Separation and size characterization of colloidal particles in river water by sedimentation field-flow fractionation

Methodologies for using sedimentation field-flow fractionation (FFF) to produce fractograms of suspended river colloidal matter have been developed. These fractograms are plots representing the content of particulate material at different elution volumes following the separation. The volume scale can be converted to effective particle mass using equations derived from first principles and to the more usual particle diameter scale if a particle density is assumed. Sample preconcentration is generally necessary and various techniques have been tested. The usefulness of exponential field programming for samples containing a large particle size range has been demonstrated. The effect of programming conditions on resolution, speed, and accuracy are discussed. Fractograms obtained for Yarra River (Australia) colloidal matter are found to contain a broad peak in the range 0.1–0.5 μm dia. It is shown that the sedimentation FFF technique has considerable potential for the size characterization and fractionation of environmental samples.     

Antibiotic contamination and occurrence of antibiotic-resistant bacteria in aquatic environments of northern Vietnam

The ubiquitous application and release of antibiotics to the environment can result in bacterial antibiotic resistance, which in turn can be a serious risk to humans and other animals. Southeast Asian countries commonly apply an integrated recycling farm system called VAC (Vegetable, Aquaculture and Caged animal). In the VAC environment, antibiotics are released from animal and human origins, which would cause antibiotic-resistant bacteria (ARB). This study evaluated occurrence of ARB in the VAC environment in northern Vietnam, with quantitative analysis of antibiotic pollution. We found that sulfonamides were commonly detected at all sites. In dry season, while sulfamethazine was a major contaminant in pig farm pond (475-6662 ng/l) and less common in city canal and aquaculture sites, sulfamethoxazole was a major one in city canal (612-4330 ng/l). Erythromycin (154-2246 ng/l) and clarithromycin (2.8-778 ng/ml) were the common macrolides in city canal, but very low concentrations in pig farm pond and aquaculture sites. High frequencies of sulfamethoxazole-resistant bacteria (2.14-94.44%) were found whereas the occurrence rates of erythromycin-resistant bacteria were lower (< 0.01-38.8%). A positive correlation was found between sulfamethoxazole concentration and occurrence of sulfamethoxazole-resistant bacteria in dry season. The sulfamethoxazole-resistant isolates were found to belong to 25 genera. Acinetobacter and Aeromonas were the major genera. Twenty three of 25 genera contained sul genes. This study showed specific contamination patterns in city and VAC environments and concluded that ARB occurred not only within contaminated sites but also those less contaminated. Various species can obtain resistance in VAC environment, which would be reservoir of drug resistance genes. Occurrence of ARB is suggested to relate with rainfall condition and horizontal gene transfer in diverse microbial community.     

Measurement and interpretation of microbial adenosine tri-phosphate (ATP) in aquatic environments

There is a widespread need for cultivation-free methods to quantify viability of natural microbial communities in aquatic environments. Adenosine tri-phosphate (ATP) is the energy currency of all living cells, and therefore a useful indicator of viability. A luminescence-based ATP kit/protocol was optimised in order to detect ATP concentrations as low as 0.0001 nM with a standard deviation of <5%. Using this method, more than 100 water samples from a variety of aquatic environments (drinking water, groundwater, bottled water, river water, lake water and wastewater effluent) were analysed for extracellular ATP and microbial ATP in comparison with flow-cytometric (FCM) parameters. Microbial ATP concentrations ranged between 3% and 97% of total ATP concentrations, and correlated well (R² = 0.8) with the concentrations of intact microbial cells (after staining with propidium iodide). From this correlation, we calculated an average ATP-per-cell value of 1.75 × 10⁻¹⁰ nmol/cell. An even better correlation (R² = 0.88) was observed between intact biovolume (derived from FCM scatter data) and microbial ATP concentrations, and an average ATP-per-biovolume value of 2.95 × 10⁻⁹ nmol/μm³ was calculated. These results support the use of ATP analysis for both routine monitoring and research purposes, and contribute towards a better interpretation of ATP data.     

Behaviour of environmental aquatic nanocolloids when separated by split-flow thin-cell fractionation (SPLITT)

A split-flow thin-cell (SPLITT) system in different operating modes was used to size fractionate colloids and particles in a lake water. The unperturbed lake water sample and eluent fractions (nominally a<1 microm; b>1 microm) were analysed with atomic force microscopy (AFM) to assess the quality of the separation, in particular to quantify the contamination of the b (>1 microm) fraction with nanocolloids (defined here as material <100 nm in size). Particle size distribution (PSD) results from AFM indicated that there was substantial contamination with nanocolloids. This contamination was, most likely, from diffusive transport across flow regimes within the SPLITT and this is supported by the fact that vertical distances between laminar flow regimes within the SPLITT channel are similar in magnitude, but slightly larger than the mean distances travelled by diffusion during the residence time of particles within the channel. Nevertheless, AFM surface density data showed that the concentration of nanoparticles in the a fraction was 6-9 times higher than in the b fraction, depending on the SPLITT mode, indicating that contamination of the b fraction was limited. Fluorescence data using monodisperse, low molar mass standards confirm the AFM results, with substantial contamination of the b fraction by the fluorescent molecular probes. The increased contamination of the b fraction of the standard molecular probes compared to natural nanocolloids is likely because they are smaller and more diffusive than the average of the natural material. Due to this contamination and the likelihood that these small colloids bind a large fraction of metals, SPLITT can only be used for metal fractionation and speciation in combination with other methods capable of performing further metal speciation analysis.     

The environmental chemistry of copper (II) in aquatic systems

The speciation of copper(II) in fresh water has been examined by considering inorganic and organic complexation and adsorption and precipitation processes. It is concluded that in most aquatic systems these processes are capable of reducing free copper levels to very low values even in the presence of high levels of total copper.     

Ulva prolifera (Chlorophyta): a suitable material to remove Cd2+ from aquatic environments

Heavy metal pollution in aquatic environments is a significant environmental problem. Marine macroalgae are novel materials for the removal of heavy metals from water, aided by their large biomass and the feature of easy collection. In this study, Ulva prolifera O.F.Müller was used to remove cadmium ions (Cd²⁺) from the aquatic environment. We examined the Cd²⁺ absorption capacity of the thalli in a factorial experiment using fresh thalli cultivated in seawater, freshwater, water containing domestic garbage, water containing industrial waste and elutriant of soil with additional Cd²⁺. In addition, changes in photosynthetic activity of thalli were investigated. A significant decrease of maximum quantum yield and effective photochemical quantum yield of PSII (YII) indicated Cd²⁺ was transported into the cells and seriously inhibited photosynthesis. Furthermore, the Cd²⁺ absorption capacity was relatively high. The results indicated the suitability of U. prolifera for removing Cd²⁺ from aquatic environments of different backgrounds.     

Priorization of acoustic variables: Environmental decision support for the physical characterization of urban sound environments

Environmental noise is a factor with a significant impact on personal well-being. One of the principal challenges of urban planning is the creation of urban spaces capable of providing inhabitants with a high quality of life. Consequently urban spaces must be planned with an acceptable sound level and quality. For this purpose, it is necessary to design a tool capable of accurately characterizing the urban sound environment. This article describes a priorization of acoustic variables, which will ultimately help to make decisions in the characterization of environmental urban noise. This study describes the development of a model to characterize sound environments, in urban agglomerations, which takes into account both temporal and spatial structure. The results obtained point to the influence of the variables related to the evolution of sound pressure on the calculation of the sound pressure level. They also reflect the influence of the sound pressure level corrected by the variability of the sound pressure, as well as the benefits derived from an optimal selection of variables in the characterization of the sound environment.     

Cadmium(II) and zinc(II) adsorption by the aquatic moss Fontinalis antipyretica: effect of temperature, pH and water hardness

The biosorption of cadmium(II) and zinc(II) ions onto dried Fontinalis antipyretica, a widely spread aquatic moss, was studied under different values of temperature, initial pH and water hardness. The equilibrium was well described by Langmuir adsorption isotherms. Maximum biosorption capacity of cadmium was independent on temperature and averaged 28.0 mg g(-1) moss, whereas for zinc, capacity increased with temperature, from 11.5 mg g(-1) moss at 5 degrees C to 14.7 mg g(-1) moss at 30 degrees C. Optimum adsorption pH value was determined as 5.0 for both metal ions. Cadmium uptake was unaffected by the presence of calcium ions, but zinc sorption was improved when water hardness increased from 101.1 to 116.3 mg CaCO(3)l(-1). Inversely, as hardness increases, the competition with calcium ions strongly reduces the affinity of the biosorbent for zinc.     

Biological treatment of Mn(II) and Fe(II) containing groundwater: kinetic considerations and product characterization

In the present article, the treatment of groundwater containing Mn(II) and Fe(II) has been investigated. The biological oxidation of Mn(II) and Fe(II) in upflow filtration units comprised the applied experimental technique. The oxidation processes were mediated by specific bacteria, namely the Leptothrix ochracea and Gallionella ferruginea, which belong to the general category of manganese and iron oxidizing bacteria. This work was focused on the characterization of the products of biological oxidation and to the examination of the kinetics of Mn(II) removal as compared with Fe(II) removal from groundwaters. The products of biological oxidation were characterized using the spectroscopic techniques XRD, XPS and SEM-EDS and comprised a mixture of biogenic hydrous manganese and iron oxides. The oxidation state of manganese in the precipitates was found to be between 3 and 4. Iron oxides were mainly in the form of amorphous ferrihydrite. The kinetic results indicated that the rates of manganese and iron oxidation were several orders of magnitude greater than the respective for abiotic oxidation. The bacterially mediated oxidation of iron was faster than manganese oxidation, presenting half-lives of reaction 0.9 and 3.98 min, respectively.     

Thoron (Rn) decay products removal in poorly ventilated environments using unipolar ionizers: Dosimetric implications

Ionizers are proven to be effective in reducing the activity concentration of radon/thoron decay products in workplace environments. However, limited studies have been conducted on understanding the mechanism of removal and the related size dependency. This study demonstrates the feasibility of reducing the activity concentrations in small chambers and in room environments up to a factor of about 7. Field experiments in an uncontrolled ventilation area such as a thorium oxalate storage shed have also shown promising results with a possible concentration reduction by a factor of 4. However, these reductions have been necessarily associated with an increase (3-5 times) in the unattached fraction of the decay products which is a significant contributor to the lung dose. Owing to this, aspersions have been cast on the capability of the ionizers in reducing the effective dose. An attempt has been made here to estimate the effective doses over a wide range of parameters such as the initial unattached fraction, activity reduction ratio and the change in the unattached fraction, which get altered due to the use of ionizers. The study proves that for realistically achievable activity reduction ratios of about 3-5 with the employment of ionizers, the inhalation dose in workplace environments can be reduced by a factor of at least 4, as indicated by model calculations.     

Sorption of Zn(II), Pb(II), and Co(II) using natural sorbents: equilibrium and kinetic studies

Natural Jordanian sorbent (consisting of primary minerals, i.e., quartz and aluminosilicates and secondary minerals, i.e., calcite and dolomite) was shown to be effective for removing Zn(II), Pb(II) and Co(II) from aqueous solution. The major mineral constitutions of the sorbent are calcite and quartz. Dolomite was present as minor mineral and palygorskite was present as trace mineral. The sorbent has microporous structure with a modest surface area of 14.4 m(2)g(-1). pH(zpc) (pH of zero point charge) of the sorbent was estimated by alkaline-titration methods and a value of 9.5 was obtained. The sorption capacities of the metals were: 2.860, 0.320, 0.076 mmol cation g(-1) for Zn(II), Pb(II) and Co(II) at pH 6.5, 4.5 and 7.0, respectively. The shape of the experimental isotherm of Zn(II) was of a "L2" type, while that of Pb(II) and Co(II) was of a "L1" type according to Giles classification for isotherms. Sorption data of metals were described by Langmuir and Freundlich models over the entire concentration range. It was found that the mechanism of metal sorption was mainly due to precipitation of metal carbonate complexes. The overall sorption capacity decreased after acid treatment, as this decreased the extent of precipitation on calcite and dolomite. The effect of Zn(II) ions concentration on sorption kinetics was investigated. Kinetic data were accurately fitted to pseudo-first order and external diffusion models which indicated that sorption of Zn(II) occurred on the exterior surface of the sorbent and the contribution of internal diffusion mechanism was insignificant. Furthermore, the sorption rate of Zn(II) was found to be slow, where only 10-20% of the maximum capacity was utilized in the first 30 min of interaction.     

Implications of natural organic matter binding heterogeneity on understanding lead(II) complexation in aquatic systems

Organochlorines (HCH isomers, DDX and individual PCBs) were determined in pine needle litter and upper soil layers of three forest test areas in central Germany. The contents accumulating over a number of years or even decades in the organic surface layer are compared with the levels of new inputs from needle fall as well as with the levels of older inputs in the upper mineral soil layer. Differences in behaviour between the soil horizons are discussed, especially concerning the DDX and HCH groups. With approximately comparable Corg values (approx. 21-24%) the pH value in the range of 4.24-2.90 in the O-horizon of the forest soils exerts a large influence. Hence the A-horizon represents--for p,p'-DDT and gamma-HCH in particular--at pH values of 2.90 a pollutant reservoir which should not be underestimated and which could endanger the rhizosphere and the groundwater. According to PCBs, in the more acidic soils with a pH value <4.0 the lipophilic higher polychlorinated biphenyls were found to be more highly enriched in the humus layer.     

Adsorption from Brazilian soils of Cu(II) and Cd(II) using cattle manure vermicompost

The potential of cattle manure vermicompost and Brazilian soils (whole soils and soils incubated with vermicompost) was assessed for adsorption of heavy metals such as Cu(II) and Cd(II) from aqueous solutions. Experimental data have been fitted to Langmuir and Freundlich isotherms to obtain the characteristic parameters of each model, with R ² values from 0.89 to 0.99. Based on the maximum adsorption capacity obtained from the Langmuir isotherm the affinity of the studied metals for the vermicompost and soils have been established as Cu(II) > Cd(II). The values of the separation factor, R _L, which has been used to predict affinity between adsorbate and adsorbent were between zero and 1, indicating that sorption was very favourable for Cu(II) and Cd(II) in synthetic solution. Addition of vermicompost to soils resulted in higher distribution coefficient, K _d, as compared with whole soils. The thermodynamic parameter, the Gibbs energy changes, was calculated for each system and the negative values obtained confirm that the adsorption processes are spontaneous. The ΔG° values for the substrates were between ?2.630±1.41 kJ mol^?1 and ?13.700±1.250 kJ mol^?1. Adsorption tests from multimetal systems confirm the affinity order obtained in the individual metal tests. The adsorption capacity for Cu(II) measured in individual tests is not reduced by the presence of Cd(II). There is also desorption of Cu(II) and Cd(II) previously bound to vermicompost, whole soils and soils incubated with vermicompost by DTPA. The experiment indicates the importance of cattle manure vermicompost and oxisol amended with vermicompost in relation to Cu(II) and Cd(II) adsorption from aqueous solution.     

Monitoring of polychlorinated biphenyls (PCBs) and hexachlorocyclohexanes (HCH) in freshwater using the aquatic moss Cinclidotus danubicus

Concentrations of PCBs and α-, β, and γ-HCH have been measured in the aquatic moss Cinclidotus danubicus to examine its potential use an indicator of chlorinated organic pollutants in freshwaters. Samples of Cinclidotus were collected from an uncontaminated stretch of the Saône R. (France) and transplanted in the Durance R., which receives effluents of an insecticide factory. Mosses were sampled 13, 24 and 51 days after the transplant and analysed by capillary column gas chromatography. Concentrations in Cinclidotus transplanted 4 km downstream from the factory reached 0.30 μg g^?1 for PCBs, 2.37 μg g^?1 for α-HCH, 1.29 μg g^?1 for β-HCH and 0.50 μg g^?1 for γ-HCH; mean accumulation factors were 616 for α-HCH, 493 for β-HCH, 294 for γ-HCH and 4867 for PCBs. The preponderence of α- and β-HCH over the other pollutants investigated was also observed in water samples, which shows that aquatic mosses can be used as indicators of chlorinated organic pollutants in freshwaters.     

Analysis for chromium traces in the aquatic ecosystem II. A study of Cr(III) and Cr(VI) in the susquehanna river basin of New York and Pennsylvania

A new procedure for the differential analysis of ppb concentrations of Cr(III) and Cr(VI) in natural waters has been developed. In this method, three-liter samples are filtered, acidified to pH 6.0, and divided into three parts. One liter is passed through an anion-exchange resin bed (AG-1X4, 100–200 mesh, Cl^? form), one liter is passed through a cation-exchange resin bed (50 WX4, 100–200 mesh, Na⁺ form), and one liter remains untreated. 10 ml of 1.0 M HNO₃ are then added to each of the three aliquots and they are individually reduced in volume by evaporation to 10 ml. Analysis by A.A. employing the method of standard addition follows. By difference, cationic, anionic, and non-ionic Cr concentrations in the sample become available. Cr(III) concentration is probably closely related to (cationic + non-ionic), and Cr(VI) concentration in the original sample corresponds to the anionic portion. Precision is ±20 % or better for total, cationic, and anionic Cr at the 1 ppb level. Precision of the non-ionic analyses is closely linked to these other precisions as the concentration of non-ionic Cr species in the original sample is obtained by the mass balance requirement set up by the other three analyses.Application of this technique to the analysis of natural water samples revealed the predominance of trivalent Cr in uncontaminated waters of the Upper Susquehanna River Basin (1–2 ppb). River water samples taken downstream of Binghamton, N.Y. area sewage outfalls revealed an increase in the mean Cr(VI) content of the river from ～0.5 ppb to ～1.6 ppb. The persistence of the Cr(VI) at least as far as 60 km downstream of the outfall area leads to the conclusion that at these levels, little dissolved Cr(VI) is removed from the river as it flows away from a point of contamination. Concentrations of Cr in samples of river sediments also revealed Cr contamination below the outfall area, and Cr contamination extended at least as far as 60 km downstream of the outfall area.     

Photo-dissolution of flocculent, detrital material in aquatic environments: contributions to the dissolved organic matter pool

This study shows that light exposure of flocculent material (floc) from the Florida Coastal Everglades (FCE) results in significant dissolved organic matter (DOM) generation through photo-dissolution processes. Floc was collected at two sites along the Shark River Slough (SRS) and irradiated with artificial sunlight. The DOM generated was characterized using elemental analysis and excitation emission matrix fluorescence coupled with parallel factor analysis. To investigate the seasonal variations of DOM photo-generation from floc, this experiment was performed in typical dry (April) and wet (October) seasons for the FCE. Our results show that the dissolved organic carbon (DOC) for samples incubated under dark conditions displayed a relatively small increase, suggesting that microbial processes and/or leaching might be minor processes in comparison to photo-dissolution for the generation of DOM from floc. On the other hand, DOC increased substantially (as much as 259 mgC gC⁻¹) for samples exposed to artificial sunlight, indicating the release of DOM through photo-induced alterations of floc. The fluorescence intensity of both humic-like and protein-like components also increased with light exposure. Terrestrial humic-like components were found to be the main contributors (up to 70%) to the chromophoric DOM (CDOM) pool, while protein-like components comprised a relatively small percentage (up to 16%) of the total CDOM. Simultaneously to the generation of DOC, both total dissolved nitrogen and soluble reactive phosphorus also increased substantially during the photo-incubation period. Thus, the photo-dissolution of floc can be an important source of DOM to the FCE environment, with the potential to influence nutrient dynamics in this system.     

光致发光技术PL(PhotoLuminescence)分析结晶硅片及电池片

类稳态光致发光技术(QSS-PL)是一项很有效,定量分析硅片及电池片的工具。类稳态光致发光技术(QSS-PL)的运用不仅在研究开发方面,也适合在线硅片高速分选。     

Mixed-mode (I + II) fracture characterization of wood bonded joints

In this work fracture characterization of wood bonded joints is performed. The main objective is to define a fracture criterion under mixed-mode loading (I + II), in order to provide a safer and reliable design of wood bonded joints. Experimental fracture characterization tests were carried out. For mode I and mode II loading, the double cantilever beam and the end notched flexure tests were selected. Under mixed-mode I + II loading the mixed-mode bending test was used considering different mixed-mode ratios. A data reduction scheme based on the specimen compliance, the beam theory and on a crack equivalent concept was used to overcome the difficulties inherent to the above referred tests. The fracture linear energetic criterion showed to be adequate to describe the fracture envelop with an exception, as discussed in the paper.     

BHC(1,2,3,4,5,6-hexachlorocyclohexane) residue concentrations and their seasonal variation in aquatic environments in the kitakyushu district, Japan, 1970–1973

The BHC (χ-, β-, γ- and δ-isomer of 1,2,3,4,5,6-hexachlorocyclohexane) concentration in river water, reservoir and tap water in the Kitakyushu District was investigated during 1970–1973. The levels in surface water were high in summer and low in autumn, winter and spring. In tap water, little difference was observed compared with the raw water. These results demonstrate that the usual treatment process, rapid sand-filteration and disinfection with chlorine, has little effect on the removal of BHC. The yearly maximum concentration in surface water occurred in summer, the logarithm of these declined linearly over a period of years. The levels of BHC concentration in the bottom sediments were much higher than those in surface water, suggesting that BHC in surface water was concentrated in the bottom sediments.     

Production and detailed characterization of bean husk-based carbon: efficient cadmium (II) removal from aqueous solutions

We report the production of a modified carbon by heat treating bean husk (Phaseolus vulgaris) at 270 degrees C in Ar, followed by chemical activation using HNO(3). The material was studied using thermogravimetric analysis (TGA), infrared spectroscopy (IRS), high-resolution transmission electron microscopy (HRTEM), elemental mapping, energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction and scanning electron microscopy (SEM). Cd(2+) sorption studies with this material were carried out at different concentrations. It was found that cadmium (II) is effectively removed by the modified material obtained from bean husk (180 mg/g). The sorption mechanism is discussed in terms of the activated surface properties. A relationship between the oxygen content and sorption was found in this novel material. Commercial activated carbon (AC) (F400) was used for comparison.