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Influence of Subsurface Processes
Published in Larry W. Canter, in Groundwater, 2019
Finally, Lindstrom and Boersma (1990) described a two-dimensional mathematical model for simulating the transport and fate of organic chemicals in a laboratory-scale, single-layer aquifer. Two large (4 ft wide, 4 ft high, and 16 ft long) physical aquifers were used, with each aquifer containing three horizontal layers of material. Each layer was assumed to be homogenous and isotropic with respect to water flow. The systems were used for the study of transport and fate of chemicals, and for evaluation of growth characteristics of indigenous microbial populations. The physical aquifers can also be used for the study of proposed physical and biological remediation schemes. The developed mathematical model accounts for the major physical processes of storage, dispersion, and advection, and can also account for linear equilibrium sorption, three first-order loss processes (including microbial degradation, irreversible sorption and/or dissolution into the organic phase, metabolism in the sorbed state), and first-order loss in the sorbed state. A broad range of remediation scenarios may be considered by the use of the model, including placement of injection/extraction wells to induce plume spreading or plume shaping and the effects of regions of varying hydraulic conductivity on the shape of the plumes.
Ground water monitoring and site remediation
Published in Neal Wilson, Soil Water and Ground Water Sampling, 2020
Once a contamination problem has been identified a plan needs to be formulated and implemented to assess the immediate risks to human health and the environment, quantify the constituents of concern, determine the horizontal and vertical rates of migration of the contaminant plume, develop ways to reduce or eliminate the contamination, and further identify and protect those potentially affected. A statement of what problem is to be solved, the information required, what the project objectives are and how the objectives are to be met must be concisely stated and sufficiently detailed to permit a clear understanding by all the parties involved in the data collection effort.10
Free Convection
Published in Gautam Biswas, Amaresh Dalal, Vijay K. Dhir, Fundamentals of Convective Heat Transfer, 2019
Gautam Biswas, Amaresh Dalal, Vijay K. Dhir
A plume is the buoyancy induced flow resulting in a fluid, when energy is supplied continuously at just one location in the fluid. In practice free plumes, like free jets are generally turbulent. An axisymmetric plume is found to be laminar only if the Rayleigh number based on its heat source(q″) and height of the plume(H) is less than 1010. Rayleigh number is given by RaH=gβH4q″ανk
Wildfire and prescribed burning impacts on air quality in the United States
Published in Journal of the Air & Waste Management Association, 2020
Daniel A. Jaffe, Susan M. O’Neill, Narasimhan K. Larkin, Amara L. Holder, David L. Peterson, Jessica E. Halofsky, Ana G. Rappold
As smoke plumes move over populated areas, they can elevate PM2.5 and/or O3 levels over health standards. Large and extended wildfires can be associated with respiratory issues and premature mortality (e.g., Liu et al. 2015a; Reid et al. 2019). The plumes can affect regions directly and/or mix with other urban pollutants. In the U.S., the Clean Air Act of 1963 was enacted to protect public health and welfare. In 1970 the U.S. Environmental Protection Agency (EPA) established the National Ambient Air Quality Standards (NAAQS) for six criteria pollutants. The criteria pollutants most relevant to wildland fire emissions are PM2.5, O3, and CO. For daily average PM2.5, the current primary standard is 35 µg/m3 at the 98th percentile, averaged over three years. For O3, the current primary standard is 0.070 ppm for the annual fourth-highest daily maximum 8-hour concentration (MDA8), averaged over three years. For CO, the current primary standards are 9 ppm for an 8-hour averaging time, and 35 ppm for a one-hour averaging time, not to be exceeded more than once per year. Although CO from fires is rarely a concern to the public, it can affect wildland firefighters, and recent work analyzes exposure in terms of National Institute of Occupational Safety and Health (NIOSH) standards (Henn et al. 2019). Smoke plumes from wildland fires have caused substantial exceedances of the EPA standards for both PM2.5 and O3, but a state may try to exclude these data from regulatory consideration under the exceptional events rule (See Section 8, Regulatory context for air quality management, for further discussion).