VietNamNet Bridge – Observation results show that the air pollution at night exists, but the pollution is still below the allowed level. However, if comparing the pollution level now and that of 5-7 years ago, one would see that the daytime pollution and the pollution at night have been increasing.

The figures that can talk

On December 2, reporters were present at the Center of Hydrometeorology and Environment Network to learn about the air quality at night. Nguyen Nhat An from the Center for National Hydrometeorology showed the reporters how to check the results of measuring concentrations of components in the air with the dates chosen.

The figures appeared on the computer with the software allowing to handle with the monitoring data from nine observation stations across the country. This is considered the most important repository tables reflecting the environmental indicators.

According to Anh, in principle, there is less dust at night than the daytime. The meter detects dust with beta rays. The TSP parameters (mg/m3) and PM10 (mg/m3) showed the air pollution at night.

On November 23, for example, the TSP indicators were 137 at 7 pm, 143 at 8 pm, 123 at 9pm, 155 at 10 pm, 182 at 11 pm and 167 at noon of the next day. Meanwhile, the PM 10 indicators of the day were 100 at 7 pm, 86 at 8 pm, 10 at 9 pm, 111 at 10 pm and 85 at 11 pm.

The figures prove that the air at night is polluted. There are the big gaps in the TSP indicators between daytime and at night with the TSP indicator on daytime higher than at night.

On November 23, for example, TSP indicators at the hours at night did not exceed 200/h. Meanwhile, the TSP indicators at some moments of the daytime were very high. For example, at 10 am, the TSP was 899, while the figure reached 1314 at 12 pm.

On November 18, TSP jumped to 2056 at 10 am, while TSP indicators at other moments of the daytime were also higher than that at night.

Meanwhile, there is no big gap in the PM10 indicator between daytime and night.

Explaining this, Bui Hoai Thanh, MA, said that TSP dust is a “dust in general” which comprises both big and small specks of dusts. Therefore, on daytime, due to the intensive transport, construction activities, the volume of the dust is big. Meanwhile, at night, as the traffic eases, the amount of the dust decreases.

As for PM10, this is a kind of small dust. The specks of dust float in the air; therefore, they are not influenced by mankind activities. Moreover, observation stations are put about 50 meters far from the main roads, therefore, big specks of dust cannot diffuse inside.

Pollution higher in winter

Anh said that the air in winter is always more polluted than in summer because of the lower humidity. Winter means the dry season, therefore, dust diffuse more in the air. Meanwhile, in summer, due to the high humidity, dust cannot go far. As such, the TSP dust pollution is higher than PM10.

However, Anh has warned that the pollution at night is now as high as the pollution on daytime, because many vehicles are now in circulation at night. At construction sites, cement plants, the dust concentration is always high at night and on daytime as well.

In fact, factories release the figures about the air pollution already, but Anh said that the figures are just for reference, and which cannot be used as the foundation to make conclusion if there is pollution.

“It is necessary to carry out many other independent research works,” Anh said.

Source: Bee.net