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51.
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53.
The stereoisomers of metolachlor and its two polar metabolites [ethane sulfonic acid (ESA) and oxanilic acid (OXA)] were separated using liquid chromatography-mass spectrometry (LC-MS) and capillary zone electrophoresis (CZE), respectively. The separation of metolachlor enantiomers was achieved using a LC-MS equipped with a chiral stationary phase based on cellulose tris(3,5-dimethylphenyl carbamate) and an atmospheric pressure chemical ionization source operated under positive ion mode. The enantiomers of ESA and OXA were separated using CZE with gamma-cyclodextrin (gamma-CD) as chiral selector. Various CZE conditions were investigated to achieve the best resolution of the ESA and OXA enantiomers. The optimum background CZE electrolyte was found to consist of borate buffer (pH=9) containing 20% methanol (v/v) and 2.5% gamma-CD (w/v). Maximum resolution of ESA and OXA enantiomers was achieved using a capillary temperature of 15 degrees C and applied voltage of 30 kV. The applicability of the LC-MS and CZE methods was demonstrated successfully on the enantiomeric analysis of metolachlor and its metabolites in samples from a soil and water degradation study that was set up to probe the stereoselectivity of metolachlor biodegradation. These techniques allow the enantiomeric ratios of the target analytes to be followed over time during the degradation process and thus will prove useful in determining the role of chirality in pesticide degradation and metabolite formation. 相似文献
54.
Acid resins are residues produced in a recycling process for used oils that was in use in the forties and fifties of the last century. The resin-like material is highly contaminated with mineral oil hydrocarbons, extremely acidic and co-contaminated with substituted and aromatic hydrocarbons, and heavy metals. To determine the potential for microbial biodegradation the acid resin deposit and its surroundings were screened for microbial activity by soil respiration measurements. No microbial activity was found in the core deposit. However, biodegradation of hydrocarbons was possible in zones with a lower degree of contamination surrounding the deposit. An extreme acidophilic microbial community was detected close to the core deposit. With a simple ecotoxicological approach it could be shown that the pure acid resin that formed the major part of the core deposit, was toxic to the indigenous microflora due to its extremely low pH of 0-1. 相似文献
55.
Antonious GF Meyer JE Snyder JC 《Journal of environmental science and health. Part. B》2006,41(8):1383-1391
Increasing concern about persistence and environmental impact of synthetic pesticide residues require development of biodegradable and environmentally safe alternatives. The potential of using fruit extracts of hot pepper as alternatives to synthetic acaricides for controlling the two-spotted spider mite, Tetranychus urticae Koch, is explored in this study. Twenty-four Capsicum accessions (Solanaceae) were screened for their toxicity and repellency to the spider mites. Crude extracts from fruits of C. chinense, C. frutescens, C. baccatum, C. annuum, and C. pubescens were prepared in methanol and tested for their acaricidal properties. Spider mite mortality was greatest (45%) when fruit extract of accession Grif-9169 (C. annuum) was used. Results from diving board bioassays indicated that mites avoided filter paper strips treated with hot pepper extracts from accessions PI-596057 (C. baccatum), PI-195299 (C. annuum), and Grif- 9270 (C. annuum). This investigation suggests that methanolic extracts of these three accessions may have a great potential for repelling spider mites and should be field-tested on a large-scale to assess their value in managing populations of spider mites, which could reduce reliance on synthetic acaricides. An attempt was made to correlate repellency with chemical constituents of fruit extracts of the most repellent accessions to identify chemical sources of repellency. Capsaicin and dihydrocapsaicin, the pungent components of pepper fruit, were not correlated with toxicity or repellency, indicating that these are not likely related to the toxicity or repellency of the pepper fruit extracts. Other, unidentified chemicals are likely responsible for toxicity and repellency to the two-spotted spider mite. 相似文献
56.
Ninon F. V. Meyer Ricardo Moreno Christopher Sutherland J. Antonio de la Torre Helen J. Esser Christopher A. Jordan Melva Olmos Josué Ortega Rafael Reyna-Hurtado Samuel Valdes Patrick A. Jansen 《Conservation biology》2020,34(1):207-219
Habitat fragmentation is a primary driver of wildlife loss, and establishment of biological corridors is a common strategy to mitigate this problem. A flagship example is the Mesoamerican Biological Corridor (MBC), which aims to connect protected forest areas between Mexico and Panama to allow dispersal and gene flow of forest organisms. Because forests across Central America have continued to degrade, the functioning of the MBC has been questioned, but reliable estimates of species occurrence were unavailable. Large mammals are suitable indicators of forest functioning, so we assessed their conservation status across the Isthmus of Panama, the narrowest section of the MBC. We used large-scale camera-trap surveys and hierarchical multispecies occupancy models in a Bayesian framework to estimate the occupancy of 9 medium to large mammals and developed an occupancy-weighted connectivity metric to evaluate species-specific functional connectivity. White-lipped peccary (Tayassu pecari), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), white-tailed deer (Odocoileus virginianus), and tapir (Tapirus bairdii) had low expected occupancy along the MBC in Panama. Puma (Puma concolor), red brocket deer (Mazama temama), ocelot (Leopardus pardalis), and collared peccary (Pecari tajacu), which are more adaptable, had higher occupancy, even in areas with low forest cover near infrastructure. However, the majority of species were subject to ≥1 gap that was larger than their known dispersal distances, suggesting poor connectivity along the MBC in Panama. Based on our results, forests in Darien, Donoso–Santa Fe, and La Amistad International Park are critical for survival of large terrestrial mammals in Panama and 2 areas need restoration. 相似文献
57.
Antarctic krill maintain large population sizes despite dramatic seasonal fluctuations in food availability, but the mechanisms
for this are still debated. The aim of this study was to compare seasonal differences in enzyme activity and respiration rates
of larval and postlarval krill to provide insights into their overwintering strategies. Respiration rates, activity of the
metabolic enzyme citrate synthase (CS), and those of the digestive enzymes laminarinase and total proteinase were measured
in austral summer west of the Antarctic Peninsula, and in autumn in the southwestern Lazarev Sea. The 100-fold difference
in chlorophyll a concentrations between the two studies is representative of the classic transition from a summer bloom to sparse winter conditions.
Correspondingly, adult krill showed reduced respiration rates and CS activity in autumn. However, their digestive enzyme activity
was significantly higher, suggesting more efficient assimilation of food at low food levels. Similar-sized larvae showed no
summer-autumn differences in respiration rates and enzyme activity, supporting suggestions that they need to feed and grow
year-round. However, trends in enzymatic activity varied between the larval stages measured, implying ontogenetic changes
in body structure and function.
Published online: 1 August 2002 相似文献
58.
Genetic monogamy in the common loon (Gavia immer) 总被引:4,自引:0,他引:4
Walter H. Piper David C. Evers Michael W. Meyer Keren B. Tischler Joseph D. Kaplan Robert C. Fleischer 《Behavioral ecology and sociobiology》1997,41(1):25-31
We conducted behavioral observations and genetic analysis on breeding pairs of common loons in the upper Great Lakes region
from 1993 through 1995 to look for behavioral evidence of extrapair copulations (EPCs) and to determine parentage of young.
Pairs remained close to each other (usually within 20 m) during the pre-laying period, leaving little opportunity for EPCs
to occur. Males and females both maintained physical proximity by approaching each other when they became separated. Copulations
were obvious but infrequent, occurring about once every other day during the pre-laying period. Multilocus DNA fingerprinting
was consistent with behavioral findings: 58 young from 47 different families were all genetic offspring of parents that raised
them. Perfect genetic monogamy (genetic parentage of young by parents that rear them) in loons might arise as a consequence
of the need for vigorous territorial defense to prevent territorial takeover.
Received: 8 August 1996 / Accepted after revision: 22 March 1997 相似文献
59.
We describe a portable, non-motorized device for delivering a tracer dye into seawater under field conditions. Dye is ejected at a constant flow rate over a period of tens of minutes. The ejector works in a wide range of ambient pressures without external energy requirements. The flow rate is adjusted simply by varying the length of the delivery tube. The dye streams permitted observations of the upcurrent and downcurrent flow regimes for a filter-feeding crinoid (Comanthus bennetti) living at a depth of 8 m on a coral reef. The results indicate that the crinoid may enhance the rate of particle capture by changing the scale of turbulence in the water passing through the mesh of the filtration fan. 相似文献
60.