This paper tested if culturing the moss Scorpiurum circinatum (Brid.) Fleisch. & Loeske with metal solutions (Cd, Cu, Pb and Zn) for 30 days causes metal bioaccumulation and ultrastructural changes. The results showed that despite the high heavy metal concentrations in treatment solutions, treated samples did not show severe ultrastructural changes and cells were still alive and generally well preserved. Bioaccumulation highlighted that moss cells survived to heavy metal toxicity by immobilizing most toxic ions extracellularly, likely in binding sites of the cell wall, which is the main site of metal detoxification.

To determine if long-term equilibration may alleviate molybdenum toxicity, earthworms, enchytraeids, collembolans and four plant species were exposed to three soils freshly spiked with Na₂MoO₄.2H₂O and equilibrated for 6 or 11 months in the field with free drainage. Total Mo concentrations in soil decreased by leaching, most (up to 98%) in sandy soil and less (54–62%) in silty and clayey soils. Changes in residual Mo toxicity with time were inconclusive in sandy soil. In the other two soils, toxicity of residual total Mo was significantly reduced after 11 months equilibration with a median 5.5-fold increase in ED50s. Mo fixation in soil, i.e. the decrease of soil solution Mo concentrations at equivalent residual total soil Mo, was maximally a factor of 2.1 only. This experiment shows natural attenuation of molybdate ecotoxicity under field conditions is related to leaching of excess Mo and other ions as well as to slow ageing reactions.

Environmental effects of copper nanoparticles are little studied in terrestrial ecosystems. In the present article, the toxicity of copper nanoparticles (Cu-NP) on the enchytraeid Enchytraeus albidus is compared to the toxicity of a copper-salt (CuCl₂). The effect parameters studied were survival, reproductive output and avoidance behaviour. The results show that Cu-NP were more toxic to E. albidus than the same concentrations of the CuCl₂-salt. The physic-chemical analysis of the particles indicated that only a small fraction was released as ions. Hence, the results indicated a nanoparticle-specific effect – lower reproductive output and higher avoidance. This was observed as 2–8 fold (significant) lower ECx values for Cu-NP (EC₅₀₋ᵣₑₚᵣₒd = 95 mg Cu/kg; EC₅₀₋ₐᵥₒᵢd = 241 mg Cu/kg) exposed organisms compared to CuCl₂ (EC₅₀ ₋ ᵣₑₚᵣₒd = 251 mg Cu/kg; EC₅₀₋ₐᵥₒᵢd = 475 mg Cu/kg) exposed organisms. These results corroborate with a nanoparticle-specific effect.

Short-term changes in levels of expression of nine stress response genes and oxidative damage of proteins were examined in Eisenia fetida exposed to polyvinylpyrrolidone (PVP) coated Ag nanoparticles (Ag-NP) and AgNO₃ in natural soils. The responses varied significantly among days with the highest number of significant changes occurring on day three. Similarity in gene expression patterns between Ag-NPs and AgNO₃ and significant relationships of expression of CAT and HSP70 with Ag soil concentration suggest similarity in toxicity mechanisms of Ag ions and NPs. Significant increases in the levels of protein carbonyls on day three of the exposure to both ions and Ag-NPs indicate that both treatments induced oxidative stress. Our results suggest that Ag ions drive short term toxicity of Ag-NPs in E. fetida. However, given that <15% of Ag in the NPs was oxidized in these soils, dissolution of Ag-NPs is likely to occur after or during their uptake.

Sorption of anionic perfluorooctane sulfonate (PFOS) on marine sediment was investigated in detail. It was found that solution ionic composition and sediment-specific parameters played important roles in affecting the sorption of PFOS. The results indicated that sorption of PFOS in seawater to marine sediments was strong (∼10 times higher than that in freshwater) and nonlinear (Freundlich nF values of 0.77–0.96). The sorption affinity was well correlated with sediment organic carbon content, indicating the importance of hydrophobic interactions. At a PFOS aqueous concentration of 10μg/L, PFOS distribution coefficients increased with the increasing salinity in solution, with an average rate of 0.48±0.03log units per a log unit of salinity. Further studies demonstrated that among common ions contributing to the salinity in seawater, dissolved calcium and magnesium are dominantly responsible for the sorption-enhancing effect of salinity for PFOS. This work will aid in better understanding of PFOS sorption mechanisms, and be useful for fate modeling of this class of contaminants in the marine environment.

This paper examined the ability of honeycomb biomass (HC), a by-product of the honey industry, to remove Pb(II), Cd(II), Cu(II), and Ni(II) ions from aqueous solutions. The equilibrium adsorptive quantity was determined as a function of the solution pH, amount of biomass, contact time, and initial metal ion concentration in a batch biosorption technique. Biosorbent was characterized by Fourier transform infrared (FTIR), scanning electron microscopy with energy-dispersive X-ray, and X-ray diffraction studies. FTIR spectral analysis confirmed the coordination of metals with hydroxyl, carbonyl, and carboxyl functional groups present in the HC. The metals uptake by HC was rapid, and the equilibrium time was 40 min at constant temperature and pH. Sorption kinetics followed a nonlinear pseudo-second-order model. Isotherm experimental data were fitted to Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherm models in nonlinear forms. The mechanism of metal sorption by HC gave good fits for Langmuir model, and the affinity order of the biosorbent for four heavy metals was Pb(II)>Cd(II)>Cu(II)>Ni(II). The thermodynamic studies for the present biosorption process were performed by determining the values of ΔG°, ΔH°, and ΔS°, and it was observed that biosorption process is endothermic and spontaneous. This work provides an efficient and easily available environmental friendly honeycomb biomass as an attractive option for removing heavy metal ions from water and wastewater.

This work assesses the use of immobilized humic acid (ImHA) onto aminopropyl silica (APS) as a sorbent for the removal and preconcentration of trace amounts of cobalt ions by on-line solid phase extraction (SPE) technique in the column system prepared in our laboratory. Different parameters, such as the effect of the pH, concentration, and flow rate, were studied and throughput was observed by a UV detector. All SPE steps were monitored by breakthrough curves used to visualize distribution of cobalt concentration between mobile and solid phase. The solutions collected from stripping steps were analyzed in atomic absorption spectrometer (AAS) and the amount of sorbed ions was calculated. Sorption characteristics were evaluated by using common adsorption isotherms and Scatchard plot analysis. From the obtained results, it was seen that sorption mechanism of cobalt ions were fitted to Langmuir model on a large scale and thought to be localized. Mean free energy (E = 40.82 kJ mol⁻¹) calculated from D-R isotherm showed that chemical interactions are more effective than physical interactions. This investigation reveals a new, simple, environmentally friendly, and cost-effective method for removal and preconcentration of cobalt ions from aqueous solutions by a new aminopropyl silica-immobilized humic acid material.

Since swine wastewater is used by farmers for soil fertilization, evaluation of toxic compounds or micro-contaminants of separate streams is required. This paper uses the toxicity identification evaluation (TIE) procedure for the physicochemical and ecotoxicological characterization of swine wastewater. To distinguish the most important toxic compounds, a physicochemical characterization and phase I-TIE procedure were performed. The acute toxic effect of swine wastewater and treated fractions (phase II-TIE) were evaluated using Daphnia magna determining 48-h LC50. Results show a high level of conductivity (23.5 μS cm−1), which is explained as due to the concentration of ions, such as ammonium (NH 4 + –N 1.6 g L−1), sulfate (SO 4 2− 397.3 mg L−1), and chlorine (Cl− 1,230.0 mg L−1). The acute toxicity of the swine wastewater was evaluated on D. magna (48-h LC50 = 3.4%). Results of the different water treatments indicate that anionic exchange treatments could reduce 22.5% of swine wastewater’s acute toxicity by reducing chlorine (to around 51%) and conductivity (8.5%). On the other hand, cationic exchange treatment increased acute toxicity on D. magna (% RT = −624.4%), by reducing NH 4 + –N (around 100%) and total nitrogen (95.5%). This finding suggests that part of the toxicity comes from anionic compounds, such as chlorine.

Currently, there are five known types of mercury transporters in bacteria: MerC, MerE, MerF, MerH, and MerT. Their general function is to mediate mercuric ion uptake into the cell in preparation for reduction to Hg°. They are present in several bacterial phyla and comprise five distinct families. We have utilized standard statistical bioinformatic tools and the superfamily principle to show that they are related by common descent. After using programs such as Global Alignment Program and SSearch to establish homology, we aligned and analyzed their amino acid sequences to find a single well conserved motif. Although these proteins exhibit 2, 3, or 4 transmembrane helical segments (TMSs), TMSs 1 and 2 are common to all superfamily members. An ancestral sequence was determined, and reliable phylogenetic trees were constructed. The results support the conclusion of homology, establishing that these proteins belong to a single superfamily. This important discovery allows extrapolation of information about structure, function, and mechanism from one protein to all superfamily members to degrees inversely proportional to their phylogenetic distances.

A thin film of well-ordered anatase TiO₂ nanotubes prepared by anodic oxidation of titanium metal were synthesised and used as adsorbent medium for the purification of water from aqueous uranium and lead. The amount of subtracted metal ions was quantified by using X-ray photoelectron spectroscopy at the surface of the reacted TiO₂ surface. Batch experiments for the sorption of U and Pb at the surface of the titania substrate were carried out in separated solution equilibrated with air of uranyl acetate and lead nitrate, in the pH range 3–9. For uranium, the experiments were also repeated in anoxic (N₂) atmosphere. The amount of metal ions adsorbed onto the titania medium was quantified by measurements of the surface coverage expressed in atomic percent, by recording high-resolution XPS spectra in the Ti2p, U4f and Pb4f photoelectron regions. Adsorption of the uranyl species in air atmosphere as a function of pH showed an adsorption edge near pH 4 with a maximum at pH 7. At higher pH the presence of very stable uranyl–carbonate complexes prevented any further adsorption. Further adsorption increased until pH 8.5 was obtained when the uranyl solution was purged from dissolved CO₂. Lead ion showed a sorption edge at pH 6, with a maximum uptake at pH 8. The results showed that the uptake of uranium and lead on the selected titania medium is remarkably sensitive to the solution pH. This study demonstrates the reliability of this type of material for treating water polluted with heavy metals as well as leachates from radioactive nuclear wastes.