利用^(31)P核磁共振技术研究污泥中磷在土壤中的形态转换

Transformation of Phosphorus Forms in Soils with Application of Sewage Sludge by Using Phosphorus-31-Nuclear Magnetic Resonance Spectroscopy

为了解污泥中磷在土壤中的化学行为,采用NaOH/EDTA浸提和31P核磁共振技术研究了污泥施用到3种典型土壤中后磷的形态变化。结果表明,和传统NaOH熔融法相比,NaOH/EDTA能浸提土壤中54%～93%的磷,酸性土壤磷的NaOH/EDTA浸提率相对高,而有碳酸钙沉积的土壤浸提率相对低。污泥施用到土壤后不但提高了土壤中磷的总量,而且增加了磷的形态,并和污泥本身磷的形态基本一致。磷在土壤中的形态变化主要发生在污泥施用到土壤的14d之内,之后磷的形态基本稳定。其中无机正磷酸盐含量从55.22%～57.88%增加到80.32%～87.47%,正磷酸二酯完全消失,正磷酸单酯含量从23.80%～28.84%降至15%左右,而无机焦磷酸盐含量从10%左右降至1%以下。污泥施加到土壤中后,有机磷在短期内转化为无机磷,虽然有利于植物对磷的吸收利用,但对水体富营养化的潜在危害加大,建议污泥土地利用时要做到少量多次。就土壤不同性质而言,低pH和粘质土更有利于有机磷固定。

In order to understand the chemical behavior of phosphorus from sewage sludge in soils, the NaOH/EDTA extractant and 31P nuclear magnetic resonance spectroscopy （ 31P-NMR ） were applied to study the change of phosphorus forms in three typical soils after the sewage sludge application. The results showed that NaOH/EDTA could extract about 54% -93% of phosphorus from the soils, and the extraction ratio for phosphorus in acid soils was much higher than that in soils with calcium carbonate. Application of sewage sludge not only increased the total phosphorus content, but also changed the phosphorus forms. The phosphorus forms in soils were the same as these in sewage sludge. The change of phosphorus forms in the soils occurred in fourteen days after the sewage sludge application, and then they became stable. The proportion of orthophosphate in total phosphorus increased from 55.41%-58.59% to 82.70%-87.47%, orthophospbate diesters disappeared, the proportion of orthophosphate monoesters in total phosphorus decreased from 23.80%-28.49% to about 10%, and the proportion of pyrophosphates decreased from about 10% to about 1%. The organic phosphorus was easy to transform to inorganic phosphorus quickly after the sewage sludge application, which was favor to adsorption of phosphorus by soils and its utilization by plants. However, the transformation could increase the risk of phosphorus to eutrophication of the water body. Therefore, it might be a good idea that small amount of sewage sludge was applied many times. For various soil properties, clay soils with low pH were in favor of organic phosphorus sequestration.