**3.1. Concentration and distribution of aerosol nanoparticles in the Prague subway station Muzeum C**

In March 2011 an experiment was organized with the objective of measuring the distribution of size and concentration of aerosol particles in a very busy (changing) subway station in Prague. The location of the measurements was the station Muzeum C for a period of twelve hours (the data from the meteorological station were collected from 7:15 to 0:15, the measurements were performed from 7:40 to 0:28).

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**Figure 12.** Air flow speed in the proximity of the measuring technology

**Figure 13.** Overall concentration of aerosol particles during the subway operation

**3.2. Results of the measurements and discussion** 

reached between 13:00 and 14:00 hours).

station.

The temperature outdoors in the morning hours was -4 C, in the afternoon 2 C, and in the evening 0 C. The air flow on the surface was from 2 m.s-1 to 7 m.s-1 (the maximum was

The basic results of measurements of the overall concentration of aerosol particles during subway operation are shown in the diagram in Figure 13. The diagram of the concentrations of aerosol particles is completed with the intervals of subway trains passing through the

The measuring technology was situated in the middle of the platform (see Figure 11). The instrument enabled measurement in the range from 14.1 to 791 nm with a sampling interval of 5 minutes.

The trains on the line C are M1 (engine power 141.5 kW). The basic data about the platform dimensions are provided in Table 3.

**Figure 11.** Location of the measuring technology on a platform of the subway station Muzeum C


**Table 3.** Dimensions of the subway station Muzeum C

The temperature at the platform during the measurements was 12 – 13 C, after 21:00 hours the temperature dropped by 1.5 – 2 C, and the air flow at the measuring device had a pulsating character – see Figure 12.

**Figure 12.** Air flow speed in the proximity of the measuring technology

The temperature outdoors in the morning hours was -4 C, in the afternoon 2 C, and in the evening 0 C. The air flow on the surface was from 2 m.s-1 to 7 m.s-1 (the maximum was reached between 13:00 and 14:00 hours).

## **3.2. Results of the measurements and discussion**

426 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

measurements were performed from 7:40 to 0:28).

**Table 3.** Dimensions of the subway station Muzeum C

pulsating character – see Figure 12.

**subway station Muzeum C** 

dimensions are provided in Table 3.

of 5 minutes.

**3. Part II – Results of systematic measurements** 

**3.1. Concentration and distribution of aerosol nanoparticles in the Prague** 

In March 2011 an experiment was organized with the objective of measuring the distribution of size and concentration of aerosol particles in a very busy (changing) subway station in Prague. The location of the measurements was the station Muzeum C for a period of twelve hours (the data from the meteorological station were collected from 7:15 to 0:15, the

The measuring technology was situated in the middle of the platform (see Figure 11). The instrument enabled measurement in the range from 14.1 to 791 nm with a sampling interval

The trains on the line C are M1 (engine power 141.5 kW). The basic data about the platform

**Figure 11.** Location of the measuring technology on a platform of the subway station Muzeum C

The temperature at the platform during the measurements was 12 – 13 C, after 21:00 hours the temperature dropped by 1.5 – 2 C, and the air flow at the measuring device had a

Length of the station 194 m Depth of the platform center under the ground level 10 m Platform width 10 m Platform height 4.3 – 5 m The basic results of measurements of the overall concentration of aerosol particles during subway operation are shown in the diagram in Figure 13. The diagram of the concentrations of aerosol particles is completed with the intervals of subway trains passing through the station.

**Figure 13.** Overall concentration of aerosol particles during the subway operation

The diagram shown above indicates that the concentration of aerosol particles in the subway station is significantly affected by the frequency of trains passing through the station.

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Figures 15 and 16 are graphic renderings of distribution of the particles during the morning

and afternoon rush hours and during the traffic lows.

**Figure 15.** Distribution of particles during the morning and afternoon rush hours

**Figure 16.** Distribution of particles during the morning low

particles.

Figure 17 is a graphic rendering of the distribution of particles during the passage of the servicing locomotive that passed through the station after it was closed for passenger traffic. The diagram indicates a distribution shift to smaller, i.e. more dangerous dimensions of the

This fact has been confirmed by the following Figure 14, which presents a graphic rendering of the dependence of the overall concentration of aerosol particles on the number of trains passing through the subway station in both directions per hour. In theory, the diagram suggests that if there were no trains passing through the station the overall concentration of aerosols would be ca. 3400 particles per cm3.

**Figure 14.** Comparison of the overall concentration of particles with the number of passing trains

The summary of average concentrations of aerosol particles for the monitored period is shown in Table 4. As a curiosity, we have provided also the measured concentration of aerosol particles in the environment during passage of a servicing Diesel locomotive MUV – 72 (engine TATRA T 928 – 2 with engine power 130 kW) after the passenger traffic in the station was closed.


**Table 4.** Average concentrations of aerosol particles during the monitored period

Figures 15 and 16 are graphic renderings of distribution of the particles during the morning and afternoon rush hours and during the traffic lows.

428 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

aerosols would be ca. 3400 particles per cm3.

station was closed.

Maximum during the passage of the

servicing locomotive

The diagram shown above indicates that the concentration of aerosol particles in the subway

This fact has been confirmed by the following Figure 14, which presents a graphic rendering of the dependence of the overall concentration of aerosol particles on the number of trains passing through the subway station in both directions per hour. In theory, the diagram suggests that if there were no trains passing through the station the overall concentration of

station is significantly affected by the frequency of trains passing through the station.

**Figure 14.** Comparison of the overall concentration of particles with the number of passing trains

N.cm-3 Standard deviation

35500 -

Overall average (without the locomotive) 8200 ±1800 Morning rush hour (745 - 945) 10800 ± 950 Morning low (1130 - 1430) 7200 ± 420 Afternoon rush hours (1730 - 1930) 9980 ± 700 Night low ( 2200 - 030) 5520 ± 600

**Table 4.** Average concentrations of aerosol particles during the monitored period

The summary of average concentrations of aerosol particles for the monitored period is shown in Table 4. As a curiosity, we have provided also the measured concentration of aerosol particles in the environment during passage of a servicing Diesel locomotive MUV – 72 (engine TATRA T 928 – 2 with engine power 130 kW) after the passenger traffic in the

**Figure 15.** Distribution of particles during the morning and afternoon rush hours

**Figure 16.** Distribution of particles during the morning low

Figure 17 is a graphic rendering of the distribution of particles during the passage of the servicing locomotive that passed through the station after it was closed for passenger traffic. The diagram indicates a distribution shift to smaller, i.e. more dangerous dimensions of the particles.

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**Figure 18.** The subway vent shaft structure on the ground level near the busy road

**woods** 

This assumption has been confirmed by a comparison of the quantity of measured nanoparticles inside a train car on the subway platform on the line C with the quantity measured in a subway train car during its trip on the line C (see part I). The concentration of nanoparticles in the travelling train car was higher than at the same place measured on the platform. This is probably caused by the ventilation system of the cars which takes in the air from the tunnel premises, plus by the higher concentration of passengers per area unit.

**3.3. Aerosol and dust particles generated during processing of selected exotic** 

The objective of the measurements was to measure quantities and distribution of aerosol micro and nanoparticles generated by individual technological steps during processing of various types of tropic woods used on the market in the Czech Republic. At the same time, we also focused on the microstructure of the wood dust in the deposits and difference in the

**Figure 17.** Distribution of particles during the passage of the servicing locomotive

*What are the supposed sources of nanoparticles on the subway station platform?* 


We anticipate that the mostly tunnel character of the subway line is the source of aerosol nanoparticles of various origin. Their spread (release) is probably caused by pressure and impulse waves created by the running subway trains.

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430 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

**Figure 17.** Distribution of particles during the passage of the servicing locomotive

*What are the supposed sources of nanoparticles on the subway station platform?* 

influences the quantity of nanoparticles on the subway platform.

crossties, subbase and by technical operations (servicing technology).

changing numbers of persons in the station.

impulse waves created by the running subway trains.

etc.

a. Supply of the outdoor air via a vent shaft (see Figure 18) into the tunnel premises in the platform proximity: In winter the ventilation air is supplied into the subway from the ground level into the tunnel premises via a vent shaft. In this case the vent shaft is situated in a very close proximity to a busy road (Prague arterial road), where the level of traffic is a "slow moving traffic jam". The traffic on the arterial road probably

b. Release of previously deposited nanoparticles from the tunnel premises: The increased concentration of nanoparticles is probably also influenced by pressure waves caused by passing trains in the narrowed premises of the tunnels. These may be e.g. nanoparticles generated by wear of the tunnel lining (usually reinforced concrete), wear of the rails,

c. Braking of the trains: Another factor that may influence the measured quantity of nanoparticles is braking of the trains. The weight of a subway train is ca. 130 t and it brakes for several seconds. This braking results in the wear of wheels, brakes, rails,

d. Influence of passengers: During the experiment we attempted to limit this influence to the maximum extent by placing the measuring technology at the end of the platform, but we still anticipate that the measured values might have been influenced by the

We anticipate that the mostly tunnel character of the subway line is the source of aerosol nanoparticles of various origin. Their spread (release) is probably caused by pressure and

This assumption has been confirmed by a comparison of the quantity of measured nanoparticles inside a train car on the subway platform on the line C with the quantity measured in a subway train car during its trip on the line C (see part I). The concentration of nanoparticles in the travelling train car was higher than at the same place measured on the platform. This is probably caused by the ventilation system of the cars which takes in the air from the tunnel premises, plus by the higher concentration of passengers per area unit.
