The Comparison Of Soil Geochemical And Mineralogical Features In The Soil Transect From Inner Mongolia To Guangdong

This paper selected China’s Inner Mongolia, Shanxi, Henan, Hunan, and Guangdong regions which from north to south cross the significant temperature and rainfall interval and sampled in soil of granitic parent material systematacially to research soil geochemical and mineralogical distribution characteristics and explore soil chemical component and heavy metal such as Cd, Pb, Zn distrition under different climate conditions. The research results shows that from Inner Mongolia to guangdong, soil geochemical and mineralogical characteristics of the transect overall controlled by climate factors. From north to south, Na₂ O, CaO, MgO content decreased with the increasing of rainfall, but K₂ O content is stable in the process of chemical weathering. Al₂O₃, Fe₂O₃ overall increased with increased rainfall along the Inner Mongolia-Guangdong transect, but Al₂O₃, Fe₂O₃ content in Guangdong are lower than that of Hunan. Variation feature of SiO2 is contrary to Al₂O₃ and Fe₂O₃. The weathering degree is increased along the Inner Mongolia-Guangdong transect with increasing CIA, CIW and decreasing leaching coefficient. Compared to Hunan, the CIA, CIW, leaching coefficient in Guangdong change smaller, while Sa value is increased, which shows that under the condition of high rainfall alkali metal almost disappear, and desilicification and allitization are suppressed. P, Mn, Sr overall negatively correlated with rainfall along the Inner Mongolia-Guangdong transect and they have strong activity in the process of chemical weathering. Se, Th, Rb overall positive correlated with rainfall and they are relatively stable in the process of chemical weathering. Cd, Hg, Pb, As, Zn, Cu and other heavy metal elements are enriched in the soil in a certain range of rainfall, due to the adsorption, but their activity increased under the condition of high rainfall. Soil iron freeness and rainfall are overall positively correlated along the transect, but free irons and coloring iron oxides are positively correlated with precipitation along Inner Mongolia-Hunan while it is negatively correlated along Hunan-Guangdong. Higher freeness in Guangdong area shows it has experienced strong chemical weathering, and the lower free iron oxides and coloring iron oxides content may be connected with dissolution of the iron oxides under the condition of high rainfall.Along the Inner Mongolia-Guangdong transect, magnetic susceptibility and frequency magnetic susceptibility shows significant rainfall dependence. Soil magnetic susceptibility has a particular rainfall inflection point, when the Average annual rainfall less than 1200 mm, the magnetic susceptibility increases with the increasing rainfall and when the average annual rainfall is higher than 1200 mm, the magnetic susceptibility will reduce with the increasing rainfall. Frequency magnetic susceptibility shows overall positive correlation with the average annual rainfall, compared with the magnetic susceptibility, which is a more ideal index to reflect the chemical weathering intensity and the average annual rainfall. Clay mineral composition exist regular change along the Inner Mongolia-Guangdong transect. Along the transect, as rainfall increased, chlorite, illite and montmorillonite turns into kaolinite.