Drinking water is contaminated? Can't electric cars or solar water heaters work?
These safety issues "surfaced" during the rainstorm
Our reporter Chen Xi
This year, the rain came early and the rainfall was heavy, and the country set new historical records. These strong convective weather phenomena such as lightning and rainstorm are closely related to human production and life. Under heavy rain, some people raised questions about the safety of drinking water sources, electric vehicles, and solar water heaters. There are also web-based videos linking heavy rain to mirages and other natural phenomena. In order to clarify the truth, a reporter from the Science and Technology Daily interviewed a number of experts in related fields to hear what they said.
Will it pollute the drinking water source? Controlling pollution sources is essential
The recent heavy rainfall in many places across the country has not only caused inconvenience to people's travel, but also made people worry: Will the heavy rain pollute the drinking water source? In this regard, Huang Jinhui, a professor at the School of Environmental Science and Engineering of Nankai University, said that the situation of heavy drinking water pollution caused by heavy rain requires specific analysis. The pollution risks are different in different places.
"First of all, it depends on where the source of drinking water comes from, whether it is groundwater or surface water." Huang Jinhui believes that if it is groundwater, it is necessary to analyze the geological conditions in this area. In some places, especially in mountainous areas, geological conditions have fissured rocks, which can cause rainwater to enter the ground along the cracks. If it is an alluvial plain, the infiltration of the descending water will pass through a very thick layer of clay. In the process of infiltration, it has actually filtered the particulate matter in the water. It should be noted that nitrogen, phosphorus and other chemical fertilizer components that are not absorbed by crops after agricultural cultivation and fertilization will quickly infiltrate into groundwater after heavy rain.
Huang Jinhui analyzed that if the drinking water comes from surface water. When it rains, the surface runoff flow increases, and the water collected from all directions eventually flows into the river, which is likely to cause non-point source pollution. In some places, garbage is thrown around and oil pollution is thrown. When it rains, pollutants from surrounding farmlands, industrial areas, and residential areas are washed into the river. Many reservoirs and lakes that serve as drinking water sources carry water from upstream rivers, so if pollutants flow down the upstream, the pollutants may enter the water source and the drinking water will be contaminated.
"To prevent the risk of water pollution caused by heavy rain, more is to control the source of pollution. Water is flowing and always flows from upstream to downstream, so whether upstream can take control measures determines whether it can protect downstream water quality." Huang Jinhui said.
Can you drive an electric car? Avoid "deep travel" and long time immersion
As a major means of transportation, electric vehicles are inevitable when driving electric vehicles to commute on rainy days. Professionals reminded that electric cars have waterproof design, but it does not mean that electric cars can "deep through" in water and soak for a long time. If the key "three electricity" components (battery, motor and electric control) enter the water, it will cause damage to the vehicle, resulting in a short circuit or failure to start.
"When it rains, electric vehicles can run normally. The lowest part of the electric vehicle chassis is the battery pack, and each battery cell and battery pack are waterproof. Currently, most of the protection levels of electric vehicles in China are above ip67 level. This level can achieve no problems with electronic equipment at a depth of 1 meter and half an hour without problems." Li Chuanpeng, project manager of the Management Department of China Automobile Data Co., Ltd. introduced.
"Although electric vehicles have strong wading capabilities, it is not recommended to go too deep in the water." Li Chuanpeng emphasized that if the water does not pass through the chassis, it is more dangerous to enter the cabin, because the wiring harness there may not be waterproof. Moreover, the main power supply is often connected to a "multipoint" harness to provide power for lights, air conditioners, and speakers. Electric cars are highly electronic, and their wiring harnesses are more than those of fuel cars. The water resistance of these harnesses is not so strong, which may cause a short circuit.
Can solar water heaters be used? The power supply should be cut off to prevent equipment damage
Summer stormy weather frequents, many people have such doubts and concerns: Can solar water heaters be used in thunderstorm weather? Will it be more prone to lightning strikes when using solar water heaters on rainy days? In response, Liu Chong, general manager of Tianjin Muge Technology Development Co., Ltd., said that qualified solar water heaters have lightning protection design, standard installation, and normal use are safe. However, in thunderstorm weather, electrical equipment may be damaged, so it is not recommended to use solar water heaters to take a shower in thunderstorm days.
Liu Chong introduced that solar water heaters are generally placed on the top of buildings, and buildings will have their own lightning protection devices. The location of solar energy is generally not higher than lightning protection devices. In addition, the solar water heater itself has a lightning protection design and has a grounded line. As the power supply enters the house, there is a neutral line and a live wire in the house, which can resolve the risk of lightning strike conduction. At the same time, the outer layer of the solar panel of the solar water heater is reinforced glass, the inner layer is a copper tube, and the outer skin is a synthetic plastic, which does not conduct electricity. Although the collector bracket is made of metal, it will be connected to the lightning protection belt or the ground terminal of the building when it is installed, and the risk of lightning strike will also be avoided.
"I have been in the business for about 10 years, and I have hardly heard of anyone being struck by lightning due to the use of solar water heaters when it rains." Liu Chong said, but the lightning will increase the power instantaneously and cause damage to the electrical appliances being used. Therefore, in thunderstorms, for safety reasons, the power supply of solar water heaters should be cut off as much as possible to prevent damage to electrical equipment.
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A mirage of mirages in the city after the rainstorm? fake!
Recently, in a video circulating on the Internet, some netizens said that after the rainstorm, a mirage appeared in the city. So after the heavy rain, can the mirage of mirage really appear in the city?
In this regard, Zhang Lianzhong, a professor at the School of Physical Sciences of Nankai University, said that Mirage is a natural phenomenon formed by the refraction of light, and is a virtual image formed by the light reflected by objects through the refraction of the atmosphere. Just like chopsticks inserted in a glass filled with half of water, you will see that the chopsticks are bent. This is because air, water, and glass have different refractive indexes. Normal air will have a small density change with height, and the refractive index will not change too much as the height increases. Sometimes special weather conditions can cause abnormalities such as temperature and power, which makes the density of the air more complicated and causes a change in the refractive index. Therefore, when a certain ground landscape spreads in the air, the refractive index The change of, it does not propagate in a straight line, but due to the change of refraction and reflection, it appears in another place. This is the simplest principle to form a mirage.
"The scientific principle of the Mirage is very clear and clear. The rainstorm should not be the cause of the Mirage, because the rainstorm will not directly cause the refractive index of the air to change." Zhang Lianzhong said that if the rainstorm is heavy, the rain will fall from high altitude. The air plays the role of filtering and cleaning. In this case, there will be no sudden change in the refractive index of the air.