城市环境土壤污染的原因毕业论文外文文献翻译及原文

毕业设计（论文）外文文献翻译

文献、资料中文题目：城市环境土壤污染的原因

文献、资料英文题目：

文献、资料来源：

文献、资料发表（出版）日期：

院（部）：

专业：

班级：

姓名：

学号：

指导教师：

翻译日期： 2017.02.14

原文：

Causes of Soil Contamination in the Urban Environment Dust Deposition

Extensive dust deposition is mainly caused by industrial emission. It is deposited in dry conditions and as suspended particulate matter. The size of particulate matter varies. The fraction of less than 10 μm designated as respirable particulate ma tter is most dangerous for human health. A portion of cement dust and fly ash may exceed that value, but there are some kinds of particulate matter with a general size distribution of less than 10 μm like asbestos dust and smoke derived from oil-fired power stations. It should be borne in mind that the smaller the suspended matter is the higher the contaminant concentration is due to the enhanced sorption capacity.

Contaminated particulate matter can be transported from outdoors into rooms. There, a dust accumulation occurs, particularly if windows remain opened during daytime. Of interest is the comparison between garden soil and house dust concentration. In England it has been found that the Cd, Cu, Pb and Zn values were larger in house dust than in the associated gardens (Thornton 1991).

Dust formation in urban areas may play an important role, in particular in arid and semi-arid regions, where dry conditions dominates, but also in humid climates dust is of importance for soil formation. For instance, in the city of Hanover (Germany) with a population of 520,000, an enormous accumulation of 5–8 cm within 50 years was observed (Burghardt and Höke 2005). When dust development and deposition occurred without any filter technique systems, the deposited layer can reach enormous thickness as observed in vicinity of a coal processing factory in Halle (Germany) with its 230,000 inhabitants (Fig. 3.2).

One important feature of urban areas is the often exposed land surface you can never discover in woodland and pasture and over long periods percentages of bare soils are private gardens and allotments in wintertime, playing fields, cemeteries, demolition and building sites, derelict and disused, mostly industrial land, waste heaps, railway embankments, and storage sites, where permanent dust deposition occurs (Thornton 1991). In urban and industrial areas sealed sites are influenced as well,

since dust may easily penetrate into gaps between pavement stones, cobbles as well as railway embankments, constantly filling them up. It is supposed that dust will be laterally transported on the pavement stones and ultimately concentrated in gaps downslope (Burghardt and Höke 2005).

It is logical to expect that urban soils show higher contamination levels than the rural areas because of their proximity to a number of potential pollution sources. Big cities like New York (USA) with 23,200,000 inhabitants are affected by several contamination sources, for instance simultaneous industrial emission, impact of traffic, deposits of technogenic substrates, etc. Consequently, a decline in e.g. 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 m g 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. 2005).

The urban-to-rural gradient has frequently been found in developed countries of the northern hemisphere. Figure 3.3 presents the lead concentrations of five relatively small towns in the United States. The contamination level of the urban lawn is comparably 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 combustion 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 long-term mixing of the humic topsoil and the mineral subsoil, causing translocation of contaminants like Pb (Craul 1992) (see Section 6.3).

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. 2008). They collected material from nine sites according to a gradient from suburban (No. 1) to urban zones (No. 9) (Fig. 3.4a–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