Association of Am with humic substances isolated from river waters with different water quality

The association properties of Am with aquatic humic substances in a 0.01M NaClO₄ solution at pH 6-8 were studied on the basis of molecular size distribution. Ten humic substances isolated from river water with different water quality (pH 3.9-8.0 and dissolved organic carbon (DOC) concentration of 2-40 mg/l) were used for comparing their effects on the association of Am. The molecular size distribution of Am in the presence of humic substances from an uncolored river water (DOC 2 mg/l) was different from that at the experimental systems using humic substances from brownish and high DOC (14-40 mg/l) river waters.     

Determination of selenium in freshwaters by cathodic stripping voltammetry after UV irradiation

An analytical method was developed for the determination of total dissolved selenium in fresh waters, using linear sweep cathodic stripping voltammetry (CSV) in combination with UV photolytic digestion. Both the CSV method, based on the electrodeposition and stripping of Cu(2)Se, and the UV irradiation procedure were investigated in detail. In the presence of dissolved organic substances, as in freshwaters, Se(VI) is reduced to Se(IV) by UV irradiation in 0.1M hydrochloric acid. Glucose can be used as the carbon source in samples low in natural dissolved organic carbon (DOC). The photolytic yields of Se(IV) were about 90% in both cases. Five freshwater samples were analysed for total selenium by CSV after UV photolysis, and by hydride generation atomic absorption spectrometry (HG-AAS) after oxidative digestion followed by reduction with hydrochloric acid. The results agreed well and the concentrations were in the range 70-190 ng/l., well above the detection limit of the CSV method at 2 ng/l.     

Comparison of changes in metal toxicity following exposure of water with high dissolved organic carbon content to solar, UV-B and UV-A radiation

This study examines the effects of natural solar radiation on the metal-binding capacity of dissolved organic matter (DOM). Newington Bog water (35.5 mg L⁻¹ dissolved organic carbon [DOC]) was irradiated for 20 days under UV-B lamps in the laboratory and under natural solar radiation. In the presence of irradiated DOM, IC₅₀ (contaminant concentration required to reduce algal growth by 50%) was significantly decreased with UV-B treatment for four metals: Pb, 64%; Cu, 63%; Ni, 35% and Cd, 40%. Solar radiation also significantly decreased IC₅₀ of Pb (58%) and Cu (49%), DOC concentration (11%), DOM fluorescence (DOMFL, 33%) and DOC-specific UV absorbance. Further experiments on Raisin River water (20.7 mg DOC L⁻¹) exposed to 20 days of artificial UVA and UV-B radiation produced significant decreases in IC₅₀ for Cu (48%) with UV-A and for Pb (43%) with UV-B. DOC concentration was decreased 20% by UV-B and 24% by UV-A. DOMFL decreased 51.5% in the first 5 days of UV-A exposure, an effect that was not observed with the UV-B treatment. The UV-A treatment decreased UV absorbance more at longer wavelengths and over a broader wavelength band than did the UV-B treatment. Change in toxicity with UV irradiation was inconsistent among the metals tested in this study, indicating that some organic metal-binding ligands were more quickly removed or altered than others. The DOM remaining after irradiation appears to be qualitatively different from the unirradiated DOM. The much greater irradiance of UV-A makes its contribution to the removal and/or alteration of DOM at least as important as the influence of higher energy UV-B.     

Effective UV photolytic decomposition of organic compounds with a low-pressure mercury lamp as pretreatment for voltammetric analysis of trace metals

The effectivity of UV irradiation with low and high pressure mercury (L-Hg and H-Hg) lamps on the decomposition of organic compounds in aqueous solutions, as pretreatment for the voltammetric determination of trace metals, is compared. The photolytic decomposition with the L-Hg lamp was much faster than with the H-Hg lamp. The higher efficiency of the L-Hg lamp is caused by its greater light intensity at short wavelengths. Interferences of organic compounds on the voltammetric determination of nickel and indium were eliminated successfully by 90 min irradiation with the L-Hg lamp. Humic acid and organic interference with the voltammetric determination of nickel in natural river water were successfully eliminated. The decomposition using the L-Hg lamp can be carried out without added oxidizing reagents and at room temperature, thus eliminating loss of water samples by evaporation at higher temperature.     

Investigations of oxidative UV photolysis

Summary Oxidative UV photolysis according to DIN standard 38406 E 16 [1] has been investigated as a sample preparation method for voltammetry. UV photolysis has decisive advantages compared with mineral acid digestion owing to the simple procedure and the very low blank values, which in turn are due to the minimal reagent addition required. For UV photolysis with a high pressure mercury lamp, an apparatus has been used that employs a new type of sample cooling and that allows the simultaneous irradiation of 12 samples. The sample preparation for the voltammetric determination of zinc, cadmium, lead, copper, nickel and cobalt has been optimized using a model water solution and subsequently tested with real matrices. The type of organic matrix and the irradiation temperature determine the irradiation time required. To digest aromatic compounds, it is advantageous to work at reaction temperatures of ca. 90°C. The application of UV photolysis centers on water samples slightly polluted with organic compounds; however, it can also be used with more heavily polluted wastewaters. As the digestion times are at most 60 min, the method is of interest for routine analysis.     

185 nm UV降解水中4-CP、4-NP和Rh B的研究

本文以对氯苯酚(4-CP)、对硝基苯酚(4-NP)和罗丹明B(Rh B)为模型有机物(以4-CP和4-NP为小分子模型有机物,以Rh B为大分子模型有机物),分别研究了185 nm UV对水中这3种模型有机物的降解规律、性能和效果.研究结果表明,185 nm UV直接对水中4-CP、4-NP和Rh B有很好的降解效果.研究内容包括:185 nm UV降解模型有机物的浓度、TOC(Total organic carbon)浓度、185 nm UV降解模型有机物过程中溶液pH及电导率变化、以及降解模型有机物过程中产生的无机离子等几个方面.     

Ultraviolet photolysis of urine for suppression of color quenching prior to liquid scintillation counting of tritium

In order to reduce the color quenching in the measurement of tritium in urine by liquid scintillation counting , UV irradiation was applied to decompose the organic substances in the sample. Urine was decolorized under UV irradiation in the presence of hydrogen peroxide. As a result, color quenching was considerably suppressed and higher counting efficiency of tritium was obtained. This UV treatment made it possible to increase the urine content in the sample from 2 to 40% (v/v) without significant decrease of counting efficiency. Either higher sensitivity or shorter analysis time was achieved in the tritium measurement by the augmentation of urine content. When the measurement time was 30 min, the detection limit of tritium defined as 3s was 0.03 Bq/ml. At the expense of some sensitivity (set at a detection limit of 0.3 Bq/ml), the measurement time was shortened to 0.5 min. These results will make a great improvement to routine tritium monitoring as well as to emergency monitoring in mass tritium exposure.      

Effect of HF treatment on the activity of TiO2 thin films for photocatalytic water splitting

The effects of HF treatment on the activity of TiO₂ thin films for the photocatalytic water splitting reaction have been investigated. TiO₂ thin films treated with HF solution (HF-TiO₂) were found to exhibit a remarkable enhancement of the photocatalytic activity for H₂ evolution from a methanol aqueous solution, as well as efficient photoelectrochemical performance under UV light irradiation as compared with the untreated TiO₂. Moreover, Pt-loaded HF-TiO₂ thin films were found to act as efficient and stable photocatalysts for the decomposition of water under UV light irradiation. The mechanistic insights obtained in the present study will be useful in the design of highly efficient photocatalysts for the decomposition of water.     

The role of solar UV radiation in the ecology of alpine lakes.

Solar ultraviolet radiation (UVR, 290-400 nm) is a crucial environmental factor in alpine lakes because of the natural increase of the UVR flux with elevation and the high water transparency of these ecosystems. The ecological importance of UVR, however, has only recently been recognized. This review, examines the general features of alpine lakes regarding UVR, summarizes what is known about the role of solar UVR in the ecology of alpine lakes, and identifies future research directions. Unlike the pattern observed in most lowland lakes, variability of UV attenuation in alpine lakes is poorly explained by differences in dissolved organic carbon (DOC) concentrations, and depends mainly on optical characteristics (absorption) of the chromophoric dissolved organic matter (CDOM). Within the water column of lakes with low DOC concentrations (0.2-0.4 mg l(-1)), UV attenuation is influenced by phytoplankton whose development at depth (i.e. the deep chlorophyll maximum) causes important changes in UV attenuation. Alpine aquatic organisms have developed a number of strategies to minimize UV damage. The widespread synthesis or bioaccumulation of different compounds that directly or indirectly absorb UV energy is one such strategy. Although most benthic and planktonic primary producers and crustacean zooplankton are well adapted to high intensities of solar radiation, heterotrophic protists, bacteria, and viruses seem to be particularly sensitive to UVR. Understanding the overall impact of UVR on alpine lakes would need to consider synergistic and antagonistic processes resulting from the pronounced climatic warming, which have the potential to modify the UV underwater climate and consequently the stress on aquatic organisms.     

Radiation decomposition of humic substances in landfill disposal leachate. TOC reduction and CO2 formation (author's transl)]

The leachate generated from landfill contains humic substances such as humic acid and fluvic acid. It shows, in general, high chemical oxygen demand (COD) and biological oxygen demand (BOD), and colors in dark brown. When the leachate collected on the No. 15 landfill in Tokyo Bay was irradiated by gamma-rays from a 60Co source in bubbling air, the total organic carbon (TOC) decreased with increasing dose and the brown color was bleached. The effects of pH, flow rate, and dose rate on the decrease of TOC, the variations of UV spectrum, and the formation of carbon dioxide by the irradiation were examined. The decreasing rate of TOC increased with an increase of the flow rate up to approximately 1l/min and showed a maximum value in the region of pH 4 approximately 6. It was also dependent on the dose rate and increased with a decrease of the dose rate. The radiation chemical yield, G(--TOC), reached 162 at low dose rate of 1.3 X10(4) rad/h. This result suggests that a radiation-induced chain reaction occurred. The amount of TOC decreased was almost equal to that of carbon dioxide formed. This result shows that the organic substances were decomposed by irradiation to carbon dioxide as a final product and it was ejected from the solution.     

Determination of heavy metal complexes with humic substances by HPLC/ICP-MS coupling using on-line isotope dilution technique

An isotope dilution mass spectrometric (IDMS) method has been developed for the simultaneous determination of the complexes of 11 heavy metals (Ag, Cd, Cu, Mo, Ni, Pb, Tl, U, W, Zn and Zr) with humic substances (HS) by coupling HPLC with ICP-MS and applying the on-line isotope dilution technique. The HPLC separation was carried out with size exclusion chromatography. This HPLC/ICP-IDMS method was applied to samples from a brown water, ground water, sewage and seepage water as well as for a sample containing isolated fulvic acids. The total contents of heavy metals and of their complexes were analyzed in these samples with detection limits in the range of 5–110 ng/L. The analysis of heavy metal/HS complexes from the different waters resulted in characteristic fingerprints of the distribution pattern of heavy metals in the separated HS fractions. A comparison between the total heavy metal concentrations and their portions bound to humic substances showed distinct differences for the various metals. Simultaneous ¹²C detection was used for the characterization of HS complexes not identified by UV detection and for the determination of relative DOC concentrations of chromatographic peaks. Received: 21 February 1997 / Revised: 27 May 1997 / Accepted: 28 May 1997     

The use of ultrafiltration for the separation and fractionation of organic ligands in fresh waters

The effects of various experimental conditions on the results obtained by using membrane filtration for the separation and fractionation of organic matter in fresh waters (mainly fulvic and humic substances) are described. The technique used (washing or concentration) and the initial concentration of the organic matter to be filtered are the most critical factors. The technique is used for the fractionation of eight water samples, one sample of peat interstitial water, five water extracts of soil and four water samples obtained by decomposition of leaves. The results are compared. A comparison is also made with results cited in the literature.     

Radiation treatment of municipal effluent

The recycling of municipal wastewater is an effective means of coping with the water shortage in Tokyo. After irradiation, the refractory organic substances in wastewater were decomposed. COD, light brown color, offensive odor and foaminess in the effluents were reduced with increasing dose.

Inactivation efficiencies (D₁₀) of six microorganisms added to the secondary effluents and return sludge supernatant by irradiation were investigated. The survival curves of total bacteria, total coliforms and enterococci in the secondary effluents were compared. The number of total coliforms exponentially decreased with increasing dose and fell to undetectable levels at 0.5 kGy.

The elimination of suspended solids in the secondary effluents is effective in diminishing the dose required to disinfect and prevent bacteria regrowth.     

Physico-chemical changes taking place in gamma irradiated bovine globulins studied by thermal analysis

Structural transformations induced in gamma and alpha globulins under influence of gamma irradiation using doses of 2.5 and 24 kGy were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG, DTG). Thermal decomposition of the globulins irradiated in water suspensions occurs at higher temperatures, in comparison to the reference non-irradiated samples. This was related to formation of covalent linkages in the irradiated proteins, apart to chemical changes induced in amino-acids. Essential modification of thermal decomposition was detected already after irradiation with a dose of 2.5 kGy performed for water suspensions. Irradiation of solid native proteins induces decrease in decomposition temperature and gives evidence of proteins degradation.     

EFFECT OF CHRONIC UV EXPOSURE ON EPIDERMAL FORWARD SCATTERING-ABSORPTION INSK–1 HAIRLESS MOUSE SKIN

Abstract— Clinical and histological precancerous responses to UV irradiation are complicated dynamic functions of total dose, dose fractionation, fluence rate, and spectral distribution. This may be due, in large part, to the ability of UV to decrease epidermal-stratum corneum transmission by stimulation of hyperplasia. This work provides quantitative measurement of dose- and wavelength-dependent optical changes inSK–1 hairless mouse epidermis-stratum corneum occurring under irradiation with “monochromatic” UV wavebands, at 280, 290, 300, 307, and 313 nm. Mice were irradiated 5 days per week with a filtered Xenon-Hg high-intensity grating monochromator, starting with 0.9 minimal erythemal dose (MED), followed by incremental increases in the radiation dose by 20% of the original dose every tenth irradiation day, for2–8 consecutive weeks. Subsequent irradiations (for longer experiments) were followed by 30% incremental increases after the 8th week every 10th irradiation day until cessation of radiation at the end of 14 weeks. Irradiated and control full-thickness epidermis/ stratum corneum were examined histologically and by forward-scattering absorption spectroscopy. Chronic irradiation of hairless mice resulted in significant hyperplasia which was optically manifested by a general increase in forward-scattering absorbance. At moderate local doses (7.2 MED), the absorbance increase per MED was approximately the same for all excitation wavelengths, whereas at large total doses (? 100 MED) the optical increase per delivered MED progressively decreased in the order 313> 307> 300? 290> 280 nm. The increase in skin thickening, expressed as observed increase in absorption at 320 nm, correlated well with histological and clinical data. We propose that optical changes induced by UV-induced thickening can account in large part, if not entirely, for dynamic changes in action spectra for (pre) cancerous processes under chronic irradiation conditions.     

Determinations of humic substances and other dissolved organic matter and their effects on the increase of COD in Lake Biwa.

Humic substances and other dissolved organic matter (DOM) in Lake Biwa and the surrounding rivers were investigated to elucidate their origins and behavior. An annual increase in chemical oxygen demand (COD) has been observed in the northern basin of Lake Biwa since 1985. The concentrations of dissolved organic carbon (DOC) in the northern and southern basins of Lake Biwa were 1.7-2.4 mgC/l and 1.9-2.6 mgC/l, respectively. The DOC concentrations tended to be high in summer and low in winter, and the seasonal changes in the concentrations of humic substances were small. The humic substances content of DOM was considered to be comparatively small because the ratio of the concentration of humic substances to DOC was in the range of 0.14-0.32. From the results of the fractionation of DOM in lake waters, it was estimated that hydrophobic acids, such as humic substances and hydrophilic acids, were about 25% and 45%, respectively. The main origin of hydrophobic acids in Lake Biwa may be humic substances from soils around the rivers that flow into Lake Biwa, while hydrophilic acids may be due to the inner production by phytoplankton. Therefore, the increase of COD in the northern basin of Lake Biwa may be attributed to the contributions of not only humic substances but also hydrophilic acids.     

Pristine simple oxides as visible light driven photocatalysts: highly efficient decomposition of organic compounds over platinum-loaded tungsten oxide

Tungsten oxide loaded with nanoparticulate platinum is demonstrated to exhibit high activity for the decomposition of organic compounds both in liquid and gas phases; the activity was almost comparable to that of TiO2 under UV light irradiation and much higher than that of nitrogen-doped TiO2 under visible irradiation.     

Relative importance of hydrolyzed Al(III) species (Al(a), Al(b), and Al(c)) during coagulation with polyaluminum chloride: a case study with the typical micro-polluted source waters

The relative importance of three different Al species, Al(a) (monomeric species, instantaneous reacted species), Al(b) (medium polymer species, reacted less than 120 min), and Al(c) (colloidal or solid species, no reaction), defined by timed complexation reaction rate measured by using ferron reagent in polyaluminum chloride (PACl) was investigated in terms of DOC (dissolved organic carbon), UV(254), and turbidity removal efficiencies. Micro-polluted, typical North China, source waters were used to conduct the experiments. The results show that DOC removal is correlated well to the content of Al(b). Removal of UV(254) is determined by the content of Al(b) and Al(c), particularly Al(c). Turbidity removal is primarily related to the content of Al(c); however, Al(b) could destabilize particles efficiently, and the flocs formed by Al(b) are not as large as those formed by Al(c), which affected the settling efficiency. Unlike the preformed Al(b), the in situ formed Al(b) could remove turbidity more efficiently since Al(c) is the dominant final species formed during coagulation. Al(a) shows a strong ability to react with some unsatisfied coordinate bonds of organic matter to facilitate particle and DOC removal. The distinct coagulation feature of Al(a), Al(b), and Al(c) can be applied to develop tailor-made PACl (with the correct distribution of Al species) to match the characteristics of raw water for optimized coagulation.     

EFFECTS OF CHRONIC EXPOSURE ULTRAVIOLET-A INCLUDING 2% ULTRAVIOLET-B ON FREE RADICAL REDUCTION SYSTEMS IN HAIRLESS MICE

Chronic ultraviolet (UV) irradiation is known to cause a variety of changes in the skin, including wrinkles, pigmented spots and carcinogenesis. To explore time dependent changes in several parameters with chronic UV irradiation, we examined the molecular changes in connective tissue, intracellular defence enzymes and free radical antioxidant substances in hairless mice skin caused by chronic exposure to UV-A including 2% UV-B. Connective tissue changes were estimated using hydroxyproline and isodesmosine assays as a measure of collagen and elastin concentrations, respectively. After 6 weeks irradiation, the insoluble collagen and elastin were both substantially elevated, as were the activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). Continued UV irradiation resulted in a steady decline in SOD and lipid soluble antioxidants, while the GSH-Px remained elevated, suggesting that SOD and lipid soluble antioxidants in the skin may be involved in protecting it from UV damage and deteriorate with chronic irradiation.