Экологические и метеорологические проблемы больших городов и промышленных зон

R.H. Turgumbayeva

 

The Kazakh National Pedagogical University named after Abai,

The Republic of Kazakhstan

 

Аtmospheric dispersion of nitrogen dioxide emissions of industry interprise on unfavourable weather conditions

 

 

The pollution of environment by industrial wastes causing degradation of habitats remains to be a nagging ecological problem of essential social and economic importance.

The variety of the chemical plants production, of the technologies applied, and of the raw materials used determines the wide range of the environmental pollutants.

Each day the plants emits a significant amount of dust, gaseous sulphur dioxide, nitrogen dioxide and other admixtures [1]. Nevertheless, enhanced concentrations of these substances in the air streams not permanently [2]. It is the result of the air flows impact on dispersion and removal of the emissions out of the city. However, unfavorable directions of wind result in increase of toxic substances content in the air.

Fig.1 demonstrates concentrations for nitrogen dioxide at the wind velocity of 1 and 2 m/s.

Velocity increase from 1 to 2 m/s decreases the total concentration of nitrogen dioxide.

 

 

Fig.1 - NO2 concentration in dependence on wind direction. 1- wind velocity 1 m/s; 2 – 2m/s.

 

For nitrogen dioxide at any direction of wind concentration in most cases exceeds the average daily maximum permissible concentration (MPC) emission (0.04 mg/m3), and at south-west directions exceeds the (MPC) value (0.085 mg/m3 ) of a maximum single emission ,which is exceeded 1.2 -1.4 times, and average daily – 2.5 -3 times.

The information on the concentration field of dispersed substances in the direction casing pollution of the residential area as well as in the direction perpendicular to the flow of removal is required for studies of polluting substances dispersion in the atmosphere.

Prior to the studies the coordinates of the points of environmental components sampling were determined on the map with respect to the conventional center of organized sources of pollutants.

With the aim of calculations convenience and pollution evaluation the direction of axis x was aligned with the wind direction prevailing in the area studied and causing pollution of air in сity by the emissions of chemical enterprise.

Nitrogen dioxide distribution shown in Fig.2 demonstrates, that in the area of industrial wastes storages location nitrogen dioxide concentration is 0.02 mg/m3 at calm, and in the area of gypsum producing plant - 0.01 mg/m3, that does not exceed average daily MPC (0.04 mg/m3) whereas at point №1 in city it exceeds both average daily MPC 1.25 -2.5 times and maximum single MPC  (0.085 mg/m3), reaching 0.1 mg/m3 .

 

Fig 2 - Concentration of nitrogen dioxide at different distances from the source of emission at wind velocity: 0 – calm; 1 – wind velocity 1 m/s; 2 – wind velocity 2 m/s.

 

At wind velocity 1-2 m/s in observation point of pollution №1 nitrogen dioxide concentration also exceeds average daily emission, approaching to the single emission maximum (0,085 mg/m3).

Evaluation of the pollutants diffusion in the direction perpendicular to the flow of polluting substances drift presented an interesting task. Such information can be obtained in the course of large-scale under-torch observations, when sampling is made in the points, located perpendicular to the stream direction at various distances from the source [3], and thus, transverse pollutants diffusion can be evaluated.

As such information was not available for the studied area, it was interesting to evaluate polluting agents diffusion in the direction perpendicular to the stream of their spread using the data of observation stations and obtain the information on substances concentration in respect not only to the source of pollution but to the torch axis as well.

The given figure demonstrates NO2 concentrations at different distances from the torch axis.

The distribution of NO2  is rather even, approaching to Gaussian distribution and exceeds average daily MCL (0.04 mg/m3) in each point of observations: in the area of the farm – 3 times (0.12 mg/m3),  ancillary farm - -3.5 times (0.14 mg/m3), gypsum manufacturing plant -2.25 times (0.09 mg/m3), wastes storage – 4 –fold excess of  single emission MPC. In the area of the wastes storage NO2 concentration makes 0.16 mg/m3 and the result is its concentration excess in the area of the ancillary farm as well, where it reaches 0.14 mg/m3, that 1.65 times exceeds single emission MPC (0,085 mg/m3). The data presented here demonstrate the enhanced negative impact of nitrogen dioxide emissions on the state of the atmosphere in the area of the farm and in the area of agricultural production.

 

 

 

Fig.3 - Concentrations at different distances of nitrogen dioxide from the torch axis at the wind velocities: 0 – calm; 1 – wind velocity 1 m/s; 2 – wind velocity 2 m/s.

 

The distribution of NO2 is rather even and approaches to Gaussian distribution.

The analysis of the nitrogen dioxide dependence on the distance from the torch axis allows evaluation of the scale of transverse turbulent diffusion.

The hypothesis of the nitrogen dioxide impact on the pollution of the city in conditions of north-west and north wind directions causing contamination of the air in city has been proved.

The obtained dependences of nitrogen dioxide concentrations on wind directions for the values of velocities from calm to 2 m/s have shown, that the highest pollution of the city air occurs at calm (0.04 mg/m3), the pollution is somewhat less at the wind velocity of 1 m/s (0.015- 0.25 mg/m3), and the lowest pollution (0.007 mg/m3) is observed at the velocity of 2m/s.

 

Literature:

1.           Израэль Ю.А.Экология и контроль состояния природной среды. -М.: Гидрометеоиздат, 1984.-355 с.

2.           Омарбекулы Т., Сембина Г.К. Моделирование загрязнения воздуха при неблагоприятных погодных условиях // Вестник КазАТК им. М. Тынышпаева. – Алматы, 2005. – №6. – С. 158-162.

3.     Берлянд М.Е. Прогноз и регулирование загрязнения атмосферы.- Л.: Гидрометеоиздат, 1985.- 272 с.