Characterization of the Strength of a Natural Sand and Artificial Sand Core Manufactured with Inorganic Binder

Natural sand and organic binders are commonly used in casting processes, but these ingredients produce environmental problems with dust and harmful TVOC(Total Volatile Organic Carbon) gases. Research on the introduction of artificial sand and inorganic binders to solve these environmental problems is being actively conducted mainly in the casting industry. Artificial sand has superior durability and a spherical shape compared to natural sand, and above all, it does not generate dust. In addition, inorganic binders have the advantage that no harmful gas is generated during casting and the used sand can be recycled. This study confirmed whether inorganic binders can be applied when replacing natural sand with artificial sand. First, eco-friendly inorganic binders that do not produce harmful gas were synthesized. Then characteristic analyses were carried out with artificial sand and natural sand. Physical and chemical properties were compared using X-Ray Fluorescence (XRF), Powder Flow Test (PFT) and particle size distribution analyses. The general strength and absorption (absolute humidity 29.9 g/cm³) strength of the sample core was measured using each sand (artificial sand, natural sand) and inorganic binder. Also, X-ray Photoelectron Spectroscope (XPS) analysis confirmed the combination structure. As a result, it was confirmed that artificial sand exhibited mold characteristics with similar strength even with lower inorganic binder content than natural sand.

Emission from Uyo Main Refuse Dumpsite and Potential Impact on Health

This paper presents potential impact on health of emission from landfill site on Uyo village road, Uyo local government area of Akwa Ibom State, Nigeria. Three sampling points were assessed for particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), hydrogen sulphide H2S, ammonia (NH3), total volatile organic carbon (TVOC) and hydrogen cyanide (HCN) using highly sensitive digital portable meters. The data obtained were expressed in terms of an air quality index. Air quality index indicates that the ambient air can be described as unhealthy for sensitive groups for NO2, unhealthy for SO2 and PM2.5 and moderate for CO, respectively. H2S, NH3, TVOC, HCN, PM10 were not indicated in USEPA air quality standards. It recommended that stringent and proper landfill emissions management together with appropriate burning of wastes should be considered in the study area to ease the risks associated with these pollutants on public health.

Halocarbon Emissions from Hazardous Waste Landfills: Analysis of Sources and Risks

Landfills are sources of fugitive volatile organic carbon (VOC) emissions, including halocarbons. The objective of this study was to evaluate the contribution of halogenated VOCs to the health risks associated with the exposure of workers operating in landfills, gathering information on the role of endogenous/exogenous sources present in anthropized areas. A hazardous waste landfill located in Turin, Italy was used as a case study. Ambient concentrations of 10 pollutants (BTEX, styrene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2-dichloroethane, and 1,2-dichloropropane), measured in 10 points of the landfill area, were considered and analyzed. The data had a monthly frequency and covered two years. A cumulative health risk analysis was conducted by applying a Monte-Carlo method. The results showed that the contribution of 1,2-dichloroethane and 1,2-dichloropropane was 17.9% and 19.4% for the total risk and hazard index respectively. Benzene and ethylbenzene gave the highest contribution to the total risk (56.8% and 24.8%, respectively). In the second phase of the study, waste typologies that are possibly responsible for halocarbon emissions were investigated. Halocarbon concentration trends and waste disposal records were compared. Although further investigation is needed, some waste typologies were not excluded to contribute to halocarbon emissions, in particular sludge coming from wastewater treatment plants.

High contributions of fossil sources to more volatile organic carbon

Sources of particulate organic carbon (OC) with different volatility have rarely been investigated despite the significant importance for better understanding of the atmospheric processes of organic aerosols. In this study we develop a radiocarbon (14C) based approach for source apportionment of more volatile OC (mvOC) and apply to ambient aerosol samples collected in winter in six Chinese megacities. mvOC is isolated by desorbing organic carbon from the filter samples in He at 200 °C in a custom-made aerosol combustion system for 14C analysis. Evaluation of this new isolation method shows that the isolated mvOC amount agrees very well with the OC1 fraction (also desorbed at 200 °C in He) measured by a thermal optical analyzer using the EUSAAR_2 protocol. The mvOC, OC and elemental carbon (EC) of thirteen combined PM2.5 samples in six Chinese cities are analyzed for 14C to investigate their sources and formation mechanisms. The relative contribution of fossil sources to mvOC is 59 ± 11 %, consistently larger than the contribution to OC (48 ± 16 %) and smaller than that to EC (73 ± 9 %), despite large differences in fossil contributions in different cities. The average difference in the fossil fractions between mvOC and OC is 13 % (7 %–25 %; range), similar to that between mvOC and EC (13 %; 4 %–25 %). SOC concentrations and sources are modelled based on the 14C-apportioned OC and EC, and compared with concentrations and sources of mvOC. SOC concentrations (15.4 ± 9.0 μg m-3) are consistently higher than those of mvOC (3.3 ± 2.2 μg m-3), indicating that only a fraction of SOC is accounted for by the more volatile carbon fraction desorbed at 200 °C. The fossil fraction in SOC is 43 % (10 %–70 %), lower than that in mvOC (59 %; 45 %–78 %). Correlation between mvOC and SOC from non-fossil sources (mvOCnf vs. SOCnf) and from fossil sources (mvOCfossil vs. SOCfossil) are examined to further explore sources and formation processes of mvOC and SOC.

Simultaneous observations by sky radiometer and MAX-DOAS for characterization of biomass burning plumes in central Thailand in January–April 2016

The first intensive multi-component ground-based remote sensing observations by sky radiometer and Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) were performed simultaneously at the SKYNET/Phimai site located in central Thailand (15.18° N, 102.56° E) from January to April 2016. The period corresponds to the dry season associated with the intense biomass burning (BB) activity around the site. The near-surface concentration of formaldehyde (HCHO) retrieved from MAX-DOAS was found to be a useful tracer for BB plumes. As the HCHO concentration tripled from 3 to 9 ppbv, the ratio of gaseous glyoxal to HCHO concentrations in daytime decreased from ~ 0.04 to ~ 0.03, responding presumably to the increased contribution of volatile organic carbon emissions from BB. In addition, clear increases in aerosol absorption optical depths (AAODs) retrieved from sky radiometer observations were seen with the HCHO enhancement. At a HCHO of 9 ppbv, AAOD at a wavelength of 340 nm reached as high as ~ 0.15 ± 0.03. The wavelength dependence of AAODs at 340–870 nm was quantified by the absorption Ångström exponent (AAE), providing evidence for the presence of brown carbon aerosols at an AAE of 1.5 ± 0.2. Thus, our multi-component observations around central Thailand are expected to provide unique constraints for understanding physical/chemical/optical properties of BB plumes.