More Like this

1. Florida mangrove saltmarsh reference surface soils

   https://doi.org/10.6073/pasta/0e08cbe07c84488cb7b9dd16669946d0  

   Lewis, David Bruce ( January 2021 , Environmental Data Initiative)

   Site description. This data package consists of data obtained from sampling surface soil (the 0-7.6 cm depth profile) in black mangrove (Avicennia germinans) dominated forest and black needlerush (Juncus roemerianus) saltmarsh along the Gulf of Mexico coastline in peninsular west-central Florida, USA. This location has a subtropical climate with mean daily temperatures ranging from 15.4 °C in January to 27.8 °C in August, and annual precipitation of 1336 mm. Precipitation falls as rain primarily between June and September. Tides are semi-diurnal, with 0.57 m median amplitudes during the year preceding sampling (U.S. NOAA National Ocean Service, Clearwater Beach, Florida, station 8726724). Sea-level rise is 4.0 ± 0.6 mm per year (1973-2020 trend, mean ± 95 % confidence interval, NOAA NOS Clearwater Beach station). The A. germinans mangrove zone is either adjacent to water or fringed on the seaward side by a narrow band of red mangrove (Rhizophora mangle). A near-monoculture of J. roemerianus is often adjacent to and immediately landward of the A. germinans zone. The transition from the mangrove to the J. roemerianus zone is variable in our study area. An abrupt edge between closed-canopy mangrove and J. roemerianus monoculture may extend for up to several hundred meters in some locations, while other stretches of ecotone present a gradual transition where smaller, widely spaced trees are interspersed into the herbaceous marsh. Juncus roemerianus then extends landward to a high marsh patchwork of succulent halophytes (including Salicornia bigellovi, Sesuvium sp., and Batis maritima), scattered dwarf mangrove, and salt pans, followed in turn by upland vegetation that includes Pinus sp. and Serenoa repens. Field design and sample collection. We established three study sites spaced at approximately 5 km intervals along the western coastline of the central Florida peninsula. The sites consisted of the Salt Springs (28.3298°, -82.7274°), Energy Marine Center (28.2903°, -82.7278°), and Green Key (28.2530°, -82.7496°) sites on the Gulf of Mexico coastline in Pasco County, Florida, USA. At each site, we established three plot pairs, each consisting of one saltmarsh plot and one mangrove plot. Plots were 50 m^2 in size. Plots pairs within a site were separated by 230-1070 m, and the mangrove and saltmarsh plots composing a pair were 70-170 m apart. All plot pairs consisted of directly adjacent patches of mangrove forest and J. roemerianus saltmarsh, with the mangrove forests exhibiting a closed canopy and a tree architecture (height 4-6 m, crown width 1.5-3 m). Mangrove plots were located at approximately the midpoint between the seaward edge (water-mangrove interface) and landward edge (mangrove-marsh interface) of the mangrove zone. Saltmarsh plots were located 20-25 m away from any mangrove trees and into the J. roemerianus zone (i.e., landward from the mangrove-marsh interface). Plot pairs were coarsely similar in geomorphic setting, as all were located on the Gulf of Mexico coastline, rather than within major sheltering formations like Tampa Bay, and all plot pairs fit the tide-dominated domain of the Woodroffe classification (Woodroffe, 2002, "Coasts: Form, Process and Evolution", Cambridge University Press), given their conspicuous semi-diurnal tides. There was nevertheless some geomorphic variation, as some plot pairs were directly open to the Gulf of Mexico while others sat behind keys and spits or along small tidal creeks. Our use of a plot-pair approach is intended to control for this geomorphic variation. Plot center elevations (cm above mean sea level, NAVD 88) were estimated by overlaying the plot locations determined with a global positioning system (Garmin GPS 60, Olathe, KS, USA) on a LiDAR-derived bare-earth digital elevation model (Dewberry, Inc., 2019). The digital elevation model had a vertical accuracy of ± 10 cm (95 % CI) and a horizontal accuracy of ± 116 cm (95 % CI). Soil samples were collected via coring at low tide in June 2011. From each plot, we collected a composite soil sample consisting of three discrete 5.1 cm diameter soil cores taken at equidistant points to 7.6 cm depth. Cores were taken by tapping a sleeve into the soil until its top was flush with the soil surface, sliding a hand under the core, and lifting it up. Cores were then capped and transferred on ice to our laboratory at the University of South Florida (Tampa, Florida, USA), where they were combined in plastic zipper bags, and homogenized by hand into plot-level composite samples on the day they were collected. A damp soil subsample was immediately taken from each composite sample to initiate 1 y incubations for determination of active C and N (see below). The remainder of each composite sample was then placed in a drying oven (60 °C) for 1 week with frequent mixing of the soil to prevent aggregation and liberate water. Organic wetland soils are sometimes dried at 70 °C, however high drying temperatures can volatilize non-water liquids and oxidize and decompose organic matter, so 50 °C is also a common drying temperature for organic soils (Gardner 1986, "Methods of Soil Analysis: Part 1", Soil Science Society of America); we accordingly chose 60 °C as a compromise between sufficient water removal and avoidance of non-water mass loss. Bulk density was determined as soil dry mass per core volume (adding back the dry mass equivalent of the damp subsample removed prior to drying). Dried subsamples were obtained for determination of soil organic matter (SOM), mineral texture composition, and extractable and total carbon (C) and nitrogen (N) within the following week. Sample analyses. A dried subsample was apportioned from each composite sample to determine SOM as mass loss on ignition at 550 °C for 4 h. After organic matter was removed from soil via ignition, mineral particle size composition was determined using a combination of wet sieving and density separation in 49 mM (3 %) sodium hexametaphosphate ((NaPO_3)_6) following procedures in Kettler et al. (2001, Soil Science Society of America Journal 65, 849-852). The percentage of dry soil mass composed of silt and clay particles (hereafter, fines) was calculated as the mass lost from dispersed mineral soil after sieving (0.053 mm mesh sieve). Fines could have been slightly underestimated if any clay particles were burned off during the preceding ignition of soil. An additional subsample was taken from each composite sample to determine extractable N and organic C concentrations via 0.5 M potassium sulfate (K_2SO_4) extractions. We combined soil and extractant (ratio of 1 g dry soil:5 mL extractant) in plastic bottles, reciprocally shook the slurry for 1 h at 120 rpm, and then gravity filtered it through Fisher G6 (1.6 μm pore size) glass fiber filters, followed by colorimetric detection of nitrite (NO_2^-) + nitrate (NO_3^-) and ammonium (NH_4^+) in the filtrate (Hood Nowotny et al., 2010,Soil Science Society of America Journal 74, 1018-1027) using a microplate spectrophotometer (Biotek Epoch, Winooski, VT, USA). Filtrate was also analyzed for dissolved organic C (referred to hereafter as extractable organic C) and total dissolved N via combustion and oxidation followed by detection of the evolved CO_2 and N oxide gases on a Formacs HT TOC/TN analyzer (Skalar, Breda, The Netherlands). Extractable organic N was then computed as total dissolved N in filtrate minus extractable mineral N (itself the sum of extractable NH_4-N and NO_2-N + NO_3-N). We determined soil total C and N from dried, milled subsamples subjected to elemental analysis (ECS 4010, Costech, Inc., Valencia, CA, USA) at the University of South Florida Stable Isotope Laboratory. Median concentration of inorganic C in unvegetated surface soil at our sites is 0.5 % of soil mass (Anderson, 2019, Univ. of South Florida M.S. thesis via methods in Wang et al., 2011, Environmental Monitoring and Assessment 174, 241-257). Inorganic C concentrations are likely even lower in our samples from under vegetation, where organic matter would dilute the contribution of inorganic C to soil mass. Nevertheless, the presence of a small inorganic C pool in our soils may be counted in the total C values we report. Extractable organic C is necessarily of organic C origin given the method (sparging with HCl) used in detection. Active C and N represent the fractions of organic C and N that are mineralizable by soil microorganisms under aerobic conditions in long-term soil incubations. To quantify active C and N, 60 g of field-moist soil were apportioned from each composite sample, placed in a filtration apparatus, and incubated in the dark at 25 °C and field capacity moisture for 365 d (as in Lewis et al., 2014, Ecosphere 5, art59). Moisture levels were maintained by frequently weighing incubated soil and wetting them up to target mass. Daily CO_2 flux was quantified on 29 occasions at 0.5-3 week intervals during the incubation period (with shorter intervals earlier in the incubation), and these per day flux rates were integrated over the 365 d period to compute an estimate of active C. Observations of per day flux were made by sealing samples overnight in airtight chambers fitted with septa and quantifying headspace CO_2 accumulation by injecting headspace samples (obtained through the septa via needle and syringe) into an infrared gas analyzer (PP Systems EGM 4, Amesbury, MA, USA). To estimate active N, each incubated sample was leached with a C and N free, 35 psu solution containing micronutrients (Nadelhoffer, 1990, Soil Science Society of America Journal 54, 411-415) on 19 occasions at increasing 1-6 week intervals during the 365 d incubation, and then extracted in 0.5 M K_2SO_4 at the end of the incubation in order to remove any residual mineral N. Active N was then quantified as the total mass of mineral N leached and extracted. Mineral N in leached and extracted solutions was detected as NH_4-N and NO_2-N + NO_3-N via colorimetry as above. This incubation technique precludes new C and N inputs and persistently leaches mineral N, forcing microorganisms to meet demand by mineralizing existing pools, and thereby directly assays the potential activity of soil organic C and N pools present at the time of soil sampling. Because this analysis commences with disrupting soil physical structure, it is biased toward higher estimates of active fractions. Calculations. Non-mobile C and N fractions were computed as total C and N concentrations minus the extractable and active fractions of each element. This data package reports surface-soil constituents (moisture, fines, SOM, and C and N pools and fractions) in both gravimetric units (mass constituent / mass soil) and areal units (mass constituent / soil surface area integrated through 7.6 cm soil depth, the depth of sampling). Areal concentrations were computed as X × D × 7.6, where X is the gravimetric concentration of a soil constituent, D is soil bulk density (g dry soil / cm^3), and 7.6 is the sampling depth in cm. 

   more » « less
2. A green solvent-to-polymer upgrading approach to water-soluble LCST poly( N -substituted lactamide acrylate)s

   https://doi.org/10.1039/D2GC02780A  

   Palà, Marc ; El Khannaji, Hafssa ; Garay-Sarmiento, Manuela ; Ronda, Juan Carlos ; Cádiz, Virginia ; Galià, Marina ; Percec, Virgil ; Rodriguez-Emmenegger, César ; Lligadas, Gerard ( October 2022 , Green Chemistry)

   We report a green solvent-to-polymer upgrading transformation of chemicals of the lactic acid portfolio into water-soluble lower critical solution temperature (LCST)-type acrylic polymers. Aqueous Cu(0)-mediated living radical polymerization (SET-LRP) was utilized for the rapid synthesis of N -substituted lactamide-type homo and random acrylic copolymers under mild conditions. A particularly unique aspect of this work is that the water-soluble monomers and the SET-LRP initiator used to produce the corresponding polymers were synthesized from biorenewable and non-toxic solvents, namely natural ethyl lactate and BASF's Agnique® AMD 3L ( N , N -dimethyl lactamide, DML). The pre-disproportionation of Cu( i )Br in the presence of tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) in water generated nascent Cu(0) and Cu( ii ) complexes that facilitated the fast polymerization of N -tetrahydrofurfuryl lactamide and N , N -dimethyl lactamide acrylate monomers (THFLA and DMLA, respectively) up to near-quantitative conversion with excellent control over molecular weight (5000 < M n < 83 000) and dispersity (1.05 < Đ < 1.16). Interestingly, poly(THFLA) showed a degree of polymerization and concentration dependent LCST behavior, which can be fine-tuned ( T cp = 12–62 °C) through random copolymerization with the more hydrophilic DMLA monomer. Finally, covalent cross-linking of these polymers resulted in a new family of thermo-responsive hydrogels with excellent biocompatibility and tunable swelling and LCST transition. These illustrate the versatility of these neoteric green polymers in the preparation of smart and biocompatible soft materials. 

   more » « less
3. The structural evolution of poly(ethylene terephthalate) oligomers produced via glycolysis depolymerization

   https://doi.org/10.1039/D2TA07467B  

   Moncada, Joshua ; Dadmun, Mark D. ( February 2023 , Journal of Materials Chemistry A)

   Polymeric materials have become an integral part of our society, and their high demand has created a large quantity of polymers that end up in the waste stream. For instance, poly(ethylene terephthalate) (PET) is widely used in a broad range of applications, where the chemical recycling of PET is of growing interest. Most methods focus on the complete depolymerization of PET to the monomer, however pushing the equilibrium reaction to the monomer is time- and energy-intensive. We hypothesize that by intercepting intermediates in the depolymerization, telechelic oligomers can be captured that can also be used as reactants to produce value-added goods. To this end, the effect of reaction type, catalyst loading, reaction time, and temperature on the evolution of the product chain structure and yield of the glycolysis depolymerization of PET is studied. For a heterogeneous reaction at lower temperatures (165 °C), the rate of depolymerization is sufficiently slow to offer access to a broad range of molecular weight products (3000–10 000 Daltons) at a high yield (nearly 100%). At higher heterogeneous reaction temperatures (175 and 185 °C), the reaction rate increases, producing oligomers of a narrower molecular weight range (2000–5000 Daltons) with significant loss of the original PET, up to 40%, as water soluble products. In the heterogeneous reaction, little change was observed when altering the catalyst loading at higher temperatures, but lower temperatures and decreased catalyst loading produce accessible higher molecular weight oligomers. Homogeneous catalysis of the glycolysis reactions increases the rate of depolymerization, such that it is difficult to isolate oligomers with M n > 1000 Daltons. The oligomers from heterogeneous reactions were used as reactants to form block copolymers with ethylene glycol, exemplifying their use as precursors in the production of value-added materials. These experiments, therefore, offer crucial insight into how reaction conditions can be readily tuned to produce target telechelic oligomers of PET. 

   more » « less
4. Rapidly-cured isosorbide-based cross-linked polycarbonate elastomers

   https://doi.org/10.1039/c5py01659b  

   Kristufek, Tyler S. ; Kristufek, Samantha L. ; Link, Lauren A. ; Weems, Andrew C. ; Khan, Sarosh ; Lim, Soon-Mi ; Lonnecker, Alexander T. ; Raymond, Jeffery E. ; Maitland, Duncan J. ; Wooley, Karen L. ( January 2016 , Polymer Chemistry)

   The rapid synthesis of an optically-transparent, flexible elastomer was performed utilizing the naturally-derived source, isosorbide. A novel monomer based on isosorbide (isosorbide dialloc, IDA) was prepared by installing carbonate functionalities along with external olefins for use in thiol–ene click chemistry. Cross-linked networks were created using the commercially-available cross-linker, trimethylolpropane tris(3-mercaptopropionate) (TMPTMP) and resulted in IDA- co -TMPTMP, an optically-transparent elastomer. Systematically, IDA- co -TMPTMP networks were synthesized using a photoinitiator, a UV cure time of one minute and varied post cure times (0–24 h, 125 mm Hg) at 100 °C to observe effects on mechanical, thermal and surface alterations. The mechanical properties also had limited changes with post cure time, including a modulus at 25 °C of 1.9–2.8 MPa and an elongation of 220–344%. The thermal decomposition temperatures of the networks were consistent, ca. 320 °C, while the glass transition temperature remained below room temperature for all samples. A cell viability assay and fluorescence imaging with adherent cells are also reported in this study to show the potential of the material as a biomedical substrate. A degradation study for 60 days resulted in 8.3 ± 3.5% and 97.7 ± 0.3% mass remaining under accelerated (1 M NaOH, 60 °C) and biological conditions (pH 7.4 PBS at 37 °C), respectively. This quickly-synthesized material has the potential to hydrolytically degrade into biologically-benign and environmentally-friendly by-products and may be utilized in renewable plastics and/or bioelastomer applications. 

   more » « less
5. Nanoscale layers of precise ion-containing polyamides with lithiated phenyl sulfonate in the polymer backbone

   https://doi.org/10.1039/d2py00802e  

   Park, Jinseok ; Easterling, Charles P. ; Armstrong, Christopher C. ; Huber, Dale L. ; Bowman, Jared I. ; Sumerlin, Brent S. ; Winey, Karen I. ; Taylor, Mercedes K. ( October 2022 , Polymer Chemistry)

   We investigate a new series of precise ion-containing polyamide sulfonates (PAS x Li), where a short polar block precisely alternates with a non-polar block of aliphatic carbons ( x = 4, 5, 10, or 16) to form an alternating (AB) n multiblock architecture. The polar block includes a lithiated phenyl sulfonate in the polymer backbone. These PAS x Li polymers were synthesized via polycondensation of diaminobenzenesulfonic acid and alkyl diacids (or alkyl diacyl chlorides) with x -carbons, containing amide bonds at the block linkages. The para - and meta -substituted diaminobenzene monomers led to polymer analogs denoted p PAS x Li and m PAS x Li, respectively. When x ≤ 10, the para -substituted diamine monomer yields multiblock copolymers of a higher degree of polymerization than the meta -substituted isomer, due to the greater electron-withdrawing effect of the meta -substituted monomer. The PAS x Li polymers exhibit excellent thermal stability with less than 5% mass loss at 300 °C and the glass transition temperatures ( T g ) decrease with increasing hydrocarbon block length ( x ). Using the random phase approximation, the Flory–Huggins interaction parameter ( χ ) is determined for p PAS10Li, and χ (260 °C) ∼ 2.92 reveals high incompatibility between the polar ionic and non-polar hydrocarbon blocks. The polymer with the longest hydrocarbon block, p PAS16Li, is semicrystalline and forms well-defined nanoscale layers with a spacing of ∼2.7 nm. Relative to previously studied polyester multiblock copolymers, the amide groups and aromatic rings permit the nanoscale layers to persist up to 250 °C and thus increase the stability range for ordered morphologies in precise ion-containing multiblock copolymers. 

   more » « less