Chemical compositions and source identification of PM₂.₅ aerosols for estimation of a diesel source surrogate

Exposure to traffic-related pollution during childhood has been associated with asthma exacerbation, and asthma incidence. The objective of the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS) is to determine if the development of allergic and respiratory disease is associated with exposure to diesel engine exhaust particles. A detailed receptor model analyses was undertaken by applying positive matrix factorization (PMF) and UNMIX receptor models to two PM_2.5 data sets: one consisting of two carbon fractions and the other of eight temperature-resolved carbon fractions. Based on the source profiles resolved from the analyses, markers of traffic-related air pollution were estimated: the elemental carbon attributed to traffic (ECAT) and elemental carbon attributed to diesel vehicle emission (ECAD).Application of UNMIX to the two data sets generated four source factors: combustion related sulfate, traffic, metal processing and soil/crustal. The PMF application generated six source factors derived from analyzing two carbon fractions and seven factors from temperature-resolved eight carbon fractions. The source factors (with source contribution estimates by mass concentrations in parentheses) are: combustion sulfate (46.8%), vegetative burning (15.8%), secondary sulfate (12.9%), diesel vehicle emission (10.9%), metal processing (7.5%), gasoline vehicle emission (5.6%) and soil/crustal (0.7%). Diesel and gasoline vehicle emission sources were separated using eight temperature-resolved organic and elemental carbon fractions. Application of PMF to both datasets also differentiated the sulfate rich source from the vegetative burning source, which are combined in a single factor by UNMIX modeling. Calculated ECAT and ECAD values at different locations indicated that traffic source impacts depend on factors such as traffic volumes, meteorological parameters, and the mode of vehicle operation apart from the proximity of the sites to highways. The difference in ECAT and ECAD, however, was less than one standard deviation. Thus, a cost benefit consideration should be used when deciding on the benefits of an eight or two carbon approach.     

The individual response of saline lakes to a severe drought

A severe protracted drought between 1997 and 2009 has altered the physical and chemical hydrology of a series of lakes in the Corangamite Basin of southeast Australia. Leading up to the drying out of most lakes (many for the first time on record), we document the changes in lakes' water quantity (water levels and inundation), salinity (Cl concentrations), salinity processes (Cl/Br ratios), nutrient concentrations and ratios (ammonia, phosphate and NOx (nitrate and nitrite)) and algae (as chlorophyll-a) for six lakes. All lakes show record declines in inundated areas and increases in salinity from pre-drought (< 1997) to drought conditions. However, the magnitude of change in salinity varies for different lakes, and there is no systematic change in the controls on lake salinity processes. Four lakes show no change in salinity processes, one lake shows the beginnings of change; where halite dissolution reactions increased closer to the time of the lake drying up, and another lake shows a marked shift from predominantly evaporation to the cyclic dissolution and precipitation of halite. Changes in filterable reactive phosphorus (FRP) values and lake N and P limitation predictions also showed little systematic correlation with changes in lake salinity, and nutrient values varied between lakes and over time. The decline in NO_x concentrations in lakes where electrical conductivity (EC) values were above 100 mS/cm indicates some correlation with changes in salinity. Largely, these lakes exhibit individual changes in water quality parameters and salinity processes in response to the drought, indicating that while the stress of drought is regional, the hydrochemical response is local. In future changing climates, these results suggest that the catchment adaption strategies will require comprehensive plans for individual lake systems.     

Demonstration of the conditions conducive to agglomeration of zinc calcine in fluidized bed roasters

Agglomeration in the fluidized bed roasting of zinc sulphide concentrate was investigated in a continuous pilot-scale fluidized bed roaster. Alone or together, low stoichiometric excess oxygen (<10%) and high temperature (>940 °C) contributed most significantly to agglomeration of zinc calcine particles. Only one test – with 0% excess oxygen at 940 °C – led to severe agglomeration and subsequent defluidisation. Neither large initial particle size nor low gas superficial velocity promoted agglomeration as much as the combination of low stoichiometric excess oxygen and high temperature.Lead sulphide, a common impurity in zinc sulphide concentrate, also appeared to have played a key role in agglomeration. Both low excess oxygen and high temperature favoured a high partial pressure of sublimated lead sulphide. Upon contact with oxygen, lead sulphide oxidised to lead oxide, which then precipitated as a liquid onto the rather inert bed particles. As a liquid, lead oxide formed coatings that caused small particles to adhere to larger ones, as well as liquid bridges that bound particles together.     

Are theoretical consultants needed?

Comments on the article by B. D. Slife and R. N. Williams (see record 84-17550) concerning theoretical psychology as a subdiscipline of psychology. The authors agree that important philosophical and metatheoretical issues confront psychology and that greater training in these areas is needed at the doctoral level; however, they do not agree with the negative assessment of positivism nor with the recommendation that specially trained theoreticians should serve as consultants in psychology departments. It is believed that the content of the proposal was vague and the use of the term theory is confusing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Les caractéristiques psychosociales associées à la solitude chez les personnes agées, selon le type d'habitat.

The initial phase of the present research verifies whether there is any difference in the degree of loneliness between elderly persons living in the community (house, apartment for the general population) compared to those living in reserved housing (institution, boarding-house, apartment for the elderly). However, the fundamental objective is to determine the social psychological characteristics associated with loneliness for the elderly living in the community or in reserved housing. Two hundred (200) elderly persons of the metropolitan Quebec region (104: community; 96: reserved housing) responded to two questionnaires concerning their loneliness and their social psychological characteristics. There is no significant difference between the degrees of loneliness either according to the type of housing (community and reserved) or according to the sub-type of housing. Several correlations were found to be significant between loneliness and social psychological characteristics for one or the other of the two types of housing. The results are discussed in the light of previous empirical studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversible thermal behavior of the layered double hydroxides (LDHs) of Mg with Ga and In

The layered double hydroxides (LDHs) of Mg with Ga and In decompose completely on heating to 500 °C to yield poorly ordered oxide residues. In the Mg-Ga system, the oxide residue has a rock-salt structure with Ga incorporated in the MgO matrix. In the Mg-In system, the oxide residue is X-ray amorphous. These oxide residues revert back to the original LDH either on standing in a water-saturated atmosphere or on hydrothermal treatment in a Na₂CO₃ solution. In contrast, the LDHs of Co with Ga and In yield the thermodynamically stable spinel oxides and the decomposition is irreversible. These results have implications for the synthesis of ‘oxide’ catalysts by thermal decomposition of the LDHs.     

The ventilator: selection of mechanical ventilators

A comprehensive ventilator selection process can be a time-consuming and an overwhelming task. The needs assessment becomes the primary driving tool in the design of the selection process. From the needs assessment, the evaluation can be planned and organized according to the facility requirements, time constraints, and resources. The strategy can expand to an extensive project or have a succinct and condensed design. The needs assessment determines the criteria for the selection, whether it be cost, ventilator specifications, educational needs, manufacturer support needs, maintenance requirements, accessory items, or combinations of any item. Once the data have been collected, it must be analyzed and critiqued. How this examination is performed can be expansive or scaled down according to the facility's resources. Important items in the selection must be maintained and used more extensively in the decision, whereas less important items take a backseat in the operation. The final selection comes from the culmination of the entire process.     

Charge distribution around a rising bubble in a two-dimensional fluidized bed by signal reconstruction

A signal reconstruction technique was developed recently to measure the electrostatic charge density distribution surrounding a bubble rising in a two-dimensional gas-solid fluidized bed using four induction probes flush with the outside wall of a two-dimensional fluidized bed and connected to charge amplifiers for recording induced charge signals as bubbles pass by the probes. The model was implemented in Visual FORTRAN using the LSGRR Subroutine to invert the matrix for the signal reconstruction. However, if the matrix was mathematically singular or ill-conditioned, a least-squares routine or the singular value decomposition routine provided had to be used to give approximate results. If the dimension of the matrix exceeds the permissible limit, or the number of pixels is much larger than the number of measurements, the matrix cannot be inverted using the LSGRR subroutine.This paper shows that an iterative linear back projection algorithm (LBP), often used in linear tomography, can be applied to improve the reconstruction resolution of the charge distribution around rising single bubbles in a gas-solid fluidized bed. The experimentally measured induced charges from four induction probes were then applied to reconstruct the real charge distribution around a single rising gas bubble injected in a two-dimensional column as it passed the probes. The results reconstructed using the LBP method are found to be smoother and more accurate than those obtained from the LSGRR subroutine.