Amendments with organic and industrial wastes stimulate soil formation in mine tailings as revealed by micromorphology Zanuzzi, A.; Arocena, J.M.; van Mourik, J.M.; Faz Cano, A. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Mine tailings are inhospitable to plants and soil organisms, because of low pH and poor soil organic matter contents. Vegetation establishment requires a soil system capable of supporting the nutrient and water requirements of plants and associated organisms. The objective of this study was to understand the influence of added organic and industrial wastes to the formation of soils in degraded landscapes left behind by past mining activities. Specifically, we stimulated the build up of soil organic matter (SOM) and the accumulation of calcite in mine tailing deposits. We amended field experimental plots with pig manure (PM), sewage sludge (SS) in combination with blanket application of marble wastes (MW). Soil samples were collected for physical and chemical analyses, two years after the addition of industrial wastes. Three years after amendments, we took undisturbed samples for micromorphological analysis. Soil pH increased from 2.7 to 7.4 due to dissolution of calcite from MW amendment. The acidity in tailings and low rainfall in the study area precipitated the secondary calcite as infillings within the 0-4 cm layer. Total organic carbon (TOC) increased from 0.86 to 2.5 g TOC kg − 1 soil after 24 months since the application of amendments. The build up of SOM resulted to stable SOM-calcite complex as dense incomplete infillings mixed with secondary calcite, and cappings on calcite particles from MW addition. These SOM cappings provide water and nutrient to support initial seedling establishment in mine tailings. We attribute the granular structure of amended materials to soil organisms (e.g., earthworm activity) involved in the decomposition of plant materials. We suggest that any organic matter amendments to acidic mine tailing deposits must be combined with calcium carbonate-rich materials to accelerate the build up of SOM to accelerate the establishment of functional ecosystem characterized by, among others, the presence of healthy soils with granular microstructure.

Seeds, young plants and adult plants of the perennial Mediterranean leguminous shrub Dorycnium pentaphyllum Scop. were exposed to Cd (1-100 lM) or Zn (10-10,000 lM) on nutrient solution. This species is resistant to Cd and Zn at different phenological stages. The lowest doses of Zn and Cd improved seed germination and young seedling growth, while only the highest doses of both heavy metals inhibited germination and decreased growth. High doses of Cd reduced seed imbibition and young seedling water content, while Zn did not. Osmotic adjustment was more efficient in Zn-treated young plants than in Cd-treated ones, while chlorophyll concentrations decreased in the former but not in the latter. Those differences were not observed anymore in adult plants. Exclusion processes were more efficient at the adult stage than at the young seedling stage and were more marked in response to Zn than to Cd. It is concluded that D. pentaphyllum could be used for phytostabilization of heavy metal-contaminated areas. The physiological strategies of tolerance, however, differ according to the age of the plants and the nature of the metal.

Metal mobility and the fractionation of elements and thus the biological uptake of Zn, Pb and Cd by plants were investigated using a simplified analytical procedure for soluble and bioavailable metals using a four-step sequential extraction procedure. Results showed that there was a low proportion of immediately soluble metals, as well as a high proportion of metals that could be released and would so be available for plant uptake. In the sequential extraction procedure, considering the total partition, there was a large proportion of Pb, Cd and Zn extracted in a readily mobile form. In acidic soils the content of metals in ready mobile form (exchangeable-bound to carbonates as well as to Fe and Mn oxides) and bound to organic matter constitutes an important source of potentially available elements. The same pattern was observed in alkaline soils, where almost 80% of the metals could be remobilized and be potentially available to plants. Knowing the metal partitioning and mobility of heavy metals it is very important for evaluating the phytoremediation efficiency.

Cadtnium is s toxic pollutant, hur the relationships hetween morphological modifications and Cd accumulation in different organs, as well as the physiological impact of accumulated Cd in leaves of different ages, remain an open question. We compared Cd concentration in the primary branches and main stems of the perennial shrub Zygophyllum fabago L. Six weeks of treatment with 10 /xM Cd inhibited stem elongation and axillary bud development, and Cd accumulated to a higher level in the oldest leaves on the main stem than in ramification leaves. Although ramifications always contained lower amounts of Cd than main-stem leaves, ramification leaves were more sensitive to the pollutant. While Cd accumulation induced stomatal closure, a decrease in carbon isotope discrimination, and an increase in the water use efficiency of main-stem leaves, an inverse trend was recorded for primary-branch leaves. Cadmium induced an increa.se in chlorophyll concentration in the main stem but decreased it in latera! branches. Bypass flow, quantified by tbe 8-hydroxy-l,3,6-pyrenetrisulfonic acid trisodium salt fluorescent dye, correlated significantly witb Cd accumulation in leaves, suggesting tbat it contributes to Cd translocation tbrough the transpiration stream. Our study demonstrates tbat Cd absorbed by the roots Is unevenly distributed in tbe shoot leaves. Accumulated toxic ion, however, is not the only factor conditioning the organ response; for example, the physiological status of the tissues in relation to tbe leaf ontogeny may direaly influence tbe extent of metabolic disorders resulting from Cd accumulation.