Influence factors and prediction model for soil nickel ecological threshold

Correction with leaching-aging factor should be applied in deriving soil ecological threshold with toxicity data from laboratory toxicity test in order to eliminate the difference of toxicity in field-contaminated soils and that in laboratory amended soils. In the paper the soil ecological threshold for soil nickel was derived with 17 species toxicity data and corrected with leaching-aging factor. The results showed that leaching effect was more significant in the soils with pH>8.5, and the values of leaching factors were all more than 2 except for exceptional soil. Aging effect was more significant in the soil with pH>7.0 and the value of aging factor increased with pH value. Main soil factors controlling soil ecological threshold for nickel were found as soil pH value and soil organic carbon content (OC). The pH value, OC and CEC could explain the nickel ecological threshold variation by 86.2%, 9.0% and 4.1% proportion respectively. The two-factor predictive model based on soil pH and OC were developed and validated for predicting ecological threshold of soil nickel. The results showed that the model could predict ecological threshold for nickel based on soil pH and OC well and the determination coefficient (R2) reached up to 0.972. The model can be applied in predicting nickel ecological threshold for different kinds of soils according to the soil properties.