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ND-09 Abstract

Biogeochemical Dynamics in River Corridors of the Amazon Basin and Their Response to Anthropogenic Change

Jeffrey E. Richey — University of Washington (US-PI)
Reynaldo Luiz Victoria — CENA - Centro de Energia Nuclear na Agricultura (USP) (SA-PI)

Objectives





We propose studies in 4 theme areas of LBA Ecology, with a primary emphasis on the

dynamics of surface water chemistry, and secondary emphases on nutrient dynamics, trace

gas fluxes, and carbon. Our research objectives are to:











  • Establish the geographic and geochemical sources of C, N, and P species for river

    corridors,


  • Define the biogeochemical consequences for water chemistry (and to a lesser extent gas

    emissions) of anthropogenic perturbations against the background of natural environmental

    variability,


  • Determine the downstream fate of sediments, nutrients, and organic matter, as mediated

    by the transport properties of the river system and the reactivity of the materials

    themselves.


  • Extrapolate these results and to contribute to overall biogeochemical modeling in LBA by

    assimilating data on carbon, nitrogen, and moisture fluxes from experimental, tower and

    aircraft databased on the modeling and remote sensing activities of our EOS IDS project.










Research will concentrate in the Rio Ji-Paraná basin, and will be extended with more

modest measurements of other basins in Rondônia and arrayed along the LBA transects

elsewhere in the Amazon (at sites where significant local collaboration is feasible). We

will work along land-use and moisture gradients, with the intention of quantifying key

fluxes and understanding the underlying dynamics for river corridors.





We will (with final and exact details subject to further negotiations with LBA

partners):









1. Develop a variable-scale drainage basin element model for biogeochemical processes

which includes water balances and routing (in conjunction with hydrology work elsewhere in

LBA). This will require development of multi-scale digital elevation models and spatial

data layers (topography, soils, land use) sufficient to evaluate 4 km, 1 km, and

ultimately 30 m resolution. The enhanced hydrological models will allow us to implement a

more detailed consideration of the mechanistic processes and factors controlling within

the CASA modeling environment of the evolution and partitioning of organic matter,

nutrients, and trace gases.



2. Establish and operate a distributed sampling network in the Rio Ji-Paraná basin

which will allow us to measure the temporal variability in the distributions of water flux

and attendant chemical composition at the exit to the basin, then progressively work our

way upstream, sampling the diverse sub-regions, approaching the low order streams. To

generalize results, we will explore lower resolution field areas elsewhere in Rondônia

and in the Amazon.



3. As these sites we will make measurements of hydrological parameters, groundwater and

stream chemistry (NO3, NH4, PO4, alkalinity, pH, O2,

particulate and dissolved organic CNP, major anions and cations, and routine stable

isotopes, surface area, individual amino acids, individual sugars, and lignin-derived CuO

reaction products.), and(funding dependent) gas concentrations and fluxes (CH4,

N2O, and CO2). Sources of N2O through the d15-N and d18O

of N2O, while transformations of ON to NO3 using d15-N techniques.

In-channel production and mineralization will be investigated with the distributions of

dissolved gases (O2, CO2, N2O, CH4, 18O2).



4. Regional extrapolation in the overall context of biogeochemical cycling will be

based on time series multispectral image measurements along the LBA transects to validate

and determine uncertainties in remote sensing inputs (e.g., FPAR, net solar radiation,

temperature, non-photosynthetic vegetation) from image data. These data are used as inputs

to our EOS-IDS regional hydrology/biogeochemical cycling model.









 





Last Updated: October 1998

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