Spatial and temporal variability

In fluid reservoirs like fhe afmosphere or the ocean, the turnover time of a tracer is also related to the spatial and temporal variability of ifs concentration within the reservoir a long turnover time corresponds to a small variability and vice versa (Junge, 1974 Hamrud, 1983). Figure 4-2 shows a plot of measured trace gas variability in the atmosphere versus turnover time estimated by applying budget considerations as indicated by Equation (1). An inverse relation is obvious, but the scatter in the data... 

Peltzer, E. T. and Hayward, N. A. (1996). Spatial and temporal variability of total organic carbon along 140 W in the equatorial Pacific Ocean in 1992. Deep-Sea Res. II43, 1155-1180. 

For convenience, these qualitative and quantitative absorption models have been classified into three categories based on their dependence on spatial and temporal variables [2], The first category is referred to as quasi-equilibrium models. The quasi-equilibrium model, including the pH-partition hypothesis... 

Figure 1 Overview of transport models for predicting oral drug absorption. Absorption models are classified into three categories based on their dependence on the spatial and temporal variables. These three categories are quasi-equilibrium, steady-state, and dynamic models. 

Sass RL, Andrews JA, Ding A, Fisher FM. Spatial and temporal variability in methane emissions from rice paddies Implications for assessing regional methane budgets. Nutr. Cycl. Agroecosys. 2002 64 3-7. 

Additionally, the integration of geographic information system (GIS) with analytical data is an effective procedure in addressing the problem of spatial and temporal variability of the different parameters involved in the environmental fate of chemicals. Based on accurate local estimations, GIS-based models would then also allow deriving realistic and representative spatially averaged regional PECs. Table 4 shows some studies that have used GIS-based methodologies to perform a site-specific risk assessment of PECs in different exposed ecosystems. 

Table 1 gives the values of design and operating parameters of a scale model fluidized with air at ambient conditions which simulates the dynamics of an atmospheric fluidized bed combustor operating at 850°C. Fortunately, the linear dimensions of the model are much smaller, roughly one quarter those of the combustor. The particle density in the model must be much higher than the particle density in the combustor to maintain a constant value of the gas-to-solid density ratio. Note that the superficial velocity of the model differs from that of the combustor along with the spatial and temporal variables. 

Sanders, J.G., G.F. Riedel, and G.R. Abbe. 1991. Factors controlling the spatial and temporal variability of trace metal concentrations in Crassostrea virginica (Gmelin). Pages 335-339 in M. Elliott and J.P. Ducrotoy (eds.). Estuaries and Coasts Spatial and Temporal Comparisons. ECSA Sympos. 19 (Univ. Caen, France, 1989). Olsen Olsen, Fredensborg, Denmark. 

Enzyme activity (urease, amidase, dehydrogenase, pl-glucosidase, phosphatase, arylsulfatase, fluorescein diacetate hydrolysis) Laboratory incubation Indicates potential microbial activity and nutrient cycling reactions determined in nonstandard laboratory with specialized equipment highly spatially and temporally variable dependent upon organic inputs Dick et al. (1996) Parham et aL (2002)... 

Denitrification, a dissimilatory pathway of nitrate reduction (see Section 3.3 also) into nitrogen oxides, N2O, and dinitrogen, N2, is performed by a wide variety of microorganisms in the forest ecosystems. Measurable rates of N20 production have been observed in many forest soils. The values from 2.1 to 4.0 kg/ha/yr are typical for forest soils in various places of Boreal and Sub-Boreal Forest ecosystems. All in situ studies (field monitoring) of denitrification in forest soils have shown large spatial and temporal variability in response to varying soils characteristics such as acidity, temperature, moisture, oxygen, ambient nitrate and available carbon. 

HPLC has been further employed for the mesurement of the spatial and temporal variabilities of phytoplankton community structure [287], for the investigation of the seasonal change of algal pigments [288], for the study of the seasonal and interannual change of phytoplankton communities [289] and for the assessment of the tidal and diurnal periodicities of pigment profiles [290],... 

Y. Obayashi, E. Tanoue, K. Suzuki, N. Handa, Y. Nojiri and C.S. Wong, Spatial and temporal variabilities of phytoplankton community structure in the Northern North Pacific as determined by phytoplankton pigments. Deep Sea Res. Part I Oceanogr. Res. Papers 48 (2001) 439 169. 

River transport of clay minerals into the ocean is spatially and temporally variable. The global annual suspended load of river sediment into coastal waters currently averages 12.6 X 10 ton. This flux is approximately 10% less than was delivered before humans began damming rivers. (One notable exception is the Mississippi River, whose sediment load has increased due to very high rates of soil erosion. The riverine sediments deposited in the mouth of the Mississippi River form one of the world s largest deltas.)... 

Spatial and Temporal Variability of Airborne Psychoactive Substances in Cities.. 450... 

The atmospheric and chemical processes controlling the spatial and temporal variability of psychoactive substances in urban atmospheres are largely uncertain, mostly due to the fact that the atmospheric residence time of these compounds is so far unclear. The transport, transformation and deposition/atmospheric removal... 

Many factors affect the transport of contaminants in the subsurface, including the (spatially and temporally variable) hydraulic and physicochemical characteristics of the solid phase and the properties of water and the contaminants themselves. In this chapter, we focus on several specific, representative examples of reactive (nonconservative) contaminant transport. 

Some data are available from several fields and held edges to estimate spatial and temporal variability around 30-day mean concentrations. In this case study, the concentration variables for the held are treated as random variables with uncertainty. Because the concentration variables for the edge are minor contributors to total daily intake, the uncertainty about these variables is ignored. 

The purpose of this chapter is not to promote the replacement of traditional physically based methods of assessing groundwater-lake systems with isotopic methods, but rather to demonstrate the utility of isotopic techniques. Physically based methods can provide more detailed information on the spatial and temporal variability of a groundwater-lake system than isotopic approaches can provide. Regardless of the method chosen, however, an adequate number of piezometers is necessary to ensure that groundwater samples are collected from upgradient areas. 

The values in parentheses give the approximate typical variability range, including the spatial and temporal variability... 

Arai, Y., Lanzirotti, A., Sutton, S.R. et al. (2006) Spatial and temporal variability of arsenic solid-state speciation in historically lead arsenate contaminated soils. Environmental Science and Technology, 40(3), 673-79. 

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