Implications of spatial heterogeneity of tailing material and time scale of vegetation growth processes for the design of phytostabilisation Paula Constantinescu a , Aurora Neagoe a,1 , Andrei Nicoară a , Anja Grawunder b , Stelian Ion c , Marilena Onete d , Virgil Iordache a, ⁎ ,1 a Research Centre for Ecological Services (CESEC), University of Bucharest, Aleea Portocalelor no. 1-3, 060101, Romania b Institute of Geosciences, Friedrich Schiller University, Burgweg 11, 07749 Jena, Germany c “Gheorghe Mihoc - Caius Iacob” Institute of Statistical Mathematics and Applied Mathematics, Romanian Academy, Calea 13 Septembrie no. 13, 050711 Bucharest, Romania d Bucharest Institute of Biology, Romanian Academy, Splaiul Independentei no. 296, Bucharest, Romania HIGHLIGHTS • Processes occur at different scales in the phytostabilization of tailing dams. • We used pot, lysimeters and field plot experiments to investigate these processes. • Zeolitic tuff and Trifolium fertilizer in combination improved plant perfor- mance. • Plant performance depended on toxic elements, phosphorus and time. • We propose a remediation methodol- ogy accounting for the time scale of effects. GRAPHICAL ABSTRACT abstract article info Article history: Received 12 April 2019 Received in revised form 17 July 2019 Accepted 18 July 2019 Available online 19 July 2019 Editor: Filip M.G.Tack Phytostabilisation projects for tailing dams depend on processes occurring at spatial scales of 10 6 m 2 and at de- cadal time scales. Most experiments supporting the design and monitoring of such projects have much smaller spatial and time scales. Usually, they are only designed for one single scale. Here, we report the results of three coupled experiments performed at pot, lysimeter and field plot scales using six sampling periodstimes from 3 to 20 months. The work explicitly accounts for the sampling times when evaluating the effects of amendments on the performance of plants grown in tailing substrates. Two treatments with potentially complementary roles were applied: zeolites to decrease availability of Cd, Cu, Pb and Zn and green fertilizer to increase the avail- ability of nutrients. Zeolites have a positive influence on plant development, especially in the early stages. Anal- yses of the pooled datasets for all sampling times revealed the possibility of predicting plant physiological variables, such as protein concentrations, pigments and oxidative stress enzyme activities, as a function of the fac- tors extracted by principal component analysis from the metal concentrations in plants, phosphorus concentra- tions in plants, and sampling times. Two potentially general methodological rules were extracted: account for the spatial geochemical variability of tailings, and cover the broadest possible range of time scales by experiments. Keywords: Agrostis capillaris Tailings Heterogeneity Pot Science of the Total Environment 692 (2019) 1057–1069 Abbreviations: LP, lipid peroxidation; MDA, malondialdehyde; SOD, superoxide dismutase; POD, peroxidase; PCA, Principal Component Analysis; m 2 , square meters; s, seconds; t 1 -t n , times; o, degrees; %, percent; m, meters; g, grams; LOI, loss on ignition; μS cm -1 , micro Siemens per centimetres; μgg -1 , microgram per gram; d.w., dry weight; Stdv, standard deviation; meq 100 g -1 , 100 miliequivalents per 100 g; g cm -1 , grams per centimetres; ml, millilitres; kg, kilograms; ha, hectares; cm, centimetres; PVC, Polyvinyl chloride; EC, electrical conductivity; pH, potential of hydrogen ion activity; ICP-MS, Inductively Coupled Plasma- Mass Spectrometry; DRC-e, Dynamic Reaction Cell; CEC eff , effective cation exchange capacity; TC, total carbon; TOC, total organic carbon; XRD, X-ray diffraction; ANOVA, analysis of variance; U mg -1 protein, units per mg protein; Lg, logarithm based on ten; R 2 , coefficient of determination. ⁎ Corresponding author. E-mail addresses: Anja.Grawunder@uni-jena.de (A. Grawunder), virgil.iordache@g.unibuc.ro (V. Iordache). 1 authors with equal contribution in the production of the article https://doi.org/10.1016/j.scitotenv.2019.07.299 0048-9697/© 2019 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv