title: Effect of phosphate addition on the sorption-desorption reaction of selenium in Japanese agricultural soils.
abstract: Desorption levels of soil-sorbed selenium (Se) were studied by adding phosphate to 22 typical Japanese agricultural soils. Soil-soil solution distribution coefficients of Se (Kd-Se) were measured using a batch process as an index of Se sorption level, adding 75Se as a tracer. After the Kd measurement, extraction of soil-sorbed 75Se with a 0.1 M or 1 M Na2HPO4 solution followed to determine the amount of 75Se desorbed by the phosphate. When the 0.1 M Na2HPO4 solution was used, 18-70% of soil-sorbed Se was extracted (average: 47%). However, when the 1 M Na2HPO4 solution was used, 27-83% of soil-sorbed Se was extracted (average: 57%). The observed 75Se desorption percentage indicated the maximum Se removability by phosphate addition. The desorption percentage of Se with 1 M Na2HPO4 correlated with Kd-Se values, suggesting that the soil sample with higher Kd-Se contained more reactive components for phosphate-sorption than the soil sample with lower Kd-Se. To evaluate the effect of phosphate concentration on the Se sorption, the Kd-Se was measured for two typical soils under different levels of phosphate (0.1-10 mM PO4). The Kd values were decreased by phosphate addition for both soils. The Kd decrease was observed even for just 1 mM PO4. The phosphate addition with 1 mM PO4 is the same level as in P fertilizer applied to paddy fields in Japan. Therefore, it was suggested that Se desorption should occur in Japanese soils due to the phosphate input.
authors.affiliation: Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage, Chiba 263-8555, Japan. nakamaru@nirs.go.jp
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakamaru
authors.forename: Keiko
authors.initials: K
authors.lastname: Tagami
authors.forename: Shigeo
authors.initials: S
authors.lastname: Uchida
mesh_terms: D000327:Adsorption / Q000187:drug effects*; D018556:Crops, Agricultural / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007564:Japan; D010710:Phosphates / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D017680:Potassium Compounds / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D012643:Selenium / Q000737:chemistry*; D012987:Soil / Q000032:analysis*
chemical_list: D010710:Phosphates; D017680:Potassium Compounds; D012987:Soil; C013216:potassium phosphate; D012643:Selenium; C018279:sodium phosphate