Fig 1.
Location of the studied transect at the border of Salina Verde in the Pantanal wetland of Nhecolândia.
Fig 2.
Concentration diagrams based on Na contents showing the regional trends (solid line) compiled from Furian et al. [32] and the chemistry of waters collected in auger holes along the transect of Salina Verde.
Note the sigmoidal shape of dissolved K along the concentration process.
Fig 3.
Standard soil layout and clay fraction distribution compiled from previous studies carried out around saline-alkaline lakes in Nhecolândia.
See text for description of horizons 1 to 4.
Fig 4.
Cross section showing the soil layout along the transect.
AH are auger holes for water collection, Electrical conductivity (EC) in mS cm-1, ⊗ are samples presented in Fig 5, Pz denotes the piezometer used for water level monitoring in the beach.
Fig 5.
X-ray diffraction of glycoled-oriented clay along the transect showing smectite-dominant (1) and mica-dominant horizon (4).
Fig 6.
(a) Streaks of organic matter in horizon 2; (b, c and d) SEM pictures of the white efflorescent crust consisting of mats of amorphous material.
Fig 7.
Mossbauer spectroscopy carried out on fine clay material of the greenish horizon 4 dominated by Fe-mica.
The deconvolution into 3 doublets shows octahedral Fe3+ (doublets 1 and 3) and secondarily octahedral Fe2+ (doublet 2).
Table 1.
Mössbauer spectrometry characteristics of fine clay mica from horizon 4.
Fig 8.
Near infrared reflectance on fine clay material of horizon 1 and 4.
V and δ denote stretching and bending, respectively.
Fig 9.
Water level monitoring of the fresh watertable of the draining fields, the saline beach groundwater and Salina Verde.
Level zero corresponds to the bottom of the lake.
Fig 10.
Si, K, Fe, Al and DOC contents in solutions after centrifugation and subsequent filtration at 0.45 μm, 30 kDa, 10 kDa and 3 kDa.
SV denotes Salina Verde and AH are auger holes shown along cross section in Fig 4.
Fig 11.
Fe and Al contents in centrifuged solutions, centrifuged and filtered solutions, and after hydrogen peroxide treatment and subsequent filtration at 0.45 μm.
The peroxide treatment tends to reduce the proportion of Fe and Al retained by filtration.
Fig 12.
Examples of alkaline lakes in the Nhecolândia showing elongated deep borders (arrows) suggesting that the chemical withdrawal-aggradation process impacts the lake depression.
Bar = 200 m. Original pictures are available at Google EarthTM imagery.