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To assess the influence of soil properties and aging on the availability and toxicity of zinc (Zn) applied as nanoparticles (Zn oxide [ZnO]-NPs) or as Zn2+ ions (Zn chloride [ZnCl2]), 3 natural soils were individually spiked with either ZnO-NPs or ZnCl2 and incubated for up to 6 mo. Available Zn concentrations in soil were measured by porewater extraction (ZnPW), whereas earthworms (Eisenia andrei) were exposed to study Zn bioavailability. Porewater extraction concentrations were lower when Zn was applied as NPs compared to the ionic form and decreased with increasing soil pH. For both Zn forms and Zn-PW values were affected by aging, but they varied among the tested soils, highlighting the influence of soil properties. Internal Zn concentration in the earthworms (ZnE) was highest for the soil with high organic carbon content (5.4%) and basic pH (7.6) spiked with Zn-NPs, but the same soil spiked with ZnCl2 showed the lowest increase in ZnE compared to the control. Survival, weight change, and reproduction of the earthworms were affected by both Zn forms; but differences in toxicity could not be explained by soil properties or aging. This shows that ZnO-NPs and ZnCl2 behave differently in soils depending on soil properties and aging processes, but differences in earthworm toxicity remain unexplained. [ABSTRACT FROM AUTHOR]

This work evaluated how pine plantations established on old fields and degraded lands influence soil properties in comparison with adjacent unplanted areas that undergo into secondary succession, and native forests, analysing the effects of abiotic variables and stand characteristics in the afforestation process. Thirty-two paired sites (pine plantations versus unplanted areas) and 10 native forests were selected in the SE Spain. In total, 74 soil profiles were studied, and 222 composite soil samples were collected at three different depths. Soil organic carbon, cation exchange capacity, and C : N ratio showed significantly greater values in pine plantations in relation to the unplanted areas (0-5 cm), and the mean values of soil organic carbon, nitrogen (N), C : N ratio, and cation exchange capacity in these pine plantations were similar to those found under native forests. Only K+ concentrations were clearly higher in the native forests than in the other land uses for all depths analysed. Pine plantations in the drier and warmer areas showed lower soil quality in relation to the paired unplanted areas, as well as the younger and denser ones; it may be because under these situations, more time is needed to produce an improvement. In fact, the paired net variations increased with the stand age and/or tree size. In conclusion, pine plantations were in general more efficient in improving parameters related to soil quality, especially in locations with high soil water retention capacity, which in our study area were found at higher and cooler elevations. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]