Spatial analysis techniques to survey the heavy metals content of the cultivated land in El-Fayoum depression, Egypt

The aims of this study are: (1) to produce a geometrically corrected physiographic-soil map scale 1:50,000 reduced to the attached map scale 1:300,000 for the studied area as a base to survey the heavy metals content and (2) to check the sustainability of the agricultural ecosystem through checking for the possible consequences of using drainage water as a source of irrigation water in some areas in El-Fayoum depression which have high heavy metal content due to pollution effects. To fulfill the first aim, 16 soil profiles were chosen to represent the different mapping units. Morphological description was carried out, and soil samples were collected for physical and chemical analysis. Based on enhanced thematic mapper images analysis and the geographic information system, coupled with the field work and laboratory analysis data, the physiographic-soil map was produced. The following main landscape units can be identified: (1) alluvial plain, (2) fluvio-lacustrine plain, and (3) lacustrine plain. With respect to the second aim, the drainage water dissolved heavy metal analysis was determined. The analysis shows that using this water as the sole source of irrigation in some areas in El-Fayoum depression, which is actually the case, with a cadmium dissolved content of 0.02 ppm will lead to an incremental increase of 80 g cadmium per acre per year, and since the warning value for cadmium concentration in the surface layer of the soil is 5 mu g/kg, i.e., 5 kg/acre. The warning value amount will accumulate in the soil during a period of 66 years. So, there are very strong doubts about the sustainability of this system. There are already signs of the buildup of heavy metal accumulation in the surface layer due to the use of drainage water in irrigating some parts of the studied area.