胞外聚合物中蛋白质对好氧污泥颗粒化的影响

为确定胞外聚合物(EPS)中蛋白质(PN)对好氧颗粒污泥(AGS)形成的影响,研究了好氧污泥颗粒化过程,污泥EPS变化规律及其与污泥表面特性的相关性,分析了AGS和接种污泥EPS组分和相关官能团的差异并确定了EPS分布情况.结果 表明,在好氧污泥颗粒化期间,EPS中PN含量由13.98 mg·g-1增加到41.86 m...     

Relationship between chromium(VI) resistance and extracellular polymeric substances (EPS) concentration by some cyanobacterial isolates

BACKGROUND, AIM, AND SCOPE: Chromium(VI) resistance and its association with extracellular polymeric substance (EPS) concentration in cyanobacteria was investigated. Increased EPS concentration was associated with Cr(VI) resistance. The most resistant isolate, Chroococcus sp. H(4), secreted the most EPS (427 mg/L). MATERIALS AND METHODS: EPS concentration of the two most resistant isolates (Chroococcus sp. H(4) and Synechocystis sp. S(63)) was investigated following exposure to 15 and 35 ppm Cr(VI). The composition of EPS produced by Chroococcus sp. H(4) following exposure to 10 ppm Cr(VI) was analyzed using high-performance liquid chromatography. Control EPS was composed of glucose (99%) and galactronic acid (1%); in the presence of 10 ppm Cr(VI), EPS composition changed to glucose (9%), xylose (75%), rhamnose (14%), and galacturonic acid (2%). RESULTS AND DISCUSSION: Results indicated that (1) exposure to elevated concentrations of Cr(VI) affected the composition of EPS produced by Chroococcus sp. H(4), and (2) there was a correlation between Cr(VI) resistance and EPS concentration in some cyanobacteria.     

Influences of influent carbon source on extracellular polymeric substances (EPS) and physicochemical properties of activated sludge

It is necessary to understand the bioflocculation, settling and dewatering characteristics in the activated sludge process in order to establish more efficient operational strategies. The influences of carbon source on the extracellular polymeric substances (EPS) and flocculation, settling and dewatering properties of the activated sludge were investigated. Laboratory-scale completely mixed activated sludge processes were used to grow the activated sludge with different carbon sources of starch, glucose and sodium acetate. The sludge fed with acetate had highest loosely bound EPS (LB-EPS) and that fed with starch lowest. The amount of tightly bound EPS (TB-EPS), protein content in LB-EPS, polysaccharide content and protein contents in TB-EPS, were independent of the influent carbon source. The polysaccharide content in LB-EPS of the activated sludge fed with sodium acetate was lower slightly than those of starch and glucose. The sludge also had a nearly consistent flocs size and the sludge volume index (SVI) value. ESS content of the sludge fed with sodium acetate was higher initially, although it was similar to those fed with glucose and starch finally. However, the specific resistance to filtration and normalized capillary suction time fluctuated first, but finally were stable at around 5.0 × 10⁸ m kg⁻¹ and 3.5 s L g⁻¹ SS, respectively. Only the protein content in LB-EPS weakly correlated with the flocs size and SVI of the activated sludge. But there was no correlation between any other EPS contents or components and the physicochemical properties of the activated sludge.     

Influence of extracellular polymeric substances (EPS) on Cd adsorption by bacteria

The role of extracellular polymeric substances (EPS) in Cd adsorption by Bacillus subtilis and Pseudomonas putida was investigated using a combination of batch adsorption experiments, potentiometric titrations, Fourier transform infrared spectroscopy (FTIR). An increased adsorption capacity of Cd was observed for untreated bacteria relative to that for EPS-free bacteria. Surface complexation modeling of titration data showed the similar pK_a values of functional groups (carboxyl, phosphate and hydroxyl) between untreated and EPS-free bacteria. However, site concentrations on the untreated bacteria were found to be higher than those on the EPS-free bacteria. FTIR spectra also showed that no significant difference in peak positions was observed between untreated and EPS-free bacteria and carboxyl and phosphate groups were responsible for Cd adsorption on bacterial cells. The information obtained in this study is of fundamental significance for understanding the interaction mechanisms between heavy metals and biofilms in natural environments.     

氧化亚铁硫杆菌浸铜研究及胞外多聚物的作用

为了获得氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans,A.f)以及胞外多聚物(extracellular polymeric sub-stances,EPS)对铜浸出的作用结果,进行了透析袋实验,设置2个处理,2者的浸出液均为成熟菌液,但一个将铜片装入透析袋中以隔离A.f及EPS与铜的直接接触。结果表明:(1)菌液的处理和加透析袋的处理中铜都得到了浸出,240 h铜的浸出浓度分别为6 796 mg/L和1 366 mg/L,可知A.f及EPS与铜片直接接触能促进铜的浸出;(2)透析袋的处理中Fe3+保持较高浓度,说明Fe3+与EPS络合后被阻挡在透析袋外面从而不能与铜反应,可知EPS在A.f浸铜中起了媒介载体的作用;(3)2者的SEM图表明无透析袋的处理A.f与铜在实验初期发生了吸附,实验后期则无,实验初期铜快速浸出是由于传质距离短,而后期速度变缓是由于传质距离增大。     

Quantification of the interactions between Ca,Hg and extracellular polymeric substances (EPS) of sludge

The interactions between metals (Ca²⁺ and Hg²⁺) and extracellular polymeric substances (EPS) extracted from the aerobic and anaerobic sludge in wastewater treatment reactors were investigated using a combination of zeta potential measurement and 3-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analysis. Results show that Ca²⁺ had no substantial effects on the EEM fluorescence spectra of the EPS, but their zeta potentials increased with the increasing Ca²⁺ dosage. However, Hg²⁺ had a significant effect on the EEM fluorescence spectra of the EPS, while their zeta potentials seemed not to be affected by the dose of Hg²⁺. The interactions between Hg²⁺ and EPS were elucidated using the fluorescence quenching with PARAFAC analysis, while the interactions between Ca²⁺ and EPS were evaluated by the zeta potential technique. The binding constants for Hg²⁺ and EPS were two orders of magnitude higher than those for Ca²⁺ and EPS, suggesting that the binding mechanisms between Ca²⁺ and EPS were different from those between Hg²⁺ and EPS. The results might be useful for understanding the roles of EPS in bacterial self-protection against heavy metals and the aggregate formation mechanisms through ionic bridging interactions.     

膜生物反应器中EPS对污泥絮体形成的影响及其膜污染特性研究

为了给减缓膜生物反应器(MBR)膜污染提供新思路,对MBR中EPS各组分对污泥聚集性能的影响及其膜污染特性进行研究。通过分析MBR中污泥的聚集性,发现原始污泥的聚集速率常数为0.0151,提取EPS后污泥的聚集速率常数为0.00181,由此可以看出EPS在污泥聚集的过程中起重要作用。为了进一步明确EPS各组分对MBR中污泥聚集性能的影响,利用扩展的DLVO理论研究MBR中EPS及其各组分对污泥聚集性能的影响,发现MBR中EPS里粘液的二级能量最小值大约为-0.94 KT,松散型EPS(LB-EPS)为-2.98 KT,紧密型EPS(TB-EPS)为-3.87 KT,说明TB-EPS在污泥聚集的过程中起重要作用。进一步通过三维荧光光谱及EPS浓度分析,发现EPS各组分浓度及结构的不同导致EPS各组分对污泥聚集性起不同的作用。通过吸附实验、原子力显微镜观察发现EPS各组分的膜污染速率为:上清液 < 粘液 < LB-EPS < TB-EPS,由此,可以推测出减少粘液和LB-EPS含量可有效降低膜污染,同时对污泥絮体结构影响较小。     

Effect of ultrasonication and Fenton oxidation on biodegradation of bis(2-ethylhexyl) phthalate (DEHP) in wastewater sludge

The presence of bis(2-ethylhexyl) phthalate (DEHP) and its metabolites, i.e. 2-ethylhexanol, 2-ethylhexanal, and 2-ethylhexanoic acid in wastewater sludge (WWS) were investigated during aerobic digestion and Bacillus thuringiensis (Bt)-based fermentation of WWS. Ultrasonication and Fenton oxidation pre-treatment was applied to improve biodegradability of WWS and bioavailability of the target compounds for digestion and fermentation. DEHP and 2-ethylhexanoic acid were observed at higher concentration, meanwhile 2-ethylhexanol and 2-ethylhexanal were observed at lower concentration in WWS. After 20-day aerobic digestion, DEHP removal was 72%, 89%, and 85%, and 2-ethylhexanoic acid removal was 71%, 84%, 79%, respectively for raw, ultrasonicated, and Fenton-oxidized sludges. Bt was found to degrade DEHP, leading to DEHP removal of 21%, 40%, and 30%, respectively for raw, ultrasonicated, and Fenton-oxidized sludges in the fermentation. The results suggested that aerobic stabilization and Bt-based fermentation can remove the phthalates, and pre-treatment of WWS was also effective in improvement of DEHP biodegradation. Hence, Bt-based biopesticide production from WWS can be applied safely when taking into consideration the phthalate contaminants.     

Distribution of Se and its species in Myriophyllum spicatum and Ceratophyllum demersum growing in water containing Se (VI)

The uptake of Se (VI) by two aquatic plants, Myriophyllum spicatum L. and Ceratophyllum demersum L., and its effects on their physiological characteristics have been studied. Plants were cultivated outdoors under semi-controlled conditions and in two concentrations of Na selenate solution (20 μg Se L⁻¹ and 10 mg Se L⁻¹). The higher dose of Se reduced the photochemical efficiency of PSII in both species, while the lower dose had no effect on PSII. Addition of Se had no effect on the amounts of chlorophyll a and b. The concentration of Se in plants grown in 10 mg Se L⁻¹, averaged 212 ± 12 μg Se g⁻¹ DM in M. spicatum (grown from 8-13 d), and 492 ± 85 μg Se g⁻¹ DM in C. demersum (grown for 31 d). Both species could take up a large amount of Se. The amount of soluble Se compounds in enzyme extracts ranged from 16% to 26% in control, and in high Se solution from 48% to 36% in M. spicatum and C. demersum, respectively. Se-species were determined using HPLC-ICP-MS. The main soluble species in both plants was selenate (∼37%), while SeMet and SeMeSeCys were detected at trace levels.     

Soil metal concentrations and productivity of Betula populifolia (gray birch) as measured by field spectrometry and incremental annual growth in an abandoned urban Brownfield in New Jersey

A forested brownfield within Liberty State Park, Jersey City, New Jersey, USA, has soils with arsenic, chromium, lead, zinc and vanadium at concentrations above those considered ambient for the area. Using both satellite imagery and field spectral measurements, this study examines plant productivity at the assemblage and individual specimen level. Longer term growth trends (basal area increase in tree cores) were also studied. Leaf chlorophyll content within the hardwood assemblage showed a threshold model for metal tolerance, decreasing significantly beyond a soil total metal load (TML) of 3.0. Biomass production (calculated with RG - Red/Green Ratio Index) in Betula populifolia (gray birch), the co-dominant tree species, had an inverse relationship with the Zn concentration in leaf tissue during the growing season. Growth of B. populifolia exhibited a significant relationship with TML. Assemblage level NDVI and individual tree NDVI also had significant decreases with increasing TML. Ecosystem function measured as plant production is impaired at a critical soil metal load.     

Toxicity of lead on Ceriodaphnia dubia in the presence of nano-CeO(2) and nano-TiO(2)

Although engineered nanoparticles (NPs) could negatively impact environmental organisms, the synergistic effect of NPs and other toxic substances, which could be more significant than that of NP alone, have seldom been examined. The effect of two common NPs, nano-CeO₂ and nano-TiO₂, on the toxicity of Pb was evaluated using Ceriodaphnia dubia (C. dubia) as the model organism. Standard EPA procedures were followed in the toxicity evaluation. The toxicity of bare NPs (without Pb) was first evaluated and safe doses (levels without causing lethal effect) of NPs were used in the synergistic studies. It was found that the overall toxicity of Pb in the system containing NPs was greater than that of Pb alone, as indicted by the reduced median lethal concentration (LC₅₀) of soluble Pb. The sorption of Pb onto the NP, and the uptake of NPs in the gastrointestinal tract of C. dubia were validated. Therefore, the uptake of Pb-loaded NPs increased the exposure of C. dubia to Pb, resulting in the enhanced toxicity. Reducing the solution pH could shift Pb speciation and enhance the overall toxicity of Pb, with or without the presence of NPs.     

Bioaccumulation of persistent organic pollutants in female common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena) from western European seas: geographical trends, causal factors and effects on reproduction and mortality

Concentrations of polychlorinated biphenyls (PCBs) in blubber of female common dolphins and harbour porpoises from the Atlantic coast of Europe were frequently above the threshold at which effects on reproduction could be expected, in 40% and 47% of cases respectively. This rose to 74% for porpoises from the southern North Sea. PCB concentrations were also high in southern North Sea fish. The average pregnancy rate recorded in porpoises (42%) in the study area was lower than in the western Atlantic but that in common dolphins (25%) was similar to that of the western Atlantic population. Porpoises that died from disease or parasitic infection had higher concentrations of persistent organic pollutants (POPs) than animals dying from other causes. Few of the common dolphins sampled had died from disease or parasitic infection. POP profiles in common dolphin blubber were related to individual feeding history while those in porpoises were more strongly related to condition.     

Perfluorooctane sulfonate (PFOS) and other fluorochemicals in fish blood collected near the outfall of wastewater treatment plant (WWTP) in Beijing

Perfluorinated compounds (PFCs) were measured in zooplankton and five fish species collected from Gaobeidian Lake, which receives discharge from wastewater treatment plant (WWTP) in Beijing, China. The mean total PFCs in five fish were in the order: crucian carp > common carp > leather catfish > white semiknife carp > tilapia. Perfluorooctane sulfonate (PFOS) occurred at the greatest concentrations, with mean concentrations ranging from 5.74 to 64.2 ng/ml serum. Perfluorodecanoic acid (PFDA) was the second dominant PFC in fish samples except for common carp in which perfluorooctane sulfonamide (PFOSA) was dominant. A positive linear relationship (r² = 0.85, p < 0.05) was observed between ln PFOS concentrations (ln ng/ml) and trophic level (based on δ¹⁵N) if tilapia was excluded. The risk assessment showed that PFOS might not pose an immediate risk to fish in Gaobeidian Lake.     

The presence of Bacillus thuringiensis (Bt) protein in earthworms Eisenia fetida has no deleterious effects on their growth and reproduction

Earthworms Eisenia fetida, bred in substances with stover of two genetically-engineered Bacillus thuringiensis (Bt) corns (5422Bt1 (Event Bt11) and 5422CBCL (MON810)) expressing Cry1Ab and their near-isogenic non-Bt corn (5422), were used to investigate the non-target effects of Bt corn on soil-dwelling organisms. Cry1Ab concentrations in substances, casts and guts of E. fetida were also investigated by Enzyme-linked immunosorbent assay (ELISA). More than 90% individuals of E. fetida survived over a period of 30 d, irrespective of whether they received Bt corn or non-Bt corn. Compared to 5422 treatments, significantly higher relative growth rate and more number of new offspring and cocoons of E. fetida were found in 5422Bt1 and 5422CBCL treatments. These results were unlikely to be directly caused by Cry1Ab released from Bt corns but rather by differences in other factors of plants such as plant components (soluble sugar, total organic carbon, total protein and available phosphorus of Bt corns were more than 5422). ELISA results indicated immunoreactive Cry1Ab was detectable in substances, and the casts, guts of E. fetida from Bt corns treatments, of which the highest levels were detected in substances under the corresponding experimental conditions. With the increase of treated time, a strong decline was observed in Cry1Ab from substances and casts of E. fetida, whereas Cry1Ab in guts of E. fetida from 5422Bt1 treatments gradually increased and that from 5422CBCL treatments increased between 14 and 30 d. Therefore, the presence of Cry1Ab in E. fetida had no deleterious effects on their growth and reproduction.     

Atmospheric transport of urban-derived NH(x): Evidence from nitrogen concentration and delta(15)N in epilithic mosses at Guiyang, SW China

Nitrogen concentration and δ¹⁵N in 175 epilithic moss samples were investigated along four directions from urban to rural sites in Guiyang, SW China. The spatial variations of moss N concentration and δ¹⁵N revealed that atmospheric N deposition is dominated by NH_x-N from two major sources (urban sewage NH₃ and agricultural NH₃), the deposition of urban-derived NH_x followed a point source pattern characterized by an exponential decline with distance from the urban center, while the agricultural-derived NH_x was shown to be a non-point source. The relationship between moss N concentration and distance (y = 1.5e^−0.13x + 1.26) indicated that the maximum transporting distance of urban-derived NH_x averaged 41 km from the urban center, and it could be determined from the relationship between moss δ¹⁵N and distance [y = 2.54 ln(x) − 12.227] that urban-derived NH_x was proportionally lower than agricultural-derived NH_x in N deposition at sites beyond 17.2 km from the urban center. Consequently, the variation of urban-derived NH_x with distance from the urban center could be modeled as y = 56.272e^−0.116x − 0.481 in the Guiyang area.     

Development of enzyme-linked immunosorbent assay (ELISA) for glutathione S-transferase (GST-S) protein in the intertidal copepod Tigriopus japonicus and its application for environmental monitoring

To utilize the GST-S protein as a useful biomarker for environmental contamination, we developed a polyclonal antibody-based enzyme-linked immunosorbent assay (ELISA) in the intertidal copepod Tigriopus japonicus. Two polyclonal antibodies, TJ-GST-S1 and TJ-GST-S2, were raised against two TJ-GST-S synthetic peptides. Also a recombinant TJ-GST-S protein was purified as a standard for ELISA development. Each polyclonal antibody was tested by Western blot analysis and indirect ELISA. Of two polyclonal antibodies, TJ-GST-S2 ELISA was further employed due to its wide range of detection and the limit of specificity compared to those of TJ-GST-S1 ELISA system. After exposure to 4 metals (Ag, As, Cd, and Cu) to T. japonicus, the amount of TJ-GST-S protein was significantly elevated in a concentration-dependent manner. Also, TJ-GST-S protein was upregulated at relative high concentrations of B[α]P, PCB, and TBT. In this paper, we suggest that T. japonicas ELISA for TJ-GST-S2 is useful as a potential indicator system for marine contaminants.     

Cytogenetic status of human lymphocytes after exposure to low concentrations of p,p'-DDT, and its metabolites (p,p'-DDE, and p,p'-DDD) in vitro

Despite that the use of DDT has been restricted for more than 40 years to malaria affected areas, low doses of this pesticide and its metabolites DDE and DDD can be found in the environment around the world. Although it has been shown that these pollutants induce cell and DNA damage, the mechanisms of their cytogenotoxic activity remains largely unknown. This study looks into their possible genotoxic effects, at doses that can be found in body fluids, on human lymphocytes using the cytokinesis-block micronucleus assay and the comet assay. After exposure for 1, 6, and 24 h compounds p,p′-DDT (0.1 μg mL⁻¹), p,p′-DDE (4.1 μg mL⁻¹), and p,p′-DDD (3.9 μg mL⁻¹) showed increase in DNA damage. The most significant results were observed at exposure period of 24 h where number of micronucleated cells increased from control 2.5 ± 0.71 to 23.5 ± 3.54, 13.5 ± 0.71, and 16.5 ± 6.36 for DDT, DDE, and DDD, respectively. Similar effect was observed using comet test where the percentage of DNA in comets tail increased from control 1.81 ± 0.16 to 17.24 ± 0.55, 11.21 ± 0.56 and 9.28 ± 0.50 for each compound, respectively. At the same time Fpg-comet assay failed to report induction of oxidative DNA damage of these pollutants. Additionally, the type of cell death was determined using diffusion assay and necrosis dominated. Our findings suggest that even at low concentrations, these pesticides could induce cytogenetic damage to human peripheral blood lymphocytes and in that manner have the impact on human health as well.     

Determination of Hg and diet identification in otter (Lontra longicaudis) feces

An analytical procedure for the determination of Hg in otter (Lontra longicaudis) feces was developed, to separate fish scales for the identification of the animal diet. Samples were washed with ultra-pure water and the suspension was sampled and transferred for digestion. The solubilization was performed with nitric-perchloric acid mixture, and detection carried out by the atomic fluorescence spectrometry (AFS). The quality of the analytical procedure was assessed by analyzing in-house standard solutions and certified reference materials. Total Hg concentrations were in the range of 7.6-156 ng g(-1) (July 2004), 25.6-277 ng g(-1) (January 2005) and 14.6-744 ng g(-1) (May 2005) that is approximately the same order of magnitude for all samples collected in two reservoirs at the Tiete River, Brazil. Although Hg concentrations varied with sampling periods and diet, high levels were correlated to the percentage of carnivorous fish scales present in the otter feces.     

Belowground effects of enhanced tropospheric ozone and drought in a beech/spruce forest (Fagus sylvatica L./Picea abies [L.] Karst)

The effects of experimentally elevated O₃ on soil respiration rates, standing fine-root biomass, fine-root production and δ¹³C signature of newly produced fine roots were investigated in an adult European beech/Norway spruce forest in Germany during two subsequent years with contrasting rainfall patterns. During humid 2002, soil respiration rate was enhanced under elevated O₃ under beech and spruce, and was related to O₃-stimulated fine-root production only in beech. During dry 2003, the stimulating effect of O₃ on soil respiration rate vanished under spruce, which was correlated with decreased fine-root production in spruce under drought, irrespective of the O₃ regime. δ¹³C signature of newly formed fine-roots was consistent with the differing g_s of beech and spruce, and indicated stomatal limitation by O₃ in beech and by drought in spruce. Our study showed that drought can override the stimulating O₃ effects on fine-root dynamics and soil respiration in mature beech and spruce forests.