Virgil Iordache

Calcium signaling mediates the response to cadmium toxicity in Saccharomyces cerevisiae cells

The involvement of Ca2+ in the response to high Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+ was investigated in Saccharomyces cerevisiae. The yeast cells responded through a sharp increase in cytosolic Ca2+ when exposed to Cd2+, and to a lesser extent to Cu2+, but not to Mn2+, Co2+, Ni2+, Zn2+, or Hg2+. The response to high Cd2+ depended mainly on external Ca2+ (transported through the Cch1p/Mid1p channel) but also on vacuolar Ca2+ (released into the cytosol through the Yvc1p channel). The adaptation to high Cd2+ was influenced by perturbations in Ca2+ homeostasis. Thus, the tolerance to Cd2+ often correlated with sharp Cd2+‐induced cytosolic Ca2+ pulses, while the Cd2+ sensitivity was accompanied by the incapacity to rapidly restore the low cytosolic Ca2+.

The Role of Organic Matter in the Mobility of Metals in Contaminated Catchments

We have applied a concept framework for scale-specific processes in order to characterize the role of the organic matter in the mobility of metals. At very small scale, we identified roles by immobilization of metals (immobilization in litter, immobilization in soil aggregates, dissolved organic carbon chelates in fine pores), by mobilization of metals (organochemical weathering, soluble chelates, organocolloids, free enzymatic degradation of immobile organic carbon), and by supporting the mobilization or immobilization of metals by other compartments at the same scale (energy source for microorganisms, buffering of soil solution). These roles have effects on the fluxes of metals and can be characterized at a larger scale: transfer of metals to plants and to lower soil layers by hydrological fluxes. At scales ranging from contaminated sites to watershed, we identified the same roles as above, that however up-scaled differently as a function of the site type (contaminated soil in the slope area, mining dump or tailing dam, contaminated soil in the floodplain, contaminated stream ecotone), with corresponding effects on the fluxes of metals subsoil and groundwater to surface water, on the transfer to surface water by lateral types of flows, transfer to floodplains, and volatilization (also differentiated as a function of the type of site). The literature is comprehensively screened for each case. The extent and consistency of the available scientific knowledge decrease with the increase of the system scale and complexity. Based on this analysis, multiscale biogeochemical and ecotoxicological research directions are suggested.

Coupled pot and lysimeter experiments assessing plant performance in microbially assisted phytoremediation.

We performed an experiment at pot scale to assess the effect of plant growth-promoting bacteria (PGPB) on the development of five plant species grown on a tailing dam substrate. None of the species even germinated on inoculated unamended tailing material, prompting use of compost amendment. The effect of inoculation on the amended material was to increase soil respiration, and promote elements immobilisation at plant root surface. This was associated with a decrease in the concentrations of elements in the leaching water and an increase of plant biomass, statistically significant in the case of two species: Agrostis capillaris and Festuca rubra. The experiment was repeated at lysimeter scale with the species showing the best development at pot scale, A. capillaris, and the significant total biomass increase as a result of inoculation was confirmed. The patterns of element distribution in plants also changed (the concentrations of metals in the roots of A. capillaris and F. rubra significantly decreased in inoculated treatments, while phosphorus concentration significantly increased in roots of A. capillaris in inoculated treatment at lysimeter scale). Measured variables for plant oxidative stress did not change after inoculations. There were differences of A. capillaris plant–soil system response between experimental scales as a result of different substrate column structure and plant age at the sampling moment. Soil respiration was significantly larger at lysimeter scale than at pot scale. Leachate concentrations of As, Mn and Ni had significantly larger concentrations at lysimeter scale than at pot scale, while Zn concentrations were significantly smaller. Concentrations of several metals were significantly smaller in A. capillaris at lysimeter scale than at pot scale. From an applied perspective, a system A. capillaris—compost—PGPB selected from the rhizosphere of the tailing dam native plants can be an option for the phytostabilisation of tailing dams. Results should be confirmed by investigation at field plot scale.

Assessing the Effect of Disturbances on Ectomycorrhiza Diversity

Ectomycorrhiza (ECM) communities can be described on a species level or on a larger scale at an ecosystem level. Here we show that the species level approach of successional processes in ECM communities is not appropriate for understanding the diversity patterns of ECM communities at contaminated sites. An ecosystem based approach improves predictability since different biotic and abiotic factors are included. However, it still does not take into account the hierarchical structure of the ecosystem. We suggest that diversity patterns of ECMs communities in forests can best be investigated at three levels. This hypothetical approach for investigation can be tested at sites of secondary succession in areas contaminated with metals. Once the diversity patterns are appropriately described by a hierarchical ecosystem approach, to the species level is used to explain these patterns by populational and ecotoxicological mechanisms.

Environmental metal contamination and health impact assessment in two industrial regions of Romania

We investigated two Romanian industrial regions- Copşa Mică and Zlatna, to assess the current situation of soil pollution and bioaccumulation of Pb, Cd, Cu and Zn in different vegetable species and possible risks to consumers. Both total and mobile forms of the metals were determined in soil samples, and metal content in the edible parts of root vegetable samples was also assessed. The concentrations of Pb and Zn in soil were higher in Copşa Mică than in Zlatna (566mg/kg vs 271mg/kg for Pb and 1143mg/kg vs 368mg/kg for Zn)·The metal mobility in soil from Copsa Mica decreases in the order Zn>Cu>Cd>Pb (1.88mg/kg, 0.40mg/kg, 0.22mg/kg, 0.16mg/kg, respectively), while in Zlatna, the order was Cu>Zn>Pb>Cd (0.88mg/kg, 0.29mg/kg, 0.04mg/kg, 0.01mg/kg, respectively), apparently depending on metal and soil conditions. In Copsa Mica, the amount of Pb and Cd in vegetable samples exceeded the maximum permissible limits in carrots (median concentration 0.32mg/kg for Pb and Cd) and in yellow onions (median concentration 0.24mg/kg for Cd). In Zlatna region, the content of Cd exceeded the maximum limits in yellow onions (median concentration 0.11mg/kg). The amount of Pb was higher than the maximum acceptable level in carrots from the Zlatna region (median concentration 0.12mg/kg). Cu and Zn levels were within the normal range in all vegetable samples. In the Zlatna region, the transfer factors for Pb and Cd were higher in carrots (median values of 9.9 for Pb and 21.0 for Cd) compared to carrots harvested in Copsa Mica (median values of 4.0 for Pb and 2.0 for Cd). Daily intake rates of metals through local vegetable consumption exceeded the limit values established by the European Food Safety Authority for Pb (1.2 to 2.4 times) and Cd (5.5 to 9.1 times) in both regions, with potential adverse health effects for the local population. The results highlight the need for total soil remediation action before fruit and vegetables produced in these polluted areas can be safely consumed.

A Conceptual Framework for Up-Scaling Ecological Processes and Application to Ectomycorrhizal Fungi

After reviewing the limits of the current approaches, we introduce an analytical framework for up-scaling analyses of ecological processes. The framework attempts to produce a conceptual unification and leads to a ten-step approach for up-scaling from a source to a target scale. The literature on ectomycorrhizal fungi is then screened following each up-scaling step. We conclude that one needs to construct four (pseudo) hierarchical levels in order to understand the ecological role of ectomycorrhizal fungi in the ecological productivity of ecosystems (scale of 104-105 m2) and one more level, if one is interested in evolutionary processes such as gene flow or speciation. The modularization scales for understanding the role of ectomycorrhizal fungi are those applicable to bacteria (10-6-10-4 m2), fungi (functional dynamic modules occupying surfaces of tenths of m2, and a tree plot of 400–900m2), epigeous fungivorous invertebrates and mammals (104-106 m2), and, for speciation, to small catchments of several hundreds of km2. The analyses showed that the source for up-scaling has to be a plot of 400–900m2. This plot has an associated homomorphic model with a maximum number of nine functional dynamic modules for the structural and functional modeling of ectomycorrhizal communities. Only one modeling step is needed for up-scaling from the source scale (plot) to the ecosystem scale, but the model’s construction involves the previous construction of several up- and down-scaling models in order to quantify the effects of smaller- and larger scale organisms on fungi. The existing knowledge limits the up-scaling of processes, especially with respect to the available mathematical models, which in turn are limited by the data required.

The influence of environmental variables on soil mite communities (Acari: Mesostigmata) from overgrazed grassland ecosystems – Romania

Abstract In 2013–2014, the soil mite communities from six overgrazed grassland ecosystems located in the Trascău Mountains, Romania, were investigated. Forty-six species were identified, with 645 individuals. Some abiotic factors from soil were measured (soil temperature – T, soil water content – H, soil acidity – pH, carbon content – C, total nitrogen – Nt, and C/Nt ratio). Significant statistical differences were obtained between environmental factors. Using a canonical correspondence analysis of mite species abundance, environmental variables and habitats, strong relationships between investigated factors were established.

Upscaling the Biogeochemical Role of Arbuscular Mycorrhizal Fungi in Metal Mobility

In this chapter, we introduce a concept relating the biogeochemical role of microorganisms explicitly to cross-scale effects in the frame of an approach we termed objective scale integrated biogeochemistry. By objective, we mean that the scale of analyses is that of the environmental objects involved in the cycling and is not assumed a priori based on human (institutional) interests. By integrated, we refer to the consideration of multielement fluxes (of nutrients and toxic elements) through the biotic and abiotic compartments controlling productivity of the system. After a critical analysis of the knowledge on arbuscular mycorrhizal fungi (AMF) relevant for estimating their biogeochemical role in the mobility of metals, we propose a methodology for characterizing this role and underline the practical limitations linked to current state of knowledge concerning AMF. These limitations are due to basic issues such as estimating the dimension of a physiological individual, the size in space of a population of AMF, and the species diversity of AMF in the hyphal compartment. We then focus on an example of myco-/phytoremediation using selected plants and commercial inocula. A multi-scale (pot, lysimeter, field plot) experimental approach for studying the biogeochemical role of AMF in metal mobility was developed, tackling scale-specific issues. The main findings of the operational research program are summarized.

Water ow on vegetated hill. 1D shallow water equation type model

Abstract A mathematical model for the water ow on a hill covered by variable distributed vegetation is proposed in this article. The model takes into account the variation of the geometrical properties of the terrain surface, but it assumes that the surface exhibits large curvature radius. After describing some theoretical properties for this model, we introduce a simplified model and a well-balanced numerical approximation scheme for it. Some mathematical properties with physical relevance are discussed and finally, some numerical results are presented.

Hyperaccummulation: A Key to Heavy Metal Bioremediation

As environmental issues become more and more stringent, the biotechnological approaches to maintain clean environments are receiving increasing attention. Heavy metal pollution is of great concern as it ultimately forces heavy metals into the food chain leading to serious ecological and health problems. Removal of excess heavy metals from contaminated sites could be achieved by means of organisms that bioaccumulate heavy metals without developing toxicity symptoms, features that are characteristic to hyperaccumulating plants. This review focuses on the applicability of hyperaccumulation phenomenon to heavy metal bioremediation as well as on the possibility to extend the hyperaccumulation concept to organisms other than plants.