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Disinfection of reclaimed water prior to reuse is important to prevent the transmission of pathogens. Chlorine is a widely utilized disinfectant and as such is a leading contender for disinfection of reclaimed water. To understand the risks of chlorination resulting from the potential selection of pathogenic bacteria, the inactivation, reactivation and regrowth rates of indigenous bacteria were investigated in reclaimed water after chlorine disinfection. Inactivation of total coliforms, Enterococcus and Salmonella showed linear correlations, with constants of 0.1384, 0.1624 and 0.057 L/(mg·min) and R2 of 0.7617, 0.8316 and 0.845, respectively. However, inactivation of total viable cells by measurement of metabolic activity typically showed a linear correlation at lower chlorine dose (0-22 (mg·min)/L), and a trailing region with chlorine dose increasing from 22 to 69 (mg·min)/L. Reactivation and regrowth of bacteria were most likely to occur after exposure to lower chlorine doses, and extents of reactivation decreased gradually with increasing chlorine dose. In contrast to total coliforms and Enterococcus, Salmonella had a high level of regrowth and reactivation, and still had 2% regrowth even after chlorination of 69 (mg·min)/L and 24 hr storage. The bacterial compositions were also significantly altered by chlorination and storage of reclaimed water, and the ratio of Salmonella was significantly increased from 0.001% to 0.045% after chlorination of 69 (mg·min)/L and 24 hr storage. These trends indicated that chlorination contributes to the selection of chlorine-resistant pathogenic bacteria, and regrowth of pathogenic bacteria after chlorination in reclaimed water with a long retention time could threaten public health security during wastewater reuse. 相似文献
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Chris E. Johnson Robert J. Petras Richard H. April Thomas G. Siccama 《Water, Air, & Soil Pollution: Focus》2004,4(2-3):579-590
The use of alkyl-Pb additives in gasoline during the 20th century resulted in widespread Pb pollution. The objective of this study was to determine the relative importance of atmospherically deposited Pb and Pb released through weathering to soil Pb pools at the Hubbard Brook Experimental Forest, New Hampshire. We employed a selective extraction method to estimate the amount of Pb that was: water-soluble + exchangeable (EX); inorganically bound (IB); organically bound (ORG); bound to amorphous oxides (AMOX); and bound in crystalline minerals (RES). After normalizing crystalline-Pb concentrations to the immobile element Ti, we estimated that 14.1 kg ha-1 of Pb has been weathered from Hubbard Brook soils in the 12,000–14,000 yr since deglaciation – a long-term average release of 1.0–1.2 g ha-1 a-1. Analysis of Ti-normalized total Pb concentrations indicated a net post-glacial decrease of 7.2 kg ha-1 in the total Pb pool – consisting of a net accumulation of 4.9 kg ha-1 in the O horizon, and a net loss of 12.1 kg ha-1 from mineral soil. Atmospheric deposition of Pb between 1926 and 1989 (estimated as 8.7 kg ha-1) was a major source of Pb in the post-glacial period. Together, long-term weathering release and 20th century atmospheric deposition could account for all of the Pb in the EX, IB, ORG, and AMOX fractions. Lead from gasoline appears to constitute a major fraction of the total Pb burden in Hubbard Brook soils. Periodic analysis of soil Pb fractions may be useful in monitoring the fate of Pb in forest soils. 相似文献
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Leanne J. Flewelling Douglas H. Adams Jerome P. Naar Karen E. Atwood April A. Granholm Sheila N. O’Dea Jan H. Landsberg 《Marine Biology》2010,157(9):1937-1953
In October 2000, a mass mortality of blacktip sharks (Carcharhinus limbatus) and Atlantic sharpnose sharks (Rhizoprionodon terraenovae) in northwest Florida occurred in conjunction with a Karenia brevis red tide bloom. Before this incident, no information existed on red tide-induced shark mortalities or baseline brevetoxin levels in sharks and rays from red tide-endemic areas. We report here that brevetoxin accumulation in live and red tide-killed elasmobranchs is common during K. brevis blooms and non-bloom periods. Strong relationships were found between the frequency of red tide blooms and the average brevetoxin concentrations in elasmobranch tissues. The presence of brevetoxins in Atlantic coast sharks in the absence of documented K. brevis blooms may suggest that blooms are occurring in areas that are not well monitored. Although red tide-related shark mortalities are rarely observed, the presence of brevetoxins in shark embryos raises questions about the effects these toxins may have on the reproductive success of sharks. 相似文献
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Qiyun Zhu April Gu Dan Li Tianmu Zhang Lunhong Xiang Miao He 《Frontiers of Environmental Science & Engineering》2021,15(6):136
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Controls of spatial variation in the prevalence of trematode parasites infecting a marine snail 总被引:2,自引:0,他引:2
Geographic variability in abundance can be driven by multiple physical and biological factors operating at multiple scales. To understand the determinants of larval trematode prevalence within populations of the marine snail host Littorina littorea, we quantified many physical and biological variables at 28 New England intertidal sites. A hierarchical, mixed-effects model identified the abundance of gulls (the final hosts and dispersive agents of infective trematode stages) and snail size (a proxy for time of exposure) as the primary factors associated with trematode prevalence. The predominant influence of these variables coupled with routinely low infection rates (21 of the 28 populations exhibited prevalence <12%) suggest broad-scale recruitment limitation of trematodes. Although infection rates were spatially variable, formal analyses detected no regional spatial gradients in either trematode prevalence or independent environmental variables. Trematode prevalence appears to be predominantly determined by local site characteristics favoring high gull abundance. 相似文献
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Natasha B. Kotliar Bruce W. Baker April D. Whicker Glenn Plumb 《Environmental management》1999,24(2):177-192
Cynomys spp.) have been labeled as keystone species because of their influence on biological diversity and ecosystem function. However,
the validity of several assumptions used to support keystone status is questionable. We review the strength of the evidence
and the magnitude of the prairie dog's effects on ecosystem structure and function. We use this review to reevaluate the keystone
role for prairie dogs. Our goal is to encourage sound management of the prairie dog ecosystem by improving the ecological
foundation of their keystone status. Our review confirms that prairie dogs affect a number of ecosystem-level functions but
that their influence on prairie vertebrates may be less than previously suggested. Species richness and abundance patterns
were variable among plants, mammals, and birds and were not consistently higher on prairie dog colonies compared to uncolonized
areas. In addition, only nine of the 208 species listed in the literature as observed on or near prairie dogs colonies had
quantitative evidence of dependence on prairie dogs. Abundance data indicated opportunistic use of colonies for an additional
20 species. A total of 117 species may have some relationship with prairie dogs, but we lacked sufficient data to evaluate
the strength of this relationship. The remaining 62 species may be accidental or alien to the system. Despite our conclusion
that some prairie dog functions may be smaller than previously assumed, collectively these functions are quite large compared
to other herbivores in the system. We suggest that prairie dogs also provide some unique functions not duplicated by any other
species and that continued decline of prairie dogs may lead to a substantial erosion of biological diversity and landscape
heterogeneity across prairie and shrub-steppe landscapes. Thus, we concur that keystone status for prairie dogs is appropriate
and may aid conservation efforts that help protect species dependent on prairie dogs and support other important ecosystem
functions. 相似文献
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The frequency and intensities of dust exposures in and near farm fields, which potentially contribute to high intensity human exposure events, are undocumented due to the transient nature of local dust plumes and the difficulties of making accurate concentration measurements. The objective of this study is to measure near-field spatial concentrations of the dust plumes emitted during tilling and harvesting of an irrigated cotton field outside of Las Cruces, NM (soil class: fine-loamy, mixed, superactive, thermic Typic Calciargid). A comparison of remote lidar measurements of plumes emitted from cotton field operations with in situ samplers shows a strong agreement between the two techniques: r2 = 0.79 for total suspended particulates (TSP) and r2 = 0.61 for particulate matter with diameter less than or equal to 10 microm (PM10). Plume movement was dependent on the short-term wind field and atmospheric stability. Horizontal spread rate of the plumes, determined from lidar measured Gaussian dispersion parameters, was less than expected by a factor of 7. Thus, in-plume downwind concentrations were higher than expected. Vertical dispersion was dependent on the rise of "cells" of warm air convecting off the soil surface. On a windy day, discing the field showed TSP and PM10 concentrations at the source itself of up to 176 microg m(-3) and 120 microg m(-3), respectively. These resulted in in-plume peak TSP concentrations of about 1.22 microg m(-3) at 10 m downwind and 0.33 microg m(-3) at 100 m downwind. The measured concentrations highlight a potential exposure risk to people in and around farming operations. 相似文献
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Sather ME Mathew J Nguyen N Lay J Golod G Vet R Cotie J Hertel T Aaboe E Callison R Adam J Keese D Freise J Hathcoat A Sakizzie B King M Lee C Oliva S San Miguel G Crow L Geasland F 《Journal of environmental monitoring : JEM》2008,10(11):1319-1325
Ambient ammonia monitoring using Ogawa passive samplers was conducted in the Four Corners area and eastern Oklahoma, USA during 2007. The resulting data will be useful in the multipollutant management of ozone, nitrogen oxides, and visibility (atmospheric regional haze) in the Four Corners area, an area with growing oil/gas production and increasing coal-based power plant construction. The passive monitoring data also add new ambient ammonia concentration information for the U.S. and will be useful to scientists involved in present and future visibility modeling exercises. Three week integrated passive ammonia samples were taken at five sites in the Four Corners area and two sites in eastern Oklahoma from December, 2006 through December, 2007 (January, 2008 for two sites). Results show significantly higher regional background ammonia concentrations in eastern Oklahoma (1.8 parts per billion (ppb) arithmetic mean) compared to the Four Corners area (0.2 ppb arithmetic mean). Annual mean ammonia concentrations for all Four Corners area sites for the 2007 study ranged from 0.2 ppb to 1.5 ppb. Peak ambient ammonia concentrations occurred in the spring and summer in both areas. The passive samplers deployed at the Stilwell, Oklahoma site compared favorably with other passive samplers and a continuous ammonia monitoring instrument. 相似文献
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