Major element chemistry, weathering and element yields for the Caura River drainage, Venezuela

Lewis, William M.; Hamilton, Stephen K.; Jones, Sandra L.; Runnels, Donald D.

doi:10.1007/bf02180153

Cited by 57 publications

(46 citation statements)

References 29 publications

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“…This can be explained by the considerable contributions of K from the Guayana Shield tributaries. Several Guayana Shield rivers have high concentrations of K as compared with the Orinoco River during the high water stage (Lewis et al, 1987), principally related to the weathering of feldspars and granitic rocks rich in K located in large areas of the Guayana Shield (Edmond et al, 1996). This result can indicate that during the high water stage, high levels of K are supplied by the Guayana Shield rivers, which supply approximately 40% of the K carried by the Orinoco River (Edmond et al, 1996).…”

Section: Cluster Analysismentioning

confidence: 84%

“…Edmond et al (1995) showed that the resulting correction for the data for atmospheric input is important only for Na (around 40%) and Mg (where the largest corrections were between 15 and 25% of the total Mg contained in these rivers), and that rain-derived K and Ca were an insignificant component. Similarly, studies carried out by Lewis et al (1987) on the Caura River, a major Orinoco tributary coming from the Guayana Shield, reveal a significant contribution of Na (20%) from atmospheric deposition in this river. Thus, a small but significant contribution of atmospheric input is expected only for Na in the Orinoco River waters.…”

Section: Cluster Analysismentioning

confidence: 93%

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Temporal variability of selected dissolved elements in the lower Orinoco River, Venezuela

Mora¹,

Alfonso

Sánchez³

et al. 2008

Hydrological Processes

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Abstract:Monthly analyses of pH, conductance, alkalinity, total suspended solids, dissolved major cations (Na, K, Ca and Mg), and selected dissolved trace elements (Fe, Al, Mn, Cu, Zn and Cr) were conducted on waters of the lower Orinoco River from February 2004 to May 2006. The data show strong seasonal variability. Major cations had maximum concentrations at low water, and were correlated with pH, conductance and alkalinity because of the tributaries coming from the Andean zones, where the weathering of evaporites and carbonate shales controls water chemistry. K concentrations did not show any relation with evaporite weathering, probably because large amounts of K come from the Guayana Shield rivers as a consequence of feldspar weathering. The concentrations of dissolved Fe, Mn and Cu were highest during the high water stage. Concentrations of the elements K, Cr, Zn and Cu are correlated with each other but not with dissolved Fe and Al, which probably are complexed with humic and fulvic substances. Mn concentrations did not show relationships with other variables. Inter-annual variability of dissolved elements is explained by temporal changes in precipitation.

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Section: Cluster Analysismentioning

confidence: 84%

Section: Cluster Analysismentioning

confidence: 93%

Temporal variability of selected dissolved elements in the lower Orinoco River, Venezuela

Mora¹,

Alfonso

Sánchez³

et al. 2008

Hydrological Processes

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“…Output of Si and HCO3-in drainage waters would be almost the net losses from the watershec, because Si in rainwater is generally negligible (Lewis et al, 1987;Shimada et al, 1993) and HCO; in drainage waters was almost derived from soil respiration (e.9., Reuss & Johnson, 1986). …”

Section: Sampling Methodsmentioning

confidence: 99%

“…Jordan (1982) suggested that the "terra firme" rain forest in the northem Amazon was maintained on nutrients derived from the atmosphere and nutrient input from parent material weathering was minimal. On the other hand, Lewis et al (1987) reported that for a tropical forest near the Caura River, Venezuela, mineral weathering had a major influence on the mass balances of Ca, Mg, Na and K. Tsutsumi and Li (1989) suggested that this forest ecosystem had relatively infertile soil, and Nakagawa et ql. (1995) suggested that there were lower concentrations of chemicals in forest drainage water in this site than in temperate regions.…”

mentioning

confidence: 99%

Inputs and Outputs of Major Chemicals in a Subtropical Forested Watershed in Southern China.

Nakagawa¹,

Li²,

Iwatsubo³

1998

Tropics

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Solute input and output budgets were evaluated for an evergreen broadJeaved forest in southem China. Inputs and outputs varied with season, and were linked to water flux pattems. During spring to early summer with high water flow, solute output increased especially for base cations, HCO3-, and Si. The sulfur that accumulated in the watershed (723 eqlhaly) were probably derived from atmospheric sources in the urban and industrial areas in the southwestern part of China. Considering internal cycling, nitrogen was highly retained in the soil (409 eqlha/y). Loss of K was inhibited by internal cycling. Sodium was not held tightly in this ecosystem. For Mg, content in vegetation was high, but production by weathering was also important. Atmospheric Ca input contribute to higher output of Ca.

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“…The water-level fluctuations constitute the most important macrofactor that should be considered while explaining species richness, distribution, and abundance of organisms in aquatic systems (Lewis et al 1987;Junk & Piedade 1993;Casco et al 2005;Thomaz et al 2007). On the other hand, as pointed out by Neiff (1996), the number and type of species in different hydrological stages change, and only a few can bear both phases (flood and drought).…”

mentioning

confidence: 99%

Orthoptera assemblages associated with macrophytes of floodplain lakes of the Paraná River

Capello¹,

Marchese²,

Wysiecki³

2013

Rev. Bras. entomol.

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ABSTRACT. Orthoptera assemblages associated with macrophytes of floodplain lakes of the Paraná River. The Orthoptera assemblage composition varies considerably, depending on habitat type. This study examines the spatiotemporal relationship between plant diversity, hydrometric level, environmental variables and the Orthoptera richness and abundance in floodplain lakes connected permanently or temporarily with the main channel of the Paraná River. The grasshoppers were collected fortnightly (April 2006-May 2007. A total of 17 species were recorded and classified according to their frequency of occurrence in constant (7), accessory (4), or accidental (6) species. In the two lakes, the greater species richness and abundance was recorded in summer, thereby coinciding with the highest water level of the Paraná River. The most significant correlation between the orthopteran richness and abundance was with the water level. The aquatic plant richness was significantly different between the lakes, but the vegetation was dominated by Eichhornia crassipes (Mart.) Solms. (Liliales, Pontederiaceae). The lake, which was connected permanently, presented the highest values of diversity and abundance, proving to be a more diverse assemblage. The beta diversity was higher in the temporary connected lake than in the permanently connected one. The orthopterans assemblages were different between the lakes, Cornops aquaticum and Tucayaca gracilis were the species that contributed more to the level of dissimilarity. C. aquaticum was more representative in the lake temporarily connected, while T. gracilis in the permanent connected one. The water level of the Paraná River and the connectivity of the floodplain lakes play an important role to explain the abundance and richness of their orthopteran assemblages.

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Major element chemistry, weathering and element yields for the Caura River drainage, Venezuela

Cited by 57 publications

References 29 publications

Temporal variability of selected dissolved elements in the lower Orinoco River, Venezuela

Temporal variability of selected dissolved elements in the lower Orinoco River, Venezuela

Inputs and Outputs of Major Chemicals in a Subtropical Forested Watershed in Southern China.

Orthoptera assemblages associated with macrophytes of floodplain lakes of the Paraná River

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