Bayesian Modeling of Enteric Virus Density in Wastewater Using Left-Censored Data

Stochastic models are used to express pathogen density in environmental samples for performing microbial risk assessment with quantitative uncertainty. However, enteric virus density in water often falls below the quantification limit (non-detect) of the analytical methods employed, and it is always difficult to apply stochastic models to a dataset with a substantially high number of non-detects, i.e., left-censored data. We applied a Bayesian model that is able to model both the detected data (detects) and non-detects to simulated left-censored datasets of enteric virus density in wastewater. One hundred paired datasets were generated for each of the 39 combinations of a sample size and the number of detects, in which three sample sizes (12, 24, and 48) and the number of detects from 1 to 12, 24 and 48 were employed. The simulated observation data were assigned to one of two groups, i.e., detects and non-detects, by setting values on the limit of quantification to obtain the assumed number of detects for creating censored datasets. Then, the Bayesian model was applied to the censored datasets, and the estimated mean and standard deviation were compared to the true values by root mean square deviation. The difference between the true distribution and posterior predictive distribution was evaluated by Kullback–Leibler (KL) divergence, and it was found that the estimation accuracy was strongly affected by the number of detects. It is difficult to describe universal criteria to decide which level of accuracy is enough, but eight or more detects are required to accurately estimate the posterior predictive distributions when the sample size is 12, 24, or 48. The posterior predictive distribution of virus removal efficiency with a wastewater treatment unit process was obtained as the log ratio posterior distributions between the posterior predictive distributions of enteric viruses in untreated wastewater and treated wastewater. The KL divergence between the true distribution and posterior predictive distribution of virus removal efficiency also depends on the number of detects, and eight or more detects in a dataset of treated wastewater are required for its accurate estimation.     

Viral Interference as a Factor of False-Negative in the Infectious Adenovirus Detection Using Integrated Cell Culture-PCR with a BGM Cell Line

Food and Environmental Virology - This study investigated the influence of viral interference on the detection of enteric viruses using the integrated cell culture (ICC)-PCR with a BGM cell line....     

A simple method to harness DC (direct current) electrical energy generated by bacterial activity

We developed a new system for collecting electrons generated by bacterial activity to supply DC (direct current) electrical energy. This system used eight titanium sub-electrodes (surface area of each sub-electrode: 189 cm²) connected to one central main titanium electrode (surface area of electrode: 1571 cm²). The distance between each sub-electrode and the main electrode was 30 cm. In an initial experiment, we collected electrons during composting cattle excreta, which was mixed with a commercially available microbial compost activator/starter. We analysed the relationships between the composting temperature and electrical current and voltage. Electrons were effectively collected and used successfully to obtain DC electrical energy. Generation of a stable voltage of approximately 0.5 V was clearly observed. This voltage was not related to compost temperature; however, the generated electrical current increased and decreased with compost temperature. The method was then used in a second experiment to collect electrons generated by bacterial activity in an agricultural field (area: 48 m²). Electrons in the field were effectively collected, and we measured a stable voltage of approximately 1.1 V and a stable current of approximately 0.7 mA. The system has the advantages of being simple, easily maintained, inexpensive, and applicable to large-scale agricultural fields.     

应用自动识别与定量分析数据库筛查黄河和长江水中有机污染物

采用气质联用分析,并应用自动识别与定量分析数据库(AIQS-DB)对黄河下游和长江下游水样中近1000种有机污染物进行了筛查.结果表明,黄河下游山东段和长江下游江苏段水样分别检出95种和121种化合物,主要包括正构烷烃、多环芳烃、酚类、硝基化合物、酞酸酯类、农药和药物等.其中,黄河和长江水样中正构烷烃平均浓度分别为1806ng/L和720ng/L;16种优控PAHs平均浓度分别为27ng/L和30ng/L;6种优控PAEs的平均浓度分别为77ng/L和2166ng/L;黄河和长江水样分别检出9种和17种农药.黄河各采样点间污染物浓度差别较大,而长江采样点间浓度相差较小.研究表明,气质联用结合AIQS-DB可有效用于区域性污染物的筛查.     

Integrated biogeochemical modelling of nitrogen load from anthropogenic and natural sources in Japan

This study proposed an integrated biogeochemical modelling of nitrogen loads from anthropogenic and natural sources in Japan. Firstly, the nitrogen load (NL) from different sources such as crop, livestock, industrial plant, urban and rural resident was calculated by using datasets of fertilizer utilization, population distribution, land use map, and social census. Then, the nitrate leaching from soil layers in farmland, grassland and natural conditions was calculated by using a terrestrial nitrogen cycle model (TNCM). The Total Runoff Integrating Pathways (TRIP) was used to transport nitrogen from natural and anthropogenic sources through river channels, as well as collect and route nitrogen to the river mouths. The forcing meteorological and hydrological data is a 30-year (1976–2005) dataset for Japan which were obtained by the land surface model, Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO). For the model validation, we collected total nitrogen (TN) concentration data from 59 rivers in Japan. As a comparison result, calculated TN concentration values were in good agreement with the observed ones, which shows the reliability of the proposed model. Finally, the TN loads from point and nonpoint sources were summarized and evaluated for 59 river basins in Japan. The proposed modelling framework can be used as a tool for quantitative evaluation of nitrogen load in terrestrial ecosystems at a national scale. The connection to land use and climate data provides a possibility to use this model for analysis of climate change and land use change impacts on hydrology and water quality.     

The effect of the increase in urban temperature on the concentration of photochemical oxidants

An atmospheric dispersion model, where the inputs of meteorological field were calculated using a meteorological model, was used to reproduce the observed air pollution conditions for the typical fine day in summer period, especially the concentration of the photochemical oxidants. As well, the effects of an increase in the urban temperature and VOC emissions on the concentration of photochemical oxidants were also considered. The following conclusions were drawn.The observed air pollution levels were well modeled by the atmospheric dispersion model using in this study, although modeled NO levels were slightly lower than the observed levels. An analysis of the temperature data showed that a 1 °C increase in temperature leads to a maximal photochemical oxidant concentration of 5.3 ppb, which is an increase of 11%. Additionally, the effect on the photochemical oxidant concentration due to an increase in the vegetation-derived VOCs was more than double the effect due to an increase in the photochemical reactions. It was found that the temperature and photochemical oxidant concentration were linearly related up to a temperature increase of 3 °C. When the temperature increases up to 3 °C, the concentration of photochemical oxidants increases by 19 ppb. An analysis of the effect of vegetation-derived VOCs on photochemical oxidant concentrations showed that, the concentration of photochemical oxidants was 30 ppb higher in the afternoon by the effect of vegetation-derived VOCs, so even in metropolitan areas with relatively little vegetation, vegetation-derived VOCs have a strong impact on photochemical oxidant concentrations.     

Current mode atomic force microscopy (C-AFM) study for local electrical characterization of conjugated polymer blends

A blend of regioregular poly(3-hexylthiophene) (P3HT) and poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2), which has the potential for polymer solar cells application, was prepared for current mode atomic force microscopy (C-AFM) measurements in this study. Phase-separated domains and the local electrical characteristics of P3HT/P(NDI2OD-T2) blends were investigated by the C-AFM.     

Respiratory uptake kinetics of neutral hydrophobic organic chemicals in a marine benthic fish, Pseudopleuronectes yokohamae

We investigated the respiratory uptake kinetics of polychlorinated biphenyls (PCBs), organohalogen pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and 2,2′,4,4′-tetrabrominated diphenyl ether (BDE #47) in a marine benthic fish, Pseudopleuronectes yokohamae. The respiratory uptake efficiencies (E_W) of the chemicals, of which there have been no reports for the majority of persistent organic pollutants (POPs), were obtained by measuring the respiratory uptake rate constants (k₁) and the oxygen consumption rates of fish. Fish were exposed to water in which these chemicals were dissolved at environmentally relevant concentrations for 28 d, followed by 168 d of depuration in clean seawater. The k₁ and E_W values for 99 compounds were obtained, and they ranged from 2000 to 42 000 L kg-lipid⁻¹ d⁻¹ and from 0.060 to 1.3, respectively. The E_W values of the chemicals, except for PAHs, tended to increase with increasing values of the log octanol–water partition coefficients (K_OW) of the chemicals up to a log K_OW of 5. For log K_OW in the range 3–5, the E_W values in this study were much lower than those in a published study (about one-third). As a result of analysis by a two-phase resistance model, the resistance of transport rates to the lipid phase in this study was lower than was the case in the published study. These findings indicate that the E_W predicted by the published study for log K_OW in the range 3–5 may differ among fish species and water temperature, and further study is needed.     

Occurrence of selected pharmaceuticals in river water in Japan and assessment of their environmental risk

The existence of pharmaceuticals in the water environment is thought to be a potential problem for aquatic organisms. In this study, we conducted a nationwide survey to clarify the occurrence of 24 selected pharmaceuticals in major Japanese rivers and evaluated their environmental risk to aquatic organisms. We found a total of 22 substances in river waters at concentrations from several nanograms per liter to several micrograms per liter. We found the highest, which was 2.4 μg/L of caffeine, followed by 1.5 μg/L of crotamiton and 1.4 μg/L of sulpiride. We conducted an environmental risk assessment of the 22 pharmaceuticals detected in river water, for which predicted no-effect concentration (PNEC) values for crustacea and algae had been obtained. The measured environmental concentration/PNEC values of four substances, caffeine, carbamazepine, clarithromycin, and ketoprofen, exceeded 0.1 with the maximum value of 9.0 for clarithromycin. As clarithromycin exhibits a high environmental risk to aquatic organisms, particular attention is required.     

Anaerobic biodegradation of biphenyl in various paddy soils and river sediment

The anaerobic degradation of biphenyl was investigated in four uncontaminated Japanese paddy soils and one river sediment sample contaminated with benzene and chlorinated aliphatics. Two of the paddy soils and the sediment were capable of degrading biphenyl anaerobically without any additional medium or electron acceptors. The half-lives of biphenyl biodegradation in the three samples were 212 d in the Kuridashi soil, 327 d in the Kamajima soil, and 429 d in the river sediment. The Kuridashi soil metabolized 1+/-0.3% of [U-14C]-biphenyl into CO2 and 5+/-2% into water-soluble metabolites after 45 d of incubation. Submerged conditions, which result in lower nitrate and iron oxide contents, and neutral pH, appeared to be the common properties among the samples that influenced their degradation capacities. The addition of 10mM sulfate and 20mM Fe(III) as electron acceptors did not enhance the biphenyl degradation rate, whereas 10mM nitrate completely inhibited biphenyl degradation. The addition of different electron donors (lactate, acetate, or pyruvate) slightly slowed the degradation. Molybdate (an inhibitor of sulfate-reducing bacteria) had an inhibitory effect on biphenyl biodegradation, but bromoethanesulfonic acid (an inhibitor of methanogens) did not. Most biphenyl degradation was observed when only water was added, with no other electron acceptors or donors. These results suggest that sulfate-reducing bacteria and fermentative microbial populations play important roles in anaerobic biphenyl biodegradation in paddy soil.