Types of urban disasters

Five kinds of urban disasters, including urban smog, photochemical pollution, heat island effect, solid waste and groundwater pollution.

1, smog

Haze weather is a state of air pollution, and smog is a general term for all kinds of suspended particles in the atmosphere, especially PM2.5 (particles with aerodynamic equivalent diameter less than or equal to 2.5 microns) is considered as the "culprit" causing haze weather.

With the deterioration of air quality, cloudy days are increasing and the harm is increasing. In many areas of our country, the smog weather phenomenon is combined with fog as an early warning and forecast of disastrous weather.

2. Photochemical pollution

Photochemical smog is mainly caused by the emission of automobile exhaust and industrial waste gas. When olefins and nitrogen dioxide (NO2) in automobile exhaust are discharged into the atmosphere, NO and NO2 are harmful photochemical pollution gases.

The molecules of these substances will become unstable after absorbing the energy of sunlight, and the original chemical chain will be destroyed to form new substances. This chemical reaction is called photochemical reaction, and its product is highly toxic photochemical smog.

3. Urban heat island effect

Due to a large number of artificial heating, buildings and roads, and the reduction of green space, the city is "hot". The phenomenon that the temperature in the city is obviously higher than that in the suburbs.

On the near-surface temperature map, the temperature in the suburbs does not change much, while the urban area is a high temperature area, just like an island protruding from the sea. Because this island represents a high-temperature urban area, it is vividly called an urban heat island.

The main factors forming urban heat island effect are urban underlying surface, artificial heat source, water vapor influence, air pollution, green space reduction, population migration and many other factors.

4. Municipal solid waste

Because there is no suitable treatment and disposal place, when solid waste is dumped at will and piled up in large quantities, it will not only hinder the city appearance, but also affect the urban environmental sanitation. At present, with the rapid increase of urban population, municipal solid waste is increasing at the rate of 8% ~ 10% every year, and solid waste is facing the difficult situation of nowhere to put it.

It seriously affects environmental sanitation and produces "visual pollution". The piled municipal solid waste is easy to ferment and rot, resulting in the breeding of mosquitoes, flies and mice, which is easy to cause the spread of diseases.

5. Groundwater pollution

The deterioration of groundwater quality caused by human factors. The main causes of groundwater pollution are: industrial wastewater is directly discharged into the ground, polluted surface water invades the underground aquifer, and human and animal feces or water polluted by excessive use of pesticides seeps into the ground.

The result of pollution is to increase the content of harmful components in groundwater, such as phenol, chromium, mercury, arsenic, radioactive substances, bacteria and organic matter. Polluted groundwater is harmful to human health and industrial and agricultural production.

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