Survey of residential indoor particulate matter measurements 1990-2019.

We surveyed literature on measurements of indoor particulate matter in all size fractions, in residential environments free of solid fuel combustion (other than wood for recreation or space heating). Data from worldwide studies from 1990 to 2019 were assembled into the most comprehensive collection to date. Out of 2752 publications retrieved, 538 articles from 433 research projects met inclusion criteria and reported unique data, from which more than 2000 unique sets of indoor PM measurements were collected.

Single-angle reflectance spectroscopy to determine the optical constants n and k: considerations in the far-infrared domain.

Single-angle infrared (IR) reflectance spectroscopy is a proven and effective method for determining the complex optical constants n and k of condensed matter. The modern method uses a Fourier transform IR spectrometer to record the quantitative reflectance R(ν) spectra followed by application of the Kramers-Kronig transform (KKT) to obtain the complex optical constants. In order to carry out the KKT, it is essential to measure the reflectance spectra to as high and low a frequency (wavenumber) as possible.

Optical and Chemical Characterization of Uranium Dioxide (UO) and Uraninite Mineral: Calculation of the Fundamental Optical Constants.

Uranium dioxide (UO) is a material with historical and emerging applications in numerous areas such as photonics, nuclear energy, and aerospace electronics. While often grown synthetically as single-crystal UO, the mineralogical form of UO called uraninite is of interest as a precursor to various chemical processes involving uranium-bearing chemicals. Here, we investigate the optical and chemical properties of a series of three UO specimens: synthetic single-crystal UO, uraninite ore of relatively high purity, and massive uraninite mineral containing numerous impurities.

Evidence for Quinone Redox Chemistry Mediating Daytime and Nighttime NO-to-HONO Conversion on Soil Surfaces.

Humic acid (HA) is thought to promote NO conversion to nitrous acid (HONO) on soil surfaces during the day. However, it has proven difficult to identify the reactive sites in natural HA substrates. The mechanism of NO reduction on soil surrogates composed of HA and clay minerals was studied by use of a coated-wall flow reactor and cavity-enhanced spectroscopy.

Combined Flux Chamber and Genomics Approach Links Nitrous Acid Emissions to Ammonia Oxidizing Bacteria and Archaea in Urban and Agricultural Soil.

Nitrous acid (HONO) is a photochemical source of hydroxyl radical and nitric oxide in the atmosphere that stems from abiotic and biogenic processes, including the activity of ammonia-oxidizing soil microbes. HONO fluxes were measured from agricultural and urban soil in mesocosm studies aimed at characterizing biogenic sources and linking them to indigenous microbial consortia. Fluxes of HONO from agricultural and urban soil were suppressed by addition of a nitrification inhibitor and enhanced by amendment with ammonium (NH4(+)), with peaks at 19 and 8 ng m(-2) s(-1), respectively.

Release of nitrous acid and nitrogen dioxide from nitrate photolysis in acidic aqueous solutions.

Nitrate (NO3(-)) is an abundant component of aerosols, boundary layer surface films, and surface water. Photolysis of NO3(-) leads to NO2 and HONO, both of which play important roles in tropospheric ozone and OH production. Field and laboratory studies suggest that NO3¯ photochemistry is a more important source of HONO than once thought, although a mechanistic understanding of the variables controlling this process is lacking.

Photooxidation of ammonia on TiO2 as a source of NO and NO2 under atmospheric conditions.

Ammonia is the most abundant reduced nitrogen species in the atmosphere and an important precursor in the industrial-scale production of nitric acid. A coated-wall flow tube coupled to a chemiluminescence NOx analyzer was used to study the kinetics of NH3 uptake and NOx formation from photochemistry initiated on irradiated (λ > 290 nm) TiO2 surfaces under atmospherically relevant conditions. The speciation of NH3 on TiO2 surfaces in the presence of surface-adsorbed water was determined using diffuse reflection infrared Fourier transform spectroscopy.