Installation of platform screen doors and their impact on indoor air quality: Seoul subway trains

In this study, variations of particulate matter (PM) concentrations in subway trains following installation of platform screen doors (PSDs) in the Seoul subway system were investigated. PM samples were collected in the trains on subway lines 1–8 before and after installation of PSDs. It was found that the mean PM₁₀ concentration in the trains after PSDs installation increased significantly by 29.9% compared to that before installation. In particular, the increase of PM₁₀ in line 6 was the highest at 103%. When the relationship between PM₁₀ and PM_2.5 was compared, coefficients of determination (r²) before and after PSDs installations were 0.696 and 0.169, respectively. This suggests that air mixing between the platform and the tunnel after PSDs installation was extremely restricted. In addition, the indoor/outdoor PM₁₀ ratio following PSDs installation increased from 1.32 to 2.97 relative to the period with no installed PSDs. Furthermore, this study revealed that PM levels in subway trains increased significantly after all underground PSDs were put in use. Several potential factors were examined that could result in this PM increase, such as train ventilation systems, operational conditions, passenger volume, subway depth, and the length of underground segments.

ImplicationsPM₁₀ concentrations inside the subway trains increased after PSDs installation. This indicates that air quality in trains was very seriously impacted by PSDs. PM₁₀ levels were also influenced by the tunnel depth and length of the underground segments. To prevent the adverse effect on human health by PM₁₀ emitted from the tunnel, an applicable ventilation system to reduce PM₁₀ is required inside trains and tunnels.     

Hyperspectral reflectance response of freshwater macrophytes to salinity in a brackish subtropical marsh

Coastal freshwater wetlands are threatened by increased salinity due to relative sea level rise and reduced freshwater inputs. Remote radiometric measurement of freshwater marsh canopies to detect small shifts in water column salinity would be useful for assessing salinity encroachment. We measured leaf hyperspectral (300-1100 nm) reflectance of freshwater macrophytes (cattail, Typha latifolia and sea oxeye, Borrichia frutescens) in a field study in a subtropical brackish (2.5-4.5 parts per thousand salinity, per thousand) marsh to determine salinity effects on visible and near-infrared spectral band reflectance and to identify reflectance indices sensitive to small (1 per thousand) changes in wetland salinity. For sea oxeye, floating-position water band index [fWBI = R(900)/minimum(R(930) - R(980)), where R(lambda) = reflectance at band lambda], normalized difference vegetation index [NDVI = (R(774) - R(681))/(R(774) + R(681))], and a proposed wetland salinity reflectance ratio (WSRR = R(990)/R(933)) were sensitive to salinity with R2 of 40, 35, and 65%, respectively (p < 0.01). For cattail, NDVI and photochemical reflectance index [PRI = (R(531) - R(570))/(R(570) + R(531))] were sensitive to salinity with R2 of 29 and 33%, respectively (p 相似文献   

Hybrid zero valent iron (ZVI)/H2O2 oxidation process for landfill leachate treatment with novel nanosize metallic calcium/iron composite

A novel nanosize metallic calcium/iron dispersed reagent was synthesized and tested as coagulant/catalyst in a hybrid zero valent iron (ZVI)/H₂O₂ oxidation process to treat leachate. Two different types of leachates, one from municipal solid waste (MSW) tipping hall (MSWIL) and second from an MSW landfill site (MSWLL), were collected and characterized. The morphology, elemental composition, and mineral phases of the nano-Ca/CaO and nano-Fe/Ca/CaO were characterized by scanning electron microscopy–electron dispersive spectroscopy (SEM-EDS) and x-ray powder diffraction (XRD) analysis. The coagulation process with 2.5 g L^?1 nano-Ca/CaO attained 64.0, 56.0, and 20.7% removal of color, chemical oxygen demand (COD), and total suspended solids (TSS) in MSWLL. With only 1.0 g L^?1 of nano-Fe/Ca/CaO, relatively high color, COD and TSS removal was achieved in MSWLL at 67.5, 60.2, and 37.7%, respectively. The heavy metal removal efficiency reached 91–99% after treatment with nano-Fe/Ca/CaO in both leachate samples. The coupling process, using 1.0 g L^?1 of nano-Fe/Ca/CaO and 20 mM H₂O₂ doses, achieved enhancement removal of color, COD, and TSS, up to 95%, 96%, and 66%, respectively, without initial pH control. After this treatment, the color, COD, TSS, and heavy metals were significantly decreased, fitting the Korean discharge regulation limit. A hybrid coupled zero valent iron (ZVI)/H₂O₂ oxidation process with novel nanosized metallic calcium/iron dispersed reagent proved to be a suitable treatment for dealing with leachate samples.

Implications: Conventional treatments (biological or physicochemical) are not sufficient anymore to reach the level of purification needed to fully reduce the negative impact of landfill leachates on the environment. This implies that new treatment alternatives species must be proposed. A coupled zero valent iron (ZVI)/H₂O₂ oxidation process proved to be a suitable treatment for dealing with leachate samples. Coagulation with nFe/Ca/CaO allows 91–99% of heavy metals removal. The coupled coagulation–oxidation process by nFe/Ca/CaO reveals excellent ability to treat leachate. After coupled treatment the color, COD, and TSS were also much lower than the discharge regulation limit.     

Comparison of seven indicator PCBs and three coplanar PCBs in beef, pork, and chicken fat

The risk assessment of polychlorinated biphenyls (PCBs) is difficult since complex congeners were used in many industrial applications for a long period of time and the residue monitoring in foods of animal origin and the environment were not established in comparable systems. The relationships of determined concentrations in indicator PCB congeners (mono- and di-ortho PCBs) and coplanar PCB congeners (non-ortho PCBs) in livestock products are presented in this study. The concentrations of seven indicator PCBs were compared with three coplanar PCBs in beef, pork, and chicken fat. Distributions of concentration for the indicator PCBs in three different animal species were similar except for that of PCB-118 (2,3',4,4',5-pentachlorobiphenyl) in pork fat. The congeners with the highest concentration were PCB-138 (2,2',3,4,4',5'-hexachlorobiphenyl) in beef and pork fat and PCB-28 (2,4,4'-trichlorobiphenyl) in chicken fat. The bioaccumulation and metabolism of PCBs in animal species represent different congener profiles in livestock products. The percentage of the total concentration of three coplanar PCBs was about 2% of the total concentration of the seven indicator PCBs. Relatively high concentration of mono-ortho and di-ortho PCBs in fat samples of livestock products may be calculated with the concentration of coplanar PCBs that can be usually determined on a sequential procedure with dioxin analysis. Therefore, the relationship of the amounts between seven indicator PCBs and three coplanar PCBs may be useful to derive the composition and level of contaminants in beef, pork, and chicken.     

Tritium inventory prediction in a CANDU plant

The flow of tritium in a CANDU nuclear power plant was modeled to predict tritium activity build-up. Predictions were generally in good agreement with field measurements for the period 1983–1994. Fractional contributions of coolant and moderator systems to the environmental tritium release were calculated by least square analysis using field data from the Wolsong plant. From the analysis, it was found that: (1) about 94% of tritiated heavy water loss came from the coolant system; (2) however, about 64% of environmental tritium release came from the moderator system. Predictions of environmental tritium release were also in good agreement with field data from a few other CANDU plants. The model was used to calculate future tritium build-up and environmental tritium release at Wolsong site, Korea, where one unit is operating and three more units are under construction. The model predicts the tritium inventory at Wolsong site to increase steadily until it reaches the maximum of 66.3 MCi in the year 2026. The model also predicts the tritium release rate to reach a maximum of 79 KCi/yr in the year 2012. To reduce the tritium inventory at Wolsong site, construction of a tritium removal facility (TRF) is under consideration. The maximum needed TRF capacity of 8.7 MCi/yr was calculated to maintain tritium concentration effectively in CANDU reactors.     

Relative extraction ratio (RER) for arsenic and heavy metals in soils and tailings from various metal mines,Korea

This study focused on the evaluation of leaching behaviours for arsenic and heavy metals (Cd, Cu, Ni, Pb and Zn) in soils and tailings contaminated by mining activities. Ten representative mine soils were taken at four representative metal mines in Korea. To evaluate the leaching characteristics of the samples, eight extraction methods were adapted namely 0.1 M HCl, 0.5 M HCl, 1.0 M HCl, 3.0 M HCl, Korean Standard Leaching Procedure for waste materials (KSLP), Synthetic Precipitation Leaching Procedure (SPLP), Toxicity Characteristic Leaching Procedure (TCLP) and aqua regia extraction (AR) methods. In order to compare element concentrations as extraction methods, relative extraction ratios (RERs, %), defined as element concentration extracted by the individual leaching method divided by that extracted by aqua regia based on USEPA method 3050B, were calculated. Although the RER values can vary upon sample types and elements, they increase with increasing ionic strength of each extracting solution. Thus, the RER for arsenic and heavy metals in the samples increased in the order of KSLP < SPLP < TCLP < 0.1 M HCl < 0.5 M HCl < 1.0 M HCl < 3.0 M HCl. In the same extraction method, the RER values for Cd and Zn were relatively higher than those for As, Cu, Ni and Pb. This may be due to differences in geochemical behaviour of each element, namely high solubility of Cd and Zn and low solubility of As, Cu, Ni and Pb in surface environment. Thus, the extraction results can give important information on the degree and extent of arsenic and heavy metal dispersion in the surface environment.     

Benefits of mitigated ambient air quality due to transportation control on childhood asthma hospitalization during the 2002 summer Asian games in Busan, Korea

The objective of this study is to see whether there were any health benefits of mitigated air pollution concentration due to reduced traffic flow during a citywide intervention for the 2002 Summer Asian Games. Relative risks of hospitalization for childhood asthma during the post-Asian Game period compared with the baseline period were estimated using a time-series analysis of the generalized additive Poisson model. Fourteen consecutive days of traffic volume control in Busan during the Games reduced all regulated air pollutant levels by 1-25%. The estimated relative risk of hospitalization during the post-Games period over the baseline period was 0.73 (95% confidence interval [CI] = 0.49, 1.11). We observed that this reduced air pollution was unique in 2002 when the traffic volume reduction program was applied during the Games period. This empirical data provides epidemiologic evidence of the health benefits resulting from environmental interventions to reduce ambient air pollution.     

Study of the Climate Change Impacts on Water Quality in the Upstream Portion of the Cau River Basin,Vietnam

This paper presents simulations of climate change impacts on water quality in the upstream portion of the Cau River Basin in the North of Vietnam. The integrated modeling system GIBSI was used to simulate hydrological processes, pollutant and sediment wash-off in the river basin, and pollutant transport and transformation in the river network. Three projections for climate change based on emission scenarios B1, B2, and A2 of IPCC Special Report on Emission Scenarios (SRES) were considered. By assuming that the input pollution sources and watershed configuration were constant, based on 2008 data, water quality in the river network was simulated up to the terminal year 2050. For each climate change scenario, patterns of precipitation in wet and dry year were considered. The change in annual and monthly trends for dissolved oxygen (DO), biochemical oxygen demand (BOD), and ammonium ions (NH4+) load and concentration for different portions of the watershed have been analyzed. The results of these simulations show that climate change has more impact on changing the seasonal water quality parameters than on altering the average annual load of the pollutants. The percent change and change pattern in water quality parameters are different for wet and dry year, and the changes in wet year are smaller than those in dry year.     

Carbamazepine degradation by photolysis and titanium dioxide photocatalysis

We investigated the degradation of carbamazepine by photolysis/ultraviolet (UV)-C only and titanium dioxide photocatalysis. The degradation of carbamazepine by UV-only and titanium-dioxide-only (adsorption) reactions were inefficient, however, complete degradation of carbamazepine was observed by titanium dioxide photocatalysis within 30 min. The rate of degradation increased as initial carbamazepine concentration decreased, and the removal kinetics fit well with the Langmuir-Hinshelwood model. The addition of methanol, a radical scavenger, decreased carbamazepine removal, suggesting that the hydroxide radical played an important role during carbamazepine degradation. The addition of oxygen during titanium dioxide photocatalysis accelerated hydroxide radical production, thus improving mineralization activity. The photocatalytic degradation was more efficient at a higher pH, whereas the removal of carbamazepine and acridine (a major intermediate) were more efficient under aerobic conditions. The mineralization of carbamazepine during photocatalysis produced various ionic by-products such as ammonium and nitrate by way of nitrogen dioxide.     

Assessment of the daily intake of 62 polychlorinated biphenyls from dietary exposure in South Korea

The dietary intake of polychlorinated biphenyls (PCBs) was estimated using the sum of 62 PCB congeners (∑₆₂PCBs), including seven indicator PCBs and 12 dioxin-like PCBs, in the South Korea. In this study, 200 individual food samples belonging to 40 different foodstuffs were investigated to estimate the distribution of PCB congeners in five sampling cities. PCB exposure was estimated using Korean dietary habits as established by the National Health and Nutrition Examination Survey (NHANES). The PCB concentrations in rice, the most frequently consumed food in Korea, was relatively low in whole food samples. The mean PCB levels measured in fish were the highest in this study, but each fish is consumed in relatively small amounts by the general population. Therefore, the daily dietary intake should also be considered with regard to human exposure to PCBs, especially with the consumption of contaminated foods. Dioxin-like PCB levels were also calculated using TEF values that were established in 2005. The average levels (pg TEQ/g) were 0.0002 for rice and 0.0098 for fish. The dioxin-like PCBs accounted for a relatively small percentage of the total PCBs, compared to previous studies. According to our research, the health risks associated with exposure to PCBs could be estimated using the tolerable daily intake (TDI) of the general population.