Vinyl-Asbestos Floor Risk Exposure in Three Different Simulations

Vinyl floors are widely used in public areas for their low cost and easy cleaning. From 1960 to 1980, asbestos was often added to improve vinyl floor performances. The Italian Ministerial Decree (M.D.) 06/09/94 indicates asbestos vinyl tiles as non-friable materials and, therefore, few dangerous to human health. This work aims to check through three different experimental tests if asbestos floor tiles, after decades of use, maintain their characteristics of compactness and non-friability. The effect of a small stone fragment stuck in the sole of rubber shoes was reproduced by striking the vinyl floor with a crampon. A vinyl tile was broken into smaller pieces with the aid of pliers to simulate what normally happens when workers replace the floors or sample it to verify the presence of asbestos. The third test reproduced the abrasion of the tile surface due to the dragging of furniture or heavy materials or sand grains that remain attached to the soles of shoes. The tests were carried out in safe conditions, working under an extractor hood with a glove box. Airborne sampling in the hood obtained the concentration of asbestos fibers produced in each test. The simulation tests performed confirms the possible release of fibers if the vinyl tiles are cut, abraded or perforated, as indicated by the Italian M.D.

Ground-Based Remote Retrievals of Cumulus Entrainment Rates

While fractional entrainment rates for cumulus clouds have typically been derived from airborne observations, this limits the size and scope of available datasets. To increase the number of continental cumulus entrainment rate observations available for study, an algorithm for retrieving them from ground-based remote sensing observations has been developed. This algorithm, called the Entrainment Rate In Cumulus Algorithm (ERICA), uses the suite of instruments at the Southern Great Plains (SGP) site of the U.S. Department of Energy's Atmospheric Radiation Measurement Program (ARM) Climate Research Facility as inputs into a Gauss–Newton optimal estimation scheme, in which an assumed guess of the entrainment rate is iteratively adjusted through intercomparison of modeled cloud attributes to their observed counterparts. The forward model in this algorithm is the explicit mixing parcel model (EMPM), a cloud parcel model that treats entrainment as a series of discrete entrainment events. A quantified value for the uncertainty in the retrieved entrainment rate is also returned as part of the retrieval. Sensitivity testing and information content analysis demonstrate the robust nature of this method for retrieving accurate observations of the entrainment rate without the drawbacks of airborne sampling. Results from a test of ERICA on 3 months of shallow cumulus cloud events show significant variability of the entrainment rate of clouds in a single day and from one day to the next. The mean value of 1.06 km−1 for the entrainment rate in this dataset corresponds well with prior observations and simulations of the entrainment rate in cumulus clouds.

Design and Sampling Characteristics of a New Airborne Aerosol Inlet for Aerosol Measurements in Clouds

Design of a new submicron aerosol inlet (SMAI) for airborne sampling of aerosol particles is introduced and its performance characteristics under a range of sampling conditions are presented. Analysis of inlet performance in clear-air and cloud systems shows that submicron aerosols are sampled representatively by the inlet, and in comparison with other types of inlets the SMAI has a relatively minor or nonexistent problem of droplet shatter contamination. The SMAI has a flow-through cone, with a perpendicular subsampling tube inside it. The cone acts as a virtual blunt body and decelerates the velocity directed toward a subsampling tube within the cone, resulting in reduced droplet impaction velocities and negligible artifact particle generation. The use of a perpendicular subsampling tube helps eliminate large shattered droplets from entering the sample volume, though it also results in lowering the aerosol sampling cut size. The SMAI sampling characteristics are determined from computational fluid dynamics simulations, and its cut size is calculated to be ~3 μm. In warm clouds, the shatter artifacts in the SMAI measurements are significantly less than that in a diffuser-type inlet, and shatter artifacts are only observed to increase when concentrations of drops larger than ~100 μm increase. In cold-cloud systems, shatter artifacts are significantly reduced with SMAI and some dependence of the inlet’s performance on the shape of the ice particles is observed.

A novel Whole Air Sample Profiler (WASP) for the quantification of volatile organic compounds in the boundary layer

The emission and fate of reactive VOCs is of inherent interest to those studying chemical biosphere-atmosphere interactions. In-canopy VOC observations are obtainable using tower-based samplers, but the lack of suitable sampling systems for the full boundary layer has limited the data characterizing the vertical structure of such gases above the canopy height and still in the boundary layer. This is the important region where many reactive VOCs are oxidized or otherwise removed. Here we describe an airborne sampling system designed to collect a vertical profile of air into a 3/8" OD tube 150 m in length. The inlet ram air pressure is used to flow sampled air through the tube, which results in a varying flow rate based on aircraft speed and altitude. Since aircraft velocity decreases during ascent, it is necessary to account for the variable flow rate into the tube. This is accomplished using a reference gas that is pulsed into the air stream so that the precise altitude of the collected air can be reconstructed post-collection. The pulsed injections are also used to determine any significant effect from diffusion/mixing within the sampling tube, either during collection or subsequent extraction for gas analysis. This system has been successfully deployed, and we show some measured vertical profiles of isoprene and its oxidation products methacrolein and methyl vinyl ketone from a mixed canopy near Columbia, Missouri.

Allocation of Terrestrial Carbon Sources Using 14CO2: Methods, Measurement, and Modeling

The radiocarbon content of whole air provides a theoretically ideal and now observationally proven tracer for recently added fossil-fuel-derived CO2 in the atmosphere (Cff). Over large industrialized land areas, determination of Cff also constrains the change in CO2 due to uptake and release by the terrestrial biosphere. Here, we review the development of a Δ14CO2 measurement program and its implementation within the US portion of the NOAA Global Monitoring Division's air sampling network. The Δ14CO2 measurement repeatability is evaluated based on surveillance cylinders of whole air and equates to a Cff detection limit of <0.9 ppm from measurement uncertainties alone. We also attempt to quantify additional sources of uncertainty arising from non-fossil terms in the atmospheric 14CO2 budget and from uncertainties in the composition of “background” air against which Cff enhancements occur. As an example of how we apply the measurements, we present estimates of the boundary layer enhancements of Cff and Cbio using observations obtained from vertical airborne sampling profiles off of the northeastern US. We also present an updated time series of measurements from NOAA GMD's Niwot Ridge site at 3475 m asl in Colorado in order to characterize recent Δ14CO2 variability in the well-mixed free troposphere.