Validation of the Digital Opacity Compliance System under Regulatory Enforcement Conditions

Abstract

U.S. Environmental Protection Agency (EPA) Emission Measurement Center in conjunction with EPA Regions VI and VIII, the state of Utah, and the U.S. Department of Defense have conducted a series of long-term pilot and field tests to determine the accuracy and reliability of a visible opacity monitoring system consisting of a conventional digital camera and a separate computer software application for plume opacity determination. This technology, known as the Digital Opacity Compliance System (DOCS), has been successfully demonstrated at EPA-sponsored Method-9 “smoke schools,” as well as at a number of government and commercially operated industrial facilities.

Results from the current DOCS regulatory pilot study demonstrated that, under regulatory enforcement conditions, the average difference in opacity measurement between the DOCS technology and EPA Reference Method 9 (Method 9) was 1.12%. This opacity difference, which was computed from the evaluation of 241 regulated air sources, was found to be statistically significant at the 99% confidence level. In evaluating only those sources for which a nonzero visible opacity level was recorded, the average difference in opacity measurement between the DOCS technology and Method 9 was 1.20%. These results suggest that the two opacity measurement methods are essentially equivalent when measuring the opacity of visible emissions.

Given the costs and technical limitations associated with use of Method 9, there is a recognized need to develop accurate, reproducible, and scientifically defensible alternatives to the use of human observers. The use of digital imaging/processing brings current technology to bear on this important regulatory issue. Digital technology offers increased accuracy, a permanent record of measurement events, lower costs, and a scientifically defensible approach for opacity determination.     

In Situ Determination of the Rate of Unassisted Degradation of Saturated-Zone Hydrocarbon Contamination

Abstract

A method to measure the in situ degradation rate of dissolved hydrocarbon contamination has been developed and applied at two locations at a field site. The method uses the rates of downward diffusion of oxygen and upward diffusion of carbon dioxide through the unsaturated zone, as calculated from vertical soil-gas concentration gradients, combined with stoichiometry to obtain two degradation rates in hydrocarbon mass per water table surface area per time. Values of 0.385 gram per m² per day and 0.52 gram per m² per day (based upon oxygen data) and 0.056 gram per m² per day and 0.12 gram per m² per day (based upon carbon dioxide data) were calculated at a field site with dissolved fuel contamination. This result of lower values from ground-air carbon dioxide concentrations is consistent with a significant fraction of the carbon dioxide produced being lost to the aqueous phase. Based upon a single-stage equilibrium phase-transfer model, gas/water volume ratios of 0.02 and 0.2 for the capillary fringe were calculated. Groundwater carbon dioxide fugacities and soil-gas carbon dioxide concentrations were used at the two locations and a third to determine whether the source of elevated soil carbon dioxide concentrations were unsaturated-zone hydrocarbon degradation or a saturated-zone process. This technique has potential applicability in setting risk-based remedial criteria and in allowing inclusion of the contribution of in situ degradation in remedial design. This can result in major remedial cost savings.     

An energy systems view of sustainability: emergy evaluation of the San Luis Basin, Colorado

Energy Systems Theory (EST) provides a framework for understanding and interpreting sustainability. EST implies that "what is sustainable" for a system at any given level of organization is determined by the cycles of change originating in the next larger system and within the system of concern. The pulsing paradigm explains the ubiquitous cycles of change that apparently govern ecosystems, rather than succession to a steady state that is then sustainable. Therefore, to make robust decisions among environmental policies and alternatives, decision-makers need to know where their system resides in the cycles of change that govern it. This theory was examined by performing an emergy evaluation of the sustainability of a regional system, the San Luis Basin (SLB), CO. By 1980, the SLB contained a climax stage agricultural system with well-developed crop and livestock production along with food and animal waste processing. The SLB is also a hinterland in that it exports raw materials and primary products (exploitation stage) to more developed areas. Emergy indices calculated for the SLB from 1995 to 2005 revealed changes in the relative sustainability of the system over this time. The sustainability of the region as indicated by the renewable emergy used as a percent of total use declined 4%, whereas, the renewable carrying capacity declined 6% over this time. The Emergy Sustainability Index (ESI) showed the largest decline (27%) in the sustainability of the region. The total emergy used by the SLB, a measure of system well-being, was fairly stable (CV?=?0.05). In 1997, using renewable emergy alone, the SLB could support 50.7% of its population at the current standard of living, while under similar conditions the U.S. could support only 4.8% of its population. In contrast to other indices of sustainability, a new index, the Emergy Sustainable Use Index (ESUI), which considers the benefits gained by the larger system compared to the potential for local environmental damage, increased 34% over the period.     

Simulating Land-Cover Change in Montane Mainland Southeast Asia

We used the conversion of land use and its effects (CLUE-s) model to simulate scenarios of land-cover change in Montane mainland southeast Asia (MMSEA), a region in the midst of transformation due to rapid intensification of agriculture and expansion of regional trade markets. Simulated changes affected approximately 10 % of the MMSEA landscape between 2001 and 2025 and 16 % between 2001 and 2050. Roughly 9 % of the current vegetation, which consists of native species of trees, shrubs, and grasses, is projected to be replaced by tree plantations, tea, and other evergreen shrubs during the 50 years period. Importantly, 4 % of this transition is expected to be due to the expansion of rubber (Hevea brasiliensis), a tree plantation crop that may have important implications for local-to-regional scale hydrology because of its potentially high water consumption in the dry season.     

Managing United States Public Lands in Response to Climate Change: A View From the Ground Up

Federal land managers are faced with the task of balancing multiple uses and goals when making decisions about land use and the activities that occur on public lands. Though climate change is now well recognized by federal agencies and their local land and resource managers, it is not yet clear how issues related to climate change will be incorporated into on-the-ground decision making within the framework of multiple use objectives. We conducted a case study of a federal land management agency field office, the San Juan Public Lands Center in Durango, CO, U.S.A., to understand from their perspective how decisions are currently made, and how climate change and carbon management are being factored into decision making. We evaluated three major management sectors in which climate change or carbon management may intersect other use goals: forests, biofuels, and grazing. While land managers are aware of climate change and eager to understand more about how it might affect land resources, the incorporation of climate change considerations into everyday decision making is currently quite limited. Climate change is therefore on the radar screen, but remains a lower priority than other issues. To assist the office in making decisions that are based on sound scientific information, further research is needed into how management activities influence carbon storage and resilience of the landscape under climate change.     

An Ecoregional Context for Forest Management on National Wildlife Refuges of the Upper Midwest,USA

To facilitate forest planning and management on National Wildlife Refuges, we synthesized multiple data sources to describe land ownership patterns, land cover, landscape pattern, and changes in forest composition for four ecoregions and their associated refuges of the Upper Midwest. We related observed patterns to ecological processes important for forest conservation and restoration, with specific attention to refuge patterns of importance for forest landbirds of conservation priority. The large amount of public land within the ecoregions (31–80%) suggests that opportunities exist for coarse and meso-scale approaches to conserving and restoring ecological processes affecting the refuges, particularly historical fire regimes. Forests dominate both ecoregions and refuges, but refuge forest patches are generally larger and more aggregated than in associated ecoregions. Broadleaf taxa have increased in dominance in the ecoregions and displaced fire-dependent taxa such as pine (Pinus spp.) and other coniferous species; these changes in forest composition have likely also affected refuge forests. Despite compositional changes, larger forest patches on refuges suggests that they may provide better habitat for area-sensitive forest landbirds of mature, compositionally diverse forests than surrounding lands if management continues to promote increased patch size. We reason that although fine-scale research and monitoring for species of conservation priority is important, broad scale (ecoregional) assessments provide crucial context for effective forest and wildlife management in protected areas.     

Emerging technologies for removing nonpoint phosphorus from surface water and groundwater: introduction

Coastal and freshwater eutrophication continues to accelerate at sites around the world despite intense efforts to control agricultural P loss using traditional conservation and nutrient management strategies. To achieve required reductions in nonpoint P over the next decade, new tools will be needed to address P transfers from soils and applied P sources. Innovative remediation practices are being developed to remove nonpoint P sources from surface water and groundwater using P sorbing materials (PSMs) derived from natural, synthetic, and industrial sources. A wide array of technologies has been conceived, ranging from amendments that immobilize P in soils and manures to filters that remove P from agricultural drainage waters. This collection of papers summarizes theoretical modeling, laboratory, field, and economic assessments of P removal technologies. Modeling and laboratory studies demonstrate the importance of evaluating P removal technologies under controlled conditions before field deployment, and field studies highlight several challenges to P removal that may be unanticipated in the laboratory, including limited P retention by filters during storms, as well as clogging of filters due to sedimentation. Despite the potential of P removal technologies to improve water quality, gaps in our knowledge remain, and additional studies are needed to characterize the long-term performance of these technologies, as well as to more fully understand their costs and benefits in the context of whole-farm- and watershed-scale P management.     

Using flue gas desulfurization gypsum to remove dissolved phosphorus from agricultural drainage waters

High levels of accumulated phosphorus (P) in soils of the Delmarva Peninsula are a major source of dissolved P entering drainage ditches that empty into the Chesapeake Bay. The objective of this study was to design, construct, and monitor a within-ditch filter to remove dissolved P, thereby protecting receiving waters against P losses from upstream areas. In April 2007, 110 Mg of flue gas desulfurization (FGD) gypsum, a low-cost coal combustion product, was used as the reactive ingredient in a ditch filter. The ditch filter was monitored from 2007 to 2010, during which time 29 storm-induced flow events were characterized. For storm-induced flow, the event mean concentration efficiency for total dissolved P (TDP) removal for water passing through the gypsum bed was 73 ± 27% confidence interval (α = 0.05). The removal efficiency for storm-induced flow by the summation of load method was 65 ± 27% confidence interval (α = 0.05). Although chemically effective, the maximum observed hydraulic conductivity of FGD gypsum was 4 L s(-1), but it decreased over time to <1 L s(-1). When bypass flow and base flow were taken into consideration, the ditch filter removed approximately 22% of the TDP load over the 3.6-yr monitoring period. Due to maintenance and clean-out requirements, we conclude that ditch filtration using FGD gypsum is not practical at a farm scale. However, we propose an alternate design consisting of FGD gypsum-filled trenches parallel to the ditch to intercept and treat groundwater before it enters the ditch.     

Inputs and losses by surface runoff and subsurface leaching for pastures managed by continuous or rotational stocking

Pasture management practices can affect forage quality and production, animal health and production, and surface and groundwater quality. In a 5-yr study conducted at the North Appalachian Experimental Watershed near Coshocton, Ohio, we compared the effects of two contrasting grazing methods on surface and subsurface water quantity and quality. Four pastures, each including a small, instrumented watershed (0.51-1.09 ha) for surface runoff measurements and a developed spring for subsurface flow collection, received 112 kg N ha(-1) yr(-1) and were grazed at similar stocking rates (1.8-1.9 cows ha(-1)). Two pastures were continuously stocked; two were subdivided so that they were grazed with frequent rotational stocking (5-6 times weekly). In the preceding 5 yr, these pastures received 112 kg N ha(-1) yr(-1) after several years of 0 N fertilizer and were grazed with weekly rotational stocking. Surface runoff losses of N were minimal. During these two periods, some years had precipitation up to 50% greater than the long-term average, which increased subsurface flow and NO(3)-N transport. Average annual NO(3)-N transported in subsurface flow from the four watersheds during the two 5-yr periods ranged from 11.3 to 22.7 kg N ha(-1), which was similar to or less than the mineral-N received in precipitation. Flow and transport variations were greater among seasons than among watersheds. Flow-weighted seasonal NO(3)-N concentrations in subsurface flow did not exceed 7 mg L(-1). Variations in NO(3)-N leached from pastures were primarily due to variable precipitation rather than the effects of continuous, weekly rotational, or frequent rotational stocking practices. This suggests that there was no difference among these grazing practices in terms of NO(3)-N leaching.