美国威斯康星州的Lower Fox River和Lower Green Bay水域的污染沉积物对鱼类影响的研究

LowerFoxRiver和LowerGreenBy水域的沉积物造成了该地区的轻度污染。经测定和分析,沉积物中含有较高的PCBs和较低含量的PCDFs及PCDDs,在鱼样品中呈现有PCBs和农药。组织病理学检查,鱼体内寄生虫感染发生率较高,部分肝组织坏死,出现肉芽瘤状物,胰腺纤维化,但没有发现鱼体上有肿瘤。     

Sorption/Desorption of Polychlorinated Dibenzo-P-Dioxins and Polychlorinated Dibenzo Furans (PCDDs/PCDFs) in the Presence of Cyclodextrins

The goal of this study was to investigate the usefulness of cyclodextrins (CDs) for the removal of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo furans (PCDDs/PCDFs) in soil and water. Five CDs having different molecular cavities and active functional groups were selected and evaluated for their ability to include (trap) PCDDs/PCDFs in soil and water. For the soil experiments, CDs were added to the soil on day one and the concentrations of unbound PCDDs/PCDFs were monitored over a 28-day period. Parallel control experiments were conducted to assist in the process performance evaluation. The ability of CDs to remove PCDDs/PCDFs from the contaminated soil was dependent upon the type of CD used and constituents of PCDDs/PCDFs. Among the five CDs investigated, hydroxypropyl-β -cyclodextrin (HPBCD) gave the highest removal efficiency for all components of PCDDs/PCDFs. The removal efficiency of total PCDDs/PCDFs was 81% one day after application of CDs and then increased to 96% after 28 days. The α -cyclodextrin (ACD) and β -cyclodextrin (BCD) removed only 45% and 50% of the total PCDDs/PCDFs after 28 days, respectively, whereas hydroxypropyl-γ -cyclodextrin (HPGCD) removed 80% of the total PCDDs/PCDFs.     

Comparative kinetic study of the binding between 2,3,7,8-tetrachlorodibenzo-ρ-dioxin and related ligands with the hepatic Ah receptors from several rodent species

Kinetic analysis of the time course of association of [³H]-2,3,7,8-tetrachlorodibenzo-ρ-dioxin with hepatic cytosoi from five rodent species gave additional evidence for differences in the properties of the Ah receptor ligand binding subunit between species. A parallel study of the association of six tritiated polychlorinated dibenzopρ-dioxins and dibenzofurans with hepatic Ah receptor from Wistar rat and C57BL/6 mouse showed that their rank order for kinetic affinity did not correlate with the rank ordering of their toxic potency- and may vary according to the source of the Ah receptor.     

Preliminary characterization of four 2-chlorobenzoate-degrading anaerobic bacterial consortia

Dechlorination was the initial step of 2CB biodegradation in four 2-chlorobenzoate-degrading methanogenic consortia. Selected characteristics of ortho reductive dehalogenation were examined in consortia developed from the highest actively dechlorinating dilutions of the original 2CB consortia, designated consortia M34-9, P20-9, P21-9 and M50-7. In addition to 2-chlorobenzote, all four dilution consortia dehalogenated 4 of 32 additional halogenated aromatic substrates tested, including 2-bromobenzoate; 2,6-dichlorobenzoate; 2,4-dichlorobenzoate; and 2-chloro-5-hydroxybenzoate. Dehalogenation occurred exclusively at the ortho position. Both ortho chlorines were removed from 2,6-dichlorobenzoate. Benzoate was detected from 2-bromobenzoate and 2,6-dichlorobenzoate. 4-Chlorobenzoate and 3-hydroxybenzoate were formed from 2,4-dichlorobenzoate and 2-chloro-5-hydroxybenzoate, respectively. Only benzoate was further degraded. Slightly altering the structure of the parent 'benzoate molecule' resulted in observing reductive biotransformations other than dehalogenation. 2-Chlorobenzaldehyde was reduced to 2-chlorobenzyl alcohol by all four consortia. 2-chloroanisole was O-demethoxylated by three of the four consortia forming 2-chlorophenol. GC-MS analysis indicated reduction of the double bond in the propenoic side chain of 2-chlorocinnamate forming 2-chlorohydrocinnamate. None of the reduction products was dechlorinated. The following were not dehalogenated: 3- and 4-bromobenzoate; 3- and 4-chlorobenzoate; 2-, 3-, and 4-fluorobenzoate; 2-, 3-, and 4-iodobenzoate; 2-, 3-, and 4-chlorophenol; 2-chloroaniline; 2-chloro-5-methylbenzoate; 2,3-dichlorobenzoate; 2,5-dichlorobenzoate; 2,4,5-trichlorophenoxyacetic acid; and 2,4-dichlorophenoxyacetic acid. Consortia M34-9, P20-9, P21-9, and M50-7 dechlorinated 2-chlorobenzoate at 4 mm. Dechlorination rates were highest for consortia P20-9 followed by those of M50-7with rates declining above 2 and 3mm 2CB, respectively. The major physiological types of microorganisms in consortia M34-9, P20-9, P21-9, and M50-7 were sulfate-reducing and hydrogen-utilizing anaerobes.     

Combining photolysis and bioprocesses for mineralization of high molecular weight polyacrylamides

The influence of ultraviolet photolysis as a pretreatment to the aerobic and anaerobic biological mineralization of a ¹⁴C-polyacrylamide was assessed using a series of radiorespirometry bioassays. The polyacrylamide studied was non-ionic with molecular weights ranging between 100,000 and 1 million. Aerobic and anaerobic biomineralization of the unphotolysed (raw) polyacrylamide was found to be only 0.60% and 0.70%, respectively, after 6 weeks of incubation, and hence indicative of the natural recalcitrance of polyacrylamide to microbial degradation. The effectiveness of UV irradiation in the physical breakdown of the polyacrylamide chain into oligomers was demonstrated by the shift in the molecular weight distribution and the positive correlation between the time of irradiation and the degree of its biological mineralization. The molecular weight fraction below 3 kD, which represents only 2% of the raw polyacrylamide, was increased to 41, 60 and 80% after 12, 24 and 48 hours of photolysis, respectively. This in turn, yielded, after 6 weeks of incubation, an aerobic mineralization of 5, 17 and 29% of 150 mg/L polyacrylamide, respectively, and an anaerobic mineralization of 3, 5 and 17%, respectively. Biomass acclimation substantially improved the specific initial rate of biomineralization of the photolysed polyacrylamides, but not the overall percentage of polyacrylamides mineralized.     

垃圾渗滤液在土壤中的生物降解动态

通过室内好氧、厌氧2种培养,研究了3种不同填埋年限垃圾渗滤液在红壤和潮土中的生物降解动态.鲜样、天井洼样、水阁样垃圾渗滤液分别为填埋0年、4～5年和12年的垃圾渗滤液.结果表明,垃圾渗滤液在前7 d降解相对较快.在好氧培养条件下,红壤鲜样、天井洼样、水阁样渗滤液在前7 d的表观降解率为88.9%、60.5%、25.0%;潮土中的表观降解率更大,分别为96.6%、80.4%和65.0%;7 d后下降趋势均趋于平缓.在相同土壤中,填埋龄越短的垃圾渗滤液的表观降解率越大,在厌氧培养条件下的情况与此类似,但降解率不如好氧条件下高.在没有土壤介质参与的条件下(如低洼处积存的渗滤液),3种垃圾渗滤液自身降解速率均符合一级动力学方程.鲜样垃圾渗滤液降解的半衰期为12～16 d,其余垃圾渗滤液降解的半衰期为20～30 d.垃圾渗滤液一旦进入土壤环境,降解速率会大大加快.土壤处理垃圾渗滤液有一定的功效.     

Removal of phosphate in a sequencing batch reactor by Staphylococcus auricularis

A sequencing batch reactor (SBR) was used to remove phosphate in biological wastewater treatment as an alternative to the activated sludge process, in order to improve the low removal efficiency of phosphate and the operational instability. After a cycle of 2 h anaerobic and 4 h aerobic conditions, phosphate removal was optimized. The removal efficiencies of 5 and 50 mg phosphate l^–1 by Staphylococcus auricularis under repeated anaerobic and aerobic conditions were above 90%. These results showed that a long adaptation time, one of the major problems in biological phosphate removal process, was overcome by SBR.     

Dichloromethane utilized by an anaerobic mixed culture: acetogenesis and methanogenesis

Dichloromethane (8.9 mg/l) was eliminated from industrially polluted, anaerobic groundwater in a fixed-bed reactor (43 m³) which was packed with activated charcoal and operated continuously for over three years. The elimination of dichloromethane over this period was some ten-fold in excess of the sorptive capacity of the charcoal, and the elimination (3.7 mg/h·[kg of charcoal]: residence time, 49 h) was tentatively attributed to dehalogenative microorganisms immobilized on the charcoal. Anaerobic enrichment cultures, with dichloromethane as the sole added source of carbon and energy, were inoculated with material from the reactor. Reproducibly complete substrate disappearance in subcultures was observed when traces of groundwater (1%) or yeast extract (0.01%) were supplied. Fed-batch experiments under an atmosphere of CO₂ plus N₂ led to the conversion in 11 days of 11 mM dichloromethane to 3 mM acetate and 2 mM methane, with a growth yield of 0.4 g of protein/mol of dichloromethane; insignificant amounts (<1 M) of chloromethane accumulated. Methanogenesis could be inhibited by 50 mM 2-bromoethane sulfonate without any effect on the dehalogenation rate. The maximum dehalogenation rate was 0.13 mmol dichloromethane/h·l (2.6 mkat/kg of protein).Abbreviation DCM dichloromethane     

Comparison of anaerobic microbial communities from Estuarine sediments amended with halogenated compounds to enhance dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin

A suite of experiments were conducted to ascertain whether dehalogenation of a model dioxin compound could be stimulated in marine sediments by supplementation with halogenated analogues to enrich for dehalogenating bacteria and if growth by members of the Chloroflexi-like group was associated with dioxin removal. Five halogenated compounds (tetrachlorobenzene, tetrachloroanisole, tetrachlorophenol, tetrachlorobenzoic acid and trichloroacetophenone) were added with 1,2,3,4-tetrachlorodibenzo-p-dioxin (TeCDD) to estuarine sediments from four sites in San Diego Bay and the coast of southern New Jersey to test for dioxin dehalogenation. Most of the halogenated additives were found to stimulate dechlorination of the model dioxin. Molecular analysis of the bacterial population using 16S rRNA and reductive dehalogenase genes indicated that distinct microbial populations were enriched with each halogenated co-amendment. Additionally, Chloroflexi-like ribosomal genes associated with dehalogenation were detected. For example, quantitative real-time PCR analysis of 16S rRNA and reductive dehalogenase gene copy number in the microcosms showed a positive correlation with 1,2,3,4-TeCDD reductive dechlorination in coastal sediments amended with different halogenated additives. These results suggest that specific Chloroflexi-like microorganisms related to Dehalococcoides are involved in 1,2,3,4-TeCDD reductive dechlorination.     

Color removal of real textile wastewater by sequential anaerobic and aerobic reactors

Textile wastewater from the Pusan Dyeing Industrial Complex (PDIC) was treated utilizing a two-stage continuous system, composed of an upflow anaerobic sludge blanket reactor and an activated sludge reactor. The effects of color and organic loading rates were studied by varying the hydraulic retention time and influent glucose concentration. The maximum color load to satisfy the legal discharge limit of color intensity in Korea (400 ADMI, unit of the American Dye Manufacturers Institute) was estimated to be 2,700 ADMI·L⁻¹ day⁻¹. This study indicates that the two-stage anaerobic/aerobic reaction system is potentially useful in the treatment of textile wastewater.     

First Evidence for Homologous Recombination-mediated Large DNA Inversion on the Bacillus subtilis 168 Chromosome

A Bacillus subtilis 168 strain carrying an inversion of about 1600kb-long chromosomal DNA was isolated. Physical and genetic analyses demonstrated that the inversion was generated as a result of homologous recombination between two homologous sequences integrated at the met and leuB loci. This is the first clear evidence of a large stable chromosomal inversion induced by homologous recombination in B. subtilis.     

Anaerobic degradation and dehalogenation of chlorosalicylates and salicylate under four reducing conditions

The anaerobic biodegradability and transformationof the mono-and dichlorinated salicylates(2-hydroxybenzoates) was examined under denitrifying,Fe (III) reducing, sulfate reducing andmethanogenic conditions. 3,6-Dichlorosalicylateand 6-chlorosalicylate are anaerobic microbialmetabolites of dicamba, a widely used herbicide.Anaerobic microcosms were established withdicamba treated soil from Wyoming, and golfcourse drainage stream sediments from NewJersey, which were each spiked with salicylate,3,6-dichlorosalicylate or one of the fourmonochlorosalicylate isomers. Salicylatewas degraded under denitrifying, sulfidogenic andmethanogenic conditions. In methanogenicenrichments 5-chlorosalicylate and 3-chlorosalicylatewere reductively dehalogenated to salicylatewhich was then utilized. Dehalogenation ofmonochlorinated salicylates to salicylate wasalso observed in denitrifying chlorosalicylatedegrading cultures. The study revealed thatthe position of the chlorine substituent as well as thepredominant electron accepting process affectthe rate and extent of chlorosalicylate degradationin anoxic environments.     

Sulfte-reduction process in sediments of Lake Kinneret,Israel

Monomictic Lake Kinneret is stratified during summer and autumn, resulting in a hypolimnion rich in H₂S (3–7 mg 1^–1). In winter and spring every year a bloom of dinoflagallate Peridinium gatunense produces an average biomass of 150000 ton wet weight. Part of this biomass sinks to the hypolimnion and sediments where it is decomposed and mineralized, with some of the mineralization due to the activity of sulfate-reducing bacteria (SRB). The sulfate-reduction potential of the upper sediment layer at the deepest part of the lake (42 m) was measured. The activity of the enzyme arylsulfatase was also monitored. Rates of sulfate-reduction ranged from a minimum of 12 nmoles SO_f4^p2–-reduced cm^–3 day^–1 in December before lake overturn to a maximum of 1673 nmoles SO_f4^p2– reduced cm^–3 day^–1 in July during stratification. These rates are considerably higher than those recorded from other freshwater lakes in the world and are probably limited more by the availability of organic matter than by sulfate concentrations.     

An Evaluation of Carbon Steel Corrosion under Stagnant Seawater Conditions

Corrosion of 1020 carbon steel coupons in natural seawater over a 1-year period was more aggressive under strictly anaerobic stagnant conditions than under aerobic stagnant conditions as measured by weight loss and instantaneous corrosion rate (polarization resistance). Under oxygenated conditions, a two-tiered oxide layer of lepidocrocite/goethite formed. The inner layer was extremely tenacious and resistant to acid cleaning. Under anaerobic conditions, the corrosion product was initially a non-tenacious sulphur-rich corrosion product, mackinawite, with enmeshed bacteria. As more sulphide was produced the mackinawite was transformed to pyrrhotite. In both aerobic and anaerobic exposures, corrosion was more aggressive on horizontally oriented coupons compared to vertically oriented samples.     

Induction characteristics of reductive dehalogenation in the ortho-halophenol-respiring bacterium,Anaeromyxobacter dehalogenans

Anaeromyxobacter dehalogenans strain 2CP-C dehalogenatesortho-substituted di- and mono-halogenated phenols and couples this activity to growth. Reductive dehalogenation activity has been reported to be inducible, however,this process has not been studied extensively. In this study, theinduction of reductive dehalogenation activity by strain 2CP-C is characterized. Constitutive 2-chlorophenoldechlorination activity occurs in non-induced fumarate-grown cells, with rates averaging 0.138 mol of Cl^- h^-1 mg of protein^-1. Once induced, these cultures dechlorinate 2-chlorophenol (2-CP) at rates as high as 116 mol of Cl^-1 h^-1 mg of protein^-1. Dechlorination of 2-CP is induced by phenol,2-chlorophenol, 2,4-dichlorophenol, 2,5-dichlorophenol, 2,6-dichlorophenol,and 2-bromophenol. Of the substrates tested, 2-bromophenol shows the highestinduction potential, yielding double the 2-chlorophenol dechlorination rate when compared to other inducing substrates. No induced dechlorination is observed at concentrations less than5 M 2-CP. When fumarate cultures were diluted 100-fold, fumarate reduction rates were reduced roughly according to the dilution factor, while dechlorination rates were similar in fumarate grown cells amended with 2-CP and cells diluted 100-fold prior to the addition of chlorophenol. This indicates that the majority of the fumarate-grown cells in late log phase were not induced when exposed to inducing substrates such as 2-CP. This observation may have ramifications on the success of bioaugmentation using halorespiring bacteria, which traditionally relies on growing culturesusing more readily utilized substrates. The rapid dechlorination rate and unique induction pattern also make strain 2CP-C a promising model organism for understanding the regulationof reductive dehalogenation at the enzymatic level.