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    In the composition of the air, 20,94% is Oxygen (O2) which nourishes all the cells of the human body. Absolutely dry air without moisture, clean, contains three main gases in which 78,08% is Nitrogen (N2), 20,94% is Oxygen (O2), 0,93% is Argon (Ar). The remaining about 0,043% are usually CO2 (0,04%), Ne (0,0018%), He (0,0005%), CH4 (0,0002%) and H2 (0,00005%). Except for the 3 main substances that make up the dry air mentioned above, other substances present in the air at very small concentrations, below the allowable standards are considered acceptable impurity. If they have concentrations above the allowable values, they are considered pollutants and the air in such a state is polluted air.

    Human’s production activities (industry, agriculture, construction, transportation, etc.), waste incineration, cooking, domestic activities have released many different compounds into the air that make up two main groups of pollutants: Polluting gases such as NOx, SOx, O3 (Ozone), CO, CO2, TVOC, Formadehyde ... have extremely small molecular sizes, about less than 5 nanometers (1mm = 1.000 µm = 1.000.000 nm); Dust particles, including airborne dust, are ≤ 100 µm in diameter, PM10 fine dust (diameter is ≤ 10 µm), PM5 fine dust (diameter is ≤ 5 µm), PM2.5 ultrafine dust (diameter is ≤ 2,5 µm), and PM1 ultrafine dust (diameter is ≤ 1 µm). The thickness of the hair is about 100 µm therefore these fine dust particles can not be seen by naked eyes. Dust particles smaller than PM10 exist in the air for a long time, directly affecting human’s health.

1. Bases for assessing the level of urban air pollution in Việt Nam

    Bases for assessing the level of urban air pollution are to compare the actual air pollution monitoring data and allowable values in environmental standards according to National Technical Regulation on Ambient Air Quality QCVN No. 05:2013/BTNMT (Table 1).

 

Table 1: Maximum values of basic parameters of ambient air (µg/m3) according to QCVN 05:2013/BTNMT

No.

Parameters

1-hour average

8-hour average

24-hour average

Annual average

1

SO2

350

-

125

50

2

CO

30,000

10,000

-

-

3

NO2

200

-

100

40

4

O3

200

120

-

-

5

TSP

300

-

200

100

6

PM10

-

-

150

50

7

PM2.5

-

-

50

25

8

Lead (Pb)

-

-

1.5

0.5

 

    As the Table 1 shows, the QCVN 05:2013/BTNMT provides the allowable hourly, 8-hour, 24-hour (daily), annual average values. Therefore, it is necessary to compare the hourly, daily or annual average values collected by the monitoring system with the hourly, daily or annual average values in the National Technical Regulation. If we take the monitoring values for each instant measurement and compare with the average values in the Table 1 to assess the level of urban air pollution as some media have shown in the recent time, it is completely incorrect.

    Next, it is necessary to assess the level of urban air pollution by the Air Quality Index (AQIx) according to the Circular No. 1459/QD-TCMT dated 12th November 2019 of the Vietnam Environment Administration, that:

    AQIh values of parameters SO2, CO, NO2, O3 are calculated according to Formula 1, AQIh values of parameters PM10, PM2.5 are calculated according to Formula 2:

    Good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, hazardous AQI levels and their interaction with human’s health are provided in Table 2.

 

Table 2: AQI levels and their effects on human’s health

AQI value range

Air quality

Effects on human’s health

0 - 50

Good

No health risk

51 - 100

Moderate

Sensitive groups should limit their time outdoors

101 - 150

Unhealthy for sensitive groups

Sensitive groups should limit their time outdoors

151 - 200

Unhealthy

Sensitive groups must limit their time outdoors

201 - 300

Very unhealthy

Sensitive groups avoid going outdoors, others are limited to outside

301 - 500

Hazardous

Everyone should stay indoors

 

    AQI = 101 ÷ 200: Corresponding to air quality that is unhealthy for sensitive groups and unhealthy. AQI = 201 ÷ 300: Air quality is very unhealthy. AQI = 301 ÷ 500: Air quality is hazardous. Typically in Hà Nội, the number of days in 2014 with AQI as unhealthy for sensitive groups accounts for more than 50% of the total number of monitoring days in the year, even, there were days when air quality declined to a very unhealthy and hazardous threshold (AQI > 300).

2. Development of air pollution in some urban areas in Việt Nam in recent years

    So far, no locality has officially announced the environmental monitoring results in 2019. Based on the information of the Center for Environment Monitoring of the Vietnam Environment Administration (VEA) in 2019, there are 3 typical graphs of the state of pollution development of air environment components in the last 6 years (2013 - 2018): Graph 1, Graph 2 and Graph 3 below.

 

Graph 1: Development of annual average concentration of PM2.5 fine dust in automatic monitoring stations located in Hà Nội, Phú Thọ, Quảng Ninh and Đà Nẵng                                                                              

in the period of 2013 - 2018 (Source: VEA, March 2019)

 

Graph 2: Development of TSP concentration in some urban centers of Thừa Thiên - Huế, Đà Nẵng, Hồ Chí Minh City, Bình Dương, Đồng Nai in the period of 2016 -2018 (Source: VEA, March 2019)

 

Graph 3: Development of annual average NO2 concentration in some residential areas in the period of 2011-2015 (Source: VEA, Institute for Environment and Resources of National University of Hồ Chí Minh City, Departments of Natural Resources and Environment, 2015)

 

    From above graphs, problems of air pollution in some urban areas in Việt Nam in recent years are as follows:

PM10, PM2.5 dust pollution: The PM10 and PM2.5 fine dust monitoring data of 6 automatic air monitoring stations in Hà Nội, Hạ Long, Việt Trì, Huế, Đà Nẵng and Nha Trang cities show that dust pollution continues to be a prominent problem. However, the Graph 1 shows that PM10 and PM2.5 fine dust pollution in the air in Hà Nội, Việt Trì, Phú Thọ cities has tended to decrease in recent years. The PM10 and PM2.5 fine dust pollution in the air of Hạ Long City has a little change and is approximating the allowable standard value. The concentration of PM10 and PM2.5 fine dust in the air of Đà Nẵng City is lower than the allowable standard value. In general, according to the monitoring data of automatic monitoring stations in 6 cities (Hà Nội, Hạ Long, Việt Trì, Huế, Đà Nẵng and Nha Trang), the fine dust variability from 2011 to 2018 has been improved. Specifically in Hà Nội, the ratio of the number of days with PM10 dust concentration exceeding the allowable standard value according to QCVN No. 05:2013/BTNMT in 2010 was 13,13%, in 2015 was 6,87% and in 2018 was 1,93%; PM2.5 in the same years was 61,25%, 33,91% and 19,69% respectively. The air quality in the 3 Central coastal provinces (Huế, Đà Nẵng and Nha Trang) was still relatively good (almost without dust pollution). Specifically, the above ratio of 2015 for PM10 in Huế was 3,67%, Đà Nẵng was 2,86% and Nha Trang was 0,0%.

Total suspended particles (TSP) pollution: Construction activities are a major source of TSP. In the same city, TSP monitored at different locations will have different results and depend on the construction activities allocated in the city. In recent years, in Hà Nội City, the concentration of TSP at the monitoring stations on the roads of Phạm Văn Đồng, Trường Chinh, Vĩnh Tuy, Mai Động... was still at heavy and very heavy pollution level.

    The fluctuation of dust concentration in the Northern urban areas is very clear in a year from October to April, the dust concentration is greater between May - September, whereas in the Central coastal cities, the dust concentration varies by season not significant. The dust concentration varies by hour of day in the 6 cities mentioned above is similar, maximum at peak hours and smallest at noon (13 - 14 hours). The average PM2.5/PM10 dust concentration in the above cities is about 0,57 - 0,72.

    Coastal cities all have better air quality than inland urban areas far from the sea. For urban areas in the South, the climate during the year is divided into dry and rainy seasons. Concentrations of PM10, PM2.5 dust have significant differences between the two seasons, the rainy season (May to November) and the dry season (December to April), the concentration of urban dust is often high in the dry season and low in the rainy season.

    NO2, SO2, CO and VOC pollution: In urban areas, the sources of NO2, CO and VOC emissions are mainly from transportation activities, SO2 emissions are from coal and sulfur-containing oil burning (buses, industrial production if any and cooking using honeycomb coal).

    NO2 concentration: NO2 concentration in the air in some big cities such as Hồ Chí Minh City (Graph 3) in recent years has also exceeded the allowable limit. In many other urban areas, the NO2 concentration is lower or approximately equal to the allowable limit.

    VOC concentration: In urban areas, especially in areas with high frequency traffic, the emission of this organic compound may be from the exhaust gas of the transportation system. In some localities such as Hà Nội, Đồng Nai, VOC concentration in the air monitored at some locations in the period of 2011 - 2015 has exceeded the allowable limit.

    SO2, CO concentrations: In most urban areas, they are still within the allowable limit of National Technical Regulation.

    General assessment of urban air pollution: From 2013 to date, air pollution has been a downward trend in urban areas in Việt Nam, however, there has been a different increase/decrease in each time. In 2019, air pollution in Hà Nội and Hồ Chí Minh City is unusual compared to previous years with local pollution increased. In particular, in September 2019, PM2.5 fine dust pollution increased due to the least rain in the past 6 years. In September 2019, with the phenomenon of heat inversions, the suspended dust could not escape to high places. Besides, this time was in the rice harvest, the burning of straw in the suburbs has affected the air in the cities.

   In addition, depending on the location of different stations, air parameters are different. Where traffic jams, construction density is high, air pollution parameter is higher than elsewhere. Therefore, the air quality parameters in the city depend on the density of the monitoring stations.

3. Sources of air pollution and suggestions for improvements

    In order to take effective actions to prevent pollution and improve urban air quality, it is necessary to first identify exactly the major sources polluting the urban environment. According to urban research in Việt Nam, especially in large cities, there are 8 major sources of pollution such as: Pollutants discharged from exhaust pipes of motor vehicles, especially from old vehicles and not regularly serviced and diesel vehicles; Emissions from new construction activities and repair of buildings, transport and urban technical infrastructure; Emissions from industrial and handicraft production facilities inside and around the cities; Poor street sanitation is a source of total suspended particles (TSP) and a part of fine dust (PM10, PM2.5); Emissions from honeycomb coal stoves are mainly pollutants such SO2, NO2, CO and TSP; Leaks and evaporation of petrol and VOC gases from petrol stations, from motor vehicles, paint and varnish production and painting and varnish places; Odors from sewers, ponds, rivers with polluted water environment; Straw burning during rice harvest season.

    Here are some solutions to improve urban air quality:

  • Promote the propagation, dissemination, education and guidance on the implementation of environment protection regulations. Mobilize the active participation of the community, every citizen, every production facility, every social organization in the air environment protection in particular and urban environment protection in general.
  • Strictly control transportation pollution sources. Immediate solutions: Need to control and check the sources of wastes from motor vehicles; conduct periodic inspections in accordance with the environmental technical regulations on gas emissions for all motor vehicles (different types of cars, especially buses, trucks, cars using diesel oil, and motorbikes); ban from circulation for all vehicles that do not meet the requirements of environment protection (including leakage of gasoline vapors); spray water to wash the roads on dry and sunny days. Long-term solutions: Complete a reasonable general urban masterplan, especially a smart urban transport masterplan; develop public urban transport systems such as bus, metro, skytrain systems...; encourage the formation of walking and bicycle streets; encourage the development of motor vehicles using gas, liquefied gas and electricity...
  • Focus on controlling, inspecting and strictly handling sources of dust pollution arising from new construction activities and repairing houses, urban technical infrastructure systems (transportation, water supply, drainage, electricity, gas, information cable systems...); apply less polluting construction technologies, such as not producing fresh concrete at the construction site but producing fresh concrete at the fresh concrete production stations and then transporting it to the construction site and pumping to the floors and columns of works.
  • Strengthen the capacity of air environment management agencies in Hà Nội, Hồ Chí Minh city and other major cities, such as establish an air environment management division at the environment protection agencies, additionally provide professionally trained staff on air environment to the environment protection agencies, as well as other environment management divisions in districts; organize refresher courses to improve the air environment management expertise for officials in the environment management system at all levels of major cities.
  • Strengthen inspection and control strictly of dust emission sources arising from transportation of bulk materials, especially transportation at night, vehicles transporting at night often violate environmental protection regulations.
  • Maintain streets clean, civilized and modern. Clean roads and sidewalks regularly to ensure that dust is vacuumed or washed; perform the collection, transportation and treatment of 100% of urban wastes with hygienic techniques. Educate people to keep the streets clean, not throw garbage into roads or throw garbage into drains, watercourses.
  • Strictly inspect and control volatile organic compounds (VOCs), especially gasoline vapors from petrol and oil trading stations, paint and varnish, petrol and oil production, processing and using facilities in urban areas; thoroughly treat water polluted rivers, lakes, ponds and drains; apply technical measures to treat dust generated from industrial and handicraft production in and around the cities.
  • Apply incentive policies to achieve the goal that by 2030 there will be no coal stoves in urban areas; apply necessary technological development policies so that suburban farmers stop burning straw during agricultural harvest.
  • Develop planting, tending and protecting trees in the cities, ensuring the norm of greenery area per capita to reach the prescribed values according to National Technical Regulation on Construction.
  • Prioritize the investment in improving the air environment monitoring system, especially the fixed automatic air monitoring system in urban areas. In Hồ Chí Minh City, there have been 9 - 11 automatic air monitoring stations but 100% damaged. Previously in Hà Nội, there have been 6 automatic air monitoring stations, now 5 automatic stations damaged, those replaced by sensor monitoring stations.

 

 

Prof. Dr. Phạm Ngọc Đăng - Vice Chairman

Vietnam Association for Conservation of Nature and Environment 

(Nguồn: Bài đăng trên Tạp chí Môi trường số Chuyên đề Tiếng Anh I/2020)

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