Studies on the sources of benzo[ a]pyrene in grain and aboveground tissues of rice plants

Abstract

Rice plant pot experiments designed to identify benzo[ a]pyrene (B[ a]P) sources in plant tissues were conducted in an air-quality controlled greenhouse built to prevent contamination from B[ a]P air pollution. Results from quartz sand cultures with control and 50, 100 and 500 μg kg −1 of B[ a]P treatments were compared with those from outdoor field experiments, in which rice plants were exposed to polluted air in the urban area of Shenyang, China. When B[ a]P was strictly controlled in both air and quartz sand culture medium, the background values of B[ a]P in rice plant tissues were uniformly very low. There was no significant difference of B[ a]P contents of rice grain between control and treatments of B[ a]P in controlled air quality trials. This indicated that the source of B[ a]P in the rice grains is not from any B[ a]P in the root culture media. The B[ a]P content of rice grain, husk, and stem with leaf sampled from outdoor field was up to 7.33-, 9.21- and 27.10-fold higher than corresponding tissues from air-quality controlled conditions. This indicated that polluted air is the main source of B[ a]P in aboveground tissues. Therefore control of B[ a]P pollution in ambient air is of prime importance for improving the quality of cereal crops.