Tapajos river

Roulet M, Lucotte M, Saint-Aubin A, Tran S, Rheault I, Farella N, de Jesus da Silva E, Dezencourt J, Sousa Passes CJ, Santos Soares G, Guimaraes JR, Mergler D, Amorim M. 1998. The geochemistry of mercury in central Amazonian soils developed on the Alter-do-Chao formation of the lower Tapajos River valley, Para state, Brazil. Sci Total Environ 223 1-24. 

Figure 2.5 Rainfall and river variability in Amazonia, (a) Rainfall in the northern Amazonia, (expressed by the NAR index, Marengo [1992]), (b) discharges of the Amazon River at Obidos, (c) Solimoes river at Manacapum, (d) Tapajoz River at Santarem, (e) Tapajos River at Itauituba (Marengo and Hastenrath 1993).

El Nino) are mutually consistent, while the rest of the years do not show consistency. In fact, the river data show a period of relatively large discharges between 1972 and 1979 at the Solimoes basin, also observed at the Tapajos River and the main Amazon stream. 

Akagi H, Malm 0, Branches F JP, et al. 1995. Human exposure to mercury due to gold mining in the Tapajos river basin, Amazon, Brazil Speciation of mercury in human hair, blood and urine. Water Air and Soil Pollution 80(l-4) 85-94. 

Malm O, Branches FJ, Akagi H, et al. 1995. Mercury and methylmercury in fish and human hair from the Tapajos River Basin, Brazil. Sci Total Environ 175(2) 141-150. 

Castilhos, Z.C., E.D. Bidone, and L.D. Lacerda. 1998. Increase of the background human ejq)osure to mercury through fish consumption due to gold mining at tiie Tapajos River region, Para State, Amazon. Bull. Environ. Contam. Toxicol. 61(2) 202-209. 

Variations of river chemistry may reflect variations of the sources. As previously noted the "shield" rivers (Negro and Tapajos) have typically depleted concentrations in As, Sr, Ba, Cu, and V as compared with Andean rivets. The increased proportion of waters from these less solute-rich rivers during the high discharge period of the Amazon contributes to the observed decrease of concentrations. 

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