Abstract
Prediction of heavy metal bioavailability in intact soil is important to manage soil pollution risks. We developed a regression model for representative Japanese soils to judge their potential vulnerability to cadmium (Cd) pollution. We added four rates of Cd to 17 sample soils to mimic artificial contamination. After aging the contaminated soils, we measured Cd’s bioavailability using the diffusive gradients in thin-films (DGT) technique. We then evaluated the relationships between bioavailability of Cd ([CdDGT]) and intact soil properties by statistical analyses. Cation exchange capacity (CEC) and pH emerged as significant factors to explain the cadmium bioavailability in Japanese soils. Specifically, lower CEC and lower pH were associated with higher [CdDGT], which poses a higher risk for soil ecosystems. The correlation between pH and [CdDGT] had a high dependence on [CdAdd], whereas that for CEC did not. Regression analysis also showed that the interaction between intact soil pH and spiked concentration ([CdAdd]) had a significant contribution to [CdDGT]. The regression model developed was rationally supported by a biotic ligand model. This simplified but realistic model would be useful in estimating the vulnerability of representative Japanese soils and determining the risk for Japanese soils in relation to Cd contamination.
Highlights
IntroductionCadmium (Cd) is a major contaminant of soils in Japan and many other countries
The aims of this study were to evaluate the relationships between added Cd concentration and Cd bioavailability measured by the diffusive gradients in thin-films (DGT) method as a function of physicochemical properties such as cation exchange capacity (CEC) and pH, and to propose a linear regression model for soil bioavailability that is reasonably applicable to Japanese soils for potential vulnerability assessment
We developed a linear regression model to estimate [CdDGT] in all the experiments based on the [CdAdd], Cation exchange capacity (CEC) of intact soil, and pH of intact soil
Summary
Cadmium (Cd) is a major contaminant of soils in Japan and many other countries. Evaluating the impacts of heavy metals such as Cd in soils is important for ecological risk assessments for soils, facilitating proactive decision making for regulation of soil ecosystems. Some researchers have devised a method to derive “critical limits” or a “critical load” to soil based on potential bioavailability in order to draw a vulnerability map of European soils [1,2,3]. They categorized soil types vulnerable to contamination according to the extent of metal
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