The role of organic matter and other soil properties in zinc('2+) activity and AB-DTPA-extractable zinc in soils.

摘要

Zinc is a plant micronutrient as well as a potential heavy metal contaminant in soils. In soil solution, the free Zn activity determines the availability of Zn as a micronutrient and its characteristics as a heavy metal contaminant. A better understanding of the mechanism that controls free Zn activity could improve soil treatments of Zn deficiency or toxicity. In this study, Zn 2+ activity (measured by chelation) was related to soil properties for 18 alkaline soils from three farms in eastern Colorado. Organic carbon and pH were statistically significant parameters in a regression with log Zn2+ activity. Principal component analysis and path analysis were studied and applied to these soils. Results of principal component analysis showed that the first principal component, summing clay and total soil Zn and subtracting soil carbon, accounted for 52% of the variability in the soils. Soil pH and inorganic carbon dominated the second principal component, which accounted for 32% of the variability. Results of path analysis showed that direct effects of pH, total soil Zn, and organic carbon are important in predicting free Zn activity in these soils. Indirect effects of clay through organic carbon, of inorganic carbon through pH, and between pH and organic carbon were also important.;Results from statistical analyses indicate that adsorption of Zn on organic matter may control Zn solubility in soils. To further explore this potential mechanism, Zn adsorption to organic matter was modeled using the chemical equilibrium model, MINTEQA2, and model results were compared to experimental data from the three Colorado farms. Experimental and model results were in close agreement. Adsorption onto organic matter may control Zn solubility in acidic to neutral soils, while precipitation may control Zn in alkaline soils.;The AB-DTPA soil test can also be used as a measure of the availability of micronutrients to plants. AB-DTPA-extractable Zn was measured and correlated to soil chemical properties for soil samples described above. Soil organic carbon and total soil Zn were statistically significant parameters in a linear regression with AB-DTPA-extractable Zn. Organic matter and clay contents were positively correlated with AB-DTPA-extractable Zn.