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Cadmium (Cd) is a hazardous heavy metal that poses several problems to human health and the environment requiring remediation to reduce such risks. In situ remediation is a promising, low-cost strategy for immobilizing heavy metals in soil. Using soil materials from a natural forest and from a mining area near the forest, Cd released kinetics (by the stirred flow method) combined with sequential chemical extraction as a function of the application of rates of biochar, phosphate, calcite, and biosolids were investigated through a series of laboratory experiments. Among the amendments, biochar and biosolids were more effective in reducing Cd desorption kinetics in forest soil than in mine soil. Both treatments increased the Cd associated with organic matter (OM), which suggests that part of the Cd was immobilized by the organic compounds that were applied to the soil. Phosphate application to both soils reduced Cd desorption kinetics. Column leaching carried out using the mine soil showed that a quarter and a half of the phosphorus (P) rate increased Cd leaching, while the higher rate decreased Cd leaching compared to untreated forest soil. Treatment with calcite was more effective in decreasing desorption kinetics of Cd in the mine soil in the initial time period (30 min), while the same was observed in the forest soil only after 120 min. In both soils, the Cd associated with OM increased after the addition of calcite as a result of the increase in the negative charge on the surfaces of the OM. [ABSTRACT FROM AUTHOR]

Aims: Seed germination is one of the most important processes in plant biology and ecology because it determines the timing and magnitude of seedling emergence events every growing season influencing community dynamics. Our aim was to determine whether polyethylene glycol (PEG) solutions simulate soil water potential accurately and recreate germination responses to soil water availability. Methods: In this study, we compared seed germination of four plant species in PEG and four soils with different textures under six water potentials under controlled laboratory conditions. Results: Total seed germination for all species significantly differed between soil and PEG under the same water potentials, as well as among soil water potentials for each of PEG and soil materials. Due to the inconsistent total germination associated with soil water potential, we evaluated unsaturated soil hydraulic conductivity (Kh) as a predictor of germination. The germination of all species followed the same response to Kh. Germination rate (GR50) was more directly related to water potential than total germination, but Kh provided a more robust description of GR50 across species and soils than PEG-osmotic potentials. Conclusions: Our findings showed that Kh is a more informative variable to predict both total seed germination and germination rate in soil, and caution must be used when considering results obtained using PEG solutions to infer germination behavior under field conditions. [ABSTRACT FROM AUTHOR]