The source of life – water
Although 70.8% of our planet is covered by water, freshwater resources are extremely limited. Of the total water resources, 97.5% are saltwater and cannot be directly drunk. Of the remaining 2.5 percent of freshwater, 87 percent is hard-to-use ice sheets at poles, glaciers in high mountains, and ice and snow in permafrost zones, so less than 0.3 percent of the total global water can actually be used directly by humans. Due to the general scarcity of freshwater resources in many parts of the world, and the face of pollution problems, coupled with the increase in population numbers, economic and social development, industrial and agricultural water use, urban water consumption continues to increase, so it is necessary to carry out overall planning and management of water resources. According to statistics released by the United Nations, 1.1 billion people worldwide currently lack access to safe drinking water. China's per capita water resources are only 2200 cubic meters, about 1/4 of the world's per capita, and it has been listed as a water-poor country by the United Nations. Among them, freshwater salinization is a cause of the scarcity of freshwater resources.
How to evaluate the saltiness of fresh water?
At present, the salinity of inland freshwater bodies in the world has generally increased, and this phenomenon is called "freshwater salinization syndrome". Freshwater salinization, commonly known as freshwater salinity, refers to the gradual increase in salinity of inland freshwater. In general, the salt content concentration of fresh water ranges from 0.01‰ to 0.5‰. On average, 1 liter of seawater contains about 35 grams of salt, and 1 liter of fresh water contains less than 0.5 grams (5/10,000) of salt. The salt content of semi-brackish water is between 0.5‰ and 30‰, of which oligoline contains 0.5‰ to 5‰, medium brine contains 5‰ to 18‰, and polyline contains 18‰ to 30‰.
In fact, "the fate of water is not in its own hands", there are many factors that cause the salinization of fresh water, including natural and human factors: sea level rise, seawater invasion, global climate change, non-point source pollution, sewage discharge, etc.
The more you drink, the more thirsty you get, just because you haven't drunk the right water
In the hot summer, sweating like rain, thirsty to a cup of cool white, instantly refreshing, full of happiness. True so-called, "happy drink cool white, healthy and comfortable in their own heart." However, can you imagine what it would be like to have only a glass of brackish water when you are thirsty? How can a "sad" word be obtained? Humans are also intolerable, not to mention miniature creatures that have been living in fresh water.
What is the harm in salting fresh water?
Salty fresh water not only directly affects our drinking water resources, but also damages infrastructure; for example, water and drainage piping systems are more susceptible to corrosion and damage. The saltiness of freshwater has a very large impact on the organisms living in freshwater. For example, high salinity has a great impact on the reproduction and egg development of freshwater fish, seriously affecting the growth of fish. Scientists have found that the freshwater four large fish (green, grass, silver carp, bighead carp) that we often say grow slowly and die quickly in water bodies with a salinity of more than 20 ‰, and the baby fish is born less and the survival rate is low. In addition to large individual fish, there are thousands, or even hundreds of millions, of micro plankton per liter of fresh water, which are difficult for us to directly observe and identify with the naked eye, and can only be observed with the help of microscopes. So, what effect does the saltiness of fresh water have on these tiny beings? Will they also be salted to death? To answer this question, the researchers chose the Xinglin Bay Reservoir in the coastal city of Xiamen for 13 months of follow-up studies.
Fresh water becomes salty, and some miniature plankton are really salted to death!
Due to the intrusion of seawater and the discharge of domestic sewage, the salinity concentration of Xinglin Bay Reservoir has changed significantly, from 0 to 6.1 ‰, exceeding the range of fresh water and reaching the level of oligosalline water and medium brine. The study found that a slight saltiness (i.e., a small increase in salinity) of fresh water in urban reservoirs can lead to the threat of death of micro-eukaryotic plankton-sensitive species and lead to significant reductions in biodiversity. Miniature eukaryotic plankton can be divided into core taxa with high abundance and low diversity and satellite taxa with low abundance and high diversity. The stability of the core plankton network is higher under low salinity conditions, while the stability of satellite plankton networks is higher under medium and high salinity conditions. These plankton community successions are of great significance for maintaining the stability and balance of aquatic ecosystems.
Protect freshwater resources and cherish every drop of water
Fresh water resources are what we usually call water resources, the pillars of the country are indispensable, and the water of life cannot be withered. General Secretary Xi Jinping pointed out, "Water is the foundation of survival and the source of civilization. "Man and nature are a community of life, and human beings must respect nature, conform to nature, and protect nature." A flood of clear water, used unconsciously, lost is difficult to survive. Therefore, to protect freshwater resources, we should start from me and start from the side. Shame on waste of water, proud of saving water; do not discard garbage at will, do a good job of garbage classification; do not use laundry detergent and laundry detergent with high phosphorus content to contribute to the prevention and control of eutrophication of water bodies; protect the environment is to protect water resources, and now the world is gradually warming, glaciers melt, causing a huge impact on the environment, which in turn will also threaten water security.
Protect freshwater resources, guard green homes, promote green development, and contribute to the construction of a green home where people and nature coexist in harmony!
Source: Institute of Urban Environment, Chinese Academy of Sciences