A protocol was developed to extract, fractionate, and quantitatively analyze periphyton extracellular polymeric substances (EPS), which obtains both information on the molecular weight (M ᵣ) distribution and protein and polysaccharide content. The EPS were extracted from freshwater periphyton between July and December 2011. Organic carbon (OC) compounds from different EPS extracts were analyzed using liquid chromatography-organic carbon detection–organic nitrogen detection (LC-OCD-OND), and total protein and polysaccharide content were quantified. Four distinct OC fractions, on the basis of M ᵣ, were identified in all extracts, corresponding to high M ᵣ biopolymers (≥80–4 kDa), degradation products of humic substances (M ᵣ not available), low M ᵣ acids (10–0.7 kDa), and small amphiphilic/neutral compounds (3–0.5 kDa). Low C/N ratios (4.3 ± 0.8) were calculated for the biopolymer fractions, which represented 16–38 % of the measured dissolved organic carbon (DOC), indicating a significant presence of high M ᵣ proteins in the EPS. Protein and polysaccharide represented the two major components of EPS and, when combined, accounted for the measured DOC in extracts. Differences in specific OC fractions of EPS extracts over the course of the study could be quantified using this method. This study suggests that LC-OCD-OND is a new valuable tool in EPS characterization of periphyton.

This study presents simultaneous hexavalent chromium (Cr(VI)) reduction and phenol degradation using Stenotrophomonas sp., isolated from tannery effluent contaminated soil. Phenol was used as the sole carbon and energy source for Cr(VI) reduction. The optimization of different operating parameters was done using Placket-Burman design (PBD) and Box-Behnken design (BBD). The significant operating variables identified by PBD were initial Cr(VI) and phenol concentration, pH, temperature, and reaction time. These variables were optimized by a three-level BBD and the optimum initial Cr(VI) concentration, initial phenol concentration, pH, temperature, and reaction time obtained were 16.59 mg/l, 200.05 mg/l, 7.38, 31.96 °C and 4.07 days, respectively. Under the optimum conditions, 81.27 % Cr(VI) reduction and 100 % phenol degradation were observed experimentally. The results concluded that the Stenotrophomonas sp. could be used to decontaminate the effluents containing Cr(VI) and phenol effectively.

This paper demonstrated the relative bactericidal activity of photoirradiated (6W-UV Torch, λ > 340 nm and intensity = 0.64 mW/cm) P25-TiO nanoparticles, nanorods, and nanotubes for the killing of Gram-negative bacterium Agrobacterium tumefaciens LBA4404 for the first time. TiO nanorod (anatase) with length of 70-100 nm and diameter of 10-12 nm, and TiO nanotube with length of 90-110 nm and diameter of 9-11 nm were prepared from P-25 Degussa TiO (size, 30-50 nm) by hydrothermal method and compared their biocidal activity both in aqueous slurry and thin films. The mode of bacterial cell decomposition was analyzed through transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR), and K ion leakage. The antimicrobial activity of photoirradiated TiO of different shapes was found to be in the order P25-TiO > nanorod > nanotube which is reverse to their specific surface area as 54 < 79 < 176 m g, evidencing that the highest activity of P25-TiO nanoparticles is not due to surface area as their crystal structure and surface morphology are entirely different. TiO thin films always exhibited less photoactivity as compared to its aqueous suspension under similar conditions of cell viability test. The changes in the bacterial surface morphology by UV-irradiated P25-TiO nanoparticles was examined by TEM, oxidative degradation of cell components such as proteins, carbohydrates, phospholipids, nucleic acids by FT-IR spectral analysis, and K ion leakage (2.5 ppm as compared to 0.4 ppm for control culture) as a measure of loss in cell membrane permeability.

Greenhouse gas (GHG) emission in wastewater treatment plants of the pulp-and-paper industry was estimated by using a dynamic mathematical model. Significant variations were shown in the magnitude of GHG generation in response to variations in operating parameters, demonstrating the limited capacity of steady-state models in predicting the time-dependent emissions of these harmful gases. The examined treatment systems used aerobic, anaerobic, and hybrid—anaerobic/aerobic—biological processes along with chemical coagulation/flocculation, anaerobic digester, nitrification and denitrification processes, and biogas recovery. The pertinent operating parameters included the influent substrate concentration, influent flow rate, and temperature. Although the average predictions by the dynamic model were only 10 % different from those of steady-state model during 140 days of operation of the examined systems, the daily variations of GHG emissions were different up to ±30, ±19, and ±17 % in the aerobic, anaerobic, and hybrid systems, respectively. The variations of process variables caused fluctuations in energy generation from biogas recovery by ±16, ±17, and ±14 % in the three examined systems, respectively. The lowest variations were observed in the hybrid system, showing the stability of this particular process design.

Dioxin-like compounds are chronically toxic to most vertebrates. However, dramatic differences in sensitivity to these chemicals exist both within and among vertebrate classes. A recent study found that in birds, critical amino acid residues in the aryl hydrocarbon receptor (AhR) ligand binding domain are predictive of sensitivity to dioxin-like compounds in a range of species. It is currently unclear whether similar predictive relationships exist for fishes, a group of animals at risk of exposure to dioxin-like compounds. Effects of dioxin-like compounds are mediated through the AhR in fishes and birds. However, AhR dynamics are more complex among fishes. Fishes possess AhRs that can be grouped within at least three distinct clades (AhR1, AhR2, AhR3) with each clade possibly containing multiple isoforms. AhR2 has been shown to be the active form in most teleosts, with AhR1 not binding dioxin-like compounds. The role of AhR3 in dioxin-like toxicity has not been established to date and this clade is only known to be expressed in some cartilaginous fishes. Furthermore, multiple mechanisms of sensitivity to dioxin-like compounds that are not relevant in birds could exist among fishes. Although, at this time, deficiencies exist for the development of such a predictive relationship for application to fishes, successfully establishing such relationships would offer a substantial improvement in assessment of risks of dioxin-like compounds for this class of vertebrates. Elucidation of such relationships would provide a mechanistic foundation for extrapolation among species to allow the identification of the most sensitive fishes, with the ultimate goal of the prediction of risk posed to endangered species that are not easily studied.

Pterocarya stenoptera is a native deciduous tree species and a candidate for reforestation in the riparian zones of the Three Gorges Reservoir Region of Yangtze River in China. Water treatments of continuous flooding (CF) and periodic flooding–drought (PF) were applied to examine the growth dynamics of 4-month-old P. stenoptera seedlings and its effects on soil chemical properties. Results showed that P. stenoptera seedlings in both CF and PF significantly decreased leaf biomass accumulation and the height and diameter growth as compared to that in control (CK; treatment with well-watered, well-drained soil), respectively. There was no significant difference in stem biomass among the three groups, but root biomass in PF showed severe reduction compared to that in both CK and CF. Total biomass in PF was significantly decreased compared to that in CK, but comparable to that in CF. Furthermore, no significant difference was found between CF and CK in total biomass. Water treatments in the unplanted soil pots significantly influenced soil pH, soil organic matter (OM), total nitrogen (TN), and alkali hydrolysable nitrogen (AN) contents, in contrast to no significant effects in total phosphorus (TP), total potassium (TK), available phosphorus (AP), and available potassium (AK) contents. In P. stenoptera soils, there were significant effects by water treatment, time, and treatment × time in the eight tested soil chemical properties, except treatment in TK and time effect in OM content. Compared to unplanted soils, the growth of P. stenoptera seedlings significantly increased soil pH value and OM, TN, TP, and TK contents, while decreasing AN, AP, and AK contents in CK group, augmented the mean value of each of the tested soil chemical properties with an exception of AK content in CF group, and increased soil pH value and TN, AN, TP, and AP contents with no significant differences in OM, TK, and AK contents in PF group. Given the fact that TN and TP contents significantly increased in P. stenoptera soils as compared to those in unplanted soils, growth of P. stenoptera seedlings should be a successful candidate for restoration within the highly dynamic hydrologic zone of the riparian zones of the Three Gorges Reservoir Region.

This study demonstrates the influences of position, number of nitrogen (N) atoms and –C–N– or –N=N– linkage present in the six membered heterocyclic compounds such as pyridine, pyrazine, and pyridazine on their photocatalytic degradation by Au, Ag, and Fe⁺² deposited TiO₂ photocatalyst. The photodegradation rate of these heterocyclic compounds follow the order pyridine > pyrazine > pyridazine due to the different extent of hydroxylation and difference in position and number of N atoms in the aromatic moiety. The Au photodeposition significantly improved the TiO₂ photoactivity as compared to Ag and Fe⁺² loading. The presence of two N atoms in pyrazine and pyridazine as compared to one N atom in pyridine hamper the nucleophilc attack of OH radicals in comparison to easy hydroxylation of pyridine ring. There is 1 N atom, 4C–C, 1C–N and 1C=N bond in pyridine, 2 N atoms in the 1 and 4 positions, 2C–C, 2C–N bonds and 2C=N bonds in pyrazine, and pyridazine ring contains 2 N atoms in the 1 and 2 positions, 3C–C, 1N–N bond and 2C=N bonds. The bond strength/energy decreases gradually as: C=N– (615 KJ/mol) > –N=N– (418 KJ/mol) > –C–C– (347 KJ/mol) > –C–N– (305 KJ/mol) > –N–N– (163 KJ/mol). As pyridine has 1C–N, 1C=N, and no N–N bond, it photodegrades easily as compared to 1 N–N and 2C=N bonds of pyridazine of lowest photodecomposition rate. The improved photoactivity of Au–TiO₂ is explained on the basis of its favorable redox potential, work function, and electron-capturing capacity, etc.

Synthetic wastewaters are widely used in many fields of wastewater research and operational management. However, few comparative studies have been conducted on the large number of published formulations. Eleven synthetic formulations simulating municipal wastewaters were selected based on their frequency of use, relative complexity, ease of formulation and cost and compared to two real municipal wastewaters. Synthetic wastewaters vary significantly in their compositions and characteristics, especially in terms of alkalinity, BOD K ₁, SOUR, BODU, COD/BOD and C/N/P ratio, although they are portrayed as ‘typical’ in terms of characteristics and suitability for use. The pH, alkalinity and the presence of Ca and Mg should be considered in combination with the diluent used. Where the diluent is tap water, then the presence of treatment chemicals should also be considered. The effects of the micronutrients present are also an important factor. The study found that no single formulation is appropriate for all situations. Both the Syntho and Synthes formulations attempt to simulate real wastewater, whereas other formulations primarily act as readily biodegradable vectors for toxicity analyses, characterisation studies and treatment process evaluations. The criteria for choosing a particular synthetic wastewater very much depend on its intended application and require careful selection.

In Mexican waters, there is no a formal and well-established monitoring program of harmful algal blooms (HAB) events. Until now, most of the work has been focused on the characterization of organisms present in certain communities. Therefore, the development of new techniques for the rapid detection of HAB species is necessary. Capillary electrophoresis finger print technique (CE-SSCP) is a fingerprinting technique based on the identification of different conformers dependent of its base composition. This technique, coupled with capillary electrophoresis, has been used to compare and identify different conformers. The aim of this study was to determine if CE-SSCP analysis of ribosomal RNA (rRNA) gene fragments could be used for a rapid identification of toxic and harmful HAB species to improve monitoring activities along the coasts of Baja California Sur, Mexico.Three different highly variable regions of the 18S and 28S rRNA genes were chosen and their suitability for the discrimination of different dinoflagellate species was assessed by CE-SSCP.The CE-SSCP results obtained for the LSU D7 fragment has demonstrated that this technique with this gene region could be useful for the identification of the ten dinoflagellates species of different genera.We have shown that this method can be used to discriminate species and the next step will be to apply it to natural samples to achieve our goal of molecular monitoring for toxic algae in Mexican waters. This strategy will offer an option to improve an early warning system of HAB events for coastal BCS, allowing the possible implementation of mitigation strategies. A monitoring program of HAB species using molecular methods will permit the analysis of several samples in a short period of time, without the pressure of counting with a taxonomic expert in phytoplankton taxonomy.

This study examined the indoor concentrations of a wide range of volatile organic compounds (VOCs) in currently built new apartments every month over a 24-month period and the source characteristics of indoor VOCs. The indoor total VOC (TVOC) concentrations exhibited a decreasing tendency over the 24-month follow-up period. Similar to TVOCs, the median indoor concentrations of 33 of 40 individual VOCs (all except for naphthalene and six halogenated VOCs) revealed decreasing tendencies. In contrast, the indoor concentrations of the six halogenated VOCs did not reveal any definite trend with time. Moreover, the indoor concentrations of those halogenated VOCs were similar to the outdoor concentrations, suggesting the absence of any notable indoor sources of halogenated VOCs. For naphthalene (NT), the indoor concentrations were significantly higher than the outdoor concentrations, suggesting the presence of indoor NT source(s). The floor/wall coverings (39 %) were the most influential indoor source of indoor VOCs, followed by household cleaning products (32 %), wood paneling/furniture (17 %), paints (7 %), and moth repellents (5 %).