Minoru Yoneda

Source discrimination of heavy metals in sediment and water of To Lich River in Hanoi City using multivariate statistical approaches

The concentrations of Mn, Fe, Ni, Cr, Cu, Pb, Zn, As, and Cd were determined to evaluate the level of contamination of To Lich River in Hanoi City. All metal concentrations in 0–10-cm water samples, except Mn, were lower than the maximum permitted concentration for irrigation water standard. Meanwhile, concentrations of As, Cd, and Zn in 0–30-cm sediments were likely to have adverse effects on agriculture and aquatic life. Sediment pollution assessment was undertaken using enrichment factor and geoaccumulation index (Igeo). The Igeo results indicated that the sediment was not polluted with Cr, Mn, Fe, and Ni, and the pollution level increased in the order of Cu < Pb < Zn < As < Cd. Meanwhile, significant enrichment was shown for Cd, As, Zn, and Pb. Cluster and principal component analyses suggest that As and Mn in sediment were derived from both lithogenic and anthropogenic sources, while Cu, Pb, Zn, Cr, Cd, and Ni originated from anthropogenic sources such as vehicular fumes for Pb and metallic discharge from industrial sources and fertilizer application for other metals.

Location of groundwater seepage points into a river by measurement of 222Rn concentration in water using activated charcoal passive collectors

Abstract A new method to measure 222 Rn concentration in water is described. This method is an application of the activated charcoal passive collector method, which is sometimes used for measurement of 222 Rn concentration in air. The model and the equation which express the quantity of 222 Rn adsorbed in activated charcoal in the collector were constructed, inspected experimentally, and proved to work well enough for the measurement of relative concentration of 222 Rn in water. We used this method to measure the 222 Rn concentration in water at ∼ 20 points in an actual river. Based on the fact that the concentration of 222 Rn in ground water is generally much higher than that of surface water, we found several possible groundwater seepage points along the river. For the absolute measurement of 222 Rn concentration in water by this method, it would also be necessary to investigate the effect of temperature on the quantity of 222 Rn collected in a collector.

Future projection of radiocesium flux to the ocean from the largest river impacted by Fukushima Daiichi Nuclear Power Plant

Following the initial fall out from Fukushima Dai-ichi Nuclear Power Plant (FDNPP), a significant amount of radiocesium has been discharged from Abukuma River into the Pacific Ocean. This study attempted to numerically simulate the flux of radiocesium into Abukuma River by developing the multiple compartment model which incorporate the transport process of the radionuclide from the ground surface of the catchment area into the river, a process called wash off. The results from the model show that the sub-basins with a high percentage of forest area release the radionuclides at lower rate compared to the other sub-basins. In addition the results show that the model could predict the seasonal pattern of the observed data. Despite the overestimation observed between the modeled data and the observed data, the values of R2 obtained from 137Cs and 134Cs of 0.98 and 0.97 respectively demonstrate the accuracy of the model. Prediction of the discharge from the basin area for 100 years after the accident shows that, the flux of radiocesium into the Pacific Ocean is still relatively high with an order of magnitude of 109 bq.month−1 while the total accumulation of the discharge is 111 TBq for 137Cs and 44 TBq for 134Cs.

Effect of particle size on risk assessment of direct soil ingestion and metals adhered to children's hands at playgrounds.

The quantity of heavy metals in soil is measured after 2-mm sieving in Japan for risk assessment of direct soil ingestion. A study was conducted on the relationship between the size of soil particles and quantity of heavy metals in soil, and the particle-size distribution of soil adhered to childrens hands, and the risks of direct intake of soil considering the particle sizes ingested were evaluated. The results showed that smaller particles had a tendency to contain more heavy metals than bigger ones, that the particle size of approximately 90% of the soil particles from playgrounds adhered to childrens hands was less than 100 μm, and that 2-mm sieving in preparation for measuring heavy metal content caused underestimation of the risk of direct soil intake. The amount of heavy metals on childrens hands after playing outside was investigated. Various metals and soil were adhered to their hands, and the amount of soil adhered could be estimated from the concentration of metals. To develop accurate risk assessment, the particle-size distribution of ingested soil and more detailed scenarios of soil intake are necessary.

Spatial analysis and source profiling of beta-agonists and sulfonamides in Langat River basin, Malaysia.

Beta-agonists and sulfonamides are widely used for treating both humans and livestock for bronchial and cardiac problems, infectious disease and even as growth promoters. There are concerns about their potential environmental impacts, such as producing drug resistance in bacteria. This study focused on their spatial distribution in surface water and the identification of pollution sources in the Langat River basin, which is one of the most urbanized watersheds in Malaysia. Fourteen beta-agonists and 12 sulfonamides were quantitatively analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). A geographic information system (GIS) was used to visualize catchment areas of the sampling points, and source profiling was conducted to identify the pollution sources based on a correlation between a daily pollutant load of the detected contaminant and an estimated density of human or livestock population in the catchment areas. As a result, 6 compounds (salbutamol, sulfadiazine, sulfapyridine, sulfamethazine, sulfadimethoxine and sulfamethoxazole) were widely detected in mid catchment areas towards estuary. The source profiling indicated that the pollution sources of salbutamol and sulfamethoxazole were from sewage, while sulfadiazine was from effluents of cattle, goat and sheep farms. Thus, this combination method of quantitative and spatial analysis clarified the spatial distribution of these drugs and assisted for identifying the pollution sources.

Characterization of Pathogenic Escherichia coli in River Water by Simultaneous Detection and Sequencing of 14 Virulence Genes

The occurrence of pathogenic Escherichia coli in environmental waters increases the risk of waterborne disease. In this study, 14 virulence genes in 669 E. coli isolates (549 isolates from the Yamato River in Japan, and 30 isolates from each of the following hosts: humans, cows, pigs, and chickens) were simultaneously quantified by multiplex PCR and dual index sequencing to determine the prevalence of potentially pathogenic E. coli. Among the 549 environmental isolates, 64 (12%) were classified as extraintestinal pathogenic E. coli (ExPEC) while eight (1.5%) were classified as intestinal pathogenic E. coli (InPEC). Only ExPEC-associated genes were detected in human isolates and pig isolates, and 11 (37%) and five (17%) isolates were classified as ExPEC, respectively. A high proportion (63%) of cow isolates possessed Shiga-toxin genes (stx1 or stx2) and they were classified as Shiga toxin-producing E. coli (STEC) or enterohemorrhagic E. coli (EHEC). Among the chicken isolates, 14 (47%) possessed iutA, which is an ExPEC-associated gene. This method can determine the sequences as well as the presence/absence of virulence genes. By comparing the sequences of virulence genes, we determined that sequences of iutA were different among sources and may be useful for discriminating isolates, although further studies including larger numbers of isolates are needed. Results indicate that humans are a likely source of ExPEC strains in the river.

The dynamic performances of DDTs in the environment and Japanese exposure to them: A historical perspective after the ban

The fugacity model for evaluating DDTs dynamic performances in the environment was combined with the dietary exposure evaluation model, including the contribution of imported food, to develop the macroscopic mathematical model relating DDTs in the environment with the health risks of the reference Japanese. The model validity was examined by comparing the simulated DDTs concentrations in environmental media, various kinds of food, and dietary intake with those observed. Numerical simulations were done for the past half and future of one century to evaluate the effect of the DDTs usage prohibition in 1970 in Japan. The major results obtained under the limits considered are as follows. The DDTs concentrations in environmental media, various kinds of foods, and the dietary intake showed the steady exponential decrease after the DDTs usage prohibition in 1970. The DDE/DDTs ratio is larger in the higher position in an ecological system, and increased steadily with time. The critical exposure of DDTs occurred through animal product intake until 1960; after 1990 marine product intake caused the most exposure. The estimated DDTs intake was evaluated to be less than the PTDI and RfD. The annual excess cancer induction risk due to the annual dietary intake of DDTs was the largest at the level of (0.5 - 2.0) x 10(-6) (1/yr) in the early 1970s. The effect of the DDT usage prohibition on dietary exposure reduction was expected to appear after about 20 years. The life-span excess cancer induction risk was conservatively estimated to be larger than 10(-5) (1/lifespan) for the reference Japanese who were born before 1970. The DDTs usage prohibition in 1970 was effective to reduce the life-span cancer risk under the 10(-5) level.

Characterization and source profiling of volatile organic compounds in indoor air of private residences in Selangor State, Malaysia

Volatile Organic Compounds (VOCs) in indoor air were investigated at 39 private residences in Selangor State, Malaysia to characterize the indoor air quality and to identify pollution sources. Twenty-two VOCs including isomers (14 aldehydes, 5 aromatic hydrocarbons, acetone, trichloroethylene and tetrachloroethylene) were collected by 2 passive samplers for 24h and quantitated using high performance liquid chromatography and gas chromatography mass spectrometry. Source profiling based on benzene/toluene ratio as well as statistical analysis (cluster analysis, bivariate correlation analysis and principal component analysis) was performed to identify pollution sources of the detected VOCs. The VOCs concentrations were compared with regulatory limits of air quality guidelines in WHO/EU, the US, Canada and Japan to clarify the potential health risks to the residents. The 39 residences were classified into 2 groups and 2 ungrouped residences based on the dendrogram in the cluster analysis. Group 1 (n=30) had mainly toluene (6.87±2.19μg/m3), formaldehyde (16.0±10.1μg/m3), acetaldehyde (5.35±4.57μg/m3) and acetone (11.1±5.95μg/m3) at background levels. Group 2 (n=7) had significantly high values of formaldehyde (99.3±10.7μg/m3) and acetone (35.8±12.6μg/m3), and a tendency to have higher values of acetaldehyde (23.7±13.5μg/m3), butyraldehyde (3.35±0.41μg/m3) and isovaleraldehyde (2.30±0.39μg/m3). The 2 ungrouped residences showed particularly high concentrations of BTX (benzene, toluene and xylene: 235μg/m3 in total) or acetone (133μg/m3). The geometric mean value of formaldehyde (19.2μg/m3) exceeded an 8-hour regulatory limit in Canada (9μg/m3), while those in other compounds did not exceed any regulatory limits, although a few residences exceeded at least one regulatory limit of benzene or acetaldehyde. Thus, the VOCs in the private residences were effectively characterized from the limited number of monitoring, and the potential health risks of the VOCs exposure, particularly formaldehyde, should be considered in the study area.

Effect of surfactants on the aggregation and stability of TiO2 nanomaterial in environmental aqueous matrices

The high likelihood of the coexistence of surfactants and engineered nano-materials (ENMs) in aqueous environments redoubles the need to study the effects of surfactants on the behavior and transport of nano-materials. In this study, we chose anionic sodium dodecyl sulfate (SDS) and nonionic nonylphenol ethoxylate (NPEO, Tergitol NP-9) to study the effect of surfactants on the behaviors of a typical TiO2 ENM in water environment. An adsorption isotherm and zeta potential study showed that both surfactants could be adsorbed onto the surface of nano-TiO2 but that only SDS can significantly decrease the zeta potential of TiO2. For a better simulation of the dynamic natural water environment, we conducted a 24-h batch experiment to study the aggregation behaviors of nano-TiO2 in the presence of SDS or NP-9 surfactants and recorded the sedimentation of the aggregates in solutions containing the surfactants over a 24h-period. SDS and NP-9 both reduced the growth of the TiO2 aggregates and retarded the aggregate sedimentation at surfactant concentrations ≥0.015% (w:v). The aggregation of TiO2 was far more remarkable in six environmental water matrices from different natural origins than in Milli-Q water, mainly because of the relatively high ionic strength of the former. The introduction of surfactants, however, still retarded the aggregation and sedimentation of TiO2 in the six environmental water matrices. SDS exerted a stronger reductive effect than NP-9. This study reveals that the presence of surfactants may increase the bioavailability and environmental risk of nanomaterial contaminants by retarding the aggregation and promoting the transport of nanomaterials in natural aqueous environments.

Functional-dependent and size-dependent uptake of nanoparticles in PC12

It is suggested that the uptake of nanoparticles is changed by the particle size or the surface modification. In this study, we quantified the uptake of nanoparticles in PC12 cells exposed Quantum Dots with different surface modification or fluorescent polystyrene particles with different particle size. The PC12 cells were exposed three types of the Quantum Dots (carboxyl base-functionalized, amino base-functionalized or non-base-functionalized) or three types of the fluorescent particles (22 nm, 100 nm or 1000 nm) for 3 hours. The uptake of the nanoparticles was quantified with a spectrofluorophotometer. The carboxyl base-functionalized Quantum Dots were considerably taken up by the cells than the non-base-functionalized Quantum Dots. Conversely, the amino base-functionalized Quantum Dots were taken up by the cells less frequently than the non-base-functionalized Quantum Dots. The particle number of the 22 nm-nanoparticles taken up by the cells was about 53 times higher than the 100 nm-particles. However, the particle weight of the 100 nm-particles taken up by the cells was higher than that of the 22 nm-nanoparticles. The 1000 nm-particles were adhered to the cell membrane, but they were little taken up by the cells. We concluded that nanoparticles can be taken up nerve cells in functional-dependent and size-dependent manners.