SUITMA 2005 Cairo - Effect of various land uses on metal status of urban soils of Seville
SUITMA 2005 Cairo
| This abstract is about one of the papers of the Properties of unconventional soils theme of the SUITMA 2005 symposium. |
| E. Ruiz-Cortés,i | Rocio Reinoso,i |
| Encarnacion Diaz-Barrientos,i | Luis Madrid.i |
Although the possibility of transfer of toxic metals from polluted soils to animals and humans through the plants growing on them is being studied since long ago, the existence of large concentrations of such metals in non-agricultural soils located in urban areas is receiving growing attention from scientists. The use of these urban soils as recreational areas (parks, gardens) favours that they come easily in direct contact with humans, especially children, so that soil metals can be directly transferred to them. That is why it is important to have a systematic knowledge of the metal contents in soils of urban areas, and also to find out whether different land uses in urban soils are related with large metal contents.
Samples of soils within the urban area of Seville receiving various uses were studied. When selecting the sampling sites, care was taken to have a selection of the various land uses that can be distinguished for soils within the city. Five uses or categories were chosen including: (1) areas of agricultural use, (2) parks, (3) ornamental gardens, (4) riverbanks, and (5) roadsides.
Although most properties of soils in the urban area of Seville are fairly uniform, several consistent differences occur that seem related to some specific categories. Those soils that can be considered to be left in a more or less ‘natural’ status, namely riverbanks, show significantly lower organic matter and N contents, suggesting that much of the organic matter in other categories is due to the more frequent care that these categories receive. This care probably includes periodical addition of organic amendments. In contrast, soils of ornamental gardens, which are more often looked after by the Gardens Service, show significantly larger concentrations of metals of ‘urban’ origin (Cu, Pb, Zn), whereas no significant differences are found for other metals. In some of the samples from ornamental gardens, moderate pollution can be considered to exist.
Although some of the high contents observed for urban metals can be related with engine exhausts, tyre wear, etc., the statistical analysis of the data suggests a certain relationship between organic matter and moderate pollution with urban metals. Moreover, several of the high contents are found in gardens in areas away from dense traffic roads. Therefore part of the large contents in urban metals could also come from amendments moderately polluted with them. Traffic is likely to be less significant than in the past concerning lead pollution, due to the shift to unleaded petrol, but still other metals are produced by motor vehicles from lubricants, tyres, alloys, etc. Moreover, quality of organic amendments used in urban parks and gardens must be periodically monitored, as it may be a significant source of metals to the urban environment.
