Effects of extracellular polymeric substances on aerobic granulation in sequencing batch reactors

The effects of extracellular polymeric substances on aerobic granulation in sequencing batch reactors were investigated by evaluating the content and compositions of extracellular polymeric substances, and the relationship between extracellular polymeric substances composition and surface properties of glucose-fed aerobic granules. The results showed that extracellular polymeric substances could affect surface properties of cells, such as surface charge and hydrophobicity, enhance polymeric interaction and promote aerobic granulation. Moreover, extracellular polymeric substances were produced mainly in the exponential phase, and served as carbon and energy source in starvation phase during granulation process, thus regulating the growth of bacteria in the interior and exterior of granules, and maintaining the integrality of granules.     

Effects of humic substances on the decomposition of 2,4-dichlorophenol by ozone after extraction from water into acetic acid through activated carbon

The objectives of this study are to clarify the behavior of humic substances throughout the processes of 2,4-dichlorophenol (2,4-DCP) adsorption on granular activated carbon (GAC) from water and extraction into acetic acid, and the influence of the extracted humic substances on the decomposition of 2,4-DCP by ozone in the acetic acid. The adsorption capacity of GAC for 2,4-DCP was not influenced by the humic substances preloaded to have equilibrium concentration of 24.9mg Cl(-1) (14.5mg Cg(-1)). The adsorption capacity of GAC for 2,4-DCP decreased to one tenth of new GAC after the first adsorption-extraction step because of only 16% desorption in the first step. However, 2,4-DCP adsorbed on GAC was completely extracted after the second step suggesting that GAC can be used as adsorbent to transfer 2,4-DCP from water to acetic acid. The concentration ratio of 2,4-DCP from water into acetic acid was around 2x10(5), whereas the concentration ratio of humic substances was about 3.5, indicating that 2,4-DCP was selectively adsorbed and extracted by this system. The first order degradation rate constant for 2,4-DCP by ozone in acetic acid increased with the addition of humic substances. The rate constant with 16mg Cl(-1) of humic substances was 2.6 times as high as that without humic substances. Humic substances behaved as a promoter for the degradation of 2,4-DCP by ozone.     

Selectivity in the complexation of actinides by humic substances

The interactions of a range of actinide elements (Th, U, Np, Pu, Am) with humic substances from the Needle's Eye natural analogue site were studied by gel permeation chromatography. Bulk humic substances were isolated by ammonia extraction, followed by dialysis against distilled water and freeze-drying. The gel permeation results suggest that Needle's Eye humic substances can be fractionated into three incompletely resolved fractions with average molecular weights determined by analytical ultracentrifugation around 49 000 for Fraction 1, around 14 700 for Fraction 2 and around 8000 for Fraction 3. Although there are significant differences between the organic matter elution patterns in individual gel permeation experiments, presumably due to differences in column packing, these are much smaller than the differences between metal ions. The uranium that is naturally present in these humic substances is largely bound in the late-eluting fraction. Spikes of the early actinides, including Np and Pu in controlled valency states, have been added to the humic substances, and gel permeation of the spiked humic substances shows that the three humic fractions vary greatly in their effectiveness and selectivity as ligands for early actinides.     

活性污泥中温与高温絮凝特性

为了揭示中温与高温活性污泥的絮凝特性及其作用机制,本研究采用序批式反应器,分别在35℃及55℃条件下培养了中温与高温活性污泥,考查了2种活性污泥的相互作用能与胞外聚合物的特性。研究结果表明：高温污泥系统出水浊度为（145±22．9）NTU,是中温污泥系统的近50倍。中温污泥的相互作用能曲线存在明显的势垒（313．4×10^-20J）,而高温污泥不存在明显势垒;高温污泥的松散型胞外聚合物与紧致型胞外聚合物的含量分别为中温污泥的12倍及3．5倍,且胞外聚合物中蛋白质、多糖、腐殖酸和DNA的含量均高于中温污泥的含量。这表明,尽管高温污泥相互作用能势垒低,但其胞外聚合物,尤其是松散型胞外聚合物含量过高,是高温污泥絮凝性能低的内在机制,而胞外聚合物组成特征不是中温和高温污泥絮凝性能差异的主要原因。     

水单胞菌CA滤液的溶藻特性及其溶藻物质

针对一株具有明显溶藻效果的水单胞菌CA（Aquimonas sp.）,对其滤液的溶藻活性以及溶藻物质特性做了进一步的探索。结果表明,CA滤液具有强烈的溶藻效果。10 d内叶绿素a降解率达79.2%,藻细胞数目降解率达98.5%。同时,藻蓝蛋白和别藻蓝蛋白急剧降低,分别降低了81.67%和82.60%。丙二醛含量也有所降低。通过研究溶藻物质的活性,发现溶藻物质经蛋白酶K处理后仍具有溶藻活性,说明溶藻物质是非蛋白类物质;溶藻物质具有较强的热稳定性,即使在121℃下处理2 h活性仍未丧失;溶藻物质在碱性条件下有较强的pH稳定性,在酸性条件下活性会有小部分丧失;同时通过有机试剂萃取,发现溶藻物质具有较强的极性。本研究为溶藻物质的溶藻特性研究以及溶藻物质的分离提供了理论基础。     

Comparison of photochemical behavior of various humic substances in water: I. Sunlight induced reactions of aquatic pollutants photosensitized by humic substances

Humic substances are shown to photosensitize transformations of several types of synthethic chemicals that do not photoreact when exposed to sunlight in distilled water. In most cases, photoproducts were the same in colored natural waters and in solutions of soil-derived humic substances, including those obtained commercially. Kinetic studies in sunlight indicated that the efficiencies of the reactions photosensitized by humic substances of various origins were the same within a factor of 2.     

A comparative study of tea waste derived humic-like substances with lignite-derived humic substances on chemical composition,spectroscopic properties and biological activity

Environmental Science and Pollution Research - Emerging demand for humic substances escalated the short supply of coal-related resources from which humic substances are extracted in large...     

Reactions of compost-derived humic substances with lead, copper, cadmium, and zinc

Thermodynamic stability constants of the formation of complexes from the reactions of humic substances with various metals are usually used as parameters to judge the reactivities of both humic substances and metals. However, in calculating the thermodynamic stability constants, complicated processes for the acquisition of activities of components in reactions are absolutely inevitable. In this study, we investigated the average conditional concentration quotients of the complexes formed from the reaction of metals with humic substances and the relations of these quotients to thermodynamic stability constants. The characterized humic substances including HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) extracted from a swine compost were prepared to react with Pb, Cu, Cd, and Zn at 25 degrees C and at pH 4.00 and 6.50. Reactions of HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) with the four metals were carried out at 1:0.1, 1:0.5, 1:1, 1:5, and 1:10 ligand:metal stoichiometry. The concentrations of the free ions of Pb, Cu, Cd, and Zn in the reaction systems of metal-HA suspensions and metal-FA solutions were measured by anodic stripping voltammetry (ASV). The sequence of the average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals was FA(MW<1,000)>FA(MW>1,000)>HA(MW>1,000), showing the relative reactivities of the fractions of swine compost-derived humic substances. The sequence of reacting metals with humic substances was Pb>Cu>Cd>Zn, which is in good agreement with the sequence reported by judging the thermodynamic stability constants. The average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals were thus useful parameters that can be directly related to thermodynamic stability constants and other parameters.     

Photocatalytic oxidation of toxic organohalides with TiO2/UV: the effects of humic substances and organic mixtures

TiO2/UV photocatalytic oxidation of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), 1,2,3-trichlorobenzene and 4-chlorophenol were examined in aqueous solution in the presence of humic substances and organic mixtures to study if the degradation rates were affected. Both commercial and natural humic substances were observed to retard the photodegradation rates, with a greater effect from the natural humic substances. Acetonitrile and isopropanol also caused significant retardation of 4-chlorophenol photodegradation. The overall retardation can be attributed to the combination of light attenuation, inhibition and competition effects. Moreover, the TiO2/UV system favors the decomposition of compounds that have stronger adsorption onto the TiO2 surface. To engineer effective treatment facilities that use the TiO2/UV system for the treatment of toxic substances in wastewater, the methodology must allow for concerns about adventitious species which are present.     

The lanthanum precipitation method. Part 1: a new method for technetium(IV) speciation in humic rich natural groundwater

A new and quick method for direct speciation of Tc(IV) in humic rich solutions, based on the induced aggregation of humic substances in the presence of the trivalent cation La(3+), is presented. This method (the "La-precipitation method") allows flocculating all the humic substances and also the Tc(IV) associated with humic substances. The method is tested on solutions containing Tc(IV) and Gorleben humic substances. The influence of different parameters (humic substance concentration, Tc concentration, reaction time and pH) is investigated on the observed free Tc(IV) concentration after precipitation of all humic substances. None of these parameters had a (significant) influence on the observed Tc(IV) concentration in solution after addition of La(3+) to Tc(IV)-HS containing solutions. It is therefore proposed that the method can be used to separate the Tc(IV) bound to humic substances from the free inorganic Tc species in solution.     

A Bayesian approach to probabilistic ecological risk assessment: risk comparison of nine toxic substances in Tokyo surface waters

Background, aim, and scope  

Quantitative risk comparison of toxic substances is necessary to decide which substances should be prioritized to achieve effective risk management. This study compared the ecological risk among nine major toxic substances (ammonia, bisphenol-A, chloroform, copper, hexavalent chromium, lead, manganese, nickel, and zinc) in Tokyo surface waters by adopting an integrated risk analysis procedure using Bayesian statistics.     

Metal homeostasis in Hypogymnia physodes is controlled by lichen substances

The hypothesis was tested that the lichen substances produced by the epiphytic lichen Hypogymnia physodes control the intracellular uptake of divalent transition metals. Incubating lichen thalli with and without their natural content of lichen substances with metal solutions showed that the lichen substances of H. physodes selectively inhibit the uptake of Cu(2+) and Mn(2+), but not of Fe(2+) and Zn(2+). Such behavior is ecologically beneficial, as ambient concentrations of Cu(2+) and Mn(2+) in precipitation and bark are known to limit the abundance of H. physodes, whereas limiting effects of Fe(2+) or Zn(2+) have never been found. This suggests that increasing the Cu(2+) and Mn(2+) tolerance stimulated the evolution of lichen substances in H. physodes. The depsidone physodalic acid is apparently most effective at reducing Cu(2+) and Mn(2+) uptake among the seven lichen substances produced by H. physodes. Probably lichen substances play a general role in the metal homeostasis of lichens.     

Determining the role of human substances in the fate of pesticides in the environment

The data presented in this paper emphasize that the behavior and fate of pesticides in the environment is influenced by humic substances. Various methods most frequently used for the characterization of humic substances are discussed. Both humic acid and fulvic acid can solubilize in water certain organic compounds and are important carriers of some pesticides in soil. Humic substances have the potential for promoting the nonbiological degradation of many pesticides. Several methods of bleaching humus color from drinking water, including chlorination, ozonation, and UV-radiation, are described. Finally, the photochemical stability to UV-radiation of certain pesticides in aqueous fulvic acid solution is discussed.     

Characterizing the heavy metal-complexing potential of fluorescent water-extractable organic matter from composted municipal solid wastes using fluorescence excitation–emission matrix spectra coupled with parallel factor analysis

To investigate the effect of organic matter evolution on heavy metal sorption, fluorescence excitation–emission matrix (EEM) spectra combined with parallel factor (PARAFAC) analysis were employed to characterize the evolution and metal-complexing potential of fluorescent water-extractable organic matter (WEOM) from composted municipal solid wastes (MSWs). The WEOMs examined comprised humic-, fulvic-, tryptophan-, and tyrosine-like substances. Composting treatment increased the content of humic- and fulvic-like matter, and changed the existence pattern of tryptophan- and tyrosine-like substances (i.e., the tryptophan- and tyrosine-like substances from uncomposted MSWs were mainly bound in protein-like matter, whereas those from composted MSWs were primarily bound in humic- and fulvic-like substances). Furthermore, composting treatment increased the polar functional group, aromaticity, and humification degree of the WEOMs, but decreased the aliphatic and hydroxyl group. These evolutions decreased the Cu(II) affinities of fulvic- and humic-like substances and the Pb(II) affinities and complexing capacities of fulvic-like substances, but increased the Cu(II) complexing capacities of fulvic- and humic-like substances. These results reveal that mature composts from the MSWs can be used for the remediation of Cu- and Pb-contaminated soils in situ, whereas immature composts can enhance the metal transferability from soil to plant.     

Determining the role of humic substances in the fate of pesticides in the environment

Abstract

The data presented in this paper emphasize that the behavior and fate of pesticides in the environment is influenced by humic substances. Various methods most frequently used for the characterization of humic substances are discussed. Both humic acid and fulvic acid can solubilize in water certain organic compounds and are important carriers of some pesticides in soil. Humic substances have the potential for promoting the nonbiological degradation of many pesticides. Several methods of bleaching humus color from drinking water, including chlorination, ozonation, and UV‐radiation, are described. Finally, the photochemical stability to UV‐radiation of certain pesticides in aqueous fulvic acid solution is discussed.     

A new twist on an old regression: transfer of chemicals to beef and milk in human and ecological risk assessment

Exposure of humans to chemicals in beef or milk is part of almost all risk evaluation procedures carried out to reduce emissions or to remediate sites. Concentrations of substances in these livestock products are often estimated using log-log regressions that relate the biotransfer factor BTF to the octanol-water partition ratio K(ow). However, the correctness of these empirical correlations has been questioned. Here, we compare them to the mechanistic model OMEGA that describes the distribution of substances in organisms by integrating theory on chemical fugacity and biological allometry. OMEGA has been calibrated and validated on thousands of laboratory and field data, reflecting many chemical substances and biological species. Overall fluxes of water, food, tissue (growth), milk and stable substances calculated by OMEGA are within a factor of two from independent data obtained in experiments. Rate constants measured for elimination of individual compounds of a recalcitrant nature vary around the level expected from the model for output to faeces and milk. Both data and model suggest that biotransfer BTF of stable substances to beef and milk is independent of the octanol-water partition ratio K(ow) in the range of 10(3)-10(6). This contradicts empirical regressions including stable and labile compounds. As expected, levels of labile substances vary widely around a tentative indication derived from the model. Transformation and accumulation of labile substances remains highly specific for the chemical and organism concerned but depends weakly on the octanol-water partition ratio K(ow). Several possibilities for additional refinement are identified.     

Identification of substances with potential for long-range transport as possible substances of very high concern

According to the European legislation, REACH, organic compounds are considered as substances of very high concern (SVHC) if they are persistent, bioaccumulative and toxic (PBT). A substance's long-range transport potential (LRTP) may also pose a risk to remote regions. This is, however, not yet explicitly included. For identification of compounds, which are not PBT according to REACH criteria, but show LRTP, we investigated 22,438 compounds from the Canadian Domestic Substance List (CDSL). The CDSL was searched for organic, neutral compounds. Substance properties were estimated with EPI Suite v4.00. Next, the substance list was edited in two ways: (1) The half-life criterion in air for LRTP as defined in the Stockholm Convention was applied. (2) For all compounds, indicators for persistence and LRTP were calculated with the multimedia model ELPOS v2.2. Applying the half-life criterion, we identified 594 substances, which are prone to LRT but are not PBT (non-PBT-L substances). In contrast, investigations with ELPOS lead to a shorter list of 188 substances, which are non-PBT-L substances. Finally, the list was compared with potential Arctic contaminants identified in previous literature. Our results show that there is a large number of organic chemicals which would not be considered as SVHC since they are not, at the same time, persistent, bioaccumulative and toxic according to REACH criteria. Nevertheless, they show LRTP according to different screening approaches and thus a potential hazard to remote regions.     

Charge characteristics of humic and fulvic acids: comparative analysis by colloid titration and potentiometric titration with continuous pK-distribution function model

Charge characteristics of humic and fulvic acids of a different origin (inshore soils, peat, marine sediments, and soil (lysimetric) waters) were evaluated by means of two alternative methods - colloid titration and potentiometric titration. In order to elucidate possible limitations of the colloid titration as an express method of analysis of low content of humic substances we monitored changes in acid-base properties and charge densities of humic substances with soil depth, fractionation, and origin. We have shown that both factors - strength of acidic groups and molecular weight distribution in humic and fulvic acids - can affect the reliability of colloid titration. Due to deviations from 1:1 stoichiometry in interactions of humic substances with polymeric cationic titrant, the colloid titration can underestimate total acidity (charge density) of humic substances with domination of weak acidic functional groups (pK>6) and high content of the fractions with molecular weight below 1kDa.     

The use of inert carriers in regulatory biodegradation tests of low density poorly water-soluble substances

Many poorly water-soluble compounds fail regulatory ready biodegradation tests as the method of test material preparation limits the bioavailability of the chemical. The recognised method for delivery of poorly soluble materials into biodegradability tests consists of coating test material inside the test vessel or onto inert substrates (i.e., glass cover slide, boiling beads, filter paper, or Teflon stir bar) that are placed inside the vessels. Volatile solvents are often used to augment this process. Although these substrates work fairly well for delivering many poorly soluble materials into biodegradability tests, they have not been effective in keeping low density, poorly water-soluble substances in the test medium. Soon after medium is added to the test vessels, these chemicals break loose from the substrates and float on the surface where they have limited contact with micro-organisms in the test medium. Hence, there is a reduced potential for measuring substantial biodegradability in the test. This paper describes the work undertaken to establish a standard method of adding low density, poorly water-soluble substances into test vessels of biodegradability studies to ensure these materials remain in contact with micro-organisms in the test medium. The substances are prepared for testing by adsorption onto silica gel followed by dispersion into the culture medium. This method of delivery may provide greater intra- and inter-laboratory consistency in biodegradability test results for low density, poorly water-soluble substances and it may more closely mimic the probable transport and fate of these substances in the environment.