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191.
Movement of liquor constituents from animal-waste lagoons has the potential to degrade ground water quality. The depth of movement and concentrations of lagoon-liquor constituents in the soil underlying three cattle (Bos taurus)-waste retention lagoons and one swine (Sus scrofa)-waste lagoon were determined. Samples were taken by using a direct-push coring machine, dissected by depth, and analyzed for total N, organic C, CaCO3, pH, cation exchange capacity (CEC), texture, and extractable NO3, NH(4), P, Cl, Ca, Mg, K, and Na. Ammonium N concentrations were greatest in the upper 0.5 m of soil under all four lagoons with concentrations ranging from 94 to 1139 mg kg(-1). Organic N was determined to make up between 39 and 74% of the total N beneath all lagoons. The swine lagoon had 2.4 kg N m(-2) in the underlying soil whereas the cattle lagoon with highest quantity of N had 1.2 kg N m(-2) in the underlying soil. Although N concentrations decreased with depth, N was greater than expected background levels at the bottom of some cores, indicating that the sampling efforts did not reach the bottom of the N plume. Nitrate N concentrations were generally less than 5 mg kg(-1) immediately below the lagoon floor. In the uppermost 0.5 m of soil underlying the swine and three cattle lagoons, NH4+ occupied 44% and between 1 and 22% of the soil cation exchange sites, respectively. The depth of movement of N under these lagoons, as much as 4 m, may pose remediation difficulties at lagoon closure. 相似文献
192.
Prevalence of low back pain in three occupational groups in Shanghai, People's Republic of China 总被引:5,自引:0,他引:5
PROBLEM: Low back pain (LBP) is one of the most prevalent work-related conditions affecting employed populations in developed countries, yet little is known about this condition among the world's largest, single-nation labor force: The People's Republic of China. METHOD: This is a cross-sectional study of the prevalence of low back pain (LBP) among garment workers, battery/kiln workers, and teachers in Shanghai, People's Republic of China. Data were collected by personal interview and physical examination at six work sites. The overall response rate was 78%. RESULTS: The overall (N=383) self-reported annual prevalence of LBP symptoms lasting 24 hours or more was 50%. Garment workers had a higher annual prevalence of LBP (74%) than teachers (40%), prevalence ratio (PR=1.9, 95% CI=1.4-2.4). DISCUSSION: The overall annual prevalence of self-reported LBP (50%) was higher than that reported among 50 other Chinese employed study populations (30%). Healthy worker effects may have limited the conclusions from this cross-sectional study. SUMMARY: These results suggest that LBP is a prevalent condition in Chinese workers and that more work should be done to estimate its impact on the Chinese workforce. The findings for garment workers were consistent with increased risk of LBP among persons doing work in fixed, sedentary postures. 相似文献
193.
Investigation of retardation effects on the titanium dioxide photodegradation system 总被引:1,自引:0,他引:1
The photocatalytic bleaching of dyes using TiO2 has appeared promising in laboratory studies, but little attention has been focused on whether other species such as might be found in wastewater have a deleterious effect on the photobleaching. This study describes the effects that result from the presence of ionic species, organic solvents and humic substances on the photobleaching of several dyes. The manner in which the photobleaching was affected by the presence of adventitious materials was carefully examined with an eye toward elucidating the mechanistic origin of the loss of the photochemical efficiency in the reaction. The overall retardation effects can be attributed to the combination of light attenuation, inhibition and competition effects. 相似文献
194.
Sourcing sediment using multiple tracers in the catchment of Lake Argyle,Northwestern Australia 总被引:5,自引:0,他引:5
Control of sedimentation in large reservoirs requires soil conservation at the catchment scale. In large, heterogeneous catchments,
soil conservation planning needs to be based on sound information, and set within the framework of a sediment budget to ensure
that all of the potentially significant sources and sinks are considered.
The major sources of sediment reaching the reservoir, Lake Argyle, in tropical northwestern Australia, have been determined
by combining measured sediment fluxes in rivers with spatial tracer-based estimates of proportional contributions from tributaries
of the main stream entering the lake, the Ord River. The spatial tracers used are mineral particle magnetics, the strontium
isotopic ratio, and the neodymium isotopic ratio. Fallout of 137Cs has been used to estimate the proportion of the sediment in Lake Argyle eroded from surface soils by sheet and rill erosion,
and, by difference, the proportion eroded from subsurface soils by gully and channel erosion. About 96% of the sediment in
the reservoir has come from less than 10% of the catchment, in the area of highly erodible soils formed on Cambrian-age sedimentary
rocks. About 80% of the sediment in the reservoir has come from gully and channel erosion. A major catchment revegetation
program, designed to slow sedimentation in the reservoir, appears to have had little effect because it did not target gullies,
the major source of sediment. Had knowledge of the sediment budget been available before the revegetation program was designed,
an entirely different approach would have been taken. 相似文献
195.
196.
Variation in the intensity of predation across the well-known environmental gradient of freshwater habitats from small, ephemeral ponds to large, permanent lakes is a key factor in the development and maintenance of aquatic community structure. Here, we present data on the distribution and abundance of four species of Chaoborus (Diptera: Chaoboridae) across this environmental gradient. Chaoborus show a distinct pattern of species sorting when aquatic systems are divided into fish and fishless environments, and this pattern is consistent with species traits known to influence their vulnerability to fish predation (i.e., pigmentation, diel vertical migration [DVM] behavior, and body size). To test whether fish are the drivers of this pattern, we created a gradient in fish density by stocking bluegill sunfish (Lepomis macrochirus) into 15 experimental ponds in southwestern Michigan, USA, and then allowed Chaoborus species to colonize. There was clear evidence of species sorting along the predation gradient; Chaoborus americanus was most abundant in the fishless ponds, C. flavicans was neutral in response to fish, and C. punctipennis and C. albatus were most abundant at high fish biomass, a response consistent with their field pattern. Furthermore, prey preference experiments confirm that size selective predation and differences in Chaoborus species traits contribute to the pattern of Chaoborus abundance and distribution. 相似文献
197.
Sheppard PR Speakman RJ Ridenour G Glascock MD Farris C Witten ML 《Environmental geochemistry and health》2007,29(5):405-412
Spatial patterns of tungsten and cobalt are described for surface dust of Fallon, Nevada, where a cluster of childhood leukemia
has been ongoing since 1997. In earlier research, airborne tungsten and cobalt was shown to be elevated in total suspended
particulates in Fallon. To fine-tune the spatial patterns of tungsten and cobalt deposition in Fallon, surface dust was collected
in a grid pattern within as well as outside of Fallon to establish background concentrations of metals. In surface dust, tungsten
and cobalt show sharp peaks (934 ppm and 98 ppm, respectively) within Fallon just north of highway 50 and west of highway
95. These two peaks overlap spatially, and given the grid pattern used for collecting surface dust, the source area of these
two airborne metals can be pinpointed to the vicinity of hard-metal industry located north of highway 50 and west of highway
95. Fallon is distinctive in west central Nevada because of high airborne tungsten and cobalt particulates, and given its
cluster of childhood leukemia, it stands to reason that additional biomedical research is in order to test directly the leukogenicity
of combined airborne tungsten and cobalt particulates. 相似文献
198.
199.
Tony Svejcar Chad Boyd Kirk Davies Matthew Madsen Jon Bates Roger Sheley Clayton Marlow David Bohnert Mike Borman Ricardo Mata-Gonzàlez John Buckhouse Tamzen Stringham Barry Perryman Sherman Swanson Kenneth Tate Mel George George Ruyle Bruce Roundy Chris Call Kevin Jensen Karen Launchbaugh Amanda Gearhart Lance Vermeire John Tanaka Justin Derner Gary Frasier Kris Havstad 《Environmental management》2014,53(6):1035-1038
In a previous article, Beschta et al. (Environ Manag 51(2):474–491, 2013) argue that grazing by large ungulates (both native and domestic) should be eliminated or greatly reduced on western public lands to reduce potential climate change impacts. The authors did not present a balanced synthesis of the scientific literature, and their publication is more of an opinion article. Their conclusions do not reflect the complexities associated with herbivore grazing. Because grazing is a complex ecological process, synthesis of the scientific literature can be a challenge. Legacy effects of uncontrolled grazing during the homestead era further complicate analysis of current grazing impacts. Interactions of climate change and grazing will depend on the specific situation. For example, increasing atmospheric CO2 and temperatures may increase accumulation of fine fuels (primarily grasses) and thus increase wildfire risk. Prescribed grazing by livestock is one of the few management tools available for reducing fine fuel accumulation. While there are certainly points on the landscape where herbivore impacts can be identified, there are also vast grazed areas where impacts are minimal. Broad scale reduction of domestic and wild herbivores to help native plant communities cope with climate change will be unnecessary because over the past 20–50 years land managers have actively sought to bring populations of native and domestic herbivores in balance with the potential of vegetation and soils. To cope with a changing climate, land managers will need access to all available vegetation management tools, including grazing. 相似文献
200.
Roger A. Nichols Gary L. Ketcheson 《Journal of the American Water Resources Association》2013,49(6):1367-1384
A federal, state, and private partnership leveraged resources and employed a long‐term, systematic approach to improve aquatic habitat degraded by decades of intensive forest management in Finney Creek, a tributary to the Skagit River of Northwest Washington State. After more than a decade of work to reduce sediment sources and the risk of landslides within the watershed, log jam installation commenced in 1999 and progressed downstream through 2010. Log jam design was adapted as experience was gained. A total of 181 log jams, including 60 floating log ballasted jams, were constructed along 12 km of channel. The goal was to alter hydraulic processes that affect aquatic habitat formation along 39 km of stream with emphasis on 18.5 km of lower Finney Creek. Aquatic habitat surveys over a five‐year period show an increase in the area of large pools and an accompanying increase in residual and maximum pool depth in the lower river reach. Channel cross sections show a generally deeper channel at the log jams, better channel definition in the gravel deposits at the head of the log jams, and improved riffle and thalweg development below the log jams. Stream temperature in the upper river decreased by 1.0°F in the first three years, and 1.1°F in the lowest treated reach over nine years. There is a trend of less stream heating over the restoration time period. Photo points show that riparian vegetation is recolonizing gravel bars. 相似文献