Lignins and ferulate-coniferyl alcohol cross-coupling products in cereal grains     

Bunzel M  Ralph J  Lu F  Hatfield RD  Steinhart H 《Journal of agricultural and food chemistry》2004,52(21):6496-6502

Plant cell walls containing suberin or lignin in the human diet are conjectured to protect against colon cancer. To confirm the existence of authentic lignin in cereal grain dietary fibers, the DFRC (derivatization followed by reductive cleavage) method was applied to different cereal grain dietary fibers. By cleavage of diagnostic arylglycerol-beta-aryl (beta-O-4) ether linkages and identification of the liberated monolignols, it was ascertained that lignins are truly present in cereal grains. From the ratios of the liberated monolignols coniferyl alcohol and sinapyl alcohol, it is suggested that lignin compositions vary among cereals. Furthermore, dimeric cross-coupling products, comprising ferulate and coniferyl alcohol, were identified in most cereal fibers investigated. These ferulate 4-O-beta- and 8-beta-coniferyl alcohol cross-coupled structures indicate radical cross-coupling of polysaccharides to lignin precursors via ferulate.  相似文献   

The transient response of vegetation to climate change: A potential source of CO2 to the atmosphere     

George A. King  Ronald P. Neilson 《Water, air, and soil pollution》1992,64(1-2):365-383

Global climate change as currently simulated could result in the broad-scale redistribution of vegetation across the planet. Vegetation change could occur through drought-induced dieback and fire. The direct combustion of vegetation and the decay of dead biomass could result in a release of carbon from the biosphere to the atmosphere over a 50- to 150-year time frame. A simple model that tracks dieback and regrowth of extra-tropical forests is used to estimate the possible magnitude of this carbon pulse to the atmosphere. Depending on the climate scenario and model assumptions, the carbon pulse could range from 0 to 3 Gt of C yr^?1. The wide range of pulse estimates is a function of uncertainties in the rate of future vegetation change and in the values of key model parameters.  相似文献   

Some Insights into Atmospheric Processes Involving Urban Sulphur and Nitrogen in and around Hong Kong,SAR     

Sequeira  Ronald 《Water, air, and soil pollution》2002,137(1-4):317-342

The representative mass ratio of the reactive airborne sulphur-to-nitrogen, S/N in the gas and aerosol phases, and in wet and dry deposition over the territory of Hong Kong, SAR,was determined, utilizing available data for the 12 yr period, 1986–1997. Using this information, the representative stoichiometric ratio values for sulphate-to-nitrate in aerosoland in wet and dry depositions were estimated. A limited supplementary data set on various canopy depositions was alsoutilized. This information collectively suggests several basicdifferences in photochemical processes between the urbanatmospheres in and around Hong Kong and the classical, smoggyLos Angeles. This is also supported by the typical diurnal variation of nitrogen oxides in Hong Kong, which suggests a moreefficient photo-oxidation of NO to NO₂ within the territoryand in nearby areas upwind, as compared to further oxidation tothe NO₃ (or nitrate) stage. On the other hand, the relatively low gas-to-particle ratio value estimated for S (～3) relative to N (～26) suggests that the advectedfraction of non-sea salt aerosol sulphate in the territory couldbe considerably greater than the corresponding fraction for nitrate. Finally, significant losses (probably related to sampling) of NH₄-NH₃ in dry deposition could be inferred, while for SO₄ in wet deposition, a moderate enrichment factor of ～2 is observed in relation to SO₄ in aerosol.  相似文献   

the effect of phosphate on the transformation of ferrihydrite into crystalline products in alkaline media     

Paige  C. R.  Snodgrass  W. J.  Nicholson  Ronald V.  Scharer  J. M.  He  Q. H. 《Water, air, and soil pollution》1997,97(3-4):397-412

The presence of phosphate retards the transformation of ferrihydrite into crystalline products. Increasing phosphate from 0 to 1 mole % results in an order of magnitude decrease in the rate of transformation of ferrihydrite at pH 12. Levels of phosphate of ～1 mol % suppress the formation of goethite (α-FeO(OH)) and result in the formation of a product consisting ofη-Fe₂O₃. Higher levels of phosphate result in the ferrihydrite remaining amorphous, even after several hundred hours. Phosphate prevents formation of goethite by hindering the dissolution of ferrihydrite rather than by interfering with nucleation and growth of goethite in solution. The transformation rate of pure ferrihydrite is also strongly inhibited in the presence of dissolved phosphate. This is due to surface complexation. The transformation rate was measured at temperatures of 60 °C and 70 °C. The rate of transformation was found to be described by either (i) a solid-state reaction equation for powdered compacts or (ii) a zero-order reaction controlled by desorption. The transformation of the ferrihydrite matrix was accompanied by the loss of the phosphate trace component. X-ray diffraction indicates that no solid solution involving phosphate substitution intoη-Fe₂O₃ is formed. Transmission electron microphotographs of the original precipitates containing phosphate confirm the presence of the phosphate and demonstrate its involvement in linking together extremely small particles of ferrihydrite.  相似文献   

Sorption and Degradation of Selected Fungicides in the Turfgrass Canopy     

Sigler  William V.  Reicher  Zachary  Throssell  Clark  Bischoff  Marianne  Turco  Ronald F. 《Water, air, and soil pollution》2003,142(1-4):311-326

Microbial degradation of fungicides on leaf surfaces after repeated applications to turfgrass was investigated. Prior andcurrent work in our laboratory has identified two characteristicsof the turfgrass leaf system that may contribute to the enhanceddegradation of fungicides after repeated application to turfgrass:(1) The leaf surface is rich in microorganisms (～10⁸ g^-1 dr wt leaf), and (2) Leaf surface microorganisms may respond to repeated fungicide applications in a manner consistentwith the phenomena of enhanced biodegradation. Field studies wereconducted on ‘Penncross' creeping bentgrass with four fungicidesrepresenting three chemical families applied either two or eight times in one growing season. Biodegradation was estimated using data from both a field study and a parallel laboratory study thatfollowed the fate of ¹⁴C-labelled fungicides. For the laboratory incubations, the locations of the residual ¹⁴C fungicides were estimated using a sequential extraction protocolthat fractionated the materials into three pools: available,retained and bound. Data from both the field and laboratory studyrefuted our hypothesis that enhanced biodegradation would developfollowing repeated applications of the fungicides onto the leafsurface. Our studies support a conclusion that a two-stagephysical sorption process leads to plant incorporation and thiscontrols most of the fungicide's fate. Thus, our data suggestthat microbial activity plays a less important part in theprocess than would be indicated by considering the size of themicrobial population on the leaves.  相似文献   

Removal of Benzene by the Indoor Plant/Substrate Microcosm and Implications for Air Quality     

Orwell  Ralph L.  Wood  Ronald L.  Tarran  Jane  Torpy  Fraser  Burchett  Margaret D. 《Water, air, and soil pollution》2004,157(1-4):193-207

Water, Air, &; Soil Pollution - The quality of the indoor environment has become a major health consideration, since urban-dwellers spend 80-90% of their time indoors, where air pollution can be...  相似文献   

Studies on Nutrient Distribution in Some Zambian Soils with Special Reference to Sulphur Using GIS (Geographic Information Systems) I. Total Sulphur Distribution in Major Zambian Soils     

Togo Tsuji  Austin Mambo  Lackson K. Phiri  Ronald Msoni  Sesele B. Sokotela  Olusegun A. Yerokun 《Soil Science and Plant Nutrition》2005,51(7):935-942

Total sulphur content of some benchmark soils was evaluated by correlating with the contents of soil organic C and amorphous oxides (Al and Fe), and the particle size distribution. An equation model to calculate the content of total soil sulphur was first obtained by regression analysis. Introducing these chemical and physical data of all the map units except for the wetlands into the equation model, the sulphur level on a national scale was estimated for each soil mapping unit in the exploratory soil map of Zambia. Second, the total sulphur content was rated into 3 classes based on the frequency distribution of the total sulphur content in the benchmark soils. Finally, the rated total sulphur content was incorporated into the national soil map database of GIS to produce a map with the total sulphur content of Zambian soils. The extent of each class was calculated and the distribution of the areas was examined in relation to rainfall and soil formation.  相似文献   

Compartmentalization of mercury in biotic components of terrestrial flood plain ecosystems adjacent to the South River AT Waynesboro,VA     

Cocking  Dean  Hayes  Robert  King  Mary Lou  Rohrer  Mary Jane  Thomas  Ronald  Ward  Deanna 《Water, air, and soil pollution》1991,57(1):159-170

Water, Air, & Soil Pollution - Aquatic Hg contamination extending more than 200 km along the South River, South Fork of the Shenandoah River, and Shenandoah River in western VA has been...  相似文献   

Comparison of the acetyl bromide spectrophotometric method with other analytical lignin methods for determining lignin concentration in forage samples     

Fukushima RS  Hatfield RD 《Journal of agricultural and food chemistry》2004,52(12):3713-3720

Present analytical methods to quantify lignin in herbaceous plants are not totally satisfactory. A spectrophotometric method, acetyl bromide soluble lignin (ABSL), has been employed to determine lignin concentration in a range of plant materials. In this work, lignin extracted with acidic dioxane was used to develop standard curves and to calculate the derived linear regression equation (slope equals absorptivity value or extinction coefficient) for determining the lignin concentration of respective cell wall samples. This procedure yielded lignin values that were different from those obtained with Klason lignin, acid detergent acid insoluble lignin, or permanganate lignin procedures. Correlations with in vitro dry matter or cell wall digestibility of samples were highest with data from the spectrophotometric technique. The ABSL method employing as standard lignin extracted with acidic dioxane has the potential to be employed as an analytical method to determine lignin concentration in a range of forage materials. It may be useful in developing a quick and easy method to predict in vitro digestibility on the basis of the total lignin content of a sample.  相似文献   

Sinapate dehydrodimers and sinapate-ferulate heterodimers in cereal dietary fiber     

Bunzel M  Ralph J  Kim H  Lu F  Ralph SA  Marita JM  Hatfield RD  Steinhart H 《Journal of agricultural and food chemistry》2003,51(5):1427-1434

Two 8-8-coupled sinapic acid dehydrodimers and at least three sinapate-ferulate heterodimers have been identified as saponification products from different insoluble and soluble cereal grain dietary fibers. The two 8-8-disinapates were authenticated by comparison of their GC retention times and mass spectra with authentic dehydrodimers synthesized from methyl or ethyl sinapate using two different single-electron metal oxidant systems. The highest amounts (481 microg/g) were found in wild rice insoluble dietary fiber. Model reactions showed that it is unlikely that the dehydrodisinapates detected are artifacts formed from free sinapic acid during the saponification procedure. The dehydrodisinapates presumably derive from radical coupling of sinapate-polymer esters in the cell wall; the radical coupling origin is further confirmed by finding 8-8 and 8-5 (and possibly 8-O-4) sinapate-ferulate cross-products. Sinapates therefore appear to have an analogous role to ferulates in cross-linking polysaccharides in cereal grains and presumably grass cell walls in general.  相似文献