Dynamics Analysis for the Distribution of Polycyclic Aromatic Hydrocarbons in Rice

Ten species of polycyclic aromatic hydrocarbons (PAHs) in rice were determined. Total PAH levels in unpolished rice ranged from 46 to 77 μg/kg dry weight, which an arithmetic mean value of 58 μg/kg dry weight. Phenanthrene was the most abundant in rice and rice straw. Individual PAH content in unpolished rice was higher than in polished rice. Total PAH contents in unpolished rice was 3-fold in polished rice. PAH concentration ratios for the lighter molecular weights (152–202) to the heavier molecular weights (228–252) in rice and paddy leaf, approximated to 70 : 30. Fluoranthene and pyrene commonly exist in environmental waters. River water and rainwater contained much greater levels of PAHs than groundwater. Fluoranthene was the most abundant and phenanthrene was second most abundant in soil. PAHs in the atmosphere directly contributed to the paddy/rice through atmospheric deposition and PAHs in soil and environmental waters indirectly contributed to the paddy/rice through root uptake and bioconcentration.