Chlorination of ozonated soil fulvic acid: mutagenicity studies in Salmonella

Samples of soil fulvic acid (SFA) were ozonated and subsequently chlorinated under acidic or slightly basic conditions. The residues were tested for His+ reversion in a fluctuation assay, using Salmonella typhimurium TA100 as the tester strain. The ozonated/chlorinated samples were mutagenic, but activity was dependent on the amount of ozone utilized and the pH of the reaction medium. Although increases in cell concentrations were also induced by some mutagenic samples, this alone did not account for the mutagenicity observed. Unchlorinated samples displayed insignificant activity.     

Influence of humic substances on the ultraviolet disinfection of surface waters

The efficiency of ultraviolet (UV) disinfection and the regrowth potential of total coliforms were investigated in humic waters. Experiments were conducted according to an experimental design in which a UV radiation dose range of 68–681 mW s/cm² was applied to waters containing various concentrations (0–10 mg/L) of fulvic acid. Experimental results strongly suggested that the harmful effect of UV radiation on bacteria was diminished in humic waters due to absorption of UV light. Increasing concentrations of fulvic acid appeared to enhance its influence with elevated doses of UV radiation. Measured inactivation responses were on the order of 1–6 log₁₀ units for the UV dose range used. Comparison of k (inactivation coefficient) values for nonhumic water to highly humic water indicated that k decreased proportionally as the fulvic acid concentration of water was increased. The results of dark‐incubation tests indicated significant regrowth of bacteria in fulvic acid‐containing waters.     

Characterisation of dissolved organic matter in karst spring waters using intrinsic fluorescence: relationship with infiltration processes

From analysis of spectrophotometric properties of dissolved organic matter (OM) and the hydrochemical responses of some karst springs under different hydrologic conditions, an assessment of the origin and transfer pathway of OM present in karst spring waters, from soil and epikarst toward the spring, has been conducted for three karst aquifers in southern Spain: Alta Cadena, Sierra de Enmedio and Los Tajos. Intrinsic fluorescence (excitation-emission matrices or EEMs), together with major water chemistry (electrical conductivity, temperature, alkalinity, Cl⁻, Mg^+ 2) and P_CO2 along with natural hydrochemical tracers (TOC and NO₃⁻), have been monitored in 19 springs which drain the three karst aquifers examined in this study. The spring water EEM spectra indicate that fulvic acid-like substances, produced in the soil as a consequence of the decomposition of OM, are the dominant fluorophores, although some of the OM appears to originate from in situ microbiological activity but could be indicative of contamination present in recharge waters from livestock. During each recharge event, TOC and NO₃⁻ concentrations increased and variations in fluorescence intensities of peaks attributed to fulvic acid-like compounds were observed. In areas with minimal soil development, spatial and temporal variations in the fluorescence intensity of fulvic acid-like substances and other fluorophores derived from microbiological activity, together with other hydrochemical parameters, provide insights into the hydrogeological functioning of karst aquifers and the infiltration velocity of water from soil and facilitate assessment of contamination vulnerability in these aquifers.     

Residual oxidant decay and bromate formation in chlorinated and ozonated sea-water

Oxidant decay and bromate formation were studied under light and dark conditions in 5.15 and 30‰ artificial sea-water and 5‰ natural estuarine water following ozonation or chlorination. For both oxidants, light exposure accelerated the residual oxidant decay rates which were inversely related to sample salinities in artificial sea-water. Significant quantities of bromate were produced in light-exposed, chlorinated samples with an initial residual oxidant concentration of 70 μM (5mg l⁻¹ as total residual chlorine) but not at lower residual oxidant concentrations or in non-photolyzed samples. No bromate was formed in any of the chlorinated natural estuarine water samples. Bromate production was much greater in ozonated samples than in chlorinated ones and was formed in two distinct stages. Photolytic bromate formation decreased with increasing bromide concentration in both chlorinated and ozonated artificial sea-water. Bromate formation was completely inhibited in the presence of NH₃-N and estuarine sediment. The same free radical mechanism is proposed for both ozone-induced and photolytic-induced bromate formation in artificial sea-water.     

Physicochemical aspects of disinfection of water by means of ultrasound and ozone

20 kHz-ultrasonic waves intensify the ozonation process in regard to disinfection of microorganisms, as well as to oxidation of organics. Ultrasonic treatment of effluent from biological sewage plant, reduced the sterilization dose of ozone with 50%, and increased the half order rate constant of decoloration of Rhodamine B with 55%.The phenomena is attributed to the action of two physicochemical mechanisms. (1) Ultrasound decomposes ozone causing augmentation of the activity of free radicals. (2) Simultaneous ultrasonic treatment enhances the aeration constant, (K_Lα-value). Both mechanisms increase the gas liquid ozone transfer and the utilization of the applicated ozonated gas.It is verified that free radicals are the proper disinfective and oxidative agents in ozonation and sonozonation. Ozone molecules act as precursors and may in themselves be relatively nontoxic.     

The ozonation of organic halide precursors: effect of bicarbonate

A laboratory study of the effect of bicarbonate on the ozonation of organic halide precursors in fulvic acid solutions and in a raw drinking water was conducted. The experimental variables were bicarbonate concentration, ozone dose and pH of chlorination. Results are expressed in terms of trihalomethane (THM), total organic halide (TOX), trichloracetic acid, dichloroacetic acid, trichloroacetone and dichloroacetonitrile precursor concentrations. Kinetic studies showed that bicarbonate slowed the decomposition of ozone in the presence of fulvic acid, and thereby, led to a greater degree of destruction of u.v.-absorbing substances. Similarly, precursor destruction increased with increasing bicarbonate concentrations in the range of 10⁻⁴spd 10⁻² M. Precursor destruction was greatest when chlorination was performed at low pH. At high pH's of chlorination, some precursor enhancement was noted, especially in the absence of bicarbonate. Results are interpreted both from a mechanistic standpoint and with respect to their applicability to water treatment practice.     

Application of pyrolysis-gas chromatography-mass spectrometry to the characterization of humic substances resulting from decay of aquatic plants in sediments and waters

Pyrolysis-GC-MS, elemental analysis and i.r. spectroscopy reveal major differences between humic substances from aquatic plants (algae and aquatic phanerogams) and lagoonal, marine and lacustrine deposits. Algae are enriched in proteins and their pyrolysis yields numerous nitrogenous by-products (alkylpyrroles, nitriles and alkylpyridines) along with aromatic compounds which are thought to reflect the decomposition of individual amino-acids (styrene, toluene, phenol and p-cresol). These compounds are less abundant in the pyrolysis products of humic substances from phanerogams with increasing amounts of methoxyphenols, characteristics of lignins.In the deposits of the Kerguelen Islands and of a “blue lake” in Greenland, the importance of algal populations is emphasized by pyrolysis products corresponding to nitrogenous and carbohydrate derivatives. Phenols and cresols in the pyrochromatograms of these samples are interpreted as evidence of polypeptides rather that lignin: p-cresol is much more abundant than the other cresols, suggesting the formation of phenols by way of tyrosine.Lagoonal sediments, in contrast, seem typical of intermixed development of algae and phanerogams.Differences between fulvic and humic acids are emphasized by the development of polyphenols and protein derivatives in humic acids compared to polysaccharide derivatives in fulvic acids. Other constituents revealed by PY-GC-MS include N-acetyl aminosugars, phthalates and aliphatic compounds.     

Photocatalytic destruction of fulvic acids by oxygen in the TiO<Subscript>2</Subscript> suspension

The paper presents a short review of the published data dealing with the photocatalytic (O₂/TiO₂/UV) oxidation of humic and fulvic acids that represent main organic impurities of natural waters. The possibility of achieving a deep destruction (≥ 90% in terms of TOC) of fulvic acids separated from the water of the Dnieper River during the process of photocatalytic oxidation by oxygen was shown for a wide interval of pH (3–8). The photocatalytic activity of a series of commercial TiO₂ samples in different isomorphic states was estimated and the impact of certain parameters of photocatalytic oxidation on the degree of complete destruction of fulvic acids was determined.     

Toxication or detoxication? In vivo toxicity assessment of ozonation as advanced wastewater treatment with the rainbow trout

Ozonation as advanced wastewater treatment method is an effective technique for micropollutant removal. However, the application of this method carries the inherent danger to produce toxic oxidation byproducts. For an ecotoxicological assessment conventionally treated wastewater, wastewater after ozonation and ozonated wastewater after sand filtration were evaluated in parallel at an operating treatment plant via the fish early life stage toxicity test (FELST) using rainbow trout (Oncorhynchus mykiss).The FELST revealed a considerable developmental retardation of test organisms exposed to ozonated WW. This was accompanied by a significant decrease in body weight and length compared to reference water, to the conventionally treated WW and to the ozonated water after sand filtration. Hence sand filtration obviously prevents from adverse ecotoxicological effects of ozonation.An additional test with yolk-sac larvae resulted in a significant reduction of vitellogenin levels in fish exposed to ozonated wastewater compared to fish reared in conventionally treated wastewater. This demonstrates the effective removal of estrogenic activity by ozonation.Adverse ozonation effects may have been a result of the conversion of chemicals into more toxic metabolites. However, sand filtration reduced toxication effects indicating that these oxidation byproducts are readily degradable or adsorbable. The results indicate that in any case ozonation should not be applied without subsequent post treatment appropriate for oxidation byproducts removal (e.g. sand filtration).     

The use of hydrogen peroxide for raising the efficiency of filter operation with biologically activated carbon

We have investigated the impact of hydrogen peroxide on the efficiency of biofiltration of the solutions of fulvic acids through biologically activated carbon with a native biofilm. We have also determined optimal conditions for using hydrogen peroxide in the processes of filtration through carbon. The use of H₂O₂ at the concentration 5 mg/dm³ is the most expedient since it makes it possible to enrich a solution of natural organic matter, in particular, fulvic acids with oxygen. It has been demonstrated that oxygen released during catalytic decomposition of H₂O₂ is actively consumed by microorganisms in the filter medium.     

The isolation and characterization of fulvic acid and humic acid from river water

Many rivers in New Hampshire are rich in dark brown organic matter from natural sources. Because the interactions between metal ions like Fe³⁺ and the organic fulvic and humic acids makes water treatment difficult, we are studying the nature of the organic acids.

Fulvic acid was isolated from the B₂ horizon of a Podzol soil obtained at Conway, NH, and fulvic and humic acids were isolated from the Oyster River (Lee, NH) and Jewel Pond (Stratham, NH). The method of isolating the organic matter from water involves new techniques. The oxygen-containg functional groups, carbon, hydrogen, and nitrogen were analyzed for all samples. The fulvic acid and humic acid samples isolated from water are different from each other, but similar to analogous soil samples.     

Particle formation and growth in dilute aluminum(III) solutions : Characterization of particle size distributions at pH 5.5

Particle formation and growth over the 1–40 μm size range in dilute aluminum solutions (approx. 2 × 10⁻⁴ M) have been studied using an electronic particle counter. Sulfate, fulvate and hydroxide ion accelerate the rate of particle formation and changes of the particle size distribution over time. Increasing ionic strength (inert electrolyte) produces similar but less dramatic effects. Combinations of sulfate and fulvic acid or sulfate and inert electrolyte further accelerate the rate of particle formation. Aluminum chloride solutions at moderate ionic strength are devoid of supramicron particles after several days. A conceptual pathway model is developed which suggests that two different solids are formed when aluminum is added to fulvic acid solutions: an aluminum-fulvate precipitate and Al(OH)₂(s). The first solid dominates in fulvic acid solutions at pH 5.5.     

The study of properties and catalytic activity of titanium dioxide doped with sulphure

Comparison was made by activity of TiO₂ doped with sulphur (S-TiO₂) and pure TiO₂, synthesized by the sol-gel method, with TiO₂ Degussa P-25 in course of photocatalytic oxidation by oxygen of the air of aqueous solutions of fulvic acids, humic and picric acids at two modes of radiation by a SVD-120 lamp (λ > 200 or λ > 320 nm). It is shown that at oxidation of fulvic acids and humic acid the activity of S-TiO₂ is substantially higher than the activity of pure TiO₂ under both modes of radiation, however, under conditions of the experiment the given samples were less effective at oxidation by picric acid.     

Impact of hydrogen peroxide on the destruction degree of fulvic acids and organic impurities of river water by ozone,UV radiation,and O<Subscript>3</Subscript>/UV treatment

We have investigated the impact of hydrogen peroxide on the change of the generalized indicators of water quality of the Dnieper River and model solutions of fulvic acids in UV radiation, ozonization, and O₃/UV treatment. We confirmed its involvement in the oxidation process of organic impurities by all studied methods at the pH of the medium more than 7. However, the additions of 1–5 mg/dm³ of hydrogen peroxide inhibited the destruction of fulvic acid in a weakly acidic medium (pH 6.3) and reduced the mineralization degree of water impurities of the Dnieper River during O₃/UV treatment and do note accelerate discoloration of the samples under investigation at the studied parameters of ozonization and O₃/UV treatment.     

The role of organic matter content and humus quality in the maintenance of soil fertility and in environmental protection

The role of organic matter in soil fertility has been well known for hundreds of years, but the role of humus quality and its environmental functions has been discovered only during the last 30 years. We outlined in an earlier study our equivalent humus parameter for the characterization of humus content and humus quality, EH_G=H_{t ha-1}K, where H_{t ha-1} is the humus content in tonnes per hectare at a depth of 1 m and K is the humus quality parameter calculated from extinction ratios of 1% NaF and 0.5% NaOH soil humus extracts. K values vary greatly; soils with raw organic materials show values around 0.01, whereas soils with the best humus quality (chernozems) have values of about 10. In investigations in recent years, we started from our general database of about 4000 sampling sites and extended the research with particular humus quality investigations over many hundreds of soil profiles for equivalent humus values. Compared with their humus status expressed in our results in log EH_G values, podzols have the lowest values ( 1.50-1.70 ), brown forest soils are in the medium range ( 1.90-2.50 ) and chernozems have the highest values ( 3.00–3.20 ). The results represent 81.14% of the cultivated area of Hungary. As K values increase as a result of humification, which produces long-chain humic acids, and their C/N values decrease, we express at the same time the polyfunctionality of humic substances, by a general environmental protection capacity, EPC_G=D_xH²K, and a special environmental protection capacity, EPC_s=D_xH²R, where D_x is the thickness of the soil layer in centimeters, H is the humus percentage and R=K/(C/N). This system is suitable for evaluation of the humus status in landscape planning, in land use in the maintenance of soil fertility. Because of the important role of humus in binding toxic elements and xenobiotics, the results are of value for sustainable land use.     

Photocatalytic destruction of fulvic acids by ozone and oxygen

We have studied destruction of river fulvic acids in water environment with ozone and oxygen. We have also determined advantages of catalytic and photocatalytic ozonization of their solutions compared with ozonization and O₃/UV treatment. Photocatalytic ozonization secures the highest degree of destruction of fulvic acids (93% in terms of total organic carbon) at a shorter time and specific consumption of ozone compare with other methods of oxidation.     

Seasonal variation and impact factors of available phosphorus in typical paddy soils of Taihu Lake region,China

Phosphorus loss from soil can play an important role in eutrophication of aquatic bodies. The seasonal variation of available phosphorus in soil profiles of three major paddy soils (Bai soil, Huangni soil and Wushan soil) during wheat and rice growth seasons was studied in the Taihu Lake region of China. The results were as follows: the available phosphorus contents differed in the three paddy soils. Available phosphorus content in Bai soil was the lowest in these soils. The available phosphorus content decreases rapidly with depth from the soil surface and reach the minimum value at approximately 45 cm before increasing slightly near the groundwater. The contents of available phosphorus were higher in February (tillering and shooting period of wheat) and in September (full heading time of rice) than in other months. The total phosphorus content strongly affects available phosphorus content in the studied soils. During the period of wheat cultivation, they show a typical power function relationship with correlation coefficient r = 0.6492** (n = 13), a significant positive linear correlation. In addition, available phosphorus content has a remarkable positive linear correlation with organic matter content, r = 0.9111** (n = 13), and a remarkable negative linear correlation with pH value, r = ?0.5945* (n = 13). In Wushan soil, there is a negative linear correlation between clay content and available phosphorus content, r = ?0.9289* (n = 4). Therefore, total phosphorus content, organic matter content and pH value are major impact factors on available phosphorus content in these soils.     

Potential health risks of arsenic,antimony and mercury in the Takab geothermal field,NW Iran

This study investigates the bioavailability, water–soil to plant transfer and health risks of arsenic (As), antimony (Sb) and mercury (Hg) in the Takab geothermal field north-west of Iran. Water used for irrigation, surface soils from agricultural lands and cultivated plants were collected from three polluted sites and analysed for As, Sb and Hg to assess associated health risks. As content in irrigation water ranges from 23.4 to 986.4?μg/L, whereas total As content in the surface soil is in the range of 16.3–492?mg/kg^?1. The results agree with other reports that metal (loid) concentrations in leaves are usually much higher than in grain. Most investigated plant species showed a significant correlation between As, Sb and Hg contents in their aerial parts and that available in the soil (r?=?0.82, p?=?0.012; r?=?0.84, p?=?0.004; r?=?0.79, p?=?0.011). Factors influencing the bioavailability of metal (loids) and their occurrences in plants are soil pH, cation exchange capacity, phosphate, calcite and organic matter content, soil texture and interaction between target elements. Available As in analysed soils is relatively low, implying that phosphate, as well as Fe-oxy-hydroxides and calcite are effective in absorbing As. But, sequential extraction analysis indicates that iron oxy-hydroxide surface can bind both As and Sb, with As being more strongly bound. The calculated bioaccumulation factor based on total metal (loids) and available metal (loids) in soil indicates that alfalfa (Medicago sativa L.) and sage (Saliva syriaca L.) are effective accumulators of As, Sb and Hg. The health risk index of the studied plants ranged from 0.0003 to 5.71, with the maximum being in wheat (Triticun aestivum L.), an alarming sign for human health. It is suggested that health risks from long-term consumption of wheat and other As-rich foodstuffs must be managed by monitoring contamination in the water–soil–plant pathway.     

Residual crude oil concentrations and ecotoxicity of polluted tropical soils after phytoremediation

Changes in residual crude oil concentrations and soil ecotoxicity during the phytoremediation assessment of tropical plants growing on crude oil-polluted soils were evaluated in a greenhouse study. The plants (Panicum maximum, Zea mays, Centrosema spp. and Pueraria spp.) were grown in weathered polluted soil samples in microcosms for 10?weeks. Residual crude oil in soil was quantified colorimetrically, while the ecotoxicity of the vegetated and control soil samples were evaluated using earthworms’ percentage survival and crop seeds’ germination bioassays. It was observed that planting of 1% (w/w) polluted soil samples reduced crude oil in the rhizosphere soils of P. maximum and Centrosema spp. by 71.6?±?1.4 and 55.3?±?4.3%, respectively. These are in contrast with 37.5?±?2.5% reduction in non-vegetated control soil samples. The ecotoxicity assays indicated that planting also effected reduction of crude oils’ toxicity positively. There were 100, 40?±?28.3 and 50?±?21.1% survival of test earthworms, respectively, after 24?h in 1% w/w polluted soil samples phytoremediated with P. maximum, Centrosema spp. and Pueraria spp. as against 0% survival in non-vegetated control samples. The observed sensitivity of the test organisms to chemical stress bodes well for providing rapid information on effectiveness of remediation programmes.