Vargem Grande

Figure 15.2 Amazon River discharge at three locations within Brazil between 1988 and 1992 (1) OBI = Obidos, (2) MAN = Manacapum, and (3) VG = Vargem Grande. The horizontal dotted line represents the overbank condition at Manacapuru.

Figure 15.5 Downstream distributions of dissolved species between Vargem Grande and 6bidos the Brazilian Amazon. Distributions for each species are given for both rising-water and falling-water periods, with the particular concentration scale applicable to both periods. Aik = alkalinity, pC02 = dissolved CO2 gas, O2 = dissolved oxygen, PO4 = phosphate ion, DOC = dissolved organic carbon and NO3 = nitrate ion. Solid dashed and thick gray lines are as defined in Fig. 15.4. All units are pM except alkalimty, which is peq 1. ...

Figure 15.8 Weight percent organic carbon (%OC) versus mineral surface area (SA). Capital letters represent bulk samples from Obidos (O), Vaigen Grande (V), and Manacapuru (M) lowercase letters represent data from SPUTT-fractionated samples from Vargem Grande (v) and Manacapuru (m).

Three processes primarily control the forms and fluxes of particulate and dissolved materials in the Amazon mainstem input, mixing, and within-reach processing. With respect to the data presented, the CAMREX program has taken the upstream input to the Brazilian Amazon as the measurements made at Vargem Grande (Fig. 15.1). With the notable exception of the Rio Madeira, all the lower tributaries are more dilute in most chemical species than the upstream input. Consequently, the downstream decreases seen in most variables are due primarily to mixing of Andean white water with dilute, less turbid lowland water (Gibbs 1972, Richey and Victoria 1993,... 

Figure 15.14 Ratio of fine particulate organic carbon (FPOC) to dissolved organic carbon (DOC) versus fine suspended sediment (FSS). Capital letters denote the mainstem stations at Obidos (O), Manacapuru (M), and Vargem Grande (V) and lowercase letters are tributaries Negro (n), Madeira (m), Jurua (j), Japura (r), Purus (p), and Igi (i).

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