有机酸对三峡库区消落带土壤无机磷形态转化和有效性的影响

Effects of Organic Acids on Form Transformation and Availability of Soil Inorganic Phosphorous in the Water-Fluctuation Zone of Three Gorge Reservoir Area

以三峡库区分布最广的紫色潮土、灰棕紫泥为对象,采用室内土柱模拟淋洗试验,研究了淋溶液中3种简单有机酸(草酸、柠檬酸和酒石酸)对三峡库区2种典型土壤无机磷形态转化及有效性的影响。结果表明:紫色潮土和灰棕紫泥2种土壤中磷均以Ca10-P为主,分别占无机磷总量的48.93%和28.20%,活性磷(Al-P、Fe-P、Ca2-P和Ca8-P)总量分别占无机磷总量的13.12%和36.91%。添加50mg/kg的外源无机磷经陈化后,磷主要向Al-P形态转化,2种土壤中Al-P分别增加了1.49倍和0.71倍,活性磷总量分别占无机磷总量的19.53%和43.51%。淋溶过程中,有机酸的存在对于土壤无机磷形态转化具有显著影响,有机酸促进了土壤磷向高活性形态转化,从而增加了土壤磷的淋出风险。灰棕紫泥土壤上,草酸、柠檬酸和酒石酸添加量同Fe-P和Ca10-P呈极显著负相关关系[r(Fe-P)分别为-0.938,-0.865,-0.935,r(Ca10-P)分别为-0.933,-0.896,-0.916,P<0.01,N=12],有机酸对Fe-P和Ca10-P的活化效应显著。2种土壤有机酸对无机磷的活化能力为灰棕紫泥>紫色潮土。灰棕紫泥上,草酸和酒石酸处理土壤有效磷与Fe-P和Ca10-P之间呈极显著负相关(r≤-0.795,P<0.01,N=12),而柠檬酸处理下灰棕紫泥有效磷与各形态无机磷之间的相关性规律不明显。

In this paper,2types of typical soils in Three Gorges Reservoir areas,including purple soil and grey-brown purple soil,were selected to investigate the effects of 3simple organic acids（oxalic acid,citric acid,and tartaric acid）on form transformation and availability of soil inorganic phosphorus,through soil column leaching experiment in laboratory.The results showed that Ca10-P was the main form of phosphorus in purple soil and grey-brown purple soil,accounting for 48.93% and 28.20% of total inorganic phosphorus in the 2types of soils,respectively.Active phosphorus（Al-P,Fe-P,Ca2-P,and Ca8-P）accounted for13.12% and 36.91% of the total inorganic phosphorus in purple soil and grey-brown purple soil,respectively.When we added 50 mg/kg of exogenous inorganic phosphorus,after aging,phosphorus primarily transformed to Al-P.The contents of Al-P in purple soil and grey-brown purple soil were increased by1.49 and 0.71 times,respectively,and active phosphorus accounted for 19.53% and 43.51% of the total inorganic phosphorus in the 2types of soils,respectively.During the leaching process,the existence of organic acid significantly affected the transformation of soil inorganic phosphorus,which prompted the activation of soil inorganic phosphorus and therefore increased the risk of phosphorus leaching from soils.In gray-brown purple soil,the adding amount of oxalic acid,citric acid and tartaric acid showed very significant negative correlations with Fe-P and Ca10-P（r（Fe-P）was-0.938,-0.865and-0.935,r（Ca10-P）was-0.933,-0.896and-0.916,P〈0.01,N=12）,indicating that the activation effects of organic acids on Fe-P and Ca10-P were remarkable.The phosphorus activation capabilities of organic acids in the 2types of soils listed in the following order：grey-brown purple soilpurple soil.For gray-brown purple soil,in oxalic acid and tartaric acid treatment,soil active phosphorus had very significant negative correlations withFe-P and Ca10-P（r≤-0.795,P〈0.01,N=12）,while in citric acid treatment,no obvious correlation existed between soil active phosphorus and various forms of inorganic phosphorus.