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In recent years, natural deep eutectic solvents have been favored greatly due to their environment friendly, mild biological toxicity and simple biodegradability. NADESs gradually applied for the extracting bioactive compounds from natural products efficiently. In this study, 20 natural deep eutectic solvents were prepared and their physical and chemical properties were tested. The ultrasonic-assisted extraction method was used to extract flavonoids from Trollius ledebouri and HPLC-UV was applied to examine two main bioactive flavonoids (orientin and vitexin). Compared with traditional solvents (water and 60% ethanol solution), natural deep eutectic solvents composed by L(-)-proline and levulinic acid (molar ratio 1:2) shows a super extraction efficiency. On this basis, the response surface method was used to optimize the extraction temperature, extraction time, water contents and solid-liquid ratio. As a consequence, the extraction temperature 60℃, extraction time 18 min, water content 14% (v/v) and the solid-liquid ratio 48 mL⋅g-1 were chose as the best extraction process. This study shows that natural deep eutectic solvents can effectively extract flavonoids from Trollius ledebouri, laying a foundation for the further application of natural deep eutectic solvents to extract bioactive compounds from natural products. This article is protected by copyright. All rights reserved.

By dissolving copper chloride in [Bmim]Cl (1-butyl-3-methylimidazolium chloride), chloride ions can coordinate with copper ions and form [CuCl

In the last decade, natural deep eutectic solvents (NADESs) have gained more and more attention due to their green, convenient preparation, low toxicity and biodegradability. It is widely used in various fields, especially in the extraction of active components from plants, formed by the combination of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs) at a certain condition. In this article, six preparation methods of NADESs were summarized and the interactions that occur in the eutectic behavior of NADES including hydrogen bonding, electrostatic interaction and van der Waals force were also reviewed. What is more, its significant extraction capacity on flavonoids, phenols, alkaloids and plant pigments endows its extensive applications in the extraction of active components from medicinal plants. Extraction factors including solvents properties (viscosity, carbon chain length, number of hydroxyl groups), extraction condition (water content, extraction temperature, extraction time, solid-liquid ratio), extraction method and recycling method were discussed. In addition, NADESs can also be combined with other technologies, like molecular imprinting, monolithic column, to achieve efficient and specific extraction of active ingredients. Further systematic studies on the biodegradability and biotoxicity are put forward to be urgent.

Structural heterogeneity is a common phenomenon in cellulose hydrogel fabricated from ionic liquid. In this work, we characterized cellulose hydrogel wire by Fourier transform infrared spectroscopy (FTIR) image system and found its interesting core-shell structure. By pixel spectra analysis, we explored their distinctive hydrogen bond network in core and shell regions. To unveil the formation of heterogeneous core-shell structure, we tracked the cellulose regeneration procedure in situ by time-dependent attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Inspired by an interesting red followed by blue band position shift, namely "V-shape" shift, we proposed a tri-step model of cellulose regeneration in favor of quantum calculation. The tri-step model can explain the formation of the heterogeneous core-shell structure.

This work presents a new method to fabricate cellulose gels with micrometer size channels that offer ultra-permeability. A non-ionic surfactant was key to the formation of the macro channels. We studied the chemical microstructure of the [Bmim]Cl (1‑butyl‑3‑methylimmidozolium chloride)-cellulose-surfactant mixtures by Fourier transform infrared spectroscopy (FTIR) imaging system. We then questioned the soft template theory and confirmed our surfactant-induced and diffusion-driven hypothesis to explain the formation of the macro channels. We also found that the microstructure of the gels was impacted by the surfactant, according to nitrogen physisorption, X-ray diffraction, nuclear magnetic resonance, and scanning electron microscopy results. Time-dependent attenuated total reflection-FTIR (ATR-FTIR) was used to monitor the phase separation of the ionic liquid and cellulose in situ during the sol-gel transition. A two-step model of cellulose regeneration was thus proposed. Our study offers a strategy to fabricate hierarchical porous materials with macro channels and can increase the understanding of cellulose regeneration mechanism from ionic liquids.

Vast amounts of soil organic matter (SOM) have been preserved in arctic soils over millennia time scales due to the limiting effects of cold and wet environments on decomposer activity. With the increase in high latitude warming due to climate change, the potential decomposability of this SOM needs to be assessed. In this study, we investigated the capability of mid infrared (MIR) spectroscopy to quickly predict soil carbon and nitrogen concentrations and carbon (C) mineralized during short-term incubations of tundra soils. Active layer and upper permafrost soils collected from four tundra sites on the North Slope of Alaska were incubated at 1, 4, 8 and 16 °C for 60 days. All incubated soils were scanned to obtain the MIR spectra and analyzed for total organic carbon (TOC) and total nitrogen (TN) concentrations, and salt-extractable organic matter carbon (SEOM). Partial least square regression (PLSR) models, constructed using the MIR spectral data for all soils, were excellent predictors of soil TOC and TN concentrations and good predictors of mineralized C for these tundra soils. We explored whether we could improve the prediction of mineralized C by splitting the soils into the groups defined by the influential factors and thresholds identified in a principal components analysis: (1) TOC >10%, (2) TOC 0.6%, (5) acidic tundra, and (6) non-acidic tundra. The best PLSR mineralization models were found for soils with TOC

Bamboo powder and its dissolution process in ionic liquids were analyzed according to Fourier Transform Infrared Spectroscopy (FT-IR) coupled with two-dimensional correlation spectroscopy and chemometrics. Second derivative spectroscopy was applied to enhance the spectra resolution, obtaining more molecular vibration information. After executing the principal component analysis (PCA) on ATR-FTIR spectra of undissolved bamboo powder residue, we obtained a three-staged dissolution process model. In addition, the conclusion that cellulose/hemicellulose dissolving prior to lignin was summarized through the PCA loading spectrum. Point-line moving window two dimensional correlation spectroscopy (PL-MW2DCOS) furtherly unveiled the dissolution details. This work provided us a clear dissolution process of biomass using a rapid, label-free and easy-operation method.

Ionic liquid is a promising cellulose solvent in the future, while moisture absorption hinders the cellulose dissolution. In the present work, we in situ monitored the procedure of moisture absorption of three 1-butyl-3-methylimidazolium cation based ionic liquids with variation of halogen anions. According to the peak position shifts across the moisture absorption process, we analyzed the structure variation of ionic liquids during the process. Besides, we analyzed the hydrogen bond interaction between halogen anion and imidazolium cation C Hs, including ring C Hs and side alkyl chain C Hs, based on infrared absorption bands position shifts of the three ionic liquids. In addition, two dimensional correlation spectroscopy was applied to enhance the spectra resolution, unveiling the transformation of ionic liquids after absorbing moisture for the split of peak attributed to ring C2 H stretching. In summary, we provide reliable evidence to analyze the structure variation of ionic liquid during moisture absorption process and hydrogen bond interaction of halogen anion with imidazolium cation ring/side alkyl C Hs from the perspective of infrared spectroscopy.

In this work, cellulose nanoparticles regenerated by water, methanol, ethanol and n-propanol as the anti-solvents from ionic liquid solution were studied systematically. Crystallinity and enthalpy in cellulose degradation of the regenerated cellulose decreased in the order water > methanol > ethanol > n-propanol. Nevertheless, the thermal stability of the regenerated cellulose showed an opposite trend. In addition, morphology of regenerated cellulose changed sharply with the variation of anti-solvents. Moreover, we introduced Kamlet–Taft parameters of anti-solvents to analyze the crystallinity, enthalpy in cellulose degradation and thermal stability variation of regenerated cellulose. Hydrogen bond acidity and basicity of anti-solvent definitely drove the property variation of regenerated cellulose nanoparticles to opposite directions. Furtherly, we proposed two competitive cellulose regeneration routes, providing a reasonable explanation to the crystallinity, enthalpy in cellulose degradation and thermal stability variation of regenerated cellulose nanoparticles. Our work successfully demonstrate that H-bond acidity/basicity of anti-solvent could tune the property of regenerated cellulose nanoparticles, unveiling the competitive routes of cellulose regeneration.

We investigated the influence of site characteristics and soil properties on the chemical composition of organic matter in soils collected from a latitudinal transect across northern cold-region through analysis of diffuse reflectance Fourier transform mid infrared (DRIFT) spectra of bulk soils. The study included 119 soil samples collected from 28 sites including tundra, boreal forest, grassland, and coastal rainforest ecosystems. Organic, mineral, and cryoturbated soil horizons, both seasonally and perennially frozen, representing a variety of depths and edaphic conditions were examined. The amount and chemical composition of organic matter, as well as site and soil properties, exerted a strong influence on the DRIFT spectra. The spectra were highly sensitive to the extent of organic matter decomposition, enabling the ordination of organic (Oi, Oe and Oa) horizons. Differences in absorbance intensity for several spectral bands indicated that Oi horizons contained greater abundance of relatively fresh residues, phenolic-OH compounds, aliphatic compounds, and carbohydrates. In contrast, Oa horizons had a greater presence of amide groups, aromatics, CC bonds, carboxylates and carboxylic acids. Another significant factor differentiating these horizons was the incorporation of clays and silicates into the Oa horizons. Calculated ratios of characteristic spectral bands showed a clear trend of increasing decomposition from Oi to Oe to Oa. The DRIFT spectra were related to many site/soil attributes including land cover type, parent material, and associated factors, such as permafrost presence/absence, drainage class, horizon depth, bulk density, cation exchange capacity, and pH. A single DRIFT spectral band was identified that might be used in future studies to quickly estimate the organic carbon, total nitrogen, and carbon:nitrogen ratios of northern soils. Our results demonstrate that the information contained in DRIFT spectra of soil integrates the quantity and chemical composition of soil organic matter with soil properties and highlights the potential for using this information to assess the degradation state of organic matter stored in northern cold-region soils.

Soil color is one of the most useful soil properties for assessing and monitoring soil health. Here we present results of tests of a new soil color app for mobile phones. Various smartphone cameras (SPCs) were tested under sunny and cloudy conditions and compared with visual estimates using Munsell color charts (MCCs). The measured and estimated soil colors were then compared with the “true” colors determined using a spectrophotometer. The results indicated that soil color determinations based on SPC measurements under both sunny and cloudy conditions were as good as those obtained using the MCCs. The accuracy of the SPC measurements was affected by the natural illumination conditions, with higher accuracy in the sun than where clouds were present. Our results also indicated that the SPC measurements completed in the sun provide higher precision (lower variance) than SPC measurements completed under cloudy conditions or estimates based on MCCs. These results suggest that mobile-device cameras have great potential to allow non–soil scientists, and others lacking access to color charts, to determine soil color.

Representing land surface spatial heterogeneity when designing observation networks is a critical scientific challenge. Here, we present a geospatial approach that utilizes the multivariate spatial heterogeneity of soil-forming factors — namely climate, topography, land cover types, and surficial geology — to identify observation sites to improve soil organic carbon (SOC) stock estimates across the State of Alaska, USA. Standard deviations in existing SOC samples indicated that 657, 870, and 906 randomly distributed pedons would be required to quantify the average SOC stocks for 0-1 m, 0-2 m, and whole-profile depths, respectively, at a confidence interval of 5 kg m-2. Using the spatial correlation range of existing SOC samples, we identified that 309, 446, and 484 new observation sites are needed to estimate current SOC stocks to 1-m, 2-m, and whole-profile depths, respectively. We also investigated whether the identified sites might change under future climate by using eight decadal (2020–2099) projections of precipitation, temperature, and length of growing season for three representative concentration pathway (RCP 4.5, 6.0, and 8.5) scenarios of the Intergovernmental Panel on Climate Change. These analyses determined that 12 to 41 additional sites (906 + 12 to 41; depending upon the emission scenarios) would be needed to capture the impact of future climate on Alaskan whole-profile SOC stocks by 2100. The identified observation sites represent spatially distributed locations across Alaska that captures the multivariate heterogeneity of soil-forming factors under current and future climatic conditions. This information is needed for designing monitoring networks and benchmarking of Earth System Model results.

Cellulose, regarded as a potential sustainable resource for the future, can dissolve and regenerate in ionic liquids (ILs) upon adding anti-solvents. Improving the regeneration conditions, like changing the anti-solvents, could optimize the properties of regenerated cellulose-based materials. Previous studies pointed out that the diffusion processes of anti-solvents plays a significant role in the determination of the properties of regenerated cellulose fibers/films. However, the cellulose regeneration mechanism from ILs has not been clarified. Here, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was introduced to monitor the molecular diffusion processes of four anti-solvents in situ. The crystallinity of regenerated cellulose showed a negative correlation with respect to the diffusion coefficient. In addition, the interaction of imidazolium cations and anti-solvent molecules was evaluated from the peak shifting during the diffusion processes. Furthermore, Taft and Kamlet scales were used to quantify the interaction between IL cations/anions and anti-solvent molecules, eliciting distinct cellulose regeneration paths in different anti-solvents.

The high viscosity of ionic liquids, even at relatively high temperatures, can greatly affect the production of cellulose fibers through the wet-spinning process. The high viscosity mainly by due to the hydrogen bond interaction between the cations and anions of ionic liquids. It is possible to reduce the viscosity by modulating the hydrogen bond interaction. In the present work, copper chloride (CuCl2) was dissolved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl)-cellulose solution, followed by the formation of a complex with the chloride anions by converting it to [CuCl4]2- anion. Through this strategy, the extrusion velocity of the solution improved, and the produced fibers obtained smoother surfaces and shrunken diameters.

We investigated several key limiting factors that control alpine tundra productivity by developing an ecosystem biogeochemistry model. The model simulates the coupled cycling of carbon (C), nitrogen (N), and phosphorus (P) and their interactions with gross primary production (GPP). It was parameterized with field observations from an alpine dry meadow ecosystem using a global optimization strategy to estimate the unknown parameters. The model, along with the estimated parameters, was first validated against independent data and then used to examine the environmental controls over plant productivity. Our results show that air temperature is the strongest limiting factor to GPP in the early growing season, N availability becomes important during the middle portion of the growing season, and soil moisture is the strongest limiting factors by late in the growing season. Overall, the controls over GPP during the growing season, from strongest to weakest, are soil moisture content, air temperature, N availability, and P availability. This simulation provides testable predictions of the shifting nature of physical and nutrient limitations on plant growth. The model also indicates that changing environmental conditions in the alpine will likely lead to changes in productivity. For example, warming eliminates the control of P availability on GPP and makes N availability surpass air temperature to become the second strongest limiting factor. In contrast, an increase in atmospheric nutrient deposition eliminates the control of N availability and enhances the importance of P availability. These analyses provide a quantitative and conceptual framework that can be used to test predictions and refine ecological analyses at this long-term ecological research site.

Savannas cover 60% of the African continent and play an important role in the global carbon (C) emissions from fire and land use. To better characterize the biophysical controls over soil respiration in these settings, half-hourly observations of volumetric soil–water content, temperature, and the concentration of carbon dioxide (CO 2 ) at different soil depths were continually measured from 2005 to 2007 under trees (“sub-canopy”) and between trees (“inter-canopy”) in a savanna vegetation near Skukuza, Kruger National Park, South Africa. The measured soil climate and CO 2 concentration data were assimilated into a process-based model that estimates the CO 2 production and flux with coupled dynamics of dissolved organic C (DOC) and microbial biomass C. Our results show that temporal and spatial variations in CO 2 flux were strongly influenced by precipitation and vegetation cover, with two times greater CO 2 flux in the sub-canopy plots (∼2421 g CO 2 m −2 yr −1 ) than in the inter-canopy plots (∼1290 g CO 2 m −2 yr −1 ). Precipitation influenced soil respiration by changing soil temperature and moisture; however, our modeling analysis suggests that the pulsed response of soil respiration to precipitation events (known as “Birch effect”) is a key control on soil fluxes at this site. At this site, “Birch effect” contributed to approximately 50% and 65% of heterotrophic respiration or 20% and 39% of soil respiration in the sub-canopy and inter-canopy plots, respectively. These results suggest that pulsed response of respiration to precipitation events is an important component of the C cycle of savannas and should be considered in both measurement and modeling studies of carbon exchange in similar ecosystems.

Subsurface moisture content is one of the critical factors that control the thermal dynamics of embankments. However, information on the subsurface moisture movement and distribution in embankments is still limited. To better understand the coupled water and heat transport within embankments, subsurface temperature and moisture of an asphalt pavement highway were extensively measured from 2009 to 2011. Collected data indicate that pure heat conduction is the overall main mechanism of heat transport in the embankment and heat convection plays a relatively unimportant role in heat transport. The results also indicate that subsurface moisture and temperature dynamics in the asphalt layer is strongly related to the rainfall events, while the subsurface moisture content below the road base course maintains relatively constant. Rainfall in summer leads to rapid cooling of the subsurface soil. Our results suggest that frequent and small rainfall events favour the thermal stability of the embankment due to the lo...

The large amount of soil carbon in boreal forest ecosystems has the potential to influence the climate system if released in large quantities in response to warming. Thus, there is a need to better understand and represent the environmental sensitivity of soil carbon decomposition. Most soil carbon decomposition models rely on empirical relationships omitting key biogeochemical mechanisms and their response to climate change is highly uncertain. In this study, we developed a multi-layer microbial explicit soil decomposition model framework for boreal forest ecosystems. A thorough sensitivity analysis was conducted to identify dominating biogeochemical processes and to highlight structural limitations. Our results indicate that substrate availability (limited by soil water diffusion and substrate quality) is likely to be a major constraint on soil decomposition in the fibrous horizon (40–60% of soil organic carbon (SOC) pool size variation), while energy limited microbial activity in the amorphous horizon exerts a predominant control on soil decomposition (>70% of SOC pool size variation). Elevated temperature alleviated the energy constraint of microbial activity most notably in amorphous soils, whereas moisture only exhibited a marginal effect on dissolved substrate supply and microbial activity. Our study highlights the different decomposition properties and underlying mechanisms of soil dynamics between fibrous and amorphous soil horizons. Soil decomposition models should consider explicitly representing different boreal soil horizons and soil–microbial interactions to better characterize biogeochemical processes in boreal forest ecosystems. A more comprehensive representation of critical biogeochemical mechanisms of soil moisture effects may be required to improve the performance of the soil model we analyzed in this study.

Peatlands store vast amounts of soil carbon and are significant sources of greenhouse gases, including carbon dioxide (CO2) and methane (CH4) emissions. The traditional approach in biogeochemical model simulations of peatland emissions is to simply divide the soil domain into an aerobic zone above and an anaerobic zone below the water table (WT) and then calculate CO2 and CH4 emissions based on the assumed properties of these two discrete zones. However, there are major potential drawbacks associated with the traditional WT-based approach, because aerobic or anaerobic environments are ultimately determined by oxygen (O2) concentration rather than water content directly. Variations in O2 content above and below the WT can be large and thus may play an important role in partitioning of carbon fluxes between CO2 and CH4. In this paper, we propose an oxygen-based approach, which simulates the vertical and radial components of O2 movement and consumption through the soil aerobic and anaerobic environments. We then use both our oxygen-based and the traditional WT-based approaches to simulate CO2 and CH4 emissions from an Alaskan fen peatland. The results of model calibration and validation suggest that our physically realistic approach (i.e., oxygen-based approach) cause less biases on the simulated flux of CO2 and CH4. The results of model simulations also suggest that the traditional WT-based approach might substantially under-estimate CH4 emissions and over-estimate CO2 emissions from the fen due to the presence of anaerobic zones in unsaturated soil. Our oxygen-based approach can be easily incorporated into existing ecosystem or earth system models but will require additional validation with more extensive field observations to be implemented within biogeochemical models to improve simulations of soil C fluxes at regional or global scale.

A new soil moisture content sensor coupled with a new matric potential sensor that can operate in the subfreezing environment was used to measure the moisture content and soil matric potential dynamics of Qinghai-Tibetan silty clay. Combined with nuclear magnetic resonance (NMR) technique and thermal resistor temperature probe, the characteristics of unfrozen water content and soil matric potential, and their relationships with temperature were analyzed. The results show that initial water content has an impact on the freezing point and unfrozen water content. The decrease in the initial water content results in a depression in the freezing point. The Qinghai-Tibetan silty clay has more similar unfrozen water content characteristic to clay than to silt. There is approximately 3% of unfrozen water content retained when the soil temperature drops to −15°C. The change of soil matric potential with temperature is similar to that of the unfrozen water content. The matric potential value of the saturated silty clay is approximately −200 kPa when the soil temperature drops to −20°C. The measured matric potentials are significantly lower than the calculated theoretical values based on the freezing point depression. Moisture migration experiment indicates that soil matric potential controls the direction of moisture movement and moisture redistribution (including ice and liquid water) during the soil freezing.

Sulfonamides (SAs) are one of the broadly used antibiotics in domestic animal operations and have a notable potential of entering the environment through animal manure management practices. In this study, sulfamethazine (SMZ) was used as a prototype to study the sorption, fate, and transport of SAs in soil–water systems using batch and miscible-displacement experiments. Sulfamethazine was degraded to a polar metabolite (PM). The batch experiments indicated that the linear sorption partitioning coefficient (K d ) values for the PM ranged from 7.5 to 206.2 L kg−1. Strong relationships between the sorption of PM and various soil fractions and organic matter were also observed. The miscible-displacement experiments showed that 33–70% of SMZ was degraded within 6 h during transport in the soil columns. Also, 69–99.7% of SMZ and PM were recovered in the effluents suggesting their high mobility. Also, the simultaneous degradation, sorption, and transport of SMZ and PM were described using a two-site chemical nonequilibrium fate and transport model, using the K d values obtained from the batch experiments. The parameters of this model were uniquely estimated using a global optimization strategy, the stochastic ranking evolutionary strategy.

The movement of dissolved organic carbon (DOC) throughboreal ecosystems has drawn increased attention because of its poten-tial impact on the feedback of OC stocks to global environmentalchange in this region. Few models of boreal DOC exist. Herewe presenta one-dimensional modelwith simultaneous production, decomposition,sorption/desorption, and transport of DOC to describe the behavior ofDOC in the OC layers above the mineral soils. The field-observed con-centration profiles of DOC in two moderately well-drained black spruceforest sites (one with permafrost and one without permafrost), coupledwith hourly measured soil temperature and moisture, were used to in-versely estimate the unknown parameters associated with the sorption/desorption kinetics using a global optimization strategy. The model,along with the estimated parameters, reasonably reproduces the con-centration profiles of DOC and highlights some important potentialcontrols over DOC production and cycling in boreal settings. Thevaluesof estimated parameters suggest that humic OC has a larger potentialproduction capacity for DOC than fine OC, and most of the DOCproduced from fine OC was associated with instantaneous sorption/desorption whereas most of the DOC produced from humic OC wasassociated with time-dependent sorption/desorption. The simulatedDOC efflux at the bottom of soil OC layers was highly dependent onthe component and structure of the OC layers. The DOC efflux wascontrolled by advection at the site with no humic OC and moist con-ditions and controlled by diffusion at the sitewith the presence of humicOC and dry conditions.Key words: Black spruce, boreal, carbon, advection, diffusion,inversion.(Soil Science 2010;175: 223Y232)

It is a significant challenge to reliably identify fate and transport parameters for solutes that simultaneously undergo multiple and complex processes. Evolutionary optimization techniques allow process parameters to be identified for complicated problems. One evolutionary optimization technique, the stochastic ranking evolutionary strategy (SRES), was used in this study to find the global or near-global optimal parameters for two solute breakthrough curve experiments. The uncertainties of the estimated parameters were assessed using a nonparametric bootstrap resample method. The two miscible-displacement cases considered were (i) a simulated experiment of a solute undergoing transformation and (ii) an actual experiment of trichloroethylene undergoing simultaneous nonequilibrium transport and transformation. In both cases, multiple breakthrough curves were produced from a parent solute and its metabolites, and the SRES was used with an appropriate convective–dispersive model to inversely identify the model parameters. The SRES inverse method provided an excellent model fit to the experimental data, and the model parameter estimates had minimal uncertainty even when 5% experimental error was introduced.

Testosterone is an endocrine disruptor that is released into the environment from natural and anthropogenic sources. The objective of this study was to achieve a better understanding of the complex fate and transport of this labile compound in an undisturbed agricultural soil (a Hamar Sandy, mixed, frigid typic Endoaquolls). This was done by using batch and miscible-displacement experiments, and by using a chemical nonequilibrium transport model. Sorption and transformations of testosterone were discerned using various batch experiments. The batch experiments indicated that the aqueous phase concentrations of testosterone rapidly decreased from 12 to 15% of the initial aqueous concentration within 5 h, but then gradually increased through time and reached 28 to 29% of the initial aqueous concentration at 168 h. The increase in the aqueous concentration was explained by mineralization and biodegradation. Multiple first-order models were used to describe batch experiments where simultaneous degradation and sorption processes occurred. An evolutionary global optimization strategy was used to estimate the process parameters from these batch experiments and there was high confidence in these parameter estimates. The result of column experiments also showed that 23.4% of testosterone was mineralized to CO 2 as it transported through the column. Combustion analyses of extracted soil from inside the columns showed that most of the 14 C retained in the column (69-74%) was sorbed in the top 5 cm. The independently determined batch parameters were incorporated into a chemical nonequilibrium transport model, which provided an excellent description of the hormone in the eftluent, and vertical redistribution in the soil column.

Soil organic carbon (SOC) plays an important role in the global carbon cycle. However, it remains largely unknown how plant litter inputs impact magnitude, composition and source configuration of the SOC stocks over long term through microbial catabolism and anabolism, mostly due to uncoupled research on litter decomposition and SOC formation. This limits our ability to predict soil system responses to changes in land-use and climate. Here, we examine how microbes act as a valve controlling carbon sequestrated from plant litters versus released to the atmosphere in natural ecosystems amended with plant litters varying in quantity and quality. We find that litter quality – not quantity – regulates long-term SOC dynamics under different plausible scenarios. Long-term changes in bulk SOC stock occur only when the quality of carbon inputs causes asynchronous change in a microbial physiological trait, defined as “microbial biosynthesis acceleration” (MBA). This is the first theoretical demonstration that the response of the SOC stocks to litter inputs is critically determined by the microbial physiology. Our work suggests that total SOC at an equilibrium state may be an intrinsic property of a given ecosystem, which ultimately is controlled by the asynchronous MBA between microbial functional groups.

The most toxic dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2378-TCDD), and obtaining comprehensive experimental data for this compound is challenging. However, several nontoxic isomers of 2378-TCDD exist, and can provide significant experimental evidence about this highly toxic dioxin. The goal of this study was to obtain experimental evidence for the fate and transport of 2378-TCDD in natural soils using its nontoxic isomers, 1,2,7,8-tetrachlorodibenzo-p-dioxin (1278-TCDD), 1,3,7,8-tetrachlorodibenzo-p-dioxin (1378-TCDD), and 1,4,7,8-tetrachlorodibenzo-p-dioxin (1478-TCDD). Batch sorption and miscible-displacement experiments, in various soils, were done using [4-(14)C]-radiolabeled TCDDs, while metabolism of these compounds was monitored. The results from the batch experiments indicated a high sorption affinity of all the TCDD isomers to soils and a strong correlation to organic matter (OM) content. 1278-TCDD, 1378-TCDD and 1478-TCDD (TCDDs) were more tightly bound to the soil with high OM than to the soil with low OM; however, it took a longer contact time to approach sorption equilibrium of TCDDs in the soil with high OM. Miscible-displacement breakthrough curves indicated chemical nonequilibrium transport, where there was a rate-limited or kinetic sorption that was likely caused by OM. Combustion analyses of extracted soil from the soil columns showed that most TCDDs were adsorbed in the top 1-5 cm of the column. These column combustion results also showed that sorption was correlated to specific surface and soil depth, which suggested the possibility of colloidal transport.

The large magnitudes of soil carbon stocks provide potentially large feedbacks to climate changes, highlighting the need to better understand and represent the environmental sensitivity of soil carbon decomposition. Most soil carbon decomposition models rely on empirical relationships omitting key biogeochemical mechanisms and their response to climate change is highly uncertain. In this study, we developed a multi-layer mechanistically based soil decomposition model framework for boreal forest ecosystems. A global sensitivity analysis was conducted to identify dominating biogeochemical processes and to highlight structural limitations. Our results indicate that substrate availability (limited by soil water diffusion and substrate quality) is likely to be a major constraint on soil decomposition in the fibrous horizon (40–60% of SOC pool size variation), while energy limited microbial activity in the amorphous horizon exerts a predominant control on soil decomposition (>70% of SOC pool size variation). Elevated temperature alleviated the energy constraint of microbial activity most notably in amorphous soils; whereas moisture only exhibited a marginal effect on dissolved substrate supply and microbial activity. Our study highlights the different decomposition properties and underlying mechanisms of soil dynamics between fibrous and amorphous soil horizons. Soil decomposition models should consider explicitly representing different boreal soil horizons and soil-microbial interactions to better characterize biogeochemical processes in boreal ecosystems. A more comprehensive representation of critical biogeochemical mechanisms of soil moisture effects may be required to improve the performance of the soil model we analyzed in this study.

It is important to understand the fate of carbon in boreal peatland soils in response to climate change because a substantial change in release of this carbon as CO2 and CH4 could influence the climate system. The goal of this research was to synthesize the results of a field water table manipulation experiment conducted in a boreal rich fen into a process-based model to understand how soil organic carbon (SOC) of the rich fen might respond to projected climate change. This model, the peatland version of the dynamic organic soil Terrestrial Ecosystem Model (peatland DOS-TEM), was calibrated with data collected during 2005-2011 from the control treatment of a boreal rich fen in the Alaska Peatland Experiment (APEX). The performance of the model was validated with the experimental data measured from the raised and lowered water-table treatments of APEX during the same period. The model was then applied to simulate future SOC dynamics of the rich fen control site under various CO2 emission scenarios. The results across these emissions scenarios suggest that the rate of SOC sequestration in the rich fen will increase between year 2012 and 2061 because the effects of warming increase heterotrophic respiration less than they increase carbon inputs via production. However, after 2061, the rate of SOC sequestration will be weakened and, as a result, the rich fen will likely become a carbon source to the atmosphere between 2062 and 2099. During this period, the effects of projected warming increase respiration so that it is greater than carbon inputs via production. Although changes in precipitation alone had relatively little effect on the dynamics of SOC, changes in precipitation did interact with warming to influence SOC dynamics for some climate scenarios.

[1] Post-fire storage of carbon (C) in organic-soil horizons was measured in one Canadian and three Alaskan chronosequences in black spruce forests, together spanning stand ages of nearly 200 yrs. We used a simple mass balance model to derive estimates of inputs, losses, and accumulation rates of C on timescales of years to centuries. The model performed well for the surface and total organic soil layers and presented questions for resolving the dynamics of deeper organic soils. C accumulation in all study areas is on the order of 20–40 gC/m2/yr for stand ages up to ∼200 yrs. Much larger fluxes, both positive and negative, are detected using incremental changes in soil C stocks and by other studies using eddy covariance methods for CO2. This difference suggests that over the course of stand replacement, about 80% of all net primary production (NPP) is returned to the atmosphere within a fire cycle, while about 20% of NPP enters the organic soil layers and becomes available for stabilization or loss via decomposition, leaching, or combustion. Shifts toward more frequent and more severe burning and degradation of deep organic horizons would likely result in an acceleration of the carbon cycle, with greater CO2 emissions from these systems overall.

[1] Several fundamental but important factors controlling the feedback of boreal organic carbon (OC) to climate change were examined using a mechanistic model of soil OC dynamics, including the combined effects of temperature and moisture on the decomposition of OC and the factors controlling carbon quality and decomposition with depth. To estimate decomposition rates and evaluate their variations with depth, the model was inverted using a global optimization algorithm. Three sites with different drainage conditions that represent a broad diversity of boreal black spruce ecosystems were modeled. The comparison among the models with different depth patterns of decomposition rates (i.e., constant, linear, and exponential decrease) revealed that the model with constant inherent decomposition rates through the soil profile was able to fit the observed data in the most efficient way. There were also lower turnover times in the wettest site compared to the drier site even after accounting for moisture and temperature differences. Taken together, these results indicate that decomposition (especially for the wetter site) was not accurately represented with standard moisture and temperature controls and that other important protection mechanisms (e.g., limitation of O2, redox conditions, and permafrost) rather than low inherent decomposition rates are responsible for the recalcitrance of deep OC. The simulation results also showed that most of the soil CO2 efflux is generated from subsurface layers of OC because of the large OC stocks and optimal moisture conditions, suggesting that these deeper soil OC stocks are likely to be critically important to the future carbon dynamics.

[1] The presence of 17β-estradiol in the environment, even at parts-per-trillion concentrations, raises significant concern regarding the health of aquatic organisms. Once 17β-estradiol is released into the environment from human and animal sources, its fate and transport is controlled by factors such as sorption and transformation, which need to be understood to fully assess potential exposures. The objective of this study was first to discern, through controlled batch experiments, the simultaneous transformation (i.e., chemical and biological) of natural estrogenic compounds and their mass exchange between the aqueous and solid phase (i.e., reversible and irreversible sorption sites). In addition, a model was developed that used a series of first-order expressions to describe the various fate and transport processes of parent and metabolite estrogens in the nonequilibrium batch experiments. A global optimization method was used to estimate the parameters of this nonequilibrium batch model. The model provided a good description of the data, and the parameter estimates were reliable. The batch studies parameter estimates were then incorporated into a convective-dispersive model to describe two undisturbed column experiments. The consistency of parameter estimates between the batch and column experiments indicated a high capability and reliability of this model and the parameter values.

Steroidal hormones are constantly released into the environment by man-made and natural sources. The goal of this study was to examine the persistence and fate of 17beta-estradiol and testosterone, the two primary natural sex hormones. Incubation experiments were conducted under aerobic and anaerobic conditions using [4-(14)C]-radiolabeled 17beta-estradiol and testosterone. The results indicated that 6% of 17beta-estradiol and 63% of testosterone could be mineralized to (14)CO(2) in native soils under aerobic conditions. In native soils under anaerobic conditions, 2% of testosterone and no 17beta-estradiol was methanogenized to (14)CH(4). Essentially, no mineralization of either testosterone or 17beta-estradiol to (14)CO(2) occurred in autoclaved soils under aerobic or anaerobic condition. Results also indicated that 17beta-estradiol could be transformed to an unidentified polar compound through abiotic chemical processes; however, 17beta-estradiol was only oxidized to estrone via biological processes. The TLC results also indicated that testosterone was degraded, not by physical-chemical processes but by biological processes. Results also indicated that the assumed risks of estrogenic hormones in the environment might be over-estimated due to the soil's humic substances, which can immobilize majority of estrogenic hormones, and thereby reduce their bioavailability and toxicity.

The vast amount of organic carbon (OC) stored in soils of the northern circumpolar permafrost region is a potentially vulnerable component of the global carbon cycle. However, estimates of the quan ...