土壤组分对磷形态和磷吸附-解吸的影响——基于三峡库区消落带落干期土壤

Effect of organic matter and iron oxides on phosphorus forms and adsorption-desorption on dry-period soils in the water-level-fluctuating zone of the Three Gorges Reservoir

通过选择性去除土壤组分的方法,探讨了三峡库区消落带落干期3种典型土壤中有机质、铁氧化物组分对磷形态和磷吸附-解吸的影响.结果发现,三峡库区消落带落干期3种典型土壤去除的有机质以易氧化组分为主,去除有机质后,土壤中各种磷形态的含量变化较小.然而,去除游离铁氧化物后,土壤中各种磷形态的含量均发生明显降低.同时,去除有机质、游离铁氧化物组分后并未改变土壤中各种磷形态的相对大小顺序,均为:钙结合磷(Ca-P)>有机磷(OP)>铁/铝结合磷(Fe/Al-P).此外,黄壤(FJ)、紫色潮土(KX)和灰棕紫泥(FL)去除有机质后对磷的吸附能力较原始土壤仅分别降低0.5%、2.3%、6.5%(P=0.017<0.05,显著性差异),表明3种土壤中有机质组分对磷吸附的影响较小;而去除游离铁氧化物后对磷的吸附能力分别降低45.6%、51.7%、43.9%(P=0.004<0.05,显著性差异),表明土壤中游离铁氧化物组分是决定磷吸附大小的重要因素.另外,3种土壤去除游离铁氧化物后较原始土壤吸附磷的解吸能力明显增加,表明游离铁氧化物组分是控制3种土壤吸附磷的解吸的重要因素.FL土壤去除有机质组分后较原始土壤吸附磷的解吸能力略有降低,而KX和FJ土壤去除有机质组分后较原始土壤吸附磷的解吸能力无明显差异,表明有机质组分对土壤吸附磷的解吸的影响与土壤类型有关.

Selective removal of organic matter or iron oxide from three typical dry-period soils were explored to investigate its direct effect on P fractions and adsorption-desorption behavior in the water-level-fluctuating zone (WLFZ) of the Three Gorges Reservoir (TGR). The data showed that kinds of P fractions in three dry-period soils were not significant decreased with removal of readily oxidizable organic matter. However, kinds of P fractions were significantly decreased with removal of free iron oxides in the three soils. Notably, different P fractions were both in the order as follows: Ca-P > OP > Fe/Al-P, before and after removal of organic matter or free iron oxides in the three soils. Moreover, after removal of organic matter, the adsorption capacity of yellow soil (FJ), purple alluvial soil (KX), grey brown purple soil (FL) for P was only decreased by 0.5%, 2.3%, 6.5%(P=0.017<0.05, significant difference), respectively, which indicated that P adsorbed on the three soils were little influenced by organic matter. In addition, after removal of free iron oxides, the adsorption capacity of FJ, KX, FL soil for P was significantly decreased by 45.6%, 51.7%, 43.9%(P=0.004<0.05, significant difference), respectively, which revealed that P adsorbed on the three soils were dominated by free iron oxides. More importantly, the desorption capacity of three soils for P was increased after removal of free iron oxides, which presented that free iron oxides were also the predominant factor to control desorption behavior of freshly sorbed P. Then, the desorption capacity of FL for P was little decreased after removal of organic mater, and there were no distinction for it before and after removal of organic matter in KX and FJ soils, which showed that the desorption capacity of three soils for P were influenced by organic matter related to soil category.