Analysis of Conventional and Biodegradable Microplastics in Solid Sample Matrices: A Contribution to Method Standardization

Microplastics are the new emerging pollutants ubiquitously detectable in aquatic and terrestrial ecosystems. Fate and behavior as well as ecotoxicity are of increasing environmental concern particularly in sediments and soils as natural sinks. For a global environmental risk assessment reliable and easy to apply analytical methods are mandatory to obtain comparable data. This is based on the isolation of microplastics out of the solid sample matrices prior to instrumental detection. Thus, this study provides a validated approach for density separation, which emerged from a comparative study using different salt solutions to isolate conventional and for the first time biodegradable microplastics from different solid sample matrices, i.e., sand, artificial soil, and compost. Four solutions (water, sodium chloride, sodium hexametaphosphate and sodium bromide) of different densities were applied followed by oxidizing digestion. Finally, the impact of the procedures on size and surface properties of microplastics was tested. Dependent on the sample matrix, highest recovery rates of 87.3-100.3 % for conventional polymers and 38.2–78.2 % for biodegradable polymers were determined with sodium bromide. It could be shown that the type of solid sample matrix influences the recovery rates and has to be considered when choosing a sample preparation technique.

RESEARCH TEMPERATURES OF IGNITION AND SELF-IGNITION OF COTTON AND POLYESTER FABRICS

Formulation of the problem. Most of the fabrics used in the technological processes of garment enterprises are classified as combustible materials and are part of the fire load, which threatens the outbreak and rapid spread of fires in the premises of garment factories. Therefore, it is important to study the indicators of the fire hazard of fabrics to identify the most dangerous of them, as well as to increase the efficiency of fire safety at sewing enterprises.The purpose of the work is to obtain the dependences of the values of ignition and self-ignition temperatures of cotton fabrics on the composition of cotton.Results. It was found that the crushed 100% cotton fabric flamed best, and the worst − solid polyester as a fabric without cotton. The lowest value of the temperature at which ignition was observed was 215°C for cotton (100%, shredded fabric), and if this value is reduced - there were failures, which are caused in particular by the fact that at lower temperatures flammable vapours are no formed in concentrations sufficient for combustion. It was found that the ignition / spontaneous combustion temperatures for a solid sample of the fabric with a composition of 100% cotton are 235°C/420°C, and for a solid sample of the fabric with a composition of 100% polyester − 360°C/500°C, respectively. Ignition / spontaneous com-bustion temperatures for finely divided fabrics are 8,5%/4,78% (cotton fabric) and 2.8%/6% (polyester) lower than the values obtained for whole fabrics.Results. According to the results of the analysis of the most common fabrics (table 1) used in garment enterprises. Identified that the biggest fire hazard is inherent containing cotton. The lowest ignition temperature is observed for cotton (100% shredded fabric) and is 215°C, which is 1,63 times less than the ignition temperature of polyester (0% cotton, shredded fabric). The lowest self-ignition temperature is also observed for cotton (100% shredded fabric) and is 400°C, which is 1,18 less than the self-ignition temperature of polyester (0% cotton, shredded fabric).

Transformations of empty CuI4 core to CuI2CuII2O and CuI6S cores via oxide and sulfide insertions

[Cu4(LRh)4]8– ([1]8–; LRh = Δ-[Rh(L-cysteinate)3]3–), with an empty tetrahedral {CuI4}4+ core, was converted to [Cu4O(LRh)4]8– ([2]8–), with a mixed-valent {CuI2CuII2O}4+ core, in aqueous NaOH. A solid sample of the latter...

Interaction of a Low-Power Laser Radiation with Nanoparticles Formed over the Copper Melt in Rarefied Argon Atmosphere

Two effects have been recently observed by the authors for the copper sample melted in a rarefied argon atmosphere. The first of these effects is a strong decrease in the normal reflectance of a copper sample with time just after the beginning of melting. A partially regular crystal structure was also formed on the surface of the solid sample after the experiment. Both effects were explained by generation of a cloud of levitating nanoparticles. Additional experiments reported in the present paper show that the rate of decrease in reflectance increases with pressure of argon atmosphere and the surface pattern on the solid sample after the experiment depends on the probe laser radiation. It is theoretically shown for the first time that the dependent scattering effects in the cloud of copper nanoparticles are responsible for the abnormal decrease in normal reflectance and also for the observed significant role of light pressure in deposition of nanoparticles on the sample surface. The predicted minimum of normal reflectance is in good agreement with the experimental value.

Supplemental Material: Experimental constraints on nonskeletal CaCO3 precipitation from Proterozoic seawater

Experimental method with figures, solution compositions, and solid sample characterization.<br>

Supplemental Material: Experimental constraints on nonskeletal CaCO3 precipitation from Proterozoic seawater

Experimental method with figures, solution compositions, and solid sample characterization.<br>

Theoretical aspects of transient temperature on cubic crystal surface in a photoacoustic effect

In photoacoustic effect, the solid sample absorbs a fraction of the radiation falling upon it and excitation process occurs. The type of excitation depends on the energy of the incident radiation. The relaxation processes, which are also popularly known as non-radiative de-excitation processes generally take place. The light – matter interaction is responsible for the generation of heat within the solid sample. The temperature of the sample changes due to absorption and non-radiative relaxation by the atoms. The pressure fluctuations will be generated due to the heating and cooling of the sample. Today, crystalline solids are widely studied due to their wide scientific and industrial applications. Temperature is one of the important parameter to be studied regarding artificial preparation of large crystals. In this paper, transient translational temperature on the surface of a homogeneous isotropic cubic crystal kept in a photoacoustic cell is calculated theoretically. For a simple cubic homogeneous crystal kept in a photoacoustic cell, an airy stress function is determined based on laser interaction with surface of the crystal. By applying the finite Marchi-Fasulo integral transform method within the crystal size limitations, transient translational temperature is exactly determined.