Does water that circulates constantly also have an age?

Recently, a bottle of mineral water with a "water age of 16,500 years" has sparked heated discussions online. The incident started when a citizen spent 15 yuan on a high-speed train to buy a bottle of mineral water in a plastic bottle with the words "water age 16,500 ± 150 years" written on it. He joked, "It's like drinking antique (water)" and posted a picture.

In this regard, netizens have expressed their opinions. Some feel that there is nothing wrong with it: "Every water molecule is a relic from ancient times. No matter how it is disinfected, it will be the same. There is nothing wrong with writing it this way." Others questioned: "This is misleading consumers."

There are many different opinions on the definition of "water age" among merchants, and there is no unified standard. The merchant of the "16,500-year-old water" that caused heated discussion claimed that it was glacial water from Mount Everest, which gushed out to the surface through the spring at the foot of Mount Everest. The water that came out was about 16,500 years old.

In fact, in the promotion of various mineral waters and glacier waters, many are claimed to be "100-year-old" or "1,000-year-old". Are you wondering, can the age of water really be measured when water is constantly circulating?

#01「What is water age?」
The water on the surface of the earth is constantly flowing and is constantly "reborn" through the surface water cycle. In contrast, the water that enters the ground circulates much more slowly, and its life cycle is therefore longer. Therefore, when we talk about the age of water , we are mainly referring to the age of groundwater.

Groundwater cycle

Generally speaking, groundwater goes through three processes: recharge, runoff, and discharge. That is, water seeps into the underground from the surface, flows underground and then returns to the surface. The time of this cycle can be as short as a few days or as long as millions of years. The time that groundwater stays underground is called the age of the groundwater.

#02「How to calculate water age?」
There are many ways to test water age, mainly hydrodynamic method and hydrochemical method. The hydrochemical method is more commonly used and is essentially a radioisotope method. Based on the constant decay rate of radioactive elements, specific radioactive elements in groundwater are selected, and the content of radioactive elements before and after decay is measured respectively, so that the age of groundwater can be calculated.

Commonly used groundwater dating isotopes and their dating ranges

Among them, the more mature isotope measurement method is the carbon-14 method. However, the number measured by the carbon-14 method is called the apparent age of water, not the absolute age. Because water is flowing, the aquifer in the stratum may be very old. If there is young or old water replenishment, the age of the entire water will be different, so there is no one-to-one correspondence. In this news event, referring to the water age test report and directly saying the age of the water is actually unscientific.

#03 "The older the water, the better the water quality?"

Whether the water quality is good or not is related to the trace elements it contains. Relevant experts said that high-quality water and water age are two different things. The age of water can only represent that this is relatively clean water without some of the current industrial pollution.

Ancient groundwater flowing out of the cracks in the rock mass of the mine

The older the groundwater is, the more likely it is to taste disappointing. Due to being sealed underground for a long time, the water has a high mineral content and often tastes bitter and astringent.

However, studying and identifying the age of groundwater is still of great significance for understanding the groundwater cycle and regeneration process, clarifying the type of water genesis and water resource evaluation, etc. It can provide important parameter indicators for the sustainable development and utilization of groundwater.

Water age does exist, but mineral water that is tens of thousands of years old may be just one of them. We need to be cautious about over-packaging corporate marketing.

China Water Affairs Comprehensive CCTV.com, Upstream News, compiled by Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences