A comprehensive ecotoxicity assessment of three different nanosized TiO₂ (with 16, 36 and 89 nm particle diameter) and one microscale TiO₂ suspension (with 3264 nm particle diameter) was carried out with a special emphasis on the relation between product characteristics and toxic effect. The applied test battery included the combination of modified standardized tests (Aliivibrio fischeri bioluminescence inhibition test, Lemna minor growth inhibition test), and nonstandardized bioassays with unconventional physiological endpoints (Tetrahymena pyriformis phagocytic activity, the Daphnia magna heartbeat rate). Based on the lowest significant effect values, the tested aquatic organisms were the most sensitive to the microscale TiO₂ suspension (with 3264 nm particle size). Although the three nanoscale TiO₂ particles were aggregated in the A. fischeri and the L. minor growth media, significant inhibition rates were experienced at 0.1 and at 1 μg L─¹ concentration of nTiO₂ suspensions with 16 and 36 nm primary particle size, respectively. Larger aggregates may have also high impact on biological organisms. In case of the D. magna heartbeat rate test rapid agglomeration was avoided, but lower responses were found compared to other investigated systems. The short term T. pyriformis phagocytic activity test demonstrated outstanding sensitivity; three TiO₂ suspensions were significantly toxic even at 0.1 μg L─¹. The consequences of our study clearly indicated that nanoscale TiO₂ may have an impact on the aquatic ecosystem which is strongly influenced by aggregation. The effect of exposure duration and concentration as contributing factors in nano-titanium dioxide mediated toxicity was also demonstrated.

The pollution of the air and the monitoring of indoor air quality are receiving increasing attention worldwide, and many methodologies are now available to identify sources of pollution. However, there has been less work concerning the development of techniques to mitigate the effects of indoor air pollution. The aim of this study was to modify cotton fabrics with silver nanoparticles in order to use them in air conditioner filters. To achieve this goal, common fabrics purchased from commercial sources were evaluated in terms of their filtration properties (permeability, pressure drop, and collection efficiency) and were subsequently modified by impregnation with nanoparticles. This modification was achieved by immersion of the filters in nanoparticle suspensions. After drying the filter, collection of particulate matter was made in a toilet. The results showed that the filters impregnated with silver nanoparticles were able to significantly reduce the activity of microorganisms present in the airborne particulate matter, resulting in growth inhibition to the microorganisms which were retained (76.70%) and passed through (96.34%) the cotton filters.

A chelator, potassium dipropyl dithiophosphate, and humic acid were combined and used as a stabilizing agent to study the stabilization effect of the mixture on heavy metals in a contaminated sediment. The results indicated that the stabilization efficiencies for Cu, Zn, Pb, and Cd in the sediment were up to 99.98, 90.66, 99.38, and 92.83%, respectively, and the unstable Cu, Zn, Pb, and Cd fractions fell by 57.11, 54.74, 56.41, and 89.14%, respectively, when 5% potassium dipropyl dithiophosphate and 7% humic acid were added. This significantly reduced the bioavailability of the heavy metals. Under leaching caused by simulated acid rain (pH 3 and pH 5), the heavy metals mainly migrated from the solid phase to the liquid phase during the initial leaching period, and the Pb, Cu, Zn, and Cd leaching rates in the sediment after stabilization fell by 55–99%. Cu showed the greatest reduction. When the results for the sediment after stabilization were compared with the sediment before stabilization, the wheat stem height had increased by 53.62%, the dry weights of the leaves and roots increased by 86.25 and 34.85%, respectively, and Cu, Zn, Pb, and Cd enrichment in the wheat roots and leaves fell by 40–88 and 73–95%, respectively.

Air sparging (AS) is one of the most efficient techniques for remediating saturated soils and groundwater contaminated with volatile organic compounds. Most studies have focused on how the subsurface conditions control the AS process; however, the “side-effects” of AS that feed back to subsurface environment have not been well addressed. This paper studied the perturbation of porous media induced by AS and the consequent multi-parameter changes with the support of Miller soil box and resistivity test, and Darcy experiment and tracer breakthrough test. The Miller soil box test shows that the resistivity response can be credibly used as a non-intrusive method to indicate the porosity change, and that the porosity-resistivity data can be well fitted using Archie equation (R ² > 0.98). Based upon the electricity measurement and above quantitive relationship, it was found that the porosity increased near the air injection point and decreased near the upper boundary of the column due to the upward-transport of particles during air sparging. The changes in porosity were found to be directly proportional to the air injection rate, and the maximum absolute variation of porosity was up to 0.104 at the air flow rate of 20 ml/min, while it did not change in the absence of AS. Both the hydraulic conductivity and dispersion coefficient increased after AS perturbation as the preferential flow pathway formed. The two parameters changed from 3.40 m/d and 0.110 to 6.13 m/d and 0.288, respectively, at 20 ml/min. This work provides useful insight into the changes in flow and transport properties of porous media induced by AS, which then help to understand the instability of air flow and the parameter-uncertainty analysis in related AS model.

Five common fungal strains, Cladosporium cladosporioides, Aspergillus clavatus, Penicillium citrinum, Fusarium oxysporum, and Alternaria alternata, were cultivated in presence of iodide and iodate to evaluate their efficiency in iodine biovolatilization and bioaccumulation. Our results suggest that iodide and iodate bioaccumulation by microscopic filamentous fungi is similar although the biological transformation into volatile iodine compounds is driven by various pathways resulting in higher volatilization efficiency of iodate. Thus, the mobilization of iodate by filamentous fungi is superior to iodide mobilization. Our paper is also the first to compare the iodide and iodate volatilization efficiency by microorganisms. Our results highlight the significant role of filamentous fungi in biogeochemistry of iodine, especially in formation of environmentally reactive volatile forms that may contribute to ozone layer destruction.

Metals are commonly determined in aquatic organisms, primarily using bivalves to provide important data on their bioavailability. The technique of diffusive gradients in thin films (DGTs) has also been employed to assess the concentration of metals in freshwater and marine environments, determining their lability. The present work evaluated and compared the labile and bioavailable concentrations of Cd, Co, Cu, Mn, Ni and Pb in seawater from Ilha Grande Bay, RJ, using DGT and transplanted bivalves (Nodipecten nodosus), respectively. The scallops and DGTs were immersed in water at three sampling locations within the bay from July to September 2012 (winter campaign) and from December 2012 to February 2013 (summer campaign). The metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and optical emission spectrometry (ICP-OES). DGT technique was successfully used to determine the concentrations of metals in waters, except for Pb when short deployment times were used. All metals were determined using transplanted bivalves (N. nodosus), but pre-exposure to Cd was evident, which made the interpretation of the data for this analyte difficult. The data on metal lability in Ilha Grande Bay waters obtained from the DGT technique were correlated with the metal bioavailability determined in the soft tissues of the transplanted N. nodosus for Co, Cu, Mn, Ni and Pb. This is the first evaluation of this type for this area of high environmental concern. Both techniques revealed that Náutico was the location with the highest concentration of metals in the study area.

The objectives of the present study are to isolate thiosulfate-degrading bacterium and optimize its degradative conditions including temperature, pH, and thiosulfate concentrations required for bioremediation purposes. A heterotrophic thiosulfate-degrading bacterial strain DT was successfully isolated from saline soil and identified as Altererythrobacter sp. based on its physicochemical properties and 16S rDNA sequence analysis. It was a naturally occurring methionine auxotrophic strain that utilized only peptone, yeast extract, or several amino acids as the sole carbon source. Altererythrobacter sp. DT degraded thiosulfate via a distinctive disproportionation reaction which was characterized by accumulation of sulfate and elemental sulfur at a molar ratio of 1:1. Optimal conditions for both bacterial growth and thiosulfate metabolism were 25–30 °C and pH 6, respectively. In a fed-batch treatment system receiving liquid polysulfide wastewater, a high degradation rate of 407.3 mg S₂O₃²⁻/(L h) and an elemental sulfur yield of nearly 50% were achieved for immobilized DT cells, indicating great potential of strain DT for future application in the treatment of and microbial production of elemental sulfur from thiosulfate-bearing industrial wastewater.

Copper is a common aqueous pollutant that is known to cause oxidative stress and disrupt the thyroid axis in amphibians. In the present study, tadpoles of the Chinese toad (Bufo gargarizans) were exposed to 1, 6.4, 32, and 64 μg L⁻¹ of copper from Gosner stages 26 to 42. We aimed to examine the influence of copper on thyroid hormone-responsive and stress-associated gene expression in the hind-limb, tail, and liver of B. gargarizans tadpoles. Exposure to 64 μg L⁻¹ copper decreased percent metamorphosis and increased length of both hind-limb and tail of B. gargarizans tadpoles at Gs 42. In addition, according to real-time PCR results, exposure to 64 μg L⁻¹ copper induced downregulation of Dio2, Dio3, TRα, and TRβ mRNA levels in all tissues examined. We inferred that copper might induce a considerable reduction of TH levels through downregulation of Dio2 and Dio3 mRNA levels in peripheral tissues. Decreased TH levels may then decrease the expressions of TRα and TRβ. Also, HSP, SOD, and PHGPx transcript levels were measured to assess cellular stress which might affect TH signaling and metamorphosis. We found that copper significantly downregulated the level of HSP, SOD, and PHGPx transcripts in the hind-limb and tail. This demonstrates that high concentrations of copper could disrupt the antioxidant system of B. gargarizans tadpoles and increase oxidative damage. Therefore, we conclude that copper could disrupt the antioxidant system and cause thyroid hormone disruption in B. gargarizans tadpoles.

Increasing concentrations of tropospheric ozone and reactive nitrogen threaten the composition and function of semi-natural plant communities. Using a free-air fumigation system, we investigated the effects of elevated ozone (1.73 × ambient concentration; +O₃) and nitrogen (+50 k g N ha year⁻¹; +N) deposition on growth of juveniles of three subalpine grassland species and their colonization by arbuscular mycorrhizal fungi (AMF) in situ. In a subsample, the extra-radical mycelium was regularly disrupted to determine the effect of AMF on the plants’ pollutant sensitivity. The plants reacted sensitively to the pollutants: +N increased shoot growth in Festuca rubra, while +O₃ decreased root growth in Trifolium alpinum and F. rubra. Colonization with AMF was stimulated by N in Leontodon helveticus and was strongly reduced by O₃ in F. rubra and L. helveticus, probably due to lower carbon allocation belowground. Conversely, AMF did not protect plants from O₃ neither did they increase the species’ responsiveness to N. Our results indicate that irrespective of AMF colonization, juvenile plants are highly sensitive to O₃ stress, probably since their growth is primarily limited by carbon assimilation.

Effects of ozonation and powdered activated carbon on removal of dissolved organic matter (DOM) and disinfection by-product (DBP) in reservoir water were intensively investigated in this study. Both the formation of carbonaceous DBP (C-DBP) and nitrogenous DBP (N-DBP) as well as their speciation were analyzed. Results exhibited that the addition of powdered activated carbon (PAC) greatly improved the removal of aromatic protein. Trihalomethanes (THMs) and haloacetonitriles (HANs) were the dominant species in C-DBP and N-DBP. The integrated coagulation and PAC processes could remove more than 70% of THMs and 93% of HANs precursors, while only 10.5 and 45% of capture were achieved by the single coagulation. The added ozone lowered the yields of HANs but synchronously increased the more toxic bromine-containing THMs from 78.5 to 128.1 μg/L. Kinetics parameters for THM formation indicated that the precursor creating the THMs fast could be easily removed by both the coagulation and PAC adsorption.