食品废弃物厌氧消化产乙酸的研究

通过实验,研究了pH、总固体浓度(TS)、碳氮比(C/N)对食品废弃物厌氧消化产乙酸的影响,详细考察了挥发性脂肪酸(VFA)的组成和浓度及乙酸浓度随时间的变化规律.结果表明,pH为6.5、TS为7%(质量分数)、C/N为16:1时,总VFA的最大质量浓度为31.56 g/L,乙酸的最大质量浓度为19.46 g/L.     

Biosynthesis of polyhydroxyalkanoate by Gamma proteobacterium WD-3 from volatile fatty acids

The production of copolymers of poly-β-hydroxyalkanoates (PHA) is generally a high cost process. To reduce the production costs, inexpensive carbon sources such as volatile fatty acids (VFAs) from acidified wastewater can be used. Therefore, isolation of bacterial strains that can produce PHA copolymers using VFAs as a sole carbon source would be a beneficial alternative. In this study, a strain of PHA accumulating bacterium was isolated from the wastewater treatment plant of a soybean processing facility in Harbin. The strain was identified as γ-proteobacterium according to its 16S rDNA information and was originally named as strain WD-3. The strain accumulated a mass of PHA up to 45% of its dry cell weight when it was cultured under the optimum fermentation condition in this study when butyrate was used as the carbon source. In addition, WD-3 could synthesize PHA copolymers of poly-hydroxybutyrate and poly-hydroxyvalerate (PHV) either from C-even substrates or from C-odd substrates, and one-third of the copolymer was PHV. Results from this study demonstrated that small molecule organic acids can be used by the strain of WD-3 as the carbon source for growth and PHA production. The maximum PHA yield in the study was 0.45 g g⁻¹ dry cell.     

The diffusion and sorption of volatile organic compounds through kaolinitic clayey soils

Laboratory experiments to estimate the effective molecular diffusion coefficient (D(e)) and sorption coefficient (K(d)) for volatile organic compounds through natural clayey soils were conducted using diffusion testing apparatus. The compounds tested were methyl ethyl ketone (MEK), toluene and trichloroethylene (TCE). The D(e) and K(d) values were determined by a curve fitting procedure. The compound losses, and the effects of porous disks used in the apparatus were significant. The transport of MEK was faster than that of TCE and toluene because of the lower sorption to the soils. The D(e) values of all the compounds were of the order of 10(-10) m(2)/s and smaller than the diffusion coefficient in pure aqueous solution at infinite dilution (D(0)), due to the tortuosity of the samples. The effects of the sample thickness on the parameter determination were not significant. Comparison to the K(d) values estimated from batch sorption tests and from organic carbon content (f(oc))-based predictions showed that the diffusion test results were intermediate between those from the other two methods. The diffusion tests use compacted soil samples and should be more relevant to in situ conditions, but the reliability of the tests is affected by large compound losses that cause uncertainties in their interpretation. It is recommended that more than one method be used to assess K(d) values.     

温度对木质纤维素水解与挥发性脂肪酸累积的影响

木质纤维素厌氧消化过程产生的挥发性脂肪酸（VFAs）可作为外加碳源投加到人工湿地,解决人工湿地反硝化碳源不足的问题,但温度对木质纤维素厌氧消化生产VFAs过程的影响还有待深入探明。考察上述木质纤维素厌氧消化过程中有机碳源、糖与VFAs的变化规律,试图探明温度（10-55℃）对木质纤维素水解与VFAs累积的影响。研究结果表明,温度升高对木质纤维素的水解具有促进作用,对VFAs产量的影响显著。35℃时是生物质发酵产酸的最优条件,VFAs累积量不仅最早（第10天）达到最高值154mgCOD／g生物质,而且碳源的数量和品质均达到较高的水平。     

The use of naturally generated volatile fatty acids for herbicide removal via denitrification

This research focuses on the removal of 2, 4-D via denitrification, with a particular emphasis on the effect of adding naturally generated volatile fatty acids (VFAs) as a carbon source. These VFAs had been produced from an acid-phase anaerobic digester (mean VFA concentration of 3153 ± 801 mg/L [as acetic acid]). The first step involved developing 2, 4-D degrading bacteria in a sequencing batch reactor (SBR) fed with both sewage and 2, 4-D (30–100 mg/L). Subsequent denitrification batch tests demonstrated that the specific denitrification rate increased from 0.0119 ± 0.0039 to 0.0192 ± 0.0079 g NO₃-N/g volatile suspended solids (VSS) per day, when using 2, 4-D alone versus 2, 4-D plus natural VFAs from the digester as a carbon source. Similarly, the specific 2, 4-D consumption rate increased from 0.0016 ± 0.0009 to 0.0055 ± 0.0021 g 2,4-D/g VSS per day, when using 2, 4-D alone as compared to using 2, 4-D plus natural VFAs. Finally, a parallel increase in the percent 2, 4-D removal was observed, rising from 28.33 ± 11.88 using 2, 4-D alone to 54.17 ± 21.89 using 2, 4-D plus natural VFAs.     

Natural formation and degradation of chloroacetic acids and volatile organochlorines in forest soil--challenges to understanding

- DOI: http:/dx.doi.org/10.1065/espr2005.06.262 Goal, Scope and Background The anthropogenic environmental emissions of chloroacetic acids and volatile organochlorines have been under scrutiny in recent years because the two compound groups are suspected to contribute to forest dieback and stratospheric ozone destruction, respectively. The two organochlorine groups are linked because the atmospheric photochemical oxidation of some volatile organochlorine compounds is one source of phytotoxic chloroacetic acids in the environment. Moreover, both groups are produced in higher amounts by natural chlorination of organic matter, e.g. by soil microorganisms, marine macroalgae and salt lake bacteria, and show similar metabolism pathways. Elucidating the origin and fate of these organohalogens is necessary to implement actions to counteract environmental problems caused by these compounds. Main Features While the anthropogenic sources of chloroacetic acids and volatile organochlorines are relatively well-known and within human control, knowledge of relevant natural processes is scarce and fragmented. This article reviews current knowledge on natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soils, with particular emphasis on processes in the rhizosphere, and discusses future studies necessary to understand the role of forest soils in the formation and degradation of these compounds. Results and Discussion Reviewing the present knowledge of the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil has revealed gaps in knowledge regarding the actual mechanisms behind these processes. In particular, there remains insufficient quantification of reliable budgets and rates of formation and degradation of chloroacetic acids and volatile organochlorines in forest soil (both biotic and abiotic processes) to evaluate the strength of forest ecosystems regarding the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale. Conclusion It is concluded that the overall role of forest soil as a source and/or sink for chloroacetic acids and volatile organochlorines is still unclear; the available laboratory and field data reveal only bits of the puzzle. Detailed knowledge of the natural degradation and formation processes in forest soil is important to evaluate the strength of forest ecosystems for the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale. Recommendation and Perspective As the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil can be influenced by human activities, evaluation of the extent of this influence will help to identify what future actions are needed to reduce human influences and thus prevent further damage to the environment and to human health caused by these compounds.     

Anaerobic degradation of nonylphenol in soil

This study investigated the effects of various factors on the anaerobic degradation of nonylphenol (NP) in soil. The results show that the optimal pH for NP degradation was 7.0 and that the degradation rate was enhanced when the temperature was increased. The addition of compost enhanced NP degradation. The individual addition of the electron donors lactate, acetate, and pyruvate inhibited NP degradation. The high-to-low order of NP degradation rates under three anaerobic conditions was sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The results show that sulfate-reducing bacteria, methanogen, and eubacteria are involved in the anaerobic degradation of NP, with sulfate-reducing bacteria being a major component of the soil. Of the anaerobic strains isolated from the soil samples, strain AT3 expressed the best ability to biodegrade NP.     

毒死蜱在不同土壤腐殖酸上的吸附/解吸特征

通过平衡振荡法研究毒死蜱在不同来源土壤腐殖酸(Has)上的吸附/解吸行为.结果表明,毒死蜱在Has上的等温吸附行为用Freundlich模型描述相对更合理;它们的吸附等温线在实验范围内基本呈直线,且吸附能力很强,顺序为:紫色潮土Has＞黄壤Has＞中性紫色土Has＞酸性紫色土Has＞腐殖土Has;但毒死蜱的解吸率较小,其值均小于26.70%,有明显的滞后现象,尤其是腐殖土Has和紫色潮土Has,固定能力顺序为:紫色潮土Has＞腐殖土Has＞中性紫色土Has＞酸性紫色土Has＞黄壤Has.由于不同来源土壤中Has的组成结构差异明显,它们对毒死蜱的吸附/解吸规律表现出不同的特征.土壤Has对毒死蜱的吸附/解吸行为的影响是多种因素综合作用的结果,具体作用机理尚待进一步研究.     

Evidence of degradation of polybrominated biphenyls in soil samples from michigan

Abstract

Soil samples obtained from the former polybrominated biphenyls (PBB) manufacturing site in Michigan were analyzed by gas chromatography and gas chromatography with mass spectrometric detection. The results indicate significant degradation of the PBB residue in the soil sample. The soil sample with the highest concentration of PBB has the greatest degree of degradation. Principal degradation products include 2,3’,4,4’,5‐pentabromo‐biphenyl, 2,2’,4,4’,5‐pencabromobiphenyl and two unidentified tetrabromobiphenyls.

The degradation pattern observed supports a photochemical decomposition mechanism. These degraded residues may be more toxic than the original Firemaster residues. The implications of the results are discussed.     

壬基酚及其短链聚氧乙烯醚在污泥和土壤中的存在和降解

壬基酚聚氧乙烯醚(NPnEO)是广泛使用的表面活性剂．在污水处理厂中会降解为具有内分泌干扰效应的短链产物和最终产物壬基酚(NP)。剩余污泥是其进入环境的重要途径。介绍了NP和短链NPnEO在污泥中的存在情况、污泥处理过程对其存在的影响、以及这些物质随污泥处置过程进入土壤后的降解。     

Essential versus potentially toxic dietary substances: a seasonal comparison of essential fatty acids and methyl mercury concentrations in the planktonic food web

We investigated seasonal variability of essential fatty acids (EFA) and methyl mercury (MeHg) concentrations in four size categories of planktonic organisms in two coastal lakes. MeHg concentrations increased significantly with increasing plankton size and were independent of plankton taxonomy. However, total EFA increased from seston to mesozooplankton, but decreased in the cladoceran-dominated macrozooplankton size-class. Analysis of EFA patterns revealed that linoleic, alpha-linolenic, arachidonic, and eicosapentaenoic acids increased with increasing zooplankton size, but docosahexaenoic acid (DHA) in the cladoceran-dominated macrozooplankton was generally lower than in seston. This consistent pattern demonstrates that cladocerans, although bioaccumulating MeHg, convey less DHA than similar-sized copepods to their consumers. It is thus evident that fish consuming cladocerans have restricted access to DHA, yet unrestricted dietary access to MeHg. Thus, the structure of planktonic food webs clearly affects the composition of EFA and regulates dietary supply of these essential nutrients, while MeHg bioaccumulates with increasing zooplankton size.     

Ecotoxicological assessment of doxycycline in soil

Doxycycline has been used in continually increasing quantities for mass treatment of food animals because of its greater bioavailability relative to older tetracyclines. The study presented in this paper was undertaken to investigate the degradation rate of the tetracycline derivative in manure-amended soil. In the present experiment, following composting, the doxycycline-contaminated manure was applied to agricultural land, and a field study was performed to investigate the degradation rate of doxycycline in soil. By the end of the 20-week sampling period, about 20 %, 33 % and 18 % of the initial doxycycline concentrations could be measured in soil samples taken at three different soil depths. The calculated half-life of doxycycline in the soil was 66.5, 76.3 and 59.4 days at depths of 0 cm, 25 cm and 50 cm, respectively. The potential effect of doxycycline on soil microbial activity was demonstrated by the nitrogen transformation test performed in compliance with the Organisation for Economic Co-operation and Development (OECD) Guideline No. 216. On day 28, the following nitrate concentrations of the control soil sample were found in the soil samples treated with different amounts of doxycycline: 76.9 %, 53.0 %, 65.6 %, 59.7 % and 77.1 %.     

Carbofuran degradation in soil profiles

Abstract

Two soils, Puyallup fine sandy loam from Puyallup, WA, and Ellzey fine sand from Hastings, FL, each with a prior history of carbofiiran exposure but with different pedological and climatological characteristics, were found to exhibit enhanced degradation toward carbofiiran in surface and subsurface soil layers. The treated Puyallup and Ellzey soils exhibited higher mineralization rates for both the carbonyl and the aromatic ring of carbofiiran when compared to untreated soils. Disappearance rates of [¹⁴C‐URL (uniformly ring labeled)] carbofiiran in the treated Ellzey soil was faster than in untreated soil, and also faster in surface soil than in subsurface soil. Initial degradation patterns in the treated Ellzey soil were also different from those in the untreated soil. The treated Ellzey soil degraded carbofuran mainly through biological hydrolysis, while untreated soil degraded carbofuran through both oxidative and hydrolytic processes.     

Parathion degradation and its intermediate formation by Fenton process in neutral environment

The purpose of this study is to investigate parathion degradation by Fenton process in neutral environment. The initial parathion concentration for all the degradation experiments was 20 ppm. For hydrogen ion effect on Fenton degradation, the pH varied from 2 to 8 at the [H₂O₂] to [Fe²⁺] ratio of 2-2 mM, and the result showed pH 3 as the most effective environment for parathion degradation by Fenton process. Apparent degradation was also observed at pH 7. The subsequent analysis for parathion degradation was conducted at pH 7 because most environmental parathion exists in the neutral environment. Comparing the parathion degradation results at various Fenton dosages revealed that at Fe²⁺ concentrations of 0.5, 1.0 and 1.5 mM, the Fenton reagent ratio ([H₂O₂]/[Fe²⁺]) for best-removing performance were found as 4, 3, and 2, resulting in the removal efficiencies of 19%, 48% and 36%, respectively. Further increase in Fe²⁺ concentration did not cause any increase of the optimum Fenton reagent ratio for the best parathion removal. The result from LC-MS also indicated that hydroxyl radicals might attack the PS double bond, the single bonds connecting nitro-group, nitrophenol, or the single bond within ethyl groups of parathion molecules forming paraoxons, nitrophenols, nitrate/nitrite, thiophosphates, and other smaller molecules. Lastly, the parathion degradation by Fenton process at the presence of humic acids was investigated, and the results showed that the presence of 10 mg L⁻¹ of humic acids in the aqueous solution enhanced the parathion removal by Fenton process twice as much as that without the presence of humic acids.     

环境胁迫因子对固定菌修复污染土壤效果的研究

通过对环境胁迫因子参数的不同设定,对固定菌修复污染土壤效果进行了研究.结果显示,当环境胁迫因子温度(高温40 ℃和低温15 ℃)、酸碱度(pH＝4和pH＝9)及重金属(Cd和Pb)存在时,对固定菌降解污染物的影响并不大,而游离菌降解率却有一定的下降趋势.进一步观察了固定化载体内部微观结构,为固定菌用于有机污染土壤的异位修复提供了一定的理论基础.     

Fatty acids composition of Caenorhabditis elegans using accurate mass GCMS-QTOF

The free living nematode Caenorhabditis elegans is a proven model organism for lipid metabolism research. Total lipids of C. elegans were extracted using chloroform and methanol in 2:1 ratio (v/v). Fatty acids composition of the extracted total lipids was converted to their corresponding fatty acids methyl esters (FAMEs) and analyzed by gas chromatography/accurate mass quadrupole time of flight mass spectrometry using both electron ionization and chemical ionization techniques. Twenty-eight fatty acids consisting of 12 to 22 carbon atoms were identified, 65% of them were unsaturated. Fatty acids containing 12 to17 carbons were mostly saturated with stearic acid (18:0) as the major constituent. Several branched-chain fatty acids were identified. Methyl-14-methylhexadecanoate (iso- 17:0) was the major identified branched fatty acid. This is the first report to detect the intact molecular parent ions of the identified fatty acids in C. elegans using chemical ionization compared to electron ionization which produced fragmentations of the FAMEs.     

Effect of design parameters in horizontal flow constructed wetland on the behaviour of volatile fatty acids and volatile alkylsulfides

A pilot-scale horizontal flow constructed wetland (HFCW) system planted with common reed (Phragmites sp.) was constructed to study how hydraulic loading rate (HLR), aspect ratio, water depth, and granular medium affect to the fate of several organic matter degradation intermediates namely, acetic acid (HAc), isovaleric acid (Isoval), and dimethylsulfide (DMS). ANOVA statistical analysis performed on the data set of 8 months of operation shows that the HLR and the water depth are two major factors that control the performance of HFCWs for the target analytes. A clear difference in the HFCW effluent concentrations was obtained according to water depth. Effluents of the shallow water depth contained lower DMS (1.05-1.44 microg l-1), HAc (7.91-10.9 mg l-1), and Isoval (0.11-0.15 mg l-1) concentrations than the deeper beds (DMS: 1.68-2.40 microg l-1; HAc: 9.29-14.4 mg l-1, and Isoval: 0.20-0.31 mg l-1). Such differences could be accounted to the different formation and consumption rates of the organic matter degradation intermediates, which is related with the redox potentials (E). Indeed, it could lead to different biochemical reactions of organic matter degradation according with the E value. HLR has a statistically significant influence on the effluent HAc, Isoval, and DMS concentrations. Seasonal variability of effluent HAc concentration shows that it is independent on the HAc loading. While the loading showed no seasonal pattern, the removal efficiency was clearly higher in cold months, which suggests a predominant internal production of HAc in HFCWs in the warm season from the accumulated organic particulate matter. Similar results were also found when Isoval and DMS were considered.     

Reducing ammonia emissions and volatile fatty acids in poultry litter with liquid aluminum chloride

This study was a pen trial in which the effects of adding different rates of liquid aluminum chloride (AlCl₃) on litter pH, total volatile fatty acids (VFAs), and ammonia (NH₃) fluxes was evaluated. Liquid AlCl₃ treatments used in this study were sprayed on the rice hull surface at rates of 100 g, 200 g, and 300 g liquid AlCl₃/kg rice hulls; untreated rice hulls served as controls. Litter pH, total VFAs, and NH₃ fluxes were all lowered (P< 0.05) by all of the liquid AlCl₃ treatments compared with controls during certain times of the 5 week study. However, there were no significant differences among treatments on litter pH at the end of the study (from 3 to 5 weeks) or NH₃ fluxes at beginning of the study (0 to 3 weeks). Total VFAs were reduced 16 %, 29 %, and 53 % by 100 g liquid AlCl₃/kg rice hulls, 200 g liquid AlCl₃/kg rice hulls, and 300 g liquid AlCl₃/kg rice hulls, respectively. Liquid AlCl₃additions reduced NH₃ fluxes by 35 %, 57 % and 67 %, respectively, at the low, medium and high rates. In summary, these results indicate that adding liquid aluminum chloride to rice hulls would be a useful tool in reducing the negative environmental impact of poultry litter. It should be noted that the decreased VFA production and NH₃ volatilization was chiefly associated with reduction in litter pH.     

Microbial degradation of the benzonitrile herbicides dichlobenil, bromoxynil and ioxynil in soil and subsurface environments--insights into degradation pathways, persistent metabolites and involved degrader organisms

The benzonitriles dichlobenil, bromoxynil and ioxynil are important broad-spectrum or selective herbicides used in agriculture, orchards and public areas worldwide. The dichlobenil metabolite 2,6-dichlorobenzamide is the most frequently encountered groundwater contaminant in Denmark, which suggests that the environmental fate of these three structurally related benzonitrile herbicides should be addressed in detail. This review summarises the current knowledge on microbial degradation of dichlobenil, bromoxynil and ioxynil with particular focus on common features of degradation rates and pathways, accumulation of persistent metabolites and diversity of the involved degrader organisms.     

Persistence,degradation and leaching of coumaphos in soil

Abstract

Dissipation, degradation and leaching of fresh ¹⁴C coumaphos, alkylated ¹⁴C coumaphos and aged residues of ¹⁴C coumaphos from vats were studied in alkaline sandy loam soil in soil columns in the field under subtropical conditions in Delhi for a year. Dissipation, degradation and bound residue formation was more in case of alkali treated coumaphos than fresh coumaphos. After 365 days total residues of fresh coumaphos accounted for 33.25% while that of alkali treated coumaphos was 19.12%. Bound residue formation was almost double in case of alkali treated coumaphos (18.95%) than fresh coumaphos (9.53%) after 150 days followed by release of bound residue in both the cases. The proportion of metabolites 4 ‐ methylumbelliferone, chlorferon and potasan collectively was 86.05% in fresh coumaphos extractable residues while the same was 91.74% in alkali treated coumaphos after 365 days. Aged residues from vats containing copper sulphate and buffer were found to be more persistent in soil as total residues remained were 95.58% in comparison with 83.09% total residues of aged residues from vats containing only buffer after 150 days of treatment. Copper sulphate seems to inhibit the degradatiion of coumaphos in soil by microorganisms. Chlorferon was the major metabolite in generally all the samples. Coumaphos did not leach below 10 cm in all the cases.