Vehicle Emissions Control

Through emissions of nitrogen oxides, cars and other road vehicles are major contributors to acidic emissions which cause acid rain. In all countries of the industrialized world, the number of vehicles on the roads has been continually increasing since the 1970^s.

With a large rise in traffic numbers, it becomes increasingly important to keep pollutant emissions to a minimum. There are presently a number of ways in which road traffic pollution can be reduced, including the use of emission control technology solutions.

Since January 1993, all new cars sold in the European Union have been fitted with a catalytic converter. Most catalytic converters lead to a dramatic reduction in emissions of nitrogen oxides, as well as other harmful pollutants.

Exhaust Gas recirculation involves returning exhaust air to the fuel inlet, which results in a reduction in peak engine temperatures and emissions of nitrogen oxides from petrol vehicles.

Smaller, lighter cars use less fuel and hence produce less pollution. Technological development using lighter materials for construction may therefore reduce emissions.

The above technologies all provide a reduction in emissions from vehicles. Electric transport is an alternative development that could lead to a large reduction in acidic pollution at ground level, if it became more wide spread. Electric transport produces no emissions at the point of use, although pollution is emitted during the production of electricity from power stations. The main drawback for electric vehicles is the need to recharge batteries. In addition, although they have lower fuel and maintenance costs than petrol and diesel, at present they require a higher capital investment.

The technical fixes such as those outlined above need to be combined with management schemes to reduce traffic in city centers, education to encourage the public to use their cars less, and the further development of alternative fuels that are not harmful to the environment.

Measures for Prevention and Reduction of the Air Pollution

The problem of the atmospheric pollution is very difficult and diversified . It requires

a lot of efforts and means. However, a current state of scientific and technical progress allows to reduce the formation of dangerous substances and to develop measures to prevent pollution.

Preventive measures against the atmospheric air pollution and reduction of harmful premixes can be subdivided into three groups:

1. The improvement of present and the introduction of new technological processes allowing no release of harmful premixes from the source of their origin.

2. The improvement of fuel content , devices , carburation and reduction or elimination of harmful emissions into the atmosphere by means of purification facilities.

3.The prevention of the atmospheric air pollution by means of a rational displacement of sources producing harmful emissions, as well as the enlargement of “green zones”.

Among measures directed against the atmospheric air pollution an important place is given to the development of new production technologies and engines, to hermetization of equipment - a source of harmful constituents, to purification of the flue and ventilation gases, to the development of more effective combustion methods , to the substitution of solid and liquid fuels by a natural gas, to creating automobile engines of new types.

One of the principal ways to reduce gas pollution is to improve gas-dust filters. It should be mentioned that filtrated substances are those highly deficient in the national economy. Solid means are directed to improve the air cleaning devices, and these costs are recovered quickly. The most effective become electric filters, their efficiency comes to 99.9%.

Proper arrangement of sanitary -protective zones plays an important role as a means of the atmospheric protection. Accordingly, enterprises should be located on rising grounds and from the lee of residential areas, constructing green zones between them. Not less than 40% of plants in such areas should be resistant to harmful constituents. The width of “green zones” should be 1000, 500, 300 and 50 m. depending on a degree of harmful effect of constituents and ways of their technological cleaning. It has been stated that in the presence of a sanitary-protective zone the dust level at the distance of 1.5km is double reduced, and sulphur dioxide pollution experienced a 3 times reduction. In Chernobyl after the accident on atomic power station the sanitary protective zone has been significantly enlarged. However, the width of a sanitary protective zone at the gasocondensation complex in Astrakhan is 3 km instead of 20 km as it was deleloped. Here at the distance of 8 km the hydrogen sulfide content in the air was recorded as 243 times more compared to normal. Sulfur anhydride 100 times exceeded the norm. A harmful effect of the Astrakhan complex is felt even in Elista at the distance of 300 km.

The USA prefer to import sulfur not to produce it in the country to avoid the sulfureous gas pollution of the air.

All “dirty” enterprises should be located outside urban areas. It is categorically prohibited to place industrial enterprises of different profile close to each other, for their emissions can interact and produce even more dangerous compounds in the result of photochemical reactions.

To reduce the air pollution originated by motor vechicles, planning of streets and organization of traffic is very important. “Green waves” promote a non-stop traffic within urban territories. The number of automobiles increasing, scientists and engineers of all nations direct their efforts to create engines which release reduced or minimized amount of harmful components into the air. The use of liquefied gas is prominent in this respect. Due to the full fuel combustion motor vehicles release less harmful compounds than those, working on petrol. Creation of electromobiles working on sun energy is quite possible. And now the problem of exhaust gases should be solved by regulating of engines and carburators. Industries produce more “pure” deforced automobile engines, reducing the toxicity of exhaust. At present, the motor vehicles park in Moscow, St.Petersburg and other cities in Russia are supplied with petrol of direct distillation without addition of tetraethyl lead. This significantly reduces poisonous lead compounds in the air.

In fighting the air pollution the important part is given to electrification, gasification and thermofication which are widely used inBelarus.

The use of biological means of plant protection - attractants, (pheromones) and other biopreparations - bacteria, viruses, fungi etc., causing diseases of vermin, instead of chemicals is also of significant importance . The use of phytophags - natural enemies of various vermin, can be also referred to as biological means of protection .

Sometimes, in the absence of wind, extreme concentrations of air pollutants can be observed. In such cases a temporary reduction of emissions into the atmosphere is economically profitable. Capital costs are not worthwhile.

Ways of regulating industrial emissions under dangerous meteo conditions are being dveloped in Russia. Minimized sporadic emissions , transfer to a good quality fuels with low sulfur content , a short termed stoppage of heavily emitting enterprises of secondary importance , shifting of technological processes can also be attributed to preventive measures. In St. Petersburg, for example, at some thermal power stations the operative use of gas or low content sulfur fuels or boilers disabling is practiced under weather conditions contributing to the higher concentrations of emissions.

The best way for cleaning and utilization of polluted air is photosynthesis. It is green plants that provide fresh air. However, it should be mentioned that in case of strong pollution, the intensity of photosynthesis markedly decreases.

It has been stated that hydrogen oxide concentration behind a thick 4- rows tree plantation is 2-3 times lower, than behind a 1-2 rows tree plantation without a shrubbery. Plants also reduce concentrations of other gases and dust.

Observations show that the main bulk of releases is formed at the distance of 300-500 m from the source of origin. Under such conditions plants bear various obvious and conspicuous changes: leaf plates twist, get dried, leaves fall down. That’s why a density of planting in the site of a source of pollution should be high. Green plants reduce gas and waste pollution,contribute to the recovery of plants activity.

The measures , mentioned above, reduce or fully exclude the atmospheric pollution . The ministry of Health service and sanitary epidemiologic control bodies constantly keep an eye on changes in the air conditions , analyzing air sample taken from stationary sites and in industrial zones.

The quality of air is under a constant control in all large urban territories. In about 70% of cities a decrease or stabilization of the pollution level caused by dust, sulfuric gas and sulfur hydrogen has been marked. The maximal permissible level of concentrations have been justified and developed for 44 harmful constituents and dozens of their combinations. The maximal permissible level for emission has also been stated for all main industrial enterprises.

However, in spite of stabilization and a certain decrease in the pollution level of the atmospheric air in Belarus, as a whole, in a number of places the situation still remains unfavorable (Mogilev,Vitebsk, Novopolotsk, Bobruisk, Mozyr, Svetlogorsk). The problem of formaldehyde air pollution will remain a concern (the average annual concentrations will overcome the maximal permissible level 2-3 times), automobile transport being the main source .

Table 3 .