城市環(huán)境土壤污染的原因外文翻譯-環(huán)境工程-文庫吧
2025-04-17 13:32 本頁面
【正文】 tamination sources, for instance simultaneous industrial emission, impact of traffic, deposits of technogenic substrates, etc. Consequently, a decline in . Cu, Ni and Pb concentrations was found with increasing distance from the city centre (Manhattan) into the rural district outside of the city. While in Manhattan Pb topsoil values of more than 130 mg kg?1 were measured, at a distance of 50–60 km the values decreased to about 40 mg kg?1, and at a distance of 120–130 km to about 30 mg kg?1 (Pierzynski et al. 2020). The urbantorural gradient has frequently been found in developed countries of the northern hemisphere. Figure presents the lead concentrations of five relatively small towns in the United States. The contamination level of the urban lawn is parably high, as would be expected by the vicinity and exposure to high levels of air pollution in urban environments. The air pollution is related to metallic aerosols from heavy industry as well as bustion of fossil fuel. The investigations referred to lawns close to houses and in parks. The high level has not to be restricted to the upper horizons and forest floors. The activity of earthworms and ants (bioturbation) may play a role in the longterm mixing of the humic topsoil and the mineral subsoil, causing translocation of contaminants like Pb (Craul 1992) (see Section ). A city – suburb gradient has been confirmed by the soil investigations of the upper 5 cm in Marrakech (Morocco) with 1,200,000 inhabitants (El Khalil et al. 2020). They collected material from nine sites according to a gradient from suburban (No. 1) to urban zones (No. 9) (Fig. –c). It is obvious that the Cd, Cu, Ni and Zn values tend to increase the shorter the distance to the city centre is. However, other factors as well as the expected dust deposition close to the city influence the situation. With increasing distance to the historic city centre the anthropogenic disturbance of the soil profiles showed distinct fingerprints as well. The technogenic fraction in the upper soil layer reaches 14% at site No. 9, indicating the huge disturbance. The coarse technogenic fraction revealed similar values at a distance of approximately 500 m from historic centre. Behind this distance the percentage ranged between 1% and 2%. Because of their relatively high contamination level the findings may contribute to the soil pollution significantly (see Section ). Both the factors dust deposition and the presence of technogenic substrates overlaps each other with reference to the topsoil contamination. In general, dust concentration in industrial areas tends to be much higher than in residential and rural areas. In particular, in regions with factories that have a relatively low number of air pollution filter systems the differences be
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