Seedlings of Cosmos bipinnatus were cultured in vitro for 30 days on modified Murashige–Skoog medium supplemented with four different concentrations of hexavalent chromium (Cr(VI); 0.0–2.0 mM). Seed germination occurred after 7 days of culture, but was significantly lower when cultured in 2.0 mM Cr(VI) than when cultured without Cr(VI) in the medium. Seedlings were able to survive heavy metal stress condition, irrespectively of the Cr(VI) concentration used. The seedlings showed two metal tolerance mechanisms that were dependent on chromium concentration: (1) metal exclusion at 0.0–0.5 mM and (2) metal accumulation at 1.0–2.0 mM. Regarding the latter mechanism, seedlings showed metal accumulation values considered as characteristic of hyperaccumulator species. The highest bioaccumulation in dry tissue was of 5443 mg Cr kg⁻¹in shoot and 4767 mg Cr kg⁻¹in root for seedlings cultured with 2.0 mM of Cr(VI). These results indicated that substantial Cr translocation from the roots unto shoots took place (translocation factor > 1.14) associated to a bioaccumulation factor for Cr(VI) greater than 98.

To biocontrol algal bloom, a novel algicidal bacterium, Enterobacter sp. NP23, was isolated. This strain has an effective algicidal activity against Chlorella vulgari, Microcystis aeruginosa, Scenedesmus, and Chlorella pyrenoidosa. Meanwhile, the growth factors were assayed to obtain a high cell density of strain NP23. As a result, three growth factors (i.e., KNO₃0.6 %, MnSO₄·H₂O 0.001 %, and K₂HPO₄0.3 %) were determined as the critical roles in enhancing the cell density of 10¹³ CFU/mL. Moreover, algicidal activity assays revealed that strain NP23 exhibited high algicidal activities against M. aeruginosa and Scenedesmus. These results indicate that this wild-type strain would provide a new member for biocontrolling microalgal and cyanobacterial populations in eco-technology.

Spatial and seasonal mobilization trends of metals in surface water were evaluated in the US–Mexico San Pedro River (SPR). Water samples were collected at five sampling stations for the analysis of dissolved oxygen, pH, electric conductivity, sulfates, and metals (Cd, Cu, Fe, Mn, Pb, and Zn). Quality of the water was characterized through Ecological Criteria of Water Quality (ECWQ) established in Mexico and Water Quality Criteria (Environmental Protection Agency (EPA)). High total metal concentrations were detected as follows: Fe > Cu > Mn > Zn > Pb > Cd. Metal concentrations were slightly higher in dry season than in rainy season: Cd (below detection limit (BDL)–0.21 mg L⁻¹), Cu (BDL–13 mg L⁻¹), Fe (0.16–345 mg L⁻¹), Mn (0.12–52 mg L⁻¹), Pb (BDL–0.48 mg L⁻¹), and Zn (0.03–17.8 mg L⁻¹). Low pH and dissolved oxygen values as well as high sulfate content were detected in both seasons. High values of metals (Cd, Cu, Fe, Mn, Pb, Zn) were detected at station E1 representing pollution source, as well as at stations E2 (Cd, Cu, Fe, Mn), E3 (Fe, Mn, Pb), and E4 and E5 (Fe, Mn). Detected concentrations exceeded maximum permissible established in ECWQ and Water Quality Criteria (EPA). Efflorescence salts on sediments in the dry season could increase levels of metals in water column. This study provides valuable information on the potential mobility of metals in surface water of SPR located in an arid environment where transport processes are strongly linked to climate. The information derived from this study should help the regional and national authorities to address present environmental regulations.

Fugitive greenhouse gas emissions from unconventional gas extraction processes (e.g. shale gas, tight gas and coal bed methane/coal seam gas) are poorly understood due in part to the extensive area over which these emissions may occur. We apply a rapid qualitative approach for source assessment at the scale of a large gas field. A mobile cavity ring down spectrometer (Picarro G2201-i) was used to provide real-time, high-precision methane and carbon dioxide concentration and carbon isotope ratios (δ¹³C), allowing for “on the fly” decision making and therefore an efficient and dynamic surveying approach. The system was used to map the atmosphere of a production coal seam gas (CSG) field (Tara region, Australia), an area containing pre-production “exploration” CSG wells (Casino, Australia), and various other potential CO₂and CH₄sources (i.e. wetlands, sewage treatment plants, landfills, urban areas and bushfires). Results showed a widespread enrichment of both CH₄(up to 6.89 ppm) and CO₂(up to 541 ppm) within the production gas field, compared to outside. The CH₄and CO₂δ¹³C source values showed distinct differences within and outside the production field, indicating a CH₄source within the production field that has a δ¹³C signature comparable to the regional CSG. While this study demonstrates how the method can be used to qualitatively assess the location and source of emissions, integration with atmospheric models may allow for quantitative assessment of emissions. The distinct patterns observed within the CSG field demonstrates the need to fully quantify the atmospheric flux of natural and anthropogenic, point and diffuse sources of greenhouse gases from individual Australian gas fields before and after production commences.

Effects of the combined application of ferrihydrite-modified diatomite (FHMD) and gypsum on phosphorus control were investigated in a laboratory-scale artificial aquarium under anoxic and agitation conditions over 120 days. Daily oscillation of a metal grid to simulate agitating effects by wind did not yield the sediment resuspension in the 120-day treatment aquarium (120-day aquarium) due to the gypsum stabilization, while significant sediment resuspension was observed in the control aquarium. The combined application of FHMD and gypsum did not affect the total kjeldahl nitrogen (TKN) concentrations in both the control aquarium and the 120-day aquarium. Under anoxic conditions and sediment resuspension conditions, a large increase in total phosphorus (TP) concentrations was observed in the control aquarium. However, the TP concentrations in the 120-day aquarium stayed relatively stable, within a range of 9.1–13.3 μg/L. After the 120 days’ incubation, translocation from mobile labile-P and organic-P to P adsorbed by FHMD occurred. The combined application of FHMD and gypsum effectively maintained TP levels within the oligotrophic range under anoxic and agitation conditions in the laboratory-scale artificial aquarium by removing phosphorus from lake water and reducing sedimentary phosphorus release via gypsum sediment stabilization and FHMD phosphorus immobilization.

Phytoremediation can be assisted by microorganisms, which promote plant growth and increase heavy metal availability in soil. In this study, we aimed at evaluating the effect of two plant growth-promoting bacteria (PGPB) on phytoextraction of copper (Cu) by maize. We chose the strains based on their ability to synthesize indole compounds, produce siderophores, solubilize phosphorus, and increase soil conductivity and extractable Cu in soil. Then, in glasshouse experiments, we assessed their ability to increase biomass, chlorophyll content, and Cu extraction by maize. Results showed that Acinetobacter sp. RG30 and Pseudomonas putida GN04 were overall the most active strains to synthesize indole, produce siderophores, and solubilize phosphorus, and hence selected for further studies. Also, both were able to significantly increase soil conductivity and release Cu from soil compared to control. Glasshouse experiments showed that Cu had a negative effect on plant growth, but inoculation with bacteria promoted plant growth and chlorophyll content in its presence (p < 0.05). Notably, the effect of inoculation on plant growth was larger on contaminated than on uncontaminated soil, which suggests an overall bacterial effect for alleviation of stress caused by Cu. Inoculation with RG30 or GN04 improved Cu extraction by maize (p < 0.05); interestingly, co-inoculation led to the highest accumulation (200 μg Cu/g plant dry weight). We conclude, therefore, that inoculation with RG30 and GN04 improves metal extraction by increasing plant growth, fitness, and availability of minerals in soil, which represents an important tool for the improvement of phytoextraction processes in polluted environments.

Novel nanocomposite hydrogels based on wheat bran-g-poly(methacrylic acid) and nano-sized clinoptilolite have been successfully utilized for the removal of Pb(II), Cu(II), Cd(II), and Ni(II) cations from their aqueous solution. The experimental results were investigated using Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order and interparticle diffusion kinetic models were studied in order to analyze the kinetic data. The kinetic data indicated that the rate of cation adsorption on nanocomposite hydrogels was fast that more than 80 % of the equilibrium adsorption capacity occurs within 15 min. The maximum monolayer adsorption capacity of the nanocomposite hydrogel, as obtained from the Langmuir adsorption isotherm, was found to be 166.7, 243.9, 175.4, and 166.6 mg g⁻¹ for Pb(II), Cu(II), Cd(II), and Ni(II), respectively. Thermodynamic parameters such as free energy (ΔG ⁰), enthalpy (ΔH ⁰), and entropy (ΔS ⁰) change were determined; the sorption process was found to be endothermic. The results of five times sequential adsorption–desorption cycle showed high adsorption efficiency and a good degree of desorption.

Adsorption and degradation processes of triclosan (TCS) were studied in the laboratory using field-collected sediments of different physicochemical properties. Batch equilibrium experiment indicated that adsorption isotherms were fitted well to both linear and Freundlich model with linear sorption coefficients (K d) varied from 147 to 1,425 mL μg⁻¹. The sediment with a higher organic carbon content and a lower pH value had the greatest adsorption capability. Degradation experiment showed that triclosan was relatively stable in water with calculated half-life values ranged from 89 to 161 days. No degradation in sterilized water suggested that the loss of triclosan was due to biological processes. Degradation was more rapid in water-sediment system than in water, and the calculated half-life value in water-sediment systems ranged from 32 to 62 days. Methylation of triclosan was observed in all studied sediments, but the amount of methyl-triclosan (M-TCS) accounted for less than 5 % of the degradated TCS.

Polybrominated diphenyl ethers (PBDEs) are a class of global flame retardants whose residues have markedly increased in fish and human tissues during the last decade. They belong to persistent and toxic contaminants which need more attention and toxicological study as their degradation in the environment is not well understood. This study characterizes 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) bioconcentration, elimination and biotransformation in juvenile turbot Psetta maxima, in order to evaluate the risk of its bioaccumulation in the marine environment. During this study, juvenile turbot were exposed to environmentally relevant BDE-47 concentrations from 0.001 to 1 μg/L for 16 days via aqueous exposure. This study found that juvenile turbot bioconcentrated and biotransformed BDE-47. There was no difference in standard length or weight between control and exposed fish. Uptake and elimination of BDE-47 by the turbot during exposure were examined in controlled laboratory experiments. Bioconcentration of BDE-47 was similar in fish from all treatment groups. Bioconcentration was rapid and increased with exposure time, since the bioconcentration factor (BCF) was higher. However, elimination was slower in comparison and low elimination was detected after 10 days in clean water. BDE-47 concentration in water influences the BCF. Half-life ranged between 37 and 108 days and theoretical times t₉₀could range from 120 to 358 days. The present study demonstrates a stepwise debromination of BDE-47 to BDE-28.

Treatment of reverse osmosis concentrate (ROC) has been complicated in terms of feasibility, cost, and most importantly, efficiency in removing contaminants. While adsorbents such as activated carbon, coal, and fly ash can remove organics, they may not be effective in removing nutrient salts that cause algae growth. Moreover, with regards to physical treatment, removing contaminants using adsorbents may not be appropriate, as toxic and non-biodegradable pollutants are not transformed or degraded into non-toxic forms. In this study, a series of processes involving adsorption using activated carbon and oxidation by hydroxyl and sulfate radicals were assessed as a means of treating ROC. The method includes treating water containing organics with an adsorbent, and adding nano-sized zero-valent iron (nZVI) to the water in the presence of oxygen, followed by the addition of persulfate, where the water is oxidized with reactive oxygen species (e.g., hydroxyl radical, peroxide, superoxide anion) produced by the addition of ZVI and persulfate radicals generated from persulfate activated by the addition of nZVI. Removal of non-biodegradable organics (as well as nitrogen and phosphorous) and nutrient salts not readily removed by conventional treatment methods can be effectively accomplished through the physical removal method described, using activated carbon, and by a chemical removal method using radical oxidation.