Heidi Bauer

The contribution of bacteria and fungal spores to the organic carbon content of cloud water, precipitation and aerosols

To estimate the contribution of bacterial and fungal carbon to the carbon content of atmospheric samples, the number concentrations of bacteria and fungal spores in cloud water, snow, rain and aerosol samples collected at a continental background site in the Austrian Alps were determined. Based on these number concentrations, bacterial and fungal carbon was calculated and related to the total carbon (TC) and organic carbon (OC) contents of the samples. In cloud water samples, an average of4.5 x 10 3 spores ml -1 was found, which corresponds to 1.5% of OC. The average bacterial abundance was 2.0 × 10 4 cells ml -1 corresponding to 0.01% ofOC. In snow samples, the average concentrations of bacteria and fungi were 3.1 x 10 3 cells ml -1 corresponding to 0.015% of TC and 6.2 x 10 2 spores ml -1 corresponding to 1.8% of TC, respectively. In aerosol samples, average concentration of bacteria amounted to 1.2 x 10 4 cells m -3 , which corresponds to 0.03% of OC, while fungal concentrations averaged to 7.3 x 10 2 spores m -3 3 or 0.9% ofOC. As fungal spores occur predominantly in the size range > 2.1 μm aerodynamic equivalent diameter (a.e.d.), their contribution to the coarse size fraction (2.1-10 μm) was investigated and amounted up to 9.9% ofOC.

Aerosol chemical characteristics of a mega-city in Southeast Asia (Dhaka–Bangladesh)

Elemental carbon (EC), organic carbon (OC), organic acids, major inorganic ions and trace elements were determined in aerosol samples collected under pre-monsoon conditions (March–April 2001) in Dhaka (Bangladesh). Using the Fe content of the aerosol to reconstruct the aerosol mass from soil-type mineralic material, a mass balance of the Dhaka aerosol was achieved. From this follows that on the average around 76% of the aerosol is from soil-type material, around 18% of carbonaceous material, and around 6% soluble ions and trace elements (without iron) o0.3%. Enrichment factors (Fe as a reference element) indicated that coal fly ash is a likely main source for Cd, Pb and Zn in the Dhaka aerosol, while As appears to be of geogenic origin. Organic acids contributed only 0.72% C to OC and were much less abundant relative to OC than at European sites. The trace elements levels in Dhaka were much lower than at comparable Southeast Asian mega-cities (e.g. Lahore, Pakistan), but considerably higher than reported for European and US cities under present day conditions. The correlation between EC and OC was quite high (R 2 ¼ 0:81) indicating a potential joint source of emission for carbonaceous aerosols. The EC/total carbon (TC) and K/EC ratios indicated that biomass combustion was not a main contributor to EC in Dhaka, which implicates that fossil fuel combustion is the major contributor to EC levels in the Dhaka aerosol. The differences in the EC/TC and K/EC ratios in the three mega-cities in Southeast Asia (data available from Dhaka, Bangladesh; Lahore, Pakistan; and Mumbai, India) indicate that the aerosol source mix in Southeast Asian cities varies considerably at a national or even regional scale.

Bacteria and fungi in aerosols generated by two different types of wastewater treatment plants

Raw wastewater is a potential carrier of pathogenic microorganisms and may pose a health risk when pathogenic microorganisms become aerosolized during aeration. Two different types of wastewater treatment plants were investigated, and the amounts of cultivable bacteria and fungi were measured in the emitted aerosols. Average concentrations of 17,000 CFU m(-3) of mesophilic, 2,100 CFU m(-3) of TSA-SB bacteria (bacteria associated with certain waterborne virulence factors), 1700 CFU m(-3) of mesophilic and 45 CFU m(-3) of thermotolerant fungi, were found in the aerosol emitted by the aeration tank of the activated sludge plant. In the aerosol of the fixed-film reactor 3000 CFU m(-3) mesophilic and 730CFUm(-3) TSA-SB bacteria, and 180 CFUm(-3) mesophilic and 14 CFU m(-3) thermotolerant fungi were measured. The specific emissions per population equivalent between the two types of treatment plants differed by two orders of magnitude. The microbial flux based on the open water surface area of the two treatment plants was similar. The aerosolization ratios of cultivable bacteria (expressed as CFU m(-3) aerosol/m(-3) wastewater) ranged between 8.4 x 10(-11) and 4.9 x 10(-9). The aerosolization ratio of fungi was one to three orders of magnitude higher and a significant difference between the two types of treatment plants could be observed.

Approach for a novel control strategy for simultaneous nitrification/denitrification in activated sludge reactors

Biological nitrogen removal in activated sludge processes is conventionally obtained by a sequence of aerobic and anoxic processes. Kinetic mechanisms aAecting the oxygen balance could trigger the production of total volatile organic carbon (TVOC) and nitric oxides (NO) under anoxic and anaerobic conditions. Measurements at a wastewater treatment pilot plant of capacity 1.6 m 3 wastewater show that the amount of TVOC and NO produced during the treatment process depends on carbon loading (low feed, balanced and overloaded) and aeration conditions. To confirm the results ORP, pH and dissolved oxygen (DO) are measured on-line and chemical parameters such as nitrate (NO3-N), ammonium (NH4-N) and TOC are measured in the wastewater. The ORP observed is in the range ofˇ60 and +198 mV includes optimal setpoints for simultaneous nitrification and denitrification. From the pattern of NO emission plot, it can be assumed that a part of the produced NO3-N is denitrified during the aeration period. NO emissions are especially high during denitrification conditions at low oxygen rates. The results suggest that both NO and TVOC emission concentrations in combination with ORP can be valuable parameters to control operation of a wastewater treatment plant. Continuous measurements of ORP and NO concentrations for estimation of NO emissions gauging the extent of nitrification or denitrification in the plant becomes possible. 7 2000 Elsevier Science Ltd. All rights reserved

Indoor and outdoor atmospheric fungal spores in the São Paulo metropolitan area (Brazil): species and numeric concentrations

The aim of this study was to estimate the indoor and outdoor concentrations of fungal spores in the Metropolitan Area of Sao Paulo (MASP), collected at different sites in winter/spring and summer seasons. The techniques adopted included cultivation (samples collected with impactors) and microscopic enumeration (samples collected with impingers). The overall results showed total concentrations of fungal spores as high as 36,000 per cubic meter, with a large proportion of non culturable spores (around 91% of the total). Penicillium sp. and Aspergillus sp. were the dominant species both indoors and outdoors, in all seasons tested, occurring in more than 30% of homes at very high concentrations of culturable airborne fungi [colony forming units(CFU) m−3]. There was no significant difference between indoor and outdoor concentrations. The total fungal spore concentration found in winter was 19% higher than that in summer. Heat and humidity were the main factors affecting fungal growth; however, a non-linear response to these factors was found. Thus, temperatures below 16°C and above 25°C caused a reduction in the concentration (CFU m−3) of airborne fungi, which fits with MASP climatalogy. The same pattern was observed for humidity, although not as clearly as with temperature given the usual high relative humidity (above 70%) in the study area. These results are relevant for public health interventions that aim to reduce respiratory morbidity among susceptible populations.

Evaluation of Methods for Measuring Particulate Matter Emissions from Gas Turbines

The project SAMPLE evaluated methods for measuring particle properties in the exhaust of aircraft engines with respect to the development of standardized operation procedures for particulate matter measurement in aviation industry. Filter-based off-line mass methods included gravimetry and chemical analysis of carbonaceous species by combustion methods. Online mass methods were based on light absorption measurement or used size distribution measurements obtained from an electrical mobility analyzer approach. Number concentrations were determined using different condensation particle counters (CPC). Total mass from filter-based methods balanced gravimetric mass within 8% error. Carbonaceous matter accounted for 70% of gravimetric mass while the remaining 30% were attributed to hydrated sulfate and noncarbonaceous organic matter fractions. Online methods were closely correlated over the entire range of emission levels studied in the tests. Elemental carbon from combustion methods and black carbon from optical methods deviated by maximum 5% with respect to mass for low to medium emission levels, whereas for high emission levels a systematic deviation between online methods and filter based methods was found which is attributed to sampling effects. CPC based instruments proved highly reproducible for number concentration measurements with a maximum interinstrument standard deviation of 7.5%.

Relationship between release of nitric oxide and CO2 and their dependence on oxidation reduction potential in wastewater treatment

Nitric oxide (NO) is an intermediate of denitrification process and can be produced by denitrifiers, nitrifiers and other bacteria. In our experiments we measured the dynamic flow of NO depending on oxidation reduction potential (ORP). Different ORP-ranges were related to various carbon loading stages in the wastewater treatment pilot plant. Nitrification and denitrification were achieved by a sequence of aeration and non-aeration periods. Our measurements show that different carbon loading conditions (low feed, balanced and overloaded conditions) did not change the range of the mixing ratio of NO emissions when the aeration conditions like air-flow and temperature were kept constant. Minimum and maximum NO mixing ratios were 34.7 and 91.8 ppbv; 52.3 and 91.3 ppbv; 57.6 and 109 ppbv for low feed, balanced and overloaded conditions, respectively. The curve of the NO graph relied on nitrification/denitrification dynamics. The dependence of NO release on different ORP and CO2-release during the various conditions are shown. Longer aeration times resulted in an increased release of gaseous NO. The net-release of NO g(-1) nitrogen removed was between 0.014% and 0.028%. The NO fluxes to the air were observed between 8.3 and 14.9 mg m(-2) d(-1) NO. The major release occurred during high aeration periods whereas the concentration of dissolved [NOaq] in the wastewater was less than 0.05% of the gaseous release due to very low solubility of the NO.

Assessing Optical Properties and Refractive Index of Combustion Aerosol Particles Through Combined Experimental and Modeling Studies

The variability of optical properties of combustion particles generated from a propane diffusion flame under varying fuel-to-air (C/O) ratios was studied with a three-wavelength nephelometer, a particle soot absorption photometer, and an integrating sphere photometer. Information on particle size distribution, morphology, and elemental carbon to total carbon (EC/TC) ratios were obtained from scanning mobility particle sizer measurements, transmission electron microscopy analyses, and thermal-optical analyses. Particles generated under a low C/O ratio (0.22) showed high elemental carbon fraction (EC/TC = 0.77) and low brown carbon to equivalent black carbon (BrC/EBC) ratio (0.01), and were aggregates composed of small primary particles. Rayleigh–Debye–Gans theory reproduced experimental single-scattering albedo, ω, absorption, and scattering Ångström exponents within 56, 3, and 18%, respectively. In contrast, particles produced under a high C/O ratio (0.60) showed low elemental carbon fraction (EC/TC = 0.09) and high BrC/EBC ratio >100, and were smaller and spherical in shape. Their optical properties were better modeled with Mie theory. By minimizing the difference between calculated and measured ω and Ångström exponents, refractive indices of OC at three visible wavelengths were deduced. Contrary to the widely accepted assumption that refractive index of BC is wavelength independent, BC-rich particles exhibited absorption Ångström exponent >1.0 which implies some degree of wavelength dependence. Copyright 2015 American Association for Aerosol Research

HYDROCARBONS EMISSIONS FROM A MUNICIPAL WASTEWATER TREATMENT PILOT PLANT IN VIENNA

Hydrocarbons emissions were measured from an aerationtank of a municipal wastewater treatment pilot plant. The collected off-gas samples werecharacterised for C2–C7 hydrocarbons usingGC-FID analytical technique while the total volatileorganic compounds (TVOC) were measured using acontinuous hydrocarbon gas analyser. Approximately,the estimated emission rates for 1 m3 of wastewaterfrom this aeration tank were 5 mgC of C2–C7hydrocarbons, and an average of 7 gC of TVOC. Withexception to toluene, all other measured hydrocarbonsare emitted less than 1 mgC day-1. The results supportthe view that a significant reduction in annualemissions of hydrocarbons from wastewater treatmentplants in Vienna has taken place.

Improved source assessment of Si, Al and related mineral components to PM10 based on a daily sampling procedure.

Samples obtained from an industrialized valley in the East Alpine region were collected daily for a half year and analyzed using X-ray fluorescence to examine the elements Si, Al, Fe, Ca, Mg, Na, K, Zn, P, S and Cl. Some factors affecting the changes of these elements were considered, including time, elemental correlations, weekday, weekend and seasonal changes. Diagnostic analysis provided an insight into a decoupling behavior that occursin siliceous and carbonates minerals. A decrease in Si and Al and an increase in carbonates, Na, K, Zn and P were observed during the cold season. However, a consistently high correlation of Si and Al was observed in all seasons. It was established that such high levels originated from street surface abrasion. The increase in variability and absolute levels of carbonates during the cold season was demonstrated by adding carbonates to the street surface as gritting material to increase the grip on snowy surfaces. A marked increase in Na and Cl was observed in winter which may have been caused by thaw salt that is widely used in winter in Austria. This was associated with a significant increase in K, Zn, and P in the cold season that was the result of domestic space heating with wood. PM10 levels in December were 12 microg/m3 and were higher than levels detected in July. It was established that such high levels originated from mineral oxides, wood smoke, and inorganic ionic material(s).