Numerical simulation on multi-scale diffusion of CO2 injected in the deep ocean in a practical scenario

The direct injection of CO₂ into the deep ocean is one of the ways for the mitigation of the global warming. There is, however, a concern about its environmental impact near the injection point. To minimize its biological impact, it is necessary to make CO₂ disperse as fast as possible and it is thought that injection with pipes towed by moving-ships is effective for this purpose. Because the injection ships are planned to move in the site, the order of magnitude of which is 10² km, a mesoscale model is required to predict CO₂ fate in seawater. At the same time, it is required to predict the concentration precisely near the injection points, which move with the ships in the mesoscale domain. In this study, a multi-scale ocean model was developed to analyze the dispersion of CO₂ in the deep ocean: the model consists of a fixed mesoscale domain and 5 small-scale domains nesting in the mesoscale domain. Each small-scale domain involves 6 pipes and moves along with the trajectories of the injection ships. From the results of the present numerical simulation, the developed technique demonstrated its applicability as a tool to optimise the system to dilute CO₂ below some criterion of biological impact.     

Detection of dicofol and related pesticides in human breast milk from China, Korea and Japan

Previously, we demonstrated that the concentrations of DDTs were greater in breast milk collected from Chinese mothers than from Japanese and Korean mothers. To investigate dicofol as a possible source of the DDTs in human breast milk, we collected breast milk samples from 2007 to 2009 in China (Beijing), Korea (Seoul, Busan) and Japan (Sendai, Takarazuka and Takayama). Using these breast milk samples, we quantified the concentrations of dichlorobenzophenone, a pyrolysis product of dicofol (simply referred to as dicofol hereafter), dichlorodiphenyltrichloroethane and its metabolites (DDTs) using GC-MS. Overall, 12 of 14 pooled breast milk samples from 210 mothers contained detectable levels of dicofol (>0.1 ng g⁻¹ lipid). The geometric mean concentration of dicofol in the Japanese breast milk samples was 0.3 ng g⁻¹ lipid and significantly lower than that in Chinese (9.6 ng g⁻¹ lipid) or Korean breast milk samples (1.9 ng g⁻¹ lipid) (p < 0.05 for each). Furthermore, the ΣDDT levels in breast milk from China were 10-fold higher than those from Korea and Japan. The present results strongly suggest the presence of extensive emission sources of both dicofol and DDTs in China. However, exposure to dicofol cannot explain the large exposure of Chinese mothers to DDTs because of the trace levels of dicofol in the ΣDDTs. In the present study, dicofol was confirmed to be detectable in human breast milk. This is the first report to identify dicofol in human samples.     

Perfluorosulfonates and perfluorocarboxylates in snow and rain in Dalian,China

Samples of precipitation events (snow and rain) in Dalian, a typical coastal town in China, were analyzed for perfluorosulfonates (PFSAs) and perfluorocarboxylates (PFCAs) to investigate atmospheric contamination by these compounds. In the snow event on December 16, 2006, samples were collected from 21 different sites and in another 6 precipitation events, samples were collected from a single location. Four PFSAs (C4, C6, C8, C10) and seven PFCAs (C6–12) were analyzed. Among the homologues, perfluorooctane sulfonate (PFOS) concentrations were the highest with a geometric mean (GM) of 145 ng/L (n = 21) during the snow event on December 16, 2006, followed by perfluorooctanoate (PFOA) with a GM of 24.7 ng/L (n = 21). Concentrations of perfluorobutane sulfonate (PFBS), perfluorohexane sulfonate (PFHxS) and perfluoroheptanoate (PFHpA) were more than two orders of magnitude lower than that of PFOS. Other PFSAs and PFCAs were found to be below the limit of detection in all the samples. In other 6 precipitation events, PFSAs and PFCAs were detected approximately in the same order of magnitude in both snow and rain. The results indicate that wet deposition may be a potential transport mechanism of perfluorinated chemicals in the environment.     

Model prediction on the rise of pCO2 in uniform flows by leakage of CO2 purposefully stored under the seabed

A numerical study was conducted to predict pCO₂ change in the ocean on a continental shelf by the leakage of CO₂, which is originally stored in the aquifer under the seabed, in the case that a large fault connects the CO₂ reservoir and the seabed by an earthquake or other diastrophism. The leakage rate was set to be 6.025 × 10⁻⁴ kg/m²/sec from 2 m × 100 m fault band, which corresponds to 3800 t-CO₂/year, referring to the monitored seepage rate from an existing EOR field. The target space in this study was limited to the ocean above the seabed, the depth of which was 200 or 500 m. The computational domain was idealistically rectangular with the seabed fault-band perpendicular to the uniform flow. The CO₂ takes a form of bubbles or droplets, depending on the depth of water, and their behaviour and dissolution were numerically simulated during their rise in seawater flow. The advection–diffusion of dissolved CO₂ was also simulated. As a result, it was suggested that the leaked CO₂ droplets/bubbles all dissolve in the seawater before spouting up to the atmosphere, and that the increase in pCO₂ in the seawater was smaller than 500 μ atm.     

Spatial distribution and loading amounts of particle sorbed and dissolved perfluorinated compounds in the basin of Tokyo Bay

In this study, we analyzed over 30 types of PFCs, including precursors in both the dissolved phase and particle solid phase, in 50 samples of river water collected from throughout the Tokyo Bay basin. PFCs were detected in suspended solids (SSs) at levels ranging from <0.003-4.4 ng L(-1) (0.11-2470 ng g(-1) dry weight). The concentrations of PFCs in the SS were one to two order(s) of magnitude lower than those of PFCs in the dissolved phase. Relatively high levels of PFCs (total of 35 PFCs) in SS were observed in urbanized areas. The concentration of PFCAs, including PFOA and PFNA, were significantly correlated with the geographic index as artificial area (R(2) of the linear regression curve in a double logarithmic plot: 0.09-0.55). Conversely, PFOS and FOSA were significantly correlated with the arterial traffic area (R(2) in a double logarithmic plot: 0.29-0.55). Those spatial trends were similar to the trends in dissolved PFCs. We estimated the loading amount of PFCs into Tokyo Bay from six main rivers and found that more than 90% of the total PFCs reached Tokyo Bay in the dissolved phase. However, 40.0-83.5% of the long chain PFCAs (C12-C15), were transported as particle sorbed PFCs. Rain runoff events might increase the loading amount of PFCs in SS. Overall, the results presented herein indicate that greater attention should be given to PFCs, especially for longer chain PFCs in SS in addition to dissolved PFCs.     

Hydrothermal synthesis of meso/macroporous BiVO4 hierarchical particles and their photocatalytic degradation properties under visible light irradiation

An ordered hierarchical meso/macroporous monoclinic bismuth vanadate (BiVO₄) particle was fabricated for the first time by a simple two-step melamine template hydrothermal method followed by calcination. The physiochemical parameters of as-prepared porous materials were characterized by means of X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Raman, Barrett–Emmett–Teller, and UV–vis techniques. The nitrogen adsorption–desorption measurement and pore size distribution curve suggest that meso/macropores exist in these hierarchical microarchitectures. Further, it is found that melamine plays a significant role in the formation of porous BiVO₄ particles, and when a known amount of melamine was added, the surface area and pore size of such porous BiVO₄ particles were increased. The photocatalytic activities of the as-prepared hierarchical BiVO₄ samples were measured for the photodegradation of Congo red aqueous dye solution under visible light irradiation. Surprisingly, the porous BiVO₄ particles showed outstanding photocatalytic activities than polycrystalline BiVO₄ sample. The possible enhancement of such catalytic performance has also been further discussed.     

Sources and distribution of hexabromocyclododecanes (HBCDs) in Japanese river sediment

The distribution of hexabromocyclododecane (HBCD) in the sediment of three Japanese rivers with different characteristics (i.e., population and potential source in the catchment) was investigated and compared with the results estimated using a multimedia fate model (ChemCAN). High concentrations of HBCD in sediments in the range of 134-2060 ng g(-1) were found in a river receiving textile wastewater. This contrasted with the much lower concentrations (0.8-4.8 ng g(-1)) observed for an urban river (with a surrounding population of 1.8 million). The medians of observed HBCD concentrations in each river were close to those estimated based on the assumed input source (e.g., 1810 ng g(-1) for the observed median concentration, and 1436 ng g(-1) for the estimation, in the Kuzuryu River). These results demonstrated the importance of considering source contributions of HBCD, including both industrial and consumer sources, to aquatic environments, for reliable risk management.     

Economic evaluation of sewage treatment processes in India

This paper evaluates the total annual cost including capital and operation and maintenance (O&M) costs for the up-flow anaerobic sludge blanket (UASB) and waste stabilization pond (WSP) systems operated in India. It also compares UASB and WSP systems with the activated sludge process (ASP) and biological aerated filter (BAF) systems in terms of total annual cost and chemical oxygen demand (COD) removal cost by assuming various annual interest rates and land prices. It was found that the relationship between capital and O&M costs per unit size of a UASB or WSP system and its treatment capacity can be established by a first-order equation. The relation between the cost of organic removal and capital or O&M cost for various sewage treatment systems at various annual interest rates revealed that, for the Indian context, UASB could be the most suitable option in terms of expenses and treatment efficiency.     

Production of biologically safe digested manure for land application by a full-scale biogas plant with heat-inactivation

Inactivation of indigenous indicator micro-organisms such as faecal coliforms, coliphages, and faecal streptococci was investigated in a full-scale biogas plant that mainly digested cow manure. The biogas plant consisted principally of a feed reservoir, fermentation tank (37 degrees C), heat-inactivation process (70 degrees C), and five reservoirs for the heat-inactivated, digested manure that was used by a local livestock farmer as liquid fertilizer. Although all the indicators tended to exhibit stepwise decreases with each stage of treatment, coliphages were found to be more capable of surviving than faecal coliforms and faecal streptococci under mesophilic anaerobic conditions as well as high temperature conditions (heat-inactivation at 70 degrees C). Liquid fertilizer produced at the biogas plant had faecal coliform densities less than the stipulations of the US EPA 40 CFR 503 Class A limits. Heat-inactivation tests indicated that although coliphages exhibited more tolerance than other bacterial indicators between 37 and 70 degrees C, they were more sensitive to continuous temperature increase than faecal coliforms and faecal streptococci.