An Experimental Study on the Particle Concentration and Size Distribution of Smoke Generated by Flaming N-Heptane

The particles of smoke generated by flaming n-heptane was measured by Fast Particulate Spectrometer (DMS500), and the particle number concentration and size distribution were recorded and analyzed for investigating the smoke dynamic characteristics. The experimental results indicated that the particle number concentrations of buoyant plume above the flame approximately decrease with the height. At the center of ceiling, there is an approximate linear relationship between the particle number concentration and heat release rate. The count median diameter (CMD) varies with time and the change rate of CMD varies with particle concentration. In these experiments, the CMD is a constant in a few minutes after burning extinction.

Biomass burning aerosol emissions from vegetation fires: particle number and mass emission factors and size distributions

Aerosol emissions from vegetation fires have a large impact on air quality and climate. In this study, we use published experimental data and different fitting procedures to derive dynamic particle number and mass emission factors (EFPN, EFPM) related to the fuel type, burning conditions and the mass of dry fuel burned, as well as characteristic CO-referenced emission ratios (PN/CO, PM/CO). Moreover, we explore and characterize the variability of the particle size distribution of fresh smoke, which is typically dominated by a lognormal accumulation mode with count median diameter around 120 nm (depending on age, fuel and combustion efficiency), and its effect on the relationship between particle number and mass emission factors. For the particle number emission factor of vegetation fires, we found no dependence on fuel type and obtained the following parameterization as a function of modified combustion efficiency (MCE): EFPN=34·1015×(1-MCE) kg−1±1015 kg−1 with regard to dry fuel mass (d.m.). For the fine particle mass emission factors (EFPM) we obtained (86–85×MCE) g kg−1±3 g kg−1 as an average for all investigated fires; (93–90×MCE) g kg

Supramicron-sized particle clearance from alveoli: route and kinetics

Particles inhaled and deposited in the alveoli of the lung, i.e., distal to the tracheobronchial mucociliary escalator, may theoretically be cleared by several routes, including solubilization, lymphatic drainage, and the mucociliary pathway. We studied the clearance routes and kinetics of an inert insoluble carbonized polystyrene particle of supramicron size (2.85 micron count median diameter) tagged with 57Co (half-life 270 days) in the adult unanesthetized sheep. The rate of particle clearance, assessed by gamma scintillation camera of the whole lung, showed a three-exponential function, comprising a rapid initial phase in the first 44 h of clearance for tracheobronchial deposition followed by a slower phase of mostly alveolar clearance in the next 30 days and a final phase of very slow relatively pure alveolar clearance. A balance study of particle route during clearance and autopsy of regional thoracic lymph nodes, blood, liver, and spleen demonstrated that this supramicron-sized particle cleared from alveoli predominantly via the mucociliary escalator of the tracheobronchial tree. Whole-lung lavage studies showed particle and macrophage recovery rates suggesting a sequestered state for alveolar-deposited particles, which may partly account for their slow clearance rates. The failure to find interstitial penetration by alveolar-deposited particles indicates that the macrophages engulfing these particles, at low particle burdens, travel normally in only one direction, i.e., from interstitium to alveolus and then to the mucociliary escalator.

Alveolar clearance in dogs after inhalation of an iron 59 oxide aerosol

Six dogs each received two 60-min exposures, 6 months apart, to an aerosol of iron 59 oxide, having an average count median diameter of 0.09 μ and a geometric standard deviation of 1.8. The concentration of iron 59 in the inspired air ranged between 0.004–0.017 μc/liter. Lung measurements were made immediately after each exposure and up to 30 days postexposure. This procedure was followed in both initial and repeat exposures of each dog. A probe-type scintillation detector fitted with a focusing collimator was used to limit the measurements to specific respiratory tract positions on each dog. The biological half-time for alveolar clearance in the 12 studies ranged from 44 to 82 days with an average value of 62 days (sd 8.8 days). This consistency suggests the probability of a normal clearance rate and the possibility of its use as a functional test. Submitted on July 11, 1961