Leaching potential and changes in components of metals in two acidic ferrisols

Two acidic ferrisols, i.e., red soil （RS） and yellow red soil （YRS）, from the vicinity regions of non-ferrous ores in Hunan province of China, were leached with simulated acid rain through artificial column experiments. The results show that the total leaching mass of metals are m（Zn）〉m（Cu）〉m（Cd） from the original soils and m（Cd）〉m（Zn）〉〉 m（Cu） from the contaminated soils with external metals after leaching for 60 d continuously, leaching quantities of Cd and Zn from the contaminated red soil （CRS） are more than that from the contaminated yellow red soil （CYRS）, but for Cu, it is almost the same. The preferential fractions for leaching are mainly in exchangeable forms, and content of exchangeable forms decreases significantly in the contaminated soil profiles. The unstable fractions of Cd, Cu and Zn in the RS and YRS increase significantly with the decrease of pH value of simulated acid rain. Changes of fi, actions of external Cd, Cu, and Zn in the residual CRS and CYRS profiles are significantly affected by the acidity of acid rain, too. After leaching for 60 d continuously, Cd exists mostly in exchangeable form, Cu exists mainly in exchangeable, manganese oxide-occluded and organically bounding forms, and Zn exists in residual in CRS and CYRS profiles. Most of exchangeable Cd and Zn exist only small in surface layer （0-20 cm） and are transferred to the sub-layers, contrarily, Cu accumulates mostly in the topsoil （0-20 cm） with low translocation.

Classification of Ferrallitic Soils in Chinese Soil Taxonomy

The development of the classification of ferrallitic soils in China is reviewed and the classification ofFerralisols and Ferrisols in Chinese Soil Taxonomy is introduced in order to discuss the correlation betweenthe ferrallitic soil classification in the Chinese Soil Taxonomy and those of the other soil classification systems.In the former soil classification systems of China, the ferrallitic soils were classified into the soil groups ofLatosols, Latosolic red soils, Red soils, Yellow soils and Dry red soils, according to the combination of soilforming conditions, soil-forming processes, soil features and soil properties. In the Chinese Soil Taxonomy,most of ferrallitic soils are classified into the soil orders of Ferralisols and Ferrisols based on the diagnostichorizons and/or diagnostic characteristics with quantitatively defined properties. Ferralisols are the soilsthat have ferralic horizon, and they are merely subdivided into one suborder and two soil groups. Ferrisolsare the soils that have LAC-ferric horizon but do not have ferralic horizon, and they are subdivided intothree suborders and eleven soil groups. Ferralisols may correspond to part of Latosols and Latosolic red soils.Ferrisols may either correspond to part of Red soils, Yellow soils and Dry red soils, or correspond to part ofLatosols and Latosolic red soils.

Effect of Heavy Metal Pollution on Potassium Behavior in Typic Udic Ferrisol

The indirect influence of heavy metal contamination of soil on nutrient availability, an important aspect of soil quality, may need to be taken into consideration when determining overall effects of heavy metals. A laboratory experiment was performed to study the effects of combined pollution of Cu, Ph, Zn and Cd on soil K status as indicated by chemical fractions, adsorption-desorption and quantity/intensity (Q/I) relationship of K in a Typic Udic Ferrisol (generally called red soil), by employing uniform design and single factor design. Compared to the control, content of exchangeable K was decreased, but that of soluble K increased in the samples contaminated with heavy metals. Due to heavy metal pollution, potassium adsorption was reduced by 5% to 22%, whereas the desorption percentage of adsorbed K increased by 2% to 32%. The Q/I curves shifted downward, potassium buffering capacity (PBCK) decreased, and equilibrium activity ratio values (ARoK) increased with increasing heavy metal pollution. These influences followed the sequences of Ph>Cu>Zn and combined pollution>single one. Displacement of K from canon exchange sites and decrease in soil CEC due to heavy metals should be responsible for the changes of soil K behaviours. The findings suggest that heavy metal pollution of soil might aggravate the degradation of soil K fertility by decreasing K adsorption and buffering capacity and increasing desorption.