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11.
12.
  总被引:6,自引:0,他引:6  
Two dry anaerobic digestions of organic solid wastes were conducted for 6 weeks in a lab-scale batch experiment for investigating the start-up performances under mesophilic and thermophilic conditions. The enzymatic activities, i.e., β-glucosidase, N-α-benzoyl-Largininamide (BAA)-hydrolysing protease, urease and phosphatase activities were analysed. The BAA-hydrolysing protease activity during the first 2-3 weeks was low with low pH, but was enhanced later with the pH increase. β-Glucosidase activity showed the lowest values in weeks 1-2, and recovered with the increase of BAA-hydrolysing protease activity. Acetic acid dominated most of the total VFAs in thermophilic digestion, while propionate and butyrate dominated in mesophilic digestion. Thermophilic digestion was confirmed more feasible for achieving better performance against misbalance, especially during the start-up period in a dry anaerobic digestion process.  相似文献   
13.
Antarctic krill, Euphausia superba, hatched from eggs and maintained for four years, were sampled periodically for age-pigment analysis. Extractable pigments from the eye and eyestalk ganglia were quantified using fluorescence intensity and standardised against protein. Three peak fluorescence intensities were detected at wavelengths of excitation 280 nm, emission 625 nm (pigment 1); excitation 355 nm, emission 510 nm (pigment 2); and excitation 463 nm, emission 620 nm (pigment 3). There was a positive correlation between the quantity of pigments 1 and 3 and the age of Antarctic krill. A model was developed to predict age from pigment 3 and to compare it with other age proxies (carapace length and eyeball diameter). The quantity of pigment 3 was the best predictor of age. The pigment method can discriminate between similar sized krill aged 12 and 36 months. Age pigments provide an improved tool for age estimation in Antarctic krill, particularly if used in conjunction with other demographic information.  相似文献   
14.
The natural grassland ecosystem of the Xilingol steppe has traditionally been the source of the most productive and highest quality agriculture in northern China. Unfortunately, the area is now experiencing degradation due to resource overuse. In an attempt to forecast grassland production and to sustain the ecosystem, we built a time-dependent simulation model of the ecosystem based on long-range weather forecasts (several weeks to several months). The model incorporated five state variables including above- and belowground biomass, the amount of standing dead plant material, livestock (sheep) weight, and the amount of excrement per unit ground area. Within the model, solar light energy is fixed by grassland vegetation and flows through the other variables via a variety of organism-environment interactions. The model was written using a set of simultaneous differential equations and was numerically analyzed. The values of the time-dependent parameters controlling energy flow were determined based on data accumulated in experiments and field surveys executed at a grassland experimental station located in Xilingol, as well as by reference to related literature. We used daily meteorological data including air temperature and rainfall recorded at the Xilinhot Meteorological Observatory. Simulated results for several stocking densities coincided well with the data of aboveground plant biomass observed at the experimental station in 1990, 1993, and 1997. We obtained reasonable simulation results for five stocking densities, three air temperature patterns, and five rainfall patterns. When a month-long drought, which sometimes occurs in this area, was forecast by a local weather station, a decrease in grassland production was forecast by the model. Such forecasts will assist in the management of livestock, forage preservation, and grassland conservation.  相似文献   
15.
Industrial symbiosis is the sharing of services, utility, and by-product resources among industries. This is usually made in order to add value, reduce costs, and improve the environment, and therefore has been taken as an effective approach for developing an eco-industrial park, improving resource efficiency, and reducing pollutant emission. Most conventional evaluation approaches ignored the contribution of natural ecosystem to the development of industrial symbiosis and cannot reveal the interrelations between economic development and environmental protection, leading to a need of an innovative evaluation method. Under such a circumstance, we present an emergy analysis-based evaluation method by employing a case study at Shenyang Economic and Technological Development Zone (SETDZ). Specific emergy indicators on industrial symbiosis, including emergy savings and emdollar value of total emergy savings, were developed so that the holistic picture of industrial symbiosis can be presented. Research results show that nonrenewable inputs, imported resource inputs, and associated services could be saved by 89.3, 32.51, and 15.7 %, and the ratio of emergy savings to emergy of the total energy used would be about 25.58 %, and the ratio of the emdollar value of total emergy savings to the total gross regional product (GRP) of SETDZ would be 34.38 % through the implementation of industrial symbiosis. In general, research results indicate that industrial symbiosis could effectively reduce material and energy consumption and improve the overall eco-efficiency. Such a method can provide policy insights to industrial park managers so that they can raise appropriate strategies on developing eco-industrial parks. Useful strategies include identifying more potential industrial symbiosis opportunities, optimizing energy structure, increasing industrial efficiency, recovering local ecosystems, and improving public and industrial awareness of eco-industrial park policies.  相似文献   
16.
    
This paper evaluates the mitigation effect of Tokai earthquake measures on housing damage using a counterfactual approach. It focuses on those measures that stimulate ex‐ante investment in disaster prevention in the supposedly affected area, including earthquake‐proof retrofitting and improved housing construction; the effect of the measures on housing losses is estimated monetarily. The study compares factual disaster damage computed using a real distribution of houses with counterfactual damage to a hypothetical housing distribution that would occur if the measures were not implemented. The key findings are: (i) the disaster mitigation effects of Tokai earthquake measures on housing amount to approximately JPY 18 billion (USD 0.18 billion) for Yamanashi Prefecture and JPY 0.26 trillion (USD 2.6 billion) for Shizuoka Prefecture, which would be at the centre of the event; (ii) a before–after comparison biases estimates of the mitigation effect; and (iii) statistically, the measures do not mitigate the housing damage predicted for an earthquake in Tokai.  相似文献   
17.
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.  相似文献   
18.
Zhou W  Imai T  Ukita M  Li F  Yuasa A 《Chemosphere》2007,66(5):924-929
Serious inhibition was found in the regular up-flow anaerobic sludge blanket (UASB) reactor in treating the evaporator condensate from a sulfite pulp mill, which contained high strength sulfur compounds. After applying the direct limited aeration in the UASB, the inhibition was alleviated gradually and the activity of the microorganisms was recovered. The COD removal rate increased from 40% to 80% at the organic loading rate of 8kgCODm(-3)d(-1) and a hydraulic retention time of 12h. Limited aeration caused no oxygen inhibition to the anaerobic microorganisms but instigated sulfide oxidization and H(2)S removal, which was beneficial to the methanogens. The experiment confirmed the feasibility of applying limited aeration in the anaerobic reactor to alleviate the sulfide inhibition. It also proved that the anaerobic system was actually aerotolerant. SEM observation showed that the predominant microorganisms partly changed from rod-shaped methanogens to cocci after the UASB reactor was aerated.  相似文献   
19.
Homogeneous oxidation reactions of gaseous elemental mercury were experimentally tested to study the behavior of mercury compounds that contribute to toxic emissions in combustion flue gas. Chemical equilibrium calculations and reaction kinetics analysis were also carried out to help explain the experimental results. In particular, the chemical forms of oxidized mercury and their reaction paths were verified in detail. Among the experimental results, molecular chlorine was confirmed to have a higher oxidizing ability toward elemental mercury than hydrogen chloride does. From the chemical equilibrium calculation, the final product of mercury compounds oxidized by chlorine was confirmed to be mercury chloride (HgCl2). Numerical analyses of reaction kinetics were mostly consistent with the experimental results and the chemical equilibrium calculations. The ratio of mercury oxidization by chlorine increases with temperature from 473 K to 873 K, although it decreases at temperatures higher than 1000 K. Sensitivity analysis revealed the dominant reaction path of the mercury oxidation by chlorine. First, elemental mercury reacts with Cl radicals to form HgCl. Then, the HgCl reacts with Cl2 to produce HgCl2.  相似文献   
20.
Medical waste management is of great importance due to its potential environmental and public health risks, especially in developing countries where both financial and technological resources on medical waste management are still lacking. Although many studies have focused on country-scaled medical waste management, few have paid close attention to regional (city-scale) management, particularly in China. This paper fills such a gap by employing a case study approach. Due to its representative nature, Shenyang was selected as the case study. After a review of China’s medical waste management, an empirical study in Shenyang was conducted in order to analyze the current state as well as identify key challenges on regional medical waste management. Based upon the local realities and aiming to better manage medical wastes, an integrated medical waste management framework is developed. Such a platform encourages the establishment of a specific medical waste management authority, a city scaled capacity building program on improving the general public’s awareness, an information platform, application of state-of-the-art technologies, as well as creation of an effective financial system. The combination of such initiatives can significantly improve the overall eco-efficiency of medical waste management at the regional level and should be promoted to other developing cities.  相似文献   
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