Chemical Aspects of Fractional Crystallization of Fatty Acid Methyl Esters Produced from Waste Fats

Fractional crystallization of fatty acid methyl esters (FAME) produced from waste cooking oil or animal fats was performed in a laboratory-scale facility. The raw esters and the “winterization” products were analyzed by determining the FAME pattern, iodine and peroxide numbers as well as oxidation stabilities and element concentrations. Fractionation experiments under air and nitrogen were conducted, but no differences concerning oxidative stability were observed. By improvement of the winterization and washing the filtration residue with methanol, the enrichment of saturated FAME in one step was raised up to a technically sufficient rate of 85%. Absorption of oxygen by FAME at different temperatures was measurable. Volatile decomposition products were registrated after heating the FAME at different temperatures. It was shown that antioxidants like butylhydroxytoluene or α-tocopherol were enriched in the phase of unsaturated FAME. This effect obviously affected the oxidative stability of the fraction of saturated FAME during winterization, although no oxidative damage of FAME was detectable at temperatures up to 20°C.     

Aircraft measurements of the microwave scattering signature of the ocean

Microwave scattering signatures of the ocean have been measured over a range of surface wind speeds from 3 m/s to 23.6 m/s using the AAFE RADSCAT scatterometer in an aircraft. Normalized scattering coefficients are presented for vertical and horizontal polarizations as a function of incidence angle (nadir to55deg) and radar azimuth angle (0degto360deg) relative to surface wind direction. For a given radar polarization, incidence angle, and azimuth angle relative to the wind direction, these scattering data exhibit a power law dependence on surface wind speed. The relation of the scattering coefficient to azimuth angle obtained during aircraft circles (antenna conical scans) is anisotropic and suggests that microwave scatterometers can be used to infer both wind speed and direction. These results have been used for the design of the Seasat-A Satellite Scatterometer (SASS) to be flown in 1978 on this first NASA oceanographic satellite.     

Degradation of grass-derived pyrogenic organic material, transport of the residues within a soil column and distribution in soil organic matter fractions during a 28 month microcosm experiment

The microbial recalcitrance of char accumulated after vegetation fires and its transport within a soil column were studied in microcosms using ¹³C- and ¹⁵N-enriched pyrogenic organic material (PyOM). The PyOM from rye grass (Lolium perenne L.) was produced by charring at 350 °C under oxic conditions for 1 and 4 min to examine the impact of the charring degree. After 28 months, ¹³C recovery decreased to values between 62% and 65%, confirming that this material can be attacked by microorganisms and that the degradation occurs rapidly after accumulation of PyOM at the soil surface. The respective ¹⁵N recovery followed the same trend but tended to be higher (between 67% and 80%). Most of the added PyOM isotopic labels were recovered in the particulate organic matter (POM) fraction, containing between 84% and 65% of the added ¹³C and ¹⁵N after the first 2 months, being reduced by half at the end of the experiment. After 1 month, up to 13.8% of the ¹³C label and 12.4% of the ¹⁵N label were detected in the POM-free mineral fractions. This fast association of PyOM with the mineral phase indicates that physical soil properties have to be considered for the elucidation of PyOM stability. Addition of fresh unlabelled grass material as co-substrate resulted in comparable trends as for the pure PyOM but the total recovery of the isotopic labels clearly increased with respect to the amount of mineral-associated PyOM. Between 73% and 82% of the mineral-associated PyOM occurred in the clay separates (<2 μm) for which the highest values were obtained for the experiment with the more intensively charred PyOM and co-substrate addition.In summary, the study demonstrates the degradability of grass-derived PyOM. The addition of fresh plant material as an easily degradable co-substrate promoted the formation of partially decomposed PyOM and subsequently its association with the mineral phase, but did not increase the respective mineralisation rates. Detection of ¹³C and ¹⁵N content at different depths of the microcosm column demonstrated an additional loss of PyOM from top soil by way of mobilisation and transport to deeper horizons. All these processes have to be taken into account in order to obtain a more realistic view about the behaviour of PyOM in environmental systems and for estimation of the C and N sequestration potential.     

A carbon budget for Brazil: Influence of future land-use change

Because of its large area of high C density forests and high deforestation rate, Brazil may play an important role in the global C cycle. The study reported here developed an estimate of Brazil's biotic CO₂-C budget for the period 1990–2010. The analysis used a spreadsheet C accounting model based on three major components: a conceptual model of ecosystem C cycling, a recently completed vegetation classification developed from remote-sensing data, and published estimates of C density for each of the vegetation classes. The dynamics of the model came from estimates of disturbance to ecosystems that release C and estimates of recovery from past disturbance that store C. The model was projected into the future with three alternative estimates of the rate of future land use change. Under all three deforestation scenarios Brazil was a C source in the range of about 3–5 × 10⁹ MgC over the 20-yr study period.The research described in this article has been funded wholly by the U.S. Environmental Protection Agency. This document has been prepared at the EPA National Health and Environmental Effects Research Laboratory in Corvallis, OR, U.S.A., through contract number 68-C8-0006 to ManTech Environmental Research Services, Corp. It has been subjected to the Agency's peer and administrative review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.     

Refractory organic carbon in particle-size fractions of arable soils I: distribution of refractory carbon between the size fractions

Refractory compounds are responsible for the long-term sequestration of organic matter in soil. The aim of this study is to assess the storage of refractory compounds, i.e. compounds with long turnover times, across size separates in arable soils. The contents and distribution of organic carbon (OC) and nitrogen (N) in size fractions were examined for two contrasting treatment types from long-term agroecosystem experiments, i.e. C-depleted and fertilized plots. The soil organic carbon (SOC) pool of the C-depleted plots is considered to be relatively enriched in refractory compounds compared with the SOC in the fertilized counterparts. In two of the three long-term experiments, the relative retention of OC in separates <20 μm was considerably higher than in separates 2000–20 μm (OC contents in depleted plots compared with fertilized plots). Highest residual contents of OC were found in fractions <6 μm. In the third experiment, additionally to the very fine fractions, separates 250–20 μm retained a high proportion of OC. The behavior of N was analogous to that of OC: the highest relative residues in the depleted plots were found in fine separates. These results indicate that in the investigated arable soils, C and N compounds associated with fine separates are most stable. Refractory OC in arable soils may be largely stored in fine particle-size fractions.     

Regional-Scale Differences in Eutrophication Effects on Eelgrass-Associated (<Emphasis Type="Italic">Zostera marina</Emphasis>) Macrofauna

Eutrophication has caused strong shifts from perennial seagrass to opportunistic macroalgae and phytoplankton in many coastal ecosystems worldwide, yet responses of the primary-producer assemblage can vary with regional environmental and nutrient-loading conditions. The wider consequences of this variable primary-producer response on the associated animal community are little known. We used large-scale field surveys across 12 study sites with low or high eutrophication levels in two geographic provinces in Atlantic Canada to examine region-specific responses of macrofauna associated with eelgrass beds. In both regions, abundances of all groups increased with eutrophication, but species richness of mobile fishes and invertebrates decreased. Generally, filter feeders, epibenthic detritivores and some herbivores increased, while more hypoxia sensitive species declined. Small fishes and invertebrate predators increased with eutrophication mirrored by decreases in their prey. Despite similar general trends, our results show distinct shifts in species composition in each geographic region associated with differences in food availability and predation refuge offered by phytoplankton and opportunistic epiphytic or benthic macroalgae as well as tolerance to an increasingly hostile physico-chemical environment. So far, the continued persistence of eelgrass beds at our “highly” eutrophied sites indicates intermediate eutrophication levels with short-term benefits for some species. However, the loss of sensitive species and decrease in species richness highlight that eutrophication has already changed seagrass ecosystems in Atlantic Canada. Our work suggests that mitigating these changes will require regional-scale management.     

Radio Observations of Ions in Comet Hale-Bopp

We present radio observations of HCO⁺, H₃O⁺ and CO⁺ in Hale-Bopp. This revised version was published online in July 2006 with corrections to the Cover Date.