Abstract. The Tana River basin (TRB) is the largest in Kenya (~120 000 km2). We conducted a survey during dry season throughout TRB, analyzing broad suite of biogeochemical parameters. Biogeochemical signatures headwater streams were highly variable. Along middle and lower river course, total suspended matter (TSM) concentrations increased more than 30-fold despite absence tributary inputs, indicating important resuspension events internally stored sediment. These resuspended sediment inputs...

We investigate the dissolved δ 30 Si of Congo River, world's second largest riverine source to ocean. Small tributaries rich in organic carbon running through wetlands (“Black Rivers”) exhibit lowest ever measured surface waters (+0.02 ± 0.15‰), whilst main branch and have higher values (+0.98 0.13‰), well within average what has been so far. Our data suggest that contribution Black Rivers total discharge basin is 22 10% mostly controlled by weathering intensity rather than fluxes. propose...

One of the most widely used sample preparation methods for Si isotopic analyses (δ30Si and δ29Si) is based on cationic chromatography, which does not remove anions from samples. Although it was first thought that presence in natural concentrations distort analyses, has recently been shown sulfate can induce a significant shift ratio measurements above SO42−/Si ratios (wt) 0.02. Here, we show dissolved organic matter also major bias when analysing river waters. To overcome these non-spectral...

We report 2 yr of monthly data from the Congo River (the second largest river in world) on dissolved silicon concentrations, biogenic silica particle isotopic signatures silicon, and siliceous counts. Diatoms predominated fraction, especially during low flow; phytoliths sponge spicules were more abundant than diatoms only rainy season, when fluxes are low. Biological processes dominated seasonal variations δ 30 Si ratio that superimposed a constant abiotic value +0.70‰ ± 0.05‰ throughout...

We present in this article a rapid method for B extraction, purification and accurate concentration δ 11 measurements by ID ‐ ICP MS MC , respectively, different vegetation samples (bark, wood tree leaves). developed three‐step procedure including (1) microwave digestion, (2) cation exchange chromatography (3) microsublimation. The entire can be performed single working day has shown to allow full recovery yield measurement repeatability as low 0.36‰ (± 2 s ) isotope ratios. Uncertainties...

Abstract. Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell freshwater bivalve Pleiodon spekii as a geochemical archive these periodic hydrological changes tuned by monsoon regime. The results three-year-long limnological and survey coastal waters performed dissolved particulate fractions were compared to LA-ICP-MS profiles Mn in five aragonitic shells from same lake location. Three...

Despite increasing recognition of the relevance biological cycling for Si in ecosystems and export from soils to fluvial systems, effects human cultivation on cycle are still relatively understudied. Here we examined stable isotope (δ30Si) signatures soil water samples across a temperate land use gradient. We show that – independent geological climatological variation there is depletion light isotopes intensive croplands managed grasslands relative native forests. Furthermore, our data...

Abstract Silicon (Si) is known to help plants mitigate environmental stresses and nutrient deficits. In some regions, the limited plant-available Si in soils can have detrimental effects on yields. Crop residue recycling used maintain amount of soils. However, effect crop management practices availability remains largely understudied. Here, we study three different rice Si-depleted fields northern Vietnam. These were (1) direct incorporation residues into soils, (2) burning field, (3) use as...

Abstract. Effects of oil-palm (Elaeis guineensis Jacq.) management on silicon (Si) cycling under smallholder plantations have hardly been investigated. As oil palms are Si accumulators, we hypothesized that practices and topsoil erosion may cause losses changes in spatial concentration patterns topsoils cultivation. To test this hypothesis, took samples mature well-drained riparian areas Jambi Province, Indonesia. The were taken from four different zones within each plot: palm circles, rows,...

In Vietnam, approximately 39 million tons of rice (Oryza sativa) residues accrue every year. this study, we quantified soil nutrient balances paddy fields under different crop-residue management practices in northern Vietnam. On twelve farms, calculated for the four prevalent rice-residue practices, i.e., (1) direct incorporation into soil, (2) application compost, (3) burning on field, and (4) use as fodder livestock. Soils to showed a positive balance, which indicates that fertility can be...

Abstract The effects of land use and fire on ecosystem silicon (Si) cycling has been largely disregarded so far. We investigated the impacts Si release from topsoils litter lowland rainforest oil-palm plantations in Jambi Province, Indonesia. Lower concentrations amorphous silica (ASi) were found plantation (2.8 ± 0.7 mg g − 1 ) compared to (3.5 0.8 ). Higher total detected frond piles (22.8 4.6 (12.7 2.2 To test impact fire, materials burned at 300 °C 500 shaken with untreated samples...

Abstract. We analyzed changes in water quantity and quality at different spatial scales within the Tapajós River basin (Amazon) based on experimental fieldwork, hydrological modelling, statistical time-trend analysis. At a small scale, we compared river discharge (Q) suspended-sediment concentrations (SSC) of two adjacent micro-catchments (< 1 km2) with similar characteristics but contrasting land uses (forest vs. pasture) using empirical data from field measurements. an intermediary...

Abstract. The Tana River basin (TRB) is the largest in Kenya (~120 000 km2). We conducted a survey during dry season throughout TRB, analyzing broad suite of biogeochemical parameters. Biogeochemical signatures headwater streams were highly variable, but some organic carbon (OC) characteristics (δ13CPOC, DOC/POC ratios and %POC/TSM) clearly correlated to surface soil characteristics. Along middle lower river course, total suspended matter (TSM) concentrations increased more than 30-fold...

Abstract Phytoliths make up the predominant fraction of biogenic silica in plant litter and soils. Thus, they represent a major source dissolved silicon (Si) soil-plant systems. Dissolution phytoliths from Si-accumulating crops such as rice has been well studied recent years. However, phytolith dissolution oil-palm plantations remains largely understudied. In this study, we compared rates isolated fronds, litter, rainforest litter. Our results showed that fronds an important reservoir easily...

Abstract. Most plant-available Si in strongly desilicated soils is provided through litter decomposition and subsequent phytolith dissolution. The importance of silicon (Si) cycling tropical soil–plant systems raised the question whether oil-palm (Elaeis guineensis Jacq.) cultivation alters cycling. As oil palms are considered hyper-accumulators, we hypothesized that much stored above-ground biomass with time. Furthermore, system might lose considerable amounts every year fruit-bunch...