城市環(huán)境土壤污染的原因外文翻譯-環(huán)境工程-文庫吧資料
2025-05-22 13:32本頁面
【正文】 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 between the areas are enormous. For instance, the emission of suspended particulate matter ranged between 360 and 500 μg m?3 in industrial catchments of several Indian cities, whilst in residential and rural areas the values varied from 140 to 200 μg m?3 only. In relation to the respirable particulate matter with a diameter less than 10 μm, the results were 120–150 μg m?3 for industrial areas and 60–100 μg m?3 for residential and rural areas (CPCB 2020). If some industrial plexes with very high emissions such as heavy metal works are present, the soil contamination is going to reach extremely high values. As seen in Fig. and b, the nonferrous metallurgy plot in Pirdop (Bulgaria) with a population of 8,000 influenced the soil properties not only in the immediate proximity of the industrial plot. Apart from lead, the elements Cu and Zn revealed the same tendencies of decreasing values with increasing soil depth and with increasing distance fr
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