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Dissolved organic matter (DOM) is known to leach to surface waters after clear-cut harvest in boreal peatland, but the chemical properties and bioavailability of leached DOM has remained largely unknown. The properties of DOM in peat seemed to be controlled by the aerobic–anaerobic conditions of the peat in a complicated manner.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.08.0155. doi:https://doi.org/10.2136/vzj2013.08.0155

System-specific markers are needed to trace dissolved organic matter (DOM). We examined DOM from four different ecosystems using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Ecosystem-specific molecular characteristics exist, and a strategic search for specific markers is necessary. Our data indicate pH and vegetation influence. We suggest tannin molecular formulae as possible markers for forest systems. Ubiquitously detected formulae match those of carboxyl-rich alicyclic molecules (CRAM), but distinction from lignin is not possible without structure elucidation.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.09.0162. doi:https://doi.org/10.2136/vzj2013.09.0162

Soil solution DOC concentrations were measured in 87 contrasting agricultural topsoils. The DOC concentrations are largely affected by drying–rewetting of the soils. In freshly sampled soils, DOC concentrations correlate poorly to physicochemical properties of the soil, likely due to biological processes involved.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.09.0167. doi:https://doi.org/10.2136/vzj2013.09.0167

The fluxes of dissolved organic and inorganic C were estimated from simulated soil water fluxes and measured C concentration in the soil solution. For the eroded hummocky ground moraine landscape, the balance ranged from leaching to a bottom influx in local depressions.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.10.0173. doi:https://doi.org/10.2136/vzj2013.10.0173

The effect of organic matter sorption and microbial activity on sand particle wettability was investigated. Wettability generally decreased after sorption of organic matter. Low C/N ratios suggest that reduction in wettability was also caused by microbial activity. Formation of biogeochemical interfaces can strongly change original particle wettability.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.10.0175. doi:https://doi.org/10.2136/vzj2013.10.0175

Natural organic matter is subjected to kinetic exchange on Al and Fe oxy(hydroxide) coated sand surfaces during laboratory experiments.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.10.0179. doi:https://doi.org/10.2136/vzj2013.10.0179

Dissolved organic matter (DOM) from organic layers is the main source of organic matter entering forest mineral soils. Increasing throughfall—one possible consequence of climate change—did not affect concentrations and quality of DOM below forest floors, suggesting enhanced exports to mineral soils with increasing precipitation.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.10.0180. doi:https://doi.org/10.2136/vzj2013.10.0180

An extensive sampling study identified the transport pathways of dissolved organic C to the surface water in contrasting catchments. An end-member mixing analysis revealed that the transport pathways of dissolved organic C can differ seasonally and highly depend on the degree of saturation of the vadose zone.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2013.11.0199. doi:https://doi.org/10.2136/vzj2013.11.0199

The dissolved organic matter (DOM) in wastewater streams provides C and nutrients, thereby influencing the priming effect (PE) of soil organic matter. The DOM-induced changes in the PE, which depend on the nature of both the DOM source and soil organic matter, influence C sequestration in soils.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2014.01.0002. doi:https://doi.org/10.2136/vzj2014.01.0002

The study characterizes bound P on fine colloids and nanoparticles in stream water through asymmetric flow field flow fractionation coupled online to detectors for size-resolved elemental detection. The developed methodology enables tracing both the inputs and source regions of colloidal fractions containing P, Al, Fe, and C for the first time.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2014.01.0005. doi:https://doi.org/10.2136/vzj2014.01.0005

Adsorption of tested heavy metals on Egyptian soils was large in all situations tested and follows the order: Cu >> Ni ≈ Zn. Copper was influenced by the timing of dissolved organic matter addition more than Ni and Zn. Specific binding mechanisms (inner-sphere complexes) dominated the affinity of Cu for the solid phase, whereas nonspecific electrostatic interactions were the dominant mechanism for Ni and Zn.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2014.01.0009. doi:https://doi.org/10.2136/vzj2014.01.0009

Spatio-temporal changes in the molecular composition of soil dissolved organic matter were investigated in a lowland catchment. The distribution of molecular markers was correlated to bulk-scale descriptors. The proportions of microbial plant-derived markers varied both vertically and temporally in line with the shift in the geometry of flow paths.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2014.02.0015. doi:https://doi.org/10.2136/vzj2014.02.0015

Special Section: Dissolved Organic Matter in Soil

The guest editors introduce the contributions to the special section, Dissolved Organic Matter in Soil, with a focus on the three main directions in this complex and growing research effort.

Vadose Zone Journal July 01, 2014, Vol.13, vzj2014.05.0051. doi:https://doi.org/10.2136/vzj2014.05.0051
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