间歇性降雨对土壤团聚体粒级及磷、铜、锌富集的影响

Effect of Intermittent Rainfall on Size Distribution and Phosphorus,Copper and Zinc Enrichment of Soil Aggregates

探讨间歇降雨条件下土壤干湿交替对团聚体粒级动态变化的影响,对加深径流泥沙运移和分选机制的理解、揭示土壤微量元素随地表径流迁移的规律具有重要意义。通过37 d内的5场间歇性人工降雨实验,观测了降雨激发的团聚体破碎过程和降雨间歇段干缩过程导致的团聚体粒径分布的动态变化,并通过分析不同团聚体粒级总磷、铜、锌含量的动态变化,评估了间歇降雨对土壤污染物富集特征的影响。结果表明,间歇性降雨导致的土壤干湿交替引发了剧烈的团聚体粒级周转,团聚体稳定性随实验推移呈总体退化状态,具体体现在>250μm微团聚体的比例随实验推移显著下降,而<250μm微粒的比例显著上升(P<0.05)。团聚体粒径分布的变化引起了不同粒径磷、铜、锌含量的同步变化,三种元素从>250μm向<63μm粒级逐渐转移,造成<63μm粒级内各元素浓度在实验末期达到最高,这意味着间歇性降雨引起的团聚体结构退化和<250μm微粒的增加及微量元素富集会加大水土流失及伴随污染物排放的风险。本研究揭示了间歇性降雨引起的土壤团聚体结构变化及对泥沙分选和元素迁移过程的影响,为土壤侵蚀引起的横向物质运移机制提供了一定的理论参考。

【Objective】Effects of the soil wetting-drying alternations induced by intermittent rainfall on the temporal dynamics of soil aggregate size distribution(ASD)in the soil were studied in this paper,which is of great significance to in-depth understanding of the mechanisms of sediment transport and fractionation and revealing rules of associated trace elements transfer with runoff.【Method】In this study,a field experiment was carried out having the field of Cambisol subjected to five separate artificial rainfall events within 37 days.During the experiment,soil aggregate breakdown process triggered by the rainfall events and dynamic change in particle size distribution of the soil aggregates were observed.And through analysis of dynamic changes in the contents of P,Cu and Zn in soil aggregates of various particle size fractions,evaluation of impacts of intermittent rainfall on enrichment of pollutants in the soil was performed.【Result】Results show that soil wetting and drying cycles caused by the intermittent rainfall triggered drastic turnover in ASD,which consequently declined in stability as a whole with the experiment going on,especially the fraction of>250μm,which as a result decreased in proportion(P<0.05),while the fraction of<250μm increased.Changes in ASD also led concurrently to variations of P,Cu and Zn concentrations in the various aggregate size classes.The three elements gradually moved from aggregates of>250μm to those of<63μm,and peaked in concentrations in aggregates of<63μm towards the end of the experiment.This shows that the intermittent rainfall triggered breakdown of aggregate structure,increased in the fraction of<250μm aggregates,and enrichment of trace elements in the fraction(<250μm),which in turn aggravated the risk of increasing soil and water loss and associated discharge of pollutants.【Conclusion】The experiment revealed how intermittent rainfall affect soil aggregate structure,fractionation of sediments and element transfer processes,which may serve as certain theoretical reference for better understanding the mechanisms of lateral transfer of soil materials caused by soil erosion.