A performance history of the base catalyzed decomposition (BCD) process

Remediation of halogenated organic compounds—such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs)—poses a challenge because these compounds are resistant to microbial attack and to degradation by many common chemicals. Since the mid-1980s, the Environmental Protection Agency's (EPA's) Office of Research and Development in Cincinnati, Ohio—the National Risk Management Research Laboratory (NRMRL)—has funded research and development efforts to develop specialized, chemical dehalogenation processes for detoxifying PCBs and related compounds. NRMRL owns domestic rights for “basic process” patents on a chemical dehalogenation process commonly known as Base Catalyzed Decomposition (BCD). EPA has licensed the process to two firms for use in the United States. This article summarizes laboratory-scale, pilot-scale, and field performance data on BCD technology collected to date by various governmental, academic, and private organizations.     

Dilution sampling and analysis of particulate matter in biomass-derived syngas

Thermochemical biomass gasification, followed by conversion of the produced syngas to fuels and electrical power, is a promising energy alternative. Real-world characterization of particulate matter (PM) and other contaminants in the syngas is important to minimize damage and ensure efficient operation of the engines it powers and the fuels created from it. A dilution sampling system is demonstrated to quantify PM in syngas generated from two gasification plants utilizing different biomass feedstocks: a BioMax?15 Biopower System that uses raw and torrefied woodchips as feedstocks, and an integrated biorefinery (IBR) that uses rice hulls and woodchips as feedstocks. PM_2.5 mass concentrations in syngas from the IBR downstream of the purification system were 12.8–13.7 μg·m⁻³, which were significantly lower than the maximum level for catalyst protection (500 μg·m⁻³) and were 2–3 orders of magnitude lower than those in BioMax?15 syngas (2247–4835 μg·m⁻³). Ultrafine particle number concentration and PM_2.5 chemical constituents were also much lower in the IBR syngas than in the BioMax?15. The dilution sampling system enabled reliable measurements over a wide range of concentrations: the use of high sensitivity instruments allowed measurement at very low concentrations (∼1 μg·m⁻³), while the flexibility of dilution minimized sampling problems that are commonly encountered due to high levels of tars in raw syngas (∼1 g·m⁻³).     

Potential Impacts of Stormwater Runoff on Water Quality in Urban Sand Pits and Adjacent Groundwater1

Whittemore, Donald O., 2012. Potential Impacts of Stormwater Runoff on Water Quality in Urban Sand Pits and Adjacent Groundwater. Journal of the American Water Resources Association (JAWRA) 48(3): 584-602. DOI: 10.1111/j.1752-1688.2011.00637.x Abstract: Entrance of stormwater runoff into water-filled pits and adjacent aquifers is a contamination concern. The water and sediment quality in several sand pits and surrounding groundwater in Wichita, Kansas, were studied to comprehensively address stormwater runoff impact. The pits are used for residential development after sand and gravel mining. Water samples were analyzed for inorganic constituents, bacteria, and 252 organic compounds, and pit sediments for inorganic components and 32 organic chemicals. Although many pesticide and degradate compounds were found in the pit and well waters, none of these chemicals exceeded existing health levels. Other organic contaminants were detected in the waters, with those exceeding health levels at one site attributed to an undiscovered groundwater contamination plume and not to stormwater runoff. Persistent insecticides and polychlorinated biphenyls detected in sediment of two pits are related to the age of residential development. The concentration distributions of pesticides and other organics at most of the sites, as well as iron, manganese, and ammonia patterns in downgradient well waters relative to upgradient well and pit waters, indicate that groundwater quality at the sites is affected by contaminants entering the pit surface waters. Thus, although current stormwater runoff does not appear to have contaminated sand-pit water and adjacent groundwater above health levels, the data show that the potential exists if stormwater became polluted.     

Groundwater Nitrate Concentration Reductions in a Riparian Buffer Enrolled in the NC Conservation Reserve Enhancement Program

Riparian buffers have been used for many years as a best management practice to decrease the effects of nonpoint pollution from watersheds. The NC Conservation Reserve Enhancement Program (NC CREP) has established buffers to treat groundwater nitrate‐nitrogen (NO₃^?‐N) from agricultural sources in multiple river basins. A maturing 46 m wide riparian buffer enrolled in NC CREP was studied to determine its effectiveness in reducing groundwater NO₃^?‐N concentrations from a cattle pasture fertilized with poultry litter. Three monitoring blocks that included groundwater quality wells, water table wells, and soil redox probes, were established in the buffer. NO₃^?‐N concentrations decreased significantly across the buffer in all of the monitoring blocks with mean reductions of 76‐92%. Many biological processes, including denitrification and plant uptake, may have been responsible for the observed NO₃^?‐N reductions but could not be differentiated in this study. However, mean reductions in Cl^? concentrations ranged from 48‐65% through the blocks, which indicated that dilution was an important factor in observed NO₃^?‐N reductions. These findings should be carefully considered for future buffer enrollments when assigning nitrogen removal credits.     

The Great Lakes Hydrography Dataset: Consistent,Binational Watersheds for the Laurentian Great Lakes Basin

Ecosystem‐based management of the Laurentian Great Lakes, which spans both the United States and Canada, is hampered by the lack of consistent binational watersheds for the entire Basin. Using comparable data sources and consistent methods, we developed spatially equivalent watershed boundaries for the binational extent of the Basin to create the Great Lakes Hydrography Dataset (GLHD). The GLHD consists of 5,589 watersheds for the entire Basin, covering a total area of approximately 547,967 km², or about twice the 247,003 km² surface water area of the Great Lakes. The GLHD improves upon existing watershed efforts by delineating watersheds for the entire Basin using consistent methods; enhancing the precision of watershed delineation using recently developed flow direction grids that have been hydrologically enforced and vetted by provincial and federal water resource agencies; and increasing the accuracy of watershed boundaries by enforcing embayments, delineating watersheds on islands, and delineating watersheds for all tributaries draining to connecting channels. In addition, the GLHD is packaged in a publically available geodatabase that includes synthetic stream networks, reach catchments, watershed boundaries, a broad set of attribute data for each tributary, and metadata documenting methodology. The GLHD provides a common set of watersheds and associated hydrography data for the Basin that will enhance binational efforts to protect and restore the Great Lakes.     

Handling of dioxin measurement data in the presence of non-detectable values: overview of available methods and their application in the Seveso chloracne study

Exposure measurements of concentrations that are non-detectable or near the detection limit (DL) are common in environmental research. Proper statistical treatment of non-detects is critical to avoid bias and unnecessary loss of information. In the present work, we present an overview of possible statistical strategies for handling non-detectable values, including deletion, simple substitution, distributional methods, and distribution-based imputation. Simple substitution methods (e.g., substituting 0, DL/2, DL/ radical2, or DL for the non-detects) are the most commonly applied, even though the EPA Guidance for Data Quality Assessment discouraged their use when the percentage of non-detects is >15%. Distribution-based multiple imputation methods, also known as robust or "fill-in" procedures, may produce dependable results even when 50-70% of the observations are non-detects and can be performed using commonly available statistical software. Any statistical analysis can be conducted on the imputed datasets. Results properly reflect the presence of non-detectable values and produce valid statistical inference. We describe the use of distribution-based multiple imputation in a recent investigation conducted on subjects from the Seveso population exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), in which 55.6% of plasma TCDD measurements were non-detects. We suggest that distribution-based multiple imputation be the preferred method to analyze environmental data when substantial proportions of observations are non-detects.     

Phosphorus and other soil components in a dairy effluent sprayfield within the central Florida Ridge

There is concern that P from dairy effluent sprayfields will leach into groundwater beneath Suwannee River basins in northern Florida. Our purpose was to describe the effects of dairy effluent irrigation on the movement of soil P and other nutrients within the upper soil profile of a sprayfield over three 12-mo cycles (April 1998-March 2001). Effluent P rates of 70, 110, and 165 kg ha(-1) cycle(-1) were applied to forages that were grown year-round. The soil is a deep, excessively drained sand (thermic, uncoated Typic Quartzipsamment). Mean P concentration in soil water below the rooting zone (152-cm depth) was < or = 0.1 mg L(-1) during 11 3-mo periods. Mehlich-1-extractable (M1) P, Al, and Ca in the topsoil increased over time but did not change in subsoil depths of 25 to 51, 51 to 71, 71 to 97, and 97 to 122 cm. Topsoil Ca increased as effluent rate increased. High Ca levels were found in dairy effluent (avg.: 305 mg L(-1)) and supplemental irrigation water (avg.: 145 mg L(-1)) which likely played a role in retaining P in the topsoil. An effect of effluent rate on P and Al concentrations in the topsoil was not detected, probably due to large and variable quantities present at project initiation. The P retention capacity (i.e., Al plus Fe) increased in the topsoil because Al increased. Dairy effluent contained Al (avg.: 31 mg L(-1)). Phosphorus saturation ratio (PSR) increased over time in the topsoil but not in subsoil layers. Regardless of effluent rate, the P retention capacity and PSR of subsoil, which contained 119 to 229 mg kg(-1) of Al, should be taken into account when assessing the risk of P moving below the rooting zone of most forage crops.     

The regional nature of PM2.5 episodes in the upper Ohio River Valley

From October 1999 through September 2000, particulate matter (PM) with aerodynamic diameter > or =2.5 microm (PM2.5) mass and composition were measured at the National Energy Technology Laboratory Pittsburgh site, with a particle concentrator Brigham Young University-organic sampling system and a tapered element oscillating microbalance (TEOM) monitor. PM2.5 measurements had also been obtained with TEOM monitors located in the Pittsburgh, PA, area, and at sites in Ohio, including Steubenville, Columbus, and Athens. The PM data from all these sites were analyzed on high PM days; PM2.5 TEOM particulate mass at all sites was generally associated with transitions from locally high barometric pressure to lower pressure. Elevated concentrations occurred with transport of PM from outside the local region in advance of frontal passages as the local pressure decreased. During high-pressure periods, concentrations at the study sites were generally low throughout the study region. Further details related to this transport were obtained from surface weather maps and estimated back-trajectories using the hybrid single-particle Lagrangian integrated trajectory model associated with these time periods. These analyses indicated that transport of pollutants to the Pittsburgh site was generally from the west to the southwest. These results suggest that the Ohio River Valley and possible regions beyond act as a significant source of PM and its precursors in the Pittsburgh area and at the other regional sites included in this study.     

Science and management in four U.S. coastal ecosystems dominated by land-ocean interactions

The influence of science in the recognition of the effects of landscape changes on coastal ecosystems and in the development of effective policy for managing and restoring these ecosystems is examined through four case studies: Chesapeake Bay, San Francisco Bay, the Mississippi Delta, and Florida Bay. These ecosystems have undergone major alterations as a result of changes in the delivery of water, sediments and nutrients from their watersheds. Both science and management have been challenged by the spatial, functional and temporal scale mismatches inherent in the watershed-coastal ecosystem relationship. Key factors affecting the influence of science on management include (1) sustained scientific investigation, responsive to but not totally defined by managers; (2) clear evidence of change, the scale of the change and the causes of the change; (3) consensus among the scientific communities associated with various interests; (4) the development of models to guide management actions; (5) identification of effective and feasible solutions to the problems.