Arsenic accumulation in duckweed (Spirodela polyrhiza L.): a good option for phytoremediation

Some unavoidable drawbacks of traditional technologies have made phytoremediation a promising alternative for removal of arsenic from contaminated soil and water. In the present study, the potential of an aquatic macrophyte Spirodela polyrhiza L. for phytofiltration of arsenic, and the mechanism of the arsenic uptake were investigated. The S. polyrhiza L. were grown in three test concentrations of arsenate and dimethylarsinic acid (DMAA) (i.e. 1.0, 2.0 and 4.0microM) with 0 (control), 100 or 500microM of phosphate. One control treatment was also set for each test concentrations of arsenic. The PO(4)(3-) concentration in control treatment was 0.02microM. When S. polyrhiza L. was cultivated hydroponically for 6d in culture solution containing 0.02microM phosphate and 4.0microM arsenate or DMAA, the arsenic uptake was 0.353+/-0.003micromolg(-1) and 7.65+/-0.27nmolg(-1), respectively. Arsenic uptake into S. polyrhiza L. was negatively (p<0.05) correlated with phosphate uptake when arsenate was applied to the culture solutions owing to similar in the sorption mechanism between AsO(4)(3-) and PO(4)(3-), and positively (p<0.05) correlated with iron uptake due to adsorption of AsO(4)(3-) onto iron oxides. Thus, the S. polyrhiza L. accumulates arsenic by physico-chemical adsorption and via the phosphate uptake pathway when arsenate was added to the solutions. These results indicate that S. polyrhiza L. would be a good arsenic phytofiltrator. In contrast, DMAA accumulation into S. polyrhiza L. was neither affected by the phosphate concentration in the culture nor correlated (p>0.05) with iron accumulation in plant tissues, which indicates that S. polyrhiza L. uses different mechanisms for DMAA uptake.     

Uptake and distribution of iodine in rice plants

Rice (Oryza sativa L.) plants were cultivated in an experimental field and separated at harvest into different components, including polished rice, rice bran, hull, straw, and root. The contents of iodine in these components and the soil were determined by inductively coupled plasma-mass spectrometry and radiochemical neutron activation analysis, respectively. Iodine content varied by more than three orders of magnitude among the plant components. Mean concentration of iodine in the entire plants was 20 mg kg(-1) dry weight, and the concentration of iodine in the surface soil (0-20 cm depth) was 48 mg kg(-1). The highest concentration of iodine (53 mg kg(-1) dry weight) was measured in root and the lowest concentration (0.034 mg kg(-1) dry weight) in polished rice. While the edible component (polished rice) accounted for 32% of the total dry weight, it contained only 0.055% of iodine found in the entire rice plants. Atmospheric gaseous iodine (5.9 ng m(-3)) was estimated to contribute <0.2% of the total iodine content in the biomass of rice plants; therefore nearly all of the iodine in the rice plants was a result of the uptake of iodine from the soil. The content of iodine in the aboveground part of rice plants was 16 mg kg(-1) dry weight and the percentage of iodine transferred per cropping from the soil into the aboveground biomass corresponded to 0.27% (20 mg m(-2)) of the upper soil layer content.     

Yearly variation in characteristics and health risk of polycyclic aromatic hydrocarbons and nitro-PAHs in urban shanghai from 2010–2018

This study encompassed the regular observation of nine polycyclic aromatic hydrocarbons (PAHs) and three nitro-PAHs (NPAHs) in particulate matter (PM) in Shanghai in summer and winter from 2010 to 2018. The results showed that the mean concentrations of ?PAHs in summer decreased by 24.7% in 2013 and 18.1% in 2017 but increased by 10.2% in 2015 compared to the data in 2010. However, the mean concentrations of ?PAHs in winter decreased by 39.7% from 2010 (12.8 ± 4.55 ng/m³) to 2018 (7.72 ± 3.33 ng/m³), and the mean concentrations of 1-nitropyrene in winter decreased by 79.0% from 2010 (42.3 ± 16.1 pg/m³) to 2018 (8.90 ± 2.09 pg/m³). Correlation analysis with meteorological conditions revealed that the PAH and NPAH concentrations were both influenced by ambient temperature. The diagnostic ratios of PAHs and factor analysis showed that they were mainly affected by traffic emissions with some coal and/or biomass combustion. The ratio of 2-nitrofluoranthene to 2-nitropyrene was near 10, which indicated that the OH radical-initiated reaction was the main pathway leading to their secondary formation. Moreover, backward trajectories revealed different air mass routes in each sampling period, indicating a high possibility of source effects from the northern area in winter in addition to local and surrounding influences. Meanwhile, the mean total benzo[a]pyrene-equivalent concentrations in Shanghai in winter decreased by 50.8% from 2010 (1860 ± 645 pg/m³) to 2018 (916 ± 363 pg/m³). These results indicated the positive effects of the various policies and regulations issued by Chinese authorities.     

mRNA expression of a cadmium-responsive gene is a sensitive biomarker of cadmium exposure in the soil collembolan Folsomia candida

The gene expression of environmental organisms is useful as a biomarker of environmental pollution. One of its advantages is high sensitivity. We identified the cDNA of a novel cadmium-responsive gene in the soil collembolan Folsomia candida. The deduced protein, designated “metallothionein-like motif containing protein” (MTC), was cysteine-rich and contained a metallothionein-like motif with similarity to metallothionein, but had a much longer sequence than metallothionein and contained repeated sequences of amino acids. Expression of MTC mRNA was sensitively induced by cadmium exposure at 0.3 mg/kg of dry food, a concentration at which toxic effects are not observed, but expression was not affected by γ-ray exposure (an inducer of oxidative stress). These findings suggest that MTC is involved in cadmium-binding processes rather than in oxidative-stress responses. In conclusion, we suggest that gene expression of MTC may be a candidate biomarker for detecting low levels of cadmium contamination in soil.     

Relationship between traffic fatalities and drunk driving in Japan

OBJECTIVE: The present study was performed to clarify the relation between alcohol use and traffic fatalities in accidents involving motor vehicles in Japan. METHODS: Data on traffic accidents were collected from Fukuoka Prefectural Police records of traffic accidents which occurred in that prefecture between 1987 and 1996. Multiple logistic regression models were used to assess the effect of alcohol use on the risk of traffic-accident death. RESULTS: The data showed that 58,421 male drivers were involved in traffic accidents during the 10-year study period, and that 271 of these were killed as a result of the accident. Alcohol use was significantly associated with speed, seat belt use, time, and road form. Among male motorcar drivers, the odds ratio of alcohol use before driving, after adjusting for age, calendar year, time, and road form, was 4.08 (95% confidence interval, 3.08-5.40), which means that about 75% of fatalities (attributable risk percent among exposed) might have been prevented if drivers had not drunk before driving. CONCLUSIONS: Alcohol use before driving resulted in a 4.08-fold increase in the risk of death in a traffic accident. It is suggested that alcohol use is considered an important risk factor for fatality in traffic accidents.     

Formation of estrogenic products from environmental phthalate esters under light exposure

Phthalate esters (PEs) have been suspected to be environmental endocrine disruptors and the detailed mechanism remains unclear. The activities of these chemicals can be enhanced through chemical modification under the environmental conditions. We demonstrate that PEs acquire unequivocal estrogenic activity by light exposure. Through UV exposure of an aqueous PE solution, one active photoproduct, identified as 4-hydroxyPE (PE-4OH) based on its characteristic UV and mass spectra, was detected in an estrogen receptor alpha-dependent transactivation assay. PE-4OH was effectively generated by UV 290 nm. The PE-4OH production accompanied H2O2 generation in a UV dose-dependent manner. Both PE and UV irradiation were indispensable in the generation of H2O2. Addition of H2O2 to the PE solution increased PE-4OH production under UV irradiation. The PE-4OH production was also observed in the PE reaction with the Fenton reagent generating hydroxyl radical without UV irradiation. The proposed mechanism for PE-4OH production based on these results is such that by PE-mediated photosensitization H2O2 is generated from O2 and H+ and decomposed to hydroxyl radical, thus oxidizing the PE benzene ring. The PEs-4OH are remarkably active estrogenic products of PEs and would be involved in ER-mediated endocrine disruption.     

Does the housing market respond to information disclosure?: Effects of toxicity indices in Japan

The policy instruments that provide information on a firm’s or facility’s environmental performance, such as the U.S. Toxic Release Inventory (TRI) and the Pollutant Release and Transfer Register system (PRTRs) used in some European countries and Japan, play an important role in encouraging firms or facilities to improve their environmental performance, if investors, consumers and residents recognize their environmental performance. This study uses a hedonic approach to explore how the Japanese rental housing market responds to carcinogenic risk arising from releases and transfers of chemical substances produced and used at close facilities. We found that residents do not perceive carcinogenic risk generated more than 1.0 km away from their residence and that they seem to recognize the increased carcinogenic risk at distances from 0.5 km to 1.0 km away; a 1% increase in carcinogenic risk reduces the average rent by 0.0007%. The distance at which residents perceive the risk arising from such facilities is less than in previous studies. This suggests that the risk perception recognized in previous studies may capture the other externalities in addition to the chemical risk because the risk is measured by the distance.     

Ubiquity of parasporin-1 producers in <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> natural populations of Japan

Parasporin, a Bacillus thuringiensis parasporal protein, is unique in having a strong cytocidal activity preferential for human cancer cells. In this study, we characterized parasporin activities associated with three novel geographical isolates of B. thuringiensis. Parasporal inclusion proteins of the three isolates were highly toxic to human uterus cervix cancer cells (HeLa), but not to non-cancer uterine smooth muscle cells (UtSMC). Inclusions of the isolates lacked insect toxicity and hemolytic activity against sheep erythrocytes. Ouchterlony immunodiffusion tests revealed that the proteins of the three isolates are immunologically closely related to parasporin-1 (Cry31A), but dissimilar to the three other existing parasporin groups. Our results provide evidence that the parasporin-1-producing organism is a common member in B. thuringiensis populations occurring in natural environments of Japan.     

Modeling the influence of biogenic volatile organic compound emissions on ozone concentration during summer season in the Kinki region of Japan

Tropospheric ozone adversely affects human health and vegetation, and biogenic volatile organic compound (BVOC) emission has potential to influence ozone concentration in summer season. In this research, the standard emissions of isoprene and monoterpene from the vegetation of the Kinki region of Japan, estimated from growth chamber experiments, were converted into hourly emissions for July 2002 using the temperature and light intensity data obtained from results of MM5 meteorological model. To investigate the effect of BVOC emissions on ozone production, two ozone simulations for one-month period of July 2002 were carried out. In one simulation, hourly BVOC emissions were included (BIO), while in the other one, BVOC emissions were not considered (NOBIO). The quantitative analyses of the ozone results clearly indicate that the use of spatio-temporally varying BVOC emission improves the prediction of ozone concentration. The hourly differences of monthly-averaged ozone concentrations between BIO and NOBIO had the maximum value of 6 ppb at 1400 JST. The explicit difference appeared in urban area, though the place where the maximum difference occurred changed with time. Overall, BVOC emissions from the forest vegetation strongly affected the ozone generation in the urban area.