再生水盐分在亚热带不同土壤中的迁移特性及其差异

Migration characteristics and its differences of reclaimed water salinity in different subtropical soils

为了合理评价再生水灌溉盐分对土壤环境的影响,分析盐溶液淋溶亚热带土壤流出液盐分变化规律及其对土壤化学性质的影响差异,该文采用定水头入渗法,模拟不同浓度钠盐溶液淋溶黏性潮土、沙性潮土、红壤、紫色土、水稻土等5种亚热带地区土壤,并观测土壤流出液电导率(EC)和pH值的差异。试验结果表明:1)高浓度盐溶液对黏粒含量较高的红壤、紫色土、黏性潮土的穿透能力弱于黏粒含量较低的水稻土和沙性潮土。同等浓度水平处理达到相同的穿透程度,酸性土壤(红壤、紫色土、水稻土)能承受更多的低质水量。2)盐分在土壤中的迁移速度主要由土壤理化性质决定,土壤黏粒含量、交换性铝含量会显著减缓盐分在土壤中的迁移能力,而土壤粉粒含量、EC、pH值以及交换性钙、镁含量会促进盐分在土壤中的迁移。盐分更容易穿透碱性土壤(黏性潮土和沙性潮土)而流出,碱性土壤流出液相对EC最大变化速率比酸性土壤高36%。基于Boltzmann函数拟合表明,入渗水盐浓度及土壤理化性质对模型参数有显著影响(P<0.05)。3)土壤化学性质受入渗液盐分浓度的影响程度不仅与土壤本身的化学性质有关,也与土壤质地中的粉粒、黏粒含量有极显著的关系(P<0.01)。各浓度盐溶液对碱性土壤的pH值影响不明显,对酸性土壤的pH值影响较大,其流出液pH值减少1.6～2.6个单位,其中红壤的pH值变化最大,其次为紫色土。入渗液EC高于4.77dS/m的处理对土壤流出液的稳定pH值影响增幅不明显。因此,利用低质水灌溉时要依据土壤理化性质合理限定水中盐浓度。

To evaluate reasonably the effect of reclaimed water irrigation salt in the soil environment,varying salinity in the effluent of salty solution leaching subtropical soil and the effect on soil chemical properties were analyzed.In this paper,five subtropical soils:clay fluvo aquic soil,sandy fluvo aquic soil,red soil,purple soil and paddy soil were selected as the research object.Use the constant head infiltration method to observe the differences in electrical conductivity(EC)and pH of effluent after leaching of soils with different concentrations of sodium salt solution(EC of solutions was 1.96,4.77,9.08,17.25 and 25.06 dS/m,respectively).The results showed that the high concentration salt solution had weaker penetrating ability in red soil,purple soil and clay fluvo aquic soil with higher clay content than paddy soil and sandy fluvo aquic soil with low clay content.The same treatment achieved the same degree of penetration,and acidic soil(red soil,purple soil,paddy soil)can withstand more low quality water.In addition,the migration rate of salinity in the soil was mainly determined by the physicochemical properties of the soil.Soil clay content and exchangeable aluminum content significantly slowed the migration of salinity in the soil,while the soil silt content,EC,pH value and exchangeable calcium and magnesium content promoted the migration of salt in the soil.Salt can easily flow out through alkaline soil(clay fluvo aquic soil and sandy fluvo aquic soil).The maximum change rate of relative EC from the alkaline soil effluent was 36%higher than that of the acidic soil.The concentration of inflow salt had an obvious influence on the relative EC change rate and the penetration process of the red soil effluents,and it mainly affected the relative EC change rate for the purple soil,the clay fluvo aquic soil and the sandy fluvo aquic soil,which mainly affected the lag degree of the penetration process for paddy soil.The Boltzmann fitting showed the infiltration water salt concentration and soil physical and chemical properties had a significant impact on the model parameters(P<0.05).Moreover,the degree of soil chemical properties affected by the salt concentration in the infiltration solution was not only related to its own chemical properties,but also had a very significant relationship with the content of powder particles and clay in the soil texture(P<0.01).The concentration of salt solution had no significant(P>0.05)effect on the pH value of alkaline soil,and had a greater effect on the pH value of acidic soil.The pH of the effluent decreased by 1.6-2.6 units,of which red soil had the greatest change in pH value,followed by purple soil.The influence of infiltration solution with EC higher than 4.77 dS/m on the stable pH value of soil effluent did not increase substantially.Therefore,when irrigating with low quality water,the salt concentration in the water should be sufficiently limited according to the physicochemical properties of the soil.The research results can serve as reference for reclaimed water irrigation and calculation of water and salt transport in subtropical regions.