Straightforward Synthesis and Evaluation of Polymeric Sensing Materials for Acetone Detection

This is an Accepted Manuscript of an article published by Macromol. React. Eng. (MRE), of Wiley, accepted on April 2, 2020; doi: 10.1002/mren.202000004Three polymeric materials (polyaniline, polypyrrole, and poly(methyl methacrylate)) have been selected, prepared and evaluated for potential use in acetone sensing (for possible diabetes-related applications). Of the materials studied, polyaniline and polypyrrole showed the most promise. Polypyrrole allowed for more acetone sorption (i.e., higher concentration of acetone sorbed), but did not distinguish between different target analytes (that is, it was not selective). A material’s ability to distinguish between several gas analytes simultaneously (in a gas mixture) is rarely evaluated; selectivity is typically based on a ‘one-analyte-at-a-time’ investigation. However, comparison of acetone sorption (in one experimental test) and interferent sorption (in a complementary experimental test) does not consider interactions that might occur between gas analytes; this motivates the sorption analysis of gas mixtures that is shown in this work. The most promising results were obtained when polyaniline or polypyrrole was exposed to acetone-rich gas mixtures with low amounts of acetaldehyde, ethanol and benzene (interferent gases). Polymer doping using three metal oxides (SnO2, WO3 and ZnO) was also investigated, but metal oxide addition had a limited effect on the sorption performance. This was true for all three metal oxides, regardless of the amount of doping (over the range studied; up to 20 wt%).NSERC; Canada Research Chair (CRC) progra

Ecosystem resistance in the face of climate change: a case study from the freshwater marshes of the Florida Everglades

Shaped by the hydrology of the Kissimmee-Okeechobee-Everglades watershed, the Florida Everglades is composed of a conglomerate of wetland ecosystems that have varying capacities to sequester and store carbon. Hydrology, which is a product of the region’s precipitation and temperature patterns combined with water management policy, drives community composition and productivity. As shifts in both precipitation and air temperature are expected over the next 100 years as a consequence of climate change, CO2 dynamics in the greater Everglades are expected to change. To reduce uncertainties associated with climate change and to explore how projected changes in atmospheric CO2 concentration and climate can alter current CO2 exchange rates in Everglades freshwater marsh ecosystems, we simulated fluxes of carbon among the atmosphere, vegetation, and soil using the DAYCENT model. We explored the effects of low, moderate, and high scenarios for atmospheric CO2 (550, 850, and 950 ppm), mean annual air temperature (þ1, þ2.5, and þ4.28C) and precipitation (2, þ7, and þ14%), as predicted by the IPCC for the year 2100 for the region, on CO2 exchange rates in short- and long-hydroperiod wetland ecosystems. Under 100 years of current climate and atmospheric CO2 concentration, Everglades freshwater marsh ecosystems were estimated to be CO2-neutral. As atmospheric CO2 concentration increased and under climate change projections, there were slight shifts in the start and length of the wet season (1 to þ7 days) and a small enhancement in the sink capacity (by 169 to 573 g C m2 century1 ) occurred at both short- and longhydroperiod ecosystems compared to CO2 dynamics under the current climate regime. Over 100 years, rising temperatures increased net CO2 exchange rates (þ1 to 13 g C m2 century1 ) and shifts in precipitation patterns altered cumulative net carbon uptake by þ13 to 46 g C m2 century1 . While changes in ecosystem structure, species composition, and disturbance regimes were beyond the scope of this research, results do indicate that climate change will produce small changes in CO2 dynamics in Everglades freshwater marsh ecosystems and suggest that the hydrologic regime and oligotrophic conditions of Everglades freshwater marshes lowers the ecosystem sensitivity to climate change. Key word

Carbon isotopic composition of cypress trees from South Florida and changing hydrologic conditions

δ 13C values were determined from cypress tree rings from two different study areas in South Florida. One site is located in the Southeastern Everglades Marsh, where pond cypress ( Taxodium ascendens) was sampled from tree islands (annual tree rings from 1970 to 2000). Bald cypress ( Taxodium distichum) trees were sampled at the other site, located along the Loxahatchee River in a coastal wetland (decadal tree rings from 1830 to 1990). The isotopic time series from both sites display different, location-specific information. The pond cypress isotopic time series has a positive correlation with the total amount of annual precipitation, while the bald cypress data from the Loxahatchee River study area had two different records dependent on the level of saltwater stress. In general, for terrestrial trees growing in a temperate environment, water stress causes an increase in water-use efficiency (WUE) resulting in a relative 13C enrichment. Yet, trees growing in wetland settings in some cases do not respond in the same manner. We propose a conceptual model based on changes in carbon assimilation and isotopic fractionation as controlled by differences in stomatal resistance (water stress) and mesophyll resistance (biochemical and nutrient related) to explain the isotopic records from both sites. With further work and a longer time series, our approach may be tested, and used to reconstruct change in hydroperiods further back in time, and potentially provide a baseline for wetland restoration

Carbon isotopic composition of cypress trees from South Florida and changing hydrologic condition

δ13C values were determined from cypresstree rings from two different study areas in SouthFlorida. One site is located in the Southeastern Everglades Marsh, where pond cypress (Taxodium ascendens) was sampled from tree islands (annual tree rings from 1970 to 2000). Bald cypress (Taxodium distichum) trees were sampled at the other site, located along the Loxahatchee River in a coastal wetland (decadal tree rings from 1830 to 1990). The isotopic time series from both sites display different, location-specific information. The pond cypressisotopic time series has a positive correlation with the total amount of annual precipitation, while the bald cypress data from the Loxahatchee River study area had two different records dependent on the level of saltwater stress. In general, for terrestrial trees growing in a temperate environment, water stress causes an increase in water-use efficiency (WUE) resulting in a relative 13C enrichment. Yet, trees growing in wetland settings in some cases do not respond in the same manner. We propose a conceptual model based on changes in carbon assimilation and isotopic fractionation as controlled by differences in stomatal resistance (water stress) and mesophyll resistance (biochemical and nutrient related) to explain the isotopic records from both sites. With further work and a longer time series, our approach may be tested, and used to reconstruct change in hydroperiods further back in time, and potentially provide a baseline for wetland restoration

Inferring implications of climate change in south Florida hardwood hammocks through analysis of metacommunity structure

Aim In order to explore how variation in regional biogeography would affect forest responses to climate change, we analysed metacommunity structure of trees in natural forest fragments across a boundary between tropical and sub-tropical temperature regimes. We wished to determine whether species assemblages were constrained by periodic cold temperatures, dispersal limitation and/or local processes associated with fragment size, and consider how these influences might affect future species migration and community reassembly. Location Southeastern Florida, USA. Methods We collected complete tree species lists for 144 forest fragments, from our own surveys supplemented by publicly available sources. The resulting species-by-site data matrix was re-ordered based on an ordination that identified the latent environmental axis most responsible for variation in composition, and metacommunity structure was analysed for coherence, turnover and range boundary clumping. Matrix structure was tested for associations with site variables, and with community-aggregated functional traits related to cold tolerance, dispersal limitation and fragment size. Results Forest patch size was the strongest single correlate with composition and species richness, but mean January temperature and a neighbourhood index denoting degree of isolation from other patches contributed significantly to regression models. The species-by-site matrix was highly nested, with trees common to small upland fragments in the Everglades interior representing a distinct subset of the richer assemblages found in sites closer to the coast. Interior forests were smaller, more isolated, and subject to cooler minimum temperatures than more coastal forests, and were comprised primarily of early-successional, animal dispersed species. Main conclusions While warming winter temperatures may relax some constraints on the northward migration of tropical species through the region, sea level rise will raise ground water levels, decreasing the size and number of suitable mesic patches, and increasing their isolation. The result will be a loss in tree species diversity, especially among late-successional, edge-sensitive species