Predicting sedimentary bedrock subsurface weathering fronts and weathering rates

AbstractAlthough bedrock weathering strongly influences water quality and global carbon and nitrogen budgets, the weathering depths and rates within subsurface are not well understood nor predictable. Determination of both porewater chemistry and subsurface water flow are needed in order to develop more complete understanding and obtain weathering rates. In a long-term field study, we applied a multiphase approach along a mountainous watershed hillslope transect underlain by marine shale. Here we report three findings. First, the deepest extent of the water table determines the weathering front, and the range of annually water table oscillations determines the thickness of the weathering zone. Below the lowest water table, permanently water-saturated bedrock remains reducing, preventing deeper pyrite oxidation. Secondly, carbonate minerals and potentially rock organic matter share the same weathering front depth with pyrite, contrary to models where weathering fronts are stratified. Thirdly, the measurements-based weathering rates from subsurface shale are high, amounting to base cation exports of about 70 kmolc ha−1 y−1, yet consistent with weathering of marine shale. Finally, by integrating geochemical and hydrological data we present a new conceptual model that can be applied in other settings to predict weathering and water quality responses to climate change.

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Characterization of Municipal Solid Waste and Evaluation of Subsurface Water Quality In The Vicinity of Dumping Sites

International Journal for Research in Applied Science and Engineering Technology ◽

10.22214/ijraset.2017.10063 ◽

2017 ◽

Vol V (X) ◽

pp. 425-431

Author(s):

Rakesh Kumar Pandey

Keyword(s):

Water Quality ◽

Municipal Solid Waste ◽

Solid Waste ◽

Subsurface Water

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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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Base cation and silicon biogeochemistry under pine and scrub oak monocultures: implications for weathering rates

Geoderma ◽

10.1016/j.geoderma.2004.10.007 ◽

2005 ◽

Vol 126 (3-4) ◽

pp. 353-365 ◽

Cited By ~ 23

Author(s):

J.L. Johnson-Maynard ◽

R.C. Graham ◽

P.J. Shouse ◽

S.A. Quideau

Keyword(s):

Base Cation ◽

Weathering Rates ◽

Scrub Oak ◽

Silicon Biogeochemistry

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Comparison of the water quality of the surface microlayer and subsurface water in the Guangzhou segment of the Pearl River, China

Journal of Geographical Sciences ◽

10.1007/s11442-014-1101-7 ◽

2014 ◽

Vol 24 (3) ◽

pp. 475-491 ◽

Cited By ~ 8

Author(s):

Qing Liu ◽

Xiaojuan Hu ◽

Jiangluan Jiang ◽

Junyi Zhang ◽

Zhihui Wu ◽

...

Keyword(s):

Water Quality ◽

Subsurface Water ◽

Pearl River ◽

Surface Microlayer ◽

The Pearl River

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Construction of Water Table Contour Map and Geo Hydrological Studies on Krishnagiri Using GIS Techniques

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i3.10.15644 ◽

2018 ◽

Vol 7 (3.10) ◽

pp. 120

Author(s):

T Subramani ◽

S Mathialagan

Keyword(s):

Water Table ◽

Hydraulic Head ◽

Groundwater Exploration ◽

Subsurface Water ◽

Contour Map ◽

Contour Lines ◽

Gis Software ◽

Water Table Contour ◽

Contemporary Technology ◽

Water Level Contour

Geo-hydrology and groundwater exploration manner to pick out and to find the zone of recharge of groundwater in a precise river basin or a catchment .water level contour traces (or waft traces) are much like topographic strains on a map. They fully represent "elevations" in the subsurface. Water table contour lines can be used to inform which manner groundwater will glide in a given region. Plenty of wells are drilled and the hydraulic head is measured in each one. Water desk contours are drawn that be a part of areas of identical head .The ones water table contours lines are also called equipotential strains. Bear in mind: groundwater usually movements from a place of the higher hydraulic head to an area of decrease hydraulic head, and perpendicular to equipotential traces. In our challenge, we put into effect concept of water table contour map and geohydrological studies on Krishnagiri using GIS software program which plays the essential position in contemporary technology.

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Effect of Split Fertilization on Subsurface Water Quality in Wild Blueberry Fields

10.13031/aim.20141913294 ◽

2014 ◽

Keyword(s):

Water Quality ◽

Subsurface Water ◽

Wild Blueberry

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Urgent problems of surface and subsurface water quality in Altai krai and possible ways of their solution

Water Resources ◽

10.1134/s0097807816010139 ◽

2016 ◽

Vol 43 (1) ◽

pp. 121-128 ◽

Cited By ~ 1

Author(s):

V. A. Somin ◽

V. I. Zanosova ◽

L. F. Komarova

Keyword(s):

Water Quality ◽

Subsurface Water

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Nitrogen Surplus—A Unified Indicator for Water Pollution in Europe?

Water ◽

10.3390/w12041197 ◽

2020 ◽

Vol 12 (4) ◽

pp. 1197 ◽

Cited By ~ 3

Author(s):

Susanne Klages ◽

Claudia Heidecke ◽

Bernhard Osterburg ◽

John Bailey ◽

Irina Calciu ◽

...

Keyword(s):

Water Pollution ◽

Water Quality ◽

Nutrient Management ◽

European Countries ◽

Organic Fertilizers ◽

Mitigation Measures ◽

Nitrogen Surplus ◽

Nitrogen Budgets ◽

Farm Level ◽

Nitrogen Budgeting

Pollution of ground-and surface waters with nitrates from agricultural sources poses a risk to drinking water quality and has negative impacts on the environment. At the national scale, the gross nitrogen budget (GNB) is accepted as an indicator of pollution caused by nitrates. There is, however, little common EU-wide knowledge on the budget application and its comparability at the farm level for the detection of ground-and surface water pollution caused by nitrates and the monitoring of mitigation measures. Therefore, a survey was carried out among experts of various European countries in order to assess the practice and application of fertilization planning and nitrogen budgeting at the farm level and the differences between countries within Europe. While fertilization planning is practiced in all of the fourteen countries analyzed in this paper, according to current legislation, nitrogen budgets have to be calculated only in Switzerland, Germany and Romania. The survey revealed that methods of fertilization planning and nitrogen budgeting at the farm level are not unified throughout Europe. In most of the cases where budgets are used regularly (Germany, Romania, Switzerland), standard values for the chemical composition of feed, organic fertilizers, animal and plant products are used. The example of the Dutch Annual Nutrient Cycling Assessment (ANCA) tool (and partly of the Suisse Balance) shows that it is only by using farm-specific “real” data that budgeting can be successfully applied to optimize nutrient flows and increase N efficiencies at the farm level. However, this approach is more elaborate and requires centralized data processing under consideration of data protection concerns. This paper concludes that there is no unified indicator for nutrient management and water quality at the farm level. A comparison of regionally calculated nitrogen budgets across European countries needs to be interpreted carefully, as methods as well as data and emission factors vary across countries. For the implementation of EU nitrogen-related policies—notably, the Nitrates Directive—nutrient budgeting is currently ruled out as an entry point for legal requirements. In contrast, nutrient budgets are highlighted as an environment indicator by the OECD and EU institutions.

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