Removal of high lead concentration by hydroponic cultures of normal and transformed plants of Scirpus americanus Pers.

Lead is a very toxic metal which affects human health. An alternative to remove it from contaminated water is the use of macrophytes, as Scirpus americanus Pers. This species is tolerant to salt and metals and has high biomass. The present research analyzed the capacity of hydroponic cultures of normal and transgenic plants (line T12) from S. americanus to remove high concentrations of lead. The antioxidant response of plants to metal exposure was also measured. The MINTEQ3.1 program was used to define the media composition in order to have the metal available to the plants. According to MINTEQ3.1 predictions, sulfate, phosphate, and molybdenum must be removed from the medium to avoid lead precipitation. Therefore, the plants were maintained in a modified Hoagland solution containing 100, 250, and 400 mg/L lead. The presence of metal did not affect the growth of roots and stems at all concentration tested. The normal and T12 plants accumulated 69,389 mg/kg and 45,297 mg/kg lead, respectively, and could be considered hyperaccumulators. Plant tolerance to lead mainly involved an increase in superoxide dismutase activity and glutathione accumulation. The bioconcentration factor indicated that S. americanus plants bioconcentrated between 192 and 300 times the metal; thus, S. americanus could be used for phytoremediation of water contaminated with a high concentration of lead.

Enhanced Cd-Accumulation in Typha latifolia by Interaction with Pseudomonas rhodesiae GRC140 under Axenic Hydroponic Conditions.

The Typha genus comprises plant species extensively studied for phytoremediation processes. Recently, Pseudomonas rhodesiae GRC140, an IAA-producing bacterium, was isolated from Typha latifolia roots. This bacterium stimulates the emergence of lateral roots of Arabidopsis thaliana in the presence and absence of cadmium. However, the bacterial influence on cadmium accumulation by the plant has not been determined. Moreover, the P. rhodesiae GRC140 effect in Cd phytoextraction by T. latifolia remains poorly understood. In this work, an axenic hydroponic culture of T. latifolia was established. The plants were used to evaluate the effects of cadmium stress in axenic plants and determine the effects of P. rhodesiae GRC140 and exogenous indole acetic acid (IAA) on Cd tolerance and Cd uptake by T. latifolia. Biomass production, total chlorophyll content, root electrolyte leakage, catalase activity, total glutathione, and Cd content were determined. The results showed that Cd reduces shoot biomass and increases total glutathione and Cd content in a dose-dependent manner in root tissues. Furthermore, P. rhodesiae GRC140 increased Cd translocation to the shoots, while IAA increased the Cd accumulation in plant roots, indicating that both treatments increase Cd removal by T. latifolia plants. These results indicate that axenic plants in hydroponic systems are adequate to evaluate the Cd effects in plants and suggest that T. latifolia phytoextraction abilities could be improved by P. rhodesiae GRC140 and exogenous IAA application.

Biosorption removal of benzene and toluene by three dried macroalgae at different ionic strength and temperatures: Algae biochemical composition and kinetics.

Release of low-molecular aromatic hydrocarbons (HC) into natural waters brings severe consequences to our environment. Unfortunately very limited information is available regarding the treatment of these pollutants. This work evaluated the use of brown, green and red macroalgae biomass as biosorbents of benzene and toluene, two of the most soluble HC. Raw seaweed biomasses were completely characterized, then evaluated under different temperatures and ionic strengths to assess their potential as biosorbents and to elucidate the biosorption mechanisms involved. Brown macroalgae registered the highest removal capacities for benzene and toluene (112 and 28 mg·g-1, respectively), and these were not affected at ionic strength < 0.6 M. Langmuir and Sips isotherm equations well described biosorption data, and the pseudo-second order model provided the best fit to the kinetics rate. Hydrocarbons are adsorbed onto the diverse chemical components of the cell wall by London forces and hydrophobic interactions.

Arsenic and lead contamination in soil and in feathers of three resident passerine species in a semi-arid mining region of the Mexican plateau.

The current study aimed at quantifying arsenic and lead in feathers from three passerine species that are residents from areas exposed to mining activities (Toxostoma curvirostre, Campylorhynchus brunneicapillus, and Melozone fusca). Lead and As contents in bird feathers and in superficial soil samples were measured with AAS. Levels of these metals were compared between sites exposed and unexposed to mining. Possible correlations of As and Pb between superficial soil and bird feathers were also investigated. Soil metal concentrations were significantly higher near mining sites, and metal concentrations in bird feathers showed a behavior similar to those recorded for soil samples. Individual birds from polluted sites had higher mean feather metal concentrations in comparison with non-polluted sites; no differences in metal concentrations were recorded among bird species. This work constitutes a basis for monitoring contaminants, and for future toxicological studies attempting to understand the impact that some mining activities may have on bird populations.

Soluble hydrocarbons uptake by porous carbonaceous adsorbents at different water ionic strength and temperature: something to consider in oil spills.

Nowadays, petrochemical operations involve risks to the environment and one of the biggest is oil spills. Low molecular aromatics like benzene, toluene, and naphthalene dissolve in water, and because of their toxicological characteristics, these produce severe consequences to the environment. The oil spill cleanup strategies are mainly designed to deal with the heavy fractions accumulated on the water surface. Unfortunately, very limited information is available regarding the treatment of dissolved fractions.A commercial (Filtrasorb 400) and modified activated carbons were evaluated to remove benzene, toluene, and naphthalene from water, which are the most soluble aromatic hydrocarbons, at different ionic strengths (I) and temperatures (0-0.76 M and 4-25 °C, respectively). This allowed simulating the conditions of fresh and saline waters when assessing the performance of these adsorbents. It was found that the hydrocarbons adsorption affinity increased 12 % at a I of 0.5 M, due to the less negative charge of the adsorbent, while at a high I (≃0.76 M) in a synthetic seawater, the adsorption capacity decreased 21 % that was attributed to the adsorbent's pores occlusion by water clusters. Approximately, 40 h were needed to reach equilibrium; however, the maximum adsorption rate occurred within the first hour in all the cases. Moreover, the hydrocarbons adsorption and desorption capacities increased when the temperature augmented from 4 to 25 °C. On the other hand, thermally and chemically modified materials showed that the interactions between adsorbent-contaminant increased with the basification degree of the adsorbent surface.

Removal and accumulation of As, Cd and Cr by Typha latifolia.

The removal from the solution and the accumulation of As, Cd and Cr by Typha latifolia was studied. Small plants of T. latifolia, collected from a non-contaminated site, were exposed to individual concentrations of As, Cd and Cr for 10 days. The ability of T. latifolia for the removal of toxic elements ranged from 23% to 54% for As, 43%-55% for Cd and 28%-73% for Cr. The accumulation of toxic elements in T. latifolia occurred mainly in the roots. The results suggest that T. latifolia can be considered as an interesting alternative for treating aquatic effluents polluted with toxic trace elements.

Removal and accumulation of cadmium and lead by Typha latifolia exposed to single and mixed metal solutions.

We investigated the effect of Cd and Pb on the growth of the aquatic macrophyte Typha latifolia; the removal from the solution and the accumulation of these elements by the plant were also studied. Thus, small plants of T. latifolia, collected from a noncontaminated site, were exposed for 10 days to Cd and Pb, in a single solution or in mixture solutions, at two concentrations of the metals (5 and 7.5 mg/L). Our results showed that T. latifolia removed effectively Cd and Pb from solutions and was able to accumulate these metals in the roots and, to a lesser extent, in the leaves. Our findings suggested a synergistic effect of Cd and Pb with respect to the toxicity to T. latifolia. Additionally, Cd diminished the Pb absorption by T. latifolia. Our results confirmed, using scanning electron microscopy, the internalization of Cd and Pb in T. latifolia.