This paper is the result of agricultural geological survey engineering.

Objective The uptake and accumulation of selenium in rice grain is determined by the bioavailability of selenium in paddy soils, which can be directly affected by its speciation pattern.In this study, the selenium speciation in soils from the west of Ankang City, Shaanxi province was analyzed to investigate the correlation of selenium content in rice grain with the speciation pattern of selenium in soils.

Methods The distribution characteristics of seleniumspeciation in soils was examined by analyzing the concentrations of selenium in soils and rice grain.

Results The concentrations of speciation fractions varied significantly. Detailedly, the humic acid boundfraction of selenium accounted for more than 90% of the total content, whereas the water-solublefraction, ion-exchangeable fraction, manganese oxides fraction and carbonate bounded fraction occupied less than 5%. This study observed a tight relationship between the rice uptake of selenium and its concentration ofwater-soluble fraction andion-exchangeable fraction in paddy soils, which was consistent with the results found in previous studiesand will provide fundamental basis for the development of selenium-rich rice. The average concentration of selenium in rice grainwas 0.20 mg/kg, which met the national standard.

Conclusions The enrichment degree of selenium in paddy soils from the study area was high. This caused the relative accumulation of selenium in rice grain, which met the national standard. This study reveals broad prospects in the development of selenium-rich rice.