Historical and future development of the tidally averaged transport of sandy sediments in the Scheldt estuary: a 2D exploratory model

Ocean Dynamics - To investigate the historical development of the tidally averaged transport of sandy sediments in the main branch of the Scheldt estuary over the last decades (1950–2013), a...     

The Department of Agriculture and pasture improvement, 1892–1914

Abstract:  Even before 1900, the emphasis in New Zealand agriculture shifted from extensive agriculture to more intensive use of existing farmland through pasture improvement. Examination of the contribution of the Department of Agriculture, which together with the Department of Scientific and Industrial Research activated the later 'grasslands revolution', shows both the extent and the limits of its role in pasture improvement before 1914. It is suggested that until then, the prime agents in this transformation were not Department of Agriculture staff but rather enlightened farmers, with co-operation between them on an equal footing towards the end of the period.     

Measurement of Natural Losses of LNAPL Using CO2 Traps

Efflux of CO₂ above releases of petroleum light nonaqueous phase liquids (LNAPLs) has emerged as a critical parameter for resolving natural losses of LNAPLs and managing LNAPL sites. Current approaches for resolving CO₂ efflux include gradient, flux chamber, and mass balance methods. Herein a new method for measuring CO₂ efflux above LNAPL bodies, referred to as CO₂ traps, is introduced. CO₂ traps involve an upper and a lower solid phase sorbent elements that convert CO₂ gas into solid phase carbonates. The sorbent is placed in an open vertical section of 10 cm ID polyvinyl chloride (PVC) pipe located at grade. The lower sorbent element captures CO₂ released from the subsurface via diffusion and advection. The upper sorbent element prevents atmospheric CO₂ from reaching the lower sorbent element. CO₂ traps provide integral measurement of CO₂ efflux based over the period of deployment, typically 2 to 4 weeks. Favorable attributes of CO₂ traps include simplicity, generation of integral (time averaged) measurement, and a simple means of capturing CO₂ for carbon isotope analysis. Results from open and closed laboratory experiments indicate that CO₂ traps quantitatively capture CO₂. Results from the deployment of 23 CO₂ traps at a former refinery indicate natural loss rates of LNAPL (measured in the fall, likely concurrent with high soil temperatures and consequently high degradation rates) ranging from 13,400 to 130,000 liters per hectare per year (L/Ha/year). A set of field triplicates indicates a coefficient of variation of 18% (resulting from local spatial variations and issues with measurement accuracy).     

The day to night absorption ratio in auroral zone riometer measurements

The day to night ratio in ionospheric radio wave absorption has been studied for College, Alaska using a narrow beam riometer array and computer assisted programming of the data. For the period of 6 November 1967 to 17 April 1968 no significant departure from a ratio of unity was found.     

Complex patterns of catchment solute–discharge relationships for coastal plain rivers

Riverine solute versus discharge (C–Q) relationships provide information about the magnitude and dynamics of material fluxes from landscapes. We analysed long‐term patterns of C–Q relationships for 44 rivers in Florida across a suite of geogenic, nutrient, and organic solutes and investigated land cover, watershed size, and surficial geology as controls on these patterns. Solute concentrations generally exhibited far less variability than did discharge, with coherent solute‐specific behaviours repeated across watersheds. Geogenic solutes generally diluted with increasing discharge, whereas organic solutes generally enriched; patterns for nutrients were highly variable across watersheds, but on average exhibited chemostasis. Despite strong evidence of both geologic and land cover controls on solute flow‐weighted concentrations, these variables were poor predictors of C–Q slopes (β) or relative coefficients of variation (CV_C:CV_Q). CV_C:CV_Q generally increased with watershed size, and wetland area appeared to influence C–Q patterns for base cations and organic solutes. Perhaps most importantly, we observed significant slope breaks in C–Q association in approximately half of our observations, challenging the generality of using single power functions to describe catchment solute export patterns. For all solutes except phosphorus (P), C–Q slopes decreased above statistically identified breaks (slopes for P increased), with breaks consistently at or near median flow (i.e., 50% flow exceedance probability). This common pattern significantly impacts solute load estimates; failing to account for slope breaks overestimates nitrate and total organic carbon loads as much as 125% and underestimates P loads as much as 35%. In addition to challenging generic power‐law characterization of C–Q relationships for these coastal plain rivers, and exploring the load estimate consequences thereof, our study supports emerging insights about watershed hydrochemical behaviours across a wide array of solutes.     

A TEM study of four particles extracted from the Stardust track 80

Abstract— Four particles extracted from track 80 at different penetration depths have been studied by analytical transmission electron microscopy (ATEM). Regardless of their positions within the track, the samples present a comparable microstructure made of a silica rich glassy matrix embedding a large number of small Fe‐Ni‐S inclusions and vesicles. This microstructure is typical of strongly thermally modified particles that were heated and melted during the hypervelocity impact into the aerogel. X‐ray intensity maps show that the particles were made of Mg‐rich silicates (typically 200 nm in diameter) cemented by a fine‐grained matrix enriched in iron sulfide. Bulk compositions of the four particles suggest that the captured dust particle was an aggregate of grains with various iron sulfide fraction and that no extending chemical mixing in the bulb occurred during the deceleration. The bulk S/Fe ratios of the four samples are close to CI and far from the chondritic meteorites from the asteroidal belt, suggesting that the studied particles are compatible with chondritic‐porous interplanetary dust particles or with material coming from a large heliocentric distance for escaping the S depletion.