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111.
Kyle R. Mankin Charles D. Ikenberry 《Journal of the American Water Resources Association》2004,40(6):1527-1535
ABSTRACT: Wetlands that treat holding pond effluent can be designed to utilize the pond storage capacity to allow flexibility in system management. Management of a wetland as a sequencing batch reactor can simplify operation and control detention times, but little performance data on such systems are available. The objective of this study was to evaluate the batch reactor wetland concept by quantifying removal of chemical oxygen demand (COD), total suspended sediments (TSS), total nitrogen (TN), ammonium (NH4), nitrate (NO3), total phosphorus (TP), and orthophosphate (PO4) and by assessing the suitability of first‐order kinetics. Weekly samples were collected following batch loadings of wetland cells with high concentration or low concentration dairy holding pond wastewater during both fall and spring seasons. During three‐week batch periods without plants, overall mass removal averaged 54 percent for COD, 58 percent for TSS, 90 percent for TN, 72 percent for NH4, ‐54 percent for NO3, 38 percent for TP, and ‐8 percent for PO4. Best fit, first‐order kinetic rate constant (k) and background concentration (C*) for COD varied by season, with k = 0.024/d and C*= 0 mg/l in fall and k = 0.056/d and C*= 200 mg/l in spring. Ammonium exhibited a consistent C*= 0 mg/l but had variable rate constants of k = 0.121/d for low concentration treatments and k = 0.079/d for high concentration treatments. Using first‐order kinetics was also appropriate for TN, with k = 0.061/d and C*= 0 mg/l for all loadings and seasons, but was not consistently appropriate for TP or PO4. These results support the use of first‐order kinetics to describe treatment in batch reactor wastewater treatment wetlands without vegetation, perhaps during the establishment phase or in open water zones of vegetated wetlands. Further work is needed to assess the effects of vegetation. 相似文献
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Assessing the carbon balance of circumpolar Arctic tundra using remote sensing and process modeling. 总被引:1,自引:0,他引:1
Stephen Sitch A David McGuire John Kimball Nicola Gedney John Gamon Ryan Engstrom Annett Wolf Qianlai Zhuang Joy Clein Kyle C McDonald 《Ecological applications》2007,17(1):213-234
This paper reviews the current status of using remote sensing and process-based modeling approaches to assess the contemporary and future circumpolar carbon balance of Arctic tundra, including the exchange of both carbon dioxide and methane with the atmosphere. Analyses based on remote sensing approaches that use a 20-year data record of satellite data indicate that tundra is greening in the Arctic, suggesting an increase in photosynthetic activity and net primary production. Modeling studies generally simulate a small net carbon sink for the distribution of Arctic tundra, a result that is within the uncertainty range of field-based estimates of net carbon exchange. Applications of process-based approaches for scenarios of future climate change generally indicate net carbon sequestration in Arctic tundra as enhanced vegetation production exceeds simulated increases in decomposition. However, methane emissions are likely to increase dramatically, in response to rising soil temperatures, over the next century. Key uncertainties in the response of Arctic ecosystems to climate change include uncertainties in future fire regimes and uncertainties relating to changes in the soil environment. These include the response of soil decomposition and respiration to warming and deepening of the soil active layer, uncertainties in precipitation and potential soil drying, and distribution of wetlands. While there are numerous uncertainties in the projections of process-based models, they generally indicate that Arctic tundra will be a small sink for carbon over the next century and that methane emissions will increase considerably, which implies that exchange of greenhouse gases between the atmosphere and Arctic tundra ecosystems is likely to contribute to climate warming. 相似文献
115.
Kyle E. Juracek Joan F Kenny 《Journal of the American Water Resources Association》1993,29(6):973-979
ASSTRACT: As part of its mission, the U.S. Geological Survey conducts water-resources research. Site-specific and aggregate water-use data are used in the Survey's National Water-Use Information Program and in various hydrologic investigations. Both types of activities have specific requirements in terms of water-use data access, analysis, and display. In Kansas, the Survey obtains water-use information from several sources. Trpically, this information is in a format that is not readily usable by the Survey. Geographic information system (GIS) technology is being used to restructure the available water-use data into a format that allows users to readily access and summarize site-specific water-use data by source (i.e., surface or ground water), type of use, and user-defined area. 相似文献
116.
Kyle R. Mankin Daniel M. Ngandu Charles J. Barden Stacy L. Hutchinson Wayne A. Geyer 《Journal of the American Water Resources Association》2007,43(5):1108-1116
Abstract: Riparian buffer forests and vegetative filter strips are widely recommended for improving surface water quality, but grass‐shrub riparian buffer system (RBSs) are less well studied. The objective of this study was to assess the influence of buffer width and vegetation type on the key processes and overall reductions of total suspended solids (TSS), phosphorus (P), and nitrogen (N) from simulated runoff passed through established (7‐year old) RBSs. Nine 1‐m RBS plots, with three replicates of three vegetation types (all natural selection grasses, two‐segment buffer with native grasses and plum shrub, and two‐segment buffer with natural selection grasses and plum shrub) and widths ranging from 8.3 to 16.1 m, received simulated runoff having 4,433 mg/l TSS from on‐site soil, 1.6 mg/l total P, and 20 mg/l total N. Flow‐weighted samples were collected by using Runoff Sampling System (ROSS) units. The buffers were very efficient in removal of sediments, N, and P, with removal efficiencies strongly linked to infiltration. Mass and concentration reductions averaged 99.7% and 97.9% for TSS, 91.8% and 42.9% for total P, and 92.1% and 44.4% for total N. Infiltration alone could account for >75% of TSS removal, >90% of total P removal, and >90% of total N removal. Vegetation type induced significant differences in removal of TSS, total P, and total N. These results demonstrate that adequately designed and implemented grass‐shrub buffers with widths of only 8 m provide for water quality improvement, particularly if adequate infiltration is achieved. 相似文献
117.
Yu YANG Zhicheng YU Takayuki NOSAKA Kyle DOUDRICK Kiril HRISTOVSKI Pierre HERCKES Paul WESTERHOFF 《Frontiers of Environmental Science & Engineering》2015,9(5):823
Increasing production and use of carbonaceous nanomaterials (NMs) will increase their release to the sewer system and to municipal wastewater treatment plants. There is little quantitative knowledge on the removal of multi-walled carbon nanotubes (MWCNTs), graphene oxide (GO), or few-layer graphene (FLG) from wastewater into the wastewater biomass. As such, we investigated the quantification of GO and MWCNTs by UV-Vis spectrophotometry, and FLG using programmable thermal analysis (PTA), respectively. We further explored the removal of pristine and oxidized MWCNTs (O-MWCNTs), GO, and FLG in a biomass suspension. At least 96% of pristine and O-MWCNTs were removed from the water phase through aggregation and 30-min settling in presence or absence of biomass with an initial MWCNT concentration of 25 mg·L−1. Only 65% of GO was removed with biomass concentration at or above 1,000 mg·L−1 as total suspended solids (TSS) with the initial GO concentration of 25 mg·L−1. As UV-Vis spectrophotometry does not work well on quantification of FLG, we studied the removal of FLG at a lower biomass concentration (50 mg TSS·L−1) using PTA, which showed a 16% removal of FLG with an initial concentration of 1 mg·L−1. The removal data for GO and FLG were fitted using the Freundlich equation (R2 = 0.55, 0.94, respectively). The data presented in this study for carbonaceous NM removal from wastewater provides quantitative information for environmental exposure modeling and life cycle assessment. 相似文献
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Kyle E. Juracek 《Journal of the American Water Resources Association》2000,36(3):633-645
ABSTRACT: The stability of the Neosho River channel downstream from John Redmond Dam, in southeast Kansas, was investigated using multiple‐date aerial photographs and stream‐gage information. Bankfull channel width was used as the primary indicator variable to assess pre‐ and post‐dam channel change. Five sin‐mile river reaches and four stream gages were used in the analysis. Results indicated that, aside from some localized channel widening, the overall channel change has been minor with little post‐dam change in bankfull channel width. The lack of a pronounced post‐dam channel change may be attributed to a substantial reduction in the magnitude of the post‐dam annual peak discharges in combination with the resistance to erosion of the bed and bank materials. Also, the channel may have been overwidened by a series of large floods that predated construction of the dam, including one with an estimated 500‐year recurrence interval. 相似文献
120.
How energy costs affect foraging decisions is poorly understood for marine animals. To provide data relevant to this topic,
we examined the relationship between activity levels and foraging behavior by attaching activity recorders to 29 chick-rearing
wing-propelled diving birds (thick-billed murres, Uria lomvia) in 1999–2000. We connected the activity during the final dive bout with the prey item we observed being fed to the chicks.
After accounting for changes in activity level with depth, activity was highest during the final dive of a dive bout, reflecting
maneuvring during prey capture. Pelagic prey items, especially invertebrates (amphipods), were associated with higher depth-corrected
activity, leading to shorter dives for a given depth (presumably due to higher oxygen consumption rates) and, thus, shorter
search times (lower bottom time for a given depth). Pelagic prey items were likely captured during active pursuit, with the
birds actively seeking and pursuing schooling mid-water prey. In contrast, benthic prey involved low activity and extended
search times, suggesting that the birds slowly glided along the bottom in search for prey hidden in the sediments or rocks.
We concluded that activity levels are important in determining the foraging tactics of marine predators.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献