Spatial and temporal variations in soil chemistry on the Amazon floodplain

Victória, Reynaldo Luiz; Martinelli, Luiz Antônio; Richey, Jeffrey E.; Devol, Allan H.; Forsberg, Bruce R.; Ribeiro, M. N. Góes

doi:10.1007/bf00620548

Cited by 14 publications

(6 citation statements)

References 6 publications

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“…The results in figure 4 showed that the contents of these nutrients decreased downstream. Similar to what was observed by Victoria et al (1989). These authors suggest that the downstream decline in Ca 2+ and Mg 2+ concentrations in floodplain soils may be due to a change in the chemical composition of the river sediments.…”

Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)supporting

confidence: 82%

“…According to Junk (2020), the availability of K + in the floodplain is underestimated, because much of the non-exchangeable K + is stored in minerals such as illite, and can be available by plants. Unlike the other cations, the K + concentration along the Solimões/Amazonas channel was significantly higher in the Lower Solimões/Middle Amazon region (Figure 4), probably due to the input of the Rio Madeira, which tends to be rich in K + , as also observed by Victoria et al (1989).…”

Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)mentioning

confidence: 53%

“…Although the majority of the samples analyzed had high levels of K + , in a few cases in the Upper and Middle Solimões River and Lower Amazon River, the level of this nutrient can become limiting to crop production (Fajardo et al, 2009). Low K values have been reported by other authors in floodplain soils (Victoria et al, 1989;Alfaia and Falcão, 1993). Lopes et al (2006) observed that agricultural use considerably decreased the contents of K + to a depth of 0.30 m in the floodplain soils along the Guamá River in Pará State.…”

Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)mentioning

confidence: 64%

“…In general, Ca 2+ is the predominant cation in the floodplain exchange complex, followed by Mg 2+ . Exchangeable Ca predominates due, in part, to the selective weathering of dolomite and calcite deposits in the Andean headwater region (Sombroek, 1984;Victoria et al, 1989). Also, the expressive contents of these nutrients can be attributed to the recent nature of the mineral constituents and the high chemical activity of the clay fraction in these soils (Sombroek, 1984;Horbe et al, 2007;Guimarães et al, 2013, Magalhães andGomes, 2013).…”

Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)mentioning

confidence: 99%

“…Many of these plants undergo a seasonal growth cycle with high production levels (Paspalum fasciculatum attains biomass value of 40 t ha -1 of dry weight after a growth period of 8 months), followed by rapid decomposition (Junk, 1984). Large quantities of nutrients are presumably taken up from floodplain soils during the growth period and then returned when the plants decompose (Victoria et al, 1989).…”

Section: Total N and Organic Carbonmentioning

confidence: 99%

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Chemical features of floodplain soils under different land-uses in the Solimões/Amazon River basin

Alfaia¹,

Ayres²,

Neves³

et al. 2022

Revista Brasileira De Ciência Do Solo

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Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)supporting

confidence: 82%

Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)mentioning

confidence: 53%

Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)mentioning

confidence: 64%

Section: Macronutrients (Calcium Magnesium Potassium and Phosphorus)mentioning

confidence: 99%

Section: Total N and Organic Carbonmentioning

confidence: 99%

See 3 more Smart Citations

Chemical features of floodplain soils under different land-uses in the Solimões/Amazon River basin

Alfaia¹,

Ayres²,

Neves³

et al. 2022

Revista Brasileira De Ciência Do Solo

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Uranium and thorium isotopes in the rivers of the Amazonian basin: hydrology and weathering processes

Marques

Al‐Gharib

Bernat

et al. 2002

Hydrological Processes

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Abstract:Two expeditions (October 1989 and May 1992) were carried out to two points of the main Amazon River channel and four tributaries. The Solimões and Madeira rivers, taking their origin in the Andes, are whitewater rivers. The Negro River is a typical acid, blackwater river. The Trombetas River flows through bauxite-rich areas, and is characterized by low concentrations of dissolved humic substances. The 238 U, 234 U, 232 Th and 230 Th activities were recorded from dissolved, suspended particulate phases and river bank sediments. The latter were analysed for their 226 Ra, 228 Ra and 210 Pb contents, and also subjected to leaching with 0Ð2 M hydroxylamine-hydrochloride solution to determine the concentrations of radionuclides bound to amorphous Fe hydroxides and Mn oxides and hydroxides.The dissolved U average concentration in the Amazon system is ten times lower than the mean world river concentration. The uranium concentration observed atÓbidos in the lower Amazon (0Ð095 µg L 1 ), where the U content in the river bank sediments and suspended matter is lowest, suggests U release from the solid phase during river transport. About 485 t of U are transported annually to the Amazon delta area in dissolved form, and 1943 t bound to suspended particulate matter.Total U and Th concentrations in the river bank sediments ranged from 1Ð59 to 7Ð14 µg g 1 and from 6Ð74 to 32 µg g 1 , respectively. The highest concentrations were observed in the Trombetas River. The proportion extracted by means of the hydroxylamine solution (HL) was relatively high for U in the Trombetas river bank sediment (31%) and for Th in the Solimões sediment (30%).According to the alpha recoil effects, the 234 U/ 238 U activity ratios of the Andean river waters and downstream Amazon water (Óbidos) were >1, but were <1 in the Negro River (at Manaus). The activity ratios of dissolved U correlate with pH and also with the U activity ratios in the river bank sediment hydroxylamine extracts. As expected, the 234 U/ 238 U activity ratios in river bank sediments were <1 in the Andean rivers and in the downstream Amazon, but they were >1 in the Trombetas and Negro rivers. Such ratios probably result from the binding of dissolved uranium to solid sediment.The 228 Th/ 232 Th ratios of river bank sediments were close to unity (except for the Negro River, where it is lower), suggesting no significant Th exchanges between the river water and the sediment. The 226 Ra/ 232 Th activity ratios were <1, and the 226 Ra/ 228 Ra activity ratios generally were significantly higher than the activity ratios of their respective parents. This perhaps is the result of easier leaching of the 226 Ra parent, 230 Th, from solid material (owing to the alpha recoil effect) than of the 228 Ra parent. Uranium and thorium isotopes were used as tools to evaluate the chemical weathering rate of rocks in the Amazon system, which was estimated to be 2Ð7 cm 1000 year 1 s 1 .

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Inland variability of carbon–nitrogen concentrations and δ¹³C in Amazon floodplain (várzea) vegetation and sediment

Martinelli¹,

Victória²,

Camargo³

et al. 2003

Hydrological Processes

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Abstract:We analysed carbon, nitrogen and υ 13 C values in sediment sampled in the Amazon floodplains. The surface sediment samples were collected along inland transects divided according to their vegetation cover: (a) forest, where the dominant vegetation was inundation forests; (b) grass, where the dominant vegetation was grasses, mainly from Echnochloa polystachya; (c) mixed, where the vegetation changed from grasses near the river bank to forest inland. The average sediment carbon and nitrogen concentrations were significantly higher in forest samples (C D 0Ð99%, N D 0Ð12%) than in grass samples (C D 0Ð84%, N D 0Ð10%). The average sediment υ 13 C was significantly heavier in grass ( 26Ð7‰) than in forest samples ( 28Ð6‰), reflecting the isotopically heavier C 4 grasses carbon. In the forest and mixed transects inland, increases in the carbon and nitrogen concentrations were observed. At approximately 50 to 60 m from the riverbank, the concentration of carbon and nitrogen became similar to the river particulate organic carbon (POC) concentration, which is the primary floodplain sediment source. We hypothesized that this trend is caused by the deposition of carbon-and nitrogen-depleted sand-size particles in the first few metres of the floodplain, whereas the more enriched silt-clay particles are preferentially deposited far inland. In contrast to inland trends, no significant downriver trend was observed in the carbon and nitrogen concentrations. However, a downriver υ 13 C increase was observed for sediment in grass-covered areas. Based on υ 13 C values in different várzea environments, we estimated the relative contribution of riverine POC and vegetation material present in the várzea sediments under different vegetation covers. For forest sediment samples we estimated that 60% of the carbon was derived from the riverine POC and the forests provided the remaining 40%. For open areas covered with grasses we estimated that only 10% was derived from these plants, and 90% was derived from riverine POC.

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Spatial and temporal variations in soil chemistry on the Amazon floodplain

Cited by 14 publications

References 6 publications

Chemical features of floodplain soils under different land-uses in the Solimões/Amazon River basin

Chemical features of floodplain soils under different land-uses in the Solimões/Amazon River basin

Uranium and thorium isotopes in the rivers of the Amazonian basin: hydrology and weathering processes

Inland variability of carbon–nitrogen concentrations and δ¹³C in Amazon floodplain (várzea) vegetation and sediment

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Spatial and temporal variations in soil chemistry on the Amazon floodplain

Cited by 14 publications

References 6 publications

Chemical features of floodplain soils under different land-uses in the Solimões/Amazon River basin

Chemical features of floodplain soils under different land-uses in the Solimões/Amazon River basin

Uranium and thorium isotopes in the rivers of the Amazonian basin: hydrology and weathering processes

Inland variability of carbon–nitrogen concentrations and δ13C in Amazon floodplain (várzea) vegetation and sediment

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Inland variability of carbon–nitrogen concentrations and δ¹³C in Amazon floodplain (várzea) vegetation and sediment