Solution weathering rate and origin of karst landforms and caves in the quartzite of Auyan-tepui (Gran Sabana, Venezuela)

Leonardo Piccini; Marco Mecchia

doi:10.1016/j.geomorph.2008.09.019

Calcium Budgets for Catchments as Interpreted by Strontium Isotopes

Hydrology Research ◽

10.2166/nh.1989.0007 ◽

1989 ◽

Vol 20 (2) ◽

pp. 85-96 ◽

Cited By ~ 33

Author(s):

Gunnar Jacks ◽

Göran Åberg ◽

P. Joseph Hamilton

Keyword(s):

Steady State ◽

Forest Ecosystem ◽

Coniferous Forest ◽

Strontium Isotopes ◽

Runoff Water ◽

Weathering Rate ◽

Weathering Rates ◽

Exchangeable Calcium

Strontium isotopes in precipitation, soil and runoff water can be used to establish a ratio of wet plus dry deposited Sr to Sr released by weathering. This ratio is especially enhanced in areas with old acid Proterozoic rocks (0.6-2.5 Ga) and Archean rocks (>2.5 Ga). Since Sr and Ca behave in an analogous way in the coniferous forest ecosystem the results for Sr can be used for the determination of Ca. If the deposition of calcium can be calculated reasonably accurately the weathering rate can also be estimated. Five catchments have been investigated using this approach. Three of them seem to be close to a steady state, wherein the losses and gains of calcium to the system are equal. In the two southern-most catchments there seems to be an ongoing loss of exchangeable calcium. The loss by runoff occurs with sulphate being the dominant anion. Weathering rates of 1.5 to 4.8 kg Ca/ha year have been estimated.

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A MICROMETER THICK COATING LAYER SLOWING THE WEATHERING RATE OF GLACIAL POLISH

10.1130/abs/2017am-303677 ◽

2017 ◽

Author(s):

Shalev Siman-Tov ◽

◽

Greg M. Stock ◽

Emily E. Brodsky ◽

Joseph Clancy White

Keyword(s):

Coating Layer ◽

Weathering Rate ◽

Thick Coating

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Origin of the low-medium temperature hot springs around Nanjing, China

Open Geosciences ◽

10.1515/geo-2020-0269 ◽

2021 ◽

Vol 13 (1) ◽

pp. 820-834

Author(s):

Jun Ma ◽

Zhifang Zhou

Keyword(s):

Hot Springs ◽

Hot Spring ◽

Hot Water ◽

Geothermal Water ◽

Geological Condition ◽

Medium Temperature ◽

Rock Interaction ◽

Karst Landform ◽

Karst Landforms ◽

Development And Management

Abstract The exploration of the origin of hot spring is the basis of its development and utilization. There are many low-medium temperature hot springs in Nanjing and its surrounding karst landform areas, such as the Tangshan, Tangquan, Lunshan, and Xiangquan hot springs. This article discusses the origin characters of the Lunshan hot spring with geological condition analysis, hydrogeochemical data, and isotope data. The results show that the hot water is SO4–Ca type in Lunshan area, and the cation content of SO4 is high, which are related to the deep hydrogeological conditions of the circulation in the limestone. Carbonate and anhydrite dissolutions occur in the groundwater circulation process, and they also dominate the water–rock interaction processes in the geothermal reservoir of Lunshan. The hot water rising channels are deeply affected by the NW and SN faults. Schematic diagrams of the conceptual model of the geothermal water circulation in Lunshan are plotted. The origin of Tangshan, Tangquan, and Xiangquan hot springs are similar to the Lunshan hot spring. In general, the geothermal water in karst landforms around Nanjing mainly runs through the carbonate rock area and is exposed near the core of the anticlinal structure of karst strata, forming SO4–Ca/SO4–Ca–Mg type hot spring with the water temperature less than 60°C. The characters of the hot springs around Nanjing are similar, which are helpful for the further research, development, and management of the geothermal water resources in this region.

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Current, steady-state and historical weathering rates of base cations at two forest sites in northern and southern Sweden: a comparison of three methods

Biogeosciences ◽

10.5194/bg-17-281-2020 ◽

2020 ◽

Vol 17 (2) ◽

pp. 281-304 ◽

Cited By ~ 1

Author(s):

Sophie Casetou-Gustafson ◽

Harald Grip ◽

Stephen Hillier ◽

Sune Linder ◽

Bengt A. Olsson ◽

...

Keyword(s):

Steady State ◽

Soil Depth ◽

Base Cations ◽

Base Cation ◽

Mineral Weathering ◽

Soil Horizon ◽

Soil Horizons ◽

Weathering Rate ◽

Weathering Rates ◽

Forest Sites

Abstract. Reliable and accurate methods for estimating soil mineral weathering rates are required tools in evaluating the sustainability of increased harvesting of forest biomass and assessments of critical loads of acidity. A variety of methods that differ in concept, temporal and spatial scale, and data requirements are available for measuring weathering rates. In this study, causes of discrepancies in weathering rates between methods were analysed and were classified as being either conceptual (inevitable) or random. The release rates of base cations (BCs; Ca, Mg, K, Na) by weathering were estimated in podzolised glacial tills at two experimental forest sites, Asa and Flakaliden, in southern and northern Sweden, respectively. Three different methods were used: (i) historical weathering since deglaciation estimated by the depletion method, using Zr as the assumed inert reference; (ii) steady-state weathering rate estimated with the PROFILE model, based on quantitative analysis of soil mineralogy; and (iii) BC budget at stand scale, using measured deposition, leaching and changes in base cation stocks in biomass and soil over a period of 12 years. In the 0–50 cm soil horizon historical weathering of BCs was 10.6 and 34.1 mmolc m−2 yr−1, at Asa and Flakaliden, respectively. Corresponding values of PROFILE weathering rates were 37.1 and 42.7 mmolc m−2 yr−1. The PROFILE results indicated that steady-state weathering rate increased with soil depth as a function of exposed mineral surface area, reaching a maximum rate at 80 cm (Asa) and 60 cm (Flakaliden). In contrast, the depletion method indicated that the largest postglacial losses were in upper soil horizons, particularly at Flakaliden. With the exception of Mg and Ca in shallow soil horizons, PROFILE produced higher weathering rates than the depletion method, particularly of K and Na in deeper soil horizons. The lower weathering rates of the depletion method were partly explained by natural and anthropogenic variability in Zr gradients. The base cation budget approach produced significantly higher weathering rates of BCs, 134.6 mmolc m−2 yr−1 at Asa and 73.2 mmolc m−2 yr−1 at Flakaliden, due to high rates estimated for the nutrient elements Ca, Mg and K, whereas weathering rates were lower and similar to those for the depletion method (6.6 and 2.2 mmolc m−2 yr−1 at Asa and Flakaliden). The large discrepancy in weathering rates for Ca, Mg and K between the base cation budget approach and the other methods suggests additional sources for tree uptake in the soil not captured by measurements.

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