Abstract
Cultivation of plants as sources of human food and livestock around the big cities like Tehran is common. In some of these areas, untreated raw sewage and urban wastewaters are used for irrigation of these plants. In Southern Tehran, the long-term irrigation of plants with waste water is produced by urbanactivities, regardless of the increase of soil fertility and the provision of macro and micro nutrients, such asnitrogen, phosphorus, iron, zinc and manganese. Also, it increased soil organic matter and heavy metalsaccumulation, such as lead, cadmium, nickel and chromium in those plants which are irrigated by wastewaters. The total amount and absorbable concentration of the mentioned elements are increased in irrigated soils, plants and finally, in edible parts of plants. Maximum accumulation of heavy metals was observed in roots, shoots and seeds, respectively. Also, the highest amount of uptake and accumulationwas observed in glandular products. A study on element accumulation and defined standards shows that it is not possible to produce crops under these areas or at least it could be possible only for the production of some of the crops that their economic parts are not directly consumed by humans or are useable after some processes. Currently, the dominant regional pattern of cultivation is maize - wheat whose final product is directly and indirectly consumed by humans or livestock. Accumulation of heavy metals in cornand wheat plant is dangerously close to the threshold. In addition, in other plants grown in these regions, accumulation of heavy metals in plant economic organs is more than normal restriction and toxicitythreshold for humans and livestock. Considering these problems and hazardous effects of waste water consumption, it is necessary to monitor the cultivation patterns and limit cultivation of those plants which have high level of heavy metal absorption and transport into economic and edible parts. It is suggested that these areas are suitable for wood production and orchards’ establishment.
Key words: Urban waste water, heavy metal, south of Tehran, agricultural products.
