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71.
Joseph Khoury Maria Pang Connie Young Anita Pandit Steve Carr Dwayne Fischer James Stahl 《Water environment research》2008,80(1):53-59
Dechlorinating agents and pH adjustment are often used to preserve wastewater samples for cyanide analysis. The effects of four approved preservation protocols on the results of the total cyanide analysis of effluents from four water reclamation plants were examined. The results differed widely, and a clear pattern emerged. Immediate analysis without pH adjustment generally gave total cyanide concentrations below the reporting limit of 5 microg/L, irrespective of the dechlorinating agents used. When the pH was adjusted to > or =12, a slight increase in the measured total cyanide concentration was observed when thiosulfate was used to dechlorinate the samples, and a significant increase (>10 microg/L) was observed when arsenite was used as the dechlorinating agent. These results provide evidence that approved preservation protocols may give rise to cyanide formation in chlorinated wastewater effluent matrices. 相似文献
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Dissolved organic matter in pore water of freshwater sediments: effects of separation procedure on quantity, quality and functionality 总被引:2,自引:0,他引:2
Pore water was separated either with or without water extraction prior to centrifugation (7600 or 20 000 × g) in order to investigate the effects of separation procedure on the amount and properties of dissolved organic matter (DOM i.e. the material passing through a 0.45-μm filter) in three freshwater sediments. On the basis of solubility in alkaline, organic matter was concluded to compose of humic substances in two (S1 and S3) and of humin (S2) in one of the sediments. DOM in the samples was quantified by total organic carbon measurement. Specific UV-absorption (SUVA) and high performance size exclusion chromatography (HPSEC) analyses were used to characterize DOM. Sorption of pyrene was used as a measure for functionality of DOM. Both water extraction and centrifugation speed were shown to affect the properties of DOM; however, the effects were sediment dependent. Water extraction increased the amount of DOM separated from the two sediments that had humic character (S1 and S3). In most cases water extraction increased SUVA and shifted the molecular size distribution of DOM towards larger sizes. The separation procedure had also an effect on the functionality of DOM. In water extracted samples of S2 and S3 the sorption of pyrene was higher than in the corresponding samples separated without water extraction, whereas in S1 similar effect was not found. Generally, centrifugation speed had smaller effects on the properties of DOM than water extraction. The fact that the effects of separation procedure on DOM depend on the sediment characteristics complicates the comparison between samples and evaluation of functionality in field conditions. 相似文献
76.
Anita Aisenberg Carmen Viera Fernando G. Costa 《Behavioral ecology and sociobiology》2007,62(1):29-35
Sexual selection theory predicts that a higher investment in offspring will turn females into the selective sex, while males
will compete for accessing and courting them. However, there are exceptions to the rule. When males present a high reproductive
investment, sex roles can reverse from typical patterns, turning males into the choosy sex, while females locate males and
initiate courtship. In many spiders, males are smaller than females, wandering in search of sedentary females and maximizing
the number of copulations. In the present study, we present findings on the sand-dwelling wolf spider, Allocosa brasiliensis, evidencing a reversal in typical courtship roles reported for the first time in spiders. Males were bigger than females.
Females located males and initiated courtship. Copulation always occurred in male burrows and took place mainly in long burrows.
Males donated their burrows to the females after copulation, closing the entrance before leaving with female cooperation from
inside. Males would provide females with a secure place for ovipositing, being exposed to predation and diminishing their
future mating possibilities until constructing a new burrow. The cost of vacating the burrow and losing the refuge in an unpredictable
habitat, such as sand dunes, would explain the courtship roles reversal in this spider species. Results turn A. brasiliensis as a promising model for discussing the determinants of sex roles and the pressures that drive their evolution and maintenance.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
77.
Herzke D Gabrielsen GW Evenset A Burkow IC 《Environmental pollution (Barking, Essex : 1987)》2003,121(2):293-300
The levels of polychlorinated camphenes (toxaphenes) were investigated in liver samples from 18 glaucous gulls (Larus hyperboreus) from Bj?rn?ya (74 degrees N, 19 degrees E) and four individuals from Longyearbyen (78 degrees N, 15 degrees E). Additionally brominated flame retardants (BFRs), PCBs and chlorinated pesticides were investigated in liver and intestinal contents of 15 of the glaucous gulls from Bj?rn?ya. Of the analysed BFRs only 2,2',4,4'-tetra- and 2,2',4,4',5-pentabrominated diphenylethers (PBDE 47 and 99) could be detected. The concentrations ranged between 2 and 25 ng/g ww. In addition, high resolution measurements with GC/HRMS revealed the existence of several, not quantified, PBDEs and polybrominated biphenyls (PBBs) congeners in the samples. B9-1679 and B8-1413 were the dominating toxaphenes with median concentrations of 8 and 15 ng/g ww. Concentrations of toxaphenes and PBDEs were up to 100-times lower than the concentrations of PCB and some of the pesticides. PCB and p,p/-DDE constituted 90% of the contaminants found. 相似文献
78.
Provisional physical habitat indices were developed and validatedfor Maryland Coastal and Non-Coastal Plain streams using variables (commonly called metrics) that best discriminated reference and degraded conditions based on biological, chemicaland land use data from the 1994–97 Maryland Biological Stream Survey (MBSS). These habitat indices contained variables that described structural, hydrological, vegetative and aesthetic components of stream habitat. Variables with the best discriminatory power for Coastal Plain streams were: instream habitat, velocity/depth diversity, pool/glide/eddy quality, embeddedness, maximum depth and aesthetic rating. Physical habitat variables with the best discriminatory power for Non-Coastal Plain sites were: instream habitat, velocity/depth diversity, riffle/run quality, embeddedness, number of rootwads and aesthetic rating. The overall classification efficiency forindex validation was 76% for both indices pooled over both strata. Scaled physical habitat index values (0–100) for bothstrata identified nearly twice as many good sites (31%) as very poor sites (16%). More than half the Maryland sites werein the poor to fair range (53%). 相似文献
79.
The use of chemical signals in a sexual context is widespread in the animal kingdom. Most studies in spiders report the use
of female pheromones that attract potential sexual partners. Allocosa brasiliensis and Allocosa alticeps are two burrowing wolf spiders that show sex-role reversal. Females locate male burrows and initiate courtship before males
perform any detectable visual or vibratory signal. So, females of these species would be detecting chemical or mechanical
cues left by males. Our objective was to explore the potential for male pheromones to play a role in mate detection in A. brasiliensis and A. alticeps. We designed two experiments. In Experiment 1, we tested the occurrence of male contact pheromones by evaluating female courtship
when exposed to empty burrows constructed by males or females (control). In Experiment 2, we tested the existence of male
volatile pheromones by evaluating female behaviour when exposed to artificial burrows connected to tubes containing males,
females or empty tubes (control). Our results suggest the occurrence of male volatile pheromones that trigger female courtship
in both Allocosa species. The sex-role reversal postulated for these wolf spiders could be driving the consequent reversal in typical pheromone-emitter
and detector roles expected for spiders. 相似文献
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