Isotope fractionation of zinc in the paddy rice soil-water environment and the role of 2’deoxymugineic acid (DMA) as zincophore under Zn limiting conditions

AbstractAlthough redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes progressively dominate the solution composition in response to their binding with large biologically-derived organic ligands. Confronted with field data, these results demonstrate that Fe isotope systematics in wetlands are controlled by the OM flux, masking Fe isotope fractionation arising from redox reactions. This work sheds light on an overseen aspect of Fe isotopic fractionation and calls for a reevaluation of the parameters controlling the Fe isotopes fractionation to clarify the interpretation of the Fe isotopic signature.

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A thermodynamic formulation of root water uptake

Hydrology and Earth System Sciences ◽

10.5194/hess-20-3441-2016 ◽

2016 ◽

Vol 20 (8) ◽

pp. 3441-3454 ◽

Cited By ~ 8

Author(s):

Anke Hildebrandt ◽

Axel Kleidon ◽

Marcel Bechmann

Keyword(s):

Soil Water ◽

Water Uptake ◽

Water Distribution ◽

Bound Water ◽

Root Water Uptake ◽

Flow Path ◽

Thermodynamic Evaluation ◽

Entire Flow ◽

Soil Water Distribution

Abstract. By extracting bound water from the soil and lifting it to the canopy, root systems of vegetation perform work. Here we describe how root water uptake can be evaluated thermodynamically and demonstrate that this evaluation provides additional insights into the factors that impede root water uptake. We derive an expression that relates the energy export at the base of the root system to a sum of terms that reflect all fluxes and storage changes along the flow path in thermodynamic terms. We illustrate this thermodynamic formulation using an idealized setup of scenarios with a simple model. In these scenarios, we demonstrate why heterogeneity in soil water distribution and rooting properties affect the impediment of water flow even though the mean soil water content and rooting properties are the same across the scenarios. The effects of heterogeneity can clearly be identified in the thermodynamics of the system in terms of differences in dissipative losses and hydraulic energy, resulting in an earlier start of water limitation in the drying cycle. We conclude that this thermodynamic evaluation of root water uptake conveniently provides insights into the impediments of different processes along the entire flow path, which goes beyond resistances and also accounts for the role of heterogeneity in soil water distribution.

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The role of tree stem proximity in the spatial variability of soil water repellency in a eucalypt plantation in coastal Portugal

Soil Research ◽

10.1071/sr04096 ◽

2005 ◽

Vol 43 (3) ◽

pp. 251 ◽

Cited By ~ 23

Author(s):

J. J. Keizer ◽

A. J. D. Ferreira ◽

C. O. A. Coelho ◽

S. H. Doerr ◽

M. C. Malvar ◽

...

Keyword(s):

Soil Water ◽

Water Repellency ◽

Soil Water Repellency ◽

Individual Measurement ◽

Hydrophobic Compounds ◽

Ethanol Droplet ◽

Central Portugal ◽

Living Organisms ◽

Tree Stem

Certain organic compounds derived from living organisms or their decaying parts are generally accepted to induce soil water repellency. Water repellency may therefore be expected to increase with proximity to organisms releasing hydrophobic compounds. This hypothesis is tested here for Eucalyptus globulus trees, since eucalypt species are frequently associated with elevated repellency levels. In a young, first-rotation plantation on coastal dune sands in central Portugal, repeat measurements of water repellency using the ‘Molarity of an Ethanol Droplet’ (MED) test were carried out in situ between April 2001 and May 2002. On 25 dates, repellency was measured at initially 2 and later 3 distances on 2 sides of 8–11 randomly selected trees. On 15 occasions, additional repellency measurements were performed within small grids aside 3 of the selected trees. The postulated decrease in topsoil water repellency with increased distance from eucalypt tree stems was found to apply on several individual measurement dates, as well as, more unexpectedly since repellency usually is a transient phenomenon, for the study period as a whole. The results confirm the general association of eucalypt trees with water repellency, and indicate that tree stem proximity is an important but not sufficient factor to explain repellency distribution in topsoil.

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Oxygen isotope fractionation during N<sub>2</sub>O production by soil denitrification

Biogeosciences ◽

10.5194/bg-13-1129-2016 ◽

2016 ◽

Vol 13 (4) ◽

pp. 1129-1144 ◽

Cited By ~ 26

Author(s):

Dominika Lewicka-Szczebak ◽

Jens Dyckmans ◽

Jan Kaiser ◽

Alina Marca ◽

Jürgen Augustin ◽

...

Keyword(s):

Oxygen Isotope ◽

Soil Water ◽

Isotope Effect ◽

Isotope Exchange ◽

Isotope Fractionation ◽

Isotope Effects ◽

N2o Production ◽

Oxygen Isotope Fractionation ◽

Oxygen Isotope Exchange ◽

Incubation Experiments

Abstract. The isotopic composition of soil-derived N2O can help differentiate between N2O production pathways and estimate the fraction of N2O reduced to N2. Until now, δ18O of N2O has been rarely used in the interpretation of N2O isotopic signatures because of the rather complex oxygen isotope fractionations during N2O production by denitrification. The latter process involves nitrate reduction mediated through the following three enzymes: nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR). Each step removes one oxygen atom as water (H2O), which gives rise to a branching isotope effect. Moreover, denitrification intermediates may partially or fully exchange oxygen isotopes with ambient water, which is associated with an exchange isotope effect. The main objective of this study was to decipher the mechanism of oxygen isotope fractionation during N2O production by soil denitrification and, in particular, to investigate the relationship between the extent of oxygen isotope exchange with soil water and the δ18O values of the produced N2O. In our soil incubation experiments Δ17O isotope tracing was applied for the first time to simultaneously determine the extent of oxygen isotope exchange and any associated oxygen isotope effect. We found that N2O formation in static anoxic incubation experiments was typically associated with oxygen isotope exchange close to 100 % and a stable difference between the 18O ∕ 16O ratio of soil water and the N2O product of δ18O(N2O ∕ H2O)  =  (17.5 ± 1.2) ‰. However, flow-through experiments gave lower oxygen isotope exchange down to 56 % and a higher δ18O(N2O ∕ H2O) of up to 37 ‰. The extent of isotope exchange and δ18O(N2O ∕ H2O) showed a significant correlation (R2 = 0.70, p < 0.00001). We hypothesize that this observation was due to the contribution of N2O from another production process, most probably fungal denitrification. An oxygen isotope fractionation model was used to test various scenarios with different magnitudes of branching isotope effects at different steps in the reduction process. The results suggest that during denitrification, isotope exchange occurs prior to isotope branching and that this exchange is mostly associated with the enzymatic nitrite reduction mediated by NIR. For bacterial denitrification, the branching isotope effect can be surprisingly low, about (0.0 ± 0.9) ‰, in contrast to fungal denitrification where higher values of up to 30 ‰ have been reported previously. This suggests that δ18O might be used as a tracer for differentiation between bacterial and fungal denitrification, due to their different magnitudes of branching isotope effects.

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The Meaning of Water Environment for Stilt Houses on the Musi Riverbanks, Palembang

Sriwijaya Journal of Environment ◽

10.22135/sje.2021.6.2.70-77 ◽

2021 ◽

Vol 6 (2) ◽

pp. 70-77

Author(s):

Ari Siswanto ◽

◽

Ira Kusumawaty ◽

Keyword(s):

Water Environment ◽

Road Construction ◽

The Road ◽

Lowland Area ◽

Tidal Swamps ◽

Agriculture Development ◽

Musi River

Water functions are very diverse for humans for daily needs such as drinking water, bathing, agriculture, development, aesthetics, and lower temperatures. Palembang is a lowland area dominated by wetlands, tidal swamps, and rivers. The types of houses on stilts on the banks of the Musi river are limas, Gudang, and Chinese stilt houses which are always associated with the water environment. The construction of roads replacing the role of rivers has realized people that the water environment has an important meaning for the house on stilts. The research objective was to explore the meaning of the water environment from various aspects for residents, stilt houses, and their environment. This research method is a case study with data collection through interviews, observation, measurements, and taking photos. Data and findings were analyzed and juxtaposed with images in the field. The road construction has eliminated part of the function of the river and influenced the change in orientation of the house on stilts. In conclusion, respect for the water environment including rivers has decreased, causing the quality of the river to decline, and the house on stilts cannot take advantage of the existence of the water environment optimally

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Electrical resistivity methods for landfill monitoring

Annals of Warsaw University of Life Sciences – SGGW Land Reclamation ◽

10.2478/sggw-2018-0015 ◽

2018 ◽

Vol 50 (2) ◽

pp. 183-193

Author(s):

Łukasz Zawadzki ◽

Dorota Wychowaniak ◽

Mariusz Lech

Keyword(s):

Electrical Resistivity ◽

Soil Water ◽

Water Flux ◽

Harmful Effect ◽

Water Environment ◽

Geophysical Methods ◽

Soil Samples ◽

Test Method ◽

Column Test ◽

Resistivity Measurements

Abstract Every single investment affects the natural environment, and that is why it is so important to eliminate nuisance it could cause. Extremely harmful effect on environment or human health could be expected from waste treatment facilities. One of the kinds of contamination which is a real threat to soil and water environment are leachates from landfills. They contain random chemical composition and can migrate from landfill through soil water flux leading to environmental pollution and degradation of groundwater. This paper focuses on the use of geophysical methods to assess migration of pollutants from the landfill through the subsoil. The laboratory tests of solute transport have been conducted on three soil samples from Łubna site to simulate the contamination flow. Migration of leachates through soil samples was controlled using the column test and electrical resistivity measurements which allow to com pare the results obtained with the standard column test method and electrical resistivity measurements. It leads to the conclusion that electrical resistivity methods for contamination transport monitoring in soil–water systems are suitable. Furthermore, field electrical resistivity tomography have been used for monitoring of the vertical sealing system in Łubna landfill.

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