Identification of the sources of PM10 in a subway tunnel using positive matrix factorization

The level of particulate matter of less than 10 μm diameter (PM₁₀) at subway platforms can be significantly reduced by installing a platform screen-door system. However, both workers and passengers might be exposed to higher PM₁₀ levels while the cars are within the tunnel because it is a more confined environment. This study determined the PM₁₀ levels in a subway tunnel, and identified the sources of PM₁₀ using elemental analysis and receptor modeling. Forty-four PM₁₀ samples were collected in the tunnel between the Gireum and Mia stations on Line 4 in metropolitan Seoul and analyzed using inductively coupled plasma–atomic emission spectrometry and ion chromatography. The major PM₁₀ sources were identified using positive matrix factorization (PMF). The average PM₁₀ concentration in the tunnels was 200.8 ± 22.0 μg/m³. Elemental analysis indicated that the PM₁₀ consisted of 40.4% inorganic species, 9.1% anions, 4.9% cations, and 45.6% other materials. Iron was the most abundant element, with an average concentration of 72.5 ± 10.4 μg/m³. The PM₁₀ sources characterized by PMF included rail, wheel, and brake wear (59.6%), soil combustion (17.0%), secondary aerosols (10.0%), electric cable wear (8.1%), and soil and road dust (5.4%). Internal sources comprising rail, wheel, brake, and electric cable wear made the greatest contribution to the PM₁₀ (67.7%) in tunnel air.

ImplicationsWith installation of a platform screen door, PM₁₀ levels in subway tunnels were higher than those on platforms. Tunnel PM₁₀ levels exceeded 150 μg/m³ of the Korean standard for subway platform. Elemental analysis of PM₁₀ in a tunnel showed that Fe was the most abundant element. Five PM₁₀ sources in tunnel were identified by positive matrix factorization. Railroad-related sources contributed 68% of PM₁₀ in the subway tunnel.     

Thermal conductivity characteristics of dewatered sewage sludge by thermal hydrolysis reaction

The purpose of this study is to quantify the thermal conductivity of sewage sludge related to reaction temperature for the optimal design of a thermal hydrolysis reactor. We continuously quantified the thermal conductivity of dewatered sludge related to the reaction temperature. As the reaction temperature increased, the dewatered sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. Therefore, the bound water in the sludge cells comes out as free water, which changes the dewatered sludge from a solid phase to slurry in a liquid phase. As a result, the thermal conductivity of the sludge was more than 2.64 times lower than that of the water at 20℃. However, above 200℃, it became 0.704 W/m?°C, which is about 4% higher than that of water. As a result, the change in physical properties due to thermal hydrolysis appears to be an important factor for heat transfer efficiency.

ImplicationsThe thermal conductivity of dewatered sludge is an important factor the optimal design of a thermal hydrolysis reactor. The dewatered sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. The liquid phase slurry has a higher thermal conductivity than pure water.     

Lagged effect of exports,industrialization and urbanization on carbon footprint in Southeast Asia

The study aims to examine lagged causal effect of economic development policies on the carbon footprint of Southeast Asia. This study employs unit root test, cointegration test and panel data analysis methods to examine endogeneity concerns in observational data. The study applies panel data analysis methods to address unobserved country effect in the model. The balanced panel data includes a total of 240 observations with five cross sections of five nations in Southeast Asia and with 48 time-specific periods of 1970–2017. The results indicate that (1) exports, industrialization, urbanization and economic growth have lagged negative effect on the carbon footprint of the region in the short-run, and (2) there exists a long-run equilibrium relationship among exports, industrialization, urbanization, economic growth and carbon footprint in the region. The findings suggest that the economic growth, exports, industrialization and urbanization of the developing countries in Southeast Asia have been achieved at the cost of increasing the carbon footprint of the region. The findings imply that the environmental policy of the export-led growth countries never have been effective so far since the nations have achieved their economic growth at the high cost of harming the environment of the nations.     

Memory effect on the dioxin emissions from municipal waste incinerator in Taiwan

Evaluation of the dioxin removal efficiency of the air pollution control device (APCD) at an existing municipal waste incinerator (MWI) located in Taiwan is conducted via stack sampling and analysis. The MWI investigated is equipped with cyclones, dry lime scrubbing systems and fabric filters as APCDs. Results indicate that the patterns of dioxin isomers at APCDs' inlet and stack are similar. During the first year of carbon injection, the concentrations of emitted dioxin decreased greatly. The dioxin removal efficiency increased from 26.9% to 96.6% after injecting 115 kg/day activated carbon (AC). At the second year, the dioxin removal efficiency reaches 98.7% after injecting the same rate of AC continuously. The lower efficiency achieved with activated carbon injection (ACI) during the first year can be attributed to the memory effect, i.e. the dioxin or precursor desorbs slowly to the flue gas and increases the dioxin concentration at stack, resulting in a lower dioxin removal efficiency than expected.     

Development of combined plant of biogas and bio solid-refuse-fuel from swine manure slurry

Journal of Material Cycles and Waste Management - An environment-friendly treatment of organic waste like swine manure and food waste is considered to be big challenge, because the residue of...     

Prüfanforderungen des Umweltbundesamtes zur Bewertung der Auswirkungen von Pflanzenschutzmitteln auf terrestrische Pflanzen

The fundamental data requirements for the authorization of plant protection products and the inclusion of active ingredients in Annex I of Council Directive 91/414/EEC are described in the Annexes II and III of this Directive. Definite instructions with regard to preconditions and for implementation and methodology (guidelines) concerning investigations with terrestrial plants are deficient. In the following, the scientific data requirements are explained for assessing the effects of plant protection products on terrestrial plants.     

Water extraction with CO2 bubbling as pretreatment of melting-furnace fly ash for metal recovery

In Japan, melting-furnace fly ash (MFA) generated from ash melting and gasification/melting plants is considered an “urban mine” due to its high metal content. This study aimed to develop a novel approach to pretreating MFA for metal recovery. Water extraction with CO₂ bubbling was investigated because MFA mainly consists of water-soluble salts containing elements such as Cl, Ca, Na, and K. Instead of acid addition, CO₂ bubbling was applied to maintain the optimal pH for minimizing the release of target metal elements and maximizing the removal of undesirable elements during water extraction. The results revealed that CO₂ bubbling effectively decreased the release of Pb, Zn, and Cd into the treatment water. This was mainly due to coprecipitation with CaCO₃, which was primarily formed by the reaction of Ca²⁺ from the MFA with CO₃ ²⁻ from the CO₂ gas. The bubbling process also helped accelerate the removal of Cl from MFA. Furthermore, the study showed that it is possible to lower the water-to-solid ratio to 5 with only a slight reduction in water extraction effect. Finally, approximately four times the concentration of target metals (rare metals and Cu, Pb, and Zn) was achieved by removing 90% of Cl, 70%–90% of Na and K, and 30%–40% of Ca through water extraction with CO₂ bubbling, resulting in a concentration of target metals that was nearly equal to that of ore.     

Observed chemical characteristics of long-range transported particles at a marine background site in Korea

Deokjeok Island is located off the west coast of the Korean Peninsula and is a suitable place to monitor the long-range transport of air pollutants from the Asian continent. In addition to pollutants, Asian dust particles are also transported to the island during long-range transport events. Episodic transport of dust and secondary particles was observed during intensive measurements in the spring (March 31-April 11) and fall (October 13-26) of 2009. In this study, the chemical characteristics of long-range-transported particles were investigated based on highly time-resolved ionic measurements with a particle-into-liquid system coupled with an online ion chromatograph (PILS-IC) that simultaneously measures concentrations of cations (Li+, Na , NH4+, K+, Ca2+, Mg2+) and anions (F-, C1-, NO3-, SO42-). The aerosol optical thickness (AOT) distribution retrieved by the modified Bremen Aerosol Retrieval (M-BAER) algorithm from moderate resolution imaging spectroradiometer (MODIS) satellite data confirmed the presence of a thick aerosol plume coming from the Asian continent towards the Korean peninsula. Seven distinctive events involving the long-range transport (LRT) of aerosols were identified and studied, the chemical components of which were strongly related to sector sources. Enrichment of acidic secondary aerosols on mineral dust particles, and even of sea-salt components, during transport was observed in this study. Backward trajectory, chemical analyses, and satellite aerosol retrievals identified two distinct events: a distinctively high [Ca2++Mg2]/[Na+] ratio (>2.0), which was indicative of a preprocessed mineral dust transport event, and a low [Ca2++Mg2+]/[Na+] ratio (<2.0), which was indicative of severe aging of sea-salt components on the processed dust particles. Particulate C1- was depleted by up to 85% in spring and 50% in the fall. A consistent fraction of carbonate replacement (FCR) averaged 0.53 in spring and 0.55 in the fall. Supporting evidences of C1- enrichment on the marine boundary layer prior to a dust front were also found. Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for sector and air mass classifications of clean and LRT cases.     

Comparative effectiveness of mixed organic substrates to mushroom compost for treatment of mine drainage in passive bioreactors

Bioreactors are one possible best sustainable technology to address the mine-impacted water problems. Several prospective substrates (mushroom compost, cow manure, sawdust, wood chips, and cut rice straw) were characterized for their ability to serve as a source of food and energy for sulfate-reducing bacteria. Twenty bench-scale batch bioreactors were then designed and set up to investigate relative effectiveness of various mixtures of substrates to that of mushroom compost, the most commonly used substrate in field bioreactors, for treating mine drainage with acidic (pH 3) and moderate pH (pH 6). Overall, reactive mixtures showed satisfactory performances in generating alkalinity, reducing sulfate and removing metals (Al>Fe>Mn) (up to 100%) at both pH conditions, for all substrates. The mixture of sawdust and cow manure was found as the most effective whereas the mixture containing 40% cut rice straw gave limited efficiency, suggesting organic carbon released from this substrate is not readily available for biodegradation under anaerobic conditions. The mushroom compost-based bioreactors released significant amount of sulfate, which may raise a more concern upon the start-up of field-scale bioreactors. The correlation between the extent of sulfate reduction and dissolved organic carbon/SO(4)(2-) ratio was weak and this indicates that the type of dissolved organic carbon plays a more important role in sulfate reduction than the absolute concentration and that the ratio is not sensitive enough to properly describe the relative effectiveness of substrate mixtures.     

Ecological recovery of vegetation on a coke-factory soil: role of plant antioxidant enzymes and possible implications in site restoration

The present paper investigated the short-term colonization by plants of a highly degraded soil in field conditions. The objectives were to identify, through phytosociological analysis, the plant species able to grow on such polluted areas and to characterize pollutant effects at different biological levels through analyses of plant oxidative status, plant growth or community indexes of richness and biodiversity. Our results showed that among the plants present in the uncontaminated surrounding area, only few species were able to colonize the polluted soil. These species were typical of the first years of grassland successions. Ecological indexes proved that the polluted soil vegetation presented a lower degree of species richness and biodiversity than the control area. These discrepancies were partly explained by pollutant phytotoxicity. Indeed, for several species including Erigeron canadensis and Oenothera biennis, we observed toxic effects of the polluted soil on plant height and biomass. Moreover, at the cellular level, changes in antioxidant enzyme activities (SOD, CAT, APX, GPX and GRD) and lipid peroxidation level (MDA) were observed. Such biochemical changes seemed to play an important role on plant sensitivity/tolerance to pollutants and thus to render them more or less competitive for colonization of such disturbed areas.