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1.
Sci Total Environ ; 702: 134993, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31726336

RESUMO

Since the establishment of the whole-contact sediment toxicity test using Heterocypris incongruens in 2012, this user-friendly method has been widely used for the assessment of many kinds of solid samples, such as sediment, soil, compost, and sewage sludge. There are two endpoints for this method: mortality and growth inhibition. Currently, there is no standard toxicity threshold established for the endpoint of growth inhibition. However, there is evidence showing that the calcite saturation state of the overlying water, which might be different among various samples, influences the growth and survival of H. incongruens. Thus, it is necessary to characterize the influence of the calcite saturation state to ensure that the test results are reliable and comparable among different samples. In the present study, we created artificial sediments comprised of quartz sand and 0-20% calcite particulates to manipulate the calcite saturation state in the overlying water and performed the test using H. incongruens for 6 d. The results show that a low calcite saturation state inhibited the growth of H. incongruens but had no effect on survival rate. The growth of ostracods was linearly related to the calcite saturation index of the overlying water. Additionally, a formula for artificial sediment consisting of 10% calcite and 90% quartz sand for the H. incongruens toxicity test was proposed. This study helps to distinguish H. incongruens growth inhibition caused by calcite saturation from that caused by toxicity.


Assuntos
Carbonato de Cálcio/química , Crustáceos/fisiologia , Poluentes Químicos da Água/toxicidade , Animais , Fenômenos Biológicos , Sedimentos Geológicos/química , Esgotos , Solo , Testes de Toxicidade , Poluentes Químicos da Água/normas
2.
Sci Total Environ ; 675: 141-150, 2019 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-31026638

RESUMO

Urban road dust can potentially have adverse effects on aquatic and benthic ecosystems if discharged into receiving waters; however, little is known about the mode of action of road dust toxicity within aquatic organisms. With an aim to reveal the biological effects of road dust on benthic crustacean species, we performed a de novo transcriptome analysis of the estuarine amphipod Grandidierella japonica exposed to road dust collected from highways around Tokyo. A transcriptome analysis by Illumina HiSeq 2500 identified differentially expressed genes related to the gamma-aminobutyric acid (GABA) signaling pathway, oxidative damage, and cuticle metabolism. Among these, a GABAB receptor subunit showed down-regulation in the road dust treatment, but a constant expression in the treatment of road dust with a carbonaceous resin XAD-4, which can reduce the acute toxicity of road dust to G. japonica. These results and the time course expressions of the related genes were partially confirmed by quantitative PCR (qPCR) experiments. Although the linkage between acute lethal toxicity and the molecular initiating events induced by road dust was still unclear, our findings provide lines of evidence to identify the causative toxicants in urban road dust.


Assuntos
Anfípodes/fisiologia , Poeira , Poluentes Ambientais/toxicidade , Anfípodes/efeitos dos fármacos , Animais , Monitoramento Ambiental , Perfilação da Expressão Gênica , Tóquio
3.
Sci Total Environ ; 668: 1267-1276, 2019 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-31018466

RESUMO

During runoff process, the urban road dust (URD) passes through the road-side gutters and detention tanks, where it gets hold for a certain period of time, hours to weeks, before making its way into the water bodies. A part of the water-exchangeable toxicants are leached by the water, and some strongly bound toxicants remain attached to the URD. Toxicity of urban runoff is dependent on holding time, water volume, and the type and composition of the wet road dust (WeRD) and leachate. However, there are no studies that have elucidated the manner in which toxicities of the WeRD and leachate vary during prolonged holding in the runoff processes. The main objectives of this research were to, i) identify the distribution of toxicants in the WeRD and leachate, and ii) evaluate the change in toxicity during prolonged holding. The URD samples that were collected from residential road, arterial road and highways in Tokyo, Japan, were mixed with moderately hard water in varying ratios (1:2 to 1:16) and were held for a certain time (1h to 5days) before centrifuging into the WeRD and leachate. Toxicity test was conducted with ostracod Heterocypris incongruens direct contact test. Toxicity of both the WeRD and leachate from residential area was not significantly greater than the 20% lethal limit. Toxicity of the WeRD from other stations initially decreased, further reached a minimum corresponding to the critical holding time, and it subsequently increased again. Toxicity of the arterial leachate gradually increased, whereas that of the highway leachate gradually decreased during 5days holding. Unionized ammonia and zinc were confirmed as one of the possible toxicants. This study proposes and verifies a model for the toxicity change of the WeRD during prolonged holding.


Assuntos
Crustáceos/efeitos dos fármacos , Poeira/análise , Poluentes Químicos da Água/análise , Poluição Química da Água/análise , Animais , Cidades , Monitoramento Ambiental , Fatores de Tempo , Tóquio , Testes de Toxicidade , Poluentes Químicos da Água/química , Poluentes Químicos da Água/toxicidade
4.
Environ Sci Technol ; 52(21): 12428-12435, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30265799

RESUMO

Interpretation of environmental DNA (eDNA) is a major problem hindering the application of this emerging technology for environmental monitoring. The decay characteristics and bioabundance estimation of different DNA fragment lengths are largely unknown, especially for eDNA captured from surface sediments. An estuarine amphipod, Grandidierella japonica, was used as the target species in this study. We conducted a lab-scale experiment using DNA extraction to clarify the effect of bacteria on eDNA decay. We also conducted a microcosm experiment using amphipods to clarify interpretations of information regarding eDNA decay and bioabundance estimation by using two fragments with different lengths (126 and 358 bp). It was found that the bacteria concentration accelerated eDNA decay, and long fragments were more susceptible to bacteria, thus decaying faster, than short fragments in the exponential decay period. The fresh eDNA (collected within 24 h of removing the amphipods) was more indicative of bioabundance than old eDNA (collected 240-480 h after removing amphipods), and short fragments better reflected bioabundance than long fragments. Finally, we compared the half-life of eDNA in surface sediment with that in a water sample and found that the temporal scales of surface sediment and water are similar (days to weeks). Our results suggest that surface sediment also has the potential to monitor the environment at a temporal scale similar to water.


Assuntos
DNA , Monitoramento Ambiental , Água Doce , Água
5.
Ecotoxicol Environ Saf ; 165: 440-449, 2018 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-30218967

RESUMO

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in urban environments. Urban road dust (URD) generated by traffic is an important PAH accumulator. Twelve priority PAHs in < 2000 µm fraction of ten URD samples from Tokyo, Japan were characterized based on profile distributions, carcinogenicity, toxicity, and source apportionment by cluster analysis, biplot and diagnostic ratios. PAH concentrations (mg/kg dry weight) in arterial roads, highways, highway parking, highway drainage pit and residential area URD samples were 2.06-4.24, 0.25-3.37, 3.44, 4.94, and 5.26 respectively, dominated by the ∑4 rings (average 46%) and ∑5 + 6 rings (average 41%) PAHs. Biplot analysis revealed that the antecedent dry weather period, vehicle frequency and organic matter content were the dominant environmental factors governing PAH profiles of different road types. The total amount of carcinogenic PAHs in the residential URD (2.12 mg/kg) was higher than those in the arterial road (0.60-2.00 mg/kg) and highway (0.10-1.84 mg/kg) URD. Toxic equivalent concentrations (TECs) of residential, arterial road and highway URD were 0.54, (0.12-0.57), and (0.02-0.51) mg/kg, respectively. The dominant PAH sources were found to be petrogenic combustion in arterial road and highway URD, and pyrogenic combustion consisting of a mix of biomass, petroleum and traffic-related sources in the residential and highway drainage pit samples. This is also the first study to find that TEC-based toxicity should not be taken as a measure of URD toxicity.


Assuntos
Poeira/análise , Poluentes Ambientais/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Carcinógenos/análise , Monitoramento Ambiental/métodos , Petróleo/análise , Tóquio , Tempo (Meteorologia)
6.
Environ Toxicol Chem ; 36(12): 3443-3449, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28755484

RESUMO

An acute sediment toxicity test using the ostracod Heterocypris incongruens is user friendly and has high sensitivity; however, a life-cycle test using this species has not been developed. The most challenging problem when developing a life-cycle test is that the egg development time varies greatly and is sometimes too long (> 150 d) to monitor. It is desirable to shorten the duration of life-cycle toxicity tests including the observation period of egg development while preserving the ecological relevance of the net reproductive rate (R0 ), an endpoint in the life-cycle test. Therefore, in the present study, we suggest a practical test duration for R0 using population growth rate (λ) as a measure of ecological relevance. We collected a range of life history characteristics of the ostracod by combining data from the literature and experimental results, constructed population matrix models, and calculated λ for 20 life history patterns. The results showed that a longer test period (> 150 d) did not increase the correlation coefficients between R0 and λ. Rather, a shorter test duration resulted in R0 being highly correlated with λ. Our results suggest that a life-cycle toxicity test using the ostracod can provide an ecologically relevant toxicity endpoint, even if the test is abandoned after approximately 50 d and unhatched eggs remain. Environ Toxicol Chem 2017;36:3443-3449. © 2017 SETAC.


Assuntos
Crustáceos/efeitos dos fármacos , Testes de Toxicidade/métodos , Poluentes Químicos da Água/toxicidade , Animais , Crustáceos/fisiologia , Estágios do Ciclo de Vida/efeitos dos fármacos , Reprodução/efeitos dos fármacos
7.
Ecotoxicol Environ Saf ; 143: 266-274, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28551584

RESUMO

This study reports on the development and application of a chronic sediment toxicity test using the benthic ostracod Heterocypris incongruens. H. incongruens reproduction parameters such as egg production, first day of brooding, egg-laying ratio, and hatching ratio were examined in this study. The test was first validated by determining the repeatability of the test method under seven control performances. The results showed good test repeatability of most endpoints, with coefficient of variation (CV) results below 15%. However, lifetime egg production, hatching ratio, and the reproductive rate were highly variable, with CVs ranging from 29.5% to 51.9%. Next, an application example of the proposed chronic method was performed using a series of urban road dust (URD) samples diluted with a reference sediment and compared to a 6 d H. incongruens toxicity test. The results of the proposed chronic test showed a statistically significant difference in the first day of brooding at 6.25% URD which did not exhibit significant mortality and growth inhibition in 6 d toxicity test.


Assuntos
Crustáceos/efeitos dos fármacos , Poeira/análise , Poluentes Ambientais/toxicidade , Sedimentos Geológicos/química , Testes de Toxicidade Crônica/métodos , Urbanização , Animais , Poluentes Ambientais/análise , Reprodução/efeitos dos fármacos , Estações do Ano , Tailândia
8.
Ecotoxicol Environ Saf ; 140: 206-213, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28260686

RESUMO

Biomarkers of exposure can be used to identify specific contaminants that are adversely affecting aquatic organisms. However, it remains prohibitively costly to investigate multiple novel biomarkers of exposure in a non-model species, despite the development of next-generation sequencing technology. In this study, we focused on the use of cDNA-amplified fragment length polymorphism (AFLP) as a cost-effective biomarker discovery tool to test whether it could identify biomarkers of exposure in the non-model amphipod species Grandidierella japonica. Loci were identified that were differentially expressed in amphipods exposed to reference chemicals (Cu, Zn, and nicotine) and to an environmental sample (road dust) at sublethal concentrations. Eight loci were shown to respond consistently to nicotine at different concentrations, but not to Cu or Zn. Some of the loci also responded to an environmental road dust sample containing nicotine. These findings suggest that loci identified using cDNA-AFLP could be used as biomarkers of nicotine exposure in environmental samples with complex matrices. Further studies with other organisms and toxicants are needed, but we have demonstrated that the use of cDNA-AFLP to identify biomarkers for ecotoxicological studies of non-model species is at least feasible.


Assuntos
Anfípodes/genética , DNA Complementar/genética , Polimorfismo Genético/genética , Anfípodes/efeitos dos fármacos , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados/métodos , Animais , Biomarcadores/metabolismo , Cobre/toxicidade , Poeira , Exposição Ambiental/efeitos adversos , Loci Gênicos , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Nicotina/toxicidade , RNA Mensageiro/genética , Transportes , Zinco/toxicidade
9.
Chemosphere ; 168: 1365-1374, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27919536

RESUMO

Urban road dust can potentially have adverse effects on ecosystems if it is discharged into receiving waters. This study investigated the causes of highway road dust toxicity by performing sediment toxicity identification evaluation (TIE) tests with an estuarine amphipod, Grandidierella japonica. In addition to metals and polycyclic aromatic hydrocarbons, which are traditionally considered to be the major toxicants in road runoff, we focused on dissolved nicotine as a causative toxicant. The sediment TIE results suggested that organic contaminants contributed to the majority of toxicity, and that the contribution of unionized nicotine to the toxicity was the highest among the chemicals considered. However, additional mortality tests with 48-h pulsed nicotine exposure demonstrated that exposure to nicotine at the same concentration as the baseline level in TIE tests did not cause significant 10-day amphipod mortality. Thus, the road dust toxicity could not be explained only by unionized nicotine, thereby suggesting contributions from joint effects of the measured toxicants and the presence of other unmeasured factors.


Assuntos
Anfípodes/efeitos dos fármacos , Poeira , Poluentes Ambientais/toxicidade , Animais , Poeira/análise , Monitoramento Ambiental , Metais/toxicidade , Nicotina/toxicidade , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Testes de Toxicidade
10.
Ambio ; 45(3): 290-301, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26531815

RESUMO

Estuarine and shallow coastal systems (ESCS) are recognized as not only significant organic carbon reservoirs but also emitters of CO2 to the atmosphere through air-sea CO2 gas exchange, thus posing a dilemma on ESCS's role in climate change mitigation measures. However, some studies have shown that coastal waters take up atmospheric CO2 (Catm), although the magnitude and determinants remain unclear. We argue that the phenomenon of net uptake of Catm by ESCS is not unusual under a given set of terrestrial inputs and geophysical conditions. We assessed the key properties of systems that show the net Catm uptake and found that they are often characteristic of human-dominated systems: (1) input of high terrestrial nutrients, (2) input of treated wastewater in which labile carbon is highly removed, and (3) presence of hypoxia. We propose that human-dominated ESCS are worthy of investigation as a contributor to climate change mitigation.


Assuntos
Carbono , Mudança Climática , Estuários , Água do Mar , Agricultura , Dióxido de Carbono , Atividades Humanas , Eliminação de Resíduos Líquidos
11.
Water Sci Technol ; 72(6): 1022-8, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26360764

RESUMO

Urban runoff can reach coastal aquatic environments; however, little is known about the effect of salinity on road runoff toxicity. The objective of this study is to investigate the toxicity of highway road dust over a salinity gradient from 5 to 35‰, in an estuarine benthic amphipod, Grandidierella japonica. Road dust toxicity was evaluated by assessing mortality after 10 days of exposure and short-term microbead ingestion activity of the amphipod. For all road dust samples considered, amphipod mortality increased with increasing salinity, whereas no significant difference in mortality was observed among test salinities in the reference river sediment. Ingestion activity during exposure to road dust decreased with increasing salinity. In fact, none of the individuals ingested any microbeads at salinity of 35‰. If assumed microbead ingestion is a proxy for feeding activity, high mortality at 35‰ could be attributed to aquatic exposure and not to dietary exposure. These findings suggest that road dust may have considerable impact on benthic organisms at high salinity levels.


Assuntos
Anfípodes/efeitos dos fármacos , Salinidade , Cloreto de Sódio/toxicidade , Animais , Poeira/análise , Japão , Masculino , Rios/química , Cloreto de Sódio/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/toxicidade
12.
Sci Total Environ ; 530-531: 96-102, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-26026413

RESUMO

The current study involves characterization of organic compounds, heavy metals, and ammonia as potential toxicants in one arterial road (St. 3) and two highway (St. 7 and 8) urban road dust (URD) collected in Tokyo, Japan. URD toxicity was evaluated by Toxicity Identification Evaluation using the ostracod Heterocypris incongruens direct contact test. URDs were treated with resins (10% XAD-4, 20% SIR-300 and 20% SIR-600) to determine the reduction in mortality after treatment. The mortality of ostracods exposed to St. 3 URD (baseline 80%) was significantly (p<0.05) reduced to 0% and 47% after XAD-4 and SIR-300 treatment respectively. This reduction led us to suspect hydrophobic organic compounds and heavy metals as potential toxicants. Subsequent elution of the recovered XAD-4 with polar (methanol, acetone) and non-polar (dichloromethane) solvents confirmed the dominance of relatively polar hydrophobic organic toxicants. The dissolved concentration of Cu and Zn after SIR-300 treatment exceeded the 50% lethal concentration (LC50) for ostracods, which led us to suspect Cu and Zn as other probable toxicants. The concentration of Zn in a SIR-300 acidic elutriate, recovered after the termination of toxicity test, confirmed Zn as one of the toxicants in St. 3. The baseline mortality (100%) of St. 7 was significantly reduced (23%) by SIR-300 treatment. This indicated the presence of heavy metals as the probable toxicant. However, the concentration of dissolved heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in the overlying water was below previously reported LC50 values for each metal in St. 7. Recovery of Zn concentrations exceeding the LC50 in the St. 7 SIR-300 elutriate led us to suspect a dietary exposure route of Zn to the ostracod during the direct contact test. The overall results indicate that the toxicant types can vary widely depending on the road sampled.


Assuntos
Poluentes Atmosféricos/toxicidade , Poeira , Monitoramento Ambiental , Animais , Crustáceos , Metais Pesados/toxicidade , Tóquio , Testes de Toxicidade , Poluentes Químicos da Água/toxicidade
13.
Water Res ; 69: 120-130, 2015 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-25463933

RESUMO

Seawater-driven forward osmosis (FO) is considered to be a novel strategy to concentrate nutrients in treated municipal wastewater for further recovery as well as simultaneous discharge of highly purified wastewater into the sea with low cost. As a preliminary test, the performance of FO membranes in concentrating nutrients was investigated by both batch experiments and model simulation approaches. With synthetic seawater as the draw solution, the dissolved organic carbon, phosphate, and ammonia in the effluent from a membrane bioreactor (MBR) treating municipal wastewater were 2.3-fold, 2.3-fold, and 2.1-fold, respectively, concentrated by the FO process with approximately 57% of water reduction. Most of the dissolved components, including trace metals in the MBR effluent, were highly retained (>80%) in the feed side, indicating high water quality of permeate to be discharged. The effect of membrane properties on the nutrient enrichment performance was investigated by comparing three types of FO membranes. Interestingly, a polyamide membrane possessing a high negative charge demonstrated a poor capability of retaining ammonia, which was hypothesized because of an ion exchange-like mechanism across the membrane prompted by the high ionic concentration of the draw solution. A feed solution pH of 7 was demonstrated to be an optimum condition for improving the overall retention of nutrients, especially for ammonia because of the pH-dependent speciation of ammonia/ammonium forms. The modeling results showed that higher than 10-fold concentrations of ammonia and phosphate are achievable by seawater-driven FO with a draw solution to feed solution volume ratio of 2:1. The enriched municipal wastewater contains nitrogen and phosphorous concentrations comparable with typical animal wastewater and anaerobic digestion effluent, which are used for direct nutrient recovery.


Assuntos
Membranas Artificiais , Nitrogênio/isolamento & purificação , Osmose , Fósforo/isolamento & purificação , Água do Mar/química , Águas Residuárias/química , Purificação da Água/métodos , Técnicas de Cultura Celular por Lotes , Estudos de Viabilidade , Concentração de Íons de Hidrogênio , Modelos Teóricos , Permeabilidade , Soluções , Eletricidade Estática , Água/química
14.
Environ Toxicol Chem ; 33(7): 1624-30, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24691681

RESUMO

The benthic ostracod Heterocypris incongruens is becoming an important tool for the ecotoxicological assessment of contaminated sediments. However, no study has yet explored solid-phase (dietary) exposure to ostracod. The present study examined the effects of metals on H. incongruens through aquatic and dietary exposures. The algal food Chlorella vulgaris was exposed to different concentrations of cadmium (Cd), copper (Cu), and zinc (Zn), and subcellular distributions of these metals in algal cells were determined. Parallel experiments were also performed to determine the toxic effects of dissolved metals on ostracod through aqueous exposure. Significant toxic effects on mortality were observed when ostracod were fed with Cd-contaminated (47-100%) and Cu-contaminated algae (55-100%). With increasing accumulated Zn in the algal cell, ostracod mortality also increased (20-83%). Aquatic exposure of ostracod to different concentrations of dissolved Cd (3.2-339 µg Cd/L) and Cu (260-2600 µg Cu/L) resulted in high observed mortalities (57-100% and 95-100%, respectively). Based on the results of aqueous and dietary exposure tests, it can be concluded that both exposure routes are important in evaluating the toxic effect of Cd on ostracod. Similar results were observed in tests using other metals (i.e., using Cu and Zn), thus emphasizing the importance of considering not only aquatic but also dietary exposure routes when evaluating metal toxicity to ostracod.


Assuntos
Cádmio/toxicidade , Cobre/toxicidade , Crustáceos/efeitos dos fármacos , Zinco/toxicidade , Animais , Crustáceos/fisiologia , Dieta
15.
J Hazard Mater ; 264: 53-64, 2014 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-24275471

RESUMO

Urban road dusts (URDs, n=10) were collected from arterial, residential, parking area in highway and highway roads in and around Tokyo, Japan, to characterize toxicity of size-fractions by the ostracod Heterocypris incongruens direct contact test. The URDs were collected with vacuum cleaner and highway sweeping vehicles, dried and size-fractionated before conducting toxicity test. The LC20 and LC50 of URDs varied (v/v) from 1.6 to 49%, and 3.8 to 67% respectively. Cluster analysis of URDs based on the concentration of heavy metal and PAHs standardized with the organic matter content was able to differentiate URDs into two groups, one group of higher toxicity and the other group of medium and lower toxicity. Mortality of ostracod decreased for some of the URDs when holding time of URD-water mixture was changed from 1h to 24h prior to the toxicity test. Fraction of fine particles was not always more toxic than the other fractions of coarse and medium particles. Site specific differences in toxicity of size-fractionated URDs indicated the complexity in defining URD toxicity as there could be co-existence of various non-targeted toxicants.


Assuntos
Crustáceos , Poeira/análise , Testes de Toxicidade , Animais , Cidades
16.
Water Sci Technol ; 67(12): 2699-705, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23787306

RESUMO

Twelve particle-bound polycyclic aromatic hydrocarbons (PAHs) were measured in the first flush regime of road runoff during nine events in Winterthur in Switzerland. The total PAH contents ranged from 17 to 62 µg/g. The PAH patterns measured at different time intervals during the first flush periods were very similar within each event irrespective of variation in suspended solids (SS) concentration within the first flush regime. However, the PAH patterns were different from event to event. This indicates that the environment plays an important role in PAH accumulation in SS. A toxicity identification evaluation approach using a toxicity equivalency factor (TEF) was applied to compare toxicities in the different events. The TEFs were found to be between 8 and 33 µg TEQ g(-1) (TEQ: toxic equivalent concentration). In some cases, two events having similar total PAH contents showed two fold toxicity differences.


Assuntos
Monitoramento Ambiental/métodos , Hidrocarbonetos Policíclicos Aromáticos/química , Transportes , Poluentes Químicos da Água/química , Chuva , Movimentos da Água
17.
Bioresour Technol ; 141: 29-34, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23499176

RESUMO

The aim of this study was to systematically compare the degradation of azo dye acid orange 7 by spongy pellets and attached biofilm of Coriolus versicolour (NBRC 9791) in a membrane bioreactor (MBR) under non-sterile conditions. Mild stirring (35 rpm) resulted in spherical (φ=0.5 cm), spongy pellets and concomitantly triggered high enzymatic activity of the fungus, allowing for excellent decolouration (>99%) of a synthetic wastewater containing the dye. However, bacterial contamination eventually damaged the fungus pellets, leading to decreased decolouration efficiency. Promotion of attached growth on a plastic support along with formation of spherical spongy pellets allowed maintenance of high enzymatic activity and decolouration/degradation for an extended period. Hydraulic retention time (HRT) could influence the level of enzymatic activity and decolouration; however, even at the shortest HRT (1 day) examined, the MBR could accomplish >95% decolouration.


Assuntos
Compostos Azo/análise , Basidiomycota/metabolismo , Reatores Biológicos , Purificação da Água/métodos , Compostos Azo/química , Compostos Azo/metabolismo , Basidiomycota/fisiologia , Biodegradação Ambiental , Biofilmes , Cor , Membranas Artificiais
18.
Sci Total Environ ; 409(12): 2366-72, 2011 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-21458026

RESUMO

Road dust is considered an important source of sediment contamination; however, there are few studies on the toxicity of road dust on benthic organisms. This study evaluates the toxicity of road dust on the benthic ostracod, Heterocypris incongruens, through a 6-day direct exposure experiment. All six road dust samples collected in heavy traffic areas caused high mortality of the ostracod, whereas the road dust collected in a residential area did not show toxicity to the ostracod. After maintaining the mixture of road dust and water for 24 h, the toxicity of the road dust decreased significantly for three of the six samples in the heavy traffic areas, suggesting these road dust samples become less toxic in the surface runoff process. In addition, we conducted the same toxicity test on manipulated road dust using different solid/liquid ratios and holding times to evaluate the change in toxicity caused by the runoff process. Wet road dust that had been separated from a dust-water mixture after a holding time of 1 h or 24 h did not show lethal toxicity, while the water-soluble fraction of the mixture caused high mortality of the ostracod at a solid/liquid ratio of 1:2 and 1:4. However, after a 7-day holding time of the dust-water mixture, the wet road dust and the water-soluble fraction showed lethal toxicity to the ostracod. These results suggest that toxicants of road dust seemed to exist mainly in water soluble fraction eluted off by rain water; however, particle-bound fraction again showed lethal toxicity after 7 days of incubation.


Assuntos
Automóveis/estatística & dados numéricos , Crustáceos/efeitos dos fármacos , Poeira/análise , Testes de Toxicidade/métodos , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade , Animais , Monitoramento Ambiental , Metais Pesados/análise , Metais Pesados/toxicidade
19.
Water Res ; 45(6): 2199-206, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21310458

RESUMO

The long-term performance of a bioaugmented membrane bioreactor (MBR) containing a GAC-packed anaerobic zone for treatment of textile wastewater containing structurally different azo dyes was observed. A unique feeding strategy, consistent with the mode of evolution of separate waste streams in textile plants, was adopted to make the best use of the GAC-zone for dye removal. Dye was introduced through the GAC-zone while the rest of the colorless media was simultaneously fed through the aerobic zone. Preliminary experiments confirmed the importance of coupling the GAC-amended anaerobic zone to the aerobic MBR and also evidenced the efficacy of the adopted feeding strategy. Following this, the robustness of the process under gradually increasing dye-loading was tested. The respective average dye concentrations (mg/L) in the sample from GAC-zone and the membrane-permeate under dye-loadings of 0.1 and 1 g/L.d were as follows: GAC-zone (3, 105), permeate (0, 5). TOC concentration in membrane-permeate for the aforementioned loadings were 3 and 54 mg/L, respectively. Stable decoloration along with significant TOC removal during a period of over 7 months under extremely high dye-loadings demonstrated the superiority of the proposed hybrid process.


Assuntos
Reatores Biológicos , Carvão Vegetal/química , Resíduos Industriais/análise , Membranas Artificiais , Têxteis , Eliminação de Resíduos Líquidos/instrumentação , Purificação da Água/instrumentação , Aerobiose , Anaerobiose , Compostos Azo/química , Compostos Azo/isolamento & purificação , Biodegradação Ambiental , Carbono/análise , Cor , Corantes/química , Corantes/isolamento & purificação , Naftalenos/química , Naftalenos/isolamento & purificação , Fatores de Tempo
20.
Water Sci Technol ; 62(9): 2044-50, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-21045330

RESUMO

This study was aimed at comparing the Zn and Cu binding parameters with dissolved organic matter (DOM) in road runoff, wastewater treatment plant (WWTP) effluent and influent. Conditional stability constant (K') and binding site concentration ([L]) are important to predict free or labile metal concentration and toxicity in the water environment. The values of K' and [L] of three DOMs were determined by metal titration and Scatchard linearization. The Zn and Cu titration data for DOMs in WWTP effluent and influent fitted to a two-ligand model, while DOM in road runoff fitted to a single-ligand model. The order of the values of K' was WWTP influent > WWTP effluent > road runoff both for Zn and Cu. Total ambient binding site concentration ([L(T)]) was lower in DOM of road runoff (1.4-1.5 µM) than those in DOM of WWTP effluent (1.6-2.3 µM) and influent (17-18 µM), suggesting lower metal complexation capacity in DOM of road runoff. DOM in WWTP influent was expected to bind to both Zn and Cu more strongly than that of the effluent DOM.


Assuntos
Cobre/química , Eliminação de Resíduos Líquidos , Movimentos da Água , Poluentes Químicos da Água/química , Zinco/química , Cidades , Características da Família , Compostos Orgânicos
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