A pool culture experiment was carried out to investigate the influence of different forms of sulfur fertilizers (sulfur and gypsum) on the transformation and migration of sulfur speciation in the rhizosphere and bulk soil of unpolluted and polluted paddy soils.The results showed that the redox potential (Eh) was about 93-283 mV and 83-254 mV, respectively, the soil solution pH was 7.5-8.4 and 7.7-8.4, respectively, and pe+pH was 9.1-13.2 and 9.1-12.5, respectively, in the bulk and bulk soil.Solution Eh values in Rhizosphere soil were generally higher than those in bulk soil, and solution pH in the former was generally lower than that in the latter.The different forms of inorganic sulfur followed the order of water-soluble sulfur (41%-81% of total inorganic sulfur, similarly hereinafter)>>sulfur adsorption (9%-34%)>hydrochloric acid soluble sulfur (8%-24%)>hydrochloric acid volatile sulfide (2%-8%) in the rhizosphere.In tillering and earing flowering,the concentrations of water-soluble and absorbed sulfur by application of gypsum were significantly higher than those using elemental sulfur.And its content in unpolluted paddy soil was significantly higher than that in polluted paddy soil. In the bulk soil,the forms of inorganic sulfur followed the order of water-soluble sulfur (40%-69%)>>hydrochloric acid soluble sulfur (18%-41%)>hydrochloric acid volatile sulfide (6%-16%)>adsorbed sulfur (0.7%-7.5%).The mass fractions of inorganic sulfur, organic sulphur and the total sulfur in the rhizosphere soil were in the range of 223-738 mg·kg-1, 574-1647 mg·kg-1 and 825-2287 mg·kg-1,respectively,and the corresponding fractions were in the range of 68-128 mg·kg-1, 108-391 mg·kg-1 and 200-477 mg·kg-1 in the bulk soil,respectively.Inorganic sulfur and organic sulfur of total sulfur in the rhizosphere were 20%-40% and 60%-80%, respectively, and those in the bulk were 18%-46% and 54%-82%, respectively.Total sulfur. organic sulfur and water-soluble sulfur and adsorbed sulfur and hydrochloric acid soluble sulfur in the rhizosphere were 3-11 times, 3-5 times, 5-7 times, 12-20 times, and 2-3 times of those in the bulk soil, respectively, whereas the hydrochloric acid volatile sulfur in the rhizosphere was lower than that in the bulk soil.
Keywords: polluted paddy soil; sulfur fertilizer; sulfur speciation; the bulk soil; the rhizosphere soil.