Transport of atmospheric fine particulate matter: part 2--findings from recent field programs on the intraurban variability in fine particulate matter

Air quality field data, collected as part of the fine particulate matter Supersites Program and other field measurements programs, have been used to assess the degree of intraurban variability for various physical and chemical properties of ambient fine particulate matter. Spatial patterns vary from nearly homogeneous to quite heterogeneous, depending on the city, parameter of interest, and the approach or method used to define spatial variability. Secondary formation, which is often regional in nature, drives fine particulate matter mass and the relevant chemical components toward high intraurban spatial homogeneity. Those particulate matter components that are dominated by primary emissions within the urban area, such as black carbon and several trace elements, tend to exhibit greater spatial heterogeneity. A variety of study designs and data analysis approaches have been used to characterize intraurban variability. High temporal correlation does not imply spatial homogeneity. For example, there can be high temporal correlation but with spatial heterogeneity manifested as smooth spatial gradients, often emanating from areas of high emissions such as the urban core or industrial zones.     

Development and application of long-term sublethal whole sediment tests with Arenicola marina and Corophium volutator using Ivermectin as the test compound

Short-term whole sediment tests using the amphipod Corophium volutator and the polychaete Arenicola marina are now routinely used in Europe to assess the acute toxicity of marine sediments. However, there is still a need to develop longer-term assays which measure effects on sublethal endpoints that are more relevant to predicting impacts at the population level. The effect of increasing exposure times and measuring additional endpoints such as growth, on the sensitivity of these assays was investigated. The test compound used was the chemotherapeutant Ivermectin (IVM), used in aquaculture to treat sea lice infestations. IVM was found to be acutely toxic to both test organisms. Extending the lugworm test to 100 days increased sensitivity of survival by a factor of three; a significant reduction in casting rate was observed at concentrations an order of magnitude lower. This assay shows potential for detecting the sublethal effects of low concentrations of sediment contaminants. Increasing the exposure time did not seem to affect the sensitivity of the amphipod, but further method development is required.     

Comparative effect of thymol or its glucose conjugate,thymol-β-d-glucopyranoside,on Campylobacter in avian gut contents

Campylobacter jejuni is an important human food-borne pathogen that can contaminate meat and poultry during processing. Consequently, strategies are sought to reduce the carriage of C. jejuni in food animals before they arrive at the abattoir. Thymol is a natural product that reduces survivability of Campylobacter in vitro, but its rapid absorption from the proximal alimentary tract limits its bactericidal efficacy in vivo. Thymol-β-d-glucopyranoside is more resistant to absorption than free thymol, but its administration to chickens has not been reported. In the present studies, 1 mM thymol-β-d-glucopyranoside was shown to exhibit near equal anti-Campylobacter activity as 1 mM thymol when incubated anaerobically in avian crop or cecal contents in vitro, resulting in reductions of 1.10–2.32 log₁₀ colony forming units mL^?1 in C. jejuni concentrations after 24 h incubation. In a follow-up live animal study, oral administration of thymol-β-d-glucopyranoside, but not free thymol, significantly lowered (>10-fold) recovery of Campylobacter from the crop of market-aged broilers when compared to placebo-treated controls (n = 6 broilers/treatment). Neither thymol-β-d-glucopyranoside nor thymol affected recovery of Campylobacter from cecal contents of the treated broilers. These results indicate that rapid absorption or passage of free thymol from the crop precluded its anti-Campylobacter activity at this site and throughout the entire gastrointestinal tract. Conversely, lower recovery of Campylobacter from the crop of birds treated with thymol-β-d-glucopyranoside indicates this conjugate was retained and able to be hydrolyzed to biologically active free thymol at this site as intended, yet was not sufficiently protected to allow passage of efficacious amounts of the intact glycoside to the lower gut. Nevertheless, these results warrant further research to see if higher doses or encapsulation of thymol-β-d-glucopyranoside or similar glycosides may yield an efficacious additive to reduce carriage of Campylobacter as well as other pathogens throughout the avian gut.     

Spatial Variation in Acidic Sulfate and Ammonia Concentrations within Metropolitan Philadelphia

Abstract

Acidic sulfate concentrations were measured in metropolitan Philadelphia during the summers of 1992 and 1993, as part of a continuing effort to characterize particle concentrations in urban environments. Sampling was performed simultaneously at eight sites located within and around metropolitan Philadelphia. Sites were selected based on their population density and on their distance and direction from the city center. Air pollution sampling was conducted every other day during the summer of 1992 and every day during the summer of 1993. All samples were collected for 24-h periods beginning at 9 a.m. (EDT). All acidic sulfate and ammonia samples were collected using modified Harvard-EPA Annular Denuder Systems (HEADS).

In this paper, we examine the spatial variation in acidic sulfate and ammonia concentrations within the metropolitan Philadelphia area. We also identify factors that may influence their variation and develop models to predict their concentrations. Outdoor sulfate (SO₄ ^2?) concentrations were uniform within metropolitan Philadelphia; however, aerosol strong acidity (H⁺) concentrations varied spatially. This variation generally was independent of wind direction, but was related to local factors, such as the NH₃ concentration, population density, and distance from the center of the city. Physico-chemical models, which were developed using data collected during the summer of 1992, were excellent predictors of 24-h and mean summertime H⁺ concentrations measured during the summer of 1993. Models accounted for 78% of the variation in 24-h H⁺ levels. Results suggest that a single stationary ambient (SAM) monitor would be sufficient to estimate SO₄ ^2? exposures for populations living in Philadelphia. For H⁺, however, multiple monitoring sites or models should be used to determine the outdoor H+ exposures of populations living in urban environments, although a single SAM site may provide an excellent index of H⁺ variation over time.     

Method Comparisons for Particulate Nitrate,Elemental Carbon,and PM2.5 Mass in Seven U.S. Cities

ABSTRACT

Methods that measure PM₂₅ mass, total particulate NO₃ ^-, and elemental carbon (EC) were evaluated in seven U.S. cities from 1997 to 1999. Sampling was performed in Bakersfield, CA; Boston, MA; Chicago, IL; Dallas, TX; Philadelphia, PA; Phoenix, AZ; and Riverside, CA. Evaluating and validating methods that measure the components of fine mass are important to the effort of establishing a speciation-monitoring network. The Harvard Impactor (HI), which measures fine particle mass, showed excellent agreement (r² = 0.99) with the PM₂₅ Federal Reference Method (FRM) for 81 24-hr samples in Riverside and Bakersfield. The HI also showed good precision (4.8%) for 243 24-hr collocated samples over eight studies.

The Aethalometer was employed in six of the sampling locations to measure black carbon (BC). These values were compared to EC as measured from a quartz filter using thermal analysis. For the six cities combined, the two methods were highly correlated (r² = 0.94; 187 24-hr samples); however, the BC values were approximately 24% less than the EC measurements consistently across all six cites. This compares well to results observed for EC/BC measurements observed in other semi-urban areas. Par-ticulate NO₃ ^- was measured using the Harvard-EPA Annular Denuder System (HEADS). This was compared to the NO₃ ^- measured from the HI Teflon (DuPont) filter to assess NO₃ ^- artifacts. Significant NO₃ ^- losses (approximately 50% of total NO₃ ^-) were found in Riverside, Philadelphia, and Boston, while minimal artifacts were observed in the other sites. Two types of HEADS configurations were employed in five cities. One system used a Na₂CO₃-coated glass fiber filter, and the other type used a nylon filter to collect volatilized NO₃ ^- from the Teflon filter. The HEADS with the Na₂CO₃-coated filter consistently underestimated the total particulate NO₃ ^- by approximately 20% compared to the nylon HEADS.     

Canada’s Mobile Sources Air Pollution Control Program

The chemical and optical properties of particle emissions from onroad vehicles were investigated at the Allegheny Tunnel on the Pennsylvania Turnpike during July 1981. The optical results are in agreement with earlier data: (1) in terms of light extinction per km driven, diesel particle emissions are at least an order of magnitude more important than particle emissions from spark-ignition vehicles; (2) for diesel particle emissions, light absorption is about twice as efficient as light scattering. Chemical analyses showed that: (1) 24% of the vehicle aerosol was extractable material, (2) 75% of the total mass was carbon, (3) 55% of the total mass was unextractable (elemental) carbon, and (4) the stoichiometry of the extractable fraction of the diesel particle emissions was C_nH_t.7nN_0.05n , i.e., the extractable material was composed predominantly of alkanes. The results of the chemical analyses allow the calculation of the massspecific light absorption coefficient for the elemental carbon component of the diesel particle emissions, i.e., 10.9 ± 1.8 m²/g (500 nm).     

一种改进的多学习教与学优化算法

针对传统教与学算法在解决复杂多峰函数优化问题时,具有局部最优且搜索开发能力较差的缺点,提出了一种改进的多学习教与学优化算法,新算法为学员的每一维加入不同的教学因子,设计了基于学员均值比较的教师选择策略和向教师及学员学习的多学习策略。基于多个单峰和多峰函数的仿真结果表明,新算法跟传统的、改进的教与学算法相比,在稳定性、寻优精度和收敛速度方面更具优势。     

Inactivation of fungi associated with barley grain by gaseous ozone

The use of gaseous ozone as a fungicide to preserve stored barley was studied. The effects of the following operating parameters on the fungicidal efficacy of ozone were examined: 1) the applied ozone dose, 2) ozonation time, 3) water activity of barley, and 4) temperature of barley. The effect of ozonation on germination of barley was also investigated. The experimental results showed that ozone was very effective in inactivation of fungi associated with the barley regardless of whether the fungi were in the forms of spores or mycelia. However, the mycelia were less resistant to ozone. With 5 minutes of ozonation, 96% of inactivation were achieved for spores as well as for mixtures of spores and small amount of mycelia by applying 0.16 and 0.10 mg of ozone/(g barley) x min, respectively. In addition, for sealed storage silos, inactivation of fungi continued when the ozone-containing gas was held inside the silos following a continuous ozone supply. The experimental results also revealed that increases in water activity and temperature of barley enhanced the fungicidal efficacy of ozone. Results of this study also indicated that the inactivation processes could be controlled by simply monitoring the exit ozone from the reactor instead of performing the time-consuming microbial examination. This finding would make the application of ozone in the preservation of cereal grains easier, simpler, and more practically applicable. The experimental results demonstrated that although ozonation above certain strength may reduce barley germination, inactivation of fungi was achieved with ozonation strengths far below the critical point.     

An empirical relationship between PM(2.5) and aerosol optical depth in Delhi Metropolitan

Atmospheric remote sensing offers a unique opportunity to compute indirect estimates of air quality, which are critically important for the management and surveillance of air quality in megacities of developing countries, particularly in India and China, which have experienced elevated concentration of air pollution but lack adequate spatial-temporal coverage of air pollution monitoring. This article examines the relationship between aerosol optical depth (AOD) estimated from satellite data at 5 km spatial resolution and the mass of fine particles ≤2.5 μm in aerodynamic diameter (PM(2.5)) monitored on the ground in Delhi Metropolitan where a series of environmental laws have been instituted in recent years.PM(2.5) monitored at 113 sites were collocated by time and space with the AOD computed using the data from Moderate Resolution Imaging Spectroradiometer (MODIS onboard the Terra satellite). MODIS data were acquired from NASA's Goddard Space Flight Center Earth Sciences Distributed Active Archive Center (DAAC). Our analysis shows a significant positive association between AOD and PM(2.5). After controlling for weather conditions, a 1% change in AOD explains 0.52±0.202% and 0.39±0.15% change in PM(2.5) monitored within ±45 and 150 min intervals of AOD data. This relationship will be used to estimate air quality surface for previous years, which will allow us to examine the time-space dynamics of air pollution in Delhi following recent air quality regulations, and to assess exposure to air pollution before and after the regulations and its impact on health.     

Soil microbial response to waste potassium silicate drilling fluid

Potassium silicate drilling fluids (PSDF) are a waste product of the oil and gas industry with potential for use in land reclamation. Few studies have examined the influence of PSDF on abundance and composition of soil bacteria and fungi. Soils from three representative locations for PSDF application in Alberta, Canada, with clay loam, loam and sand textures were studied with applications of unused, used once and used twice PSDF. For all three soils, applying ≥ 40 m³/ha of used PSDF significantly affected the existing soil microbial flora. No microbiota was detected in unused PSDF without soil. Adding used PSDF to soil significantly increased total fungal and aerobic bacterial colony forming units in dilution plate counts, and anaerobic denitrifying bacteria numbers in serial growth experiments. Used PSDF altered bacterial and fungal colony forming unit ratios of all three soils.