硫素对水稻吸收砷的生物有效性及其在土壤中形态影响

Influence of Sulfur on the Bioavailability of Arsenic Uptake by Rice(Oryza.sativa L.) and Its Speciation in Soil

采用外源砷污染水稻土进行水稻盆栽实验,研究不同形态硫肥(单质硫和石膏)对水稻吸收砷的有效性及其在土壤中赋存形态的影响.结果表明,在水稻不同生育期内,土壤溶液pH平均值范围为7.38~7.45,且AsS0和AsS1处理的高于AsS2处理;土壤溶液氧化还原电位Eh值变化在200 mV左右,且AsS0处理高于AsS1和AsS2处理;从不同生育期水稻根系、地上部茎叶及籽粒干物重来看,施用S肥(单质硫及石膏)能提高水稻的干物质质量,单质硫和石膏处理的差异不显著;水稻根表胶膜以Fe膜为主,含量达到10~30 g·kg-1,Mn膜相对较少,含量仅为0.1~1.3 g·kg-1,根系吸附的铁锰胶膜含量的差异主要表现在分蘖期,单质硫处理能比石膏硫处理的能促进水稻根系表面铁锰胶膜的形成;水稻根表胶膜吸附As量分蘖期为583~719 mg·kg-1,孕穗期为466~621 mg·kg-1,扬花期和成熟期为310~384 mg·kg-1,这与铁锰胶膜形成厚度一致;施用S肥能明显降低水稻根系、地上部茎叶以及籽粒中As的含量,且施用石膏硫效果更好,这可能与孕穗期铁锰胶膜吸附As有关.根据土壤砷的赋存形态,非专性吸附态和专性吸附态As是最有活性的,在分蘖期AsS1处理它们之和显著低于AsS2处理的As含量2.85 mg·kg-1,而在扬花期AsS1处理Asnea+Asea之和高于AsS2处理的As含量0.77 mg·kg-1,或许有更多的As溶解于土壤溶液中,造成处理AsS1的生物有效性高于处理AsS2.

Pot experiments using exogenous arsenic-polluted paddy soils were carried out to investigate the influence of different forms of sulfur fertilizers( sulfur and gypsum) on As uptake by rice and its chemical speciation. Soil solution pH value ranged 7. 38-7. 45 in different growth period of rice,and the pH value of AsS0 and AsS1treatments was higher than that of AsS2 treatment. Variation of Eh value in soil solution was about 200 mV and the Eh of AsS0 was higher than those of AsS1 and AsS2treatments. From dry matter weight of root and stem and grain of rice,S-fertilizer applied by sulfur and gypsum could improve the amounts of dry matter in rice,while the effects of sulfur treatments and gypsum treatments were not significant. Concentrations of Fe and Mn in iron-manganese plaque on rice roots were 10-30 g·kg- 1and 0. 1-1. 3 g·kg- 1,respectively. Contents of Fe-Mn plaque were mainly different in the tiller stage.Elemental S treatment could more greatly promote the formation of Fe-Mn plaque of rice root than gypsum treatment. Concentrations of As adsorbed by rice roots surface plaque were 583-719 mg·kg- 1in tiller stage,466-621 mg·kg- 1in boot stage,and 310-384mg·kg- 1in flower and matur stage. And it was consistent with the thickness of Fe-Mn plaque on rice root surface. Concentrations of As uptake in roots and stem and leaf and grain were significantly reduced by the application of S fertilizer,and it may be related to the amount of As adsorbed by Fe-Mn plaque at boot stage. According to chemical speciation of soil arsenic,As of non-specific and specific adsorption was most active,and their amounts of As adsorbed in AsS1 treatment were significantly lower by 2. 85 mg·kg- 1than that in AsS2 treatment in tiller stage,and was 0. 77 mg·kg- 1higher than that in AsS2 treatment in the flower stage. Perhaps soil arsenic was easily dissolved in the soil solution and the bioavailability of AsS1 treatment was better than that of AsS2 treatment.