Measuring and Zoning of Heavy Metals Pollution in Soil Using GIS for Fields to the South of Tehran

South lands of Tehran are the main source of agricultural productions in which some kinds of vegetables, legumes, cereals and other crops are growing. This research measured and zoned heavy metal soil pollution in 1500 ha of these cultivated fields south of the city of Tehran in Iran. In this study, 128 samples were collected using the systematicrandom method from 64 areas at depths of 0-30 cm and 30- 60 cm and the concentrations of cadmium, chromium, nickel, lead and zinc were measured. The parameters of pH, electrical conductivity, and phosphate were also recorded. Zoning maps were developed using the inverse distance weighted method. The results showed that concentrations of heavy metals, with the exception of nickel, were higher at the shallower depth than at the lower depth. The zoning map shows that cadmium, chromium, lead and zinc occurred in greater concentrations in the northern areas and nickel in the southern areas. A comparison of these results with Iranian soil resource pollution standards indicates that the levels of chromium, nickel and zinc exceeded the standards in some parts of the study area.