丘陵区紫色土不同土地利用方式下磷的吸附解吸特性

磷素是水体富营养化的重要限制营养元素,农地磷肥过量施入造成的磷流失导致水污染问题引起世界范围的普遍关注.本研究主要针对紫色土集中分布的四川盆地丘陵区土地利用方式多样、农业非点源污染显著等特点,采集不同土地利用方式(林地、坡耕地)下的典型酸性、中性及石灰性紫色土,开展磷素等温吸附解吸热力学实验,并结合Langmuir模型研究了不同类型紫色土对磷素的吸附-解吸特征的影响.结果表明,四川盆地丘陵区紫色土林地土壤磷素最大吸附量(Qm)及磷吸附缓冲容量(MBC)高于同类型紫色土农地土壤;林地土壤生物有效磷含量低于农地;农地磷素释放风险高于林地.相较中性及石灰性紫色土,酸性紫色土磷素最大吸附量、吸附缓冲容量低,但磷素解吸能力较高,表明酸性紫色土磷素释放风险较大.多重相关分析表明,尽管不同类型紫色土pH、有机质、土壤质地等因素对磷素吸附解吸并无单一的显著影响,从而无法针对所有3种土壤找出其影响磷素吸附解吸的共性因素,但因子分析结果表明pH、土壤质地及土壤总磷含量对磷素吸附解吸特性仍有直接影响.

Phosphorus Adsorption and Desorption Characteristics of Purple Soils under Different Land Use in Hilly Area

Phosphorus is an important limiting nutrient of water eutrophication ,and overdose of farmland phosphate have aggravated the water pollution .In the circumstances of multiple parent materials and land uses ,typical purple soils (Named as Entisol in SAT system ,US) have respectively been collected from forest and farmland in three sites ,representing acidic ,neutral and calcareous soils in hilly area of the Si-chuan Basin .T he characteristics of phosphorus adsorption-desorption of soil samples have been studied by incubation in Lab and Langmuir model analysis methods .Results show that the maximum adsorption ca-pacity (Qm) and buffer capacity (MBC ) of phosphorus ranged from 320 .82 -615 .81 mg/kg ,18 .16 -109 .65 L/kg of forest soils ,and 246 .02-454 .55 mg/kg ,11 .52-69 .30 L/kg of farmland soils ,w hich in-dicates higher phosphorus release risk in farmland .Acidic purple soil has a lower Qm ,MBC and a higher P desorption capacity than neutral and calcareous soil ,w hich indicates that acidic purple soil are easier to lose P than the other two types of purple soil .The multiple regression analysis shows that there are no signifi-cant linear correlations between soil physicochemical properties and the phosphorus adsorption-desorption characteristics ,but factor analysis shows that pH ,organic matter and soil texture have direct impact on soil phosphorus adsorption-desorption ability .