Characteristics of compounds with strong or weak nitrification inhibition in sewage.

To clarify the characteristics of compounds with strong or weak nitrification inhibition in sewage, 64 organic compounds including compounds registered in Pollutant Release and Transfer Register (PRTR) were evaluated in terms of their chemical structures and molecular weights. Nineteen compounds showed strong nitrification inhibition by testing with Nitrosomonas europaea. Compounds with thioamide structures had the lowest median value of EC50 (0.017 mg/L), followed by those with alkyne structures (0.121 mg/L), chlorophenol structures (0.300 mg/L), and then azole structures (0.365 mg/L). In contrast, 33 of the 64 compounds showed weak nitrification inhibition at a concentration of 10 mg/L, 27 of which were categorized into three main groups: long-chain alcohol structures, alkyne structures with a phenyl group, and aromatic structures. Most compounds with strong nitrification inhibition had a low molecular weight (MW) from 50 to 200. Meanwhile, the proportion of compounds with weak nitrification inhibition tended to be greater with increasing MW and such compounds were predominant at higher molecular weights above 300. The correlations of results derived from tests of nitrification inhibition based on ISO 9509 and N. europaea showed that 24 out of 30 compounds provided results that were highly correlated between these tests (R = 0.85), while 4 compounds with chlorophenol structures and 2 compounds with alkyne structures showed weaker inhibition rates in the ISO 9509 test than in the N. europaea test. Our results indicate that the magnitude of nitrification inhibition depends on MW in addition to the chemical structure, which is helpful in the search for the cause of nitrification inhibition in wastewater treatment plants.

Temperature affects growth, geosmin/2-methylisoborneol production, and gene expression in two cyanobacterial species.

Cyanobacterial blooms accompanied by taste and odor (T&O) compounds affect the recreational function and safe use of drinking water. Geosmin and 2-methylisoborneol (2-MIB) are the most common T&O compounds. In this study, we investigated the effect of temperature on geosmin and 2-MIB production in Dolichospermum smithii and Pseudanabaena foetida var. intermedia. More specifically, transcription of one geosmin synthase gene (geoA) and two 2-MIB synthase genes (mtf and mtc) was explored. Of the three temperatures (15, 25, and 35 °C) tested, the maximum Chl-a content was determined at 25 °C in both D. smithii and P. foetida var. intermedia. The maximum total geosmin concentration (19.82 µg/L) produced by D. smithii was detected at 25 °C. The total 2-MIB concentration (82.5 µg/L) produced by P. foetida var. intermedia was the highest at 35 °C. Besides, the lowest Chl-a content and minimum geosmin/2-MIB concentration were observed at 15 °C. There was a good positive correlation between geosmin/2-MIB concentration and Chl-a content. The expression levels of the geoA, mtf, and mtc genes at 15 °C were significantly higher than those at 25 and 35 °C. The transcription of the mtf and mtc genes in P. foetida var. intermedia was higher at 35 °C than at 25 °C. The results highlight unfavorable temperature can increase the potential of geosmin/2-MIB synthesis from the gene expression level in cyanobacteria. This study could provide basic knowledge of geosmin/2-MIB production by cyanobacteria for better understanding and management of T&O problems in drinking water.

Effects of elevated nitrogen on the growth and geosmin productivity of Dolichospermum smithii.

Geosmin is one of the most common earthy-musty odor compounds, which is mainly produced by cyanobacteria in surface water. Nitrogen (N) is an important factor affecting the growth of cyanobacteria and its secondary metabolites production due to the eutrophication. In this study, we compared the effects of elevated N on the growth and geosmin productivity of Dolichospermum smithii NIES-824 (synonym Anabaena smithii NIES-824), aiming to better understand the mechanisms involved and give an important and fundamental knowledge to solve off-flavor problem. Results show that elevated N concentration promoted more chlorophyll a (Chl-a) production, whereas the geosmin synthesis decreased, revealing a possible competitive correlation between the Chl-a concentration and geosmin production of D. smithii NIES-824. The majority of geosmin (> 90%) was retained intracellularly during the 28 days of cultivation. The qRT-PCR analysis demonstrates that the expression level of the geosmin synthase gene (geoA) was constitutive and decreased at the higher N concentration during the exponential growth phase of cyanobacterial cells. Furthermore, the decrease of geoA expression during the decline phase suggested that geoA transcription was closely related to cell activity and isoprenoid productivity.

Exploration of an odorous aldehydes and ketones produced by Uroglena americana using high resolution mass spectrometry, GC-Olfactometry, and multivariate analysis.

Off-flavor events in tap water have been reported from various regions of Japan. Fishy smell is the second most common off-flavor in Japan and Uroglena americana (U. americana) is known to be a major contributor to the smell. However, the causative compound of the smell it produces still remains unrevealed to the best of our knowledge. In this study, an exploration of odorous aldehydes and ketones originating from U. americana was performed with a view to discovering a possible candidate substance of causative compounds. Environmental samples containing U. americana colony and cultured media with U. americana were analyzed with two high resolution mass spectrometers, one of them is coupled with liquid chromatography (LC-HRMS), and the other is with gas chromatography and a sniffing port (GC-O-HRMS). Multivariate analyses (MVA) were utilized to explore a compound that is likely to be odorous aldehydes or ketones with a reduced time of exploration. A combination of LC-HRMS and MVA resulted in the selection of one candidate substance and its formula was determined to be C13H20O3 on the basis of its accurate mass and natural isotopic pattern. The candidate substance underwent GC-O-HRMS analyses and milk-like smell was detected at around its retention time. Although the detected smell was different from fishy smell, it is expected that the fishy smell is caused by multiple compounds to which the candidate substance belongs. First generation product ion spectra of the candidate substance suggested that it contains a hydroxyl group, a cyclohexene ring, and a ketone moiety.

Identification of a mutagenic chlorination by-product produced from (E)-1, 3-dichloropropene (a component of nematocide DD) by using high resolution LC/MS and multivariate analysis.

The estimated domestic usage of DD (a typical nematocide) has been the greatest among all the agricultural chemicals in Japan. DD is involved in a document which is used to establish tap water quality standard in Japan. The document indicates that DD is potentially detectable in raw water for tap waters. DD in raw water will be treated with chlorine at waterworks, which raises concerns about formation of mutagenic chlorination by-products through the treatment. The objective of this work was to identify a mutagenic chlorination by-product by using high resolution mass spectrometers and multivariate analyses. Mutagenicity of the chlorination by-product was evaluated with the Ames Salmonella mutagenicity assay. (E)-1,3-Dichloropropene (DCP) was used as a model compound of DD. The mutagenicity of chlorine treated model aqueous solutions of DD increased with increasing chlorine dosages up to 3.00 mol-Cl2/mol-DCP. From the chlorine treated aqueous solutions of DD, 1,3-dichloroacetone (DCA) was identified as a major mutagen by a cochromatography with an authentic standard, precursor ion analyses and first-generation product ion analyses with the high resolution mass spectrometers. The mutagenicity of DCA against TA100 strain without microsomal activation was 160,000 net revertant colony/µmol (the toxicity equivalent factor was 0.14). Based on the mutagenicity of the chlorine treated DCP sample, the specific mutagenicity of DCA, and the DCA concentration in the sample, the mutagenic contribution of DCA to the chlorine treated DCP sample was calculated. High contribution (98%) clearly shows that DCA is a major mutagen in the chlorine treated DCP sample. Because the exploration of DCA was performed by using the unrealistic high concentration samples of DCP and chlorine, formation of DCA in the practical concentration samples (0-200 µg-DCP/L, 0.10 or 1.27 mg-Cl2/L) was examined. It was proven that DCA formation reaction takes place in the practical concentrations of DCA and chlorine.

Removals of pesticides and pesticide transformation products during drinking water treatment processes and their impact on mutagen formation potential after chlorination.

Removal efficiencies of 28 pesticide transformation products (TPs) and 15 parent pesticides during steps in drinking water treatment (coagulation-sedimentation, activated carbon adsorption, and ozonation) were estimated via laboratory-scale batch experiments, and the mechanisms underlying the removal at each step were elucidated via regression analyses. The removal via powdered activated carbon (PAC) treatment was correlated positively with the log Kow at pH 7. The adjusted coefficient of determination (r2) increased when the energy level of the highest occupied molecular orbital (HOMO) was added as an explanatory variable, the suggestion being that adsorption onto PAC particles was largely governed by hydrophobic interactions. The residual error could be partly explained by π-π electron donor-acceptor interactions between the graphene surface of the PAC particles and the adsorbates. The removal via ozonation correlated positively with the energy level of the HOMO, probably because compounds with relatively high energy level HOMOs could more easily transfer an electron to the lowest unoccupied molecular orbital of ozone. Overall, the TPs tended to be more difficult to remove via PAC adsorption and ozonation than their parent pesticides. However, the TPs that were difficult to remove via PAC adsorption did not induce strong mutagenicity after chlorination, and the TPs that were associated with strong mutagenicity after chlorination could be removed via PAC adsorption. Therefore, PAC adsorption is hypothesized to be an effective method of treating drinking water to reduce the possibility of post-chlorination mutagenicity associated with both TPs and their parent pesticides.

Identification of mutagenic transformation products generated during oxidation of 3-methyl-4-nitrophenol solutions by orbitrap tandem mass spectrometry and quantitative structure-activity relationship analyses.

We used Ames assays to investigate the effects of ozonation (designated O3), ozonation followed by chlorination (O3/Cl), an advanced oxidation process (AOP, UV/H2O2), and AOP followed by chlorination (AOP/Cl) on the mutagenicity of solutions of 3-methyl-4-nitrophenol (3M4NP), a major environmental degradation product of the organophosphorus insecticide fenitrothion. Whereas O3 did not induce mutagenicity, O3/Cl, AOP, and AOP/Cl converted 3M4NP into mutagenic transformation products (TPs). Using liquid chromatography-mass spectrometry, we detected a total of 138 peaks in the solutions subjected to O3/Cl, AOP, and AOP/Cl. To elucidate the TPs responsible for the observed mutagenicity, we performed simple regression analyses of the relationship between the area of each peak and the observed mutagenicity of samples withdrawn periodically during each oxidation process. The area of each of 10 peaks was found to be positively correlated (r2 ≥ 0.8) with the observed mutagenicity, suggesting that the TPs corresponding to these peaks contributed to the mutagenicity. After taking into account the consistency of mutagenicity induction by the oxidation processes and analyzing the peaks by tandem mass spectrometry, we identified 3 TPs, corresponding to 6 peaks, as candidate mutagens. These TPs were assessed by means of 4 quantitative structure-activity relationship (QSAR) models, and all 3 were predicted to be mutagenic by at least one model. This result was consistent with our assumption that these TPs were mutagens. Ames assays of an authentic sample of one of the 3 TPs revealed that it did not contribute to the mutagenicity. This left 3-methoxy-4-nitrophenol and 2-[(E)-[(2,5-dihydroxyphenyl) methylidene]amino]-5-dihydroxybenzaldehyde on the list of mutagens suspected of contributing to the mutagenicity induced by AOP. No TPs were identified as candidate mutagens responsible for the mutagenicity induced by O3/Cl and AOP/Cl.

Production of biodiesel fuel from canola oil with dimethyl carbonate using an active sodium methoxide catalyst prepared by crystallization.

In this study, a novel method for the production of biodiesel under mild conditions using fine particles of sodium methoxide formed in dimethyl carbonate (DMC) is proposed. Biodiesel is generally produced from vegetable oils by the transesterification of triglycerides with methanol. However, this reaction produces glycerol as a byproduct, and raw materials are not effectively utilized. Transesterification with DMC has recently been studied because glycerol is not formed in the process. Although solid-state sodium methoxide has been reported to be inactive for this reaction, the catalytic activity dramatically increased with the preparation of fine catalyst powders by crystallization. The transesterification of canola oil with DMC was studied using this catalyst for the preparation of biodiesel. A conversion greater than 96% was obtained at 65°C for 2h with a 3:1M ratio of DMC and oil and 2.0 wt% catalyst.

A level change in mutagenicity of Japanese tap water over the past 12 yr.

A relative comparison study of mutagenicity in Japanese tap water was conducted for 1993 and 2005 surveys. It intended to assess the effects of advanced water treatment installations to water works, improvement of raw water quality and improvement of residual HOCl concentration controlling. Sampling points (taps) were the same in both surveys. The results of 245 samples obtained by the Ames Salmonella mutagenicity test (Ames test) were analyzed. The Ames tests were conducted by using Salmonella typhimurium TA98 and TA100 strains with and without exogenous activation (S9). With the exception of TA100-S9, the other conditions needed no discussion as a factor in the mutagenicity level change. The average mutagenicity in 1993 and 2005 under the conditions of TA100-S9 were 2600 and 1100 net revertantL(-1), respectively. This indicated that the mutagenicity level of Japanese tap water decreased during the 12-yr period. Particularly a remarkable decrease in mutagenicity was observed in the water works where the advanced water treatments were installed during the 12-yr period. The advanced water treatments were effective in decreasing the mutagenicity of tap water. Mutagenicity also decreased in the water works with conventional water treatments; the improvement of residual HOCl concentration controlling was also considered to be effective in decreasing the mutagenicity of tap water.

Determination of total arsenic in coal and wood using oxygen flask combustion method followed by hydride generation atomic absorption spectrometry.

A simple and sensitive procedure for the determination of total arsenic in coal and wood was conducted by use of oxygen flask combustion (OFC) followed by hydride generation atomic absorption spectrometry (HGAAS). The effect of various items (composition of absorbent, standing time between the combustion and filtration, particle size and mass of sample) was investigated. Under the optimized conditions of the OFC method, nine certified reference materials were analyzed, and the values of arsenic concentration obtained by this method were in good accordance with the certified values. The limit of detection (LOD) and relative standard deviation (RSD) of the method were 0.29 microg g(-1) and less than 8%, respectively. In addition, eight kinds of coals and four chromated copper arsenate (CCA)-treated wood wastes were analyzed by the present method, and the data were compared to those from the microwave-acid digestion (MW-AD) method. The determination of arsenic in solid samples was discussed in terms of applicable scope and concentration range of arsenic.

Surveying the mutagenicity of tap water to elicit the effects of purification processes on Japanese tap water.

The mutagenicity levels of tap water in Japan were surveyed using the Ames test. Tap water samples (179) were collected at 17 sampling sites located from the northern tip (Hokkaido) to the southern tip (Kagoshima Prefecture). The mutagenicity values ranged from under the detection limit to 3600 net rev x L(-1). The average mutagenicity was 1100 net rev x L(-1) and the levels were significantly higher in the wintertime than in the summertime. The average mutagenicity of each site ranged from under the detection limit to 2000 net rev x L(-1). There was no significant correlation of the mutagenicity with TOC, A(260) or THMs. The highest positive ratios of the Ames test and the umu test were 92% under the condition TA100-S9 and 9% under the condition NM2009-S9, respectively, which indicated that the Ames test has higher sensitivity for the test of tap water than the umu test. This survey incorporated the 1992-1993 survey. The comparison of these survey-results in a further study will reveal the improvement of Japanese tap water quality from the perspective of mutagenicity.

Arsenic speciation in marine product samples: comparison of extraction-HPLC method and digestion-cryogenic trap method.

For the arsenic speciation in marine product samples, two types of pretreatment-analysis combination were compared. One is the combination of solvent extraction and high performance liquid chromatography (HPLC) followed by a highly sensitive arsenic detection, while the other is the combination of alkaline digestion and cryogenic trap (CT) method followed by a highly sensitive arsenic detection. For six certified reference materials (CRMs) of marine animal samples, the concentrations of arsenobetaine (AsB) obtained from the extraction-HPLC method were very consistent with those of trimethylated arsenic species measured by the digestion-CT method. For four seaweed samples, the determination of three arsenosugars (Sugar-1, Sugar-2, and Sugar-3) was favorably carried out by the extraction-HPLC method. Those seaweed samples were also subjected to the digestion-CT method, and the amounts of dimethylated arsenic species measured by the method were approximately equal to the sum of the amounts of dimethylarsinic acid (DMAA) and three arsenosugars (Sugar-1+Sugar-2+Sugar-3) obtained from the extraction-HPLC method.

Determination of mercury in ash and soil samples by oxygen flask combustion method--cold vapor atomic fluorescence spectrometry (CVAFS).

A simple method was developed for the determination of mercury (Hg) in coal fly ash (CFA), waste incineration ash (WIA), and soil by use of oxygen flask combustion (OFC) followed by cold vapor atomic fluorescence spectrometry (CVAFS). A KMnO4 solution was used as an absorbent in the OFC method, and the sample containing a combustion agent and an ash or soil sample was combusted by the OFC method. By use of Hg-free graphite as the combustion agent, the determination of Hg in ash and soil was successfully carried out; the Hg-free graphite was prepared by use of a mild pyrolysis procedure at 500 degrees C. For six certified reference materials (three CFA samples and three soil samples), the values of Hg obtained by this method were in good agreement with the certified or reference values. In addition, real samples including nine CFAs collected from some coal-fired power plants, five WIAs collected from waste incineration plants, and two soils were analyzed by the present method, and the data were compared to those from microwave-acid digestion (MW-AD) method.

Determination of trace elements in coal and coal fly ash by joint-use of ICP-AES and atomic absorption spectrometry.

Microwave-acid digestion (MW-AD) followed by inductively coupled plasma-atomic emission spectrometry (ICP-AES), graphite furnace atomic absorption spectrometry (GFAAS), and hydride generation atomic absorption spectrometry (HGAAS) were examined for the determination of various elements in coal and coal fly ash (CFA). Eight certified reference materials (four coal samples and four CFA samples) were tested. The 10 elements (As, Be, Cd, Co, Cr, Mn, Ni, Pb, Sb, and Se), which are described in the Clean Air Act Amendments (CAAA), were especially considered. For coal, the HF-free MW-AD followed by ICP-AES was successful in the determination of various elements except for As, Be, Cd, Sb, and Se. These elements (except for Sb) were well-determined by use of GFAAS (Be and Cd) and HGAAS (As and Se). For CFA, the addition of HF in the digestion acid mixture was needed for the determination of elements, except for As, Sb, and Se, for which the HF-free MW-AD was applicable. The use of GFAAS (Be and Cd) or HGAAS (Sb and Se) resulted in the successful determination of the elements for which ICP-AES did not work well. The protocol for the determination of the 10 elements in coal and CFA by MW-AD followed by the joint-use of ICP-AES, GFAAS, and HGAAS was established.

Combined use of photocatalyst and adsorbent for the removal of inorganic arsenic(III) and organoarsenic compounds from aqueous media.

A novel method for the removal of inorganic arsenic(III) (As(III)), monomethylarsonate (MMA), and dimethylarsinate (DMA) from aqueous media, was proposed and investigated. This method involves the combined use of TiO2-photocatalyst and an adsorbent, which has a high ability of As(V) adsorption, under photo-irradiation. When an aqueous solution of As(III) was stirred and irradiated by sunlight or xenon lamp in the presence of TiO2 suspension, the oxidation of As(III) into As(V) was effectively attained. By use of the same photocatalytic reaction, MMA and DMA were also degraded into As(V), while the total organic carbon (TOC) in the aqueous phase was decreased. When an aqueous solution of As(III) was stirred with a mixed suspension of TiO2 and an adsorbent for As(V) (activated alumina) under sunlight irradiation, the arsenic removal reached 89% after 24 h. By use of the same photocatalyst-adsorbent system, 98% of MMA and 97% of DMA were removed. The mechanism of the removal of arsenic species by the photocatalyst-adsorbent system was discussed.

Analysis of arsenic and some other elements in coal fly ash by X-ray photoelectron spectroscopy.

Surface characterization of coal fly ash (CFA) was carried out by use of X-ray photoelectron spectroscopy (XPS), especially focusing on the occurrence of As. A peak in the XPS spectrum of CFA was assigned to oxide forms of As(3d). The molar ratios of Al, As, Ca, Fe, and S normalized to Si were obtained from XPS analysis (MR-X). Also, the molar ratios of those elements were calculated from bulk analysis (total element concentration in CFA) (MR-B). The MR-X/MR-B ratio of As was much higher than those of other elements, suggesting that As is highly enriched on the surface of CFA. When eight CFA samples were analyzed, there was an approximate relationship between the MR-X values and MR-B values for As. The leaching of elements from CFA was examined by XPS analysis and by bulk analysis. The leaching tests using EDTA and HNO3 resulted in a great decrease in the As(3d) peak area; the %leaching of As obtained by XPS analysis was almost equal to that by bulk analysis.

Effect of HF addition on the microwave-assisted acid-digestion for the determination of metals in coal by inductively coupled plasma-atomic emission spectrometry.

The microwave-assisted acid-digestion for the determination of metals in coal by ICP-AES was investigated, especially focusing on the necessity of adding HF. By testing five certified reference materials, BCR-180, BCR-040, NIST-1632b, NIST-1632c, and SARM-20, it was found that the two-stage digestion without HF (HNO(3)+H(2)O(2) was used) was very effective for the pretreatment of ICP-AES measurement. Both major metals (Al, Ca, Fe, and Mg) and minor or trace metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) in coal gave good recoveries for their certified or reference values. The possibility of 'HF-memory effect' was cancelled by the use of a set of vessels which had been never contacted with HF. Twenty-four Japanese standard coals (SS coals) were analyzed by the present method, and the concentrations of major metals measured by the present method provided very high accordance with those from the authentic JIS (Japanese Industrial Standard) method.