The introduction of Littorina littorea to British Columbia, Canada: potential impacts and the importance of biotic resistance by native predators

Although the establishment and spread of non-indigenous species depends upon survival in the face of novel environmental conditions and novel biological interactions, relatively little attention has been focused on the specific role of native predators in limiting invasion success. The European common periwinkle, Littorina littorea, was recently introduced to the Pacific coast of Canada and provides a case study of an introduction into an area with an important predator guild (sea stars) that is functionally minor in the invader’s native habitat. Here, we assess the likelihood of establishment, spread, and negative ecological impact of this introduced gastropod, with an emphasis on the role of native sea stars as agents of biotic resistance. Size frequency distributions and local market availability suggest that L. littorea was most likely introduced via the live seafood trade. Non-native hitchhikers (e.g., the trematode Cryptocotyle lingua) were found on/in both market and field specimens. Laboratory studies and field observations confirmed that L. littorea can survive seasonal low salinity in Vancouver, British Columbia. Periwinkles also readily consumed native Ulva, suggesting that periwinkles could impact native communities via herbivory or resource competition. Unlike native gastropods, however, L. littorea lacked behavioural avoidance responses to Northeast Pacific predatory sea stars (Pisaster ochraceus and Pycnopodia helianthoides), and sea star predation rates on L. littorea were much higher than predation rates on native turban snails (Chlorostoma funebralis) in common garden experiments. We therefore expect periwinkle establishment in British Columbia to be limited to areas with low predator density, as is seen in its field distribution to date. We caution that this conclusion may understate the importance of the L. littorea introduction if it also serves as a vector for additional non-indigenous species such as C. lingua.     

Control of hydrogen sulphide in digestor gas using iron salts

Different dosages of ferrous chloride and ferric chloride were added to digestors separately, and the volumes of methane and hydrogen sulphide contained in the digestor gas (biogas) were monitored. It was noted that the effects of adding of 16, 18 and 32 kg ferrous chloride/ tonne volatile solids, and 16 and 18 kg ferric chloride/tonne volatile solids were similarly effective in controlling the hydrogen sulphide levels.

According to an average amount of undigested sludge (primary sludge mixed with surplus activated sludge) of 41 tonne volatile solids produced each day during the sewage treatment process in Shatin sewage treatment works, and the required dosage of 16 kg ferric chloride/ tonne volatile solids, the amount of iron salts required should be 656 kg/day or 3.3 mg/L for the actual application, based on an average sewage flow of 200,000 m³/day.     

Effect of C/N on composting of pig manure with sawdust

The aim of this composting trial was to evaluate the effect of C/N on the composting process of pig manure with the purpose of reducing the amount of sawdust normally used as co-composting materials. Two aerobic static piles were prepared consisting of pig manure mixed with sawdust at an initial C/N of 30 (pile A) and 15 (pile B), respectively. Pile B containing larger amount of pig manure showed a slower rise in temperature, lower maximum temperature, and shorter thermophilic phase than pile A. It also resulted in higher pH and electrical conductivity (EC) values, and even higher contents of soluble NH4-N and volatile solids throughout the composting period. Chemical and biological parameters including dissolved organic carbon (DOC) (4932 mg kg(-1)), soluble NH4-N (371 mg kg(-1)), C/Nsolid (18.3), C/Naquoeus (5.8) and seed germination index (GI) (66.5%) indicated that pile A achieved maturity after 49 days of composting. After 63 days of composting, pile B contained 5352 and 912 mg kg(-1) of DOC and soluble NH4-N content, respectively, which was much higher than the criterion of 5% and 400 mg kg(-1), indicating its immature nature. Pile B showed a relatively low GI value of 46%, which may be due to its high indigenous EC value as a result of larger amount of pig manure. Therefore, co-composting of pig manure with sawdust at a low initial C/N would require a composting longer than 63 days, and, the high salinity due to the large amount of pig manure would pose a potential inhibition on plant growth.     

Residential proximity to industrial sources of air pollution: interrelationships among race, poverty, and age

This study builds on earlier work investigating statistical relationships between sociodemographic characteristics of populations and their residential proximity to industrial sources of air pollution. The analysis uses demographic data from the 1990 U.S. Census and industrial site data from the U.S. Environmental Protection Agency (EPA)'s 1990 Toxics Release Inventory (TRI). The focus is on examining interactions among race (African Americans and Whites), poverty (above and below household poverty threshold), and age (children from birth to 5 years of age and elderly people 65 years old or older). Results from three different study areas (Kanawha Valley in West Virginia, the Baton Rouge-New Orleans Corridor in Louisiana, and the greater Baltimore metropolitan area in Maryland) suggest there are important interactions among race, poverty, and age that are likely to have consequential ramifications for efforts aimed at investigating issues related to environmental justice. Our results indicate that a substantial proportion of all demographic groups studied live within a mile of the nearest facility, with values ranging from 22% of Whites above poverty in the Baton Rouge-New Orleans Corridor to 60% of African Americans below poverty in Baltimore. Likewise, a substantial proportion of all demographic groups also live within 2 miles of four or more industrial facilities, with values ranging from 16% for Whites above poverty in the Corridor to 70% for African Americans below poverty in Baltimore. In all three study areas, African Americans were more likely than Whites to (1) live in households with incomes below the household poverty line, (2) have children 5 years of age or younger, (3) live closer to the nearest industrial emissions source, and (4) live within 2 miles of multiple industrial emission sources. Findings indicate that, compared with White children, a substantially higher proportion of African-American children 5 years of age or younger lived in poor households that were located in relatively close proximity to one or more industrial sources of air pollution.     

Predictive model for motorcycle accidents at three-legged priority junctions

In conjunction with a nationwide motorcycle safety program, the provision of exclusive motorcycle lanes has been implemented to overcome link-motorcycle accidents along trunk roads in Malaysia. However, not much work has been done to address accidents at junctions involving motorcycles. This article presents the development of predictive model for motorcycle accidents at three-legged major-minor priority junctions of urban roads in Malaysia. The generalized linear modeling technique was used to develop the model. The final model reveals that motorcycle accidents are proportional to the power of traffic flow. An increase in nonmotorcycle and motorcycle flows entering the junctions is associated with an increase in motorcycle accidents. Nonmotorcycle flow on major roads had the highest effect on the probability of motorcycle accidents. Approach speed, lane width, number of lanes, shoulder width, and land use were found to be significant in explaining motorcycle accidents at the three-legged major-minor priority junctions. These findings should enable traffic engineers to specifically design appropriate junction treatment criteria for nonexclusive motorcycle lane facilities.     

Microbial enhancement of Cu2+ removal capacity of Eichhornia crassipes (Mart.)

Bacteria resistant to Cu2+, Ni2+ or Zn2+ were isolated from the rhizosphere of water hyacinth (Eichhornia crassipes (Mart.)) and their metal ion removal capacities (RCs) were determined. The Ni2+ and Zn2+ RCs of the respective metal ion-resistant bacteria were less than 4.1 mg g(-1), while one of the Cu2+-resistant bacteria (Strain CU-1) showed a significant high Cu2+ RC of 10.6 mg g(-1). The effect of inoculating water hyacinth with Strain CU-1 on its Cu2+ RC was further studied. Water hyacinths were treated with an antibiotic, oxytetracycline (OTC), to remove most rhizospheric bacteria of plant roots. Inoculation of Strain CU-1 increased the Cu2+ RC of the plant root by 1.91 (OTC-treated) and 1.56 (OTC-untreated) folds respectively when compared with the control. Results also showed that Strain CU-1 colonized onto the plant root and led to the increase of Cu2+ RC of the roots of water hyacinth.     

Sewage sludge as organic ameliorant for revegetation of fine bauxite refining residue

The rise in aluminium demand in the world has significantly increased the generation of bauxite residue which occupies huge areas of land worldwide. Direct revegetation of residue storage areas has been unsuccessful because of the high alkalinity and salinity, and poor nutrient contents of the fine residue (red mud). This paper describes glasshouse and field experiments evaluating the potential use of sewage sludge as an organic ameliorant for gypsum amended red mud. The growth of Agropyron elongatum in red mud receiving gypsum (0 and 38.5 t ha⁻¹) and sewage sludge (0, 38.5 and 77 t ha⁻¹) amendment was assessed in a glasshouse study. Leachate and soil analyses revealed that gypsum was effective in reducing the pH, EC and ESP of red mud, while sewage sludge gave additional reductions in EC, Na and ESP. No evidence of any significant increases in heavy metal contents were observed in the leachates following sewage sludge amendment. However, soil Al contents were more available in red mud receiving only sewage sludge treatment. Sewage sludge amendment significantly increased dry weight yield and provided sufficient nutrients for plant growth except K which was marginal. No heavy metal accumulation was observed in Agropyron. Following that, a field experiment was performed having red mud amended with sewage sludge (38.5, 77 and 154 t ha⁻¹) and gypsum (38.5 and 77 t ha⁻¹) to evaluate their effects on soil physical properties of red mud. Sewage sludge significantly reduced soil bulk density (25%) and particle density (9%) and increased the total porosity of red mud (8%). Hydraulic conductivity also increased from 1.5 to 23 × 10⁻⁵ m s⁻¹. Plant cover percentage and dry weight yield of Agropyron increased with an increase in gypsum and sewage sludge amendment. The results confirm that sewage sludge is effective in improving both soil structure and nutrient status of gypsum amended red mud. The use of sewage sludge for red mud revegetation provides not just an option for sludge disposal, but also a cost effective revegetation strategy for bauxite refining industry.     

Social face for innovation in strategic alliances in China: the mediating roles of resource exchange and reflexivity

This study proposes that partners who communicate mutual respect to each other develop integrative interaction that is a foundation for innovation. Structural equation analysis suggests that reflecting upon and improving interaction between supplier and customer organizations can contribute to resource exchange between partners that results in innovation in supply chain partnerships. Results also indicate that the confirmation of social face is an important antecedent to these useful integrative interaction patterns. These findings were interpreted as reaffirming the value of relationships for making partnerships effective and that the constructive application of the value of social face can promote open discussion and innovation in China. Copyright © 2007 John Wiley & Sons, Ltd.     

Evaluation of the effectiveness of low frequency workpiece vibration in deep-hole micro-EDM drilling of tungsten carbide

The application of micro-electrical discharge machining (micro-EDM) in deep-hole drilling is still limited due to the difficulty in flushing of debris and unstable machining. Present study introduces a simplistic analytical model to evaluate the effectiveness of low frequency workpiece vibration during the micro-EDM drilling of deep micro-holes. In addition, experimental investigation has been conducted to validate the model by studying the effects of workpiece vibration on machining performance, surface quality and dimensional accuracy of the micro-holes. The effect of vibration frequency and amplitude for three different settings of aspect ratios has been studied experimentally. Moreover, the vibration experiments have been conducted at different levels of gap voltages and capacitances in order to understand the effect of electrical parameters and effectiveness of low-frequency workpiece-vibration at different levels of discharge energies. It has been shown analytically that the effectiveness of low frequency workpiece vibration during micro-EDM drilling can be evaluated by a parameter ‘K_v’ (ratio of maximum acceleration of the vibrating plate in gravitational direction to gravitational acceleration ‘g’), which can be determined from the vibration frequency, amplitude and phase angle of the vibrating workpiece. The theoretical model reveals that for K_v > 1, the position of debris particles will be above the workpiece; thus can be flushed away from machined zone effectively. The experimental reasons for improved micro-EDM drilling performance at the setting of K_v > 1 are found to be the increased effective discharge ratio, reduced short-circuits and improved dielectric flushing. The experimental results also reveal that the low frequency vibration is more effective at the low discharge energy level, thus making it more suitable for micro-EDM. Considering the effect on both the machining characteristics and micro-hole accuracy parameters, vibration frequency of 750 Hz and amplitude of 1.5 μm was found to provide improved performance for the developed vibration device.