Pollution induced community tolerance (PICT) to Cu2+, and co-tolerance to nanoparticulate Cu, ionic silver (Ag+), and vancomycin were measured in field soils treated with Cu2+ 15 years previously. EC50 values were determined using substrate induced respiration and correlations made against soil physicochemical properties, microbial community structure, physiological status (qCO2; metabolic quotient), and abundances of genes associated with metal and antibiotic resistance. Previous level of exposure to copper was directly (P < 0.05) associated with tolerance to addition of new Cu2+, and also of nanoparticle Cu. However, Cu-exposed communities had no co-tolerance to Ag+ and had increased susceptibly to vancomycin. Increased tolerance to both Cu correlated (P < 0.05) with increased metabolic quotient, potentially indicating that the community directed more energy towards cellular maintenance rather than biomass production. Neither bacterial or fungal community composition nor changes in the abundance of genes involved with metal resistance were related to PICT or co-tolerance mechanisms.

Intra-specific variability of root biomass production (RP) of six rooted macrophytes, i.e. Juncus effusus, Phragmites australis, Schoenoplectus lacustris, Typha latifolia, Phalaris arundinacea, and Iris pseudacorus grown from clones, in response to Cu exposure was investigated. Root biomass production varied widely for all these macrophytes in control conditions (0.08 μM) according to the sampling site. Root biomass production of T. latifolia and I. pseudacorus in the 2.5–25 μM Cu range depended on the sampling location but not on the Cu dose in the growth medium. For P. australis, J. effusus, S. lacustris, and P. arundinacea, an intra-specific variability of RP depending on both the sampling location and the Cu-dose was evidenced. This intra-specific variability of RP depending on the sampling location and of Cu-tolerance for these last four species suggests that Cu constitutive tolerance for all rooted macrophytes is not a species-wide trait but it exhibits variability for some species.

Recently compiled databases facilitated estimation of basin-wide benthic organic biomass and turnover in the Strait of Georgia, an inland sea off western Canada. Basin-wide organic biomass was estimated at 43.1×106kgC and production was 54.6×106kgCyr−1, resulting in organic biomass turnover (P/B) of 1.27×yr−1. Organic biomass and production for sub-regions were predictable from modified organic flux (r2>0.9). P/B declined significantly with increasing modified organic flux, suggesting greater biomass storage in high flux sediments. Biomass and production were highest, and P/B lowest near the Fraser River. Annual basin-wide benthic production was 60% of previously estimated oxidized organic flux to substrates, which agrees with proportional measurements from a recent, localized study.Deviations from expected patterns related to organic enrichment and other stressors are discussed, as are potential impacts to benthic biomass and production, of declining bottom oxygen, increasing bottom temperature and potential changes in riverine input.

Stabilization of sewage sludge (SS) prior to its land disposal may help control the mobility of SS-borne contaminants, particularly potentially toxic metals. We examined the effects of stabilized SS application on soil properties, biomass production, and phytoavailability of Cu and Zn to plants grown in two contrasting soils, Entisol and Aridisol. Stabilized SS mixtures were created by mixing SS in a 3-to-1 ratio with bentonite (B), sugar beet factory lime (SL), brick factory fly ash (BFA), rice straw (RS), water hyacinth (WH), and 50:50 mixture of RS and SL. Mixtures were applied at 50 Mg ha⁻¹, and Sorghum vulgare L. and Eurica sativa were grown in a pot experiment. All the amendments increased plant availability and uptake of both Cu and Zn compared to the unamended control. The application of stabilized SS increased dry plant biomass significantly and decreased DTPA-extractable elements compared to the non-stabilized SS treatment. We conclude that of the six amendments studied, especially sugar beet factory lime (SL) and bentonite (B), are promising for the stabilization of metal-contaminated biosolids and should be tested under field conditions.

The potential use of the arsenic-tolerant woody leguminous species Anadenanthera peregrina (L) Spegazzini for rehabilitating arsenic (As)-contaminated areas was studied. In an As (539.33 mg/kg)-contaminated soil experiment, plants were able to accumulate arsenic in their roots with a low transfer index to the shoot. Inoculation with arbuscular mycorrhizal fungi (AMF) amplified this behavior and improved both biomass production and the phosphorus concentration in the shoot. AMF inoculation not only improved A. peregrina plant growth but also protected the shoot against As toxicity. Aside from the AMF inoculation, the addition of organic matter reduced the soil pH, thus improving the ability of the roots to accumulate arsenic. The majority (81 %) of the variations in As accumulation in A. peregrina roots were explained by the effects of the organic matter and soil pH as well as AMF treatments, as found by a principal component analysis. A. peregrina promoted phytostabilization through As root sequestration. Therefore, A. peregrina plants inoculated with AMF in the presence of organic matter are recommended to rehabilitate degraded areas of soil contaminated with arsenic.

A dose–response study was performed in four commercial clones, Baldo (Populus deltoides), Jean Pourtet (Populus nigra), I-214 (Populus x euramericana) and Villafranca (Populus alba), to investigate the best performing species in terms of metal content and high metal resistance (absence of symptoms) useful in biomass production on contaminated water/land by zinc. Zinc (1 μM as control and 1 mM) was applied for 4 weeks in a hydroponic system. Clone Villafranca was the least damaged, while the most sensitive was clone I-214. The highest zinc concentration in all different parts of plants analysed was recorded in Villafranca > I-214 > Baldo > Jean Pourtet. The higher translocation factor was seen in Baldo, the lowest in Villafranca. Analyses of leaf damage showed a reduction on Chl a in young leaves (96 %) in I-214 stressed plants, whereas in Villafranca, Chl a was about double compared to the control. Regarding other photosynthetic pigments, violaxanthin was significantly correlated to zinc concentration in old leaves. The responses of clones to zinc (Zn) stress were specific: Villafranca was the most resistant, while I-214 showed the highest biomass production under Zn excess. Since these two clones have useful and complementary traits for uptake and detoxification while maintaining high biomass production under Zn excess, they are interesting candidates for understanding the key resistance mechanisms.

Many polluted sites are typically characterized by contamination with multiple heavy metals, drought, salinity, and nutrient deficiencies. Here, an Australian native succulent halophytic plant species, Carpobrotus rossii (Haw.) Schwantes (Aizoaceae) was investigated to assess its tolerance and phytoextraction potential of Cd, Zn, and the combination of Cd and Zn, when plants were grown in soils spiked with various concentrations of Cd (20–320 mg kg⁻¹Cd), Zn (150–2,400 mg kg⁻¹Zn) or Cd + Zn (20 + 150, 40 + 300, 80 + 600 mg kg⁻¹). The concentration of Cd in plant parts followed the order of roots > stems > leaves, resulting in Cd translocation factor (TF, concentration ratio of shoots to roots) less than one. In contrast, the concentration of Zn was in order of leaves > stems > roots, with a Zn TF greater than one. However, the amount of Cd and Zn were distributed more in leaves than in stems or roots, which was attributed to higher biomass of leaves than stems or roots. The critical value that causes 10 % shoot biomass reduction was 115 μg g⁻¹for Cd and 1,300 μg g⁻¹for Zn. The shoot Cd uptake per plant increased with increasing Cd addition while shoot Zn uptake peaked at 600 mg kg⁻¹Zn addition. The combined addition of Cd and Zn reduced biomass production more than Cd or Zn alone and significantly increased Cd concentration, but did not affect Zn concentration in plant parts. The results suggest that C. rossii is able to hyperaccumulate Cd and can be a promising candidate for phytoextraction of Cd from polluted soils.

This study evaluated the effect of alkaline industrial by-products such as flyash (FA) and redmud (RM) on phosphorus (P) mobilisation in abattoir wastewater irrigated soils, using incubation, leaching and plant growth (Napier grass [Pennisetum purpureum]) experiments. The soil outside the wastewater irrigated area was also collected and treated with inorganic (KH₂PO₄[PP]) and organic (poultry manure [PM]) P treatments, to study the effect of FA and RM on P mobilisation using plant growth experiment. Among the amendments, FA showed the highest increase in Olsen P, oxalic acid content and phosphatase activity. The highest increase in Olsen P for PM treated non-irrigated soils showed the ability of FA and RM in mobilising organic P better than inorganic P (PP). There was over 85 % increase in oxalic acid content in the plant growth soils compared to the incubated soil, showing the effect of Napier grass in the exudation of oxalic acid. Both amendments (FA and RM) showed an increase in phosphatase activity at over 90 % at the end of the 5-week incubation period. The leaching experiment indicated a decrease in water soluble P thereby ensuring the role of FA and RM in minimising P loss to water bodies. FA and RM showed an increase in plant biomass for all treatments, where FA amended soil showed the highest increase as evident from FA’s effect on Olsen P. Therefore, the use of FA and RM mobilised P in abattoir wastewater irrigated soils and increased biomass production of Napier grass plants through root exudation of oxalic acid.

Zea mays (L.) is a crop widely cultivated throughout the world and can be considered suitable for phytomanagement due to its metal resistance and energetic value. In this study, the effect of two plant growth-promoting rhizobacteria, Ralstonia eutropha and Chryseobacterium humi, on growth and metal uptake of Z. mays plants in soils contaminated with up to 30 mg Cd kg⁻¹was evaluated. Bacterial inoculation increased plant biomass up to 63 % and led to a decrease of up to 81 % in Cd shoot levels (4–88 mg Cd kg⁻¹) and to an increase of up to 186 % in accumulation in the roots (52–134 mg Cd kg⁻¹). The rhizosphere community structure changed throughout the experiment and varied with different levels of Cd soil contamination, as revealed by molecular biology techniques. Z. mays plants inoculated with either of the tested strains may have potential application in a strategy of soil remediation, in particular short-term phytostabilization, coupled with biomass production for energy purposes.

Growing common duckweed Lemna minor L. in diluted livestock wastewater is an alternative option for pollutants removal and consequently the accumulated duckweed biomass can be used for bioenergy production. However, the biomass accumulation can be inhibited by high level of ammonium (NH₄⁺) in non-diluted livestock wastewater and the mechanism of ammonium inhibition is not fully understood. In this study, the effect of high concentration of NH₄⁺on L. minor biomass accumulation was investigated using NH₄⁺as sole source of nitrogen (N). NH₄⁺-induced toxicity symptoms were observed when L. minor was exposed to high concentrations of ammonium nitrogen (NH₄⁺-N) after a 7-day cultivation. L. minor exposed to the NH₄⁺-N concentration of 840 mg l⁻¹exhibited reduced relative growth rate, contents of carbon (C) and photosynthetic pigments, and C/N ratio. Ammonium irons were inhibitory to the synthesis of photosynthetic pigments and caused C/N imbalance in L. minor. These symptoms could further cause premature senescence of the fronds, and restrain their reproduction, growth and biomass accumulation. L. minor could grow at NH₄⁺-N concentrations of 7–84 mg l⁻¹and the optimal NH₄⁺-N concentration was 28 mg l⁻¹.