华北平原潮土酸度特征与酸化敏感性的初步探讨

PRELIMINARY STUDY ON ACIDITY AND ACIDIFICATION SENSITIVITY OF FLUVO-AQUIC SOILS OF NORTH CHINA PLAIN

采集华北平原潮土样品对其酸度特征和酸化敏感性进行了初步探讨.结果显示,过量施用氮肥导致的硝酸盐积累是华北平原潮土pH值下降的重要原因,硝酸根与土壤pH值呈显著负相关.碳酸钙溶解是当前潮土缓冲酸化的主要过程,决定着潮土对外界酸输入的响应方式和敏感程度.随着酸输入量的增加,低碳酸钙土壤的pH值迅速下降,但高碳酸钙的石灰性潮土对酸输入不敏感.潮土酸化的敏感性主要决定于碳酸钙含量,临界缓冲容量、酸缓冲强度及pH缓冲强度等土壤敏感性指标均与碳酸钙含量呈显著正相关.初步分析显示,在长期集约化耕作的影响下低碳酸钙潮土存在pH值急剧下降的风险.建立和完善适合华北平原潮土及其它中-碱性土壤的酸化敏感性评价方法和指标体系已成为对潮土酸化进行科学调控的迫切需要.

Fluvo-aquic soils in North China Plain were collected for the preliminary investigation of their acidity characteristics and acidification sensitivity,under intensive agricultural utilization.Soil pH significantly correlated with nitrate,which indicated that overuse of nitrogen fertilizer was the important driving factor for soil pH decline.Dissolution of CaCO3 is the main acidification buffer process in these fluvo-aquic soils.Soils with lower CaCO3 were sensitive to the acid input with fast pH drop,while soils with higher CaCO3 were insensitive to continuous acid input.Critical acid buffer capacity,acid buffer intensity and pH buffer intensity,calculated based on acid-base titration curve,positively correlated with CaCO3 content.Such relationships clearly showed the strong dependence of acidification sensitivity on soil carbonates.Depletion of soil carbonates induced by intensive utilizations will result in,in turn,faster decrease in soil pH,which brings potential risk to soil quality and environment health.Methodology improvement on acidification sensitivity assessment,with enough consideration to the buffering characteristics,is the most urgent task in the regulation of acidification in fluvo-aquic soils.