Motor vehicles leaded fuels

Heavy metals concentration generally decreases in urban soils away from the main road network and with increasing depth of sampling. This can be explained by the strong dependence of these contaminants on the use of motor vehicles—leaded fuels for Pb, tire wear for Zn and Cd, brake pads for Sb, converters and exhaust systems for platinum group elements (PGEs). 

The use of propane as a motor vehicle fuel has been highly developed in some countries, particularly in the USA, Holland and Italy. It is, of course, an entirely lead-free fuel. Very high efficiencies can be obtained using a gaseous fuel in spark-ignition engines since intimate mixing of the fuel and air is much more easily achieved than with a liquid fuel. This results in a much cleaner exhaust, with considerable reductions in CO and hydrocarbons. 

The release of PCDD/PCDF from transport activities was estimated to be very minimal and not reported for uncontrolled combustion processes (Universiti Sains Malaysia, 2004). In the Department of Environment Malaysia 1997 report, the major sources of air pollution in 1996 were motor vehicles, 82%, power stations, 9%, industrial fuel burning, 5%, industrial production processes, 3%, domestic and commercial furnaces, 0.2%, and open burning at solid waste disposal sites, 0.8% (Afroz et al., 2003). Leaded gasoline has been phased out since 1998 and most cars have been fitted with catalytic converters since then. Consequently, a minimal release of PCDD/PCDF is expected from motor vehicles that are mainly from diesel-powered vehicles. The released air pollutions monitored were CO, N02, S02, 03, and suspended particulate matters. 

Direct and indirect evidence indicates that motor vehicles are a source of environmental PCDD/Fs, with leaded gasoline emitting higher levels of PCDD/Fs into the environment than unleaded gasoline.20-23 Leaded fuel-powered vehicles... 

Even so, the victory of motor vehicles over the horse was not quick or easy. The 20 million horses used for transportation in the United States in 1900 swamped by a factor of 10,000 the few thousand motorized vehicles on the road at the time. The gasoline car was not even the leading competitor to the horse. They shared the motorized vehicle market with battery electric and steam powered vehicles (Cannon, 1995). Despite the advantages of motorized vehicles, opposition was strong because the new fuels and technologies were disruptive. Very few farmers became oil drillers and even fewer stable boys became automotive engineers. Hundreds of thousands of jobs were lost in the transition. 

Combustion particles are of complex chemistry, carrying most of the trace elements, toxins or carcinogens generated from the combustion process. Combustion of different types of fuels results in emissions of various trace elements which are present in the fuel material. In most cases there is not just one specific element that is related to the combustion of a particular fuel, but a source profile of elements [2]. For example, motor vehicle emissions contain Br, Ba, Zn, Fe and Pb (in countries where leaded petrol is used) and coal combustion results in the emission of Se, As, Cr, Co, Cu and Al. For comparison, the crustal elements include Mg, Ca, Al, K, Sc, Fe and Mn. Since most of the trace elements are nonvolatile, associated with ultrafine particles and less prone to chemical transformations, they often remain in the air for prolonged periods of time in the form in which they were emitted. 

Fig. 13.3 The declining use of leaded fuels in motor vehicles is illustrated by these statistics from the US. [Data US Geological Survey.]...

Exposure to airborne lead from motor vehicles using leaded petrol has been the subject of a great deal of scientific debate. Old vehicles with poor emission control are allowed to travel freely on the Indian roads. Currently, there is no effort towards providing lead-free petrol in India, whereas in all major cities of the industrialized nations strict emission controls are enforced. The use of cleaner fuels [10] has led to declining emissions in recent years. In India, the lead content in petrol has increased with a rise in the octane number from 83 to 87 since 1983. 

The atmosphere is the recipient of many of the products of our technological society. These effluents include products of combustion of fossil fuels and the development of new synthetic chemicals. Historically these emissions can lead to unforeseen consequences in the atmosphere. Classical examples include the realization in the 1950s that motor vehicle emissions could lead to urban smog and the realization in the 1970s that emissions of chlorofluorocarbons from aerosol spray cans and refrigerators could cause the depletion of stratospheric ozone. 

Atmospheric particulate matter samples can be analyzed routinely for more than 50 trace elements. Trace element emissions arise from a large number of different source types in urban areas. For example, motor vehicles burning leaded fuel, electric arc steel furnaces, Kraft recovery boilers, and secondary lead smelters contribute to atmospheric lead concentrations. The wide spectrum of sources, together with the fact that trace metals often are only a minor fraction of the mass emissions from each source, obscure the relative importance of the contributors to atmospheric trace element levels. 

However, despite all the progress being made, the uncontrolled production unavoidably leads to environmental problems such as climate change or emission of toxic products. For example, dioxins and furans are unintentionally formed and released from various sources like open burning of waste, thermal processes in the metallurgical industry, residential combustion sources, motor vehicles, particularly those burning leaded gasoline, fossil fuel-fired utility and industrial boilers, waste oil refineries etc... 

An everyday example of this is the poisoning of the previously mentioned exhaust catalyst in motor vehicles by the heavy metal lead (also compare Sect. 19.4). This is why lead-free fuels must always be used. 

Leaded gasoline was banned in the US in 1986, but lead additives are still used in racing fuels, as well as fuels for watercraft, fight aircraft, and farm machinery [204]. In Canada, unleaded gasoline was introduced in 1975, and leaded gasoline was banned for use in motor vehicles in 1990. In Ontario, for example, ambient air Pb concentrations declined from 0.3 to 0.01 p-g/m between 1980 and 1990 [190]. For comparison, with these air Pb concentrations, Patterson [6] calculated natural air Pb concentration of 0.0005 p-g/m which is a factor of twenty lower than the lower LOD for air Pb employed by the OMEE. 

Fuels are used to do something, such as move a motor vehicle, cook a meal or heat a house. There is a strong link between the use of the fuel and the fuel as an energy source for the task. Students may think energy is consumed as the task is done. Calculations of fuel consumption in a car engine or of gas consumed by a boiler lead to this. We need to show students that we transfer energy from usable to non-usable forms. The overall amount of energy in the Universe remains constant. 

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