2199 research outputs found
Sort by
Pyrite Morphology, Texture, and Trace Metals Across a Weathering Profile (from Parent Rock to Soil) of Ohio Coal Shales
No full textAcid mine drainage (AMD) refers to the acidic outflow of water from a mining site caused by the weathering of pyrite (FeS2) present in coal. Oxidation of pyrite, within underground mine work and surface waste, releases sulfuric acid and metals, including nickel, cobalt, arsenic, and lead into surface and subsurface waters. AMD negatively impacts water quality, wildlife, and human health. The aim of this study was to determine changes in pyrite particle size, morphology, texture, and composition during the weathering of the parent coal-shale rock. This was accomplished by collecting scanning electron microscopy (SEM) images and energy dispersive spectroscopy (EDS) element maps of pyrite in the following materials: (1) the parent coal-shale rock; (2) rock powder before and after simulated weathering; and (3) soils developing on historic mine waste. Shale samples were crushed to 63, 250, and 2000 µm and subjected to an artificial weathering process over several months to observe if particle size impacted the degree of weathering and its effect on mineral morphology. Soils were collected at various depths and prepared as thin sections. The commonest morphologies seen were framboids and octahedra. Oxidation rim and replacement textures were observed repeatedly, especially in the soils. Iron and sulfur oxide concentrations were universally observed over the range of crushed particle sizes and various surface topographies. Oxidation rim textures are most abundant on small particles consistent with prolonged weathering, resulting in greater degrees of oxidation. Preliminary results suggest AMD production increases with greater variability of surface topography and decreasing particle size. Understanding how the release of AMD will progress in an impacted system, controlled by the degree of weathering of parent rock, is important to assessing its environmental impact. Characterization of mine spoil is instrumental to proper planning and implementation of treatment systems
More than One Way to Limit Algae: Trace Metal-Nutrient Colimitation of Algal Production
No full textAlgae use diverse mechanisms to acquire and sequester nutrients to support metabolism and growth. Some mechanisms include the use of trace metals as enzyme cofactors to support electron transfer proteins, for photosynthesis and respiration, or to produce enzymes that allow for use of less common organic nutrient sources. Much of what is understood about stream nutrient limitation focuses on just N and P, although trace metals support several underlying metabolic pathways that may also cause apparent nutrient limitation. We present data from streams in the Great Lakes basin that span a gradient of pristine to urban and low to high inorganic nutrient concentrations. We used trace metal nutrient diffusing substrates (tNDS) with different combinations of elements to identify trace metal-nutrient co-limitation of algae. Metal-nutrient co-limitation was observed in streams with low dissolved inorganic nutrients. Chlorophyll a concentrations showed that 80% of streams with low inorganic P were Zn-P co-limited. Net primary production estimates showed that streams with low inorganic N were Ni-N co-limited. We suggest that while a stream may appear N or P limited, the metabolic mechanism underlying this result may be due to trace metal co-limitation
The Impact of the Bokashi Composting Method on Soil Fungal Community Structure and Function
No full textConversion from traditional farming practices to more sustainable, organic methods is becoming increasingly popular. While widely practiced, little research has been performed on how many of these methods influence overall plant health and their impact on soil microbial communities. In Costa Rica, for instance, many local farms utilize an organic farming technique known as the Bokashi method. This method is an anaerobic composting technique that utilizes the fermentation of organic matter and waste as a means of adding nutrients to soil to increase crop productivity. This is method is not only cost effective, but it is also not as work intensive as traditional composting techniques. However, while this method has great potential and is widely used, the impact that it has on soil microbial community structure and function is still a mystery. In this study, we analyzed whether Bokashi treatments have an impact on fungal community structure within several Costa Rican fields. We sampled soil from cilantro and/or cabbage farms representing a chronosequence of the Bokashi organic farming method, which ranged in age of implementation from 1 – 18 years. After sampling, we utilized next-generation Illumina sequencing to examine fungal taxonomic community structure. Overall, samples were found to contain a diverse array of fungi with dominance of phyla belonging to Ascomycota and to a lesser extent Basidiomycota. We found that the length of time a farm has been organically managed has a marginally significant effect on soil fungal community composition. However, sampling site and crop type had a more significant effect, which may show the importance of surrounding plant cover and dispersal limitation in determining community composition. While our findings suggest a small potential effect of organic farming on community composition, further analysis will be performed on how it influences the distribution of fungal functional groups
Differentiation of Harmful Algal Bloom Signatures in the Indian River Lagoon by Remote Sensing
No full textLocated along the east coast of Florida, the Indian River Lagoon (IRL) is a shallow-marine estuary that extends along 240 km of coastline. Historically, freshwater flowing into the IRL has transported high concentrations of nitrogen and phosphorus runoff from agricultural fertilizers and septic systems. As a result, eutrophic waters have driven the growth of various types of harmful algal blooms (HABs). Previous remote sensing research has focused on monitoring water quality by identifying the spectral characteristics of color producing agents (CPAs) associated with HABs through the use of ocean color chlorophyll-a algorithms. The ability to reliably distinguish CPAs of HABs, color dissolved organic matter (CDOM), and suspended sediment within water bodies through remote sensing techniques has become critically important for monitoring regional water quality. Recent statistical techniques for processing Landsat 8 and Sentinel 3 imagery have expanded retrievals beyond chlorophyll-a and corrected for atmospheric interferences. The Kent State spectral decomposition method, a type of Varimax-rotated Principal Component Analysis (VPCA), is used to process visible reflectance spectra (400-700nm) from multispectral and hyperspectral imaging systems. The VPCA decomposition describes the total percentage of variability of CPAs mixed in the water column and determines the leading spectral components of the satellite image that contribute to the overall signal. We identify these leading spectral components obtained from this analysis with lab measured reflectance spectra, such as brown tide cultures, A. lagunensis, to qualitatively assess areas of the IRL which have relatively high or low proportions of CPAs over time. Results using the VPCA method have identified A. lagunensis constituents within the Banana River region of the IRL and have since been validated with in-situ biovolume and water quality measurements
Manganese dissolution kinetics and uptake rates by red maple trees in soils
No full textManganese, an essential nutrient critical for photosynthesis and a toxic element in excess, impacts forest metabolism, carbon storage, and ecosystem productivity. Given the significant role Mn can play, it is important to understand how soil geochemistry controls Mn uptake. We conducted a greenhouse pot experiment to quantify Mn uptake by plants based on controlled geochemical constraints. Specifically, we investigated whether Mn uptake was limited by the supply of Mn to soil solution or by biological controls within the plants. Tree pots containing soil-only or soil and red maple saplings were supplied with either dissolved Mn, Mn-oxides, or crushed shale containing Mn-bearing pyrite. We predict that Mn uptake would be higher in systems with dissolved Mn because it is not limited by mineral weathering, and that Mn uptake would be higher when the system is supplied with fast-weathering substrates (pyrite in the shale) than slow-weathering substrates (Mn-oxides). We analyzed the chemical composition of leaf tissue to quantify Mn uptake and soil leachate to quantify Mn losses. Leaf chemistry varied on orders of magnitude, with Mn uptake being the highest in the dissolved Mn treatment and lower in the Mn-oxide and shale treatments. Conductivity data indicates major solute loss in leached water from the dissolved Mn and shale treatment groups. The leached water from the shale group was extremely acidic, suggesting rapid dissolution of pyrite. Leachate chemistry indicates that Mn loss in the dissolved Mn treatment groups was two to 10 times higher than the other treatment groups. We conclude that vegetation stored Mn and reduced leaching rates in all treatments, and that Mn dissolution rates influenced plant uptake. Ongoing analyses include constructing mass balance models to quantify Mn uptake and leaching, microscale imaging techniques to examine root-soil associations and mineral transformation, and community analysis of Mn-oxidizing or reducing microorganisms
Oak tree differentiation of defense and reallocation strategies in response to herbivore pressure
No full textPlant strategies against herbivory may involve defending themselves by producing plant secondary metabolites (PSM), regrowing to negate injuries from tissue loss (tolerance), or reallocating resources to better defend or protect themselves from further damage. We investigated the strategies of oak plants to minimize herbivory by investment in tannins and reallocation of non-structural carbohydrates. Oak species may differentially invest in defenses and reallocation depending on the intensity and location of herbivore feeding. We simulated the effects of herbivory by removing 25% or 75% of oak tissue, removing either the apical or lateral meristems. The investment in defenses may act as a selective pressure driving herbivore diversity and behavior. Using 12 oak species from different parts of a well-supported phylogeny, we applied five treatments of simulated herbivory, varying in intensity and location. The 12 species were chosen to represent a broad array of geographical and phylogenetic diversity. Using an untransformed statistical analysis, we found that oak species invest differentially in defensive mechanisms. We will also present a more thorough phylogenetic comparative analysis of the data to determine if differences in defense and reallocation strategies are a result of adaptation to herbivory or if defense and reallocation strategies are associated with particular oak lineages
Understanding how microorganisms influence the bioavailability of iron-bound phosphate under shifting redox regimes in nutrient poor soils
No full textPlants remove carbon dioxide (CO2) from the atmosphere and can mitigate climate change, but require nutrients like phosphorus (P) to increase primary productivity and build biomass. P can become limiting to plant growth as changes in the water table alter soil redox conditions. These anoxic-oxic changes can influence geochemical sorption of phosphate (PO43-) to iron (oxyhydr)oxides, modifying P bioavailability. Vernal ponds are one such system that experience seasonal hydrologic changes that result in redox fluctuations. Release of iron-bound phosphorus through microbial mechanisms could increase P bioavailability for plants to grow and in turn take up more CO2. To assess how microbes affect the availability of P in iron-bound PO43-, we examined P uptake by the microbial community in vernal pond soils in Northeast Ohio. Mesh bags were filled with organic material and three types of synthetic iron oxides (ferrihydrite, goethite, and hematite). Iron oxides were either saturated in a PO43- solution or not sorbed with PO43-. Bags were incubated in both lowland (pond) and adjacent upland environments and removed during flooded conditions and after the pond had dried. Preliminary results show that bags in both environments that contained iron-bound PO43- had higher mass following incubation than those without PO43-, suggesting biomass accumulation. Release of iron-bound PO43- could supply plants with vital nutrients needed to grow, resulting in greater uptake of atmospheric CO2.</p
Evidence for net nitrogen gas production in Lake Erie surface waters
No full textTwo methods are commonly employed to quantify rates of N2-fixation in surface waters. Acetylene reduction assays (ARA) are an indirect measure of N2-fixation, relying on the conversion of acetylene to ethylene at a known mole ratio with respect to dissolved nitrogen gas. An alternative method, membrane-inlet-mass-spectrometry (MIMS), can directly quantify dissolved N2 gas concentrations in water.Here, surface sample grabs (0.5m depth) were collected at 6 sites in Sandusky Bay on 4 dates (N=24) and bioassays were performed using both techniques. Significant levels of N2-fixation were detected with ARA in 83% of samples, whereas net N2-fixation was not detected in any samples (0%) by analysis via MIMS. In contrasts, significant levels of N2-production were observed in 40% of the samples. N2-production is not possible to detect with ARA and would have been missed had MIMS not been employed. Notably, 36% of the samples yielded significant rates of N2-fixation via ARA and also net N2-production via MIMS. In order for analysis via MIMS to show significant increases in concentrations of dissolved N2, the rates of N2-production must exceed the rates of N2-fixation in those samples. It is well documented that members of the cyanobacterial order Nostocales produce specialized cells (heterocyst) that can fix nitrogen, converting inert gaseous N2 into ammonium ion (NH4+). Thus, detecting N2-fixation in Sandusky Bay is not atypical. However, N2-production is known to occur via two pathways within the microbial nitrogen cycle (i.e., anaerobic ammonium oxidation and denitrification). Currently, neither of these N2-production pathways are known to be associated with oxygenated surface waters, but rather anoxic lake sediments (denitrification) or groundwater (anaerobic ammonium oxidation). Additional research is needed to resolve the net N2-production observed by the methods employed in this study.</p
Fusion Fall 2019
No full texthttps://kent-islandora.s3.us-east-2.amazonaws.com/node/17633/87702-thumbnail.jp
Remote Sensing of Cyanobacterial and Harmful Algal Blooms in Lake Okeechobee and Biscayne Bay, Florida
No full textCyanobacterial and Harmful Algal Blooms (CyanoHABs) have become a major topic of concern for homeowners and environmental groups in Florida, with blooms occurring in both Lake Okeechobee and Biscayne Bay in prior years. While Biscayne Bay and Lake Okeechobee are distinct water bodies, with different manifestations of the blooms, in both environments CyanoHABs can contain toxins that are harmful to humans and animals, can lead to fish and wildlife kills, as well as disrupt ecosystems. Furthermore, recreational and economic use of the waters of Biscayne Bay and Lake Okeechobee are negatively impacted by these blooms. Monitoring and assessment of the CyanoHABs in both water bodies is a vital aspect of understanding the drivers and impacts of CyanoHAB growth in Florida. Spectral decomposition of satellite remote sensing images of Lake Erie has been shown to be effective at discriminating between in-water constituents, both those related to CyanoHABs, and those that are non-HAB forming. Here we show that the KSU spectral decomposition method is also successful in identifying in-water constituents in Florida waters using images from the Sentinel 3A- Ocean and Land Color Instrument, acquired on 16 July 2017 and 28 July 2018. We identify the CyanoHAB signal in Lake Okeechobee on both days, as well as the sediment and algal signal in Biscayne Bay.</p