Over the past few years, a large number of studies have been conducted on the use of ultrasound for decomposition of harmful
organic pollutants, particularly chlorinated aromatic hydrocarbons (CAH) in wastewater. The published reports cover a variety
of applications, including both ultrasonic treatment alone and in combination with other methods, e.g., advanced chemical
oxidation processes. This article presents a review of recent work on ultrasonic-based methods of CAH decomposition, with
emphasis on the applications of ultrasound alone and in combination with Fenton's reagent, as attractive advanced oxidation
systems. In the first part of this review, the basic principles of sonochemical treatment are presented, followed by a review
of the applications of ultrasound alone for CAH degradation. In the second part, the mechanisms of CAH degradation with Fenton's
reagent and its application for CAH degradation are summarized. In the final part, studies on the applications of ultrasound
together with Fenton's reagent are reviewed. The reported results suggest that a combination of ultrasound and Fenton's reagent
is more attractive for practical application than the use of either method separately. Further studies, however, are required
in this area because the reaction mechanism and the relationship between the reaction rates and process parameters for such
a combined process are not yet well established. 相似文献
Attempts were made to analyze the toxin composition of the toxic hiogi scallop Chlamys nobilis. The toxins were partially purified from the digestive glands by column chromatography using Bio-Gel P-2 and Bio-Rex 70 (H+ form), resulting in separation into protogonyautoxin (PX), gonyautoxin (GTX) and saxitoxin (STX) fractions. Their total potencies were scored to be <100 mouse units (MU), 3200 MU and 3700 MU, respectively. A 5-min hydrolysis with 0.1 N HCl enhanced the potencies of PX and GTX fractions to 450 MU and 12000 MU respectively, whereas no enhancement occurred in the STX fraction at all. Electrophoretic, thin-layer chromatographic and high performance liquid chromatographic analyses demonstrated that the PX fraction consisted mainly of GTX8 and its epimer, the GTX fraction of GTX5, GTX6, along with two unidentified toxins, and the STX fraction exclusively of two unidentified toxins. This rather unique composition suggested a complex metabolism of PSP in this species. 相似文献
The article used two NOAA-14 Advanced Very High ResolutionRadiometer (AVHRR) datasets to assess flood damage in the middleand lower reaches of China's Changjiang River (Yangtze River) in 1998. As the AVHRR is an optical sensor, it cannot penetratethe clouds that frequently cover the land during the flood season, and this technology is greatly limited in flood monitoring. However the widely used normalized difference vegetation index (NDVI) can be used to monitor flooding, sincewater has a much lower NDVI value than other surface features.Though many factors other than flooding (e.g. atmospheric conditions, different sun-target-satellite angles, and cloud) can change NDVI values, inundated areas can be distinguished fromother types of ground cover by changes in the NDVI value beforeand after the flood after eliminating the effects of other factors on NDVI. AVHRR data from 26 May and 22 August, 1998 wereselected to represent the ground conditions before and after flooding. After accurate geometric correction by collecting GCPs,and atmospheric and angular corrections by using the 6S code, NDVI values for both days and their differences were calculatedfor cloud-free pixels. The difference in the NDVI values betweenthese two times, together with the NDVI values and a land-use map, were used to identify inundated areas and to assess the arealost to the flood. The results show a total of 358 867 ha, with 207 556 ha of cultivated fields (paddy and non-irrigated field) inundated during the flood of 1998 in the middle and lower reaches of the Changjiang River Catchment; comparing with the reported total of 321 000 and 197 000 ha, respectively. The discrimination accuracy of this method was tested by comparing the results from two nearly simultaneous sets of remote-sensingdata (NOAA's AVHRR data from 10 September, 1998, and JERS-1 synthetic aperture radar (SAR) data from 11 September, 1998, with a lag of about 18.5 hr) over a representative flooded regionin the study area. The results showed that 67.26% of the total area identified as inundated using the NOAA data was also identified as inundated using the SAR data. 相似文献
The present study aimed to investigate the potential ammonia (NH3) emission from flag leaves of paddy rice (Oryza sativa L. cv. Koshihikari). The study was conducted at a paddy field in central Japan that was designed as a free-air CO2 enrichment (FACE) facility for paddy rice. A dynamic chamber method was used to measure the potential NH3 emissions. The air concentrations of NH3 at two heights (2 and 6 m from the ground surface) were measured using a filter-pack method, and the exchange fluxes of NH3 of the whole paddy field were calculated using a gradient method. The flag leaves showed potential NH3 emissions of 25-38 ng N cm−2 h−1 in the daytime from the heading to the maturity stages, and they showed potentials of approximately 22 ng N cm−2 h−1, even in the nighttime, at the heading and mid-ripening stages. The exchange fluxes of NH3 of the whole paddy field in the daytime were net emissions of 0.9-3.9 g N ha−1 h−1 whereas the exchange fluxes of NH3 in the nighttime were approximately zero. 相似文献
To assess the potential endocrine disruptive effects through multiple nuclear receptors(NRs),especially non-steroidal NRs,in municipal wastewater,we examined the agonistic activities on four NRs(estrogen receptor α,thyroid hormone receptor α,retinoic acid receptor α and retinoid X receptor α) of untreated and treated wastewater from municipal wastewater treatment plants(WWTPs) in Japan using a yeast two-hybrid assay.Investigation of the influent and effluent of seven WWTPs revealed that agonistic activities... 相似文献
The fate of pharmaceuticals after discharged from hospital into wastewater was clarified experimentally by using a new lab-scale conventional activated sludge (CAS) treatment reactor. The 43 target compounds belong to nine therapeutic classes (antivirals, antibacterials, anticancer drugs, psychotropics, antihypertensives, analgesic–antipyretics, contrast media, herbal medicines, and phytoestrogens) were selected with inclusion of 16 newly estimated compounds. The efficiency of the present reactor was estimated by comparing the reaction rate constant of the solid-water partition coefficients (log Kd) between liquid and solid samples and half-life during 48-h experiment obtained by using hospital effluents with those obtained by using STP wastewater. The results that no significant difference in removal efficiency was observed between both water samples (P?>?0.05) indicate high reliability of the present lab-scale reactor. The actual rates of removal when hospital effluent was applied varied widely (mean, 59?±?40%) independent of type of the pharmaceuticals. More than 90% of 17 compounds were removed after 8 h of treatment. However, the values for psychotropics (mean, 19?±?26%) and contrast media (mean, 24?±?17%) were generally low, indicating high stability. The log Kd values ranged from 1.3 to 4.8. Notably, clarithromycin, acridine, and glycitein could be removed in both liquid and solid phases. The dominant removal mechanisms were found to be different for individual pharmaceutical. These results suggest the effectiveness of introduction of the lab-scale biological treatment system for development of a new solution for discharge of pharmaceuticals from hospital.
ABSTRACT The use of activated carbon fiber (ACF) filters for the capture of particulate matter and elemental Hg is demonstrated. The pressure drop and particle collection efficiency characteristics of the ACF filters were established at two different face velocities and for two different aerosols: spherical NaCl and combustion-generated silica particles. The clean ACF filter specific resistance was 153 kg m-2 sec-1. The experimental specific resistance for cake filtration was 1.6 × 106 sec-1 and 2.4 × 105 sec-1 for 0.5- and 1.5-μm mass median diameter particles, respectively. The resistance factor R was approximately 2, similar to that for the high-efficiency particulate air filters. There was a discrepancy in the measured particle collection efficiencies and those predicted by theory. The use of the ACF filter for elemental Hg capture was illustrated, and the breakthrough characteristic was established. The capacity of the ACF filter for Hg capture was similar to other powdered activated carbons. 相似文献