Development of visibility forecasting modeling framework for the Lower Fraser Valley of British Columbia using Canada’s Regional Air Quality Deterministic Prediction System

Visibility degradation, one of the most noticeable indicators of poor air quality, can occur despite relatively low levels of particulate matter when the risk to human health is low. The availability of timely and reliable visibility forecasts can provide a more comprehensive understanding of the anticipated air quality conditions to better inform local jurisdictions and the public. This paper describes the development of a visibility forecasting modeling framework, which leverages the existing air quality and meteorological forecasts from Canada’s operational Regional Air Quality Deterministic Prediction System (RAQDPS) for the Lower Fraser Valley of British Columbia. A baseline model (GM-IMPROVE) was constructed using the revised IMPROVE algorithm based on unprocessed forecasts from the RAQDPS. Three additional prototypes (UMOS-HYB, GM-MLR, GM-RF) were also developed and assessed for forecast performance of up to 48 hr lead time during various air quality and meteorological conditions. Forecast performance was assessed by examining their ability to provide both numerical and categorical forecasts in the form of 1-hr total extinction and Visual Air Quality Ratings (VAQR), respectively. While GM-IMPROVE generally overestimated extinction more than twofold, it had skill in forecasting the relative species contribution to visibility impairment, including ammonium sulfate and ammonium nitrate. Both statistical prototypes, GM-MLR and GM-RF, performed well in forecasting 1-hr extinction during daylight hours, with correlation coefficients (R) ranging from 0.59 to 0.77. UMOS-HYB, a prototype based on postprocessed air quality forecasts without additional statistical modeling, provided reasonable forecasts during most daylight hours. In terms of categorical forecasts, the best prototype was approximately 75 to 87% correct, when forecasting for a condensed three-category VAQR. A case study, focusing on a poor visual air quality yet low Air Quality Health Index episode, illustrated that the statistical prototypes were able to provide timely and skillful visibility forecasts with lead time up to 48 hr.

Implications: This study describes the development of a visibility forecasting modeling framework, which leverages the existing air quality and meteorological forecasts from Canada’s operational Regional Air Quality Deterministic Prediction System. The main applications include tourism and recreation planning, input into air quality management programs, and educational outreach. Visibility forecasts, when supplemented with the existing air quality and health based forecasts, can assist jurisdictions to anticipate the visual air quality impacts as perceived by the public, which can potentially assist in formulating the appropriate air quality bulletins and recommendations.     

Uranium and other trace elements’ distribution in Korean granite: implications for the influence of iron oxides on uranium migration

To understand trace radionuclide (uranium) migration occurring in rocks, a granitic batholith located at the Korea Atomic Energy Research Institute (KAERI) site was selected and investigated. The rock samples obtained from this site were examined using mineralogical methods, including scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The changes in the distribution pattern of uranium (U) and small amounts of trace elements, and the mineralogical textures affected by weathering, were examined. Based on the element distribution analyses, it was found that Fe²⁺ released from fresh biotite is oxidized in short geological time, forming amorphous iron oxides, such as ferrihydrite, around silicate minerals. In that case, the amorphous ferrihydrite does not show distinct adsorption for U. However, as it gradually crystallizes to goethite or hematite, the most U-rich phases were found to be associated with the secondary iron oxides having granular forms. This evidence suggests that the geological subsurface environment is favorable for the crystallized iron oxides to keep their structures more stable for a long time as compared with the amorphous phases. There is a possibility that the long residence of U which is in contact with the stable crystalline phases of iron may finally lead to the partial sequestration of U in their structure. Consequently, it seems that Fe-oxide crystallization can be a dominating mechanism for U uptake and controls long-term U transport in granites with low U contents.     

Biophoton emission of MDCK cell with hydrogen peroxide and 60 Hz AC magnetic field

We studied biophoton characteristics of Madin-Darby canine kidney (MDCK) cells under the influence of H2O2 by employing a photomultiplier tube (PMT) and a fluorescence microscope. H2O2 was used for producing reactive oxygen species (ROS) in the measurement. Images from a fluorescence microscope show an increase of photon intensity emitted from the sample due to H2O2. By using a PMT we measured quantitative change in biophoton emission with application of H2O2 to the MDCK cell culture, found that the increase of the biophoton is dependent upon the amount of H2O2. The agreement between the results of the PMT and the fluorescence microscope suggests the possibility of quantitative measurement of the influence of ROS on living tissue or cell. In addition we applied a 60 HzAC magnetic field on the cells to investigate the change in reaction between MDCK cell and ROS. It showed that a decay of chemiluminescence intensity has taken a different path following exposure to the magnetic field. As a result, the PMT measurement might be considered as a useful tool for studying biochemical characteristics in relation to ROS.     

Physiological responses of Cladophora glomerata to cyanotoxins: a potential new phytoremediation species for the Green Liver Systems

Due to increased pollution of potable water sources as a consequence of eutrophication and anthropogenic xenobiotics, sustainable water purification is an essential concern. Therefore, the Green Liver System, a natural, economic and sustainable water purification system employing the biotransformation capabilities of aquatic plants, was developed. To expand the capacities and applications of this system, new aquatic plants are continually evaluated for their potential to remediate various aquatic pollutants. In this study, the potential of Cladophora glomerata to internalize cyanotoxins, microcystins (MCs) and anatoxin-a, and consequently its ability to cope with the subsequent oxidative stress associated with toxin-uptake were investigated. C. glomerata was able to take up all three of the tested MC congeners as well as anatoxin-a, similarly to previous toxin internalizations reported for aquatic plants such as Ceratophyllum demersum, Myriophyllum spicatum and Hydrilla versiculata. The antioxidative stress defense of C. glomerata proved to efficiently endure the toxin-uptake with no adverse effects. Subsequently, the uptake potential of C. glomerata was investigated at lab-scale by exposure to the three MC congeners and anatoxin-a collectively. After a period of seven days, 95–97% of the MCs and 100% of anatoxin-a were removed from the exposure media. C. glomerata therefore, is a suitable candidate to be incorporated in future Green Liver Systems.     

Production of gaseous fuel from refuse plastic fuel via co-pyrolysis using low-quality coal and catalytic steam gasification

In this study, refuse plastic fuel (RPF) was copyrolyzed with low-quality coal and was gasified in the presence of a metal catalyst and steam. Some metal catalysts, such as Ni, NiO, and Mg, and mixtures of these with base promoters such as Al₂O₃ and Fe₂O₃ were employed in the pyrolysis and gasification processes to convert the synthesis gas into more valuable fuel gas. The operating temperatures for the pyrolysis and gasification were between 700° and 1000°C. The experimental parameters were the operating temperature, catalyst type, basic promoter type, and steam injection amount. Solid fuel samples (5 g) were fed into a semibatch-type quartz tube reactor when the reactor reached the designated temperature. The synthesis gas was analyzed by gas chromatography. The use of low-quality coal as fuel in co-pyrolysis with RPF was explored. For the co-pyrolysis of RPF and low-quality coal, the effectiveness of the catalysts for fuel gas production followed the order Mg > NiO > Ni. In catalytic gasification of RPF, the addition of Al₂O₃ seemed to reduce the activity of the corresponding catalysts Ni and Mg. The maximum fuel gas yield (92.6%) was attained when Mg/Fe₂O₃ was used in steam gasification at 1000°C.     

Settling and dewatering characteristics of granulated methane-oxidizing bacteria

We evaluated the settling ability and dewaterability of granulated methane-oxidizing bacteria (GMOB) after granulation using a continuous-flow reactor. A comparative analysis on settling and dewatering characteristics due to changes in sludge retention time (SRT, 10, 15 and 20 days) during cultivation of GMOB was conducted. In assessing dewaterability, the specific resistance to filtration (SRF) of activated sludge and GMOB was found to be 8.21×1013-2.38×1014 and 4.88 × 1012-1.98×1013 m/kg, respectively. It was confirmed that as SRT decreased, SRF of GMOB increased. In the case of bound extracellular polymeric substance (EPS), activated sludge registered 147.5 mg/g-VSS while GMOB exhibited 171-177.2 mg/g-VSS. In the case of extracellular polymeric substance soluble EPS in effluent, activated sludge measured 62 mg/L and GMOB had 17.4-21.4 mg/L. The particle size analysis showed that mean particle diameters of GMOB were 402, 369, and 350 μm, respectively, at SRTs of 20, 15 and 10 days. In addition, it was found that GMOB had a larger mean particle diameter and exhibited much better settleability and dewaterability than activated sludge did.     

Laboratory migration experiments with radionuclides and natural colloids in a granite fracture

Natural colloids in groundwater could facilitate radionuclide transport, provided the colloids are mobile, are present in sufficient concentrations and can adsorb radionuclides. This paper describes the results of a laboratory migration study carried out with combinations of radionuclides and natural colloids within a fracture in a large granite block to experimentally determine the impact of colloids on radionuclide transport. The 85Sr used in this study is an example of a moderately sorbing radionuclide, while the 241Am is typical of a strongly sorbed radionuclide with very low solubility. The natural colloids used in this study were isolated from granite groundwater from Atomic Energy of Canada (AECL) Underground Research Laboratory (URL), and consisted of mostly 1-10 nm organic colloids, along with lesser amounts of 10-450 nm colloids (organics and aluminosilicates). The measured coefficients for radionuclide sorption onto these colloids were between 3 x 10(2) and 1 x 10(3) ml/g for 85Sr, and between 7 x 10(4) and 7 x 10(5) mg/l for 241Am. The 85Sr sorption on the natural colloids appeared to be reversible. Migration experiments in the granite block were carried out by establishing a flow field between two boreholes (out of a total of nine) intersecting a main horizontal fracture. These experiments showed that dissolved 85Sr behaved as a moderately sorbing tracer, while dissolved 241Am was completely adsorbed by the fracture surfaces and showed no evidence of transport. However, when natural colloids were injected together with dissolved 241Am, a small amount of 241Am transport was observed, demonstrating the ability of natural colloids to facilitate the transport of radionuclides with low solubility. Natural colloids had only a minor effect on the transport of 85Sr. In a separate experiment to test the effect of higher colloid concentrations on 85Sr migration, synthetic colloids were produced from Avonlea bentonite. The introduction of a relatively high concentration of bentonite colloids actually reduced 85Sr transport because, compared to natural colloids, the bentonite colloids were less mobile and they sorbed 85Sr more strongly.     

Flow and dispersion in an urban cubical cavity

Flow and dispersion in an urban cubical cavity are numerically investigated using a Reynolds-averaged Navier–Stokes equations (RANS) model with the renormalization group (RNG) k–? turbulence closure model. The urban cubical cavity is surrounded by flank walls that are parallel to the streamwise direction, called end-walls, as well as upstream and downstream walls. A primary vortex and secondary vortices including end-wall vortices are formed in the cavity. Because of the end-wall drag effect, the averaged mean-flow kinetic energy in the cavity is smaller than that in an urban street canyon that is open in the along-canyon direction. A trajectory analysis shows that the end-wall vortices cause fluid particles to move in the spanwise direction, indicating that flow in the cavity is essentially three-dimensional. The iso-surfaces of the Okubo–Weiss criterion capture cavity vortices well. The pollutant concentration is high near the bottom of the upstream side in the case of continuous pollutant emission, whereas it is high near the center of the primary vortex in the case of instantaneous pollutant emission. To get some insight into the degree of pollutant escape from the cavity according to various meteorological factors, extensive numerical experiments with different ambient wind speeds and directions, inflow turbulence intensities, and cavity-bottom heating intensities are performed. For each experiment, we calculate the time constant, which is defined as the time taken for the pollutant concentration to decrease to e^?1 of its initial value. The time constant decreases substantially with increasing ambient wind speed, and tends to decrease with increasing inflow turbulence intensity and cavity-bottom heating intensity. The time constant increases as the ambient wind direction becomes oblique. High ambient wind speed is found to be the most crucial factor for ventilating the cavity, thus improving air quality in an urban cubical cavity.