Residual Nitrate in Potato Tuber Samples Collected from Fields in Important Production Areas and the Main Fruit and Vegetables Supply Center of Tehran

Nitrate is an important pollutant that accumulates in edible parts of crops. This accumulation usually occurs because of misuse and excess use of N- fertilizers. Nitrate is transformed to nitrite and then to nitrosamine, which is a carcinogen compound, in digestion system of human and animal bodies. Potato is the third important foodstuff in Iranian food basket after wheat and rice. Therefore, it seems that evaluating the nitrate pollution in potato and recognition of the pollution sources and ways to reduce the pollution is necessary. Potato tuber samples were collected from the main Fruit and Vegetables Supply Center of Tehran once a week, from May 2008 to May 2009. Additionally, potato samples were collected directly from different farms in 9 most important potato-producing regions, namely, Esfahan, Charmahal, Hamadan, East-Azarbaijan, Ardabil, Tehran, Khozestan, Fars, and Kerman (Jiroft and Kahnooj). Nitrate content in edible part and water content of fresh potato tubers were determined in all 341 samples in the central laboratory of Soil and Water Research Institute of Iran. Results showed that nitrate content in potato tubers ranged from 10.2 mg. kg-1 FW, to 524 mg. kg-1 FW with a mean of 163.5 mg kg-1FW, which was in accordance with world normal range. Assuming 200 mg kg-1 FW as the European nitrate limit in potato tubers, it exceeded from this level in about 30% of the tuber samples, and assuming 246 mg kg -1 FW as the Iranian nitrate limit, it exceeded from this level in about 20% of the tuber samples. Results showed that harvest season could affect nitrate content in potato tuber. Mean nitrate content in potato tubers taken from Fruit and Vegetables Supply Center of Tehran during spring-summer was 216.55 mg kg-1 FW, and for samples taken during autumn-winter, it was 131.53 mg kg-1FW.