Photodegradation of hexachlorobenzene and theoretical prediction of its degradation pathways using quantum chemical calculation

Experimentally determined photodegradation pathways of hexachlorobenzene (HCB), a chlorinated aromatic compound, in hexane, 2-propanol (IPA), and methanol were compared with those predicted by quantum chemical calculation based on density functional theory (DFT), and the adequacy of the prediction method was evaluated. The experimental main degradation pathways of HCB were virtually the same for the three solvents and also agreed with the predicted main degradation pathways. In the DFT method, the main degradation product was the dechlorinated benzene at the position where the C-Cl bond was predicted to have the lowest bond dissociation energy. This result suggested that the photodechlorination pathways of chlorinated aromatic compounds could be predicted by comparing the bond dissociation energies calculated with the DFT method.     

Abiotic reduction of antimony(V) by green rust (Fe(4)(II)Fe(2)(III)(OH)(12)SO(4).3H(2)O)

Green rust (Fe(4)(II)Fe(2)(III)(OH)(12)SO(4).3H(2)O) is an intermediate phase in the formation of iron (oxyhydr)oxides such as goethite, lepidocrocite, and magnetite. It is widely considered that green rust occurs in many soil and sediment systems. Green rust has been shown to reduce sorbed Se(VI), Cr(VI), and U(VI). In addition, it is also reported that green rust does not reduce As(V) to As(III). In this study, we have investigated for the first time the interaction between Sb(V) and green rust using XAFS and HPLC-ICP-MS. Most of the added Sb(V) was adsorbed on green rust, and Sb(III), a reduced form, was observed in both solid and liquid phases. Thus, it was shown that green rust has high affinity for Sb(V), and that Sb(V) was reduced to more toxic Sb(III) by green rust despite the high stability of the Sb(V) species even under reducing condition as reported in previous studies. Therefore, green rust can be one of the most important reducing agents for Sb(V), which can influence the Sb mobility in suboxic environments where green rust is formed.     

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...     

The effects on Thailand of China’s import restrictions on waste: measures and challenges related to the international recycling of waste plastic and e-waste

Journal of Material Cycles and Waste Management - This paper has outlined the measures and challenges facing Thailand, which was forced to address a surge in imports of plastic waste and e-waste...     

Analysis on the influence of forest soil characteristics on radioactive Cs infiltration and evaluation of residual radioactive Cs on surfaces

We investigated the depth profiles of radioactive Cs, ignition loss, and cation exchange capacity (CEC) in five types of forest soils sampled using scraper plates. We then simulated the monitored depth profiles in a compartment model, taking ignition loss as a parameter based on experimental results showing a positive correlation between ignition loss and the CEC. The calculated values were comparable with the monitored values, though some discrepancy was observed in the middle of the soil layer. Based on decontamination data on the surface dose rate and surface contamination concentration, we newly defined a surface residual index (SRI) to evaluate the residual radioactive Cs on surfaces. The SRI value tended to gradually decrease in forests and unpaved roads and was much smaller in forests and on unpaved roads than on paved roads. The radioactive Cs was assumed to have already infiltrated underground 18 months after the nuclear power plant accident, and the sinking was assumed to be ongoing. The SRI values measured on paved roads suggested that radioactive Cs remained on the surfaces, though a gradual infiltration was observed towards the end of the monitoring term. The SRI value is thought to be effective in grasping the rough condition of residual radioactive Cs quickly at sites of decontamination activity in the field. The SRI value may be serviceable for actual contamination works after further research is done to elucidate points such as the relation between the SRI and the infiltration of radioactive Cs in various types of objects.     

Receptor modeling of source apportionment of Hong Kong aerosols and the implication of urban and regional contribution

Understanding the spatial–temporal variations of source apportionment of PM_2.5 is critical to the effective control of particulate pollution. In this study, two one-year studies of PM_2.5 composition were conducted at three contrasting sites in Hong Kong from November 2000 to October 2001, and from November 2004 to October 2005, respectively. A receptor model, principal component analysis (PCA) with absolute principal component scores (APCS) technique, was applied to the PM_2.5 data for the identification and quantification of pollution sources at the rural, urban and roadside sites. The receptor modeling results identified that the major sources of PM_2.5 in Hong Kong were vehicular emissions/road erosion, secondary sulfate, residual oil combustion, soil suspension and sea salt regardless of sampling sites and sampling periods. The secondary sulfate aerosols made the most significant contribution to the PM_2.5 composition at the rural (HT) (44 ± 3%, mean ± 1σ standard error) and urban (TW) (28 ± 2%) sites, followed by vehicular emission (20 ± 3% for HT and 23 ± 4% for TW) and residual oil combustion (17 ± 2% for HT and 19 ± 1% for TW). However, at the roadside site (MK), vehicular emissions especially diesel vehicle emissions were the major source of PM_2.5 composition (33 ± 1% for diesel vehicle plus 18 ± 2% for other vehicles), followed by secondary sulfate aerosols (24 ± 1%). We found that the contribution of residual oil combustion at both urban and rural sites was much higher than that at the roadside site (2 ± 0.4%), perhaps due to the marine vessel activities of the container terminal near the urban site and close distance of pathway for the marine vessels to the rural site. The large contribution of secondary sulfate aerosols at all the three sites reflected the wide influence of regional pollution. With regard to the temporal trend, the contributions of vehicular emission and secondary sulfate to PM_2.5 showed higher autumn and winter values and lower summer levels at all the sites, particularly for the background site, suggesting that the seasonal variation of source apportionment in Hong Kong was mainly affected by the synoptic meteorological conditions and the long-range transport. Analysis of annual patterns indicated that the contribution of vehicular emission at the roadside was significantly reduced from 2000/01 to 2004/05 (p < 0.05, two-tail), especially the diesel vehicular emission (p < 0.001, two-tail). This is likely attributed to the implementation of the vehicular emission control programs with the tightening of diesel fuel contents and vehicular emission standards over these years by the Hong Kong government. In contrast, the contribution of secondary sulfate was remarkably increased from 2001 to 2005 (p < 0.001, two-tail), indicating a significant growth in regional sulfate pollution over the years.     

Temporal variation of Be concentrations in atmosphere for 8 y from 2000 at Yamagata,Japan: solar influence on the Be time series

We have been continuously observing the daily ⁷Be concentrations in surface air at Yamagata, Japan (38.25° N, 140.35° E) since 2000. The yearly profile of the ⁷Be concentration indicates the variation in galactic cosmic rays owing to solar modulation. Over 8 y, the ⁷Be concentration, cosmic neutrons, and number of sunspots varied by 37.4%, 12.2%, and 92.8%, respectively. The influence of precipitation on the ⁷Be variability was approximately 5%. Hence, the yearly ⁷Be concentration was mainly varied by the solar modulation of the ⁷Be production rates. Based on the production rates found in an EXPACS simulation, the observed variability indicates ⁷Be transport from high latitudes. The daily ⁷Be concentrations have two significant periodic components of 19 d and 36 d. The 36-d component implies a relationship between the sun's rotation and the vertical transport of air masses under quiet solar activity.     

Estimation of contribution from non-point sources to perfluorinated surfactants in a river by using boron as a wastewater tracer

The contribution of non-point sources to perfluorinated surfactants (PFSs) in a river was evaluated by estimating their fluxes and by using boron (B) as a tracer. The utility of PFSs/B as an indicator for evaluating the impact of non-point sources was demonstrated. River water samples were collected from the Iruma River, upstream of the intake of drinking water treatment plants in Tokyo, during dry weather and wet weather, and 13 PFSs, dissolved organic carbon (DOC), total nitrogen (TN), and B were analyzed. Perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluoroheptanoate (PFHpA), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUA), and perfluorododecanoate (PFDoDA) were detected on all sampling dates. The concentrations and fluxes of perfluorocarboxylates (PFCAs, e.g. PFOA and PFNA) were higher during wet weather, but those of perfluoroalkyl sulfonates (PFASs, e.g. PFHxS and PFOS) were not. The wet/dry ratios of PFSs/B (ratios of PFSs/B during wet weather to those during dry weather) agreed well with those of PFS fluxes (ratios of PFS fluxes during wet weather to those during dry weather), indicating that PFSs/B is useful for evaluating the contribution from non-point sources to PFSs in rivers. The wet/dry ratios of PFOA and PFNA were higher than those of other PFSs, DOC, and TN, showing that non-point sources contributed greatly to PFOA and PFNA in the water. This is the first study to use B as a wastewater tracer to estimate the contribution of non-point sources to PFSs in a river.     

Analysis of adsorption processes of dissolved organic matter (DOM) on ferrihydrite using surrogate organic compounds

Environmental Science and Pollution Research - Ferrihydrite (Fh) has been recently used in water treatment for removing dissolved organic matter (DOM), but its governing interactions with...     

Conflict and collective action in Tonle Sap fisheries: adapting governance to support community livelihoods

This paper presents the results of action research conducted from 2009 to 2015 on the dynamics of resource conflict concerning fisheries and livelihoods in the Tonle Sap Lake, as well as the institutional context and strategies for institutional adaptation to address such conflicts equitably. Over the past 15 years, Cambodia has made significant advances in building the policy framework, regulations and institutions to support community‐based fisheries management and increase the sector's contribution to the rural economy. However, fundamental challenges of increased resource conflict and loss of livelihoods by the most vulnerable remain. Key sources of conflict include destructive and illegal fishing practices, clearing of flooded forests, competing uses of land and water, and overlapping resource claims. Addressing these challenges requires collective action by all key actors: local fishers, the private sector, civil society, development partners, and government from the local to the national level. We identify and elaborate upon four governance priorities: (1) clarify roles and responsibilities in fisheries management; (2) link civil society and government efforts in law enforcement; (3) strengthen partnerships for livelihoods development; and (4) integrate fisheries management into decentralised development planning.