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391.
Roy V. Rea Kenneth N. Child David P. Spata Douglas MacDonald 《Environmental management》2010,46(1):101-109
Plants cut at different times produce resprouts that vary in their nutritional value relative to when they are cut. To determine
how vegetation management in transportation (road and rail) corridors at different times of the year could influence browse
quality in the years following cutting, and how this could potentially influence encounters between herbivores and vehicles,
we undertook a 3-year study. In 2001, at a wildlife viewing area near Prince George, British Columbia, Canada, we established
a control area and treatment areas where shrubs and trees that are used as food by moose (Alces alces) were cut at the beginning of June, July, August, September, and October. In the fall, moose were most often observed browsing
the resprouts of plants cut in August (years 1 and 2 post-treatment) and September (year 3). Cumulative winter track counts
were highest in the uncut control area in the years following cutting. Spring pellet counts revealed that most pellets were
deposited in the uncut (years 1 and 2) and August-cut (year 3) areas during winter. With the exception of the first year after
cutting, browse removal by moose was highest for plants cut later in the growing season. Overall, our findings suggest that
following cutting, plants cut later in the year are selected more often by moose relative to those cut earlier. To reduce
browse use of corridor vegetation in areas where concerns for moose-vehicle collisions exist, we recommend that vegetation
maintenance activities be conducted in the early summer months of June and July. 相似文献
392.
Lake variability: key factors controlling mercury concentrations in New York State fish 总被引:2,自引:0,他引:2
Simonin HA Loukmas JJ Skinner LC Roy KM 《Environmental pollution (Barking, Essex : 1987)》2008,154(1):107-115
A 4year study surveyed 131 lakes across New York State beginning in 2003 to improve our understanding of mercury and gather information from previously untested waters. Our study focused on largemouth and smallmouth bass, walleye and yellow perch, common piscivorous fish shown to accumulate high mercury concentrations and species important to local fisheries. Fish from Adirondack and Catskill Forest Preserve lakes generally had higher mercury concentrations than those from lakes in other areas of the state. Variability between nearby individual lakes was observed, and could be due to differences in water chemistry, lake productivity or the abundance of wetlands in the watershed. We found the following factors impact mercury bioaccumulation: fish length, lake pH, specific conductivity, chlorophyll a, mercury concentration in the water, presence of an outlet dam and amount of contiguous wetlands. 相似文献
393.
Sequential sorption of lead and cadmium in three tropical soils 总被引:2,自引:0,他引:2
It is important to examine mechanisms of Pb and Cd sorption in soils to understand their bioavailability. The ability of three tropical soils to retain Pb, Cd, and Ca was evaluated. The objectives of this study were to (1) determine the extent to which soil sorption sites are metal specific, (2) investigate the nature of reactions between metals and soil surfaces, and (3) identify how metals compete for sorption sites when they are introduced to soils sequentially or concurrently. Lead was shown to be much less exchangeable than Cd and inhibited Cd sorption. Cadmium had little effect on Pb sorption, though both Ca and Cd inhibited the adsorption of Pb at exchange sites. Lead appears to more readily undergo inner-sphere surface complexation with soil surface functional groups than either Cd or Ca. Thus, regardless of when Pb is introduced to a soil, it should be less labile than Cd. 相似文献
394.
Pearl Weinberger Dan Sher Roy Greenhalgh 《Journal of environmental science and health. Part. B》2013,48(2):269-281
Abstract Fresh and estuarine water algae maintained in laboratory microcosms simulating river‐lake/estuary‐bay systems were exposed to 14C‐fenitrothion formulated with Atlox and tank mixed with Aerotex or Dowanol (11.5:1.5:1.5 w/v/v). Generally, the tank mix co‐solvents determined the amount of uptake and the array of derivatives formed by the algae. Typically, exposed to an Aerotex mix the ratio of ethyl acetate extractable (NP) fraction : ethyl acetate unextractable (P) fraction was as 3.5:1.0, exposed to a Dowanol mix the ratio was as 1.5:1.0. Within any comparable time period, fresh water algae turned over more of the C‐ring of fenitrothion than the estuarine genera. Turn‐over was enhanced when Aerotex was the tank mix co‐solvent. 相似文献
395.
P. Bhattacharyya K. S. Roy S. Neogi M. C. Manna T. K. Adhya K. S. Rao A. K. Nayak 《Environmental monitoring and assessment》2013,185(10):8659-8671
Changes in the soil labile carbon fractions and soil biochemical properties to elevated carbon dioxide (CO2) and temperature reflect the changes in the functional capacity of soil ecosystems. The belowground root system and root-derived carbon products are the key factors for the rhizospheric carbon dynamics under elevated CO2 condition. However, the relationship between interactive effects of elevated CO2 and temperature on belowground soil carbon accrual is not very clear. To address this issue, a field experiment was laid out to study the changes of carbon allocation in tropical rice soil (Aeric Endoaquept) under elevated CO2 and elevated CO2 + elevated temperature conditions in open top chambers (OTCs). There were significant increase of root biomass by 39 and 44 % under elevated CO2 and elevated CO2 + temperature compared to ambient condition, respectively. A significant increase (55 %) of total organic carbon in the root exudates under elevated CO2 + temperature was noticed. Carbon dioxide enrichment associated with elevated temperature significantly increased soil labile carbon, microbial biomass carbon, and activities of carbon-transforming enzyme like β-glucosidase. Highly significant correlations were noticed among the different soil enzymes and soil labile carbon fractions. 相似文献
396.
Allison H. Roy William D. Shuster 《Journal of the American Water Resources Association》2009,45(1):198-209
Abstract: Although total impervious area (TIA) is often used as an indicator of urban disturbance, recent studies suggest that the subset of impervious surfaces that route stormwater runoff directly to streams via stormwater pipes, called directly connected impervious area (DCIA), may be a better predictor of stream ecosystem alteration. We evaluated the differences between TIA and DCIA in the Shepherd Creek catchment, a small (1.85‐km2), suburban basin in Cincinnati, Ohio. Imperviousness determinations were calculated based on publicly available geographic information system (GIS) data and parcel‐scale field assessments, and these direct assessments were compared to DCIA calculated from published, empirical relationships. Impervious and semi‐impervious area comprised 13.1% of the catchment area, with 56.3% of the impervious area connected. When summarized by subcatchments (0.26‐1.85 km2), TIA measured in the field (11‐23%) was considerably higher than that calculated from the National Land Cover Data Imperviousness Layer (7‐18%). In contrast, TIA calculated based on aerial photos was similar to TIA calculated from field assessments, thus indicating that photo interpretation may be adequate for catchment‐scale (>25 ha) TIA determinations. While these GIS data sources can be used to calculate TIA, on‐site assessments were necessary to accurately determine DCIA within residential parcels. There was a wide variation in percent connectivity across parcels, and, subsequently, DCIA was not accurately predicted from empirical relationships with TIA. We discuss applications of DCIA data that highlight the importance of parcel‐scale field assessments for managing suburban watersheds. 相似文献
397.
398.
Specimens of the edible crab Cancer pagurus (L.) collected in the Skagerrak, Denmark, between June and August 1990 were examined in the laboratory. Impairment of respiratory function after pre-exposure (7 d) to sub-lethal concentrations of Cu and Zn (0.4 mg l-1) was only detectable during hypoxic exposure [PO2 (partial pressure of oxygen) =60 torr]. This was indicated by a decrease in the transfer factor (TO2), due principally to an increase in the PO2 differential across the gills. Cu and Zn exposure did not cause significant changes in ventilation or perfusion although there was some indication that cardiac output may increase in respiratory-impaired individuals. After 28 d exposure no difference was noted in the respiratory responses to hypoxia of treated and untreated crabs. It is concluded that respiratory impairment was due to an increase in the diffusion barrier thickness at the gills and that this was reversible even during continued exposure to trace metal contamination. 相似文献
399.
The association between ‘faint-positive’ amniotic fluid acetylcholinesterase and fetal malformations
Yoel Sadovsky MD Michelle L. Robbin Barbara F. Crandall Roy A. Filly Mitchell S. Golbus 《黑龙江环境通报》1993,13(11):1071-1074
The finding of a ‘faint-positive’ acetylcholinesterase band in amniotic fluid samples of women at 15 weeks' gestation or above is associated with an increased risk of fetal abnormalities, most commonly gastroschisis. This finding warrants a targeted sonographic evaluation, in order to rule out significant fetal malformations. 相似文献
400.
Roy C. Sidle Alan J. Campbell 《Journal of the American Water Resources Association》1985,21(6):909-917
Suspended sediment data from a 154 ha watershed on northeast Chichagof Island, Alaska, were collected over three fall storm seasons from 1980 to 1982. Sediment rating curves for nine pooled storms explained less than 34 percent of the variation in total suspended solids (TSS). Significantly higher concentrations of suspended sediment occurred during the rising limb of storm hydrographs than for similar flows on the falling limb, accounting for hysteresis loops in TSS versus streamflow plots for individual storms. These hysteresis loops were wider during early season storms, indicating that easily transportable fine sediment may have been flushed from the upper portion of channel banks and from behind large organic debris during early season peak flows. Regression relationships (TSS versus Q) developed for the highest stormflows (> 1 m3/s) had steeper slopes than the lower stormflows (< 1 m3/s). Turbidity correlated well (r=0.94) with TSS for all storm-flow data combined. Organic matter constituted an average of 35 percent (by weight) of TSS for all water quality samples. 相似文献