The effect of filter material on bioaerosol collection of Bacillus subtilis spores used as a Bacillus anthracis simulant

The objective of this study was to determine filter materials and extraction methods that are appropriate to use for environmental sampling of B. anthracis. Four types of filters were tested: mixed cellulose ester (MCE) with a pore size of 3 microm, polytetrafluoroethylene (PTFE) with pore sizes of 1 and 3 microm, and gelatin with a pore size of 3 microm. Bacillus subtilis var. niger endospores (also known as Bacillus globigii[BG]) were used as a surrogate for B. anthracis. Endospores were collected into Button Inhalable Aerosol Samplers with sampling times of 15 minutes, 1 hour, and 4 hours. Physical collection efficiency was determined by measuring upstream and downstream B. subtilis concentrations with an optical particle counter. Vortexing with ultrasonic agitation and vortexing with shaker agitation extraction methods were evaluated. The MCE, 1 microm PTFE, and gelatin filters provided physical collection efficiencies of 94% or greater. The 3 microm PTFE filter showed inconsistent physical efficiency characteristics between filters. Epifluorescence microscopic analysis of the gelatin filter extraction fluid revealed the presence of contamination by non-culturable bacteria. Mean differences for microbial culturability were not statistically significant for filter materials and extraction methods. However, the vortexing with shaker agitation extraction method resulted in higher total microbial counts in the extraction fluids for MCE and 1 microm PTFE filters when compared to vortexing with ultrasonic agitation. In summary, the MCE and 1 microm PTFE filters in combination with vortexing and shaker extraction demonstrated the best performance for the filter collection and extraction of BG spores.     

Quantitative PCR analysis of house dust can reveal abnormal mold conditions

Indoor mold concentrations were measured in the dust of moldy homes (MH) and reference homes (RH) by quantitative PCR (QPCR) assays for 82 species or related groups of species (assay groups). About 70% of the species and groups were never or only rarely detected. The ratios (MH geometric mean : RH geometric mean) for 6 commonly detected species (Aspergillus ochraceus, A. penicillioides, A. unguis, A. versicolor, Eurotium group, and Cladosporium sphaerospermum) were >1 (Group I). Logistic regression analysis of the sum of the logs of the concentrations of Group I species resulted in a 95% probability for separating MH from RH. These results suggest that it may be possible to evaluate whether a home has an abnormal mold condition by quantifying a limited number of mold species in a dust sample. Also, four common species of Aspergillus were quantified by standard culturing procedures and their concentrations compared to QPCR results. Culturing underestimated the concentrations of these four species by 2 to 3 orders of magnitude compared to QPCR.     

Environmental feedbacks in temperate aquatic ecosystems under global change: why do we need to consider chemical stressors?

Regional Environmental Change - Globally increasing temperature and modifications in precipitation patterns induce major environmental alterations in aquatic ecosystems. Particularly profound...     

Effect of gaseous chlorine dioxide on indoor microbial contaminants

Traditional and modern techniques for bioaerosol enumeration were used to evaluate the relative efficiency of gaseous chlorine dioxide (ClO2) in reducing the indoor microbial contamination under field and laboratory conditions. The field study was performed in a highly microbially contaminated house, which had had an undetected roof leak for an extended period of time and exhibited large areas of visible microbial growth. Air concentrations of culturable fungi and bacteria, total fungi determined by microscopic count and polymerase chain reaction (PCR) assays, endotoxin, and (1 --> 3)-beta-D-glucan were determined before and after the house was tented and treated with ClO2. The laboratory study was designed to evaluate the efficiency of ClO2 treatment against known concentrations of spores of Aspergillus versicolor and Stachybotrys chartarum on filter paper (surrogate for surface treatment). These species are commonly found in damp indoor environments and were detected in the field study. Upon analysis of the environmental data from the treated house, it was found that the culturable bacteria and fungi as well as total count of fungi (as determined by microscopic count and PCR) were decreased at least 85% after the ClO2 application. However, microscopic analyses of tape samples collected from surfaces after treatment showed that the fungal structures were still present on surfaces. There was no statistically significant change in airborne endotoxin and (1 --> 3)-beta-D-glucan concentration in the field study. The laboratory study supported these results and showed a nonsignificant increase in the concentration of (1 --> 3)-beta-D-glucan after ClO2 treatment.     

Organic carbon causes interference with nitrate and nitrite measurements by UV/Vis spectrometers: the importance of local calibration

Compared with sporadic conventional water sampling, continuous water-quality monitoring with optical sensors has improved our understanding of freshwater dynamics. The basic principle in photometric measurements is the incident light at a given wavelength that is either reflected, scattered, or transmitted in the body of water. Here, we discuss the transmittance measurements. The amount of transmittance is inversely proportional to the concentration of the substance measured. However, the transmittance is subject to interference, because it can be affected by factors other than the substance targeted in the water. In this study, interference with the UV/Vis sensor nitrate plus nitrite measurements caused by organic carbon was evaluated. Total or dissolved organic carbon as well as nitrate plus nitrite concentrations were measured in various boreal waters with two UV/Vis sensors (5-mm and 35-mm pathlengths), using conventional laboratory analysis results as references. Organic carbon increased the sensor nitrate plus nitrite results, not only in waters with high organic carbon concentrations, but also at the lower concentrations (< 10 mg C L^?1) typical of boreal stream, river, and lake waters. Our results demonstrated that local calibration with multiple linear regression, including both nitrate plus nitrite and dissolved organic carbon, can correct the error caused by organic carbon. However, high-frequency optical sensors continue to be excellent tools for environmental monitoring when they are properly calibrated for the local water matrix.     

Performance of the Button Personal Inhalable Sampler for the measurement of outdoor aeroallergens

No personal aerosol sampler has been evaluated for monitoring aeroallergens in outdoor field conditions and compared to conventional stationary aerobiological samplers. Recently developed Button Personal Inhalable Aerosol Sampler has demonstrated high sampling efficiency for non-biological particles and low sensitivity to the wind direction and velocity. The aim of the present study was to evaluate the Button Sampler for the measurement of outdoor pollen grains and fungal spores side-by-side with the widely used Rotorod Sampler. The sampling was performed for 8 months (spring, summer and fall) at a monitoring station on the roof of a two-storied office building located in the center of the city of Cincinnati. Two identical Button Samplers, one oriented towards the most prevalent wind and the other towards the opposite wind and a Rotorod Sampler were placed side-by-side. The total fungal spore concentration ranged from 129 to 12,980 spores m(-3) (number per cubic meter of air) and the total pollen concentration from 4 to 4536 pollen m(-3). The fungal spore concentrations obtained with the two Button Samplers correlated well (r = 0.95; p<0.0001). The pollen data also showed positive correlation. These findings strongly support the results of earlier studies conducted with non-biological aerosol particles, which demonstrated a low wind dependence of the performance of the Button Sampler compared to other samplers. The Button Sampler's inlet efficiency was found to be more dependent on wind direction when sampling larger sized Pinaceae pollen grains (aerodynamic diameter approximately 65 mum). Compared to Rotorod, both Button Samplers measured significantly higher total fungal spore concentrations. For total pollen count, the Button Sampler facing the prevalent wind showed concentrations levels comparable to that of the Rotorod, but the Button Sampler oriented opposite to the prevalent wind demonstrated lower concentration levels. Overall, it was concluded that the Button Sampler is efficient for the personal sampling of outdoor aeroallergens, and is especially beneficial for aeroallergens of small particle size.     

Sulphur dioxide adsorption in Scots pine canopies exposed to high ammonia emissions near a Cu-Ni smelter in SW Finland

Since 1994 the nickel-processing plant at the Cu-Ni smelter at Harjavalta, south-west Finland, has emitted considerable amounts of NH(3) into the atmosphere. The effects of NH(3) emissions on nitrogen and sulphur deposition in throughfall and the foliar nutrient status were investigated in a Scots pine stand at 0.5 km distance. Bulk deposition, stand throughfall and percolation water (20 cm depth) samples were collected at 4-week intervals during 1992-1998. pH and the Ca, Mg, K, NH(4) and SO(4) concentrations were determined on the samples. NH(3) emissions have strongly increased the scavenging of SO(2) from the air in the pine stand, and the increased levels of N and S deposition were clearly evident as increased foliar N and S concentrations and larger needle size. The increased input of SO(4) into the forest floor was not associated with an increase in the leaching of Ca and Mg from the surface soil layers.     

Culturability and concentration of indoor and outdoor airborne fungi in six single-family homes

In this study, the culturability of indoor and outdoor airborne fungi was determined through long-term sampling (24-h) using a Button Personal Inhalable Aerosol Sampler. The air samples were collected during three seasons in six Cincinnati area homes that were free from moisture damage or visible mold. Cultivation and total microscopic enumeration methods were employed for the sample analysis. The geometric means of indoor and outdoor culturable fungal concentrations were 88 and 102 colony-forming units (CFU) m(-3), respectively, with a geometric mean of the I/O ratio equal to 0.66. Overall, 26 genera of culturable fungi were recovered from the indoor and outdoor samples. For total fungal spores, the indoor and outdoor geometric means were 211 and 605 spores m(-3), respectively, with a geometric mean of I/O ratio equal to 0.32. The identification revealed 37 fungal genera from indoor and outdoor samples based on the total spore analysis. Indoor and outdoor concentrations of culturable and total fungal spores showed significant correlations (r = 0.655, p<0.0001 and r = 0.633, p<0.0001, respectively). The indoor and outdoor median viabilities of fungi were 55% and 25%, respectively, which indicates that indoor environment provides more favorable survival conditions for the aerosolized fungi. Among the seasons, the highest indoor and outdoor culturability of fungi was observed in the fall. Cladosporium had a highest median value of culturability (38% and 33% for indoor and outdoor, respectively) followed by Aspergillus/Penicillium (9% and 2%) among predominant genera of fungi. Increased culturability of fungi inside the homes may have important implications because of the potential increase in the release of allergens from viable spores and pathogenicity of viable fungi on immunocompromised individuals.     

A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters

The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO₂) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO₂ production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO₂ production by mineralization as well as CO₂ loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of \( {0.70}_{-0.31}^{+0.27} \) to \( {1.52}_{-0.90}^{+1.09} \) Pg C yr^?1 depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO₂ sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO₂ sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.