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171.
Annual export rates, or fluxes, of total nitrogen (TN), nitrate, total phosphorus (TP) and potassium from four streams on two golf courses on the Precambrian Shield were compared with those from forested reference locations. Overall, the mean annual fluxes of K, TN, NO(3) and TP from golf courses were greater than from forested areas by 10, 2, 6 and 2 times, respectively. The overall mean export coefficients (kg/ha/yr) were 16 for K, 5.2 for TN, 2.1 for NO(3) and 0.14 for TP. For TN and TP, these are similar to those reported from cropland in Canada by Chambers and Dale. 相似文献
172.
Wade KS Mulholland JA Marmur A Russell AG Hartsell B Edgerton E Klein M Waller L Peel JL Tolbert PE 《Journal of the Air & Waste Management Association (1995)》2006,56(6):876-888
Data from the U.S. Environmental Protection Agency Air Quality System, the Southeastern Aerosol Research and Characterization database, and the Assessment of Spatial Aerosol Composition in Atlanta database for 1999 through 2002 have been used to characterize error associated with instrument precision and spatial variability on the assessment of the temporal variation of ambient air pollution in Atlanta, GA. These data are being used in time series epidemiologic studies in which associations of acute respiratory and cardiovascular health outcomes and daily ambient air pollutant levels are assessed. Modified semivariograms are used to quantify the effects of instrument precision and spatial variability on the assessment of daily metrics of ambient gaseous pollutants (SO2, CO, NOx, and O3) and fine particulate matter ([PM2.5] PM2.5 mass, sulfate, nitrate, ammonium, elemental carbon [EC], and organic carbon [OC]). Variation because of instrument imprecision represented 7-40% of the temporal variation in the daily pollutant measures and was largest for the PM2.5 EC and OC. Spatial variability was greatest for primary pollutants (SO2, CO, NOx, and EC). Population-weighted variation in daily ambient air pollutant levels because of both instrument imprecision and spatial variability ranged from 20% of the temporal variation for O3 to 70% of the temporal variation for SO2 and EC. Wind 相似文献
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176.
Mary Ann Rozance Diana Denham Sarah Kidd 《Journal of Environmental Policy & Planning》2020,22(3):413-427
ABSTRACTThe success of ecological restoration efforts is tightly coupled with the effectiveness of many U.S. environmental policies. Yet scholars have raised questions about the ability of restoration to produce intended results. We use a case study of tidal wetland restoration planning in Oregon to examine how neoliberal environmental governance exercises influence through a set of knowledge politics that produces subpar outcomes. We present three main findings: (1) restoration policies produce a restoration economy based on a conception of wetland as commodity (2) practitioners in this restoration economy exhibit competitive behavior resulting in a piecemeal rather than a landscape approach to restoration; and (3) limited monitoring prevents changes to existing policies. Practitioners offer insight into the challenge of treating wetlands as a commodity and call for more monitoring to challenge the assumptions of hegemonic knowledge practices that reinforce a neoliberal environmental governance regime. The divergent ideas of reflexive practitioners, though not yet manifest as action, show where changes to restoration governance might be possible. 相似文献
177.
In 1991, a fire occurred at a foundry in western Pennsylvania. The fire started in capacitors that contained polychlorinated biphenyls (PCBs) and subsequent sampling has indicated that PCBs and products of their incomplete combustion, the polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), were released as a result of the fire. This article develops and provides justification for site-specific cleanup levels for the PCBs, PCDDs, and PCDFs accidentally released into this industrial facility during the fire. Cleanup levels were calculated using standard risk assessment approaches and assumptions, and these riskbased values were compared with cleanup criteria used for other sites. Final criteria were established based on this comparison and a consideration of such site-specific factors as migration potential, industrial use patterns, and the small mass of material present. 相似文献
178.
Mercury in fish from African lakes 总被引:1,自引:0,他引:1
Karen Kidd 《Natural resources forum》2005,29(2):177-178
179.
Cascading ecological effects of low-level phosphorus enrichment in the Florida everglades 总被引:2,自引:0,他引:2
Gaiser EE Trexler JC Richards JH Childers DL Lee D Edwards AL Scinto LJ Jayachandran K Noe GB Jones RD 《Journal of environmental quality》2005,34(2):717-723
Few studies have examined long-term ecological effects of sustained low-level nutrient enhancement on wetland biota. To determine sustained effects of phosphorus (P) addition on Everglades marshes we added P at low levels (5, 15, and 30 microg L(-1) above ambient) for 5 yr to triplicate 100-m flow-through channels in pristine marsh. A cascade of ecological responses occurred in similar sequence among treatments. Although the rate of change increased with dosing level, treatments converged to similar enriched endpoints, characterized most notably by a doubling of plant biomass and elimination of native, calcareous periphyton mats. The full sequence of biological changes occurred without an increase in water total P concentration, which remained near ambient levels until Year 5. This study indicates that Everglades marshes have a near-zero assimilative capacity for P without a state change, that ecosystem responses to enrichment accumulate over time, and that downstream P transport mainly occurs through biota rather than the water column. 相似文献
180.
Kuntz RL Hartel PG Godfrey DG McDonald JL Gates KW Segars WI 《Journal of environmental quality》2003,32(6):2311-2318
Recent studies suggest that host origin databases for bacterial source tracking (BST) must contain a large number of isolates because bacterial subspecies change with geography and time. A new targeted sampling protocol was developed as a prelude to BST to minimize these changes. The research was conducted on the Sapelo River, a tidal river on the Georgia coast. A general sampling of the river showed fecal enterococcal numbers ranging from <10 (below the limit of detection) to 990 colony-forming units (CFU) per 100 mL. Locations with high enterococcal numbers were combined with local knowledge to determine targeted sampling sites. Fecal enterococcal numbers around one site ranged from <10 to 24,000 CFU per 100 mL. Bacterial source tracking was conducted to determine if a wastewater treatment facility at the site was responsible for this contamination. The fecal indicator bacterium was Enterococcus faecalis. Ribotyping, automated with a RiboPrinter (DuPont Qualicon, Wilmington, DE), was the BST method. Thirty-seven ribotypes were observed among 83 Ent. faecalis isolates obtained from the Sapelo River and the wastewater lagoon. Sixteen ribotypes were associated with either the river or the lagoon, and only five ribotypes (14%) were shared. Nevertheless, these five ribotypes represented 39 of the 83 Ent. faecalis isolates, almost a majority (47%). These results suggest that the fecal contamination in the river came from the wastewater treatment facility. As a prelude to BST, targeted sampling minimized subspecies changes with geography and time, and eliminated the need for a permanent host origin database by restricting BST to a small geographic area and requiring sampling to be completed in one day. 相似文献