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Weather generators (WGs) are tools that create synthetic weather data, which are statistically similar to the observed data. Considering the limitations of most rainfall generators to preserve satisfactorily the fundamental statistical properties (e.g., spatial and temporal coherence) simultaneously, we propose a new framework for multisite rainfall generation. The framework consists of three main components: (1) a spatiotemporal rainfall field, described as spatial modes and their corresponding temporal evolution based on empirical orthogonal function analysis (EOFA). (2) The time series of these spatial modes, decomposed into intrinsic mode functions (IMFs) with characteristic frequencies (periods) using Hilbert-Huang transform (HHT). (3) Stochastic simulation (SS), achieved by assigning random phases for the specific IMFs. The current model, EHS ( E OFA + H HT + S S), is compared with two other typical multi-site rainfall generators, MulGETS (parametric model) and KNN (non-parametric model) for a network of 12 stations in Xiang River basin, China. These three models are assessed based on their ability to simulate sequences with statistical attributes that are similar to those observed. We compare the basic statistics (mean, standard deviation, skewness), extreme value characteristics (95th percentile and maximum), spatial dependence (spatial correlation and spatial continuity ratio), and temporal dependence statistic (autocorrelation, wet/dry spells, and low-frequency variability). The results show that EHS rainfall generator has a similar capacity as KNN model in reproducing the spatial structure of the original rainfall field, and has a greater ability than MulGETS and KNN model to preserve the historical temporal statistics, especially the autocorrelation at various time scales and low-frequency variability. Overall, EHS is a useful model for generating realistic multi-site rainfall field and can be expected to generate plausible scenarios for impact studies.

Polybrominated diphenyl ethers (PBDEs) contained in electronic waste (e-waste) can be released to indoor environments and cause occupational health hazards during the recycling process. TVs, washing machines, refrigerators and printed wiring boar (PWB) represent the main domestic e-wastes. In this study, concentrations of Σ7PBDEs in air and dust samples from recycling workshops handling these four major types of e-wastes were measured, and the occupational exposure risk for workers at the corresponding workshops was evaluated. Concentrations of Σ7PBDEs in air and dust were within the ranges of 55.28–369.66 ng/m3 and 158.07–669.81 μg/g, respectively. The highest concentration of Σ7PBDEs in air was detected in the TV recycling workshop, while the refrigerator recycling workshop had the highest level of Σ7PBDEs in dust. The workers at these two e-waste recycling workshops were the most substantially exposed to BDE-209, which accounted for more than 85% of Σ7PBDEs in both air and dust. Compared to other e-waste recycling workshops, the workers at the PWB recycling workshop were also more exposed to BDE-47 and BDE-99. Occupational exposure levels for inhalation and dust ingestion were within the ranges of 3939 pg/kg/d to 26,271 pg/kg/d and 104,945 pg/kg/d to 444,694 pg/kg/d, respectively. The hazard quotient (HQ) values were calculated based on the RfDs provided by the EPA. Total HQ levels of inhalation exposure and dust ingestion were less than 0.222. The results of the HQ indicated that no adverse health effects were expected for workers in these workshops; however, the exposure risk of workers in the PWB recycling workshop (HQ=0.222) was higher than that in other e-waste recycling workshops (HQ=0.022–0.072). At the PWB recycling workshop, BDE-47 and BDE-99 caused the main occupational exposure risk to the workers, while s in the recycling plants handling other types of domestic e-waste BDE-209 was the major contributor to the risk faced by the workers.

A quality-assured ecological risk assessment (ERA) requires enormous resources (time and labor) in collection/assessment of hazard data, as well as considerable expertise to interpret the risk. The ERA of chemicals is thereby considered difficult or impossible for those with little assessment experience and cumbersome or complicated for practitioners. To meet the concerns regarding ERA and accelerate the risk assessment and management of chemicals, we developed an all-in-one free tool for multi-purpose ecological risk assessment management (MeRAM) of chemical substances in aquatic environment called the AIST-MeRAM Ver. 2.0.0 (Copyright No: H28PRO-2007). It allows users from beginners to experts to conduct ERA without any preparation because all the necessary ecotoxicity test data and methodologies are available in the system. Approximately 270,000 ecotoxicity test data points for 3900 chemical substances together with the scientific methodologies from traditional simple hazard quotient (HQ) to more ecologically relevant complicated assessments such as species sensitivity distribution (SSD) and population-level assessment are embedded in the AIST-MeRAM. In addition, users can easily understand the Japanese regulatory RA and management of chemical substances due to a special function based on the Japanese Chemical Substance Control Law (CSCL). Here, we demonstrate a tiered ERA using the embedded sample data to evaluate and ensure the functions of AIST-MERAM. We show that the AIST-MeRAM can provide a comprehensive and accurate ERA, suggesting that it is a powerful IT solution for cumbersome ERA.

Growing concerns about the hydrological impacts of climate variability and climate change suggest an imperativeness to generate plausible climate scenarios suitable for the vulnerability assessment studies. A frequency-domain nonstationary framework for multi-site rainfall generation is proposed for decision-centric hydrological impact assessments. The framework has three main components: (1) a spatiotemporal rainfall field, described as spatial modes and their corresponding temporal evolution, based on empirical orthogonal function analysis (EOFA); (2) the time series of these spatial modes, decomposed into intrinsic mode functions (IMFs) with characteristic frequencies (periods) using the Hilbert-Huang transform (HHT); and (3) Stochastic simulation (SS), achieved by assigning random phases to the noise IMFs in combination with adjustments both to the residual series and to the signal IMFs. A synthetic test function is first used to illustrate the power of the EHS (EOFA + HHT + SS) rainfall generator to detect and extract signals (e.g., nonstationary oscillation and trend component) from noisy data. A real application of the EHS model is then presented for the Xiang River basin to demonstrate its ability (reproducibility and adaptivity). The results showed that the EHS rainfall generator has sufficient capacity in reproducing the original spatiotemporal structure, such as the spatial correlation and low-frequency variability. Meanwhile, the EHS model exhibits advantages in terms of perturbing the distribution characteristics of rainfall and altering their behavior according to the intrinsic spatial patterns. These features give the EHS model high feasibility to act as a scenario generator for generating a wide range of possible rainfall scenarios reflecting different aspects of climate variability and climate change, and hence bolster the hydrological impact analysis in the climate change context.

Heavy metal (HM) pollution is a serious and urgent issue in integrated watershed management in China and worldwide. Determining effective management strategies for pollution control requires quantification of input and output metal fluxes and the inherent uncertainties. Process-based metal models can simulate the metal movement on a watershed scale providing essential information for metal budget. However, there has been little effort to quantify the uncertainties in metal flux simulations. In this work, we modified the previously developed SWAT-HM (Soil and Water Assessment Tool – Heavy Metal) model by adding two external model inputs (atmospheric deposition and agricultural-source input) and one process-based module (plant uptake). We then linked the modified model with the SWAT Calibration and Uncertainty Programs SWAT-CUP for stochastic calibration and uncertainty analysis. The modified SWAT-HM was used to model the fluxes of primary inputs and outputs of zinc (Zn) in both uplands (soil) and channel (bed sediment) in the upper Liuyang River watershed in south-central China. To calibrate the model with uncertainty analysis, we used six-years of daily streamflow, daily sediment load, and daily Zn load at monthly frequency at the watershed outlet. In the upland phase, we identified Zn input from atmospheric deposition and Zn output through soil erosion as the most significant fluxes. In the channel phase, bed sediment was the critical Zn sink receiving 5,100 to 42,000 kg yr−1 Zn. The method used in SWAT-HM calibration and uncertainty analysis is general with potential application to similar settings in the world.

Widespread chemical plants render human life more vulnerable to major natural disasters such as earthquakes. Recognizing the potential cascading threats initiated by a devastating earthquake, a general methodology for assessing the life loss risks introduced by airborne hazardous chemical dispersion following seismically induced chemical release (SICR) was proposed. With a 600 km × 600 km region in North China as a demonstrative study area, the dispersion of ammonia released from multiple relevant chemical plants that were supposed to be damaged by a devastating earthquake was simulated in a probabilistic manner. Using an ammonia toxicity-fatality relationship and its toxicity concentration threshold, regional life loss and spatial spread were evaluated. The life loss risk was found to be non-prominent but would be very contingent on unfavorable meteorological conditions. Non-parametric correlation analysis revealed that the respective effects of meteorological mixing parameters on the risk exhibit new features in a disaster context, that is, stronger mixing would cause elevation of risk in a region. This preliminary research implied that the risk of chemical-induced life loss after a devastating earthquake deserves attention and a thorough uncertainty evaluation in the future.

A six-day static-renewal toxicity test was performed to determine the influences of cadmium on the development of embryos of soldatov's catfish (Silurus soldatovi). The median lethal concentration (LC50) value and median effective concentration (EC50, i.e., the total adverse effects, including developmental defects and mortality) were calculated to be 2740 and 133 μg/L, respectively, when cadmium was prepared in dilution water. The LC50 decreased to 266 μg/L in a subsequent test one month later, thereby suggesting that the sensitivity of this fish to cadmium in the early life stage(1) was largely influenced by the quality of fertilized eggs, which is known to be dependent on the season. The mortality and total adverse effects showed a concentration-dependent relationship at dosages greater than 1000 or 10 μg/L (p

Membrane separation was employed in a novel photocatalytic oxidation slurry reactor to conserve catalyst. This paper reports some critical operational conditions of this reactor. While fine-bubble aeration served to suspend the catalyst, introducing an intermittent coarse bubbling under the membrane during operation was vital to counteract TiO2 catalyst entrapment on membrane surface. Circulation flow in the reactor was also found to have certain effect on counteracting the dropping out of catalyst. A submerged membrane module with a pore size of 0.1 μm successfully conserved the powdered catalysts within the reactor after 2 days’ preluding filtration. As for pollutant removal, membrane filtration and circulation flow had no effect, whereas increase in gas holdup had. Running the reactor to treat model pollutant dissolved in tap water revealed that calcium carbonate both deactivated the catalyst and contributed to membrane fouling, suggesting that water hardness and alkalinity deserves appropriate treatment to warrant a good performance of such a reactor.

Here we report a structured matrix model for wild Japanese medaka (Oryzias latipes) and the use of the model to predict the population-level effects of 4-nonylphenol (4-NP) using a stochastic simulation approach. In the model, the natural fecundity and mortality rates of wild medaka were considered inhibited by 4-NP, based on Weibull dose–response models estimated from a full life-cycle toxicity test. The matrix model was simulated according to three scenarios: (1) stochastic daily growth under optimal conditions, (2) stochastic annual growth under conditions of seasonal variation and (3) population dynamics over 3 years undergoing density-regulation. Accordingly, a finite population growth rate, λ, was applied as an endpoint in the first and second scenarios and a quasi-extinction risk in the third scenario. The median and 95% confidence interval (CI) of 4-NP concentrations corresponding to λ = 1 (Cλ=1) in the first and second scenarios were 27.5 μg/L (CI: [20.2, 33.0] μg/L) and 17.0 μg/L (CI: [16.0, 17.9] μg/L), respectively. The quasi-extinction risks mounted quickly when the exposure concentration approached Cλ=1. The influence of uncertainties was analyzed, and the Cλ=1 was found to be robust against uncertainties in both the mean and the variation of vital rates, whereas the quasi-extinction risk was moderately sensitive to the mean mortality rate. The ignorance of whether the survival of adult madaka should be considered inhibited by 4-NP or not was found to remarkably affect the population-level effects. This study demonstrates an application of Cλ=1 in a stochastic sense as a population-level ecological risk assessment (PLERA) endpoint in chemical risk management.

A novel configuration of a photocatalytic slurry reactor using low-pressure mercury lamps coupled with membrane filtration was proposed, and treatment of polluted river water with a pilot plant of this system was investigated. Both COD and NH+4-N in the river water were simultaneously removed. Under the conditions of a hydraulic retention time of 3.0 h, influent COD strength of 50–80 mg L−1 and NH+4-N of 2–6 mg L−1, 80% COD and 50% NH+4-N were achieved, respectively. The reactor was found to own a higher UV utilization effectiveness than most reported photocatalytic reactors. Intermittent backwash was effective to retard the membrane fouling and enable stable membrane operation for more than 1 month. An adhered catalyst, algae and fungi in the river water were the main contaminants of the membrane, but the membrane permeability could be almost recovered through sequential rinsing by tap water and a sodium hypochlorite solution. After continuous operation for over 1 month, the photocatalytic activity of catalysts was found elevated, which likely resulted from adsorption of hydroxyl-rich alcohols onto the catalyst surfaces.