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721.
722.
Many publicly owned treatment works in North America are exceeding permitted limits for total cyanide in their wastewater treatment effluents. A recently introduced rapid, segmented, flow-injection analysis procedure using UV digestion and amperometric detection of the membrane-separated cyanide was used to investigate the various scenarios by which elevated cyanide levels might be present in wastewater treatment plant effluent. A number of significant interferences can produce false positive bias during sample analysis with the traditional acid distillation technique, but are minimized or absent with the new analytical method. However, increased levels of cyanide were found in some chlorinated wastewaters compared to the levels before chlorination, suggesting a fast reaction mechanism associated with the disinfectant and some precursor in the wastewater. In particular, the contact of chlorine with nitrite in the presence of a carbon precursor appears to contribute to cyanide formation during wastewater treatment and sample handling. This paper explores the scenarios under which cyanide can form during wastewater treatment as well as those in which a false bias for total cyanide can be obtained during sample processing and provides guidance for appropriate sample handling, screening, and processing to ensure valid analytical results. 相似文献
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724.
Stored extracts of passive samplers exposed in 757 randomly selected Canadian residences provided a unique opportunity for retrospective determination of the occurrence of airborne volatile organic compounds (VOCs). Aliquots of the individual extracts were pooled to form a composite exposure sample and a corresponding blank sample. To identify and quantitate potentially hazardous organics in the samples, GC-MS analyses were conducted by several approaches. The amounts of 52 target compounds in the the composite sample were estimated based on selected ion monitoring (SIM) results, extraction recoveries, average air volume sampled, and 3M OVM 3500 passive sampling rates. Forty of the organics were detected and were present in amounts equivalent to airborne concentrations ranging from <1 to 104 μg m−3. Several other compounds were also tentatively identified by full scan analysis. Many of the detected organics have been reported to be associated with activities such as tobacco smoking and the presence of consumer products and plastic materials indoors. The analytical results have been useful in risk assessments and establishment of a new Canadian priority substances list (PSL). 相似文献
725.
726.
Text analysis tools for identification of emerging topics and research gaps in conservation science 总被引:1,自引:0,他引:1
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Martin J. Westgate Philip S. Barton Jennifer C. Pierson David B. Lindenmayer 《Conservation biology》2015,29(6):1606-1614
Keeping track of conceptual and methodological developments is a critical skill for research scientists, but this task is increasingly difficult due to the high rate of academic publication. As a crisis discipline, conservation science is particularly in need of tools that facilitate rapid yet insightful synthesis. We show how a common text‐mining method (latent Dirichlet allocation, or topic modeling) and statistical tests familiar to ecologists (cluster analysis, regression, and network analysis) can be used to investigate trends and identify potential research gaps in the scientific literature. We tested these methods on the literature on ecological surrogates and indicators. Analysis of topic popularity within this corpus showed a strong emphasis on monitoring and management of fragmented ecosystems, while analysis of research gaps suggested a greater role for genetic surrogates and indicators. Our results show that automated text analysis methods need to be used with care, but can provide information that is complementary to that given by systematic reviews and meta‐analyses, increasing scientists’ capacity for research synthesis. 相似文献
727.
Living in a “stethoscope”: burrow-acoustics promote auditory specializations in subterranean rodents
Subterranean mammals rely to a great extent on audition for communication and to be alerted to danger. The only hitherto published
report on burrow acoustics revealed that in tunnels of blind mole-rats (Spalax ehrenbergi), airborne sounds of 440 Hz propagated best whereas lower and higher frequencies were effectively attenuated. Morpho-functional
analyses classify the ear of subterranean mammals as a low-sensitivity and low-frequency device. Concordantly, hearing is
characterized by low sensitivity and a restricted frequency range tuned to low frequencies (0.5–4 kHz). Some authors considered
the restricted hearing in subterranean mammals vestigial and degenerate due to under-stimulation. In contrast to this view
stand a rich (mostly low-frequency) vocal repertoire and progressive structural specializations of the middle and inner ear.
Thus, other authors considered these hearing characteristics adaptive. To test the hypothesis that acoustical environment
in burrows of different species of subterranean mammals is similar, we measured sound attenuation in burrows of Fukomys mole-rats (formerly known as Cryptomys, cf. Kock et al. 2006) of two differently sized species at different locations in Zambia. We show that in these burrows, low-frequency sounds (200–800 Hz)
are not only least attenuated but also their amplitude may be amplified like in a stethoscope (up to two times over 1 m).
We suggest that hearing sensitivity has decreased during evolution of subterranean mammals to avoid over-stimulation of the
ear in their natural environment.
We dedicate this work to Mathias Kawalika, who died in March 2006. 相似文献
728.
Jörn Germer Michael Yongha Boh Marie Schoeffler Philip Amoah 《Waste management (New York, N.Y.)》2010,30(2):185-191
Small scale co-composting of faecal matter from dry toilet systems with shredded plant material and food waste was investigated in respect to heat development and deactivation of faecal indicators under tropical semiarid conditions. Open (uncovered) co-composting of faecal matter with shredded plant material alone did not generate temperatures high enough (<55 °C) to reduce the indicators sufficiently. The addition of food waste and confinement in chambers, built of concrete bricks and wooden boards, improved the composting process significantly. Under these conditions peak temperatures of up to 70 °C were achieved and temperatures above 55 °C were maintained over 2 weeks. This temperature and time is sufficient to comply with international composting regulations. The reduction of Escherichia coli, Enterococcus faecalis and Salmonella senftenberg in test containment systems placed in the core of the compost piles was very efficient, exceeding 5 log10-units in all cases, but recolonisation from the cooler outer layers appeared to interfere with the sanitisation efficiency of the substrate itself. The addition of a stabilisation period by extending the composting process to over 4 months ensured that the load of E. coli was reduced to less than 103 cfu?g and salmonella were undetectable. 相似文献
729.
Gideon Fishelson Philip Graves 《Journal of the Air & Waste Management Association (1995)》2013,63(8):785-789
The role of SO2 and COH (coefficient of haze) as causative factors in hospital emergency room admissions for respiratory and cardiac disease is analyzed using data from Chicago's Cook County Hospital. Some of the findings are that, while COH appears not to affect morbidity, SO2 does, with most important impacts being felt by those with cardiac disease, females, and the youngest and oldest age groups. It is concluded that marginal morbidity damages, about which little had been known, are not high relative to other damage categories. These damages are estimated to be on the order of 10 cents per microgram per cubic meter per person per year. 相似文献
730.
Bryson E. Finch Brett R. Blackwell Derek R. Faust Kimberly J. Wooten Jonathan D. Maul Stephen B. Cox Philip N. Smith 《Environmental science and pollution research international》2013,20(2):1151-1160
The synthetic growth-promoting hormones trenbolone and melengestrol acetate have been detected in the environment near beef cattle feedlots and are reportedly transported via wind-borne particulate matter. Therefore, movement of synthetic hormones from beef cattle feedlots to water bodies via particulate matter is possible. Our objective was to evaluate potential effects of 17α-trenbolone (17α-TB), melengestrol acetate (MGA), and combinations of both on growth, development, and survival of Xenopus laevis larvae. On post-hatch day 2 (stage 33/34), X. laevis larvae were exposed to three nominal concentrations of 17α-TB (10, 100, and 500 ng/L), MGA (1, 10, and 100 ng/L), a combination of both (1/10, 10/100, and 100/500 ng/L MGA/17α-TB), frog embryo teratogenesis assay-Xenopus medium, or a solvent control. Significant increases in all X. laevis growth metrics were observed among larvae in the 1 ng/L MGA?+?10 ng/L 17α-TB and 10 ng/L MGA?+?100 ng/L 17α-TB treatments. Stage of development was increased among larvae in the 1 ng/L MGA?+?10 ng/L 17α-TB treatment group and significantly decreased among those in the 500 ng/L 17α-TB treatment. Total body mass and snout–vent length of X. laevis larvae were significantly reduced in the 100 ng/L MGA and 100 ng/L MGA?+?500 ng/L 17α-TB treatment groups. Larvae exposed to 500 ng/L 17α-TB had decreased total body mass, snout–vent length, and total length. In general, growth measurements decreased with increasing concentration of MGA, 17α-TB, or a combination of both. Survival among all treatments was not significantly different from controls. Amphibians exposed to MGA and 17α-TB in the environment may experience alterations in growth and development. 相似文献