Journal of Environmental Quality
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Comparative Analysis of Partial Structures of a Peat Humic and Fulvic Acid Using One‐ and Two‐Dimensional Nuclear Magnetic Resonance Spectroscopy ABSTRACT Nuclear magnetic resonance (NMR) resonance integrals obtained from one‐dimensional NMR spectra provide semiquantitative contents of humic constituents with limited resolution in structural detail. When supplemented by connectivity information available from homo‐ and heteronuclear two‐dimensional NMR spectra a more reliable assignment of humic substructures becomes available. This is demonstrated with a comparative one‐ and two‐dimensional NMR analysis of a fulvic and a humic acid obtained from Eriophorum peat. An example of a detailed analysis of the proton chemical shift region normally attributed to carbohydrates shows substantial contributions from amino acids, amino and desoxy sugars, and highly oxidized aliphatic chains of intermediate length. The very good resolution of structural detail by a combined analysis of all NMR spectra shows that the effect of the fractionation procedure on the composition and chemical structure of humic materials is very significant. The comparison of the partial structures comprising humic acid (HA) and fulvic acid (FA) of the peat humic materials studied indicates that FA is diagenetically downstream of HA, favoring the biopolymer degradation (BD) model of humification.
Journal of Environmental Quality - Tập 31 Số 2 - Trang 375-387 - 2002
Atmospheric Sulfur Deposition, Neutralization, and Ion Leaching in Two Deciduous Forest Ecosystems Abstract In the 1981 water year, bulk precipitation was primarily a solution of dilute H2 SO4 , and SO4 2‐ was the dominant anion in tbroughfall and soil leachates in two eastern Tennessee deciduous forests. Ecosystem inputs of SO4 2‐ , which included dry deposition of forest canopies, may have been up to 40% greater than input estimates based on atmospheric deposition sampling in open areas. Volume‐weighted mean annual pH of bulk precipitation was 4.3; of throughfall 4.8; and of leachates from O2, A1, and B21 soil horizons about 6.0. At both sites, strong acids in precipitation were largely neutralized prior to rainwater's infiltration into mineral soil. Base cations that exchanged with H+ (hydrogen ions) in acid precipitation were almost entirely supplied by forest canopies and litter layers, and did not come directly from exchangeable mineral soil pools. Annual fluxes of HCO3 − alkalinity from B21 horizons, about 0.42 and 0.51 kmol (−) ha−1 (keq ha−1 ) at the two sites, indicated that the natural H+ input from the partial ionization of H2 CO3 was of similar magnitude to H+ input in bulk precipitation in 1981 [0.60 kmol(+)ha−1 ]. However, even in these infertile soils with low cation exchange capacities (CEC) [<7.2 cmol (NH4 + ) kg−1 (meq/100 g) in surface 50‐ or 80‐cm soil], exchangeable bases were more than two orders of magnitude greater than annual H+ input in bulk precipitation, and represented a substantial reserve for base cations in canopies and litter layers that exchanged with H+ in acid rain. Furthermore, inputs of H+ from acid precipitation were equal to about 0.4% of the base cations that are biologically cycling and immediately available in these ecosystems. Although poorly quantified, mineral weathering and deep rooting will supply, over time, substantial amounts of additional base cations for biologic cycling. Both soils are base‐poor Udults and classified as sensitive to acid rain, but the deposition, cycling, and soil data presented in this report indicate that leaching remains a process affecting cation reserves and soil development only over the very long term.
Journal of Environmental Quality - Tập 12 Số 2 - Trang 263-270 - 1983
Mineralizable Nitrogen in Broiler Litter: I. Effect of Selected Litter Chemical Characteristics Abstract Broiler (chicken, Gallus gallus domesticus ) litter is a mixture of manure and bedding material that is generated in large amounts by the broiler industry. This litter is typically applied to land as fertilizer, at rates estimated to supply adequate N. Estimation of rates is currently hampered by the lack of rapid methods to determine mineralizable N in BL. This study was conducted to compare the kinetics of N mineralization of 15 BL samples, and to evaluate selected chemical characteristics of the litter as predictors of mineralizable N. Broiler litter samples were mixed with samples of Cowarts soil (150 mg organic N kg−1 soil, −0.02 MPa) and incubated at 25°C for 112 d. Cumulative net N mineralized was fitted to a two‐pool, first‐order model, to determine the size of fast and slow pools of mineralizable N. The fast N pool varied from 116 to 569 g N kg−1 organic N (ON), and could be predicted from uric acid‐N concentration in the litter (R 2 = 0.92). The size of the slow N pool did not vary significantly among BL samples; (309 ± 94 g N kg−1 ON). Total mineralizable N (fast + slow N pools) ranged from 465 to 868 g N kg−1 ON, and could be predicted from uric acid‐N and total N concentrations (R 2 = 0.91), or from uric acid‐N concentration and C/N of the litter (R 2 = 0.95). The simplicity of the chemical indices involved should make this approach attractive to estimate mineralizable N in BL.
Journal of Environmental Quality - Tập 26 Số 6 - Trang 1672-1679 - 1997
Greenhouse Gas Emissions and Management Practices that Affect Emissions in US Rice Systems Previous reviews have quantified factors affecting greenhouse gas (GHG) emissions from Asian rice (Oryza sativa L.) systems, but not from rice systems typical for the United States, which often vary considerably particularly in practices (i.e., water and carbon management) that affect emissions. Using meta‐analytic and regression approaches, existing data from the United States were examined to quantify GHG emissions and major practices affecting emissions. Due to different production practices, major rice production regions were defined as the mid‐South (Arkansas, Texas, Louisiana, Mississippi, and Missouri) and California, with emissions being evaluated separately. Average growing season CH4 emissions for the mid‐South and California were 194 (95% confidence interval [CI] = 129–260) and 218 kg CH4 ha−1 season−1 (95% CI = 153–284), respectively. Growing season N2 O emissions were similar between regions (0.14 kg N2 O ha−1 season−1 ). Ratoon cropping (allowing an additional harvestable crop to grow from stubble after the initial harvest), common along the Gulf Coast of the mid‐South, had average CH4 emissions of 540 kg CH4 ha−1 season−1 (95% CI = 465–614). Water and residue management practices such as alternate wetting and drying, and stand establishment method (water vs. dry seeding), and the amount of residue from the previous crop had the largest effect on growing season CH4 emissions. However, soil texture, sulfate additions, and cultivar selection also affected growing season CH4 emissions. This analysis can be used for the development of tools to estimate and mitigate GHG emissions from US rice systems and other similarly mechanized systems in temperate regions. Core Ideas
Emissions of CH4 and N2 O were quantified for US rice systems using a meta‐analysis. Emissions were determined for both the growing and fallow seasons. We assessed the major management practices affecting emissions. Analysis can be used to develop a tool for quantifying emissions from rice fields.
Journal of Environmental Quality - Tập 47 Số 3 - Trang 395-409 - 2018
Seasonal Methane and Nitrous Oxide Emissions of Several Rice Cultivars in Direct-Seeded Systems
Journal of Environmental Quality - Tập 44 Số 1 - Trang 103-114 - 2015
Optimal Fertilizer Nitrogen Rates and Yield-Scaled Global Warming Potential in Drill Seeded Rice
Journal of Environmental Quality - Tập 42 Số 6 - Trang 1623-1634 - 2013
Adsorption of Arsenate and Arsenite on Ferrihydrite in the Presence and Absence of Dissolved Organic Carbon ABSTRACT The adsorption of As(V) and As(III) on synthetic two‐line ferrihydrite in the presence and absence of a peat humic acid (HAp ), Suwannee River fulvic acid (FA), or citric acid (CA) was investigated. Previous work with goethite has demonstrated the ability of dissolved organic carbon (DOC) to decrease As(V) and As(III) adsorption. The results obtained demonstrate that As(V) adsorption on ferrihydrite was decreased only in the presence of CA. Arsenate decreased the adsorption of all organic acids except HAp Both FA and CA reduced As(III) adsorption on ferrihydrite, while HAp had no effect. Fulvic and citric acid adsorption on ferrihydrite was decreased in the presence of As(III); however, FA and CA adsorption increased at lower pH, which was consistent with decreased As(III) adsorption. Peat humic acid did not decrease As(III) adsorption, and we believe that the adsorption process of HAp and As(III) and As(V) on ferrihydrite are independent of each other. Previously, we observed that As(V) adsorption on goethite decreased in the presence of HAp > FA > CA, while As(III) adsorption on goethite was decreased similarly to that on ferrihydrite in the presence of CA > FA ≈ HAp , yet As(III) adsorption on ferrihydrite was greater than on goethite. The observed differences between this study and the earlier study on goethite are believed to be an intricate function of ferrihydrite's surface characteristics, which affect the mechanisms of adsorption and hence the affinity of organic acids such as HAp , FA, and CA for the ferrihydrite surface. As such, the adsorption of DOCs to ferrihydrite are assumed to be less favorable and to occur with a fewer number of ligands, resulting in lower surface coverage of weaker bond strength.
Journal of Environmental Quality - Tập 31 Số 4 - Trang 1115-1123 - 2002
Carbon and Nitrogen Mineralization Rates after Application of Organic Amendments to Soil ABSTRACT The objective of this study was to quantify C and N mineralization rates from a range of organic amendments that differed in their total C and N contents and C quality, to gain a better understanding of their influence on the soil N cycle. A pelletized poultry manure (PP), two green waste–based composts (GWCa, GWCb), a straw‐based compost (SBC), and a vermi‐cast (VER) were incubated in a coarse‐textured soil at 15°C for 142 d. The C quality of each amendment was determined by chemical analysis and by 13 C nuclear magnetic resonance (NMR). Carbon dioxide (CO2 –C) evolution was determined using alkali traps. Gross N mineralization rates were calculated by 15 N isotopic pool dilution. The CO2 –C evolution rates and gross N mineralization rates were generally higher in amended soils than in the control soil. With the exception of GWCb all amendments released inorganic N at concentrations that would be high enough to warrant a reduction in inorganic N fertilizer application rates. The amount of N released from PP was high indicating that application rates should be reduced, or alternative amendments used, to minimize leaching losses in regions where ground water quality is of concern. There was a highly significant relationship between CO2 –C evolution and gross N mineralization (R 2 = 0.95). Some of the chemically determined C quality parameters had significant relationships (p < 0.05) with both the cumulative amounts of C and N evolved. However, we found no significant relationships between 13 C NMR spectral groupings, or their ratios, and either the CO2 –C evolved or gross N mineralized from the amendments.
Journal of Environmental Quality - Tập 35 Số 1 - Trang 183-193 - 2006
Characterization of Slow Pyrolysis Biochars: Effects of Feedstocks and Pyrolysis Temperature on Biochar Properties
Journal of Environmental Quality - Tập 41 Số 4 - Trang 990-1000 - 2012
Arsenic Distribution in Florida Urban Soils ABSTRACT Arsenic contamination is of concern due to its effect as a carcinogen. Understanding the distribution of arsenic in urban soils is important for establishing baseline concentrations from which anthropogenic effects can be measured. The soil cleanup target level (SCTL) for arsenic in Florida (0.8 and 3.7 mg kg−1 in residential and commercial areas, respectively) is lower than in most states and is near the arsenic background concentrations in Florida soils. The objective of this study was to characterize the distribution of arsenic in the soils of two Florida cities, Gainesville and Miami. More than 200 soil samples were collected from three land‐use classes in each city (residential, commercial, and public land), digested with USEPA Method 3051a, and analyzed with graphite furnace atomic absorption spectrophotometry. Arsenic concentrations varied greatly in Gainesville, ranging from 0.21 to approximately 660 mg kg−1 with a geometric mean (GM) of 0.40 mg kg−1 (after discarding outliers), which was significantly lower than the GM of 2.81 mg kg−1 in Miami, although Miami samples ranged only from 0.32 to approximately 110 mg kg−1 Arsenic concentrations in 29 and 4% of the Gainesville soil samples and 95 and 33% of the Miami samples exceeded the Florida residential and commercial SCTL, respectively. This study is the first to provide information on arsenic distribution in urban soils of Florida, and the data are useful for assessing arsenic contamination and determining the need for remediation.
Journal of Environmental Quality - Tập 32 Số 1 - Trang 109-119 - 2003
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