Environmental effects on soil NO concentrations and root N uptake in beech and spruce forests

This study aimed to investigate the shifts in net nitrogen (N) uptake and N compounds of fine roots over the vegetation period (i.e., spring, summer, autumn) and correlate this with NO concentration in the soil. Soil NO concentration was measured using gas lysimeters for collection and a chemiluminescence analyzer for quantification. Net N uptake by the roots was determined using the ¹⁵N enrichment technique. N pools were quantified using spectrophotometric techniques. Soil NO concentrations at beech and spruce forest sites were highest in spring (June), and lowest in winter (December). Total N of the roots was similar during the seasons and between the two years under study despite considerable variation of different N compounds. Net N uptake generally increased with higher N supply. Correlation analysis revealed a positive relationship between soil NO concentration and net N uptake only for spruce trees. This relationship seemed to be modulated by environmental factors and tree species.     

Extraction of polyphenols from processed black currant (Ribes nigrum L.) residues

The total phenol and anthocyanin contents of black currant pomace and black currant press residue (BPR) extracts, extracted with formic acid in methanol or with methanol/water/acetic acid, were studied. Anthocyanins and other phenols were identified by means of reversed phase HPLC, and differences between the two plant materials were monitored. In all BPR extracts, phenol levels, determined by the Folin-Ciocalteu method, were 8-9 times higher than in the pomace extracts. Acid hydrolysis liberated a much higher concentration of phenols from the pomace than from the black currant press residue. HPLC analysis revealed that delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside, and cyanidin-3-O-rutinoside were the major anthocyanins and constituted the main phenol class ( approximately 90%) in both types of black currant tissues tested. However, anthocyanins were present in considerably lower amounts in the pomace than in the BPR. In accordance with the total phenol content, the antioxidant activity determined by scavenging of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation, the ABTS(*)(+) assay, showed that BPR extracts prepared by solvent extraction exhibited significantly higher (7-10 times) radical scavenging activity than the pomace extracts, and BPR anthocyanins contributed significantly (74 and 77%) to the observed high radical scavenging capacity of the corresponding extracts.     

Structure determination of partially deuterated carotenoids from intrinsically labeled vegetables by HPLC-MS and 1H NMR

The structures of biosynthetic deuterated carotenoids in labeled vegetables were investigated: (all-E)-lutein and (all-E)-beta-carotene from spinach, and (all-E)-beta-carotene and (all-E)-alpha-carotene from carrots. The vegetables were grown hydroponically using a nutrient solution enriched with deuterium oxide (D(2)O) and were extracted using matrix solid-phase dispersion (MSPD). Deuterium enrichment in the carotenoid molecules was determined by liquid chromatography-mass spectrometry (LC-MS). (all-E)-Lutein and (all-E)-beta-carotene in spinach showed partial deuteration from (2)H(1) to (2)H(12), with the abundance maximum at (2)H(5). (all-E)-beta-Carotene and (all-E)-alpha-carotene from carrots showed partial deuteration from (2)H(1) to (2)H(17), with the abundance maximum at (2)H(11). The (1)H NMR spectra of the four deuterated carotenoids showed additional signals for all methyl groups and decreased signal intensity for the olefinic protons and the methylene protons in the ring. These differences are due to isotopic effects and are based on the substitution of protons by deuterium atoms. The deuteration was distributed randomly throughout the carotenoid molecules.     

Substrate utilization by Aspergillus flavus in inoculated whole corn kernels and isolated tissues

Utilization of the major corn (Zea mays) reserve materials (free saccharides, starch, triglycerides, and zein) was monitored during infection of detached kernels by Aspergillus flavus (A. flavus) over a 12-day period. Inoculated whole kernels were compared to noninoculated kernels. Concentrations of sucrose and raffinose in inoculated seed decreased to nearly zero at 6 days, whereas concentrations of these saccharides in noninoculated seed dropped at a considerably slower rate, and significant levels remained at the end of the incubation period. Triglyceride concentrations remained unchanged in the noninoculated seed but dropped continuously after 2 days in the inoculated seed. Starch and zein concentrations did not change during the 12-day incubation period. Aflatoxin B1 was first detected after 2 days and increased to about 20 microg/g (20,000 ppb) after 12 days. Very low aflatoxin concentrations were detected in the noninoculated seed. Significant concentrations of erythritol, arabitol, and mannitol were produced during infection, with peak concentrations occurring at 8 days. Whole seed and germ tissue appeared to support good fungal growth and aflatoxin production, whereas ground tissues and endosperm did not. A. flavus preferentially utilized saccharides as initial carbon substrates followed by triglycerides. When invading nonwounded corn kernels, the fungus selectively targets the germ tissue where these materials are localized in the highest concentrations.     

Impacts of anthropogenic N additions on nitrogen mineralization from plant litter in exotic annual grasslands

Urban regions of southern California receive up to 45 kg N ha^-1 y^-1 from nitrogen (N) deposition. A field decomposition study was done using ¹⁵N-labelled litter of the widespread exotic annual grass Bromus diandrus to determine whether elevated soil N is strictly from N deposition or whether N mineralization rates from litter are also increased under N deposition. Tissue N and lignin concentrations, which are inversely related in field sites with high and low N deposition, determine the rate at which N moves from plant litter to soil and becomes available to plants. The effect of soil N on N movement from litter to soil was tested by placing litter on high and low N soil in a factorial experiment with two levels of litter N and two levels of soil N. The litter quality changes associated with N deposition resulted in faster rates of N cycling from litter to soil. Concentrations of litter-derived N in total N, NH₄⁺, NO₃⁻, microbial N and organic N were all higher from high N/low lignin litter than from low N/high lignin litter. Litter contributed more N to soil NH₄⁺ and microbial N in high N than low N soil. At the end of the study, N mineralized from high N litter on high N soil accounted for 46% of soil NH₄⁺ and 11% of soil NO₃⁻, compared to 35% of soil NH₄⁺ and 6% of soil NO₃⁻ from low N litter on low N soil. The study showed that in high N deposition areas, elevated inorganic soil N concentrations at the end of the summer N deposition season are a result of N mineralized from plant litter as well as from N deposition.     

Rapid sedimentological and biological assessment of hydrocarbon contaminated sediments

It is possible to rapidly detect the presence of high concentrations of sediment associated hydrocarbons using a sediment profile camera and simultaneously evaluate the general sedimentological and biological character of a contaminated area. In sediments that were heavily contaminated with hydrocarbons from spills and chronic long-term additions the presence of hydrocarbons was seen about 50% of the time in the sediment profile images as unique features, ‘H spots’. The presence of these features was related to the concentration of hydrocarbons in the sediment. In highly contaminated muddy sediments ‘H spots’ were found in images collected at stations that had from 270 to 610 ppt total hydrocarbons. Sedimentological and biological information obtained from the sediment profile images confirmed the impacted nature of Elizabeth River sediments. Sediment profile imaging provide a means of obtaining an overall evaluation of the quality of a habitat and impacts on that habitat from pollution related environmental disturbances. While qualitative, an advantage of sediment profile image data is that they can be evaluated in less than a day and used to quickly locate inclusions of hydrocarbons in the sediments for further quantitative chemical or biological sampling, or mapping of heavily contaminated areas.     

Elemental deposition downwind of a coal-fired power plant

Dry deposition of fly ash emitted by a coal-fired power plant has been calculated using a surface depletion Gaussian plume model. The subject plant is located in the southwestern United States. Soil samples collected downwind of this power plant have been chemically analyzed for selected trace elements (As, B, F, Hg, Se, Sr, U, and V) to determine concentration vs. distance trends. Gaussian plume deposition calculations predict very little increase of trace element concentrations in soils, except for those elements highly concentrated in fly ash emissions compared to soils. Trace element soil concentrations as a function of downwind distance generally confirm these predictions, with the possible exception of Se.     

Frog communities and wetland condition: relationships with grazing by domestic livestock along an Australian floodplain river

Frogs are in decline worldwide, and are known to be sensitive indicators of environmental change. Floodplains of the Murray-Darling Basin in southeastern Australia have been altered in many ways by livestock grazing, by the introduction of exotic fish, and by changes to flooding regimes. These changes have led to declines in wetland condition and hence to the availability of habitat for wetland frogs. This study examined relationships between frogs, wetland condition and livestock grazing intensity at 26 wetlands on the floodplain of the Murrumbidgee River. Frog communities, species richness, and some individual species of frogs declined with increased grazing intensity. Wetland condition also declined with increased grazing intensity, particularly the aquatic vegetation and water quality components. There were clear relationships between frog communities and wetland condition, with several taxa responding to aquatic and fringing vegetation components of wetland condition. Thus, grazing intensity appeared to influence frog communities through changes in wetland habitat quality, particularly the vegetation. Reduced stocking rates may result in improved wetland condition and more diverse frog communities. River management to provide natural seasonal inundation of floodplain wetlands may also enhance wetland condition, frog activity and reproductive success.     

Analysis of virgin olive oil volatiles by a novel electronic nose based on a miniaturized SAW sensor array coupled with SPME enhanced headspace enrichment

A novel electronic nose based on solid-phase microextraction (SPME) coupled with a surface acoustic wave (SAW) sensor array has been used to analyze different quality virgin olive oils. A mathematical model was designed with 37 samples to distinguish lampante from the other virgin olive oils categories (extra-virgin and virgin), because lampante-virgin olive oils cannot be consumed without a previous refining process. The model, successfully validated with a test set of 16 samples, was able to classify 90% of the samples correctly. Misclassifications were explained by SPME-HRGC analyses and a second sensory evaluation.     

Metsulfuron methyl sorption-desorption in field-moist soils

Pesticide sorption coefficients (K(d)) are generally obtained using batch slurry methods. As a consequence, the results may not adequately reflect sorption processes in field-moist or unsaturated soil. The objective of this study was to determine sorption of metsulfuron methyl, a weak acid, in field-moist soils. Experiments were performed using low density (i.e., 0.3 g mL(-)(1)) supercritical fluid carbon dioxide (SF-CO(2)) to convert anionic metsulfuron methyl to the molecular species and remove it from the soil water phase only, thus allowing calculation of sorption coefficients (K(d)) at low water contents. K(d) values for sorption of the metsulfuron methyl molecular species on sandy loam, silt loam, and clay loam soil at 11% water content were 120, 180, and 320 mL g(-)(1), respectively. Using neutral species K(d) values, the pK(a) of metsulfuron methyl, and the pH of the soil, we could successfully predict the K(d) values obtained using the batch slurry technique, which typically has a predominance of anionic species in solution during the sorption characterization. This application of supercritical fluid extraction to determine sorption coefficients, combined with sulfonylureas' pK(a) values and the soil pH, will provide an easy method to predict sorption in soil at different pH levels.