Breakdown Characteristics Of Aggregates Derived From Quaternary Red Clay Under Different PH And Electrolyte

Slope erosion is dominantly controlled by processes of aggregate breakdown, the slope erosion and sediment yield are related to aggregate stability. Tillage, fertilizer and other agricultural activities change the soil pH, electrolyte concentration and composition, even more affect the stability of soil aggregates. Hilly red soil region located in the tropical and subtropical play an extremely important role in agriculture and economy development in China. However, since the soil erosion is very serious, it is important to study breakdown characteristics of red soil aggregates under different pH and electrolyte conditions for learning red soil erosion mechanisms and utilizing red soil resources rationally. Laboratory experiments are on the basis of the LB-method to study red soil derived from Quaternary red clay. This study was designed to reveal aggregate breakdown characteristics under different pH and electrolyte, and then discussed the breakdown mechanisms of H＋and electrolyte on the red soil aggregates. Based on LB-method, aggregates were treated by applying fast wetting and alcohol pre-wet under different pH, electrolyte type and concentration. Broken aggregates granularity and soil aggregates MWD were discussed. The main results were listed as following:1, Aggregates MWD change with electrolyte types and concentration.(1) Soil aggregates MWD decreases with the increase of electrolyte concentration, and then become stabilized. The minimum electrolyte concentration that aggregate MWD does not change with is known as the critical concentration. This study found the critical concentration was0.10mol L’1. The result showed that index of correlation between the MWD of soil aggregate and electrolyte concentration is significant.(2) The effect of the electrolyte on the soil aggregates change with different cation in solution when the anion is the same. The effect of divalent cation is greater than monovalent cation. The cation of small hydrated radius is greater than that of larger hydrated radius. The effects of the three kinds of electrolyte on red soil aggregate is in the order of MgCl2> KCl> NaCl.(3) The effect of electrolyte on soil aggregates is mainly reflected by the decrease of large aggregates and increase of small aggregates. The mass percentage of broken aggregates in diameter of0.5-0.25mm is hardly affected by electrolyte concentration, the addition and reduction under different electrolyte concentration is nearly equal. (4) The content of the free Fe and Al oxides in broken aggregates treated by different electrolyte were little different.2, If the pH is in the range of3.0-10.0, aggregate MWD will don’t change with the pH under fast wetting and alcohol pre-wet treatment.