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721.
Pierre-Franois Biard Annabelle Couvert Christophe Renner Jean-Pierre Levasseur 《Chemosphere》2009,77(2):182-187
Dimethyl disulphide (DMDS) removal was investigated in a compact scrubber (hydraulic residence time ≈20 ms), composed of a wire mesh packing structure where liquid and gas flow at co-current and high gas superficial velocity (>12 m s−1). In order to regenerate the scrubbing liquid and to maintain a driving force in the scrubber, ozone and hydrogen peroxide were added to water since they allow the generation of nonselective and highly reactive species, hydroxyl radicals HO. Three ways of reagent distribution were tested. The influence of several parameters (liquid flow rate(s), ozone flow rate, pH and reagent concentrations) was investigated. The best configuration was obtained when ozone is transferred in the scrubbing liquid before introduction at the top of the scrubber simultaneously with the hydrogen peroxide solution, allowing to generate hydroxyl radical in the scrubber. With this configuration, DMDS removal could be increased from 16% with water to 34% at the same gas and liquid flow rates in the scrubber showing the potentiality of advanced oxidation process. 相似文献
722.
723.
Background, aim, and scope The pulp and paper industry is the sixth largest polluter discharging a variety of gaseous, liquid, and solid wastes into
the environment. Effluents from bleached Kraft mill effluents (BKME) are polluting waters to a great extent These effluents
cause considerable damage to the receiving waters if discharged untreated since they have high levels of biological oxygen
demand (BOD), chemical oxygen demand (COD), chlorinated compounds (measured as AOX), suspended solids (mainly fibers), fatty
acids, tannins, resin acids, lignin and its derivatives, sulfur and sulfur compounds, etc. This study aimed to remove adsorbed
organic halogen (AOX), total nitrogen, and lignin-degrading products in the wastewater (4,500 m3/h) from the paper mill in the pulp and paper industry, which is discharged to sea from a plant located in western Turkey.
Materials and methods The photocatalytic degradation of AOX, total nitrogen, and chlorinated lignin in BKME have been investigated in different
parameters, such as time, H2O2 and TiO2 concentration. In addition, for investigating the effect of chlorine on the removal of lignin, pure lignin solution was prepared
in equal amounts to chlorinated lignin degradation products found in BKME. The same experiments were conducted for this solution.
Experiments were carried out in photocatalytic reactor made of Pyrex glass. The mercury lamp was used as a radiation source.
All irradiation was carried out under constant stirring. The existence of dissolved O2 is an important factor which increases the photocatalytic degradation. Hence, we used an air pump for the aeration of the
wastewater solutions. The temperature of the wastewater was controlled and adjusted to 25°C by thermostat pump in conjunction
with a cooler. At the end of all experiments, AOX, total nitrogen and lignin concentrations were analyzed according to standard
methods. All experiments were performed in duplicate and average values were used.
Results and discussion When the effect of H2O2 and time were investigated, it was observed that the AOX concentration increased from 3.0 to 11.0 mg/L by only UV. However,
when H2O2 was added, AOX concentration decreased from approximately 3.0 to 0.0 mg/L. The optimal conditions for the removal of AOX
appear to be an initial H2O2 concentration of 20.0 mL/L and reaction time of 50 min. In addition, at the same experiment conditions, it was seen that
the total nitrogen concentration decreased from 23.0 to 15.0 mg/L by only UV and by increasing H2O2 concentration, the concentration of 20.0 mL/L H2O2 appears to be optimal (9.0 mg/L). The AOX, total nitrogen and lignin degradation products and pure lignin go through a minimum
when the concentration of H2O2 and TiO2 increases at constant pH and UV intensity. The kinetics for the degradation of AOX, total nitrogen and lignin degradation
products followed a pseudo-first order law with respect to the products, and the degradation rates (min−1) for the UV/TiO2/H2O2 system were higher than that of the corresponding values for the UV/H2O2 system.
Conclusions The AOX, total nitrogen and lignin concentration go through a minimum when the concentration of H2O2 and TiO2 increases at constant pH and UV intensity. It was found that the UV/TiO2/H2O2 system has proved capable of the degradation of total nitrogen as well as chlorinated and degraded lignin in BKME.
Recommendations and perspectives The photocatalytic process can be considered a suitable alternative for the remove of some compounds from the BKME. Nevertheless,
further studies should be carried out to confirm the practical feasibility of BKME. Another result obtained from the study
is that pre-purification carried out with UV/TiO2/H2O2 photocatalytic process may constitute an important step for further purification processes such as adsorption, membrane processes,
etc. 相似文献
724.
Isaac Luginaah Kevin Smith Ada Lockridge 《Journal of Environmental Planning and Management》2010,53(3):353-370
This study examines the perceptions and coping strategies of the Aamjiwnaang First Nation, which is surrounded by ‘Chemical Valley’, the largest complex of petrochemical plants in Canada. Analysis of in-depth interviews showed that residents perceive ‘Mother Earth to be sick’; however, a strong level of community cohesion prevails, with ‘place’ as a significant anchor to the culture and history of the community. Residents articulated a collective sense of responsibility for the well-being of members both within and surrounding the community, whereby some residents would never leave, regardless of the toxic environment and concern for high rates of cancer and respiratory diseases among both adults and children. Residents employed action-focused coping strategies such as ‘indoor evacuation’ and the ‘Cop-sniff test’, and emotional coping strategies including blocking out the effects of ‘Chemical Valley’ by frequently ignoring warning sirens from industry. The results call on the need for a collaborative environmental planning intervention involving clear community participation. Findings suggest the need for an indoor recreational facility for both children and adults, and a graded warning system. 相似文献
725.
726.
Screening level risk assessment models are used by many countries to assess the treatability of organic chemicals during the sewage treatment process, especially those that are new to commerce. The performance of one such model, the sewage treatment plant model, is evaluated in the current study by comparing model predictions with actual measurement data collected at various stages of a typical full-scale activated sludge type sewage treatment plant. A suite of ten polycyclic aromatic hydrocarbons (PAHs) with widely varying physico–chemical properties were monitored for the comparison. Model predicted removal efficiencies were in very good agreement with those measured for all ten PAHs. Observed chemical concentrations and their trends at various stages of the sewage treatment process were also well simulated by the model. Results also suggest that a reasonable first approximation estimate of a range for the biodegradation half-life needed for the model may be obtained by dividing reported aqueous biodegradation half-life by scaling factors of 50 and 150. 相似文献
727.
Sakan S Grzetić I Dordević D 《Environmental science and pollution research international》2007,14(4):229-236
Introduction In this work, sediments of the River Tisa (Tisza) are studied to assess their environmental pollution levels for some major
heavy metals, as well as to predict the investigated elements’ mobility on the basis of their association type with the substrate.
The Tisa River catchments area is a subbasin of the River Danube. Part of this river, 166 km long, belongs to the Serbian
province of Vojvodina, before it flows into the Danube. It has been chosen for our investigation, because it has been exposed
to intense pollution in the last decades.
Materials and Methods The river sediment samples were collected at 32 locations. The proportions of sand, silt and clay fractions were determined.
The sequential extraction procedure following a modified Tessier method was applied for speciation of the metal forms in the
collected samples. The metal concentrations of Zn, Cd, Pb, Ni, Cu, Cr, Fe and Mn in extracts were determined by atomic absorption
spectroscopy.
Results and Discussion Granulometric analysis showed that some 50% of the Tisa River sediments were silt and clay, while the rest was sand with quartz,
as the main constituent. The average metal content of the surface river sediment samples for every fraction of sequential
extraction was presented and discussed in relation to pH, Eh and metal fractionation. The average metal content from the Tisa
River sediments, obtained as an average of the metal’s concentration released in all five sequential extraction fractions
was compared with: average metal contents of the Tisa River sediments in Hungary, metal content in soils formed on the Tisa
River alluvium of Vojvodina, average metal content in soils of Vojvodina, and average metal content in soils of Hungary. An
assessment of metal pollution levels in Tisa River sediments was made by comparing mean values for obtained results for the
Tisa River sediments with the freshwater sediment’s Quality Guidelines as published by US EPA, Environment Canada and soil
standards for Serbia.
Conclusion According to US EPA and Canadian Quality Guidelines for freshwater sediments, the concentration of heavy metals in Tisa sediments
were: (a) much higher than defined concentrations below which harmful effects on river biota are unlikely to be observed,
(b) below defined concentrations above which harmful effects on river biota are likely to be observed. The concentration levels
of Pb, Ni, Cu and Cr in Tisa River sediments are safe when compared with Serbian MAQ (Maximum Allowed Quantity) standards
for soils, but they are unsafe in the case of Zn and Cd.
Recommendations and Outlook The quality of sediments in the Tisa River was on the border line between potentially polluted and polluted. This line could
very easily be exceeded since the quality of sediments in the Tisa River in Hungary was already worse than in Serbia. These
results indicated the need for further monitoring of heavy metals in that locality. 相似文献
728.
Hydrogeochemistry and Groundwater Quality Assessment of Lower Part of the Ponnaiyar River Basin, Cuddalore District, South India 总被引:7,自引:0,他引:7
Jeevanandam M Kannan R Srinivasalu S Rammohan V 《Environmental monitoring and assessment》2007,132(1-3):263-274
The Lower Ponnaiyar River Basin forms an important groundwater province in South India constituted by Tertiary formations
dominated by sandstones and overlain by alluvium. The region enjoyed artesian conditions 50 years back but at present frequent
failure of monsoon and over exploitation is threatening the aquifer. Further, extensive agricultural and industrial activities
and urbanization has resulted in the increase in demand and contamination of the aquifer. To identify the sources and quality
of groundwater, water samples from 47 bore wells were collected in an area of 154 km2 and were analysed for major ions and trace metals. The results reveal that the groundwater in many places is contaminated
by higher concentrations of NO3, Cl, PO4 and Fe. Four major hydrochemical facies Ca–Mg–Cl, Na–Cl, Ca–HCO3 and Na–HCO3 were identified using Piper trilinear diagram. Salinity, sodium adsorption ratio, and sodium percentage indicate that most
of the groundwater samples are not suitable for irrigation as well as for domestic purposes and far from drinking water standards.
The most serious pollution threat to groundwater is from nitrate ions, which are associated with sewage and fertilizers application.
The present state of the quality of the lower part of Ponnaiyar River Basin is of great concern and the higher concentration
of toxic metals (Fe and Ni) may entail various health hazards. 相似文献
729.
Knowledge of the total concentration of heavy metals is not enough to fully assess the environmental impact of urban soils.
For this reason, the determination of metal speciation is important to evaluate their environment and the mobilization capacity.
Sequential extraction technique proposed by the former European Community Bureau of Reference (BCR) was used to speciate Cd,
Cu, Fe, Mn, Ni, Pb, and Zn in urban soils from Guangzhou into four operationally defined fractions: HOAc extractable, reducible,
oxidizable, and residual. The Cu, Fe, Ni, and Zn were predominately located in the residual fraction, Pb in the reducible
fraction, and Cd and Mn within the HOAc extractable fraction. The order of Cd in each fraction was generally HOAc extractable
> reducible > residual > oxidizable; Cu and Fe were residual > reducible > oxidizable > HOAc extractable; Mn was HOAc extractable
> residual > reducible > oxidizable; Ni and Zn were residual > reducible > HOAc extractable > oxidizable; and Pb was reducible
> residual > oxidizable > HOAc extractable. Cadmium was identified as being the most mobile of the elements, followed by Mn,
Zn, Ni, Cu, Pb and Fe. Iron–Mn oxides can play an important role in binding Cd, Cu, Ni, Pb, and Zn and in decreasing their
proportion associated with the residual fraction in the soils. With total concentrations of Cd, Cu, Ni, Pb, Zn, and Mn increase,
these metals more easily release and may produce more negative effects on the urban environment. 相似文献
730.
Perrino C Canepari S Cardarelli E Catrambone M Sargolini T 《Environmental monitoring and assessment》2007,128(1-3):133-151
A field study was carried out at six locations in the Lazio region (Central Italy) aimed at characterising atmospheric particulate
matter (PM10 and PM2.5) from the point of view of the chemical composition and grain size distribution of the particles, the mixing properties of
the atmosphere, the frequency and relevance of natural events. The combination of four different analytical techniques (ion
chromatography, X-ray fluorescence and ICP for inorganic components, thermo-optical analysis for carbon compounds) yielded
sound results in terms of characterisation of the air masses. During the first three months of the study (October-December
2004), many pollution events of natural (sea-salt or desert dust episodes) or anthropogenic nature were identified and characterised.
More than 90% of the collected mass was identified by chemical analysis. The central role played by the mixing properties
of the lower atmosphere when pollution events occurred was highlighted. The results show a major impact of primary anthropogenic
pollutants on traffic stations and a homogeneous distribution of secondary pollutants over the regional area. An evaluation
of the sources of PM and an identification of possible reliable tracers were obtained using a chemical fractionation procedure. 相似文献