Detection Of Biological Aerosols Research Articles

Outdoor environmental sensitivity test for the detection of biological aerosols

A real-time light-emitting-diode-induced fluorescence biological aerosol detection method is developed that enables real-time monitoring of airborne particles derived from organisms so the presence of these contaminants can be identified. To characterize the performance, a variety of background measurements describing different contamination levels and particulate concentrations controlled to closed environments were obtained and used as the input to a detection algorithm. Optimization was performed for various backgrounds. Additionally, detection performance per sensitivity level was determined using a confusion matrix so that the user can select sensitivities depending on the background. For 50 to 100 agent-containing-particles-per-liter-of-air target detection performance, an alarm rate of 100% was achieved, and the false-alarm rate was optimized to 0%. Applying these settings, the final sensitivities of the “high” and “low” modes were roughly twice and half of those of the “normal” mode, respectively. The final alarm thresholds of high and low sensitivities were set to 0.1 times and 10 times the reference values, respectively, enabling reliable operation in a variety of situations.

Investigation of detecting biological aerosol by passive Fourier transform infrared spectroscopy technology based on MODTRAN model

The problem of detecting the biological aerosol at low elevation angle is analyzed and discussed by using MODTRAN model. First of all, the atmospheric model and profile of MODTRAN model are introduced for the biological aerosol detection by Fourier transform infrared (FTIR) spectroscopy. According to the passive detection of biological aerosol by FTIR spectroscopy, the radiation brightness difference L between the background and the target biological aerosol is calculated by using the radiative transfer theory and the simplest three-layer model. The signal value 2Lt under the actual circumstance is derived from the derivative of L combined with the noise equivalent spectral radiance value of the spectrometer. Finally, the detection limit of biological aerosol for each atmospheric mode is predicted with the passive remote sensing method. The limit concentration of detection for each atmospheric mode is different due to the differences in boundary layer temperature, transmittance, and background radiation brightness of atmospheric model, and it is also related to the absorption coefficient of biological aerosol. It is shown that the passive remote sensing of FTIR technology can detect the presence of the biological aerosol. Therefore, the detection of the biological aerosol is feasible. It presents a method of detecting the biological aerosol cloud under the actual circumstance.

Алгоритм обнаружения биологических аэрозолей в воздухе при наличии тестовых данных

Алгоритм обнаружения биологических аэрозолей в воздухе при наличии тестовых данных

Passive Detection of Biological Aerosols in the Atmosphere with a Fourier Transform Instrument (FTIR)—the Results of the Measurements in the Laboratory and in the Field

Fourier Transform Infrared Radiation (FTIR) spectroscopy is one of the most powerful methods for the detection of gaseous constituents, aerosols, and dust in planetary atmospheres. Infrared spectroscopy plays an important role in searching for biomarkers, organics and biological substances in the Universe. The possibility of detection and identifications with FTIR spectrometer of bio-aerosol spores (Bacillus atrophaeus var. globigii=BG) in the atmosphere is discussed in this paper. We describe the results of initial spectral measurements performed in the laboratory and in the field. The purpose of these experiments was to detect and to identify bio-aerosol spores in two conditions: 1) In a closed chamber where the thermal contrast between the background and aerosols was large, and 2) In open air where the thermal contrast between the background and aerosols was small. The extinction spectrum of BG spores was deduced by comparing our measurements with models, and other measurements known from the literature. Our theoretical and experimental studies indicate that, during passive remote sensing measurements, it is difficult—but possible to detect and to identify bio-aerosol clouds by their spectral signatures. The simple spectral analysis described in the paper can be useful for the detection of various kinds of trace aerosols—not only in the Earth’s atmosphere, but also during planetary missions in the environments of other astronomical objects such as planets, comets etc. We expect that the interpretation of data from spectrometric sounding of Venus and Mars during the current missions Mars and Venus Express, and later during the Rosetta mission will benefit from our experimental work and numerical modelling.

Required Spectral Resolution for Bioaerosol Detection Algorithms Using Standoff Laser-Induced Fluorescence Measurements

We have developed and tested a standoff biological aerosol detection demonstrator employing ultraviolet laser-induced fluorescence. It is based on commercially available components including a pulsed 355-nm laser and an intensified charge-coupled device camera. Biological warfare simulants and interferents were released and measured in open air field and closed-chamber laboratory tests. We analyzed the experimental data at different spectral resolutions, using statistics-based anomaly detection, and spectral angle mapping algorithms. The results show that less than 20 spectral channels in the 350-700-nm spectral region are sufficient in order to discriminate between the agents released using these methods. This corresponds to sacrificing high spectral resolution for the benefit of more photons in each channel and reduced computation time.

Infrared differential-absorption Mueller matrix spectroscopy and neural network-based data fusion for biological aerosol standoff detection

An active spectrophotopolarimeter sensor and support system were developed for a military/civilian defense feasibility study concerning the identification and standoff detection of biological aerosols. Plumes of warfare agent surrogates gamma-irradiated Bacillus subtilis and chicken egg white albumen (analytes), Arizona road dust (terrestrial interferent), water mist (atmospheric interferent), and talcum powders (experiment controls) were dispersed inside windowless chambers and interrogated by multiple CO(2) laser beams spanning 9.1-12.0 microm wavelengths (lambda). Molecular vibration and vibration-rotation activities by the subject analyte are fundamentally strong within this "fingerprint" middle infrared spectral region. Distinct polarization-modulations of incident irradiance and backscatter radiance of tuned beams generate the Mueller matrix (M) of subject aerosol. Strings of all 15 normalized elements {M(ij)(lambda)/M(11)(lambda)}, which completely describe physical and geometric attributes of the aerosol particles, are input fields for training hybrid Kohonen self-organizing map feed-forward artificial neural networks (ANNs). The properly trained and validated ANN model performs pattern recognition and type-classification tasks via internal mappings. A typical ANN that mathematically clusters analyte, interferent, and control aerosols with nil overlap of species is illustrated, including sensitivity analysis of performance.

Development and Characterization of an Aircraft Aerosol Time-of-Flight Mass Spectrometer

Vertical and horizontal profiles of atmospheric aerosols are necessary for understanding the impact of air pollution on regional and global climate. To gain further insight into the size-resolved chemistry of individual atmospheric particles, a smaller aerosol time-of-flight mass spectrometer (ATOFMS) with increased data acquisition capabilities was developed for aircraft-based studies. Compared to previous ATOFMS systems, the new instrument has a faster data acquisition rate with improved ion transmission and mass resolution, as well as reduced physical size and power consumption, all required advances for use in aircraft studies. In addition, real-time source apportionment software allows the immediate identification and classification of individual particles to guide sampling decisions while in the field. The aircraft (A)-ATOFMS was field-tested on the ground during the Study of Organic Aerosols in Riverside, CA (SOAR) and aboard an aircraft during the Ice in Clouds Experiment-Layer Clouds (ICE-L). Initial results from ICE-L represent the first reported aircraft-based single-particle dual-polarity mass spectrometry measurements and provide an increased understanding of particle mixing state as a function of altitude. Improved ion transmission allows for the first single-particle detection of species out to approximately m/z 2000, an important mass range for the detection of biological aerosols and oligomeric species. In addition, high time resolution measurements of single-particle mixing state are demonstrated and shown to be important for airborne studies where particle concentrations and chemistry vary rapidly.

Remote detection of biological aerosols at a distance of 3 km with a passive Fourier transform infrared (FTIR) sensor

Bio-aerosols containing Bacillus subtilis var. niger (BG) were detected at a distance of 3 km with a passive Fourier Transform InfraRed (FTIR) spectrometer in an open-air environment where the thermal contrast was low (~ 1 K). The measurements were analyzed with a new hyperspectral detection, identification and estimation algorithm based on radiative transfer theory and advanced signal processing techniques that statistically subtract the undesired background spectra. The results are encouraging as they suggest for the first time the feasibility of detecting biological aerosols with passive FTIR sensors. The number of detection events was small but statistically significant. We estimate the false alarm rate for this experiment to be 0.0095 and the probability of detection to be 0.61 when a threshold of detection that minimizes the sum of the probabilities of false alarm and of missed detection is chosen.

Multijet and multistage aerosol concentrator: design and performance analysis.

A multijet and multistage aerosol concentrator was designed and fabricated with two virtual impactors in a series. Collection efficiency, internal loss, and concentration factors were calculated at ambient conditions for each stage. The total inlet flow rate of the aerosol concentrator was set at 1000 L/min(-1), while the minor flow rate for the first stage was at 6.0% of the total inlet flow and the minor flow rate of the second stage was at 6.7% of the first stage minor flow. The aerosol concentrator was calibrated using polystyrene latex particles in aerodynamic sizes ranging from 0.5 to 10 microm. Several configurations of the multijet acceleration nozzles and multitube receptors were designed in this study. The effects of the different designs were subsequently evaluated through experimentation. It was found that a properly designed multijet and multistage aerosol concentrator can significantly improve aerosol concentration performance. Results showed that the concentration factor increases from 1 to 240 over the particle size range studied. Applications of the multijet and multistage aerosol concentrator with high-volume flow rate can vary widely, from detection of biological aerosols at low concentration, laboratory aerosol sampling, clean room monitoring, and ambient aerosol measurements.

Simultaneous light scattering and intrinsic fluorescence measurement for the classification of airborne particles

We describe a prototype laboratory light-scattering instrument that integrates two approaches to airborne particle characterization: spatial light-scattering analysis and intrinsic fluorescence measurement, with the aim of providing an effective means of classifying biological particles within an ambient aerosol. The system uses a single continuous-wave 266-nm ultraviolet laser to generate both the spatial elastic scatter data (from which an assessment of particle size and shape is made) and the particle intrinsic fluorescence data from particles in the approximate size range of 1-10-mum diameter carried in a sample airflow through the laser beam. Preliminary results suggest that this multiparameter measurement approach can provide an effective means of classifying different particle types and can reduce occurrences of false-positive detection of biological aerosols.

Size and Fluorescence Measurements for Field Detection of Biological Aerosols

This paper describes an instrument developed to monitor the biological fraction of an aerosol. The instrument simultaneously sizes individual particles in a flowing air stream and measures their total fluorescence following excitation at 266 nm. Laboratory data show that these two parameters enable discrimination between individuals of certain bacterial species. Field measurements are presented in which bacterial samples were aerosolized and subsequently detected 800 m downwind.

Detection of biological aerosols by luminescence techniques

Luciferin–luciferase (LL) luminescence techniques were used to successfully measure the adenosine triphosphate (ATP) content (pg/ml) in aerosol samples containing either vegetative bacterial cells or spores. Aerosols were collected with wet or dry sampling devices. Evaluation for the presence of total biomass from both bacterial and nonbacterial sources of ATP was achieved by suspending the collected aerosol samples in phosphate-buffered saline (PBS), using a pipette to draw off a 50-μl aliquot of the PBS suspension into a Filtravette™, and then adding bacterial releasing agent (BRA). The sample was then reacted with LL, and the resulting relative luminescence units (RLUs), indicative of the total ATP content, were measured. Identical techniques were used to prepare the bacterial cells for analysis with one additional step: a wash with somatic cell releasing agent (SRA) before adding BRA. This step removes interfering substances or nonbacterial sources of ATP. For spore analysis, an equivolume sample of the PBS suspension was added to an equivolume of trypticase soy broth (TSB), incubated at 37 °C for 15 min, and processed using methods identical to bacterial cell analysis. With the use of these techniques we were able to detect Bacillus subtilis variation niger, formerly known as Bacillus globigii (BG) in artificially inoculated aerosol samples at concentrations ≥ 105 colony-forming units (CFU) per milliliter. Results of field and chamber trials show that one can detect the presence of bacterial and nonbacterial sources of ATP. These techniques may be appropriate to situations where the measurement of bacterial aerosols is needed. © 1999 John Wiley & Sons, Inc.* Field Analyt Chem Technol 3: 283–290, 1999

Detection of biological aerosols by luminescence techniques

Detection of biological aerosols by luminescence techniques

Chemical and biological aerosol detection and identification with field analytical instrumentation

Chemical and biological aerosol detection and identification with field analytical instrumentation

Continuous, rapid biological aerosol detection with the use of UV fluorescence: Outdoor test results

This report describes the design and principles of operation of an instrument for separately monitoring ambient aerosol concentrations of biological and nonbiological composition. A method of outdoor testing, and recent results, are also described. The single-particle fluorescence analyzer (SPFA) draws ambient air into an optical chamber through a sampling nozzle. Detection signals from each aerosol particle consist of an elastic scattering response as well as fluorescent emission in two distinct spectral bands. Differentiation of biological aerosols is based on the relative intensity of ultraviolet (UV) fluorescence measured from the particles following excitation with a 266-nm-wavelength laser pulse. During outdoor tests two types of organisms were released as aerosol sprays: Erwinia herbicola vegetative cells and Bacillus subtilis spores. The SPFA participated in 39 of a total set of 40 outdoor tests. Twenty-seven tests released E. herbicola and nine released B. subtilis. Analysis of these results indicates that a reliability of detection of about 90% for E. herbicola, and of about 87% for B. subtilis were achieved under the conditions of the tests, with a sensitivity near 1 particle/l. Some tests involved release of nonbiological aerosols that did not result in a significant change in fluorescent signals in the instrument. © 1999 John Wiley & Sons, Inc.* Field Analyt Chem Technol 3: 249–259, 1999

Real time detection of biological aerosols with fluorescence aerodynamic particle sizer (FLAPS)

Real time detection of biological aerosols with fluorescence aerodynamic particle sizer (FLAPS)