Sediment geochemistry, mineral precipitation and clay neoformation on the Mkuze River floodplain, South Africa

Humphries, Marc; Kindness, Andrew; Ellery, W.N.; Hughes, J. C.

doi:10.1016/j.geoderma.2010.03.010

Cited by 22 publications

(25 citation statements)

References 31 publications

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“…In the fine fraction (b63 μm) of the samples collected offshore of the northeastern Sicilian coast, Italy, Saccà et al (2011) found that Fe oxides varied only slightly (7.7-9.0%, with a possible outlier of 6.5%) in one site and 9.4-10% in the other. Humphries et al (2010), however, reported substantially higher weight percentages with a wider variation interval of Fe 2 O 3 in the clay fraction of sediment samples from the Nkuze Wetland System, South Africa, ranging from 10.2% to 21.2%. Clearly, the Fe-clay relationship is regionally but not universally uniform.…”

Section: The Relationships Of Fe-clay and Rb-clay And Model Applicabmentioning

confidence: 85%

Characterizing soils using a portable X-ray fluorescence spectrometer: 1. Soil texture

2011

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Section: The Relationships Of Fe-clay and Rb-clay And Model Applicabmentioning

confidence: 85%

Characterizing soils using a portable X-ray fluorescence spectrometer: 1. Soil texture

2011

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“…Floodplains are important sinks of particulate Si (Meybeck and Vörösmarty 2005) and can similarly remove DSi from solution, biologically or though mineral neoformation (Humphries et al 2010(Humphries et al , 2011. However, floodplains can also release DSi through chemical weathering (Lupker et al 2012), so the net effect is unclear.…”

Section: Evidence For Continental Dsi Retention From River Geochemistrymentioning

confidence: 99%

Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration

et al. 2014

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Weathering of silicate minerals releases dissolved silicate (DSi) to the soil-vegetation system. Accumulation and recycling of this DSi by terrestrial ecosystems creates a pool of reactive Si on the continents that buffers DSi export to the ocean. Human perturbations to the functioning of the buffer have been a recent research focus, yet a common assumption is that the continental Si cycle is at steadystate. However, we have no good idea of the timescales of ecosystem Si pool equilibration with their environments. A review of modelling and geochemical considerations suggests the modern continental Si cycle is in fact characterised in the longterm by an active accumulation of reactive Si, at least partially attributable to lakes and reservoirs. These lentic systems accumulate Si via biological conversion of DSi to biogenic silica (BSi). An analysis of new and published data for nearly 700 systems is presented to assess their contribution to the accumulating continental pool. Surface sediment BSi concentrations (n = 692) vary between zero and [60 % SiO 2 by weight, apparently independently of lake size, location or water chemistry. Using sediment core BSi accumulation rates (n = 109), still no relationships are found with lake or catchment parameters. However, issues associated with single-core accumulation rates should in any case preclude their use in elemental accumulation calculations. Based on lake/reservoir mass-balances (n = 34), our best global-scale estimate of combined lake and reservoir Si retention is 1.53 TMol year -1 , or 21-27 % of river DSi export. Again, no scalable relationships are apparent, suggesting Si retention is a complex process that varies from catchment to catchment. The lake Si sink has implications for estimation of weathering flux generation from river chemistry. The size of the total continental Si pool is poorly constrained, as is its accumulation rate, but lakes clearly contribute substantially. A corollary to this emerging understanding is that the flux and isotopic composition of DSi delivered to the ocean has likely varied over time, partly mediated by a fluctuating continental pool, including in lakes.

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“…Tooth et al, 2002;Tooth et al, 2007;Grenfell et al, 2009). Recent studies of sediment, groundwater and porewater geochemistry have identified the Mkuze Wetland System as an important sink for solutes (Humphries et al, 2010;Barnes et al, 2002). This system, representing South Africa's largest freshwater wetland area, forms part of the iSimangaliso World Heritage Site and plays an ecologically important role in filtering sediment from water entering Lake St. Lucia.…”

Section: Introductionmentioning

confidence: 99%

137Cs and 210Pb derived sediment accumulation rates and their role in the long-term development of the Mkuze River floodplain, South Africa

et al. 2010

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Sediment geochemistry, mineral precipitation and clay neoformation on the Mkuze River floodplain, South Africa

Cited by 22 publications

References 31 publications

Characterizing soils using a portable X-ray fluorescence spectrometer: 1. Soil texture

Characterizing soils using a portable X-ray fluorescence spectrometer: 1. Soil texture

Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration

137Cs and 210Pb derived sediment accumulation rates and their role in the long-term development of the Mkuze River floodplain, South Africa

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