Effects Of Chemicals On Soil Aggregates Stability And Their Other Physical Characters

Soil is similar to the living forms has obvious characteristics of life, and aggregates are important “organs” of the body to maintain its life. Stable soil aggregates are important material basis in coordinating gas, heat, water and fertilizer of soil and adverse natural environmental, and creating comfortable environment for the growth, also resist the violations of natural environment on the soil, such as water and wind erosion, to ensure the Habitat eco-friendly environment. Natural soil aggregates, particularly the stability is of great concern to the academic community. Based on the current situation of a large number of chemical substances into farmland, as well as the extent of irrigation water in different places, such as chemical contamination, making the destruction of soil aggregates, soil compaction and soil compaction widespread occurrence, quality of soil structure decline, it is highly necessary to study the ability of soil aggregates to resist all kinds of traits chemical destruction. Based on the concept of stability of soil aggregates hydraulics, mechanical stability and biological stability, "chemical stability of soil aggregates" is proposed, referring to the ability to resist the effects of chemical substances while maintaining good reunion and its physiological function.Because the soil solution is a dilute solution containing complex chemical composition, but not the pure water in any case, the impacts of chemicals on soil aggregates are multifaceted, they completely different from the classical soil science highlighted in the water stable aggregates concepts and effects. The type and amount of various chemicals in solution effects on the role of soil aggregates should become an important task and content of soil science; it is completely different from the stability effects of pure water on soil aggregates in classical soil science.Based on the above problems, a representative of the black soil of northeast China, Lou soil of Guanzhong area, red soil of south China were chosen as the research object, using the indoor simulation method, respectively, pure water and different concentrations of inorganic and organic salt solutions for the medias. Soil aggregates composition, expansion, saturated hydraulic conductivity and permeability characteristics were determined to explore the mechanism of exogenous chemicals affect different types of cemented soil aggregate stability, access to the following conclusions:(1) Water stability of soil aggregates is closely related to the type of soil grouting agents, composition and stability of soil aggregates obtained through wet-sieving in pure water significantly different. Long-term effects of chemicals on soil aggregates so that the composition of the soil aggregates constantly undergoing dynamic changes, the changes sometimes are scattered, but also sometimes reunion. The dynamic equilibrium always develops towards to a certain direction eventually.(2) The level of soil fertility is one of the main factors affecting soil aggregate stability, mechanical stability and water stability of soil aggregates showed significant correlation to soil fertility levels, higher fertility soil had more stable aggregates. Composition of soil aggregates response to the degree of nitrogen solution also exists a significant correlation to soil fertility levels, high degree of agglomeration with high fertility soils affected by nitrogen fertilizer solution was weak, and the relatively low degree of agglomeration with low soil fertility response to nitrogen fertilizer solution was more intense. Soil fertility levels play a certain role in mechanical, water and chemical stability of aggregates.(3) The theoretical of impact of different valence cations on soil aggregates stability has long formed. Species and concentration of salt solutions are important factors that affect the stability of aggregates. Salt solution enables water stable aggregates further dispersed, but also to inhibit certain grades of aggregates dispersed, which can be regarded as a protective effect of salt solution on the aggregates.(4) Difference in soil expansion is one of the causes of differences in the stability of soil aggregates. Soil expansion depends not only on the type of clay minerals, in soil aggregates, soil expansion is closely related to the quantity and quality of soil cement material. The linear expansion coefficient of the three tested soils there are some differences in changes over time in water as the medium. Low concentration of sodium chloride solution had no significant effect on the black soil and red soil expansion, but can significantly reduce the rate of expansion of Lou soil. Increasing the salt concentration, the initial expansion rate of red soil and black soil significantly reduced, also the initial expansion rate of Lou soil decreased but not significantly. With different concentrations of ethanol for the three soils as medium, coefficient of linear expansion changed in a wide range, illustrating the effect of ethanol on expansive soils produce can not be ignored.(5) Soil saturated hydraulic conductivity and stable infiltration rate can reflect the stability of soil aggregates macroscopically. Theoretically considered an indicator of the state of soil moisture such as soil saturated hydraulic conductivity and stable penetration rates are " constant", but by the experiments on quality of the solution on soil saturated hydraulic conductivity and stability of the permeation rate, found that the type and concentration of chemical substances contained in the soil solution were important factors in these two soil moisture migration indicators. Experimental results show that the soil saturated hydraulic conductivity and soil infiltration rate is closely related to the stability of soil aggregates composed, and the composition of soil aggregates affected by soil solution chemistry changing state of matter, soil aggregate stability was an important factor to determine changes of stability of soil saturated hydraulic conductivity and permeation rate, the species and quantity of chemicals in the soil solution were important external factors affecting these two indicators.(6) Compare the test results of soil water and chemical stability study, found that water-stable soil aggregates were not necessarily chemical-stable. This is because there are significantly different types of cementing substance in soils. The way and ability of reactions of different salt solutions to the cementation material were different, so the exogenous chemical substances into the soil, differences in chemical stability were significantly among different types of soils. The test results demonstrate the impact of the species and quantity of chemicals in environment on soil aggregate stability can not be ignored.Therefore, the concept and application of "chemical stability" of soil aggregates should become an important content of soil aggregates research system. Meanwhile, the studies on soil aggregates stability and soil moisture transport properties in the past usually use water as a medium, which is not realistic in the soil environment, its scientific deserve further discussions. Establish a standard research system to accurately evaluate the situation and characteristics of soil aggregates will be important research topic on soil physics.