Traffic-related Air Pollution - Hydrocarbons 1993
The Berlin primary road network has a length of 1,163 km. The daily travelled distance on this network totals 30,000,000 vehicle kilometers. This figure is almost 100 times the earth’s circumference. The secondary road network is about 4,000 km long, and the daily travelled distance is only about 5,600,000 vehicle kilometers. Figure 5 depicts the percentual distribution of exhaust and abrasion emissions of various pollutants according to the Berlin primary and secondary road networks. It is conspicuous that an extremely high percentage of hydrocarbon and benzol emissions occur on the secondary road network. These emissions are strongly influenced by cold start factors; and about half of the initial kilometers travelled after a start occur on secondary roads.
Hydrocarbon Emissions in Primary Road Network
Map 03.09.1 shows that the primary long outbound arterial roads stand out with particularly high exhaust gas emissions at 1) the city expressway ring (Stadtautobahnring), 2) along the east-west axis on roads such as Bismarckstrasse to Kaiserdamm in Charlottenburg, and Karl-Marx-Allee to Frankfurter Allee in Mitte and Friedrichshain and 3) other primary arterial roads. Emission loads over 50 kg/m and 50 t/km have been measured at these roads. The significant impact of these main emission segments are clearly to be seen in a comparison with the highest grid value (150 t/km2 × a) in Map 03.09.2, Exhaust Gas Emissions on the Entire Road Network. These primary roads have about 6 % of area on a 1 sq km grid; their emission values are about 30 %.
Emission level evaluations show clear correlation to traffic volume, insofar as the characteristics of individual roads are taken into consideration. Most of the 70 km-long expressway falls into the highest emission categories. The AVUS segment starting at the Funkturm (broadcast tower) triangle, however, has a traffic volume of over 70,000 vehicles a day, and shows a relatively lower pollutant load of 13 kg/m × a. This is due to a relatively undisturbed traffic flow.
Exhaust Gas Emissions in Entire Road Network
Distance travelled on the primary road network is about five times greater than distance travelled on the secondary road network. This 5:1 ratio is not reflected in the amounts of hydrocarbon emissions on the two road networks. This disproportion can be seen in Map 03.09.2 – Exhaust Gas Emissions in Entire Road Network. All grid areas within the inner ring of the City Rail Circle Line (S-Bahn-Ring) have over 50 t/km2 × a. The influence of individual long avenues is no longer so clear. 1993 pollutant loads in areas of West Berlin were greater than in East Berlin, but this difference should have evened out by now. East Berlin motor vehicle registrations and distances travelled have increased, and are now near western levels. Other local centers outside the inner city with over 50 t/km2 × a have emerged in the boroughs of Spandau, Reinickendorf, Marzahn, Treptow and Neukölln.
Volatile hydrocarbon requires that fuel tank evaporation be considered separately from the direct emissions produced by moving vehicles. The fuel tank respiration of non-moving motor vehicles are differentiated from evaporative effects resulting from use; i.e. hot and warm motors. Map 03.09.3 gives parked motor vehicle vapor emissions and Map 03.09.4 gives evaporative emissions based on hot and warm engines.
Evaporative Emissions from Tank Respiration
Even vehicles parked and not driven for a day can produce hydrocarbon emissions through tank respiration. Tank respiration results from pressure differences between the fuel tank and the carburetor float chamber. Pressure differences are caused by temperature fluctuations. It has been calculated that tank respiration produced 1,830 tons of hydrocarbon emissions in Berlin in 1993. This is a good 5 % of total emissions. These tank respiration emissions could have been prevented and used for fuel if vehicles had been equipped with activated carbon filters.
The distribution of emission levels in the various grids reflects both population density and the ratio of vehicles to residents. Residential areas in outlying areas, some borough centers, and the densely built inner city stand out.
Evaporative Emissions from Vehicles after Use / Hot Engines and Warm Engines
Hot and warm engine evaporative emissions are produced when engine and exhaust systems heat the fuel contained in fuel-feed lines after the engine is shut off. Hot and warm engine evaporative emissions reach levels of 6,600 tons; much greater than tank respiration emissions. Hot and warm engine evaporative emissions are a decisive influence on the distribution of total motor vehicle evaporative emissions (Map 03.09.5 – Total Evaporative Emissions of Motor Vehicle Traffic). Cars, station wagons and light utility vehicles with conventional internal combustion engines (Otto engines) produce these evaporative emissions when their engines are switched off – this occurs about 3,270,000 times a day in Berlin. The grids with the highest levels of over 50 t/km2 × a are within the inner city. The inner city is the most frequent destination for traffic – for work, recreation, and shopping. But some local centers, such as Schlossstrasse in Steglitz, have registered loads of around 30 t/km2 × a. These local centers are well above the average Berlin load of 7 t/km2 × a.
Total Emissions of Motor Traffic
Map 03.09.6 – Total Emissions of Motor Traffic portrays all emission producers. These producers were previously depicted only singly. A comparison with Map 03.09.2 – Traffic Emissions 1989 (cf. Map 03.08 SenStadtUm 1994) enables a few conclusions to be drawn about changes in the number of motor vehicles and in total emission loads. A total emission load of 51,900 tons was ascertained in 1989. The highest motor traffic emissions were determined in the eastern inner city. This is mainly due to the high emissions produced by vehicles with two-stroke engines. Total emissions then fell to 25,500 tons, after 1) a decrease in the number of vehicles with two-stroke engines, such as Trabants and Wartburgs, and after 2) a 57 % increase in the number of motor vehicles equipped with regulated catalytic converters (reference year 1993). Exhaust gas emissions are the dominate source, with 60 % of total emissions. Relatively high loads are registered in the area between the city expressways in the North and West, Steglitzer Kreisel in the South, and the Karl-Marx-Allee / Frankfurter Allee thoroughfare in the East. No particular focuses of loads were determined. The highest loads of 160 to 212 t/km2 × a were found along the long Kaiserdamm – Bismarckstrasse avenues, as well as south of them. It is conspicuous that twice as many hydrocarbon emissions can be produced in residential areas with little traffic but many parked vehicles: stopped traffic can produce twice as much hydrocarbon emissions as moving traffic.
Evaporative Emissions at Fuel Stations
Map 03.09.7 shows fuel station refilling emissions for the inner city in 1993. Only motor vehicle refueling is considered here; refilling of the petrol depot at the fuel station is not considered. The most significant amount of refueling emissions, about 96 %, results from fuel stations which do not have fuel vapor recovery systems.
Total refueling and transfer emissions at Berlin fuel stations include those resulting from the transfer of fuel from tankers, ship tankers, and railroad tank cars into fuel station depots. Total refueling and transfer emissions in 1993 amounted to about 3,630 tons of hydrocarbons; approximately 10 % of total hydrocarbon emissions. About 96 %, the most significant proportion by far, resulted from fuel stations which did not have fuel vapor recovery systems. All fuel stations selling more than 1,000 m3 of fuel per year were required to be equipped with fuel vapor recovery systems before the end of 1997. This requirement has been mostly fulfilled, as noted in Table 3. The fuel vapor recovery systems and the declining number of fuel stations, taken together, should reduce loads to a little less than 20 % of the 1993 total.
The distribution of fuel stations is naturally closely coupled to developed areas. Some of these areas have emissions at levels similar to total motor traffic evaporation resulting from tank respiration and switched-off warm and hot engines. The number of grids registering high emission loads decreases noticeably as the edges of the city are approached.
Exhaust Gas Emissions of Benzol on Primary Road Network
Map 03.09.8 shows carcinogenic benzol emissions on the primary road network. For calculation purposes, different amounts of benzol in HC exhaust emissions were assigned based on engine type. The benzol percentage for vehicles with regulated catalytic converters in a “warm” condition was set at 8.1 %. A mean of 5.3 % was assigned for total vehicles.
Benzol emissions are proportional to hydrocarbon emissions due to their close relationship (see Map 03.09.1). A total of 793 tons of benzol were emitted on the Berlin primary road network; this is about 50 % of total traffic-related benzol emissions. Knowledge about benzol emission distribution on the primary road network is necessary to ascertain the pollution concentration for each area, locate heavily polluted areas, and to conduct comparisons with the yearly average concentration value, as stipulated by the 23rd Regulation of the Federal Pollution Control Law (cf. Map 03.10).
Benzol – Total Emissions of Motor Vehicle Traffic
Map 03.09.9 shows that almost the entire inner city has emission levels of over three tons per square kilometer per year in each grid. Benzol loads are considerably lower towards the city edges; this is similar to total hydrocarbon loads. Only a few borough centers have levels close to those in the inner ring of the City Rail Circle Line (S-Bahn-Ring).