Watershed region

Riverine Nr export to the coastal zone (TgN/y) in the past (1860, left bar), present (1990, center bar) and future (2050, right bar). Dry and Inland watershed regions that do not transmit to coastal areas are shown In gray. Source From Galloway, J. N., et al. (2004). Biogeochemistry 70, 153-226. 

WM lesions are rated separately in four WM areas periventricular, deep, watershed, and subcortical WM. By definition, periventricular WM foci have to be in contact with the ventricular wall, deep WM foci separated from the ventricles by a strip of normal-appearing WM and located outside watershed regions. Watershed regions are the areas located between the territories of two of the main cerebral arteries, like middle cerebral artery and anterior cerebral artery or middle cerebral artery and posterior cerebral artery. The subcortical... 

The author examined comatose patients with suspected cortical ischemia with DWI who had suffered from cerebral hypoxia often after cardiac arrest (Lovblad et al. 2004). A further evaluation of an expanded series of these patients is presented in Table 16.1 26 patients with lesions attributed to hypoxia that resumes the clinical signs of all patients. This series confirms the initial observation that DWI was superior to T2-weighted MRI regarding the prediction of lesion extent. Table 16.2 presents the patterns and localizationof findings. The DWI lesions were localized in the typical watershed regions in 7 of 26 (27%) (Fig. 16.8). The cortical lesions were unilateral in one patient (4%). Basal ganglia involvement was found in 10 of 26 patients (38%), and there was also white matter involvement in 9 of 26 patients (35%) (Figs. 16.8 and 16.9). Additional infratentorial lesions were found in 3 of 19 patients (35%) (Fig. 16.8). 

It has been estimated that riverine and atmospheric N inputs in the North Atlantic Ocean basin are at least equal to and may exceed N inputs by biological N2 fixation (Howarth et al., 1996 Paerl and WhitaU, 1999). Therefore, our understanding of marine eutrophication dynamics needs to consider a range of scales including ecosystem, watershed, regional and global. 

Table 8. Atmospheric deposition of oxidized (NOy) and reduced (NHx)/ormi of nitrogen to the watershed regions. Modem values are total current deposition as reported in Prospero et al (1996), pre-industrial values are modeled estimates (Howarth et al, 1996), and anthropogenic values are the difference between modem and pre-industrial. All values are in kg/knr/year.

Figure 5. Application of nitrogen in fertilizer and by atmospheric deposition ofFiOy to 13 of the watershed regions. Values are in kg N/km /year. Fertilizer inputs dominate net anthropogenic nitrogen inputs in most, but not all, regions of the North Atlantic basin (Howarth, 1996).

Environment Canada. 1999. Environment Canada, Environmental Protection Branch, Atlantic Region. March 1999. Pesticide residue in sediment and water from two watersheds in Prince Edward Island,... 

When examining the Syrdaiya and Amurdaiya watersheds in 1979-80, it was found that DDT concentrations reached 0.119 mkg/l, and lindane concentrations reached 0.076 mkg/l [23]. In the cotton-growing regions of Uzbekistan in the beginning of the 1960s, concentrations of DDT in the canals and ditches reached 5.4 mg/1, of Aldrin reached 1.2 mg/l (600 times higher than the acceptable level), and of HCH reached 2.52 mg/l [A49, 27]. The concentration of methylmercaptophos reached 9.2 mg/l (900 times the acceptable level) in the water sources of the Khorezm Oblast of Uzbekistan [28]. 

Soil compartment chemical fate modeling has been traditionally performed for three distinct subcompartments the land surface (or watershed) the unsaturated soil (or soil) zone and the saturated (or groundwater) zone of a region. In general, the mathematical simulation is structured around two major cycles the hydrologic cycle and the pollutant cycle, each cycle being associated with a number of physicochemical processes. Watershed models account for a third cycle sedimentation. 

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