We studied the performance of the AZTI Marine Biotic Index AMBI manipulating input data collected from lagoonal ecosystems. Our data set consisted of macrofaunal abundance and biomass counts gathered at a variety of sites at which the disturbance status was known. Input data were also manipulated using a set of transformations of increasing severity. Biotic indices were calculated using raw and transformed abundance, biomass and production. Among the three categories of AMBI-based indices, medium transformation of data gave the highest correlation with pressures. However, increasing the severity of transformation generally resulted in a decrease of the correlation with environmental factors. The relative importance of ecological groups changed when using abundance or biomass, sometimes leading to an improved ecological status classification. Being biomass and production more ecologically relevant than abundance, using them to derive AMBI-based new indices seems intriguing, at least in lagoonal waters, where the community is naturally disturbed and dominated by opportunists.

Size-fractioned phytoplankton (pico, nano and microplankton) biomass and production were estimated throughout a year at Recife harbor (NE Brazil), a shallow well mixed tropical hypereutrophic estuary with short residence times but restricted water renewal. Intense loads of P-PO4 (maximum 14μM) resulted in low N:P ratios (around 2:1), high phytoplankton biomass (B=7.1–72μgchl-aL−1), production (PP=10–2657μgCL−1h−1) and photosynthetic efficiency (PB=0.5–45μgCμgchl-a−1), but no oxygen depletion (average O2 saturation: 109.6%). Nanoplankton dominated phytoplankton biomass (66%) but micro- and nanoplankton performed equivalent primary production rates (47% each). Production-biomass models indicate an export of the exceeding microplankton biomass during most of the year, possibly through grazing. The intense and constant nutrient and organic matter loading at Recife harbor is thus supporting the high microplankton productivity that is not accumulating on the system nor contributing to oxygen depletion, but supporting the whole system’s trophic web.

Solanum nigrum L., a potential cadmium (Cd) hyper-accumulator, has not currently been investigated to identify if it has a strong simultaneous accumulative ability to Cd, copper (Cu), zinc (Zn), or lead (Pb) in contaminated soils. In this study, a pot culture experiment was conducted to investigate the phytoremediation effects of S. nigrum L. on these heavy metals. The potential hyper-accumulative characteristics of S. nigrum L. were also discussed. The results showed that S. nigrum L. remediation effects were not inhibited by multi-heavy metals in contaminated soil. On the contrary, the height and wet and dry weights of S. nigrum L. increased compared to the control treatments and to treatments using only one heavy metal contaminant. Results from the Cd treatment experiments showed 1.66- and 1.45-fold increases in stem and root levels; there were also 1.24-, 2.17-, and 1.61-fold extraction increases in the leaves, stems, and roots, respectively. The differences found in shoot and root bioaccumulation coefficient (BC) factors for multi-heavy metal (MHM) treatment were higher than for a single Cd treatment. These results indicate that S. nigrum L. could stimulate biomass production and that it has a strong ability to tolerate and accumulate Cd in contaminated soils with Pb, Zn, and Cu. This study shows that the remediation scope for S. nigrum L. is greater than currently believed and that it will also remove Pb, Zn, and Cu while extracting Cd from contaminated soils.

This study investigates the use of sericite beads and microalgae for the removal of heavy metals from acid mine drainage (AMD) and the simultaneous enhancement of biomass productivity. The experiment was conducted over a period of 6 days in a hybrid system containing sericite beads and microalgae Chlorella sp. The results show that the biomass production increased to ~8.04 times its initial concentration of 0.367 g/L as measured by an optical panel photobioreactor (OPPBR) and had a light transmittance of 95 % at a 305-mm depth. Simultaneous percent removal of Fe, Cu, Zn, Mn, As, and Cd from the AMD effluent was found to be 97.78 to 99.26 %. Biomass production was significantly enhanced by removal of heavy metal ions. We thus found that our hybrid system of sericite beads and microalgae was highly effective in removing heavy metal and in enhancing biomass production and could be a useful alternative treatment of AMD.

To select suitable tree species associated with arbuscular mycorrhizal fungi (AMF) for phytoremediation of heavy metal (HM) contaminated area, we measured the AMF status and heavy metal accumulation in plant tissues in a lead–zinc mine area, Northwest China. All 15 tree species were colonized by AM fungi in our investigation. The mycorrhizal frequency (F%), mycorrhizal colonization intensity (M%) and spore density (SP) reduced concomitantly with increasing Pb and Zn levels; however, positive correlations were found between arbuscule density (A%) and soil total/DTPA-extractable Pb concentrations. The average concentrations of Pb, Zn, Cu and Cd in plant samples were 168.21, 96.61, 41.06, and 0.79 mg/kg, respectively. Populus purdomii Rehd. accumulated the highest concentrations of Zn (432.08 mg/kg) and Cu (140.85 mg/kg) in its leaves. Considerable amount of Pb (712.37 mg/kg) and Cd (3.86 mg/kg) were concentrated in the roots of Robinia pseudoacacia Linn. and Populus simonii Carr., respectively. Plants developed different strategies to survive in HM stress environment: translocating more essential metals (Zn and Cu) into the aerial parts, while retaining more toxic heavy metals (Pb and Cd) in the roots to protect the above-ground parts from damage. According to the translocation factor (TF), bioconcentration factor (BCF), growth rate and biomass production, five tree species (Ailanthus altissima (Mill.) Swingle, Cotinus coggygria Scop., P. simonii, P. purdomii, and R. pseudoacacia) were considered to be the most suitable candidates for phytoextraction and/or phytostabilization purposes. Redundancy analysis (RDA) showed that the efficiency of phytoremediation was enhanced by AM symbioses, and soil pH, Pb, Zn, and Cd levels were the main factors influencing the HM accumulation characteristics of plants.

Bioaccumulation of Cd²⁺in soil bacteria might represent an important route of metal transfer to associated mycorrhizal fungi and plants and may have potential as a tool to accelerate Cd²⁺extraction in the bioremediation of contaminated soils. The present study examined the bioaccumulation of Cd²⁺in 15 bacterial strains representing three phyla (Firmicutes, Proteobacteria, and Bacteroidetes) that were isolated from the rhizosphere, ectomycorrhizae, and fruitbody of ectomycorrhizal fungi. The strains Pseudomonas sp. IV-111-14, Variovorax sp. ML3-12, and Luteibacter sp. II-116-7 displayed the highest biomass productivity at the highest tested Cd²⁺concentration (2 mM). Microscopic analysis of the cellular Cd distribution revealed intracellular accumulation by strains Massilia sp. III–116-18, Pseudomonas sp. IV-111-14, and Bacillus sp. ML1-2. The quantities of Cd measured in the interior of the cells ranged from 0.87 to 1.31 weight % Cd. Strains originating from the rhizosphere exhibited higher Cd²⁺accumulation efficiencies than strains from ectomycorrhizal roots or fruitbodies. The high Cd tolerances of Pseudomonas sp. IV-111-16 and Bacillus sp. ML1-2 were attributed to the binding of Cd²⁺as cadmium phosphate. Furthermore, silicate binding of Cd²⁺by Bacillus sp. ML1-2 was observed. The tolerance of Massilia sp. III-116-18 to Cd stress was attributed to a simultaneous increase in K⁺uptake in the presence of Cd²⁺ions. We conclude that highly Cd-tolerant and Cd-accumulating bacterial strains from the genera Massilia sp., Pseudomonas sp., and Bacillus sp. might offer a suitable tool to improve the bioremediation efficiency of contaminated soils.

Fast-growing clones of Salix and Populus have been studied for remediation of soils contaminated by risk elements (RE) using short-rotation coppice plantations. Our aim was to assess biomass yield and distributions of elements in wood and bark of highly productive willow (S1—[Salix schwerinii × Salix viminalis] × S. viminalis, S2—Salix × smithiana clone S-218) and poplar (P1–Populus maximowiczii × Populus nigra, P2—P. nigra) clones with respect to aging. The field experiment was established in April 2008 on moderately Cd-, Pb- and Zn- contaminated soil. Shoots were harvested after four seasons (February 2012) and separated into annual classes of wood and bark. All tested clones grew on contaminated soils, with highest biomass production and lowest mortality exhibited by P1 and S2. Concentrations of elements, with exception of Ca and Pb, decreased with age and were higher in bark than in wood. The Salix clones were characterised by higher removal of Cd, Mn and Zn compared to the Populus clones. Despite generally higher RE content in young shoots, partly due to lower wood/bark ratios and higher RE concentrations in bark, the overall removal of RE was higher in older wood classes due to higher biomass yield. Thus, longer rotations seem to be more effective when phytoextraction strategy is considered. Of the four selected clones, S1 exhibited the best removal of Cd and Zn and is a good candidate for phytoextraction.

Crop irrigation with heavy metal-contaminated effluents is increasingly common worldwide and necessitates management strategies for safe crop production on contaminated soils. This field study examined the phytoavailability of three metals (Cd, Cu, and Zn) in two cereal (wheat, maize) and legume (chickpea, mungbean) crops in response to the application of either phosphatic fertilizer or sewage-derived water irrigation over two successive years. Five fertilizer treatments, i.e. control, recommended nitrogen (N) applied alone and in combination of three levels of phosphorus (P), half, full and 1.5 times of recommended P designated as N₀P₀, N₁P₀, N₁P₀.₅, N₁P₁.₀, and N₁P₁.₅, respectively. Tissue concentrations of Cd, Cu, Zn, and P were determined in various plant parts, i.e., root, straw, and grains. On the calcareous soils studied while maximum biomass production was obtained with application of P at half the recommended dose, the concentrations of metals in the crops generally decreased with increasing P levels. Tissue metal concentrations increased with the application of N alone. Translocation and accumulation of Zn and Cu were consistently higher than Cd. And the pattern of Cd accumulation differed among plant species; more Cd being accumulated by dicots than monocots, especially in their grains. The order of Cd accumulation in grains was maize > chickpea > mungbean > wheat. Mungbean and chickpea straws also had higher tissue Cd concentration above permissible limits. The two legume species behaved similarly, while cereal species differed from each other in their Cd accumulation. Metal ion concentrations were markedly higher in roots followed by straw and grains. Increasing soil-applied P also increased the extractable metal and P concentrations in the post-harvest soil. Despite a considerable addition of metals by P fertilizer, all levels of applied P effectively decreased metal phytoavailability in sewage-irrigated soils, and applying half of the recommended dose of P fertilizer was the most feasible solution for curtailing plant metal uptake from soils. These findings may have wide applications for safer crop production of monocot species when irrigating crops with sewage effluent-derived waters.

This work investigated the accumulation, allocation, and impact of zinc (Zn; 1.0 μM–10 mM) in maize (Zea mays L.) seedlings under simulated laboratory conditions. Z. mays exhibited no significant change in its habitus (the physical characteristics of plants) up to 10–1000 μM of Zn (vs 5–10 mM Zn). Zn tolerance evaluation, based on the root test, indicated a high tolerance of Z. mays to both low and intermediate (or relatively high) concentrations of Zn, whereas this plant failed to tolerate 10 mM Zn and exhibited a 5-fold decrease in its Zn tolerance. Contingent to Zn treatment levels, Zn hampered the growth of axial organs and brought decreases in the leaf area, water regime, and biomass accumulation. Nevertheless, at elevated levels of Zn (10 mM), Zn²⁺ was stored in the root cytoplasm and inhibited both axial organ growth and water regime. However, accumulation and allocation of Zn in Z. mays roots, studied herein employing X-ray fluorimeter and histochemical methods, were close to Zn accumulator plants. Overall, the study outcomes revealed Zn tolerance of Z. mays, and also implicate its potential role in Zn phytoextraction.

Anthyllis vulneraria was highlighted here as a Zn-hyperaccumulator for the development of a pilot phytoextraction process in the mine site of Les Avinières in the district of Saint-Laurent-Le-Minier. A. vulneraria appeared to hyperaccumulate the highest concentration of Zn in shoots with a better metal selectivity relative to Cd and Pb than the reference Zn-hyperaccumulator Noccea caerulescens. A bigger biomass production associated to a higher Zn concentration conducted A. vulneraria to the highest total zinc gain per hectare per year. As a legume, A. vulneraria was infected by rhizobia symbionts. Inoculation of A. vulneraria seeds showed a positive impact on Zn hyperaccumulation. A large-scale culture process of symbiotic rhizobia of A. vulneraria was investigated and optimized to allow large-scale inoculation process. Contaminated shoots of A. vulneraria were not considered as wastes and were recovered as Eco-Zn catalyst in particular, examples of organic synthesis, electrophilic aromatic substitution. Eco-Zn catalyst was much more efficient than conventional catalysts and allowed greener chemical processes.