abstract: Drylands (arid and semi-arid grassland ecosystems) cover about 40% of the Earth's surface and support over 40% of the human population, most of which is in emerging economies. Human development of drylands leads to topsoil loss, and over the last 160 years, woody plants have encroached on drylands, both of which have implications for maintaining soil viability. Understanding the spatial variability in erosion and soil organic carbon and total nitrogen under varying geomorphic and biotic forcing in drylands is therefore of paramount importance. This study focuses on how two plants, palo verde (Parkinsonia microphylla, nitrogen-fixing) and jojoba (Simmondsia chinensis, non-nitrogen fixing), affect sediment transport and soil organic carbon and total nitrogen pools in a dryland environment north of Phoenix, Arizona. Bulk samples were systematically collected from the top 10 cm of soil in twelve catenae to control for the existence and type of plants, location to canopy (sub- or intercanopy, up- or downslope), aspect, and distance from the divide. Samples were measured for soil organic carbon and total nitrogen and an unmanned aerial system-derived digital elevation map of the field site was created for spatial analysis. A subset of the samples was measured for the short-lived isotopes 137Cs and 210Pbex, which serve as proxy erosion rates. Erosional soils were found to have less organic carbon and total nitrogen than depositional soils. There were clear differences in the data between the two plant types: jojoba catenae had higher short-lived isotope activity, lower carbon and nitrogen, and smaller canopies than those of palo verde, suggesting lower erosion rates and nutrient contributions from jojoba plants. This research quantifies the importance of biota on influencing hillslope and soil dynamics in a semi-arid field site in central AZ and finishes with a discussion on the global implications for soil sustainability. / Dissertation/Thesis / Masters Thesis Geological Sciences 2018

Soil organic N (SON) comprises 90% of all N in surface soils, yet as much as half remains in forms which are chemically unknown or, at best, poorly understood. Analytical methods such has pyrolysis field-ionization mass spectrometry (Py-FIMS) and 15N cross polarization magic-angle spinning nuclear magnetic resonance (CPMAS-NMR) spectroscopy are widely used for the characterization of SON; however, these methods have limitations which contribute to the gaps in our understanding of SON chemistry. For example, Py-FIMS may produce heat-induced secondary compounds, and 15N-NMR may lack sensitivity and resolution for experiments at natural 15N abundance. X-ray absorption near edge structure (XANES) spectroscopy probes the bonding environment of individual elements. The application of this technique to complex environmental samples such as soil is still in its infancy, but early studies suggest that this technique may help resolve SON molecular structure. This dissertation sought to develop and apply synchrotron-based N and C K-edge XANES spectroscopy to the study of soil and soil extracts to determine the structures in which SON is bound. In these studies, Py-FIMS was coupled with XANES as a corroboratory technique.<p> Initial methodological development resulted in a calibration method whereby N2 gas generated in ammonium-containing salts was used to calibrate a soft X-ray beamline at the N K-edge. Although XANES can produce secondary compound artifacts, contrary to early assertions that it is a non-destructive technique, it was shown in a second study that beam-induced decomposition can be minimized by moving the beam to a fresh spot between scans.<p> Three applied studies exploring SON composition were conducted. These studies followed a spatial gradient ranging from the landscape scale, through a rhizosphere study, and ended with a study of glomalin-related soil protein (GRSP). Glomalin-related soil protein is a persistent soil glycoprotein of arbuscular mycorrhizal origin (AMF) implicated in aggregation and long-term C and N storage. Nitrogen and C K-edge XANES and Py-FIMS were used in all studies, and GRSP was further characterized using proteomics techniques.<p> Soil organic N composition was largely controlled by topographic position, and to a lesser degree, by cultivation. Divergent (i.e., water shedding) positions were enriched in carbohydrates and low molecular weight lignins, whereas convergent, depressional and level positions showed enrichment in lipid-type compounds. These differences were attributed to tillage-induced redistribution of soil, and water movement from upper to lower slope positions. Nitrogen XANES revealed a unique form of organic N, identified as N-bonded aromatics, particularly in the divergent positions.<p> Rhizosphere soil was enriched in higher molecular weight lipid-type materials and depleted in low molecular weight polar compounds. This was attributed to increased input of fresh plant material and higher microbial turnover in the rhizosphere. Nitrogen-bonded aromatics also were detected in the rhizosphere.<p> The GRSP extracts were characterized as mostly proteinaceous, but also contained many co-extracted, non-protein compounds. Despite being previously described as a glycoprotein, only weak carbohydrate signals were observed. Proteomics-based assessment of GRSP showed no homology to any proteins of AMF origin, instead showing homology with thioredoxin and with heat-stable soil proteins. This may be because protein databases do not yet contain glomalin-related sequences, or that glomalin is homologous to non-AMF soil proteins.<p> This dissertation demonstrated that N XANES is a sensitive and novel method for characterizing SON, and can be used complementarily with other analytical techniques such as Py-FIMS and proteomics. The continued development of XANES will provide a useful tool for SOM research into the future.

Soil organic N (SON) comprises 90% of all N in surface soils, yet as much as half remains in forms which are chemically unknown or, at best, poorly understood. Analytical methods such has pyrolysis field-ionization mass spectrometry (Py-FIMS) and 15N cross polarization magic-angle spinning nuclear magnetic resonance (CPMAS-NMR) spectroscopy are widely used for the characterization of SON; however, these methods have limitations which contribute to the gaps in our understanding of SON chemistry. For example, Py-FIMS may produce heat-induced secondary compounds, and 15N-NMR may lack sensitivity and resolution for experiments at natural 15N abundance. X-ray absorption near edge structure (XANES) spectroscopy probes the bonding environment of individual elements. The application of this technique to complex environmental samples such as soil is still in its infancy, but early studies suggest that this technique may help resolve SON molecular structure. This dissertation sought to develop and apply synchrotron-based N and C K-edge XANES spectroscopy to the study of soil and soil extracts to determine the structures in which SON is bound. In these studies, Py-FIMS was coupled with XANES as a corroboratory technique.<p> Initial methodological development resulted in a calibration method whereby N2 gas generated in ammonium-containing salts was used to calibrate a soft X-ray beamline at the N K-edge. Although XANES can produce secondary compound artifacts, contrary to early assertions that it is a non-destructive technique, it was shown in a second study that beam-induced decomposition can be minimized by moving the beam to a fresh spot between scans.<p> Three applied studies exploring SON composition were conducted. These studies followed a spatial gradient ranging from the landscape scale, through a rhizosphere study, and ended with a study of glomalin-related soil protein (GRSP). Glomalin-related soil protein is a persistent soil glycoprotein of arbuscular mycorrhizal origin (AMF) implicated in aggregation and long-term C and N storage. Nitrogen and C K-edge XANES and Py-FIMS were used in all studies, and GRSP was further characterized using proteomics techniques.<p> Soil organic N composition was largely controlled by topographic position, and to a lesser degree, by cultivation. Divergent (i.e., water shedding) positions were enriched in carbohydrates and low molecular weight lignins, whereas convergent, depressional and level positions showed enrichment in lipid-type compounds. These differences were attributed to tillage-induced redistribution of soil, and water movement from upper to lower slope positions. Nitrogen XANES revealed a unique form of organic N, identified as N-bonded aromatics, particularly in the divergent positions.<p> Rhizosphere soil was enriched in higher molecular weight lipid-type materials and depleted in low molecular weight polar compounds. This was attributed to increased input of fresh plant material and higher microbial turnover in the rhizosphere. Nitrogen-bonded aromatics also were detected in the rhizosphere.<p> The GRSP extracts were characterized as mostly proteinaceous, but also contained many co-extracted, non-protein compounds. Despite being previously described as a glycoprotein, only weak carbohydrate signals were observed. Proteomics-based assessment of GRSP showed no homology to any proteins of AMF origin, instead showing homology with thioredoxin and with heat-stable soil proteins. This may be because protein databases do not yet contain glomalin-related sequences, or that glomalin is homologous to non-AMF soil proteins.<p> This dissertation demonstrated that N XANES is a sensitive and novel method for characterizing SON, and can be used complementarily with other analytical techniques such as Py-FIMS and proteomics. The continued development of XANES will provide a useful tool for SOM research into the future.

The features of upwelled water are cold, salty and nutrient-rich. However, factors such as the air-sea exchanges of heat affect temperature, and freshwater input from rivers, precipitation and evaporation affect salinity. As biologically important elements are mostly in the dissolved inorganic forms in young upwelled waters, and are mostly in the particulate organic forms in old upwelled waters, the aging status of upwelled waters can be expressed as the relative percentages of biologically important elements in the inorganic and organic forms. Further, nutrients may be consumed by biological productivity. For these reasons, we hereby judge upwelling in the Taiwan Strait (TS) between 2000 and 2002 by the Degree of Nutrient Consumption (DNC, DNCC = and DNCX = ¡AX is nitrogen or phosphorus). The value of DNC is low in young upwelled waters but high in old upwelled waters. In summer, autumn and winter, waters at, or east of, a front in the northeastern Taiwan Strait were affected by the Kuroshio off eastern Taiwan. This front divides the Kuroshio water, the South China Sea (SCS) water that flows through the TS and the Coastal China Current water (in winter). The implications are that not all currents in the Taiwan Strait flow in a northerly direction, even in summer. Because the axis of Kuroshio moved away from eastern Taiwan and upwelling weakened in SCS in 2002, salinity east of the front was fresher, and nutrient and DON were lower in 2002 than 2001. On the other hand, upwelling induced higher DON west of the front. In August, 2002, the water in the southern TS was higher in temperature, more salty, but nutrient and DON were lower than in 2001 because of weakened upwelling in the SCS, and water that intruded into the TS had a higher percentage of Kuorshio. The trend of upwelling, DNCC,P,N was along the west Penghu Channel from bottom to surface. Rates of temperature, salinity and DNCC,P,N variation were greater during 2001 than in 2002, reflecting slower rate of upwelling in 2002.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2003. / Härtill 5 uppsatser.

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abstract: Population growth and fresh water depletion challenge drinking water utilities. Surface water quality is impacted significantly by climate variability, human activities, and extreme events like natural disasters. Dissolved organic carbon (DOC) is an important water quality index and the precursor of disinfection by-products (DBPs) that varies with both hydrologic and anthropogenic factors. Granular activated carbon (GAC) is a best available technology for utilities to meet Stage 2 D/DBP rule compliance and to remove contaminants of emerging concern (CECs) (e.g., pharmaceutical, personal care products (PCPs), etc.). Utilities can operate GAC with more efficient and flexible strategies with the understanding of organic occurrence in source water and a model capable predicting DOC occurrence. In this dissertation, it was found that DOC loading significantly correlated with spring runoff and was intensified by dry-duration antecedent to first flush. Dynamic modeling based on reservoir management (e.g., pump-back operation) was established to simulate the DOC transport in the reservoir system. Additionally, summer water recreational activities were found to raise the level of PCPs, especially skin-applied products, in raw waters. GAC was examined in this dissertation for both carbonaceous and emerging nitrogenous DBP (N-DBP) precursors (i.e., dissolved organic nitrogen (DON)) removal. Based on the experimental findings, GAC preferentially removes UV254-absorbing material, and DOC is preferentially removed over DON which may be composed primarily of hydrophilic organic and results in the low affinity for adsorption by GAC. The presence of organic nitrogen can elevate the toxicity of DBPs by forming N-DBPs, and this could be a major drawback for facilities considering installation of a GAC adsorber owing to the poor removal efficiency of DON by GAC. A modeling approach was established for predicting DOC and DON breakthrough during GAC operation. However, installation of GAC adsorber is a burden for utilities with respect to operational and maintenance cost. It is common for utilities to regenerate saturated GAC in order to save the cost of purchasing fresh GAC. The traditional thermal regeneration technology for saturated GAC is an energy intensive process requiring high temperature of incineration. Additionally, small water treatment sites usually ship saturated GAC to specialized facilities for regeneration increasing the already significant carbon footprint of thermal regeneration. An innovative GAC regeneration technique was investigated in this dissertation for the feasibility as on-site water treatment process. Virgin GAC was first saturated by organic contaminant then regenerated in-situ by iron oxide nanocatalysts mixed with hydrogen peroxide. At least 70 % of adsorption capacity of GAC can be regenerated repeatedly for experiments using modeling compound (phenol) or natural organic matter (Suwannee River humic acid). The regeneration efficiency increases with increasing adsorbate concentration. Used-iron nanocatalysts can be recovered repeatedly without significant loss of catalytic ability. This in-situ regeneration technique provides cost and energy efficient solution for water utilities considering GAC installation. Overall, patterns were found for DOC and CEC variations in drinking water sources. Increasing concentrations of bulk (DOC and DON) and/or trace organics challenge GAC operation in utilities that have limited numbers of bed-volume treated before regeneration is required. In-situ regeneration using iron nanocatalysts and hydrogen peroxide provides utilities an alternative energy-efficient operation mode when considering installation of GAC adsorber. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2012

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The Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GoM) in the spring of 2010 introduced 4.4 million of barrels of oil to the ecosystem. Some biodegradation of the oil occurs when microorganisms, particularly bacteria, metabolize the oil as a carbon source. During this process, the microbes also require nutrients for energy. An introduction of oil at this magnitude has the ability to induce large blooms of microbes, which in turn can affect nutrient concentrations. Microbial petroleum degradation decreases nutrient concentrations, whereas the microbial assimilation and decay of organic matter increase nutrient concentrations. This study assessed whether any changes in nitrate, ammonium, and/or phosphate concentrations from historical levels could be attributed to the oil spill as a result of biodegradation, and how those changes can impact the GoM ecosystem. Nutrient samples were collected at discrete depths throughout the water column, in a cross-shelf transect inland from the spill site outside the DeSoto Canyon, in August 2010, February 2011, and May 2011 (four months to one year after the spill). In August 2010, a subsurface oil plume was found at depths of 1000 m to 1200 m. At the same depth of ~1000 m, a significant decrease in nitrate was observed, indicating the biodegradation of oil by heterotrophic bacteria of the aphotic zone, compared to earlier data during August 2000, when no known oils were present. Overall temporal increases in ammonium and dissolved organic nitrogen (DON) were observed both in near-surface waters and at an intermediate depth of ~400 m next to the walls of the DeSoto Canyon, suggesting an incremental die-off of both plankton and benthic organisms during accelerated recycling of nutrients. Continued decreases of phosphate were observed into February 2011, supporting ongoing biodegradation then as well. By May 2011, however, there were more increases in near-surface ammonium concentrations, compared to April 2000, with the implication that continued interseasonal recycled nitrogen accumulations may have been due to a decadal ecological regime shift, after a combination of top-down overfishing, petroleum perturbations, and/or increases of toxic harmful algal blooms (HABs).

Nitrogen (N) is known to be a limiting factor in peatlands and as such, the vegetation present has adapted to living in low N conditions. This makes such ecosystems particularly vulnerable to increases in the deposition of reactive N (Nr), which may result in significant changes to its biodiversity and biogeochemistry. Since the industrial revolution, the amount of anthropogenic Nr globally has increased from ~15 Tg N y-1 in the 1860’s to ~187 Tg N y-1 in 2005, and is estimated to reach ~267 Tg N yr-1 by 2050 (Galloway et al. 2004, Galloway et al. 2008). Consequences include acidification, loss of biodiversity, changes in vegetation, N-saturation, eutrophication, health impacts and the release of greenhouse gases.Objectives of this thesis were (i) to measure key components of the N-budget at Auchencorth Moss, a Scottish moorland, for a two year period (Jan 2009 – Dec 2010) and (ii) to compare current deposition rates with those measured 14/15 years previously. Annual fluxes of N inputs were estimated from measurements of wet only deposition, estimates of N-fixation deposition and from atmospheric deposition modelled from hourly concentrations of N containing gases and aerosols. Exports were estimated from stream measurements and from atmospheric emissions modelled from hourly concentrations. Organic N is often an underreported part of the N-cycle, but the results presented here suggest it is an important part of the N story. An attempt to identify (dissolved organic nitrogen) DON compounds in both precipitation and stream water was made using GC×GC-NCD. Ten unique compounds were detected, of which only five could be identified: pyrrole, benzonitrile, dodecylamine, N-nitrosodipropylamine and decylamine. Pyrrole, benzonitrile and three unknown compounds were present in both precipitation and stream samples. Ammonia (NH3) fluxes were measured over a 7 month period in 2009 using a wet-chemistry gradient system with online analysis and calculated with the aerodynamic gradient method. The results were used to refine a bi-directional dynamic exchange model. Several parameters were updated, including an increased stomatal emission potential from 180 to 350, a reduction of the minimum cuticular resistance (Rw,min) used to calculate Rw from 20 s m-1 to 15 s m-1 and an increase in the leaching rate (Kr¬) from the leaf surfaces from -0.01 to -0.1 s-1. The exchange parameterisations used to estimate HNO3, HONO and the aerosol compounds were taken from the literature and earlier studies at the site.Overall, Auchencorth was found to accumulate N, with deposition exceeding export by -1.61 kg N ha-1 yr-1. The main N deposition was from NH3, followed by wet deposition of ammonium. DON, which is not routinely included in N budgets, contributed 6.5% of total deposition. The largest loss of N was as DON via the stream with N losses of -5.31 kg N ha-1 yr-1 or 71.8% of total export. Between 1995 and 2009/2010, deposition decreased by 0.81 kg N ha-1 yr-1, with the wet deposition of inorganic nitrogen decreasing by 25.2%, but dry deposition increasing by 12.5%. DON, N2O and N-fixation were not included in the comparison as they were not measured in 1995.This thesis has demonstrated that DON is an important parameter in the overall N budget, and should be routinely measured when assessing the N status of ecosystems.