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Description
Biological soil crusts (BSCs) are critical components of arid and semiarid environments and provide the primary sources of bioavailable macronutrients and increase micronutrient availability to their surrounding ecosystems. BSCs are composed of a variety of microorganisms that perform a wide range of physiological processes requiring a multitude of bioessential micronutrients, such as iron, copper, and molybdenum. This work investigated the effects of BSC activity on soil solution concentrations of bioessential elements and examined the microbial production of organic chelators, called siderophores. I found that aluminum, vanadium, copper, zinc, and molybdenum were solubilized in the action of crusts, while nickel, zinc, arsenic, and zirconium were immobilized by crust activity. Potassium and manganese displayed behavior consistent with biological removal and mobilization, whereas phosphorus and iron solubility were dominated by abiotic processes. The addition of bioavailable nitrogen altered the effects of BSCs on soil element mobilization. In addition, I found that the biogeochemical activites of BSCs were limited by molybdenum, a fact that likely contributes to co-limitation by nitrogen. I confirmed the presence of siderophore producing microbes in BSCs. Siderophores are low-molecular weight organic compounds that are released by bacteria to increase element solubility and facilitate element uptake; siderophore production is likely the mechanism by which BSCs affect the patterns I observed in soil solution element concentrations. Siderophore producers were distributed across a range of bacterial groups and ecological niches within crusts, suggesting that siderophore production influences the availability of a variety of elements for use in many physiological processes. Four putative siderophore compounds were identified using electrospray ionization mass spectrometry; further attempts to characterize the compounds confirmed two true siderophores. Taken together, the results of my work provide information about micronutrient cycling within crusts that can be applied to BSC conservation and management. Fertilization with certain elements, particularly molybdenum, may prove to be a useful technique to promote BSC growth and development which would help prevent arid land degradation. Furthermore, understanding the effects of BSCs on soil element mobility could be used to develop useful biomarkers for the study of the existence and distribution of crust-like communities on ancient Earth, and perhaps other places, like Mars.
ContributorsNoonan, Kathryn Alexander (Author) / Hartnett, Hilairy (Thesis advisor) / Anbar, Ariel (Committee member) / Garcia-Pichel, Ferran (Committee member) / Shock, Everett (Committee member) / Sharp, Thomas (Committee member) / Arizona State University (Publisher)
Created2012
Description
Aboveground net primary production (ANPP) is an important ecosystem process that, in drylands, is most frequently limited by water availability. Water availability for plants is in part controlled by the water holding capacity of soils. Available water holding capacity (AWHC) of soils is strongly influenced by soil texture and depth. This study drew upon localized rain gauge data and four data-sets of cover-line and biomass data to estimate ANPP and to determine annual precipitation (PPT). I measured soil depth to caliche and texture by layer of 112 plots across the four landscape units for which estimation of ANPP were available. A pedotransfer function was used to estimate AWHC from soil depth increments to depth of caliche measurements and texture analysis. These data were analyzed using simple and multivariate regression to test the effect of annual precipitation and available water holding capacity on aboveground net primary production. Soil texture remained constant among all plots (sandy loam) and depth to caliche varied from 15.16 cm to 189 cm. AWHC and the interaction term (PPT*AWHC) were insignificant (p=0.142, p=0.838) and annual PPT accounted for 18.4% of the variation in ANPP. The y-intercept was significantly different for ANPP ~ annual PPT when considering AWHC values either above or below 3 cm. Shrub ANPP was insensitive to precipitation regardless of AWHC (R2=-0.012, R2=0.014). Results from this study indicate that a model incorporating annual PPT and AWHC may not serve as a good predictor for ANPP at a site level where there is little variation in soil texture.
ContributorsWagner, Svenja K (Author) / Sala, Osvaldo E. (Thesis advisor) / Cease, Arianne (Committee member) / Hall, Sharon (Committee member) / Peters, Debra (Committee member) / Arizona State University (Publisher)
Created2019
Description
In this project, I investigated the ecosystem services, or lack thereof, that landscape designs created in terms of microclimate modification at 11 residential homes throughout the Phoenix Metro Area. I also created an article for the homeowners who participated, explaining what I did and how they could apply my research. My research question was how a person can achieve a comfortable outdoor climate in their yard without over-using scarce water resources. I hypothesized that there would be a negative correlation between the maximum air temperature and the percent shade in each yard, regardless of the percent grass. I analyzed the data I collected using the program, R, and discovered that my hypothesis was supported for the month of July. These results are in line with previous studies on the subject and can help homeowners make informed decisions about the effects their landscaping choices might have.
ContributorsBarton, Erin Michaela (Author) / Hall, Sharon (Thesis director) / Ruddell, Benjamin (Committee member) / Spielmann, Katherine (Committee member) / Barrett, The Honors College (Contributor) / School of Sustainability (Contributor)
Created2014-05
Description
The Prosopis genus of trees, also known as mesquites, are uniquely equipped to allow for an agroforestry regime in which crops can be grown beneath the canopy of the tree. Mesquites have the ability to redistribute water moisture in such a way that allows plants under the canopy to use water that has been brought up by the roots of mesquite trees. This means that there is a potential for food crops to be grown under the trees without using additional irrigation measures. This could be used where access to water is limited or for a sustainability-minded farmer who is trying to reduce water inputs in an arid environment. Mesquite trees produce a variety of products, including lumber and bean pods that can be ground down into an edible flour. Both products demand a high price in the marketplace and are produced in addition to the crops that can potentially be grown beneath the mesquite tree. In order to determine whether or not it is possible to grow crops under mesquite trees, I reviewed a wide range of literature regarding hydraulic redistribution, mesquite trees in general, and what plants might be best suited for growing beneath a mesquite. The list of plants was narrowed down to four crops that seemed most likely to survive in shaded, low water conditions in a hot environment. There has not been any research done on crops growing beneath mesquite trees, so the next step for research would be to experiment with each of the crops to determine how well each species can adapt to the specified conditions.
ContributorsMesser, Luke Winston (Author) / Eakin, Hallie (Thesis director) / Hall, Sharon (Committee member) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Polycyclic aromatic hydrocarbon (PAH) redistribution in extreme dust storms and processing in clouds
Description
Dust storms known as 'haboobs' occur in the City of Tempe, AZ during the North American monsoon season. A haboob classification method based on meteorological and air quality measurements is described. There were from 3 to 20 haboob events per year over the period from 2005 to 2014. The calculated annual TSP (total suspended particulate) dry deposition during haboobs is estimated to contribute 74% of the total particulate mass deposited in Tempe, AZ.
Dry deposition is compared with the aqueous chemistry of Tempe Town Lake. Water management and other factors may have a stronger impact on Tempe Town Lake chemistry than haboob dry-deposition. Haboobs alter the Polycyclic Aromatic Hydrocarbon (PAH) concentrations and distributions in Tempe, AZ. PAH isomer ratios suggest PM2.5 (particulate matter with aerodynamic diameters less than or equal to 2.5 μm) sources consistent with approximate thunderstorm outflow paths.
The importance of the atmospheric aqueous phase, fogs and clouds, for the processing and removal of PAHs is not well known. A multiphase model was developed to determine the fate and lifetime of PAHs in fogs and clouds. The model employed literature values that describe the partitioning between three phases (aqueous, liquid organic, and gas), in situ PAH measurements, and experimental and estimated (photo)oxidation rates. At 25 °C, PAHs with two, three and four rings were predicted to be primarily gas phase (fraction in the gas phase xg > 90 %) while five- and six-ring PAHs partitioned significantly into droplets (xg < 60 %) with aqueous phase fractions of 1 to 6 % and liquid organic phase fractions of 31 to 91 %. The predicted atmospheric lifetimes of PAHs in the presence of fog or cloud droplets (< 5 hours) were significantly shorter than literature predictions of PAH wet and dry deposition lifetimes (1 to 14 days and 5 to 15 months respectively) and shorter than or equal to predicted PAH gas phase / particle phase atmospheric lifetimes (1 to 300 hours). The aqueous phase cannot be neglected as a PAH sink due to the large aqueous volume (vs. organic volume) and the relatively fast aqueous reactions.
Dry deposition is compared with the aqueous chemistry of Tempe Town Lake. Water management and other factors may have a stronger impact on Tempe Town Lake chemistry than haboob dry-deposition. Haboobs alter the Polycyclic Aromatic Hydrocarbon (PAH) concentrations and distributions in Tempe, AZ. PAH isomer ratios suggest PM2.5 (particulate matter with aerodynamic diameters less than or equal to 2.5 μm) sources consistent with approximate thunderstorm outflow paths.
The importance of the atmospheric aqueous phase, fogs and clouds, for the processing and removal of PAHs is not well known. A multiphase model was developed to determine the fate and lifetime of PAHs in fogs and clouds. The model employed literature values that describe the partitioning between three phases (aqueous, liquid organic, and gas), in situ PAH measurements, and experimental and estimated (photo)oxidation rates. At 25 °C, PAHs with two, three and four rings were predicted to be primarily gas phase (fraction in the gas phase xg > 90 %) while five- and six-ring PAHs partitioned significantly into droplets (xg < 60 %) with aqueous phase fractions of 1 to 6 % and liquid organic phase fractions of 31 to 91 %. The predicted atmospheric lifetimes of PAHs in the presence of fog or cloud droplets (< 5 hours) were significantly shorter than literature predictions of PAH wet and dry deposition lifetimes (1 to 14 days and 5 to 15 months respectively) and shorter than or equal to predicted PAH gas phase / particle phase atmospheric lifetimes (1 to 300 hours). The aqueous phase cannot be neglected as a PAH sink due to the large aqueous volume (vs. organic volume) and the relatively fast aqueous reactions.
ContributorsEagar, Jershon (Author) / Herckes, Pierre (Thesis advisor) / Hayes, Mark (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2016
Description
Biological soil crusts (BSCs), topsoil microbial assemblages typical of arid land ecosystems, provide essential ecosystem services such as soil fertilization and stabilization against erosion. Cyanobacteria and lichens, sometimes mosses, drive BSC as primary producers, but metabolic activity is restricted to periods of hydration associated with precipitation. Climate models for the SW United States predict changes in precipitation frequency as a major outcome of global warming, even if models differ on the sign and magnitude of the change. BSC organisms are clearly well adapted to withstand desiccation and prolonged drought, but it is unknown if and how an alteration of the precipitation frequency may impact community composition, diversity, and ecosystem functions. To test this, we set up a BSC microcosm experiment with variable precipitation frequency treatments using a local, cyanobacteria-dominated, early-succession BSC maintained under controlled conditions in a greenhouse. Precipitation pulse size was kept constant but 11 different drought intervals were imposed, ranging between 416 to 3 days, during a period of 416 days. At the end of the experiments, bacterial community composition was analyzed by pyrosequencing of the 16s rRNA genes in the community, and a battery of functional assays were used to evaluate carbon and nitrogen cycling potentials. While changes in community composition were neither marked nor consistent at the Phylum level, there was a significant trend of decreased diversity with increasing precipitation frequency, and we detected particular bacterial phylotypes that responded to the frequency of precipitation in a consistent manner (either positively or negatively). A significant trend of increased respiration with increasingly long drought period was detected, but BSC could recover quickly from this effect. Gross photosynthesis, nitrification and denitrification remained essentially impervious to treatment. These results are consistent with the notion that BSC community structure adjustments sufficed to provide significant functional resilience, and allow us to predict that future alterations in precipitation frequency are unlikely to result in severe impacts to BSC biology or ecological relevance.
ContributorsMyers, Natalie Kristine (Author) / Garcia-Pichel, Ferran (Thesis advisor) / Hall, Sharon (Committee member) / Turner, Benjamin (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2013
Description
As air quality standards become more stringent to combat poor air quality, there is a greater need for more effective pollutant control measures and increased air monitoring network coverage. Polluted air, in the form of aerosols and gases, can impact respiratory and cardiovascular health, visibility, the climate, and material weathering. This work demonstrates how traditional networks can be used to study generational events, how these networks can be supplemented with low-cost sensors, and the effectiveness of several control measures. First, an existing network was used to study the effect of COVID-19 travel restrictions on air quality in Maricopa County, Arizona, which would not have been possible without the historical record that a traditional network provides. Although this study determined that decreases in CO and NO2 were not unique to the travel restrictions, it was limited to only three locations due to network sparseness. The second part of this work expanded the traditional NO2 monitoring network using low-cost sensors, that were first collocated with a reference monitor to evaluate their performance and establish a robust calibration. The sensors were then deployed to the field to varying results; their calibration was further improved by cycling the sensors between deployment and reference locations throughout the summer. This calibrated NO2 data, along with volatile organic compound data, were combined to enhance the understanding of ozone formation in Maricopa County, especially during wildfire season. In addition to being in non-attainment for ozone standards, Maricopa County fails to meet particulate matter under 10 μm (PM10) standards. A large portion of PM10 emissions is attributed to fugitive dust that is either windblown or kicked up by vehicles. The third part of this work demonstrated that Enzyme Induced Carbonate Precipitation (EICP) treatments aggregate soil particles and prevent fugitive dust emissions. The final part of the work examined tire wear PM10 emissions, as vehicles are another significant contributor to PM10. Observations showed a decrease in tire wear PM10 during winter with little change when varying the highway surface type.
ContributorsMiech, Jason Andrew (Author) / Herckes, Pierre (Thesis advisor) / Fraser, Matthew P (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2023
Description
Atmospheric particulate matter (PM) has a pronounced effect on our climate, and exposure to PM causes negative health outcomes and elevated mortality rates in urban populations. Reactions that occur in fog can form new secondary organic aerosol material from gas-phase species or primary organic aerosols. It is important to understand these reactions, as well as how organic material is scavenged and deposited, so that climate and health effects can be fully assessed. Stable carbon isotopes have been used widely in studying gas- and particle-phase atmospheric chemistry. However, the processing of organic matter by fog has not yet been studied, even though stable isotopes can be used to track all aspects of atmospheric processing, from particle formation, particle scavenging, reactions that form secondary organic aerosol material, and particle deposition. Here, carbon isotope analysis is used for the first time to assess the processing of carbonaceous particles by fog.
This work first compares carbon isotope measurements (δ13C) of particulate matter and fog from locations across the globe to assess how different primary aerosol sources are reflected in the atmosphere. Three field campaigns are then discussed that highlight different aspects of PM formation, composition, and processing. In Tempe, AZ, seasonal and size-dependent differences in the δ13C of total carbon and n-alkanes in PM were studied. δ13C was influenced by seasonal trends, including inversion, transport, population density, and photochemical activity. Variations in δ13C among particle size fractions were caused by sources that generate particles in different size modes.
An analysis of PM from urban and suburban sites in northeastern France shows how both fog and rain can cause measurable changes in the δ13C of PM. The δ13C of PM was consistent over time when no weather events occurred, but particles were isotopically depleted by up to 1.1‰ in the presence of fog due to preferential scavenging of larger isotopically enriched particles. Finally, the δ13C of the dissolved organic carbon in fog collected on the coast of Southern California is discussed. Here, temporal depletion of the δ13C of fog by up to 1.2‰ demonstrates its use in observing the scavenging and deposition of organic PM.
This work first compares carbon isotope measurements (δ13C) of particulate matter and fog from locations across the globe to assess how different primary aerosol sources are reflected in the atmosphere. Three field campaigns are then discussed that highlight different aspects of PM formation, composition, and processing. In Tempe, AZ, seasonal and size-dependent differences in the δ13C of total carbon and n-alkanes in PM were studied. δ13C was influenced by seasonal trends, including inversion, transport, population density, and photochemical activity. Variations in δ13C among particle size fractions were caused by sources that generate particles in different size modes.
An analysis of PM from urban and suburban sites in northeastern France shows how both fog and rain can cause measurable changes in the δ13C of PM. The δ13C of PM was consistent over time when no weather events occurred, but particles were isotopically depleted by up to 1.1‰ in the presence of fog due to preferential scavenging of larger isotopically enriched particles. Finally, the δ13C of the dissolved organic carbon in fog collected on the coast of Southern California is discussed. Here, temporal depletion of the δ13C of fog by up to 1.2‰ demonstrates its use in observing the scavenging and deposition of organic PM.
ContributorsNapolitano, Denise (Author) / Herckes, Pierre (Thesis advisor) / Fraser, Matthew (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2018