Effect of exposure test conditions on leaching behavior of inorganic contaminants from recycled materials for roadbeds

Throughout the utilization of recycled materials, weathering factors such as humidity, gas composition and temperature have the potential to change the material properties and enhance the release of inorganic contaminants. In this research, the effects of weathering factors on recycled gravel materials for roadbeds were evaluated by applying three kinds of accelerating exposure tests: freezing–melting cycle test, carbonation test, and dry–humid cycle test. The effects of exposure tests were determined by X-ray diffraction (XRD) analysis and serial batch leaching test, making it possible to identify the change in release mechanisms. Sixteen elements, mainly metals, were investigated. Tested samples were molten slag from municipal solid waste, molten slag from automobile shredded residue, and crushed natural stone.After the exposure tests, the increase of cumulative release in the leaching test was generally less than 2.0 times that of the samples without the exposure test. Among the three test conditions, freezing–melting showed a slightly higher effect of enhancing the release of constituents. XRD analysis showed no change in chemical species. From these results, it was determined that the stony samples were stable enough so that their properties were not significantly changed by the exposure tests.     

High performance liquid chromatographic determination of pesticides in soluble phase and suspended phase in river water

A high performance liquid chromatographic method has been developed to determine pesticides in river water as both dissolved phase and suspended phase. The target pesticides were eight herbicides, asulam, diuron, flazasulfuron, linuron, MCPB, mecoprop, pyrazosulfuron‐ethyl and siduron, and two fungicides, oxine‐copper and thiram. The pesticides in filtered river water were extracted with styrene‐divinylbenzene copolymer and were eluted with acetonitrile. The pesticides on suspended solids were extracted ultrasonically with acetonitrile. Each eluate was concentrated and analyzed by HPLC with multiwavelength detector. Recoveries of the pesticides in the overall procedure of this method were 78–114% for filtered river water and 75–107% for suspended solids. The limits of detection in water and suspended solids ranged from 0.1 to 0.9 μg/L and 1 to 7 μg/g, respectively. Pesticide distribution between soluble phase and suspended phase in river water was measured by this method.     

Honeybee foragers adjust crop contents before leaving the hive

Upon leaving the hive, foragers carry a small amount of honey, which they subsequently consume to generate energy for flight. We investigated the relationship between waggle-phase duration and crop volume in foragers (both dancers and dance followers) leaving the hive. Our findings indicate that these variables were positively correlated in the two types of bee, suggesting that they were able to adjust the amount of food that they carry depending on the distance to a food source. We also found that dance followers left the hive with a larger amount of honey than dancers. We suggest two possible explanations: (1) dance followers have less information about the location of the food source than dancers, who have a better knowledge of the surrounding area; or (2) honeybees lack a precise calibration method for estimating energy needs from waggle-run duration. The effect of foraging experience was confirmed: bees decreased their honey load at departure with repeated trips to a sugar-syrup feeder. Honeybees showed a different pattern of change when the feeder provided soybean flour as a pollen substitute, possibly because honeybees use honey not only as an energy source but also as “glue” to form “balls” of pollen on their hind legs. Based on our observations that followers of sugar-syrup foragers carry a different amount of honey in their crop than followers of soybean-followers, we suggest that waggle dancers also convey information concerning food type.     

Geochemical provenance and spatial distribution of fluoride in groundwater of Mayo Tsanaga River Basin, Far North Region, Cameroon: implications for incidence of fluorosis and optimal consumption dose

The 500,000 inhabitants of Mayo Tsanaga River Basin are vulnerable to a “silent” fluorosis from groundwater consumption. For the first time, the groundwater is investigated for the purpose of identifying the provenance of fluoride and estimating an optimal dose of fluoride in the study area. Based on the fluoride content of groundwater, fluorine and major oxides abundances in rocks from the study area, mean annual atmospheric temperature, and on-site diagnosis of fluorosis in children, the following results and conclusions are obtained: Fluoride concentration in groundwater ranges from 0.19 to 15.2 mg/l. Samples with fluoride content of <1.5 mg/l show Ca–HCO₃ signatures, while those with fluoride >1.5 mg/l show a tendency towards Na-HCO₃ type. Fluor-apatite and micas in the granites were identified as the main provenance of fluoride in the groundwater through water-rock interactions in an alkaline medium. The optimal fluoride dose in drinking water of the study area should be 0.7 mg/l, and could be adjusted downward to a level of 0.6 mg/l due to the high consumption rate of groundwater, especially during drier periods.     

Numerical analysis of gas explosion inside two rooms connected by ducts

Simulations of gas explosion of hydrogen/air mixture inside two rooms connected by ducts are carried out. Scalar transport chemical reaction model and LES turbulence model are utilized to reduce the calculation load and to conduct real-scale analysis. The effects of ignition source locations and volume of ignited room are analyzed, and the time history of pressure and rate of pressure rise in each room are focused in this study. When the volume of the ignited room is larger than the other room, the high pressure from the other room causes a force to act on the partition to the ignited room. This study indicates that the current technique can predict specific features of gas explosions inside two rooms connected by the ducts.     

End-of-life vehicle recycling and automobile shredder residue management in Japan

The Japanese Government introduced the Law on Recycling of End-of-Life Vehicles (ELV Recycling Law) in 2002. This law requires manufacturers to retrieve chlorofluorocarbons (CFCs), airbags, and automobile shredder residue (ASR) from ELVs and to properly recycle the remaining materials. This framework is compared with European ELV directives. Pilot-scale incineration plant testing has revealed a greater formation of by-product persistent organic pollutants (POPs) during the primary combustion of ASR compared to normal municipal solid waste. This may be attributed to the abundance of chlorine, Cu, and Fe in ASR, as Cu and Fe have been found to catalyze the formation of POPs under certain conditions. However, most by-product POPs were destroyed by the secondary combustion, and almost all were removed after flue gas treatment. The direct melting system is a shaft-type gasification and melting technology that has proved effective in many municipal solid waste applications. This system can be applied to ASR recycling for effective decomposition of brominated flame retardants and polybrominated dioxins.     

The dynamics of mercury around an artisanal and small-scale gold mining area,Camarines Norte,Philippines

Environmental Science and Pollution Research - To elucidate the dynamics of mercury emitted and released by artisanal and small-scale gold mining (ASGM) activity and to estimate its impact on the...     

Variability and reliability of POP concentrations in multiple breast milk samples collected from the same mothers

Risk assessment of infant using a realistic persistent organic pollutant (POP) exposure through breast milk is essential to devise future regulation of POPs. However, recent investigations have demonstrated that POP levels in breast milk collected from the same mother showed a wide range of variation daily and monthly. To estimate the appropriate sample size of breast milk from the same mother to obtain reliable POP concentrations, breast milk samples were collected from five mothers living in Japan from 2006 to 2012. Milk samples from each mother were collected 3 to 6 times a day through 3 to 7 days consecutively. Food samples as the duplicated method were collected from two mothers during the period of breast milk sample collection. Those were employed for POP (PCBs, DDTs, chlordanes, and HCB) analysis. PCB concentrations detected in breast milk samples showed a wide range of variation which was maximum 63 and 60% of relative standard deviation (RSD) in lipid and wet weight basis, respectively. The time course trend of those variations among the mothers did not show any typical pattern. A larger amount of PCB intake through food seemed to affect 10 h after those concentrations in breast milk in lipid weight basis. Intraclass correlation coefficient (ICC) analyses indicated that the appropriate sample size for good reproducibility of POP concentrations in breast milk required at least two samples for lipid and wet weight basis.     

Navigating Institutional Challenges: Design to Enable Community Participation in Social Learning for Freshwater Planning

Social learning is a process suited to developing understanding and concerted action to tackle complex resource dilemmas, such as freshwater management. Research has begun to recognise that in practice social learning encounters a variety of institutional challenges from the shared habits and routines of stakeholders (organised by rules, norms and strategies) that are embedded in organisational structures and norms of professional behaviour. These institutional habits and routines influence the degree of willingness to engage with stakeholders, and expectations of behaviours in social learning processes. Considering this, there has been a call to understand how institutions influence social learning and emergent outcomes. We addresses this by presenting a heuristic for implementing social learning cognisant of institutional context to answer three questions: (i) How institutional influences impact implementation of social learning design; (ii) how implementation of social learning design modifies institutions influencing social learning; and (iii) how these changes in design and institutions together shape social learning outcomes? To answer these questions a freshwater planning exercise was designed, implemented and evaluated as a social learning process with community groups in two New Zealand catchments. Incorporating participatory reflection enabled the project team to modify social learning design to manage institutional influences hindering progress toward outcomes. Findings emphasise that social learning is underpinned by participants’ changing assumptions about what constitutes the institution of learning itself—from instruction to a dynamic, collective and emergent process. Reflecting on these assumptions also challenged participants’ expectations about their own and others’ behaviours and roles in freshwater planning.     

The stability of butyltin compounds in a dredged heavily-contaminated sediment

A treatment process for marine sediment heavily contaminated with tributyltin (TBT) was designed that included dehydrating, sunlight drying and dumping processes. The time course in butyltin (BTs) compounds, TBT, dibutyltin (DBT) and monobutyltin concentrations were investigated in the sediment treated under various conditions (light (UV, sunlight and light exclusion), moisture (air-drying and water saturation) and wetting and drying cycles). Significant changes in all the BT compound concentrations with time were not found regardless of the sediment conditions for light and moisture. The results indicated the high stabilities of TBT and DBT in the sediments versus light and moisture condition changes, probably taking place in the treatment process. It is also estimated that the BTs in the sediment are resistant to photo-degradation and biochemical degradation and their half lives are relatively long. In contrast, the decreases in the TBT and DBT were observed during the wetting and drying cycle treatment for the water saturated sediment both during exposure to sunlight and under a dark condition. This result suggested the hypothesis that the TBT degradation could be accelerated by the high microbial activity induced by the moisture changing treatments.