Inputs Amazon River

Several studies have examined the partitioning of U on particles and colloids. Results from detailed sampling and particle separation in the Amazon estuary shows that most of the uranium at the Amazon River mouth is associated with particles (>0.4 im) and that >90% of the uranium in filtered water (<0.4 im) is transported in a colloidal phases (from a nominal molecular weight of 10 000 MW up to 0.4 im) (Swarzenski et al. 1995 Moore et al. 1996). Mixing diagrams for uranium in different size fractions in the Amazon estuary reveal that uranium in all size fractions clearly display both removal and substantial input during mixing. 

As shown in Figure 14.8, kaolinite concentrations are highest in tropical and equatorial latitudes, particiflarly off the western coasts of North Africa and Australia (>40%) and the northeastern coasts of Australia and South America (30%). The first two are the result of aeolian transport by the Trade Winds from the Saharan and Australian deserts, respectively. The other two are the result of river input from the eastern Australian continent and the Amazon River. 

Interactive consideration of the dynamics of the biosphere as a climatic system component is particularly interesting. The importance of this problem can be exemplified by estimates of the climatic impact of the clearing of tropical forests in the Amazon basin obtained by Bunyard (1999). The Amazon River basin, consisting mainly of wet tropical forest (WTF), performs several important and still inadequately considered functions, including the input of energy from tropical to higher latitudes, which is under threat in view of the high rate of WTF destruction. 

Allochthonous inputs from the Amazon River and local drainage thus contribute 4.3 Tg yr of organic carbon to floodplain. This represents approximately 4% of total plant production within the floodplain. However, the majority of the allochthonous inputs are refractory carbon, while most of the aquatic plant production is available to other trophic levels. 

Diztom/Richelia intracellularis associations can be spatially extensive and contribute intensive input of N through N2 fixation in the upper water column. For instance, a Hemiaulus hauckii/Richelia bloom encountered by Carpenter et al. (1999) off the northeast coast of South America in Oct 1996 was observed over a linear cruise track of 2500 km and accounted for very substantial levels of N2 fixation (see below). The symbionts for individual diatoms such as Hemiaulus and Rhizosolenia while morphologically similar are genetically distinct and discrete probes for each association have been developed and applied in the Amazon River plume to enumerate the relative densites of these two associations (Foster et al., 2007). 

The first and only detailed analysis of the terms in equation 1 for an Amazon floodplain lake was performed at Lake Calado (Lesack and Melack 1991, 1995 Lesack 1993a, 1995). Lake Calado has a BA LA ratio ranging from about 7 at high water to about 28 at low water. River water invaded the lake at the start of rising level in the mainstem, but by midrising water, lake water steadily flowed from the lake into the river, while river levels continued to rise. By the end of the water year, Lake Calado had experienced a 10 m range in water level, and local runoff had contributed 57% of the total water input, river inflow 21%, rainfall directly onto the lake... 

The total organic carbon balance for lakes on the central Amazon floodplain can be examined by comparing total inputs due to primary production and external loading with total losses (Table 14.4). The combined input of organic carbon due to primary production, river import and local runoff was estimated at 117.3 Tg C yr. Combined losses due to biogenic gas emission and... 

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