Transportation and fate of cationic surfactant in river water

The degradation, sorption, transportation and material balance of cationic surfactants discharged from domestic waste into river water was studied. Ion-pair solid-phase extraction behavior showed that the sorption of cationic surfactants as an ion-pair with anionic surfactant onto river sediment was so strong that little cationic surfactant was found in the bulk water. Cationic surfactant was found in river sediment at more than 500 times higher concentration than that in the bulk water. The degradation of the cationic surfactant was very slow in river water and much slower in the sediment. A material balance of cationic surfactant was estimated for a river running through Toyama City by measuring the flow rate and the concentration of cationic surfactant in the water at several points. It was found that more than 30% of cationic surfactant introduced to the river was lost during the river running through ca. 3 km in 3 h. This reduction probably comes from a quick transfer of the cationic surfactant from river water to sediment and water weed by means of adsorption or precipitation with suspending solids.     

Residual organic fluorinated compounds from thermal treatment of PFOA,PFHxA and PFOS adsorbed onto granular activated carbon (GAC)

Perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA) and perfluorooctane sulfonate (PFOS) adsorbed onto granular activated carbon (GAC) were thermally treated in N₂ gas stream. The purpose was to assess the fate of perfluoroalkyl and polyfluoroalkyl substances (PFASs) during thermal regeneration of GAC, which had been used for water treatment. Mineralized F, residual PFASs including short-chained species, and volatile organic fluorine (VOF) were determined. In a temperature condition of 700 °C, VOF were 13.2, 4.8, and 5.9 % as for PFOA, PFHxA, and PFOS. However, the VOF decreased to 0.1 %, if the GAC and off-gas were kept at 1000 °C. No PFASs remained in GAC at 700–1000 °C; at the same time, short-chained PFASs were slightly detected in the aqueous trapping of off-gas at 800 and 900 °C conditions. The destruction of PFASs on GAC could be perfect if the temperature is higher than 700 °C; however, the process is competitive against volatile escape from GAC. Destruction in gaseous phase needs a temperature as high as 1000 °C. Destruction of PFASs on the surface of GAC, volatile escape from the site, and thermolysis in gas phase should be considered, as to thermal regeneration of GAC.     

The effects of current water management practices on methane emissions in Japanese rice cultivation

Cultivated wetland rice fields are a source of methane (CH₄) emissions. To estimate CH₄ emissions and develop policies to reduce such emissions, information on water management at the farm level is crucial. It is known that farmers implement midseason drainage (MD) to increase rice yields and save water. However, little is known about whether MD is carried out in soils where CH₄ emissions are high and how part-time status will influence management. The objective of this study is to identify factors that determine MD implementation using a binomial logistic regression model based on a farm-level survey in Japan and to indicate possible changes in estimates of CH₄ emissions, accounting for current water management practices. The implementation rates were significantly higher where the soil types were classified as having the potential for high CH₄ emissions. Under current water management practices, the duration of MD and the percentage of continuous flooding were 5 to 7 days longer and approximately 7 % higher, respectively, than the values used by the Greenhouse Gas Inventory Office of Japan, which in turn are used to report greenhouse gas emissions to the United Nations Framework Convention on Climate Change. By accounting for current water conditions with the Tier 2 method, this study indicates that national estimates of CH₄ emissions from rice straw application areas could be lowered by 12.7 %. These results may contribute to the development of a mitigation policy that will help to further reduce CH₄ emissions.     

Sea bottom management in Japan

Cleanup of polluted sediment in several Japanese ports and harbors is descrbed. Cleanup is preceded by detailed examination of sediment and organism chemical concentrations. When Japanese government tentative standards for mercury, cadmium, or oganics are exceeded in these compartments of the environment, steps are taken to eliminate the pollution problem. Results or pollution countermeasures at Tokuyama-Kudamatsu port (mercury pollution) and Hachinohe port (organic pollution) are described in detail. Future research needs include the establishment of more refined and realistic sediment standards, detailed surveys of organic pollution in Japanese bays and inland seas, and addressing the persistent problem of eutrophication in these areas.     

Differences in the Spatial Variability Among CO2, CH4, and N2O Gas Fluxes from an Urban Forest Soil in Japan

The spatial variability of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) fluxes from forest soil with high nitrogen (N) deposition was investigated at a rolling hill region in Japan. Gas fluxes were measured on July 25th and December 5th, 2008 at 100 points within a 100 × 100 m grid. Slope direction and position influenced soil characteristics and site-specific emissions were found. The CO₂ flux showed no topological difference in July, but was significantly lower in December for north-slope with coniferous trees. Spatial dependency of CH₄ fluxes was stronger than that of CO₂ or N₂O and showed a significantly higher uptake in hill top, and emissions in the valley indicating strong influence of water status. N₂O fluxes showed no spatial dependency and exhibited high hot spots at different topology in July and December. The high N deposition led to high N₂O fluxes and emphasized the spatial variability.     

Nervous system disruption and concomitant behavioral abnormality in early hatched pufferfish larvae exposed to heavy oil

BACKGROUND AND OBJECTIVE: Spills of heavy oil (HO) over the oceans have been proven to have an adverse effect on marine life. It has been hypothesized that exposure of early larvae of sinking eggs to HO leads largely to normal morphology, whereas abnormal organization of the developing neural scaffold is likely to be found. HO-induced disruption of the nervous system, which controls animal behavior, may in turn cause abnormalities in the swimming behavior of hatched larvae. To clarify the toxicological effects of HO, we performed exposure experiments and morphological and behavioral analyses in pufferfish (Takifugu rubripes) larvae. EXPERIMENTAL PROCEDURE: Fertilized eggs of pufferfish were exposed to 50?mg/L of HO for 8?days and transferred to fresh seawater before hatching. The hatched larvae were observed for their swimming behavior, morphological appearance, and construction of muscles and nervous system. RESULTS AND DISCUSSION: In HO-exposed larvae, we did not detect any anomaly of body morphology. However, they showed an abnormal swimming pattern and disorganized midbrain, a higher center controlling movement. Our results suggest that HO-exposed fishes suffer developmental disorder of the brain that triggers an abnormal swimming behavior and that HO may be selectively toxic to the brain and cause physical disability throughout the life span of these fishes.     

Effect of aging time on the availability of freshly precipitated ferric hydroxide to coastal marine diatoms

Cell growth and iron uptake of the coastal marine diatoms Chaetoceros sociale and Thalassiosira weissflogii were studied in the presence of short-aged amorphous ferric hydroxide (am-Fe(III)) media. These were prepared by aging for 1 day, 3 days, and 3 weeks after adding a small amount of ferric iron acidic stock solution to autoclaved filtered seawater and were experimentally measured in culture experiments at 10°C for C. sociale and 20°C for T. weissflogii. The order of cell yields for both species was: 1-day aged am-Fe(III) >3-day aged am-Fe(III) >> 3-week aged am-Fe(III) media. The iron uptake rates by C. sociale during 0–1 day in 1 day and 3-day aged am-Fe(III) media were about two-thirds and one-fourths, respectively, lower than that in the direct Fe(III) input medium containing C. sociale into which an acidic Fe(III) stock solution was added directly. The longer aging time of am-Fe(III) in media results in reducing the supply of bioavailable iron in the media by the slower dissolution rate of am-Fe(III) with the longer aging time. These results suggest that the chemical and structural changes of freshly precipitated amorphous ferric hydroxide with short aging time affect their ability, such as iron solubility and dissolution rate to supply bioavailable iron for the phytoplankton growth. The chemical and structural conversion of solid iron phases with time is one of the most important processes in changing the supply of available iron to marine phytoplankton in estuarine and coastal waters and in iron fertilization experiments.     

Distribution coefficients (K d) of stable iodine in estuarine and coastal regions, Japan, and their relationship to salinity and organic carbon in sediments

The sediment–water distribution coefficient, K _d, is one of the most important parameters in radionuclide assessment models. In this study, we determined K _ds of stable iodine (I) in estuarine and coastal regions. We studied 16 estuarine and coastal regions of Japan and obtained I data on water and sediments. Data on salinity, pH, dissolved organic carbon and dissolved oxygen in water, and organic carbon (OC) in sediments were also obtained as estuarine variables. Determined K _ds of I in the Sagami River estuary decreased along the salinity gradient (salinity range, 0.1–33.8), indicating that salinity is one of the important factors controlling the K _d values; however, when the K _d values were compared among all the estuaries, the difference between minimum and maximum K _d values varied by about two orders of magnitude in a narrow salinity range of 30.0–34.4. A significant correlation between K _d value and OC content in sediments was observed in all the stations with a salinity of ≥30 except for stations in the Ishikari and Onga River estuaries. The exceptions are probably due to different sources of the sediments, which are explained by the results of relatively low I/OC ratios in sediments in those two estuaries, compared to the other estuaries. Thus, OC in sediments as well as salinity may be responsible for the variation of K _ds of I in the estuarine and coastal regions.     

Derivation of hazardous doses for amphibians acutely exposed to ionising radiation

Derivation of effect benchmark values for each taxonomic group, which has been difficult due to lack of experimental effects data, is required for more adequate protection of the environment from ionising radiation. Estimation of effects doses from nuclear DNA mass and subsequent species sensitivity distribution (SSD) analysis were proposed as a method for such a derivation in acute irradiation situations for assumed nuclear accident scenarios. As a case study, 5% hazardous doses (HD₅s), at which only 5% of species are acutely affected at 50% or higher lethality, were estimated on a global scale. After nuclear DNA mass data were obtained from a database, 50% lethal doses (LD₅₀s) for 4.8 and 36% of the global Anura and Caudata species, respectively, were estimated by correlative equations between nuclear DNA mass and LD₅₀s. Differences between estimated and experimental LD₅₀s were within a factor of three. The HD₅s obtained by the SSD analysis of these estimated LD₅₀s data were 5.0 and 3.1 Gy for Anura and Caudata, respectively. This approach was also applied to the derivation of regional HD₅s. The respective HD₅s were 6.5 and 3.2 Gy for Anura and Caudata inhabiting Japan. This HD₅ value for the Japanese Anura was significantly higher than the global value, while Caudata had no significant difference in global and Japanese HD₅s. These results suggest that this approach is also useful for derivation of regional benchmark values, some of which are likely different from the global values.