Spatial and Temporal Variation

FIGURE 82A PM25 concentration and chemical composition at various sites in North America (NARSTO 2003). Chemical species for each site are presented clockwise in the pie charts in the same order as in the legend. 

FIGURE 8.25 Annual variation of the Ph. s concentration and composition in Pittsburgh, PA (Wittig et al. 2004a). 

FIGURE 8.28 Measured PM10 OC and EC concentrations in Bakersfield, CA during 1995 Integrated Monitoring Study. 

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The thermal parameters for comfort should be relatively uniform both spatially and temporally. Variations in heat flow from the body make the physiological temperature regulation more difficult. Nonuniform thermal conditions can lead to nonuniform skin temperatures. The active elements of the regulatory system may need to make more adjustments and work harder in order to keep thermal skin and body temperatures stable. To avoid discomfort from environmental nonuniformities, the temperature difference between feet and head should be less than about 3 °C (Fig. 5.9) and the mean surface temperature or radiant difference from one side of the body to the other should not he greater then about 10 °C. 

Hansell, D. A. and Peltzer, E. T. (1998). Spatial and temporal variations of total organic carbon in the Arabian Sea. Deep-Sea Res. II (in press). 

Van Nuijs ALN, Pecceu B, Theunis L, Dubois N, Oiarlier C, Jorens PG, Bervoets L, Blust R, Neels H, Covaci A (2009) Spatial and temporal variations in the occurrence of cocaine and benzoylecgonine in waste- and surface water from Belgium and removal during wastewater treatment. Water Res 43(5) 1341-1349... 

Bartholomew GW, FK Pfaender (1983) Influence of spatial and temporal variations on organic pollutant biodegradation rates in an estuarine environment. Appl Environ Microbiol 45 103-109. 

Sextro, R.G., Nazaroff, W.W., and Turk, B.H., Spatial and temporal variation in factors governing the radon source potential of soil, in Proceedings of the 1988 Symposium on Radon and Radon Reduction Technology, Vol. 1, EPA- 600/9-89-006a (NTIS PB89-167480), March 1989. 

Phillips, B.M., B.S. Anderson, and J.W. Hunt. 1998. Spatial and temporal variation in results of purple urchin (Strongylocentrotus purpuratus) toxicity tests with zinc. Environ. Toxicol. Chem. 17 453-459. 

TV glaciers are the primary source of water to life-supporting streams and lakes. Understanding the spatial and temporal variation in glacier snow geochemistry... 

Blowes, D.W., Ptacek, C.J., Jambor, J.L 2003. Mill Tailings Hydrology and Geochemistry. Environmental aspects of Mine Waste. Mineralogical Association of Canada Short Course series 31, 95-116. Etcheverry, D.J. 2009. Spatial and Temporal Variations in the Ruttan Mine Tailings, Leaf Rapids, Manitoba, Canada. M.Sc. thesis, University of Manitoba, Winnipeg, Manitoba. 

A two-point two-time PDF would be required to describe such spatial and temporal variations. 

Winds play a central role in inducing ocean currents and turbulent mixing. Winds themselves are a type of convection current generated by spatial and temporal variations in atmospheric heating. In the atmosphere, these air currents form the major wind... 

At sea level, Pj is approximately 1 atm, but exhibits some temporal and spatial variability. For example, the annual mean pressure in the northern hemisphere is 0.969 atm and in the southern hemisphere is 0.974 atm, with monthly averages varying by as much as 0.0001 atm, i.e., about 1 mbar (1 atm = 1013.25 mbar). These fluctuations are caused by spatial and temporal variations in atmospheric temperature and water vapor content associated with weather, and seasonal and longer-term climate shifts. Pj is also affected by diurnal atmospheric tides, and it decreases with increasing altitude above sea level. Some gases, such CO2 and O2, exhibit seasonal variability that is caused in part by seasonal variability in plant and animal activity (see Figures 25.4 and 6.7). 

Atmospheric methane has a mean 5 C-value of around —47%c (Stevens 1988). Quay et al. (1999) presented global time series records between 1988 and 1995 on the carbon and hydrogen isotope composition of atmospheric methane. They measured spatial and temporal variation in and D with a slight emichment observed for the southern hemisphere (—47.2%c) relative to the northern hemisphere (—47.4%o). The mean 5D was —86 3%c with a 10%o depletion in the northern relative to the southern hemisphere. 

The units of analysis should be determined by the needs of the assessment, not by the data that happen to be available. Careful consideration is required to identify which biological, spatial, and temporal units are appropriate for each assessment. This will depend on the nature and degree of spatial and temporal variation in the many factors that affect exposure and effects, including the following ... 

It has been argued that exposure of birds should usually be evaluated and effects predicted initially for individuals, and then used to evaluate consequences at larger scales (US SAP 1999), because it is individuals that experience mortality or fail to reproduce. Also, spatial and temporal variation in pesticide residues combined with... 

Improved methods and data for spatial and temporal variation... 

Spatial and temporal variation are major drivers of variability in risk. Research is required to develop the databases, models, and methods required to quantify their influence in risk assessment. 

In practical combustion systems, such as CO boilers, the flue gas experiences spatial and temporal variations. Constituent concentration, streamline residence time, and temperature are critical to determining an efficient process design. Computational fluid dynamics (CFD) modeling and chemical kinetic modeling are used to achieve accurate design assessments and NO, reduction predictions based on these parameters. The critical parameters affecting SNCR and eSNCR design are listed in Table 17.4. 

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