Although the Ibirité reservoir (an urban tropical eutrophic reservoir) has been the recipient of the discharge of a large volume of raw urban sewage, the key cause of ecosystem degradation has been historically solely attributed to the discharge of effluents from an oil refinery. This fact motivated an investigation to unravel the compositions of contaminants in the sediments to evaluate their distributions, possible sources, and potential impacts on sediment–water quality. The concentrations of polycyclic aromatic and aliphatic hydrocarbons and of metals and metalloids were, in general, significantly lower than some selected polluted sites used for comparison. Calculated distribution indexes showed that the hydrocarbon sources were petrogenic, pyrogenic, and biogenic. Only a few PAHs exceeded the threshold effects level (TEL) guideline. Industrial activities are the presumed sources of metals and metalloids except for copper, which is from copper sulfate used as algaecide in the reservoir. The bioavailable concentrations of some metal and metalloid exceeded the TEL–PEL guidelines. The acid volatile sulfide concentration was greater than that of the simultaneously extracted metals in the clayey–silty reservoir sediments, whereas the opposite result was observed for the sandy sediments of the tributaries. The sediment interstitial water toxic units were >1 for metals, thus indicating that metals are potentially toxic to the benthos. Considering the data set generated in this study, it can be concluded that the degradation of Ibirité reservoir and its tributaries cannot be solely attributed to the input of hydrocarbons, but predominantly to the discharge of raw urban sewage and effluents from other industrial sources. 相似文献
An accidental explosion occurred in a waste storage tank at an incineration plant in Kawasaki, Japan, on May 11, 1997. The
accident was caused primarily by unintended mixing involving reactive chemicals, such as organic peroxides (POs) and acrylonitrile
(AN). The PO initiated polymerization of AN and the heat released during the polymerization led to a runaway reaction and
explosion. POs are widely used in the chemical industry and can be self-reactive and hazardous when mixed with other chemicals
such as acids and alkalis. The goal of this study was to obtain a better understanding of the mixing hazard of chemicals through
an evaluation of POs with other chemicals using conventional experimental techniques such as glass test-tube tests, Dewar
vessel tests, and differential scanning calorimetry (DSC). Seven types of POs were mixed with AN. Test results were classified
into four ranks based on the hazard criteria. In addition, di(2-ethylhexyl)-peroxydicarbonate/AN mixtures were investigated
in detail and the influences of the mixing ratio and the stirring rate were examined. 相似文献
Experimentally determined photodegradation pathways of hexachlorobenzene (HCB), a chlorinated aromatic compound, in hexane, 2-propanol (IPA), and methanol were compared with those predicted by quantum chemical calculation based on density functional theory (DFT), and the adequacy of the prediction method was evaluated. The experimental main degradation pathways of HCB were virtually the same for the three solvents and also agreed with the predicted main degradation pathways. In the DFT method, the main degradation product was the dechlorinated benzene at the position where the C-Cl bond was predicted to have the lowest bond dissociation energy. This result suggested that the photodechlorination pathways of chlorinated aromatic compounds could be predicted by comparing the bond dissociation energies calculated with the DFT method. 相似文献
Since 1983, the Ministry of the Environment of Japan has conducted nation-wide acid deposition surveys. To investigate the
effects of acid deposition on surface water, we used the nonparametric Mann–Kendall test to find temporal trends in pH, alkalinity,
and electrical conductivity (EC) in more than 10 years of data collected from five lakes and their catchments (Lake Kuttara:
northernmost; Lake Kamakita: near Tokyo; Lake Ijira: central; Lake Banryu: western; and Lake Unagiike: southernmost). The
pH of Lake Ijira water has declined slightly since the mid-1990s, corresponding with the downward trends seen in the pH and
alkalinity of the river water flowing into the lake. There were significant upward trends in the EC of both the lake and stream
water; the same trends were also found for concentrations. These trends show evidence of acidification due to atmospheric deposition, and this is the first such finding
in Japan based on significant long-term trends. Lake Ijira is located about 40 km north of the Chukyo industrial area near
Nagoya. The annual depositions of H+, nss-, and in Lake Ijira were among the highest of all deposition monitoring sites, suggesting that this is the main cause of the significant
acidification observed in Lake Ijira. No significant trends suggesting acidification were observed in any of the other lake
catchments in spite of the significant upward trends in EC. Upward trends in pH and alkalinity at Lake Banryu and upward trends
in alkalinity at Lake Kamakita were detected, but no change in pH or alkalinity at Lake Kuttara and Lake Unagiike was observed. 相似文献
Objective: Hazard perception (HP) is the ability to identify a hazardous situation while driving. Though HP has been well studied among neurologically intact populations, little is known about the HP of neurologically impaired populations (in this study, stroke patients). The purpose of this study is, first, to investigate the HP of stroke patients and, second, to verify the effect of lesion side (right or left hemisphere) on HP, from the viewpoint of hazard types.
Methods: Sixty-seven neurologically intact age-matched older drivers and 63 stroke patients with valid driver’s licenses conducted a video-based Japanese HP task. Participants were asked to indicate the hazardous events in the driving scenario. These events were classified into 3 types: (1) behavioral prediction hazards (BP), which are those where the cause is visible before it becomes a hazard; (2) environmental prediction hazards (EP), which are those where the ultimate hazard may be hidden from view; and (3) dividing and focusing attention hazards (DF), which are those where there is more than one potential hazard to monitor on approach.Participants also took part in the Trail Making Test (TMT) to evaluate visual information processing speed.
Results: The results showed that the number of responses was significantly fewer for stroke patients than for age-matched drivers for all hazard types (P < .001), and this difference was not affected by lesion side (P > .05). It was also found that stroke patients showed a slower response time than age-matched drivers only for BP (P < .001). The lesion side did not affect response latency (P > .05). Results of the TMT revealed that age-matched drivers completed the task significantly faster than stroke patients (P < .001) and that neither TMT-A nor TMT-B differentiated between patients with left hemisphere damage and patients with right hemisphere damage (P > .05).
Conclusions: Firstly, HP in stroke patients is low compared to age-matched drivers. Secondly, even if stroke patients notice hazards, their response may be delayed in a BP situation, due to a slower visual information processing speed. Thirdly, the lesion side does not appear to affect HP. 相似文献
We tried to decolorize mixtures of four reactive textile dyes, including azo and anthraquinone dyes, by a white-rot basidiomycete Phanerochaete sordida. P. sordida decolorized dye mixtures (200 mg l-1 each) by 90% within 48 h in nitrogen-limited glucose-ammonium media. Decolorization of dye mixtures needed Mn2+ and Tween 80 in the media. Manganese peroxidase (MnP) played a major role in dye decolorization by P. sordida. Decolorization of dye mixtures by P. sordida was partially inhibited by polyvinyl alcohol (PVA) that wastewaters from textile industries often contain. This was caused by an inhibitory effect of PVA on the decolorization of Reactive Red 120 (RR120) with MnP reaction system. Second addition of Tween 80 to the reaction mixtures in the presence of PVA improved the decolorization of RR120. These results suggest that PVA could interfere with lipid peroxidation or subsequent attack to the dye. 相似文献
This study reports the first known studies to investigate the thermal degradation of a polyester/cellulose fabric substrate ("article") treated with a fluorotelomer-based acrylic polymer under laboratory conditions conservatively representing typical combustion conditions of time, temperature, and excess air level in a municipal incinerator, with an average temperature of 1000 degrees C or greater over approximately 2s residence time. The results demonstrate that the polyester/cellulose fabric treated with a fluorotelomer-based acrylic polymer is destroyed and no detectable amount of perfluorooctanoic acid (PFOA) is formed under typical municipal incineration conditions. Therefore, textiles and paper treated with such a fluorotelomer-based acrylic polymer disposed of in municipal waste and incinerated are expected to be destroyed and not be a significant source of PFOA in the environment. 相似文献
The decrease of trichlorophenol by injecting oxidation catalyst into a municipal solid waste incinerator was monitored in real time. Direct sampling atmospheric pressure chemical ionization (APCI)/ion trap mass spectrometry (ITMS) was used for the real-time monitoring. The oxidation catalyst was iron oxide type, which exponentially reduced trichlorophenol emission. CO emission, however, did not show any correlation with the catalyst injection rate. Simultaneous analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) suggested that real-time monitoring of trichlorophenol as a surrogate of PCDDs/PCDFs, has a potential to timely control the optimum injection rate of PCDD/PCDF suppression catalyst continuously and economically. 相似文献