Application of Klebsiella oxytoca immobilized cells on the treatment of cyanide wastewater

Klebsiella oxytoca, isolated from cyanide-containing industrial wastewater, has been shown to be able to biodegrade cyanide to non-toxic end products. The technology of immobilized cells can be applied in biological treatment to enhance the efficiency and effectiveness of biodegradation. In this study, potassium cyanide was used as the target compound and both alginate and cellulose triacetate techniques were applied for the preparation of immobilized cells. Results from this study show that KCN can be utilized as the sole nitrogen source by K. oxytoca. The free suspension systems reveal that the cell viability was highly affected by initial KCN concentration and pH. Results show that immobilized cell systems could tolerate a higher level of KCN concentration and wider ranges of pH. In the batch experiments, the maximum KCN removal efficiencies using alginate and cellulose triacetate immobilized beads were 0.108 and 0.101mM h(-1) at pH 7, respectively. Results also indicate that immobilized system can support a higher biomass concentration. Complete KCN degradation was observed after the operation of four consecutive degradation experiments with the same batch of immobilized cells. This suggests that the activity of immobilized cells can be maintained and KCN can be used as the nitrogen source throughout KCN degradation experiments. The maximum KCN removal rates using alginate and cellulose triacetate immobilized beads in continuous-column system were 0.224 and 0.192mMh(-1) with initial KCN concentration of 3mM, respectively. Results indicate that the immobilized cells of K. oxytoca would be applicable to the treatment of cyanide-containing wastewaters.     

Subregion districting analysis for municipal solid waste collection privatization

Privatization of municipal solid waste (MSW) collection can improve service quality and reduce cost. To reduce the risk of an incapable company serving an entire collection area and to establish a competitive market, a large collection area should be divided into two or more subregions, with each subregion served by a different company. The MSW subregion districting is generally done manually, based on the planner's intuition. Major drawbacks of a manual approach include the creation of a districting plan with poor road network integrity for which it is difficult to design an efficient collection route. The other drawbacks are difficulty in finding the optimal districting plan and the lack of a way to consistently measure the differences among subregions to avoid unfair competition. To determine an MSW collection subregion districting plan, this study presents a mixed-integer optimization model that incorporates factors such as compactness, road network integrity, collection cost, and regional proximity. Two cases are presented to demonstrate the applicability of the proposed model. In both cases, districting plans with good road network integrity and regional proximity have been generated successfully.     

A Risk-Based Approach to Evaluating Wildlife Demographics for Management in a Changing Climate: A Case Study of the Lewis’s Woodpecker

Given the projected threat that climate change poses to biodiversity, the need for proactive response efforts is clear. However, integrating uncertain climate change information into conservation planning is challenging, and more explicit guidance is needed. To this end, this article provides a specific example of how a risk-based approach can be used to incorporate a species’ response to climate into conservation decisions. This is shown by taking advantage of species’ response (i.e., impact) models that have been developed for a well-studied bird species of conservation concern. Specifically, we examine the current and potential impact of climate on nest survival of the Lewis’s Woodpecker (Melanerpes lewis) in two different habitats. To address climate uncertainty, climate scenarios are developed by manipulating historical weather observations to create ensembles (i.e., multiple sequences of daily weather) that reflect historical variability and potential climate change. These ensembles allow for a probabilistic evaluation of the risk posed to Lewis’s Woodpecker nest survival and are used in two demographic analyses. First, the relative value of each habitat is compared in terms of nest survival, and second, the likelihood of exceeding a critical population threshold is examined. By embedding the analyses in a risk framework, we show how management choices can be made to be commensurate with a defined level of acceptable risk. The results can be used to inform habitat prioritization and are discussed in the context of an economic framework for evaluating trade-offs between management alternatives.     

探究性教学在大学语文课程中的运用——以讲授苏轼《水调歌头》一课为例

《大学语文》作为高职高专的一门公共基础课,因其丰富的人文内蕴、情感价值和审美趣味而承担了进一步提高大学生人文素质、增进文化修养的功能,从而培养大学生具有深厚人文精神的理想人格。在《大学语文》教学活动中开展探究性教学,既是教育改革全面实施素质教育的客观要求,也是大学生自我提升的内在需要。以讲授苏轼的《水调歌头·明月几时有》一课为例,阐述如何在高职高专《大学语文》课程的教学活动中引导和组织学生开展探究性教学。     

The Characterization of Ozone and Sulfur Dioxide Air Quality Data for Assessing Possible Vegetation Effects

Since the 1960s, much effort has been devoted to collecting and formatting air quality data. This paper discusses 1) the availability of air quality data for assessing potential biological impacts associated with ozone and sulfur dioxide ambient exposures, 2) examples of how air quality data can be characterized for assessing vegetation effects, and 3) the limitations associated with some exposure parameters used for developing relevant vegetation doseresponse yield reduction models. Data are presented showing that some ozone monitoring sites not continuously affected by local urban sources experience consecutive hourly ozone exposures ≥0.10 ppm in the late evening and early morning hours. These sites experience their maximum ozone concentrations either in the spring or summer months. Sites influenced by local rural sources experience their maximum ozone concentrations during the summer months. It is suggested that further research be performed to identify whether the sensitivity of a target organism at the time of exposure, as well as the pollutant concentration and chemical form that enters into the target organism, is as important in defining effects as air pollutant exposure alone.     

Lead contamination of the Seine River, France: geochemical implications of a historical perspective

Four sediment cores collected in the Seine River basin and dated between 1916 and 2003 were analyzed for lead concentrations and isotopic composition. In all four cores, the measured Pb concentration (up to 460 mg kg⁻¹) lies significantly above the natural background (27-40 mg kg⁻¹), although a significant decrease (down to 75 mg kg⁻¹) was observed during the second half of the 20th century which can be explained by the reduction of lead emissions. The ²⁰⁶Pb/²⁰⁷Pb ratio measured in these samples indicates that the main source of Pb used in the Paris conurbation is characterized by a “Rio Tinto” signature (defined as ²⁰⁶Pb/²⁰⁷Pb = 1.1634 ± 0.0001). A high contribution, up to 25%, from the leaded gasoline (characterized by ²⁰⁶Pb/²⁰⁷Pb = 1.08 ± 0.02) is revealed in the Seine River downstream Paris, indicating that lead from the leaded gasoline is preferentially released to the river.The dominating Pb signature in the Paris conurbation that is currently sampled through incinerators fumes (²⁰⁶Pb/²⁰⁷Pb = 1.1550 ± 0.0005) and waste water treatment plant (²⁰⁶Pb/²⁰⁷Pb = 1.154 ± 0.002), represents a mixture of highly recycled lead from the Rio Tinto mine and lead from leaded gasoline (imprinted by the low ²⁰⁶Pb/²⁰⁷Pb of the Broken Hill mine). This signature is called “urban” rather than “industrial”, because it is clearly distinct from the Pb that is found in areas contaminated by heavy industry, i.e. the heavy industries located on the Oise River which used lead from European ores characterized by high ²⁰⁶Pb/²⁰⁷Pb ratios (∼1.18-1.19) and possibly a minor amount of North American lead (²⁰⁶Pb/²⁰⁷Pb ratios > 1.20). The “urban” signature is also found in a rural area upstream of Paris in the 1970’s. At the Seine River mouth in 2003, Pb with an urban signature represents 70% of the total Pb sediment content, with the 30% remaining corresponding to natural Pb.     

Application of in situ biosparging to remediate a petroleum-hydrocarbon spill site: field and microbial evaluation

In this study, a full-scale biosparging investigation was conducted at a petroleum-hydrocarbon spill site. Field results reveal that natural attenuation was the main cause of the decrease in major contaminants [benzene, toluene, ethylbenzene, and xylenes (BTEX)] concentrations in groundwater before the operation of biosparging system. Evidence of the occurrence of natural attenuation within the BTEX plume includes: (1) decrease of DO, nitrate, sulfate, and redox potential, (2) production of dissolved ferrous iron, sulfide, methane, and CO(2), (3) decreased BTEX concentrations along the transport path, (4) increased microbial populations, and (5) limited spreading of the BTEX plume. Field results also reveal that the operation of biosparging caused the shifting of anaerobic conditions inside the plume to aerobic conditions. This variation can be confirmed by the following field observations inside the plume due to the biosparging process: (1) increase in DO, redox potential, nitrate, and sulfate, (2) decrease dissolved ferrous iron, sulfide, and methane, (3) increased total cultivable heterotrophs, and (4) decreased total cultivable anaerobes as well as methanogens. Results of polymerase chain reaction, denaturing gradient gel electrophoresis, and nucleotide sequence analysis reveal that three BTEX biodegraders (Candidauts magnetobacterium, Flavobacteriales bacterium, and Bacteroidetes bacterium) might exist at this site. Results show that more than 70% of BTEX has been removed through the biosparging system within a 10-month remedial period at an averaged groundwater temperature of 18 degrees C. This indicates that biosparging is a promising technology to remediate BTEX contaminated groundwater.