BACKGROUND: This work focuses on the accumulation and mobility properties of arsenic (As) and the effects of phosphate (P) on its movement in Pennisetum clandestinum Hochst (kikuyu grass), grown hydroponically under increasing arsenate (As(V)) concentrations. The uptake of both ions and the relative kinetics show that phosphate is an efficient competitive inhibitor of As(V) uptake. The P/As uptake rate ratios in roots indicate that P is taken up preferentially by P/As transporters. An arsenite (As(III)) efflux from roots was also found, but this decreased when the arsenate concentration in the solution exceeded 5 μM. METHODS: Increases in both arsenite and arsenate concentrations in roots were observed when the arsenate concentration in the solution was increased, and the highest accumulation of As(III) in roots was found when plants were grown at 5 μM As(V). The low ratios of As accumulated in shoots compared to roots suggest limited mobility of the metalloid within Kikuyu plants. RESULTS: The results indicate that arsenic resistance in kikuyu grass in conditions of moderate exposure is mainly dependent on the following factors: 1) phosphate nutrition: P is an efficient competitive inhibitor of As(V) uptake because of the higher selectivity of membrane transporters with respect to phosphate rather than arsenate; and 2) a detoxification mechanism including a reduction in both arsenate and arsenite root efflux. CONCLUSIONS: The As tolerance strategy of Kikuyu limits arsenate uptake and As translocation from roots to shoots; therefore, this plant cannot be considered a viable candidate for use in the phytoextraction of arsenic from contaminated soils or water.

Common vetch (Vicia sativa L.) is a legume species with an extensive agricultural use. However, the phytoremediation potentiality of this species has not been sufficiently explored because little is known about its resistance to inorganic and organic pollutants. In the present work, phenol tolerance of common vetch was assayed at different stages of growth. Germination index and germination rate decreased only at high phenol concentrations (250 and 500 mg L − 1), whereas 30-day-old plants were able to tolerate this pollutant, with high removal efficiencies. The activities of antioxidative enzymes, such as peroxidase (POD) and ascorbate peroxidase, increased significantly with the highest phenol concentration, whereas superoxide dismutase activity, malondialdehyde, and H2O2 levels remained unaltered. Besides, an increase in two basic isoforms of POD was observed in plants treated with phenol. The results suggested that common vetch has an efficient protection mechanism against phenol-induced oxidative damage. Moreover, it could tolerate and remove high phenol concentrations, avoiding serious phytotoxic effects. Thus, V. sativa could be considered an interesting tool in the field of phytoremediation.

PURPOSE: The potential of using waste Saccharomyces cerevisiae as adsorbent for the adsorption of As(III) from aqueous solution was assessed. METHODS: The biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy analysis. Various parameters including pH, biosorbent dosage, contact time, and temperature were systematically investigated. RESULTS AND CONCLUSIONS: The FTIR results of S. cerevisiae biomass showed that biomass has different functional groups, and these functional groups are able to react with metal ion in aqueous solution. Several biosorption isotherms were used to fit the equilibrium data, showing sorption to be monolayer on the heterogeneous surface of the biosorbent. The maximum biosorption capacity calculated using Langmuir model was found to be 62.908 μg/g at pH 5.0, biosorbent dosage 5 g/L, contact time 240 min, and temperature 35 °C. The kinetic studies indicated that the biosorption process of the As(III) followed well the pseudo-second-order equation. The intraparticle diffusion and Richenberg models were applied to the data, and we found that the biosorption of As(III) was governed by film diffusion followed by intraparticle diffusion. The thermodynamics constants indicated that the biosorption of As(III) onto S. cerevisiae was spontaneous and endothermic under examined conditions. Biosorbent could be regenerated using 0.5 M NaOH solution, with up to 75 % recovery.

PURPOSE: The impact of CO₂ urban plume in a rural area was investigated by concentrations recorded near surface. METHODS: CO₂ dry concentrations at three levels near surface were recorded for about 8 months at a rural site. Daily cycles were obtained and directional analysis was made with percentiles. Several functions were used to fit background and plume concentrations and the goodness of fit was evaluated with different statistics, which were also compared. RESULTS: Daily cycle showed a difference of around 2 ppm during the night between the lowest (1.8 m) and the highest (8.3 m) levels. Weighting functions of the directional analysis revealed the influence of the Valladolid urban plume. Two regions were established, with local factors prevailing below 3 m s⁻¹ and transport dominating above 6 m s⁻¹. The best fit was achieved with a quadratic function for the background and a cubic function for the plume due to the lack of symmetry observed. Gamma and Weibull distributions were also successfully used. Some statistics, such as the root mean square error (RMSE), stood out when evaluating the goodness of fit, whilst others were discarded due to their extremely low values and the lack of sensitivity against the functions used. Finally, a comprehensive metric merging several statistics was also tested with slight differences against RMSE.

INTRODUCTION: In this work, we report in situ studies of UV photoelectrocatalytic discoloration of a dye (indigo carmine) by a TiO2 thin film in a microreactor to demonstrate the driving force of the applied electrode potential and the dye flow rate toward dye discoloration kinetics. METHODS: TiO2 65-nm-thick thin films were deposited by PVD magnetron sputtering technique on a conducting glass substrate of fluorinated tin oxide. A microreactor to measure the discoloration rate, the electrode potential, and the photocurrent in situ, was developed. The dye solutions, before and after measurements in the microreactor, were analyzed by Raman spectroscopy. RESULTS: The annealed TiO2 thin films had anatase structure with preferential orientation (101). The discoloration rate of the dye increased with the applied potential to TiO2 electrode. Further, acceleration of the photocatalytic reaction was achieved by utilizing dye flow recirculation to the microreactor. In both cases the photoelectrochemical/photocatalytic discoloration kinetics of the dye follows the Langmuir–Hinshelwood model, with first-order kinetics. CONCLUSIONS: The feasibility of dye discoloration on TiO2 thin film electrodes, prepared by magnetron sputtering using a flow microreactor system, has been clearly demonstrated. The discoloration rate is enhanced by applying a positive potential (E AP) and/or increasing the flow rate. The fastest discoloration and shortest irradiation time (50 min) produced 80% discoloration with an external anodic potential of 0.931 V and a flow rate of 12.2 mL min−1.

PURPOSE: Degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in soils by Fe3O4 nanoparticles combined with soil indigenous microbes was investigated, and the effects of Fe3O4 nanoparticles on soil microbial populations and enzyme activities were also studied. METHODS: The soils contaminated with 2,4-D were treated with Fe3O4 nanoparticles. The microbial populations and enzyme activities were analyzed by dilution plate method and chemical assay, respectively, and the concentration of 2,4-D in soil was determined by high-performance liquid chromatography (HPLC). RESULTS: The results indicated that Fe3O4 nanoparticles combined with soil indigenous microbes led to a higher degradation efficiency of 2,4-D than the treatments with Fe3O4 nanoparticles or indigenous microbes alone. The degradation of 2,4-D in soils followed the pseudo first-order kinetic. The half-lives of 2,4-D degradation (DT50) of the combined treatments were 0.9, 1.9 and 3.1 days in a Red soil, Vertisol and Alfisol, respectively, which implied that the DT50 of the combination treatments were significantly shorter than that of the treatments Fe3O4 nanoparticles or indigenous microbes alone. The effects of Fe3O4 nanoparticles on soil microbial populations and enzyme activities were also investigated and compared with the α-Fe2O3 nanoparticles. The results suggested that the α-Fe2O3 nanoparticles had only comparatively small effects on degradation of 2,4-D in soils, while the Fe3O4 nanoparticles not only degraded 2,4-D in soils but also increased the soil microbial populations and enzyme activities; the maximum increase in enzyme activities were 67.8% (amylase), 53.8% (acid phosphatase), 26.5% (catalase) and 38.0% (urease), compared with the untreated soil. Moreover, the introduction of Fe3O4 nanoparticles at the different dosage resulted in a variable degradation efficiency of 2,4-D in soil. CONCLUSION: The method of combining Fe3O4 nanoparticles with indigenous soil microbes may offer great benefits for the application of nanotechnology in remediation of herbicide contaminated soil.

Residues of tetracyclines reach soils as a result of animal waste application. Sorption is a key process in transport, fate, and effects of contaminants in the environment. In this work, we have attempted to predict the sorption of four widely used tetracyclines (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) from soil physicochemical properties. Batch sorption experiments were performed on 15 natural soils with a broad range of physicochemical properties, and the data were fitted to several isotherm models. Multivariate analysis methods were conducted to identify the main factors affecting the sorption distribution coefficients (K d) of the tetracyclines at two aqueous concentration levels (100 and 400 μg L−1). All four tetracycline sorption isotherms in alkaline and acidic soils were well described by the Freundlich and Langmuir equation, respectively. At intermediate soil pH (from 5.3 to 7), oxytetracycline and tetracycline exhibited Freundlich behavior, whereas chlortetracycline and doxycycline followed a Langmuir model. Two partial least squares (PLS) models were developed. The first one uses five soil descriptors as input variables; the second uses, pH, cation exchange capacity (CEC), and log K d,OTC. Both models satisfactorily predicted distribution coefficients within a factor of 1.5. Sorption of tetracyclines in soil is governed by several factors, in the following order of importance: solution speciation, CEC (dominant at acidic–neutral soil pH), transition metal content, and texture. The PLS models indicated that tetracycline sorption can be predicted using a minimal set of soil descriptors including oxytetracycline sorption data.

INTRODUCTION: Exposure to trace metals and polycyclic aromatic hydrocarbons (PAHs) adsorbed on particulates is of a serious health concern. Levels of some trace metals in total suspended particulate and 13 PAHs of fine particulate matter were measured from nomadic tents in the southern Tibetan Plateau in summer 2010. RESULTS AND DISCUSSION: The indoor air within the tents was seriously polluted, mainly due to yak dung combustion. Average trace metal concentrations were much higher (range of indoor/outdoor ratio 61–291) than those of the outdoor air. Additionally, enrichment factors of most trace metals of indoor air were similar to those of outdoor air, indicating outdoor air quality of the studied area was possibly influenced by pollutants emitted from local tents. Mean concentrations of total PAHs and BaP within tents was 5372.45 and 364.79 ng/m3, hundred times higher than that of outdoor air of the Tibetan Plateau. Three- and four-ring PAHs were the predominant components. The diagnostic ratio of BaA/(BaA + Chr) was 0.33. Since Tibetan women typically spend longer time within the tents, they were exposed to PAHs (BaP exposure = 1.81 μg/m3) about two times of other family members. Among all the PAHs, Bap contributed the most (82.6%) of the total carcinogenicity. Similarly, the excess lifetime cancer risk for women and other family members were 2.75 × 10−4 and 1.27 × 10−4, respectively, indicating Tibetan herdsmen, especially women who are in charge of most house chores were at risk for adverse health effects.

Hexabromocyclododecanes (HBCDs), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), and decabromodiphenyl ethane (DBDPE) used as alternatives for polybrominated diphenyl ethers (PBDEs) are also persistent in the environment as PBDEs. Limited information on these non-PBDE brominated flame retardants (BFRs) is available; in particular, there are only few publications on environmental pollution by these contaminants in the coastal waters of Asia. In this regard, we investigated the contamination status of HBCDs, BTBPE, and DBDPE in the coastal waters of Asia using mussels as a bioindicator. Concentrations of HBCDs, BTBPE, and DBDPE were determined in green (Perna viridis) and blue mussels (Mytilus edulis) collected from the coastal areas in Cambodia, China (mainland), SAR China (Hong Kong), India, Indonesia, Japan, Malaysia, the Philippines, and Vietnam on 2003–2008. BTBPE and DBDPE were analyzed using GC-MS, whereas HBCDs were determined by LC-MS/MS. HBCDs, BTBPE, and DBDPE were found in mussels at levels ranging from <0.01 to 1,400, <0.1 to 13, and <0.3 to 22 ng/g lipid wt, respectively. Among the three HBCD diastereoisomers, α-HBCD was the dominant isomer followed by γ- and β-HBCDs. Concentrations of HBCDs and DBDPE in mussels from Japan and Korea were higher compared to those from the other Asian countries, indicating extensive usage of these non-PBDE BFRs in Japan and Korea. Higher levels of HBCDs and DBDPE than PBDEs were detected in some mussel samples from Japan. The results suggest that environmental pollution by non-PBDE BFRs, especially HBCDs in Japan, is ubiquitous. This study provides baseline information on the contamination status of these non-PBDE BFRs in the coastal waters of Asia.

PURPOSE: Air pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. The mass artificial plantation is very helpful to absorb dust and reduce pollution for conservation of the urban environment. The foliar surface of plants is an important receptor of atmospheric pollutants. Therefore, selection of suitable plant species for urban environment is very important. METHODS: The dust-retaining capability of urban trees in Guangzhou was determined at four different types of urban area, and the morphological traits of their leaves such as wax, cuticle, stomata, and trichomes were observed under a scanning electron microscope. RESULTS: It was determined that the dust-retaining capability of any given tree species is significantly different in the same place. Of the four studied tree species in the industrial area (IA) and commercial/traffic areas (CTA) type urban areas, the highest amounts of dust removed by Mangifera indica Linn was 12.723 and 1.482 g/m2, respectively. However, in contrast, the equivalent maxima for Bauhinia blakeana is only 2.682 g/m2 and 0.720 g/m2, respectively. Different plant species have different leaf morphology. The leaf of M. indica has deep grooves and high stomata density which are in favor of dust-retained, and thus, their dust-retained capability is stronger, while B. blakeana has the cells and epicuticular wax with its stomata arranging regularly, resulting in poor dust catching capability. Leaf size was also shown to be related to dust capture for the four studied tree species. CONCLUSIONS: The dust removal capacity of individual tree species should be taken into account in the management of greening plantation in and around an urban area. It was also shown that temporal variation in dust accumulation occurred over the 28-day observation period and this was discussed. Furthermore, spatial contrasts in dust accumulation were evidenced by the data. This reflected the differing pollution loadings of the four urban-type areas. The highest amount of dust accumulation was associated with the industrial area in which shipyard and steelworks occurred whilst the lowest dust accumulation was associated with the grounds of the University which was the control area.