酸性条件下干湿循环对黄棕壤崩解性能的影响

Effects of dry-wet cycle on the disintegration performance of yellow brown soil under acidic conditions

明确酸性条件下干湿循环对土壤崩解性能影响,对变化环境下水土保持及生态环境治理具有重要指导意义。为研究酸雨与干湿循环及其共同作用对黄棕壤崩解性能的影响,设置4种酸性程度(pH=3、pH=4、pH=5和pH=7)和8种干湿循环次数(0、1、2、3、4、5、10和15次)对土样进行预处理后开展崩解试验,对比分析酸性条件下干湿循环对黄棕壤密度、崩解稳定时间和崩解指数的影响。结果表明:1)黄棕壤密度随着干湿循环次数和溶液酸性的增加均呈现先增加后趋于稳定的变化趋势。溶液酸性越强,对土壤结构的破坏越强烈,土壤的密度增加就越快。但随着干湿循环次数的增加,溶液酸性对土壤密度的影响趋于稳定。2)黄棕壤的崩解过程曲线呈现出典型的“S型”,可分为缓慢崩解阶段、指数崩解阶段和崩解完成阶段。3)在经历15次酸性条件下干湿循环后,崩解稳定时间延长接近1倍,最大崩解指数下降接近30%。最大崩解指数随着干湿循环次数的增加先增加后逐渐减小,随溶液酸性的增强先减少后增加。4)酸性环境的土壤干湿循环对黄棕壤的密度和崩解性能具有显著影响,其中干湿循环作用影响更大。因此,酸性条件下干湿循环显著影响黄棕壤崩解性能。

[Background]China has become the third-largest acid rain area after Europe and North America due to the increasingly serious air pollution.The magnitude of the impact of acid rain on the soil is directly related to the quality of the entire ecological environment,and many useful results have been obtained.The individual effect of dry-wet cycle or acidity on the physical and chemical properties of soil have been widely investigated.However,there is limited studies on their combined effects on soil disintegration performance,despite the soil may suffer dry-wet cycle under acidic condition in nature.[Methods]The yellow-brown soil,a typical soils in the Three Gorges Reservoir area,was collected from Yichang as the research object.In the laboratory,the collected soil samples were broken up gently with hands into small clods,by following their natural structures,to pass a five mm sieve;and then the impurities,such as pebbles,were manually removed,and air-dried for further use in the research.Four acidities(pH=3,pH=4,pH=5 and pH=7 refer to extremely strong acid rain,strong acid rain,weak acid rain and no acid rain condition,respectively)combined with eight dry-wet cycles(0,1,2,3,4,5,10 and 15 times)were set for this research.And the disintegration test was carried out after pretreatment.The duration of the disintegration experiment was 20 min or stopped until all the soil was disintegrated.The effect of dry-wet cycle on the soil bulk density,disintegration stability time and disintegration index under acidic conditions were compared and evaluated.[Results]1)The bulk density gradually increased with increasing in the number of dry-wet cycle or the acidity of the acid solution until reaching a maximum,and then it levelled off.The stronger the acidity,the more serious the damage to the soil structure,resulting in the increasing of soil bulk density.The influence of the acidity on the bulk density gradually stabilized with the increase of the number of dry-wet cycles.2)The disintegration process curve of yellow-brown soil showed a typical“S-shape”with three stages including the slow disintegration stage,absorption-exponential disintegration stage and disintegration completion stage.3)The disintegration stability time prolonged by nearly double while the maximum disintegration index dropped by nearly 30%after 15 times of acid drying-wet cycle.The maximum disintegration index of yellow-brown soil had an increasing trend followed a gradually reduction with the increase of the number of dry-wet cycles,while had a decreasing trend followed a gradually increment with the increase of the acidity of the acid solution.4)The dry-wet cycle and acidity had a significant impact on the bulk density and disintegration of yellow-brown soil,and the contribution of dry-wet cycle effect was more than those of acidity and their combined effect.[Conclusions]The disintegration performance of yellow-brown soil demonstarted obvious change due to dry-wet cycle under acidic condition.The research may strengthen the understanding of the disintegration properties of yellow-brown soil.