The Effects of Plant-Microbe-Environment Interactions on Mineral Weathering Patterns in a Granular Basalt.

The importance of biota to soil formation and landscape development is widely recognized. As biotic complexity increases during early succession via colonization by soil microbes followed by vascular plants, effects of biota on mineral weathering and soil formation become more complex. Knowledge of the interactions among groups of organisms and environmental conditions will enable us to better understand landscape evolution.

Effect of gypsum on transport of IMX-104 constituents in overland flow under simulated rainfall.

Residue of energetic formulations, which is deposited on military training grounds following incomplete detonation, poses biotic hazards. This residue can be transported off-site, adsorb to soil clays and organic matter, transform or degrade, or taken up by plants and animals. Its harmful effects can be mitigated by localizing the energetics at the site of initial deposition using soil amendments and allowing them to bio- and photodegrade in situ.

The effects of physical form, moisture, humic acids, and mixtures on the photolysis of insensitive munitions compounds.

The explosive formulations IMX-101 and IMX-104 are replacing conventional explosives in munitions, making them safer to transport and handle. However, munitions manufacturing and military training can lead to the environmental release of constituent insensitive munitions compounds (IMCs) such as 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ). These IMCs absorb ultraviolet light and transform photochemically into products with potentially greater toxicity.

Movement of TNT and RDX from composition B detonation residues in solution and sediment during runoff.

Energetics used in military exercises can potentially contaminate ground and surface waters. This study was conducted to evaluate the movement of Composition B, a formulation that includes TNT (2,4,6-trinitrotoluene), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), in runoff. Mechanisms of transport we examined include movement of energetics dissolved in runoff, as particles and adsorbed to suspended sediment, and in infiltration.

Effects of drought and recovery on soil volatile organic compound fluxes in an experimental rainforest.

Drought can affect the capacity of soils to emit and consume biogenic volatile organic compounds (VOCs). Here we show the impact of prolonged drought followed by rewetting and recovery on soil VOC fluxes in an experimental rainforest. Under wet conditions the rainforest soil acts as a net VOC sink, in particular for isoprenoids, carbonyls and alcohols.

Transport of insensitive munitions constituents, NTO, DNAN, RDX, and HMX in runoff and sediment under simulated rainfall.

Insensitive munition constituents derived from residues of low order detonations and deposited on military training grounds present environmental risks. A series of rainfall simulation experiments on small soil plots examined the effect of precipitation, soil properties, and particle size on transport of IMX-104 munition components: NTO (3-nitro-1,2,4-triazol-5-one), DNAN (2,4-dinitroanisole), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and HMX (octahydro-1,3,5,7- tertranitro-1,3,5,7-tetrazocine). The primary pathways for rainfall driven transport were subsurface infiltration, off-site transport in solution, and transport in solid form including re-adsorption onto soil particles.

A laboratory rill study of IMX-104 transport in overland flow.

The deposition of explosive contaminants in particulate form onto the soil surface during low-order detonations can lead to ground and surface water contamination. The vertical fate and transport of insensitive munitions formulation IMX-104 through soil has been thoroughly studied, however the lateral transport of explosive particles on the surface is less known. The objective of this research was to understand the impact of overland flow on the transport of IMX-104 constituent compounds 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX).

Contrasting Community Assembly Forces Drive Microbial Structural and Potential Functional Responses to Precipitation in an Incipient Soil System.

Microbial communities in incipient soil systems serve as the only biotic force shaping landscape evolution. However, the underlying ecological forces shaping microbial community structure and function are inadequately understood. We used amplicon sequencing to determine microbial taxonomic assembly and metagenome sequencing to evaluate microbial functional assembly in incipient basaltic soil subjected to precipitation.

Elevated temperatures drive abiotic and biotic degradation of organic matter in a peat bog under oxic conditions.

Understanding the effects of elevated temperatures on soil organic matter (SOM) decomposition pathways in northern peatlands is central to predicting their fate under future warming. Peatlands role as carbon (C) sink is dependent on both anoxic conditions and low temperatures that limit SOM decomposition. Previous studies have shown that elevated temperatures due to climate change can disrupt peatland's C balance by enhancing SOM decomposition and increasing CO emissions.

Outdoor dissolution and photodegradation of insensitive munitions formulations IMX-101 and IMX-104: Photolytic transformation pathway and mechanism study.

New munition compounds have been developed to replace traditional explosives to prevent unintended detonations. However, insensitive munitions (IM) can leave large proportion of unexploded charge in the field, where it is subjected to photodegradation and dissolution in precipitation. The photolytic reactions occurring on the surfaces of IMX-101 and IMX-104 formulations and the subsequent fate of photolytic products in the environment were thoroughly investigated.

Soil microbial composition and carbon mineralization are associated with vegetation type and temperature regime in mesocosms of a semiarid ecosystem.

Transition from historic grasslands to woody plants in semiarid regions has led to questions about impacts on soil functioning, where microorganisms play a primary role. Understanding the relationship between microbes, plant diversity and soil functioning is relevant to assess such impacts. We evaluate the effect that plant type change in semiarid ecosystems has for microbial diversity and composition, and how this is related to carbon mineralization (CMIN) as a proxy for soil functioning.

Author Correction: Biotic soil-plant interaction processes explain most of hysteretic soil CO efflux response to temperature in cross-factorial mesocosm experiment.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Biotic soil-plant interaction processes explain most of hysteric soil CO efflux response to temperature in cross-factorial mesocosm experiment.

Ecosystem carbon flux partitioning is strongly influenced by poorly constrained soil CO efflux (F). Simple model applications (Arrhenius and Q) do not account for observed diel hysteresis between F and soil temperature. How this hysteresis emerges and how it will respond to variation in vegetation or soil moisture remains unknown.

Ecosystem-bedrock interaction changes nutrient compartmentalization during early oxidative weathering.

Ecosystem-bedrock interactions power the biogeochemical cycles of Earth's shallow crust, supporting life, stimulating substrate transformation, and spurring evolutionary innovation. While oxidative processes have dominated half of terrestrial history, the relative contribution of the biosphere and its chemical fingerprints on Earth's developing regolith are still poorly constrained. Here, we report results from a two-year incipient weathering experiment.

Photo-transformation of aqueous nitroguanidine and 3-nitro-1,2,4-triazol-5-one: Emerging munitions compounds.

Two major components of insensitive munition formulations, nitroguanidine (NQ) and 3-nitro-1,2,4-triazol-5-one (NTO), are highly water soluble and therefore likely to photo-transform while in solution in the environment. The ecotoxicities of NQ and NTO solutions are known to increase with UV exposure, but a detailed accounting of aqueous degradation rates, products, and pathways under different exposure wavelengths is currently lacking. Here, we irradiated aqueous solutions of NQ and NTO over a 32-h period at three ultraviolet wavelengths (254 nm, 300 nm, and 350 nm) and analyzed their degradation rates and transformation products.

Dissolution and transport of insensitive munitions formulations IMX-101 and IMX-104 in saturated soil columns.

Military training exercises can result in deposition of energetic residues on range soils, which ultimately can contaminate groundwater with munitions constituents. Column experiments followed by HYDRUS-1D modeling were conducted to evaluate dissolution and transport of energetic constituents from the new insensitive munitions (IM) formulations IMX-101, a mixture of 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), and 2, 4-dinitroanisole (DNAN), and IMX-104, a mixture of NTO, 1,3,5-hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and DNAN. NTO and DNAN are emerging contaminants associated with the development of insensitive munitions as replacements for traditional munitions.

Batch soil adsorption and column transport studies of 2,4-dinitroanisole (DNAN) in soils.

The explosive 2,4,6-trinitrotoluene (TNT) is currently a main ingredient in munitions; however the compound has failed to meet the new sensitivity requirements. The replacement compound being tested is 2,4-dinitroanisole (DNAN). DNAN is less sensitive to shock, high temperatures, and has good detonation characteristics.

Ecosystem Composition Controls the Fate of Rare Earth Elements during Incipient Soil Genesis.

The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE mass-partitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza.

Column transport studies of 3-nitro-1,2,4-triazol-5-one (NTO) in soils.

Development of the new, insensitive, energetic compound, NTO (3-nitro-1,2,4-triazol-5-one), creates need for the data on NTO's fate and transport to predict its behavior in the environment and potential for groundwater contamination. To measure the transport of NTO in soils, we conducted miscible-displacement experiments under steady state and interrupted flow conditions using eight soils having varying physical and geochemical properties. The breakthrough curve (BTC) data were analyzed using temporal moment analysis and simulated using HYDRUS-1D to determine transport parameters and better understand the mechanisms of sorption and transformation.

Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations.

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled Earth-system processes. Such knowledge is imperative in improving predictions of hydro-biogeochemical cycles, especially under climate change scenarios. We present an experimental method, designed to capture sub-surface heterogeneity of an initially homogeneous soil system.

Adsorption and attenuation behavior of 3-nitro-1,2,4-triazol-5-one (NTO) in eleven soils.

NTO (3-nitro-1,2,4-triazol-5-one) is one of the new explosive compounds used in insensitive munitions (IM) developed to replace traditional explosives, TNT and RDX. Data on NTO fate and transport is needed to determine its environmental behavior and potential for groundwater contamination. We conducted a series of kinetic and equilibrium batch experiments to characterize the fate of NTO in soils and the effect of soil geochemical properties on NTO-soil interactions.

Outdoor dissolution of detonation residues of three insensitive munitions (IM) formulations.

We seek to understand the environmental fate of three new insensitive munitions, explosive formulations developed to reduce the incidence of unintended detonations. To this end, we measured the size distribution of residues from low order detonations of IMX 101, IMX 104, and PAX 21-filled munitions and are studying how these three formulations weather and dissolve outdoors. The largest pieces collected from the detonations were centimeter-sized and we studied 12 of these in the outdoors test.

Dissolution of three insensitive munitions formulations.

The US military fires live munitions during training. To save soldiers lives both during training and war, the military is developing insensitive munitions (IM) that minimize unintentional detonations. Some of the compounds in the IM formulation are, however, very soluble in water, raising environmental concerns about their fate and transport.