- ItemPhysiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh-Tidal Channel Interface(Journal of Geophysical Research: Biogeosciences, 2023-06-06) Fettrow, Sean; Jeppi, Virginia; Wozniak, Andrew; Vargas, Rodrigo; Michael, Holly; Seyfferth, Angelia L.Tidal channels are biogeochemical hotspots that horizontally exchange carbon (C) with marsh platforms, but the physiochemical drivers controlling these dynamics are poorly understood. We hypothesized that C-bearing iron (Fe) oxides precipitate and immobilize dissolved organic carbon (DOC) during ebb tide as the soils oxygenate, and dissolve into the porewater during flood tide, promoting transport to the channel. The hydraulic gradient physically controls how these solutes are horizontally exchanged across the marsh platform-tidal channel interface; we hypothesized that this gradient alters the concentration and source of C being exchanged. We further hypothesized that trace soil gases (i.e., CO2, CH4, dimethyl sulfide) are pushed out of the channel bank as the groundwater rises. To test these hypotheses, we measured porewater, surface water, and soil trace gases over two 24-hr monitoring campaigns (i.e., summer and spring) in a mesohaline tidal marsh. We found that Fe2+ and DOC were positively related during flood tide but not during ebb tide in spring when soils were more oxidized. This finding shows evidence for the formation and dissolution of C-bearing Fe oxides across a tidal cycle. In addition, the tidal channel contained significantly (p < 0.05) more terrestrial-like DOC when the hydraulic gradient was driving flow toward the channel. In comparison, the channel water was saltier and contained significantly (p < 0.05) more marine-like DOC when the hydraulic gradient reversed direction. Trace gas fluxes increased with rising groundwater levels, particularly dimethyl sulfide. These findings suggest multiple physiochemical mechanisms controlling the horizontal exchange of C at the marsh platform-tidal channel interface. Plain Language Summary Tidal salt marshes store large amounts of carbon belowground in soils, but there is also a significant amount of carbon flowing into and out of these ecosystems via tidal channels. We investigated the carbon flowing between the channel bank and surface water in a salt marsh in Delaware. We found that soil minerals (i.e., iron oxides) control the mobility of carbon as iron oxides retain carbon during ebb tides and release carbon during flood tides as the minerals dissolve. The gradient between the groundwater and surface water elevation (i.e., hydraulic gradient) controls the flow direction for dissolved carbon, altering the concentration and source of carbon found in the tidal channel across tidal cycles. In addition, gases trapped in channel banks are pushed out of the soils as the tide rises. These findings will improve our understanding of carbon cycles in these critical carbon sinks. Key Points - Physiochemical mechanisms control horizontal exchange of carbon across marsh-tidal channel interfaces, affecting lateral carbon flux - Dissolution and reprecipitation of carbon-bearing Fe oxides during flood and ebb tides control the horizontal mobility of carbon - Hydraulic gradients control the carbon character in the tidal channel, and rising tides push greenhouse gases out of the channel bank
- ItemHydrothermal Leaching of Amylose from Native, Oxidized and Heat-Treated Starches(Processes, 2023-05-11) Nikolenko, Mykola V.; Myrhorodska-Terentieva, Viktoriia D.; Sakhno, Yuriy; Jaisi, Deb P.; Likozar, Blaž; Kostyniuk, AndriiThe kinetics of amylose leaching in hot, excess water from native, oxidized-by-potassium permanganate and heat-treated potato starch at temperatures of 62–90 °C was investigated in isothermal conditions. For the first time, it was proposed to describe the kinetic data by the Kroger–Ziegler equation. It was found that for native starch in the range of 62–70 °C, the activation energy of the amylose leaching process is 192.3 kJ/mol, and at a temperature of 80–90 °C, it decreases to 22 kJ/mol. Similar patterns were established for modified starches. In the kinetic mode, the activation energy was 102.5 kJ/mol for oxidized starch and 44.7 and 82.5 kJ/mol for heat-treated starches at a temperature of 135 °C for 2.5 and 5 h. In the diffusion mode, it was: 18.7 kJ/mol for oxidized and 16.2 and 18.9 kJ/mol for heat-treated starches for 2.5 and 5 h, respectively. It is shown that the consideration of amylose leaching as a heterogeneous pseudochemical process makes it possible to explain the change in the activation energy with increasing temperature by the transition of the leaching process from the kinetic to the diffusion mode. As such a pseudochemical process, it is proposed to consider the breaking of multiple hydrogen bonds between amylose macromolecules. The change in the activation energies of amylose extraction from modified starches is explained by the change in the degree of amylose polymerization. Thin-layer chromatography was used to compare the molecular weight distributions of the resulting modified amylose samples. FTIR spectroscopy and thermal methods of analysis were used to study the transformations of starch during heat treatment.
- ItemScanning X-ray fluorescence spectroscopy and micro-X-ray absorption near-edge structure analysis as a guiding tool for the conservation treatment of two eighteenth-century Philadelphian portraits(X-Ray Spectrometry, 2023-04-02) Porell, Mina; Cushman, Matthew; Fischel, Jason S. T.; Fischel, Matthew H. H.; Sparks, Donald L.; Grayburn, RosieAn in-depth technical examination and conservation treatment of paintings by William Williams (Bristol 1727–1791 Bristol) has shed light on the artist's materials and technique. This investigation centered primarily on Williams's two 1766 portraits of William and David Hall. The paintings are considered the earliest life-sized, full-length portraits executed in the Philadelphia area. The analysis of the artist's palette indicated deliberate choices in the use of orpiment (As2S3). The mineral's tendency to oxidize to colorless and water-soluble arsenic oxides likely caused color changes and degraded organic binder in the orpiment-rich areas. μ-XANES revealed orpiment photodegradation to arsenate species at the paint surface, with migration to the ground layers. Just below the paint surface, arsenic remains bound primarily as arsenite, with some associated with sulfur as orpiment. This As distribution suggests that the paint is liable to further degradation by photooxidation and use of moisture would be detrimental. Given this treatment-critical degradation phenomenon, it was important to identify all arsenic-containing areas of both portraits. Scanning XRF allowed rapid and accurate collection of maps from both portraits. Elemental maps of arsenic identified the orpiment-rich areas of the painting, which would be susceptible to further degradation upon exposure to water during treatment. An aqueous adhesive was necessary to consolidate the cupped paint of the glue-paste lined paintings. The arsenic maps guided the use of two different consolidants–BEVA 371 for the water-sensitive orpiment-rich paint and sturgeon glue for all other areas, striking a compromise between esthetic improvement and long term preservation.
- ItemEffect of core cultivation, fertility, and plant growth regulators on recovery of voided creeping bentgrass greens canopies following annual bluegrass control via methiozolin(Weed Technology, 2023-04-13) Venner, Katelyn A.; Ervin, Erik; Koo, Suk-Jin; Peppers, John M.; Askew, Shawn D.Methiozolin is commonly used for the safe and selective removal of annual bluegrass from creeping bentgrass golf greens. Studies were conducted in 2013 and 2014 with the objective of assessing fertility programs consisting of synthetic fertilizers and biostimulants, with and without the plant growth regulator trinexapac-ethyl, to aid putting green canopy recovery following annual bluegrass removal via methiozolin. Additional studies were conducted to compare recovery of creeping bentgrass following an aggressive core aerification event with fertility programs with and without methiozolin. In all cases, the addition of 7 kg ha−1 of N-P-K from fertilizer or biostimulant biweekly to greens increased turfgrass recovery time by 1 to 3 wk compared to a standard green’s fertility program alone. Creeping bentgrass treated with biostimulants recovered equivalent to or quicker than creeping bentgrass treated with synthetic fertilizer (SF) in all cases. In the presence of methiozolin treatments, trinexapac-ethyl reduced time to 90% recovery (T90) by 0.25 to 0.5 wk at two locations, and increased T90 recovery time by 0.1 wk at one location. Otherwise, plots treated with SF plus trinexapac-ethyl were equivalent to plots treated with SF only. Methiozolin slowed turfgrass recovery time at one location where severe drought stress occurred but not at the other location that did not experience drought stress. These results suggest that turf managers should increase fertilizer treatments but will not need to discontinue trinexapac-ethyl use to maximize creeping bentgrass recovery following annual bluegrass control with methiozolin. These data also suggest that methiozolin has the potential to negatively affect creeping bentgrass recovery when drought stress is experienced.
- ItemRice husk and charred husk amendments increase porewater and plant Si but water management determines grain As and Cd concentration(Plant and Soil, 2022-03-09) Linam, Franklin; Limmer, Matt A.; Tappero, Ryan; Seyfferth, Angelia L.Purpose Rice is a staple crop worldwide and a silicon (Si) hyperaccumulator with Si levels reaching 5–10% of its mass; this can result in desilication and Si-deficiency if plant residues are not managed correctly. Rice is also uniquely subject to arsenic (As) and cadmium (Cd) contamination depending on soil conditions. Our goal is to quantify the effects of rice husk (a Si-rich milling byproduct) amendments and different water management strategies on rice uptake of Si, As, and Cd. Methods We employed 4 husk amendment treatments: Control (no husk), Husk (untreated husk), Biochar (husk pyrolyzed at 450 °C), and CharSil (husk combusted at > 1000 °C). Each of these amendments was studied under nonflooded, alternate wetting and drying (AWD), and flooded water management in a pot study. Porewater chemistry and mature plant elemental composition were measured. Results Husk and Biochar treatments, along with flooding, increased porewater and plant Si. Vegetative tissue As decreased with increasing porewater Si, but grain As and plant Cd were primarily controlled by water management. Grain As and Cd were inversely correlated and are simultaneously minimized in a redox potential (Eh) range of 225–275 mV in the studied soil. Ferrihydrite in root iron plaque decreased As translocation from porewater to grain, but amendments were not able to increase plaque ferrihydrite content. Conclusion We conclude moderate husk amendment rates (i.e., 4 years’ worth) with minimal pretreatment strongly increases rice Si content but may not be sufficient to decrease grain As in low Si and As soil.