Mobile Measurement of PM2.5 Based on an Individual in Ulaanbaatar City.

In the present study, we measured fine particulate matter (PM2.5) on the daily route of our study participant in order to determine her exposure and dose of PM2.5 in every microenvironment (ME). The measuring instrument, created by Nagoya University and Panasonic Corporation, Japan, was carried close to the breathing zone most of the time. Each data point was collected for 10–30 s or 2–6 cycles/min for 24 h from 1 October 2018 to 30 December 2018. Public transportation showed the highest level of PM2.5 compared with other MEs, including residence apartments, houses (ger district), the National University of Mongolia (NUM), food courts or restaurants, and other indoor locations. The personal daily average exposure to PM2.5 was 35 µg/m3 on 4 November 2018; on the other hand, this value was evaluated as the highest level of exposure compared to other measurement days. Interestingly, the study participant‘s exposure and dose of PM2.5 was lower than those stated in the World Health Organization (WHO) air quality guidelines, with 25 µg/m3 from 4:00 to 7:00.


Introduction
According to the global ranking of mortality risk factors, air pollution is the fifth highest risk factor and ranks higher than well-known hazardous components, such as alcohol use, occupational risk, and physical inactivity [1]. The World Health Organization (WHO) announced that nine out of 10 people breathe air containing a high level of pollutants [2,3]. The diameter of PM 2.5 , one of the major pollutants of air pollution, is less than 2.5 micrometres; however, it is capable of carrying various toxic materials. When humans breathe, PM 2.5 enters the human body through air exchange and reaches the ends of the pulmonary alveoli, thereby damaging other parts of the body [4,5]. Primary sources of PM 2.5 can be incomplete fuel combustion, biomass burning, vehicle exhaust, residential cooking, and bioaerosols [6]. The adverse effects of combustion-related air pollution are premature death, pulmonary diseases, including asthma, and an increased risk of developing cancer [7][8][9]. Alexander Millman (2008) from Columbia University suggests that PM 2.5 causes micro-inflammation to a newborn's brain [10].
The average daily temperature in Ulaanbaatar (UB), the capital city of Mongolia, is around −13 • C and sometimes reaches temperatures as low as −40 • C at night in the winter [11]. As of 2010, the population of UB was 1.24 million, but the number grew to 1.50 million by 2018 [12]. This population growth has led to major increases in the city's air pollution emissions, as 53% of UB citizens live in the ger (the traditional Mongolian dwelling) areas, where coal and other flammable fuels are used for their heating systems [13]. The Mongolian National Agency for Meteorology and Environment Monitoring reports that, in 2017, in the wintertime, the mean concentration of particulate matter for the Figure 2 displays the instrument designed by Nagoya University and Panasonic Corporation, Japan. The monitoring pack-the PM 2.5 sensor-was strapped onto the study participant's shoulder in a bag around her breathing height. The size was 52 × 45 × 22 mm, the PM 2.5 concentration was determined by the distribution of the light-scattering technology, and the fine particle content was directly expressed in µg/m 3 . The validation of the PM 2.5 sensor was carried out with beta attenuation monitoring (BAM) instruments (Thermo Fisher, SHARP 5030, DKK-TOA, model FPM-377, and Kimoto, model PM-712) at four urban and suburban sites in Fukuoka, Kadoma, Kasugai, and Tokyo, and the correlation factors were 0.87, 0.86, 0.86, and 0.89, respectively. For calibration, the PM 2.5 mass concentration was calculated using the particle size of monodisperse polystyrene latex (PSL) and the particle number density measured with the condensation particle counter (CPC, TSI, model 3772). As an example of the results, the concentrations of PSL particles with diameters of 0.296 and 0.498 mm measured by the CPC were approximately 17 and 13 particles/cm 3 , respectively. The linearity of the sensor was tested using cigarette smoke particles. A test room (31 m 3 ) with ten PM 2.5 sensors and a digital dust monitor (Shibata, model LD-3B) was filled with cigarette smoke because there is no clear difference between the density of PSL particles (1.05 g/cm 3 ) and the typical densities of cigarette smoke particles (1.0-1.3 g/cm 3 ) [30]. One of the study areas was the building of the National University of Mongolia (NUM), which is located in the center of the city. Another study area was a participant's apartment (home 1) located 1 km away from the NUM. However, in mid-October, the participant moved to a campsite (home 2), 13 km away from the NUM (Figure 1).

Study Object
A researcher (a full-time student) from the NUM cooperated as a participant in this study. According to the study, students who are enrolled at a university or a college spend 3.50 hours per day in class and partaking in education-related activities [29]. The study object spent approximately 7.90 hours at the NUM every single day from October to December 2018. One of the study areas was the building of the National University of Mongolia (NUM), which is located in the center of the city. Another study area was a participant's apartment (home 1) located 1 km away from the NUM. However, in mid-October, the participant moved to a campsite (home 2), 13 km away from the NUM (Figure 1).

Study Object
A researcher (a full-time student) from the NUM cooperated as a participant in this study. According to the study, students who are enrolled at a university or a college spend 3.50 hours per day in class and partaking in education-related activities [29]. The study object spent approximately 7.90 hours at the NUM every single day from October to December 2018.  On a full power bank, the PM 2.5 runs for approximately 2-3 days. Furthermore, the built-in memory is able to store the data for around one year when continuously sampling logs every ten seconds per minute. The data for 8-10 days for 24 h per day were collected for each month.

Data Collection, Extraction, and Processing
The sensor collected data from 1 October 2018, to 31 December 2018, and measured close to breathing height ( Figure 3). The data were recorded at intervals of 10-30 s. We calculated descriptive indications, such as the minimum value, mean, median, and maximum value of the collected data. We chose days from every measured months that can represent the daily average exposure. One of the chosen days consisted of the ordinary route, and the other day consisted of a number of the microenvironments. Additionally, some statistical analyses, such as standard deviation, variance, coefficient variance, average, and median values, analyzed the result of every microenvironment (home/house, NUM, means of transportation, restaurant, pub, bar, and sports hall). where Tme/ma is the time spent in each microenvironment/macro activity (h/day), Came is the air concentration in a microenvironment (µg/m 3 ), and IRma is the inhalation rate during each macroactivity (m 3 /h).   The PM2.5 concentration decreased between 0:00 and 9:10 on 4 October 2018 ( Figure 4). The study participant went to the NUM from home between 9:10 and 9:30. The highest concentration of the day was 230 µg/m 3 , which is 9.2 times higher than stated in the WHO air quality guidelines (25 µg/m 3 24hour mean) [36] due to the fact that the study object walked near the road where a street-sweeper

Data Analysis
We determined the PM 2.5 concentration with the participant's breath. The day-night exposure and total exposure of the participant's daily route were calculated. There were two reasons to divide exposures into day and night.
The inhalation rate when sleeping is six times less than that in normal breathing. Therefore, the amount of PM 2.5 in the human body decreases, and thus the study participant was assumed to be asleep during the night time [31].
According to the study, men and women between the ages of 16 and up to the age of 21 breathe 16.3 m 3 air per day [31]. Generally, the human inhalation rate is 16.3 m 3 /day. Consequently, the daytime inhalation rate is 0.873 m 3 /h and the night-time inhalation rate is 0.295 m 3 /h.
For the inhalation process, the exposure was estimated for each of the microenvironments in which the participant spent time and each macroactivity that would result in a different inhalation rate while engaging in that activity (Equation (1)). The exposure for 24 h was the sum of the microenvironment/macroactivity (me/ma) exposure. For each me/ma exposure, the inhalation exposure for 24 h (E me/ma ) was defined [33][34][35].
where T me/ma is the time spent in each microenvironment/macro activity (h/day), C ame is the air concentration in a microenvironment (µg/m 3 ), and IRma is the inhalation rate during each macroactivity (m 3 /h). Figure 3 shows the amount of PM 2.5 determined by the descriptive parameters, such as the maximum, average, median, and mean values in October 2018. On 19 October, the PM 2.5 concentration reached 420 µg/m 3 , which was the highest number that month. The daily routes of the month are represented on 4 October 2018, while 9 October represents different routes and various means of transportation compared with other days.

PM 2.5 Concentration in the Wintertime
The PM 2.5 concentration decreased between 0:00 and 9:10 on 4 October 2018 ( Figure 4). The study participant went to the NUM from home between 9:10 and 9:30. The highest concentration of the day was 230 µg/m 3 , which is 9.2 times higher than stated in the WHO air quality guidelines (25 µg/m 3 24-h mean) [36] due to the fact that the study object walked near the road where a street-sweeper swept up particles of dust. The level of PM 2.5 fluctuated from 20 to 40 µg/m 3 at the NUM from 13:10 to 13:50 while the study participant was outdoors around the NUM. However, from the NUM to home, the PM 2.5 concentration was in a range of 10 to 36 µg/m 3 from 19:30 to 19:50.   The PM2.5 concentration decreased between 0:00 and 9:10 on 4 October 2018 ( Figure 4). The study participant went to the NUM from home between 9:10 and 9:30. The highest concentration of the day was 230 µg/m 3 , which is 9.2 times higher than stated in the WHO air quality guidelines (25 µg/m 3 24hour mean) [36] due to the fact that the study object walked near the road where a street-sweeper  4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 21 22 23 24 29   In Figure 5, from 0:00 to 8:40, the PM 2.5 concentration was 7-37 µg/m 3 at home on 9 October 2018. The study participant travelled to Modnii-2 (5 km away from the NUM to the west) by bus from 8:40 to 9:20 and then back home. At that time, the PM 2.5 concentration increased by 20-40 µg/m 3 . The maximum amount during the day was 145 µg/m 3 , which occurred from 11:00 to 11:15, when the participant went from home to the NUM library; this is 5.80 times higher than that suggested by the WHO air quality guidelines. Thereafter, the PM 2.5 concentration decreased slowly. From 15.40 to 16.20, the green color indicates an outdoor locality where the Music and Dance College of Mongolia is located (600 m far away from NUM). After that, the participant went to Modnii-2 (an apartment complex, 5 km away from NUM) and back home by bus. Some windows were opened on the bus; therefore, the PM 2.5 concentration ranged from 11 to 130 µg/m 3 . From 19:50 to 20:20 around the shopping center or E-Mart (1 km away from the NUM to the east), the concentration of PM 2.5 reached 69 µg/m 3 , which is 1.40 times higher than that suggested by the WHO air quality guidelines.

PM2.5 Concentration in the Wintertime
swept up particles of dust. The level of PM2.5 fluctuated from 20 to 40 µg/m 3 at the NUM from 13:10 to 13:50 while the study participant was outdoors around the NUM. However, from the NUM to home, the PM2.5concentration was in a range of 10 to 36 µg/m 3 from 19:30 to 19:50. In Figure 5, from 0:00 to 8:40, the PM2.5 concentration was 7-37 µg/m 3 at home on 9 October 2018. The study participant travelled to Modnii-2 (5 km away from the NUM to the west) by bus from 8:40 to 9:20 and then back home. At that time, the PM2.5 concentration increased by 20-40 µg/m 3 . The maximum amount during the day was 145 µg/m 3 , which occurred from 11:00 to 11:15, when the participant went from home to the NUM library; this is 5.80 times higher than that suggested by the WHO air quality guidelines. Thereafter, the PM2.5 concentration decreased slowly. From 15.40 to 16.20, the green color indicates an outdoor locality where the Music and Dance College of Mongolia is located (600 m far away from NUM). After that, the participant went to Modnii-2 (an apartment complex, 5 km away from NUM) and back home by bus. Some windows were opened on the bus; therefore, the PM2.5 concentration ranged from 11 to 130 µg/m 3 . From 19:50 to 20:20 around the shopping center or E-Mart (1 km away from the NUM to the east), the concentration of PM2.5 reached 69 µg/m 3 , which is 1.40 times higher than that suggested by the WHO air quality guidelines.     In Figure 5, from 0:00 to 8:40, the PM2.5 concentration was 7-37 µg/m 3 at home on 9 October 2018. The study participant travelled to Modnii-2 (5 km away from the NUM to the west) by bus from 8:40 to 9:20 and then back home. At that time, the PM2.5 concentration increased by 20-40 µg/m 3 . The maximum amount during the day was 145 µg/m 3 , which occurred from 11:00 to 11:15, when the participant went from home to the NUM library; this is 5.80 times higher than that suggested by the WHO air quality guidelines. Thereafter, the PM2.5 concentration decreased slowly. From 15.40 to 16.20, the green color indicates an outdoor locality where the Music and Dance College of Mongolia is located (600 m far away from NUM). After that, the participant went to Modnii-2 (an apartment complex, 5 km away from NUM) and back home by bus. Some windows were opened on the bus; therefore, the PM2.5 concentration ranged from 11 to 130 µg/m 3 . From 19:50 to 20:20 around the shopping center or E-Mart (1 km away from the NUM to the east), the concentration of PM2.5 reached 69 µg/m 3 , which is 1.40 times higher than that suggested by the WHO air quality guidelines.   As shown in Figure 7, the PM 2.5 concentration was relatively stable until 7:40 on 4 November 2018. After that, the PM 2.5 concentration sharply increased because the study participant wiped off a table near the measuring instrument in the house. The maximum level of PM 2.5 was 287 µg/m 3 , which is 11.40 times higher than that suggested by the WHO air quality guidelines. The participant travelled from the house to Hunsnii-4 (750 m away from NUM to the north) from 10:35 to 11:20 by bus and then travelled to the NUM by car until 12:30. The PM 2.5 concentration fluctuated from 13 to 77 µg/m 3 from 12:40 to 19:00 at the sports center of the school (a bus stop, 1.3. km away from NUM to the north). Interestingly, the PM 2.5 concentration reached 225 µg/m 3 while the participant walked to the NUM from the sports center for 15 min. After that, the participant waited for the bus between 20:10 and 20:20 at the shopping center, where the PM 2.5 concentration measured over 72-100 µg/m 3 . Figure 6 illustrates that all measurements of PM2.5 were defined by the maximum, average, median, and mean values in November 2018. On 18 November, the PM2.5 concentration reached 936 µg/m 3 , which is 37.40 times higher than that suggested by the WHO air quality guidelines. Moreover, that was the highest measurement of the month. The day of 4 November 2018 chosen due to the sports center, while 11 November 2018 represents the daily route of a study participant.    The blue color represents the PM 2.5 concentration in the house, as shown in Figure 8. At 8:35, the participant sprayed an air freshener near the measuring instrument. Therefore, the PM 2.5 concentration strongly increased and reached 283 µg/m 3 , which is 11.40 times higher than that suggested by the WHO air quality guidelines. For that reason, this was the highest value of the day. The participant traveled to the NUM from the house from 9:30 to 10:40 by bus. She stayed at the NUM until 18:20, where the PM 2.5 concentration was below the air quality standard. From 18:30 to 19:00, the participant traveled back to the house from the NUM by public transport. From 20:30 on this day, the concentration of PM 2.5 was 50 µg/m 3 at the house. Figure 6 illustrates that all measurements of PM2.5 were defined by the maximum, average, median, and mean values in November 2018. On 18 November, the PM2.5 concentration reached 936 µg/m 3 , which is 37.40 times higher than that suggested by the WHO air quality guidelines. Moreover, that was the highest measurement of the month. The day of 4 November 2018 chosen due to the sports center, while 11 November 2018 represents the daily route of a study participant.    As shown in Figure 9, in December 2018, the amount of PM 2.5 was determined by the maximum, average, median, and mean values of descriptive parameters. On 20 December, 2018, the PM 2.5 concentration reached 542 µg/m 3 , which is 20.20 times higher than that suggested by the WHO air quality guidelines. Furthermore, it was the highest level of the month. We display measurements from 4 December 2018.
participant sprayed an air freshener near the measuring instrument. Therefore, the PM2.5 concentration strongly increased and reached 283 µg/m 3 , which is 11.40 times higher than that suggested by the WHO air quality guidelines. For that reason, this was the highest value of the day. The participant traveled to the NUM from the house from 9:30 to 10:40 by bus. She stayed at the NUM until 18:20, where the PM2.5 concentration was below the air quality standard. From 18:30 to 19:00, the participant traveled back to the house from the NUM by public transport. From 20:30 on this day, the concentration of PM2.5 was 50 µg/m 3 at the house. As shown in Figure 9, in December 2018, the amount of PM2.5 was determined by the maximum, average, median, and mean values of descriptive parameters. On 20 December, 2018, the PM2.5 concentration reached 542 µg/m 3 , which is 20.20 times higher than that suggested by the WHO air quality guidelines. Furthermore, it was the highest level of the month. We display measurements from 4 December 2018.   5 6 9 10 11 12 13 14 17 18 20 21 23 24 25 26 27 28    The blue color shows the PM 2.5 concentration in the house from 0:00 to 7:00. From 7:10 to 7:35, the PM 2.5 concentration was 343 µg/m 3 , which means it was 13.60 times higher than that suggested by the WHO air quality guidelines. Meanwhile, these numbers were identified as being the highest level of the day. Generally, the PM 2.5 concentration in the NUM was higher than on the other chosen days. At the food court (400 m away from the NUM to the northeast), the level of PM 2.5 ranged from 49 to 70 µg/m 3 . From 12:00 to 15:20, the study participant traveled to Tasganii Ovoo (the ger district, 2 km away from the NUM to the northeast), Naiman Sharga (1.40 km away from the NUM to the east), Tasganii Ovoo, and back to the NUM by car. The participant walked around the NUM while the concentration of PM 2.5 was above the WHO air quality guidelines. After that, the concentration of PM 2.5 fluctuated between 28 and 90 µg/m 3 when the study participant returned home by bus. The blue color represents the PM2.5 concentration in the house, as shown in Figure 8. At 8:35, the participant sprayed an air freshener near the measuring instrument. Therefore, the PM2.5 concentration strongly increased and reached 283 µg/m 3 , which is 11.40 times higher than that suggested by the WHO air quality guidelines. For that reason, this was the highest value of the day. The participant traveled to the NUM from the house from 9:30 to 10:40 by bus. She stayed at the NUM until 18:20, where the PM2.5 concentration was below the air quality standard. From 18:30 to 19:00, the participant traveled back to the house from the NUM by public transport. From 20:30 on this day, the concentration of PM2.5 was 50 µg/m 3 at the house. As shown in Figure 9, in December 2018, the amount of PM2.5 was determined by the maximum, average, median, and mean values of descriptive parameters. On 20 December, 2018, the PM2.5 concentration reached 542 µg/m 3 , which is 20.20 times higher than that suggested by the WHO air quality guidelines. Furthermore, it was the highest level of the month. We display measurements from 4 December 2018.   4 5 6 9 10 11 12 13 14 17 18 20 21 23 24 25 26 27 28   From 0:00 to 7:50, on 20 December 2018, the PM 2.5 concentration at the house is indicated by the blue color (shown in Figure 11). Between 8:50 and 9:00, while the participant was waiting for the bus at the bus stop, the measurement of PM 2.5 reached 542 µg/m 3 , which is 20.20 times higher than that recommended by the WHO air quality guidelines, and this was the highest result of the day. The participant was in the lecture room from 9:20 to 14:20. From 14:40 to 15:00, the participant visited the food court near the NUM where the PM 2.5 concentration reached 100 µg/m 3 , which is 2 times higher than the air quality standard.
Int. J. Environ. Res. Public Health 2020, 17, x 9 of 16 µg/m 3 , which means it was 13.60 times higher than that suggested by the WHO air quality guidelines. Meanwhile, these numbers were identified as being the highest level of the day. Generally, the PM2.5 concentration in the NUM was higher than on the other chosen days. At the food court (400 m away from the NUM to the northeast), the level of PM2.5 ranged from 49 to 70 µg/m 3 . From 12:00 to 15:20, the study participant traveled to Tasganii Ovoo (the ger district, 2 km away from the NUM to the northeast), Naiman Sharga (1.40 km away from the NUM to the east), Tasganii Ovoo, and back to the NUM by car. The participant walked around the NUM while the concentration of PM2.5 was above the WHO air quality guidelines. After that, the concentration of PM2.5 fluctuated between 28 and 90 µg/m 3 when the study participant returned home by bus. From 0:00 to 7:50, on 20 December 2018, the PM2.5 concentration at the house is indicated by the blue color (shown in Figure 11). Between 8:50 and 9:00, while the participant was waiting for the bus at the bus stop, the measurement of PM2.5 reached 542 µg/m 3 , which is 20.20 times higher than that recommended by the WHO air quality guidelines, and this was the highest result of the day. The participant was in the lecture room from 9:20 to 14:20. From 14:40 to 15:00, the participant visited the food court near the NUM where the PM2.5 concentration reached 100 µg/m 3 , which is 2 times higher than the air quality standard.  As shown in Table 1, the PM 2.5 level on public transportion was higher than in other microenvironments, while the PM 2.5 level at the karaoke bar was the lowest. The average dose experienced by the participant for one hour or less on the selected days from every microenvironment (ME) is shown in Table 2. This table shows how high the PM 2.5 dose that the participant received from each ME at the same time per hour. In this regard, the study participant received the maximum dose of PM 2.5 on her body from outdoor locations and transportation.

PM 2.5 Concentration in Various Microenvironments
The personal exposure from each microenvironment depended on the participant's length of exposure, location, and other activities. The PM 2.5 concentration in the home/house increased during cleaning and cooking activities [38][39][40][41]. The house was a new building and also displayed higher PM 2.5 measurements. The average concentration of PM 2.5 at the NUM was 26.04 ± 33.98 µg/m 3 . Furthermore, the fine particles in outdoor and indoor locations of the NUM were classified as "very strong positive" (r = 0.83) [42].
Restaurants and public transportation had the highest PM 2.5 concentration values. We assumed that the restaurant included a fast-food restaurant, food court, and a non-smoking bar, where the frying and roasting of foods was the reason for an intensified PM 2.5 concentration. There are 1135 public means of transportion in UB, of which 135 are 12-year-old buses and 527 are 11-year-old buses [12]. Figure 12 illustrates the study participant's route to the house from the NUM on 11 November, 2018. The air quality index is shown to aid in the understanding of what the local air quality means to human health. To make it easier to understand, the air quality index is divided into six levels of health concern in Mongolia ( Table 4).

Time-activity Pattern of the Participant.
For the study, the participant spent 89.01% of her time indoors and four major microenvironments were classified: (1) home/house, (2) the NUM, (3) the restaurant, and (4) other indoor locations. The most time was spent at the home/house, which represented 54.09% (631 hours 7 minutes) of the entire study period. According to the study results, the participant spent 10.18 hours per day at home. The NUM was the next major indoor location, which made up 33.33% of the day. Lastly, 1.95% of the time was spent in the restaurant and other indoor places from 1 October 2018 to 31 December 2018. However, the study participant spent 5.90% of her time on modes of transportation. The PM2.5 concentration of the restaurant was higher than that of other microenvironments, but the time spent there was shorter than for other indoor locations. On the other hand, the PM2.5 transportation level was lower than that of restaurants, while the time spent there was longer than around 1.15 hours per day. Therefore, public transit will become an important issue.

Time-Activity Pattern of the Participant
For the study, the participant spent 89.01% of her time indoors and four major microenvironments were classified: (1) home/house, (2) the NUM, (3) the restaurant, and (4) other indoor locations. The most time was spent at the home/house, which represented 54.09% (631 h 7 min) of the entire study period. According to the study results, the participant spent 10.18 h per day at home. The NUM was the next major indoor location, which made up 33.33% of the day. Lastly, 1.95% of the time was spent in the restaurant and other indoor places from 1 October 2018 to 31 December 2018. However, the study participant spent 5.90% of her time on modes of transportation. The PM 2.5 concentration of the restaurant was higher than that of other microenvironments, but the time spent there was shorter than for other indoor locations. On the other hand, the PM 2.5 transportation level was lower than that of restaurants, while the time spent there was longer than around 1.15 h per day. Therefore, public transit will become an important issue.

Study Limitations
This study involved one participant and we determined her individual exposure, microenvironment, and time-activity pattern by a measuring instrument. Although this study is based on one full-time student, the collected data are being considered sufficient for analysis, comparison, and calculation. Additionally, the data collection was interrupted in some cases when the measuring tool was temporarily used in another study or when the power bank was being charged.

Conclusions
Within this study, we determined the PM 2.5 concentration in different microenvironments and determined individual exposure values. The study included the following: We estimated the exposure of PM 2.5 for selected days. The maximum level of exposure occurred on 4 November 2018. According to the measurements of the day, the participant inhaled the maximum amount of PM 2.5 from 09:00 to 11:00; 3.
The PM 2.5 concentration increased because of traffic congestion and burning coal at the time of starting and finishing work. In addition, the fact that road and the street are swept at that time is another reason behind the increasing concentration of PM 2.5 . In order to diminish individual exposure and reduce the conjunction of events, the street or road should be swept at another time.
Author Contributions: A.A. and S.C. designed and participated in the field research of the study. S.C., A.A., and Y.M. were responsible for the research design and analysis. A.A. and S.C. wrote the paper. All authors contributed to editing and reviewing of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding:
The research has received funding from the National University of Mongolia under grant agreement P2019-3727 and was funded by the Ministry of Education, Culture, Science, and Sport, the Mongolian Foundation for Science and Technology (SSA/2020).