Nitrate Leaching from Moorland Soils: Can Soil C:N Ratios Indicate N Saturation?

Links between forest floor carbon:nitrogen (C:N) ratios, atmospheric N deposition and nitrate leaching into surface waters have been reported for forest ecosystems, but similar studies have not been reported previously for the equivalent compartments of moorland ecosystems in Great Britain, despite the importance of nitrate in contributing to the acidification of moorland streams and lakes in British uplands. In this paper, the relationships between the C:N ratio of moorland soil surface organic matter, N deposition, and nitrate leaching are explored for 13 soils in four moorland catchments. Although there is spatial variability in the C:N ratio of soils, major differences are apparent between soils and especially between catchments. The C:N ratio appears to be inversely related to modelled inorganic N deposition and, to a lesser degree, measured nitrate leaching, for three of the four catchments studied (Allt a'Mharcaidh, Afon Gwy, and Scoat Tarn). Nitrification may make an important contribution to nitrate leaching at the two higher deposition sites. At the fourth site, the heavily acidified River Etherow catchment, extremely high rates of nitrate leaching are not accompanied by low C:N ratios or high nitrification potentials in the upper soil horizons. Hence the C:N ratio of surface soil organic matter may have potential as an indicator of nitrogen saturation and leaching in some systems, but it is not universally applicable.     

A Conceptual Model of Spatially Heterogeneous Nitrogen Leaching from a Welsh Moorland Catchment

Soil- and stream-water data from the Plynlimon research area, mid-Wales, have been used to develop a conceptual model of spatial variations in nitrogen (N) leaching within moorland catchments. Extensive peats, in both hilltop and valley locations, are considered near-complete sinks for inorganic N, but leach the most dissolved organic nitrogen (DON). Peaty mineral soils on hillslopes also retain inorganic N within upper organic horizons, but a proportion percolates into mineral horizons as nitrate (NO ₃ ^– ), either through incomplete immobilisation in the organic layer, or in water bypassing the organic soil matrix via macropores. This NO ₃ ^– reaches the stream where mineral soilwaters discharge (via matrix throughflow or pipeflow) directly to the drainage network, or via small N-enriched flush wetlands. NO ₃ ^– in hillslope waters discharging into larger valley wetlands will be removed before reaching the stream. A concept of catchment nitrate leaching zones is proposed, whereby most stream NO ₃ ^– derives from localised areas of mineral soil hillslope draining directly to the stream; the extent of these zones within a catchment may thus determine its overall susceptibility to elevated surface water NO ₃ ^– concentrations.     

A spatially explicit investigation of phosphorus sorption and related soil properties in two riparian wetlands

Soils of riparian wetlands are highly effective at phosphorus (P) sorption. However, these soils exhibit extreme spatial variability across riparian zones. We used a spatially explicit sampling design in two riparian wetlands in North Carolina to better understand the relationships among P sorption, soil properties, and spatial variability. Our objectives were to quantify patterns of spatial variability of P sorption and related soil properties, and to determine which soil properties best explained the variability in P sorption after accounting for the effects of spatial autocorrelation. We measured bulk density, moisture, pH, soil organic matter (SOM), texture (percent clay, silt, and sand), oxalate-extractable aluminum (Al(ox)), iron (Fe(ox)), and the phosphorus sorption index (PSI). Due to differences in texture, Al(ox), and Fe(ox), the two sites had substantially different mean PSIs. At each site, we found considerable differences in the spatial variability of soil properties. For example, semivariance analysis and kriging illustrated that soil properties at Site 1 varied at smaller scales than those at Site 2. At both sites, after accounting for the effects of spatial autocorrelation and all other soil properties, we determined that Al(ox) had the highest Mantel correlation with PSI. We believe this geostatistic and Mantel approach is robust and could serve as a model for research on other biogeochemical processes such as denitrification.     

Initial investigation on the use of waterjets to place amendments in the subsurface

Quasi‐passive in situ remediation technologies, such as the use of permeable reactive barriers to treat contaminated groundwater or applications of granular activated carbon to treat polychlorinated biphenyl (PCB)‐contaminated, near‐surface sediments, are proven or promising technologies that may be limited in application due to the traditional construction techniques normally used for placement in the environment. High‐pressure waterjets have traditionally been used to excavate material during mining operations or to cut rock or other durable material. Waterjets have the potential to place amendments in the subsurface at depths greater than those that can be obtained using traditional construction techniques. Likewise, waterjets may have less negative impact on near‐surface utilities and/or sensitive ecological systems. Laboratory experiments were performed to characterize the placement of two solid amendments in a simulated saturated aquifer. A second set of experiments was performed to characterize the effectiveness of waterjets for placing a third amendment in simulated intertidal sediments. The laboratory work focused on characterizing the nature of the waterjet penetration of the aquifer matrix and the saturated sediments, as well as the corresponding waterjet parameters of pressure, nozzle size, and injection time. The laboratory results suggest that field trials may be appropriate for future investigations. © 2005 Wiley Periodicals, Inc.     

ACCOMMODATING CHANGE OF BACTERIAL INDICATORS IN LONG TERM WATER QUALITY DATASETS1

ABSTRACT: In 1996, the State of Oregon adopted a water quality standard based on Escherichia coli (E. coli), recognizing E. coli as an indicator of pathogenic potential. The Oregon Department of Environmental Quality (DEQ) began analysis for E. coli that same year. The Oregon DEQ continued collection and analysis of fecal coliform (a prior indicator organism) for data input to bacterial loading models and the Oregon Water Quality Index (OWQI). The OWQI is a primary indicator of general water quality for the Oregon DEQ and the Oregon Progress Board. The objective of this study was to develop a regression relationship between fecal coliform and E. coli. This relationship would fill data gaps and extend water quality models and indicators. Water quality policy is better informed by the ability of these extended water quality models to determine whether water quality meets present or would have met past bacterial standards. Monitoring resources spent on dual bacterial analyses could be conserved. This study also showed that changes to OWQI values (as a result of changing bacterial indicators) were minimal, and corresponded to improved characterization of water quality with respect to pathogenic potential.     

Masonry fireplace emissions test method: Repeatability and sensitivity to fueling protocol

A test method for masonry fireplaces has been evaluated during testing on six masonry fireplace configurations. The method determines carbon monoxide and particulate matter emission rates (g/h) and factors (g/kg) and does not require weighing of the appliance to determine the timing of fuel loading.The intralaboratory repeatability of the test method has been determined from multiple tests on the six fireplaces. For the tested fireplaces, the ratio of the highest to lowest measured PM rate averaged 1.17 and in no case was greater than 1.32. The data suggest that some of the variation is due to differences in fuel properties.The influence of fueling protocol on emissions has also been studied. A modified fueling protocol, tested in large and small fireplaces, reduced CO and PM emission factors by roughly 40% and reduced CO and PM rates from 0 to 30%. For both of these fireplaces, emission rates were less sensitive to fueling protocol than emission factors.     

Monitoring the presence of asbestos in a residential apartment building

Asbestos was once frequently used in building materials, but airborne fibres are now associated with serious health risks. This paper discusses the properties of asbestos and the ways in which certain forms can cause disease. Risks to the health of residents of asbestos-containing building are also explored. The detection, measurement and control of airborne asbestos demands careful monitoring. A case study is presented which describes the various procedures used to investigate the potential risks to residents of an asbestos-containing apartment building. Based on this investigation, recommendations are outlined for precautionary measures, mitigation techniques and further monitoring.     

Driving safety improves after individualized training: An RCT involving older drivers in an urban area

Objective: This study aimed to reproduce the results of a previous investigation on the safety benefits of individualized training for older drivers. We modified our method to address validity and generalizability issues.

Methods: Older drivers were randomly assigned to one of the 3 arms: (1) education alone, (2) education?+?on road training, and (3) education?+?on road?+?simulator training. Older drivers were recruited from a larger urban community. At the pre- and posttests (separated by 4 to 8 weeks) participants followed driving directions using a Global Positioning System (GPS) navigation system.

Results: Our findings support the positive influence of individualized on-road training for urban-dwelling older drivers. Overall, driving safety improved among drivers who received on-road training over those who were only exposed to an education session, F(1, 40) = 11.66, P = .001 (26% reduction in total unsafe driving actions [UDAs]). Statistically significant improvements were observed on observation UDAs (e.g., scanning at intersections, etc.), compliance UDAs (e.g., incomplete stop), and procedural UDAs (e.g., position in lane).

Conclusion: This study adds to the growing evidence base in support of individualized older driver training to optimize older drivers’ safety and promote continued safe driving.     

ALGAL BIOASSAY AND GROSS PRODUCTIVITY EXPERIMENTS USING SEWAGE EFFLUENT IN A MICHIGAN WETLAND'

ABSTRACT: One component of the filamentous algal community of a northern fen ecosystem in central Michigan was studied under conditions of nutrient enrichment by secondarily treated sewage effluent during one growing season. The productivity of Cladophora spp. measured by continuous flow bioassay was 2.6 g dry weight m day at the site of effluent addition compared to 0.085 g m day at the control site. Under conditions of nutrient enrichment, uptake by bioassay Cladophora spp. averaged 12 mg m^?2day^?1for phosphorus and 55 mg m^?2day^?1for nitrogen, compared to 0.01 mg m^?2 day^?1and 0.16 mg m^?2day^?1for phosphorus and nitrogen, respectively, in the control area. At the end of the growing season approximately 4.3 g N m^?2 and 0.96 g P m^?2were immobilized in Cladophora algal biomass. Algal growth temporarily immobilized 3.0 percent of the nitrogen and 1.0 percent of the phosphorus added as sewage effluent. Gross productivity of surface water in the fen averaged 1.5 g O₂m^?2day^?1at the nutrient enriched site, compared to 0.5 g O₂ m^?2day^?1at the control area. Gross productivity, community respiration and reaeration constant values in the fen were similar to data collected by other researchers in shallow water aquatic systems, but only at the fertilized sites.