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Acid hydrolysis of sucrose was studied as a method to convert sucrose in sweet sorghum syrup into glucose and fructose before fermentation with the genetically engineered succinic acid-producing Escherichia coli strain AFP184. Successful hydrolysis of sucrose in sweet sorghum syrup was achieved without noticeable formation of degradation products using moderate temperatures, 65–85 °C, with 0.24–0.48 M HCl in less than 30 min. The measured sucrose hydrolysis rates were lower than previously reported for sweet sorghum molasses. The E. coli strain AFP184 consumed all the sugars (glucose and fructose) in the sweet sorghum syrup hydrolysate. The products were predominately succinic and acetic acid. The final concentration of succinic acid was 27 g/L, but the organism was shown to produce higher levels of succinic acid (60 g/L), when grown under optimal conditions on pure glucose. Note that the fermentation results during scale-up should be seen as preliminary, as initial sugar content, aeration, agitation, and duration of initial aerobic growth phase were not optimized. Thus, improved results closer to those experienced with glucose are expected. • Acid hydrolysis converted all sucrose in sweet sorghum syrup into glucose and fructose. • Hydrolysis took place at 65–85 °C with 0.24–0.48 M HCl in less than 30 min. • Genetically engineered succinic acid-producing Escherichia coli consumed all the sugars. • The E. coli strain AFP184 produced 27 g/L of succinic acid from hydrolyzed sweet sorghum syrup. • The E. coli strain AFP184 produced 60 g/L of succinic acid from pure glucose solutions. [ABSTRACT FROM AUTHOR]

We sampled three layers of snow at 16 sites along a 1200 km transect from Nome to Barrow across northwestern Alaska. Samples were analyzed for major element concentrations, specific conductance and pH. Samples from five of the sites were analyzed for trace element concentrations. Pb, Cd, SO42− and non-sea salt SO42− concentrations were significantly higher in layers deposited later in the winter than those deposited earlier. This is consistent with the seasonal increase in atmospheric aerosol loading (arctic haze) that develops as the Arctic polar front expands southward in March and April. Haze contaminant concentrations in the snow pack were as high south of the Brooks Range as they were to the north, suggesting the Brooks Range is not an effective orographic barrier to aerosol transport. Computed yearly non-sea salt SO42− loading rates at the 16 sites ranged from 12 to 281 mg/m2/yr. Elevated concentrations of Hg, Na and Cl were measured near the Arctic Ocean coast but not near the Bering Sea coast. To explain this pattern we suggest that the “effective distance from the coast,” inferred from prevailing wind directions and storm tracks, is critical in governing whether halogen emissions from the ocean are available for photochemical reactions that result in Hg deposition to the snow. [Copyright &y& Elsevier]

Recent advancement in the understanding of snow-microwave interactions has helped to isolate the considerable potential for radar-based retrieval of snow water equivalent (SWE). There are however, few datasets available to address spatial uncertainties, such as the influence of snow microstructure, at scales relevant to space-borne application. In this study we introduce measurements from SnowSAR, an airborne, dual-frequency (9.6 and 17.2 GHz) synthetic aperture radar (SAR), to evaluate high resolution (10 m) backscatter within a snow-covered tundra basin. Coincident in situ surveys at two sites characterize a generally thin snowpack (50 cm) interspersed with deeper drift features. Structure of the snowpack is found to be predominantly wind slab (65%) with smaller proportions of depth hoar underlain (35%). Objective estimates of snow microstructure (exponential correlation length; l ex ), show the slab layers to be 2.8 times smaller than the basal depth hoar. In situ measurements are used to parametrize the Microwave Emission Model of Layered Snowpacks (MEMLS3&a) and compare against collocated SnowSAR backscatter. The evaluation shows a scaling factor (ϕ) between 1.37 and 1.08, when applied to input of l ex , minimizes MEMLS root mean squared error to <1.1 dB. Model sensitivity experiments demonstrate contrasting contributions from wind slab and depth hoar components, where wind rounded microstructures are identified as a strong control on observed backscatter. Weak sensitivity of SnowSAR to spatial variations in SWE is explained by the smaller contributing microstructures of the wind slab. [ABSTRACT FROM AUTHOR]

Abstract: We collected surface snow samples during three years (2004, 2005, and 2007) in Arctic Alaska and from the adjoining frozen Arctic Ocean during springtime in environments that span most Arctic terrains including land, thin and thick first-year sea ice, and multi-year sea ice. The snow was analyzed for Br−, Cl−, SO4 2−, NO3 −, NH4 +, Na+, K+, Mg2+ and Ca2+. Source fractionation processes and atmospheric influences are important modification mechanisms that influence the ions. We find that Cl−, K+ and Mg2+ are primarily sourced by unfractionated sea salt and only show deviations from sea salt composition at low Na+ concentrations. Bromide and Ca2+ are highly influenced by atmospheric processes that are evident at low sea salt tracer concentrations. Calcium enrichments are due to the addition of non-sea salt (nss) Ca2+ from dust and possibly other sources. Bromide enrichments are due to the addition of nss-Br− and bromide depletions are due to bromine activation to the gas phase. Sulfate is affected by source fractionation at high Na+ concentrations and by atmospheric addition at low Na+ concentrations. Nitrate and NH4 + are not correlated with sea salt and show less concentration variability than sea salt ions. Modifications are related to time-integrated air–snow exchange fluxes for Br−, SO4 2− and Ca2+ and are in good agreement with observations of related gas-phase and aerosol species. This work reinforces our understanding of air–snow exchanges and their importance for atmospheric chemistry in the Arctic. [Copyright &y& Elsevier]

The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land–Air–Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations.The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. [Copyright &y& Elsevier]