Abstract: In autumn 2008, a total of 65 plough layer soil samples were collected from the paddy fields in Qianguo Irrigation Area located at the downstream of the Second Songhua River. These paddy fields were irrigated with  water from the River, and had different irrigation histories. The Cu, Pb, Zn, Cd, Ni, As, and Hg concentrations in the soil samples were determined, and the accumulation characteristics, input approaches, and pollution sources of these heavy metals were analyzed. The Cu, Pb, Zn, Cd, Ni, As, and Hg concentrations in the samples were 14.1- 28.4 mg·kg^-1, 37.6-57.4 mg·kg^-1, 53.3-84.4 mg·kg^-1, 0.044-0.367 mg·kg^-1, 18.4-37.0 mg·kg^-1, 3.25-12.11 mg·kg^-1, and 0.031-0.155 mg·kg^-1, respectively. The Pb, Hg, and Cd exhibited an obvious accumulation trend, with their concentrations being 100.0%, 38.7%, and 66.1% higher than the baselines, respectively, while Cu, Zn, Ni, and As had less accumulation. With the increase of irrigation history, the Pb concentration showed a decreasing trend, while the Hg concentration was in reverse. There was no significant correlation between the Cd concentration and the irrigation history. According to source analysis, soil Pb  mainly originated from the atmospheric Pb deposition via historical use of leaded gasoline, soil Hg was  from the polluted irrigation water from the Second Songhua River, and soil Cd was from the use of chemical fertilizers, pesticides, and other agrochemicals. Though the Pb, Hg, and Cd had obviously accumulatied in the paddy fields in Qianguo Irrigation Area, their potential ecological risk was still low, and would not pose threat on the local agricultural production and food security.

Key words: the Second Songhua River, Qianguo Irrigation Area, soil, heavy metal,  , ecological risk