Development of a variable configuration cascade impactor for aerosol size distribution measurement

In atmospheric aerosol studies, it is often required to use two different impactors, namely, the normal pressure and the low-pressure impactor, to measure the mass-size distribution over a wide size range. From the perspective of rendering the system compact for such measurements, it may be more advantageous to combine the two features in a single instrument. In an effort towards exploring this option, a variable configuration cascade impactor (VCCI) comprising of 7 normal pressure and 4 low-pressure stages has been designed and developed. In configuration-1, it operates as a low-pressure impactor, with a sampling flow rate of 10 L min^?1 and classifies the particles from 0.1 to 21 μm in eleven size classes. In configuration-2, it operates as a normal pressure impactor, with a sampling flow rate of 45 L min^?1, and classifies the particles from 0.53 to 10 μm in seven size classes. As part of performance evaluation of the system, the deposit patterns and the integral performance have been studied. For integral performance, a comparative mass-size distribution measurement between VCCI and standard Andersen impactor was carried out. Its performance was also evaluated against the GRIMM Scanning Mobility Particle Sizer (SMPS) in the common size range of both these instruments and against GRIMM Optical Particle Counter (OPC). In addition to this, VCCI was evaluated for its performance in the PM_x configuration obtained by removing a few of the impactor stages sequentially and measuring corresponding size distribution for every stage removed. Changes in the distribution parameters due to spillover of the deposits of previous stage to remaining stages were within 10%. This variation is well within the generally accepted value for all environmental measurement related applications.     

A comparative study for the sorption of Cd(II) by K-feldspar and sepiolite as soil components, and the recovery of Cd(II) using rhamnolipid biosurfactant

This study investigated the sorption characteristics and recovery of selected heavy metal Cd(II) from K-feldspar and sepiolite, representative soil components, using rhamnolipid biosurfactant. Although the proposed technique was classified as a soil bioremediation process, it can also be applied to treatment of waste waters containing Cd(II) ions with minor modifications. The effect of initial Cd(II) concentration on sorption capacity was characterized by determining the sorption isotherms. Of the four models examined, the Freundlich model showed the best fit for the sorption of Cd(II) on K-feldspar, whereas the Langmuir-model was used successfully to characterize the sorption of Cd(II) on sepiolite. Although a high Cd(II) uptake of 7.49 mmol/kg by K-feldspar was obtained, sepiolite was a superior Cd(II) accumulater, with a maximum Cd(II) uptake of 24.66 mmol Cd(II)/kg. The presence of Cd(II) in the sepiolite or K-feldspar prior to addition of the rhamnolipid generally resulted in less rhamnolipid sorption to sepiolite or K-feldspar. The maximum Cd(II) desorption efficiency by rhamnolipid from K-feldspar was substantially higher than that of sepiolite and determined to be 96% of the sorbed Cd(II), whereas only 10.1% of the sorbed Cd(II) from sepiolite was recovered by rhamnolipid solution.     

Demolish it and They Will Come: Estimating the Economic Impacts of Restoring a Recreational Fishery1

Abstract: This paper presents the results of an ex post survey of recreational anglers for the lower Kennebec River, post‐Edwards Dam removal. To the best of our knowledge, this study represents one of the first ex post analyses of fisheries restoration from dam removal. We find significant benefits have accrued to anglers using the restored fishery. Specifically, anglers are spending more to visit the fishery, a direct indication of the increased value anglers place on the improved fishery. Anglers are also willing to pay for increased angling opportunities on the river. These findings have policy implications for other privately owned dams that are currently undergoing relicensing and/or dam removal considerations. Our findings may also hold implications for fisheries that have deteriorated due to historic dam construction.     

Bio-syngas production with low concentrations of CO2 and CH4 from microwave-induced pyrolysis of wet and dried sewage sludge

This paper assesses the feasibility of producing syngas from sewage sludge via two pyrolysis processes: microwave-induced pyrolysis (MWP) and conventional pyrolysis (CP). The changes in the composition of the produced gas as a function of the pyrolysis treatment and the initial moisture content of the sludge were evaluated. It was found that MWP produced a gas with a higher concentration of syngas than CP, reaching values of up to 94vol%. Moreover, this gas showed a CO2 and CH4 concentration around 50% and 70%, respectively, lower than that obtained in the gas from CP. With respect to the effect of moisture on gas composition, this was more pronounced in CP than in MWP. Thus, the presence of moisture increases the concentration of H2 and CO2 and decreases that of CO, especially when CP was used. In order to elucidate the behaviour of CO2 during the pyrolysis, the CO2 gasification kinetics of the char obtained from the pyrolysis were investigated. It was established that in microwave heating the gasification reaction is much more favoured than in conventional heating. Therefore, the low concentration of CO2 and the high concentration of CO in the microwave pyrolysis gas could be due to the self-gasification of the residue by the CO2 produced during the devolatilization of the sewage sludge in the pyrolysis process.     

Theoretical study on the chemical properties of polybrominated diphenyl ethers

Density functional theory calculations at the B3LYP/6-31+G(d) and B3LYP/aug-cc-pVDZ levels were performed to obtain the equilibrium structures, thermodynamic properties, and electron affinities (EA) of 14 polybrominated diphenyl ether (PBDE) congeners in the gas phase. All congeners except for those of symmetric BDE are found to have two or more conformational isomers. The optimized geometries of the most stable conformational isomers are in agreement with recently published X-ray crystallographic data. The thermodynamic properties of the congeners with a given number of bromine substitutions are strongly dependent on the substitution pattern, whereas the EA values also depend on the number of bromine substitutions. The vertical electron affinities (EA(Ver)) calculated for the selected BDE congeners at the B3LYP/aug-cc-pVDZ level are all positive except for di-BDEs, and are correlated with the initial reductive debromination rate constants obtained recently [Keum, Y.-S., Li, Q.X., 2005. Reductive debromination of polybrominated diphenyl ethers by zerovalent iron. Environ. Sci. Technol. 39, 2280]. All adiabatic electron affinities (EA(Ada)) are positive, and suggest that the BDE congeners act as electron acceptors when reacting with receptors in living cells. The calculated EA(Ada) values differ considerably from those of EA(Ver) because of the large geometrical relaxation from the neutral to the anionic BDE congeners, highlighted by the lengthening of a C-Br bond. The elongated C-Br bond, which occurs at the alpha position, is directly involved in the debromination of n-bromodiphenyl to (n-1)-bromodiphenyl ethers in the reductive debromination experiments.     

Application of biofiltration system on AOC removal: column and field studies

The Cheng-Ching Lake Water Treatment Plant (CCLWTP) is the main supplier of domestic water for the Greater Kaohsiung area, the second largest metropolis in Taiwan. Biological activated carbon (BAC) filtration is one of the major treatment processes in CCLWTP. The objectives of this study were to evaluate the effectiveness of BAC filtration on water treatment in the studied advanced water treatment plant and its capability on pollutants [e.g., AOC (assimilable organic carbon), bromide, bromate, iron] removal. In this study, water samples from each treatment process of CCLWTP were collected and analyzed periodically to assess the variations in concentrations of AOC and other water quality indicators after each treatment unit. Moreover, the efficiency of biofiltration process using granular activated carbon (GAC) and anthracite as the fillers was also evaluated through a column experiment. Results show that the removal efficiencies for AOC, bromide, bromate, and iron are 86% 100%, 17%, and 30% after the BAC filter bed, respectively. This indicates that BAC filtration plays an important role in pollutant removal. Results also show that AOC concentrations in raw water and effluent of the CCLWTP are approximately 143 and 16 microg acetate-Cl(-1), respectively. This reveals that the treatment processes applied in CCLWTP is able to remove AOC effectively. Results of column study show that the AOC removal efficiencies in the GAC and anthracite columns are 60% and 17%, respectively. Microbial colonization on GAC and anthracite were detected via the observation of scanning electron microscopic images. The observed microorganisms included bacteria (rods, cocci, and filamentous bacteria), fungi, and protozoa. Results from this study provide us insight into the mechanisms of AOC removal by advanced water treatment processes. These findings would be helpful in designing a modified water treatment system for AOC removal and water quality improvement.     

Changes in persistent contaminant concentration and CYP1A1 protein expression in biopsy samples from northern bottlenose whales, Hyperoodon ampullatus, following the onset of nearby oil and gas development

A small population of endangered northern bottlenose whales (Hyperoodon ampullatus) inhabits "The Gully" a Marine Protected Area on the Scotian Shelf, eastern Canada. Amid concerns regarding nearby oil and gas development, we took 36 skin and blubber biopsy samples in 1996-1997 (prior to major development) and 2002-2003 (five years after development began), and three samples from a population in the Davis Strait, Labrador in 2003. These were analysed for cytochrome P4501A1 (CYP1A1) protein expression (n=36), and for persistent contaminants (n=23). CYP1A1 showed generally low expression in whales from The Gully, but higher levels during 2003, potentially coincident with recorded oil spills, and higher levels in Davis Strait whales. A range of PCB congeners and organochlorine compounds were detected, with concentrations similar to other North Atlantic odontocetes. Concentrations were higher in whales from The Gully than from the Davis Strait, with significant increases in 4,4'-DDE and trans-nonachlor in 2002-2003 relative to 1996-1997.     

Bulk deposition of polycyclic aromatic hydrocarbons (PAHs) in an industrial site of Turkey

Ambient air and deposition samples were collected in the period of July 2004-May 2005 in an industrial district of Bursa, Turkey and analyzed for polycyclic aromatic hydrocarbon (PAH) compounds. The overall average of fourteen bulk deposition fluxes for PAHs was 3300+/-5100 ng m(-2) d(-1). PAH depositions showed a seasonal variation and they were higher in winter months. This was probably due to increases in residential heating activities and decreases in atmospheric mixing layer levels. Ambient air samples, measured with a high volume air sampler, were collected from the same site. The average total concentration including gas and particulate phase was about 300+/-420 ng m(-3) and it was in the range of previously reported values. Some of the ambient air and bulk deposition samples were collected simultaneously in dry periods. Both concurrently measured values were used to calculate the dry deposition velocities whose overall average value was 0.45+/-0.35 cm s(-1).     

Feasibility of phytoextraction to remediate cadmium and zinc contaminated soils

A Cd and Zn contaminated soil was mixed and equilibrated with an uncontaminated, but otherwise similar soil to establish a gradient in soil contamination levels. Growth of Thlaspi caerulescens (Ganges ecotype) significantly decreased the metal concentrations in soil solution. Plant uptake of Cd and Zn exceeded the decrease of the soluble metal concentrations by several orders of magnitude. Hence, desorption of metals must have occurred to maintain the soil solution concentrations. A coupled regression model was developed to describe the transfer of metals from soil to solution and plant shoots. This model was applied to estimate the phytoextraction duration required to decrease the soil Cd concentration from 10 to 0.5 mg kg⁻¹. A biomass production of 1 and 5 t dm ha⁻¹ yr⁻¹ yields a duration of 42 and 11 yr, respectively. Successful phytoextraction operations based on T. caerulescens require an increased biomass production.