Departamento de Ingeniería Hidráulica y Ambiental, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago, Chile; Centro de Desarrollo Urbano Sustentable CEDEUS, El Comendador 1916, Providencia, Santiago, Chile.
Departamento de Ingeniería Hidráulica y Ambiental, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago, Chile; Centro de Desarrollo Urbano Sustentable CEDEUS, El Comendador 1916, Providencia, Santiago, Chile.
Sci Total Environ. 2015 Apr 15;512-513:26-35. doi: 10.1016/j.scitotenv.2015.01.038. Epub 2015 Jan 19.
Water erosion is a leading cause of soil degradation and a major nonpoint source pollution problem. Many efforts have been undertaken to estimate the amount and size distribution of the sediment leaving the field. Multi-size class water erosion models subdivide eroded soil into different sizes and estimate the aggregate's composition based on empirical equations derived from agricultural soils. The objective of this study was to evaluate these equations on soil samples collected from natural landscapes (uncultivated) and fire-affected soils. Chemical, physical, and soil fractions and aggregate composition analyses were performed on samples collected in the Chilean Patagonia and later compared with the equations' estimates. The results showed that the empirical equations were not suitable for predicting the sediment fractions. Fine particles, including primary clay, primary silt, and small aggregates (<53 μm) were over-estimated, and large aggregates (>53 μm) and primary sand were under-estimated. The uncultivated and fire-affected soils showed a reduced fraction of fine particles in the sediment, as clay and silt were mostly in the form of large aggregates. Thus, a new set of equations was developed for these soils, where small aggregates were defined as particles with sizes between 53 μm and 250 μm and large aggregates as particles>250 μm. With r(2) values between 0.47 and 0.98, the new equations provided better estimates for primary sand and large aggregates. The aggregate's composition was also well predicted, especially the silt and clay fractions in the large aggregates from uncultivated soils (r(2)=0.63 and 0.83, respectively) and the fractions of silt in the small aggregates (r(2)=0.84) and clay in the large aggregates (r(2)=0.78) from fire-affected soils. Overall, these new equations proved to be better predictors for the sediment and aggregate's composition in uncultivated and fire-affected soils, and they reduce the error when estimating soil loss in natural landscapes.
水蚀是土壤退化的主要原因，也是主要的非点源污染问题。许多研究致力于估计离开农田的泥沙量及其大小分布。多粒径分类水蚀模型将侵蚀土壤细分为不同粒径，并根据从农业土壤得出的经验方程估算团聚体的组成。本研究的目的是评估这些方程在取自自然景观（未开垦）和受火灾影响土壤的土壤样本中的应用。在智利巴塔哥尼亚采集的样本进行了化学、物理和土壤组分以及团聚体组成分析，并与方程的估算值进行了比较。结果表明，经验方程不适用于预测泥沙粒径。细小颗粒（包括原生黏土、原生粉土和小团聚体(<53μm)）被高估，而大团聚体(>53μm)和原生砂被低估。未开垦和受火灾影响的土壤中，泥沙中的细颗粒减少，因为黏土和粉土主要以大团聚体的形式存在。因此，为这些土壤开发了一组新的方程，其中小团聚体定义为粒径在 53μm 和 250μm 之间的颗粒，大团聚体定义为粒径>250μm 的颗粒。新方程的 r(2) 值在 0.47 到 0.98 之间，可为原生砂和大团聚体提供更好的估计值。团聚体的组成也得到了很好的预测，特别是未开垦土壤中大团聚体中的粉土和黏土组分(r(2)=0.63 和 0.83)，以及未开垦土壤中小团聚体中的粉土(r(2)=0.84)和大团聚体中的黏土(r(2)=0.78)。总的来说，这些新方程在未开垦和受火灾影响的土壤中，对于泥沙和团聚体组成的预测效果更好，并且在估算自然景观中的土壤流失时，减少了误差。
