bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of organic carbon content, clay type, and aging on the oral bioavailability of hexachlorobenzene in rats
Authors: Saghir Shakil A. , Bartels Michael J. , Budinsky Robert A. , Harris Jr., Eric E. , Clark Amy J. , Staley Jennifer L. , Chai Yunzhou , Davis John W. 
Published: October 2007

Abstract
Bioavailability of lipophilic chemicals is influenced by the physicochemical properties of soils/sediment such as particle size, pH, clay, and organic carbon content. The present study investigated the effects of sediment composition and aging on the oral bioavailability of hexachlorobenzene (HCB) in rats. Formulated sediments were prepared using various ratios of kaolinite and montmorillonite clay, sand, peat moss, and black carbon, spiked with 14C-HCB, and orally administered to rats prior to and after one year of aging in dark at 10°C. In the nonaged sediments there was a 21 to 45% reduction in the oral bioavailability of HCB when compared to the corn oil standard without any clear pattern of the impact of the sediment clay and/or organic carbon content. One year of aging resulted in statistically significant (p = 0.049) reduction in the oral bioavailability of HCB from the sediments compared to the corn oil standard and nonaged sediment indicating stronger interactions between HCB and sediment contents with aging. The mean reduction in oral bioavailability after one year of aging ranged from approximately 5 to 14% greater than that observed for nonaged sediments. The fecal elimination of the HCB-derived radioactivity from the one-year-aged sediments was much higher than the nonaged sediments, consistent with the lower absorption from the gastrointestinal tract due to lower desorption of HCB from the aged sediments. Increase in the fecal elimination and decrease in oral bioavailability of 14C-HCB was related to the increase in clay and black carbon.
Concentrations of methylated naphthalenes, anthracenes, and phenanthrenes occurring in Czech river sediments and their effects on toxic events associated with carcinogenesis in rat liver cell lines
Authors: Vondráĉek Jan , Ŝvihálková-Ŝindlerová Lenka , Pênĉíková Kater̂ina , Marvanová Son̂a , Krĉmár̂ Pavel , Ciganek Miroslav , Neĉa Jir̂í , Trosko James E. , Upham Brad , Kozubík Alois , Machala Miroslav 
Published: October 2007

AbstractAlkylated polycyclic aromatic hydrocarbons (PAHs) are important environmental pollutants. In the present study, we determined levels of monomethylated naphthalenes (MeNap), phenanthrenes (MePhe), and anthracenes (MeAnt) in Czech river sediments. The levels of MePhe generally were lower than the concentrations of phenanthrene. In contrast, both MeNap and MeAnt were found at levels higher than their respective parent compounds in the majority of sampling sites. We then investigated their aryl hydrocarbon receptor (AhR)-mediated activity, accumulation of phosphorylated p53 protein, induction of expression of cytochrome P450 1A1 (CYP1A1), inhibition of gap junctional intercellular communication (GJIC), and effects on cell proliferation in rat liver cell models to evaluate the relative importance of these toxicity mechanisms of low-molecular-weight methylated PAHs. Methylated phenanthrene and anthracene compounds were weak inducers of AhR-mediated activity as determined both in a reporter gene assay system and by detection of the endogenous gene (Cyp1a1) induction. 2-Methylphenanthrene was the most potent AhR ligand. Contribution of MeAnt and MePhe to overall AhR-inducing potencies should be taken into account in PAH-contaminated environments. Nevertheless, their effects on AhR were not sufficient to modulate cell proliferation in a normal rat liver progenitor cell model system. These PAHs only had a marginal effect on p53 phosphorylation at high doses of 1-, 3-, and 9-MePhe as well as 1 MeAnt. On the other hand, both 2- and 9-MeAnt as well as all the MePhe under study were efficient inhibitors of GJIC, suggesting that these compounds might act as tumor promoters. In summary, inhibition of GJIC and partial activation of AhR seem to be the most prominent toxic effects of the methylated PAHs in the present study.
Stereoisomeric separation and toxicity of the nematicide fosthiazate
Authors: Lin Kunde , Zhang Feng , Zhou Shanshan , Liu Weiping , Gan Jay , Pan Zhiyan 
Published: October 2007

Abstract
Considerable attention has been paid to the enantiomeric resolution and toxicity of some chiral organophosphorous pesticides (OPs) with one asymmetric center, but research concerning chiral OPs with two asymmetric centers is still limited. In the present study, the stereoisomeric separation and toxicity of fosthiazate, a chiral OP with two asymmetric centers on phosphorus and carbon atoms, was investigated. All four stereoisomers of fosthiazate were separated successfully with a Chiralpak® AD [amylase tris(3,5-dimethyl-phenyl carbamate)] column on high-performance liquid chromatography. The resolved isomers and the pairs of enantiomers were further distinguished using a circular dichroism detector and an optical rotation detector, designating the first (pk1) and third (pk3) eluted peaks as one pair of enantiomers and the second (pk2) and fourth (pk4) peaks as the other pair. The developed method was used to prepare microquantities of individual stereoisomers that were used for in vitro and in vivo bioassays. The inhibition potencies of the stereoisomers against acetylcholinesterase of Electrophorus electricus were slightly stereoselective, with a maximum difference of 1.4-fold among the isomers. A 3.1-fold difference, however, was observed in the acute toxicity of isomers to Daphnia magna. The 48-h toxicity of isomers to D. magna followed the order pk1 &gt; pk2 &gt; pk4 &gt; racemate ≈ pk3. The stereoselective toxicity to D. magna found in fosthiazate suggests that the environmental safety of fosthiazate should be evaluated on the basis of its individual isomers.
Methane Oxidation in an Intensively Cropped Tropical Rice Field Soil under Long‐Term Application of Organic and Mineral Fertilizers
Authors: Nayak D. R. , Babu Y. Jagadeesh , Datta A. , Adhya T. K. 
Published: October 2007

AbstractMethane (CH4) oxidation is the only known biological sink process for mitigating atmospheric and terrestrial emissions of CH4, a major greenhouse gas. Methane oxidation in an alluvial soil planted to rice (Oryza sativaL.) under long‐term application of organic (compost with a C/N ratio of 21.71), and mineral fertilizers was measured in a field‐cum‐laboratory incubation study. Oxidation rates were quantified in terms of decrease in the concentration of CH4in the headspace of incubation vessels and expressed as half‐life (t½) values. Methane oxidation rates significantly differed among the treatments and growth stages of the rice crop. Methane oxidation rates were high at the maximum tillering and maturity stages, whereas they were low at grain‐filling stage. Methane oxidation was low (t½= 15.76 d) when provided with low concentration of CH4On the contrary, high concentration of CH4resulted in faster oxidation (t½= 6.67 d), suggesting the predominance of “low affinity oxidation” in rice fields. Methane oxidation was stimulated following the application of mineral fertilizers or compost implicating nutrient limitation as one of the factors affecting the process. Combined application of compost and mineral fertilizer, however, inhibited CH4oxidation probably due to N immobilization by the added compost. The positive effect of mineral fertilizer on CH4oxidation rate was evident only at high CH4concentration (t½= 4.80 d), while at low CH4concentration their was considerable suppression (t½= 17.60 d). Further research may reveal that long‐term application of fertilizers, organic or inorganic, may not inhibit CH4oxidation.
Hydrological Variability and Agricultural Drainage Ditch Inorganic Nitrogen Reduction Capacity
Authors: Kröger R. , Holland M. M. , Moore M. T. , Cooper C. M. 
Published: October 2007

AbstractThe application of inorganic nitrogen fertilizers on agricultural landscapes has the potential to generate concerns of environmental degradation at fine to coarse scales across the catchment and landscape. Inorganic nitrogen species (NO3−, NO2−, and NH3) are typically associated with subsurface flow processes; however, surface runoff from rainfall events in no‐till agriculture with inorganic surface fertilizers might contribute to downstream eutrophication. Inorganic nitrogen reduction capacity of agricultural drainage ditches under no‐till cotton was determined under natural, variable rainfall conditions in northern Mississippi. Monthly grab baseflow samples and storm‐generated flow samples were variably sampled temporally within two experimental farm ditches over 2 yr. Inorganic nitrogen concentrations, in conjunction with Manning's equation and Natural Resources Conservation Service dimensionless hydrographs, provided individual water volumes per storm event and thus maximum effluent and outflow nitrogen loads. Base and stormflow regression results indicate drainage ditches reducing NO3− and NH3 over the length of the ditch for growing and dormant seasons. Overall, maximum storm loads of dissolved inorganic nitrogen (DIN) from the farm over the 2‐yr sampling period accounted for 2.2% of the initial fertilizer application, of which 1.1% left the ditch (0.84 kg ha−1 yr−1) (a 57% ditch reduction of DIN load over 2 yr). Long‐term sampling incorporating data on application and loss of fertilizers and farm management will provide critical information for farmers and scientists on the potential of economic gains and downstream ecosystem eutrophication, respectively.
Variations in Stream Water and Sediment Phosphorus among Select Ozark Catchments
Authors: Haggard Brian E. , Smith Douglas R. , Brye Kristofor R. 
Published: October 2007

AbstractStream sediments play a large role in the transport and fate of soluble reactive phosphorus (SRP) in stream ecosystems, and equilibrium P concentrations (EPC0) of benthic sediments at which P is neither adsorbed nor desorbed are often related to stream water SRP concentrations. This study evaluated (i) the variation among water chemistry and sediment‐P interactions among streams draining catchments that varied in the land use; (ii) the relations between SRP concentration, sediment EPC0, and other measured abiotic factors (e.g., particle size distribution, slope of linear sorption isotherms, etc.) in the stream sediments; and (iii) the use of the traditional Mehlich‐3 (M3) soil extraction on stream sediments to elucidate other abiotic factors (e.g, M3P, P saturation ratio, etc.) related to SRP concentration in stream sediments. Stream water and sediments were sampled at 22 selected Ozark streams in northwest Arkansas during fall 2003 and spring 2004. Nitrate‐N concentrations in the water column (r = 0.69) and modified P saturation ratios (PSRmod) of the benthic sediments (r = 0.79) at the selected streams increased with an increase in percent pasture in the catchments, whereas SRP concentration (r = –0.56) and Mehlich‐3–extractable P (M3P) content (r = –0.47) decreased with an increase in the percent forested area. Soluble reactive P concentrations in the stream water were positively correlated to sediment EPC0 (r = 0.51), although sediment EPC0 was generally greater than SRP. The M3 soil extraction was useful in identifying abiotic factors related to SRP concentrations in the selected streams, in particular SRP concentrations were positively correlated to M3P contents (r = 0.50) and PSRmod (r = 0.71) of the benthic sediments. Thus, M3P and EPC0 estimates from stream sediments may be valuable yet simple indicators of whether benthic sediments act as sinks or sources of P in fluvial systems, as well as estimating changes in stream SRP concentrations.
Phosphorus Speciation of Sequential Extracts of Organic Amendments Using Nuclear Magnetic Resonance and X‐ray Absorption Near‐Edge Structure Spectroscopies
Authors: Ajiboye Babasola , Akinremi Olalekan O. , Hu Yongfeng , Flaten Donald N. 
Published: October 2007

AbstractThe chemical forms of phosphorus in organic amendments are essential variables for proper management of these amendments for agro‐environmental purposes. This study was performed to elucidate the forms of phosphorus in various organic amendments using state‐of‐the‐art spectroscopic techniques. Anaerobically digested biosolids (BIO), hog (HOG), dairy (DAIRY), beef (BEEF), and poultry (POULTRY) manures were subjected to sequential extraction. The extracts and residues after extraction were analyzed by solution 31P nuclear magnetic resonance (NMR) and synchrotron‐based P 1s X‐ray absorption near‐edge structure (XANES) spectroscopies, respectively. Most of the total P analyzed by inductively coupled plasma– optical emission spectroscopy in the sequential extracts of organic amendments was orthophosphate, except POULTRY, which was dominated by organic P. The labile P fraction in all the organic amendments, excluding POULTRY, was mainly orthophosphate from readily soluble calcium and some aluminum phosphates. In the poultry litter, Ca phytate was the main P species controlling P solubility. The recalcitrant fraction of BIO was mainly associated with Al and Fe. Those of HOG, DAIRY, and POULTRY were calcium phytate, which were identified only as organic species in the XANES spectra. The combination of the three techniques—sequential chemical extraction, solution 31P NMR spectroscopy, and P 1s XANES—provided molecular characterization of P in organic amendments that would not have been possible with just one or a combination of any two of these techniques. Therefore, P speciation of organic amendments should use solid‐phase and aqueous speciation techniques as deemed feasible.
Assessment of the 16S‐23S rDNA Intergenic Spacer Region in Enterococcus spp. for Microbial Source Tracking
Authors: Dickerson J. W. , Crozier J. B. , Hagedorn C. , Hassall A. 
Published: October 2007

AbstractA new library‐based microbial source tracking (MST) approach intended for initial application in the coastal waters of Virginia was evaluated. Host‐origin isolates of Enterococcus spp. were collected from beaches and the surrounding tidewater region of Virginia and used to construct a library based on the pattern of DNA band lengths produced by the amplification of the 16S‐23S rDNA intergenic spacer (IGS) region, and subsequent digestion with MboI. Initial results from small host‐origin libraries (64 and 200 total isolates) with discriminant analysis (DA) and logistic regression (LR) yielded high average rates of correct classification (ARCC) for a four‐source classification split (birds, dogs, sewage, and wildlife), with ARCCs ranging from 83 to 100%. However, the poor results obtained when classification was attempted on a non‐library validation set (VS, ARCCs of 47 and 48%, respectively, using DA and LR) demonstrated that a library of 200 isolates was insufficient to adequately represent the diversity of the enterococci in the sampled region. An increase in the library size to 1029 total isolates was accompanied by a reduction in the ARCC of the library to 42.7% with DA and 45.7% with LR, plus similarly poor results obtained from the VS. The low correct classification rates generated by the larger known‐source library were unsuitable for field application. Many reported MST methods have been based on results obtained using small host‐origin libraries without external validation. Our results indicate that such an approach can be very misleading, and that larger libraries and external validation is essential for the confirmation of preliminary results.
Magnesium‐Rich Minerals in Sediment and Suspended Particulates of South Florida Water Bodies: Implications for Turbidity
Authors: Harris W. G. , Fisher M. M. , Cao X. , Osborne T. , Ellis L. 
Published: October 2007

AbstractFine sediments in shallow water bodies such as Lake Okeechobee are prone to resuspension. Predominantly inorganic “mud” sediment that covers ∼670 km2 of the lake has been recognized as a persistent source of turbidity. The objective of this study was to determine if mineral components of sediments in Lake Okeechobee and water conveyances of the northern Everglades also occur as suspended sediment and hence constitute a potential abiotic contributor to turbidity. Sediment samples were collected from nine stations within the lake and eight locations north of Water Conservation Area 2A in the Everglades. Water samples were also collected at selected locations. The silt and clay mineralogy of sediment and suspended particles was determined using X‐ray diffraction, thermogravimetry, scanning‐electron microscopy, energy‐dispersive X‐ray elemental microanalysis, and high‐resolution transmission‐electron microscopy. Clay fractions of the lake sediment contained the Mg silicate minerals sepiolite and palygorskite, along with smectite, dolomite, calcite, and kaolinite. Sediment silt fractions were dominated by carbonates and/or quartz, with smaller amounts of Ca phosphates and sepiolite. Mineralogy of the mud sediment was similar to that reported for geologic phosphate deposits. This suggests that the mud sediment might have accumulated by stream transport of minerals from these deposits. Suspended solids and mud‐sediment mineralogy were similar, except that smectite was more abundant in suspended solids. Everglade samples also contained Mg‐rich minerals. The small size, low density, and fibrous or platy nature of the prevalent mud sediment minerals make them an abiotic, hydrodynamically sensitive source of persistent turbidity in a shallow lake. Mitigation efforts focused exclusively on P‐induced biogeochemical processes do not address the origin or effects of these minerals. Ecological management issues such as turbidity control, P retention, geologic P input, and suitability of dredging are related to mud‐sediment properties and provenance.
Field Test of In Situ Soil Amendments at the Tar Creek National Priorities List Superfund Site
Authors: Brown S.L. , Compton H. , Basta N.T. 
Published: October 2007

AbstractA range of soil amendments including diammonium phosphate fertilizer (DAP), municipal biosolids (BS), biosolids compost, and Al‐ and Fe‐based water treatment residuals were tested on Pb‐, Zn‐, and Cd‐contaminated yard soils and tailings at the Tar Creek NPL site in Oklahoma to determine if amendments could restore a vegetative cover and reduce metal availability in situ. For the yard soils, all amendments reduced bioaccessible (assessed with a physiologic‐based extraction method) Pb, with reductions ranging from 35% (BS+Al, DAP 0.5%, DAP+Compost+Al) to 57% (Compost+Al). Plant Zn (Cynadon dactylon L.) and NH4NO3–extractable Cd and Zn were also reduced by a number of amendments. For the tailings, all amendments excluding BS reduced bioaccessible Pb, with the largest reductions observed in the DAP 3% and DAP3%+BS treatments (75 and 84%). Plant growth was suppressed in all treatments that contained DAP for the first season, with the highest growth in the treatments that included compost and biosolids. In the second year, growth was vigorous for all treatments. Plant Zn and Cd and extractable metal concentration were also reduced. A number of treatments were identified that reduced bioaccessible Pb and sustained a healthy plant with reduced metal concentrations. For the yard soil, Compost+Al was the most effective treatment tested. For the tailings, BS+DAP 1% was the most effective treatment tested. These results indicate that in situ amendments offer a remedial alternative for the Tar Creek site.
Ecotoxic Effect of Phenanthrene on Nitrifying Bacteria in Soils of Different Properties
Authors: Maliszewska‐Kordybach Barbara , Klimkowicz‐Pawlas Agnieszka , Smreczak Bozena , Janusauskaite Dalia 
Published: October 2007

AbstractInformation on ecotoxicity of organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs), in terrestrial environment is needed for establishing soil quality criteria and for risk assessment purposes. An ecotoxic effect of a model PAH compound (phenanthrene) toward soils microorganisms (nitrifying bacteria) was evaluated in 50 different soils. The soil samples were collected from agricultural land in four regions of Poland with varying levels of industrialization (Slaskie, Dolnoslaskie, Podlaskie, and Lubelskie voievodeships). Soils were characterized for basic physicochemical properties (texture, organic matter content, pHKCl, total nitrogen content, total sorption capacity) and the content of contaminants including PAHs (73–800 μg kg−1), Pb (6–720 mg kg−1), and Zn (9–667 mg kg−1). Ecotoxicity of phenanthrene (applied at 10, 100, 500, and 1000 mg kg−1) to soils microorganisms was evaluated in laboratory studies in control conditions (incubation of soils for 7 d at 20 ± 2°C). Nitrification potential was used as the ecotoxicity measurements end point. The EC50 values (146−1670 mg kg−1) calculated from the square root–X linear regression model differed significantly in various soils, although it was difficult to establish a causative relationship between soil physicochemical characteristic and phenanthrene toxicity. A significant factor in the assessment of soils vulnerability to the effect of phenanthrene was level of soil contamination, particularly with PAHs. Soils with previous contamination were more susceptible (mean EC50, 325 mg kg−1) than soils from uncontaminated, rural areas (mean EC50, 603 mg kg−1).
Controlled Application Rate of Water Treatment Residual for Agronomic and Environmental Benefits
Authors: Oladeji Olawale O. , O'Connor George A. , Sartain Jerry B. , Nair Vimala D. 
Published: October 2007

AbstractWater treatment residuals (WTR) are useful soil amendments to control excessive soluble phosphorus (P) in soils, but indiscriminate additions can result in inadequate control or excessive immobilization of soluble P, leading to crop deficiencies. We evaluated the influence of application rates of an Al‐WTR and various P‐sources on plant yields, tissue P concentrations, and P uptake and attempted to identify a basis for determining WTR application rates. Bahiagrass (paspalum notatum Fluggae) was grown in a P‐deficient soil amended with four P‐sources at two application levels (N‐ and P‐based rates) and three WTR rates (0, 10, and 25 g kg−1 oven dry basis) in a glasshouse pot experiment. The glasshouse results were compared with data from a 2‐yr field experiment with similar treatments that were surface applied to an established bahiagrass. Soil P storage capacity (SPSC) values increased with application rate of WTR, and the increase varied with sources of P applied. Soil soluble P concentrations increased as SPSC was reduced, and a change point was identified at 0 mg kg−1 SPSC in the glasshouse and the field studies. A change point was identified in the bahiagrass yields at a tissue P concentration of 2.0 g kg−1, corresponding to zero SPSC. Zero SPSC was shown to be an agronomic threshold above which yields and P concentrations of plants declined and below which there is little or no yield response to increased plant P concentrations. Applying P‐sources at N‐based rates, along with WTR sufficient to give SPSC value of 0 mg kg−1 SPSC, enhanced the environmental benefits (reduced P loss potential) without negative agronomic impacts.