III. Summer time atmospheric phenomena
Before one can talk about the overall levels of air pollution associated with Moscow it is crucial to consider several atmospheric phenomena that contribute to the current pollution status. Moscow as a large city experiences the effect of the “heat island” where the annual temperatures within the city are usually 1.5-2C higher than those of the suburbs (Stathopoulou et al 2008). This effect is more pronounced in winter, yet in summer it is also observed during the nighttime (Shahgedanova et al 1999).
The heat island effect does not allow for rapid clearing of the atmosphere from the smog and pollutants (Stathopoulou et al 2008). It modifies the temperature progression throughout the layers of the atmosphere above the city and results in temperature inversions as well as temperature stratification. Such stratification prevents air masses with different temperatures from mixing. Thus, the air masses above Moscow stay relatively unmixed with the masses about the suburbs and rural area (Stathopoulou et al 2008). This effect produces a heat “cap” over Moscow. This cap provides a platform for the photochemical smog that is characteristic for Moscow during summer time (Elansky et al 2007; Federal Portal 2010; Gorchakov et al 2006; Mosecomonitoring 2010; Plaude et al 2007). The smog together with weak winds (<2m/s) and heat inversions absorbs the pollutants and expedites reactions between free radicals, pollutants and other harmless compounds. The smog can be dry or wet, where high humidity contributes to the dissolution of hazardous particles in water droplets thus allowing for their enhanced assimilation by living organisms and plants. Some pollutants like PM10 can precipitate from the smog into the sediment and be further washed off by the rainfall into the local water bodies (Federal Portal 2010; Khaikin et al 2006; Shahgedanova et al 1998).
Air masses above Moscow are relatively well cleared by the precipitation in case of regular rainfalls (Mosecomonitoring 2010; Roshydromet 2010). However, past several summers were characterized as very dry with small amounts of precipitation which resulted in heavier smog over the city due to formation of more ozone (O3), NO2, PM10 and other hazardous pollutants discussed further (Plaude et al 2007).
IV. Classification of summer smog pollutants
Table 1. Maximum Permissible Concentrations/Values in mg/m3 (Russian Federation)
(Mosecomonitoring 2010).
Classification of hazard system is based on 4 classes, where 1 is the most hazardous and 4 is the least hazardous substance (Mosecomonitoring 2010). According to Table 1, O3 is the most hazardous substance that occurs in Moscow in high concentrations during summer time.
Figure 4. Comparison of O3 mean monthly values and O3 maximum permissible values
(Lokoshenko and Elansky 2006; Mosecomonitoring 2010; Roshydromet 2010).
Figure 4 represents mean monthly values of O3, where months with the most O3 concentration are April, May and June (Mosecomonitoring 2010; Roshydromet 2010). Thus, O3 is formed most vigorously during the summer months in the Moscow city and is greatly reduced during winter months. Tropospheric ozone has somewhat different properties compared to the stratospheric O3 such as strong oxidant characteristics (Gorchakov et al 2006; Plaude et al 2007; Stathopoulou et al 2008; Zvyagintsev 2008). This type of ozone is detrimental for most living organisms that inhabit the lower layer of the atmosphere given rapid increase in its concentration during summer. Tropospheric ozone shows a strong positive correlation with the increasing temperature and smog formation, where photochemical mechanisms of smog contribute to O3 formation and O3 trapping in the troposphere (Mosecomonitoring 2010; Stathopoulou et al 2008; Zvyagintsev 2008). Additionally, since photochemical smog represents a “blanket” of anthropogenic pollutants such as CO, NO, NO2 and VOCs (OH), these compounds react to the increase in temperature and solar radiation. These parameters stimulate enhanced O3 production through the following reaction that involves solar radiation:
1. CO+OH=H+CO2
2. H+O2=HO2 (peroxy radical)
3. HO2+NO=NO2+OH
4. NO2 =(photolysis)=NO+O
5. O+O2=O3 (Stathopolou et al 2008).
Apart from this mechanism of O3 production, there are two other mechanisms that add up to O3 presence in the atmosphere: emissions from fossil fuel, peat bog and forest burning that are very common in summer for Moscow as well as occasional migration of stratospheric ozone into the troposphere. These emissions are trapped within the troposphere due to the “heat island effect” of urban settlement such as Moscow (Mosecomonitoring 2010; Stathopoulou et al 2008; Zvyagintsev 2008).
According to Figure 5, there is a positive correlation between O3 concentration and solar radiation as well as increasing temperature in case of Moscow (Zvyagintsev 2008). As the temperature rises, the O3 concentrations grow accordingly, yet the O3 concentrations drop before the temperature reaches its maximum in July. This can be explained by a crude generalization of mean monthly temperatures and ozone concentration, where for the period of 2002-2009 there were several very hot and very cold summers.
Figure 5. Positive correlation between the mean monthly temperature fluctuations and
mean monthly O3 concentrations. (Lokoshenko and Elansky 2006;
Mosecomonitoring 2010; Roshydromet 2010; Moscow Climate 2010)
As for the effects of the atmospheric pressure, so far no studies have been produced for the Moscow city. It might be possible, however, that lowering of the atmospheric pressure might result in increased mechanism of stratospheric O3 migration into the troposphere. Additionally, low atmospheric pressure combined with low wind activity might create an additional stimulus for increased O3 formation given the smog presence. These assumptions, however, are not supported by evidence and further research will be needed to investigate the relationship between O3 and atmospheric pressure.
Another substance that has an adverse effect on the rate of O3 formation is aerosols (Elansky et al 2007; Flynn et al 2009; Khaikin et al 2006; Stathopoulou et al 2008; Stulov et al 2010; Zvyaginstev 2008). Specifically, aerosols affect solar radiation by absorbing it and hence reduce the stimulus for O3 to form. Solar radiation is the key component of O3 production, which is more important than the overall composition of the tropospheric pollutants. With reduced solar radiation and therefore more aerosol particulates O3 levels will tend to decrease (Flynn et al 2009).
As for the relationship between the O3 and other meteorological phenomena, it is crucial to mention the temperature stratification and wind patterns that affect the O3 formation and longetivity (Flynn et al 2009; Zvyagintzev 2008). According to the constant temperature inversions that are characteristic for Moscow during summer, the air becomes warmer as it rises up. This effect traps the ozone within the troposphere and prevents it from breakdown (Elansky et al 2007; Federal Portal 2010; Mosecomonitoring 2010). Temperature inversion coupled with slow wind speed (<2m/s) creates a good platform for accumulation of tropospheric O3 for approximately 1-1.5 km up (Flynn et al 2009; Gorchakov et al 2006).
Another important pollutant that is directly related to the O3 production is nitrogen dioxide (NO2) (Gorchakov et al 2006; Ionov and Timofeev 2009; Shaghedanova et al 1999). According to Figure 6, the mean monthly concentrations of NO2 breached the threshold limit during the months of November and December, where the maximum permissible value was around 1- 1.1 (Lokoshenko and Elansky 2006; Mosecomonitoring 2010; Roshydromet 2010). This jump during winter months can be explained by episodes of low mixing of the tropospheric air and temperature inversions that trap the pollutants. These compounds are produced on a constant basis throughout the year due to increased traffic and high temperature fuel burning engines as well as heat generating power plants, where the latter produces NO only during the cold winter months (Shahgedanova et al 1999). Most power plants that are located within the city of Moscow contribute enormously to the NO2 pollution by smoke stack emissions that coat the urban settlement.
These emissions are usually relatively high throughout the year, where the increase in NO during winter is balanced off by the increase in NO2 formation during spring and summer due to photochemical reactions (Gorchakov et al 2006; Ionov and Timofeev 2009; Shaghedanova et al 1999). Both NO2 and NO result from the engine emissions from automobile transportation, where the applied measures of installing the so-called “neutralizers” to control the exhaust composition do not effectively separate these compounds. In fact, summer emissions of NO usually exceed those of NO2 during the daily traffic rush hour (Federal Portal 2010; Gorchakov et al 2006; Ionov and Timofeev 2009; Mosecomonitoring 2010).
Figure 6. Comparison between NO2 monthly values and NO2 maximum permissible value (Lokoshenko and Elansky 2006; Mosecomoritoring 2010; Roshydromet 2010)
According to the recent studies, the highest values of NO and NO2 are recorded around highways and large roads within Moscow (Ionov and Timofeev 2009; Mosecomonitoring 2010; Roshydromet 2010). These values often exceed maximum permissible values, yet they are rapidly diffused over the city due to the winds or natural precipitation. Compared to the municipal areas where the values for these compounds are relatively low, their concentrations around large roads often breach the threshold value throughout the year. Traffic density in Moscow is overall very dense with minor variation in summer, when most of the population drives to the countryside for leisure. This, however, does not result in significant reduction of NO2 concentration due to the smog issues (Gorchakov et al 2006; Mosecomonitoring 2010; Roshydromet 2010).
Dense traffic also contributes to the CO emissions (Elansky et al 2007; Shahdedanova et al 1999). These numbers are not as high as O3 or NO2, yet this compound is very hazardous and has to be closely monitored in order to prevent major health issues associated with it. CO concentrations in Moscow are relatively low compared to other large cities, yet they are still constantly emitted by traffic and peat bog and forest fires (Mosecomonitoring 2010; Plaude et al 2007; Roshydromet 2010). There is a peak associated with increased CO concentration around 7-10 am daily throughout the late summer period which is associated with the morning rush hour (Moecomonitoring 2010; Shahgedanova et al 1999).
Figure 7. Comparison of CO mean monthly values and CO maximum permissible value
(Lokoshenko and Elansky 2006; Mosecomonitoring 2010; Roshydromet 2010)
According to Figure 7, the CO increases during March and July-early September, where the latter values pertain to the natural fires coupled with the traffic emissions. The peak in March could be caused by several episodes of little natural atmospheric precipitation, which resulted in cumulative aggregation of CO emissions (Mosecomonitoring 2010; Roshydromet 2010). According to Mosecomonitoring and Roshydromet, the overall CO concentrations, however, did not show a significant increase over the past decade. Moscow officials relate this phenomenon to the improved quality of car fleet and gas production techniques. At the same time, the claimed efficiency of car engines contributes to the overall NO and NO2 emissions, which are also very hazardous for human health in large concentrations (Elansky et al 2007; Mosecomonitoring 2010; Roshydromet 2010).
Finally, there are aerosols and specifically PM10 particles, which usually show a concentration increase of up to 15% during summer time (Federal Portal 2010; Mosecomonitoring 2010).
Figure 8. Comparison of PM10 mean monthly values and PM10 maximum permissible
value (Mosecomonitoring 2010; Roshydromet 2010; MSU?)
Figure 8 shows a huge difference of the observed PM10 concentration from the maximum permissible value, yet both Mosecomonitoring and Roshydromet observed a gradual increase in PM10 concentrations for the years 2007 (0.034mg/m3), 2008 and 2009 (0.038mg/m3) by approximately 2-5% (Khaikin et al 2006; Mosecomonitoring 2010). These particles express higher concentration values closer to the industrial sites and highways due to their nature. Their concentration in the air strongly depends on the precipitation patterns, where heavy rainfalls result in PM10 sedimentation (Elansky et al 2007).
Last but not least, it is crucial to mentions such substances as benzopyrene, formaldehyde and phenol that express significant increase during Moscow summers, especially during the peat bog and forest fires around Moscow (Mosecomonitoring 2010; Lezina 2010; Roshydromet 2010). For example, summer 2010 was characterized as almost two-month heavy smog over the Moscow city, where several daily values of phenol constituted about 0.135 mg/m3 (maximum permissible daily value 0.003mg/m3) and formaldehyde – 0,250 mg/m3 (maximum permissible daily value 0.003mg/m3) (Lezina 2010; Moscecomonitoring 2009). Most of the monitoring stations measure just these two compounds and not benzopyrene, which is also crucial for assessing the overall atmospheric pollution of Moscow. All in all, the credibility of these numbers is imperative for understanding the potential health impacts associated with the above-mentioned pollutants.
VI. Medical implications
So far we have discussed the following pollutants that are crucial in assessing the atmospheric pollution in Moscow city: O3, NO2, CO, PM10, formaldehyde and phenol.
If the maximum permissible values are exceeded for these pollutants, each one of them will have a special adverse effect on the health system of a human. For example, NO2 targets the lungs and can lead to various chronic and acute lung diseases depending on its concentration in the atmosphere. This is crucial for those affected by bronchitis or asthma (Ionov and Timofeev 2009; Mosecomonioring 2010; Shahgedanova et al 1999).
CO mimics the hemoglobin structure and prevents the red blood cells from collecting oxygen, which could be lethal. Formaldehyde can cause allergies and in large concentrations in can lead to asthma (EPA 2011a).
PM10 due to their size can reach the lungs through inhalation and penetrate into the cardiovascular system leading to associated diseases and even death due to poisoning (Khaikin et al 2006).
As for O3 it is uncertain as to whether it causes long-term damages to the respiratory system, yet its acute effects involve coughing, irritation and potentially asthma (EPA 2011b). All of these pollutants show damaging effects on heart and central nervous system, which could lead to irreversible damages if a person is exposed to toxic chemicals for too long. Also, there is a high risk that these substances might be carcinogenic (EPA 2011a; EPA 2011b).
Thus, the two episodes of severe smog events that were observed in Moscow during 2002 and 2010 could have a major damaging impact on Muscovites’ immune system overall. As for the age group of 75+, the statistics are needed to be gathered in order to show whether mortality rates and disease outbreaks are related with the heavy smog events. Further studies will need to be carried out in order to assess the level of damage that these events might have caused.
VII. Recommendations
The main recommendation is to check the credibility of the available Mosecomonitoring and Roshydromet data as well as calibrate the monitoring stations in order to have replicable data. This is crucial for atmospheric research since a large variation of data will result in misinterpretation of the current situation of overall pollution and mislead the decision-makers. Also, it would be necessary to gather statistical data on health impacts of the smog events, monitor the amount of calls to the hospitals and assess the general health of the newborns after this summer of 2010 in order to establish a magnitude of health damage produced by smog effects.
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