditions for the growth of harmful bacteria. Hygiene is also a serious problem: people cannot properly wash themselves, wash clothes and keep their homes clean.
If no measures are taken, then by 2030 almost 5 billion people - about 67% of the planet's population - will remain without satisfactory water purification.
Today, for every inhabitant of the Earth there are about750 m³ per year of fresh water, by 2050 this amount will decrease to 450 m³. Up to 80% of the world's countries will find themselves in an area that, according to the UN classification, is classified as below the water scarcity line.
In Africa alone, by 2020, due to climate change, between 75 and 250 million people will find themselves in such a situation. Lack of water in desert and semi-desert regions will cause intensive migration of the population.
Most of India is already suffering from the lack of drinking water.
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