bluuebunny/crossref_metadata_2025 huggingface dataset:
Partitioning of polychlorinated biphenyls between Arctic seawater and size-fractionated zooplankton
Authors: Sobek Anna , Reigstad Marit , Gustafsson Örjan
Published: July 2006

Concentrations of hydrophobic organic contaminants in zooplankton have been hypothesized to be governed by either near-equilibrium partitioning with surrounding water, growth dilution, or biomagnification. Concentrations of 17 polychlorinated biphenyls (PCBs) were measured in size-fractionated zooplankton, in phytoplankton (>0.7 μm), and in the dissolved water phase (<0.7 μm) in the surface water of the northern Barents Sea marginal ice zone east and north of Spitsbergen (Norway) and in the central Arctic Ocean at 89°N. The linear partition model was used to indirectly assess if PCBs were equilibrated between water and the extractable organic matter (EOM) of zooplankton. As an independent test, the relation between the EOM-normalized partition coefficient (log KEOM) and trophic level (TL) of the zooplankton (based on δ15N) was investigated. All log K–log KOW regressions were significant (n = 18, p < 0.05, r2 = 0.65–0.95), being consistent with near-equilibrium partitioning and indirectly suggesting the absence of biomagnification. No correlation was found between log KEOM and TL, further supporting the apparent absence of biomagnification in zooplankton. One implication of these results is a reduced uncertainty in modeling of food web uptake, in which kinetic parameterizations of biodilution or biomagnification in zooplankton may be replaced by a simpler parameterization based on equilibrium partitioning.
Mobilization of chrysene from soil in a model digestive system
Authors: Minhas Jaswinder K. , Vasiluk Luba , Pinto Linda J. , Gobas Frank A. P. C. , Moore Margo M.
Published: July 2006

Accurate estimates for the oral bioavailability of hydrophobic contaminants bound to solid matrices are challenging to obtain because of sorption to organic matter. The purpose of this research was to measure the bioavailability of [14C]chrysene sorbed to soil using an in vitro model of gastrointestinal digestion and absorption to a surrogate intestinal membrane, ethylene vinyl acetate (EVA) thin film. The [14C]chrysene moved rapidly from soil into the aqueous compartment and reached steady state within 2 h. Equilibrium was reached in the EVA film within 32 h. Aging the spiked soil for 6 or 12 months had no effect on chrysene mobilization. This was supported by the finding that the data best fit a one-compartment model. Despite significant decreases in [14C]chrysene mobilization when water or nonneutralized gastrointestinal fluids were used in place of the complete medium, the equilibrium concentration of [14C]chrysene in EVA film remained the same in all conditions. Thus, the driving force for uptake was the fugacity gradient between the aqueous phase and the EVA film. Cultured human enterocytes (human colorectal carcinoma cell line [Caco-2 cells]) had a higher lipid-normalized fugacity capacity than EVA film, but the elimination rate constants were the same, suggesting that the rate was controlled by the resistance of the unstirred aqueous layer at the membrane–water interface.
Removal and biodegradation of polycyclic aromatic hydrocarbons by Selenastrum capricornutum
Authors: Chan Sidney Man Ngai , Luan Tiangang , Wong Ming Hung , Tam Nora Fung Yee
Published: July 2006

The removal and degradation of a mixture of polycyclic aromatic hydrocarbons (PAH), namely phenanthrene (PHE), fluoranthene (FLA), and pyrene (PYR), by a green microalgal species, Selenastrum capricornutum, at different initial cell densities were studied. The PAH removal efficiency increased with the initial cell density, and 96% of PHE, 100% of FLA, and 100% of PYR in the medium were removed by live S. capricornutum at the density of 1 × 107 cells/ml in 4 d, whereas less than 50% of PAHs were removed at the lowest cell density (5 × 104 cells/ml) in 7 d. The removal mechanisms included initial adsorption onto the cell walls of both live and dead cells, and the adsorbed PAHs were then absorbed and degraded in live cells only. Among different PAHs in a mixture, irrespective of whether they were added to medium at the same or different concentrations, the removal preference by live S. capricornutum was in the descending order of PYR > FLA > PHE, whereas the biodegradation rates followed the descending order of FLA > PYR > PHE. Initial findings regarding PAH metabolites revealed that PHE was converted into four different monohydroxyphenanthrenes and two dihydroxyphenanthrenes, whereas FLA and PYR were converted into three hydroxylated derivatives through the monooxygenase pathway. The presence of dihydroxylated PAHs suggested that the dioxygenase pathway also might have taken place at the same time.
Risk assessment of the National Institute of Standards and Technology petroleum crude oil standard water accommodated fraction: Further application of a copepod-based, full life-cycle bioassay
Authors: Bejarano Adriana C. , Chandler G. Thomas , He Lijian , Cary Tawnya L. , Ferry John L
Published: July 2006

The U.S. National Institute of Standards and Technology (NIST) petroleum crude oil was used to generate NIST water-accommodated hydrocarbon fractions (WAFs) for standardized assessment of crude oil effects on the copepod Amphiascus tenuiremis. Effects were assessed using a 96-well microplate, full life-cycle test. Briefly, nauplii (age, 24 h) were reared individually to adults (n ≥ 120 nauplii/treatment) in microplate wells containing 200 μl of treatment solution (seawater control [0%] or 10, 30, 50, or 100% NIST-WAF). Nauplii were monitored through development to adulthood, and mature virgin male:female pairs mated in wells containing original treatments (<30 d). A second bioassay using 0, 10, 30, and 50% WAFs (n ≥ 60 nauplii/treatment) was conducted to assess the effects of ultraviolet (UV) light on naupliar endpoints (<16 d). In the first experiment, nauplius-to-copepodite survival in exposures to 100% WAF was 27% ± 6% lower than in controls (92% ± 1%), but copepodite-to-adult survival was greater than 90% across all treatments. Analysis of development curves showed that nauplii in the 10% WAF developed into copepodites 25% faster, whereas nauplii in the 50 and 100% WAFs developed 17% slower, than controls. Copepodite development into male and female copepods was significantly delayed (2 and 4 d, respectively) in the 100% WAF compared to controls. Although none of the WAF exposures had significant effects on fertilization success or total viable production (p > 0.05), embryo hatching in the 100% WAF was significantly less (70.0% ± 21.2%) than that in controls (87.0% ± 19.4%). Results from the UV bioassay showed that relatively short exposures (<14 d) to 30 and 50% WAFs in the presence of UV light caused negative effects on copepod survival and development. Naupliar-stage survival and developmental endpoints were the most sensitive indicators of exposure to the NIST crude oil WAF.
Trends in metals in urban and reference lake sediments across the United States, 1970 to 2001
Authors: Mahler Barbara J. , van Metre Peter C. , Callender Edward
Published: July 2006

Trends in metals concentrations in sediment cores from 35 reservoirs and lakes in urban and reference settings were analyzed to determine the effects of three decades of legislation, regulation, and changing demographics and industrial practices in the United States on concentrations of metals in the environment. Decreasing trends outnumber increasing trends for all seven metals analyzed (Cd, Cr, Cu, Pb, Hg, Ni, and Zn). The most consistent trends are for Pb and Cr: For Pb, 83% of the lakes have decreasing trends and 6% have increasing trends; for Cr, 54% of the lakes have decreasing trends and none have increasing trends. Mass accumulation rates of metals in cores, adjusted for background concentrations, decrease from the 1970s to the 1990s, with median changes ranging from −46% (Pb) to −3% (Hg and Zn). The largest decreases are from lakes in dense urban watersheds where the overall metals contamination in recently deposited sediments has decreased to one-half its 1970s median value. However, anthropogenic mass accumulation rates in dense urban lakes remain elevated over those in lakes in undeveloped watersheds, in some cases by as much as two orders of magnitude (Cr, Cu, and Zn), indicating that urban fluvial source signals can overwhelm those from regional atmospheric sources.
Elevated organochlorines in the brain–hypothalamic–pituitary complex of intersexual shovelnose sturgeon
Authors: Koch Brian T. , Garvey James E. , You Jing , Lydy Michael J.
Published: July 2006

Organochlorine compounds (OCs), including polychlorinated biphenyls and organochlorine pesticides, were used on lands adjacent to the Middle Mississippi River (MMR; USA) from 1930 through 1988, and they continue to occur in MMR fish. These compounds are estrogenic and/or antiandrogenic, and they alter hormone production and reception within the brain and gonads of male fish, resulting in intersexuality and/or suppressed gonadal development. To assess how OCs affect reproduction of MMR fish, we quantified OC accumulation, intersexuality, and gonadal development in male shovelnose sturgeon (Scaphirhynchus platorynchus) throughout the MMR during the spring of 2003. Gonads were observed for intersexual characteristics, weighed to calculate the gonadosomatic index (GSI), and examined histologically. Tissue accumulation of OCs was quantified in gonads, brain–hypothalamic–pituitary (BHP) complex, and fillets. Four of 48 mature males were identified macroscopically as intersexuals, and a fifth was found through histology (a 10.4% incidence). Intersexuals accumulated higher concentrations of OCs in the BHP complex compared with those of mature males. In addition, GSI and OC accumulation within the BHP complex, gonads, and fillets of mature males were negatively related. Exposure to OCs before or during sexual differentiation likely induces intersexuality in MMR shovelnose sturgeon, and exposure throughout gonadal maturation inhibits gonadal development.
Bioavailability and toxicity of soil particle-associated copper as determined by two bioluminescent Pseudomonas fluorescens biosensor strains
Authors: Brandt Kristian K. , Holm Peter E. , Nybroe Ole
Published: July 2006

We report the development and application of a novel, solid phase–contact bioassay based on two whole-cell bacterial biosensor strains. Our data indicate that a significant fraction of particle-associated Cu may be available to bacteria in dilute soil suspensions but also support the conventional view that mainly the soluble fraction of Cu is directly available to bacteria under more realistic soil conditions.
A biomarker approach to measure biological effects of contaminant exposure in largemouth bass from Lake Conestee, South Carolina, USA
Authors: Schreiber Erika A. , Otter Ryan R. , van den Hurk Peter
Published: July 2006

Sediments from Lake Conestee, a former reservoir now filled with pollutant-enriched sediments, located south of Greenville, South Carolina, USA, and other nearby reservoirs were collected and analyzed for lead and polycyclic aromatic hydrocarbons (PAHs). Hepatic ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), UDP-glucuronosyltransferase (UGT), sulfotransferase (SULT), and erythrocyte δ-aminolevulinic acid dehydratase (ALAD) were measured in largemouth bass (Micropterus salmoides) to characterize biological effects of these contaminants over three seasons. Results showed that total PAH concentrations in Lake Conestee sediments were significantly greater than the control during each season. An average 10-fold induction in EROD activity was observed at Lake Conestee compared with the control over all three seasons, indicating that PAHs present in sediment were bioavailable to fish. Significant gender effects were observed in EROD activity during the spring, in which activity in reproductively active female fish was significantly suppressed compared with the male fish. Sediments from Lake Conestee had elevated lead concentrations, but the lack of ALAD inhibition in bass indicated that lead was not biologically available. Total GST activity, UGT activity, and SULT activity were not significantly induced in fish from any of the affected sites compared with the reference site. Both EROD and UGT activities were highest during the winter, as were sediment PAH concentrations in Lake Conestee, possibly linked to seasonal resuspension events. The biomarkers measured in this study were useful as a first investigation into the biological effects of contaminant exposure, as well as in determining the bioavailability of contaminants in Lake Conestee.
The focus group interview
Authors: Ho Debbie G.E.
Published: July 2006

This paper explores the possibility of expanding the focus group interview into the field of English as a Second Language (ESL), where this research methodology is yet to be thoroughly explored. Specifically, it aims to challenge popular criticisms about the reliability and validity of the focus group as a qualitative research methodology. It does this by first setting up a list of five main criticisms of the focus group interview drawn from current literature on research methodology within the social sciences and education. Based on transcripts of interactional data gathered from focus group interviews carried out among ESL students in a formal ESL context, it then provides a direct and detailed response to each criticism. The arguments put forward demonstrate that the focus group interview, as a method of data collection, may be particularly relevant in gathering the viewpoints and opinions of participants who have traditionally not been well represented through the more conventional and common methods currently employed in ESL research studies. Furthermore, the paper raises conscious awareness about the potential of the focus group as a viable and verifiable tool in qualitative research methodology.
Exploring an approach for teaching subject specific genres in Chinese
Authors: Shum Mark Shiu Kee
Published: July 2006

This research seeks both to describe Chinese genres found in a range of school subjects and to develop models of pedagogical principles for their teaching. Thus far, most of the research has been devoted to the teaching of genres for first and second language teaching, though there is a developing interest in research into the teaching of genres in teaching English as a foreign language. There is a need to develop genre-based research in languages other than English, in order to test the application of the theory to non-English speaking contexts. This paper reports on an approach to the study of Chinese genres for examination purposes, developed in Hong Kong, where, since 1997, official support has been given to the use of Chinese as a medium of instruction. The study is not yet completed, though there is some encouraging evidence that the genre-based approach is proving useful.
Carbon Sequestration in Dryland Soils and Plant Residue as Influenced by Tillage and Crop Rotation
Authors: Sainju Upendra M. , Lenssen Andrew , Caesar‐Thonthat Thecan , Waddell Jed
Published: July 2006

Long‐term use of conventional tillage and wheat (Triticum aestivum L.)–fallow systems in the northern Great Plains have resulted in low soil organic carbon (SOC) levels. We examined the effects of two tillage practices [conventional till (CT) and no‐till (NT)], five crop rotations [continuous spring wheat (CW), spring wheat–fallow (W–F), spring wheat–lentil (Lens culinaris Medic.) (W–L), spring wheat–spring wheat–fallow (W–W–F), and spring wheat–pea (Pisum sativum L.)–fallow (W–P–F)], and Conservation Reserve Program (CRP) planting on plant C input, SOC, and particulate organic carbon (POC). A field experiment was conducted in a mixture of Scobey clay loam (fine‐loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) from 1998 to 2003 in Havre, MT. Total plant biomass returned to the soil from 1998 to 2003 was greater in CW (15.5 Mg ha−1) than in other rotations. Residue cover, amount, and C content in 2004 were 33 to 86% greater in NT than in CT and greater in CRP than in crop rotations. Residue amount (2.47 Mg ha−1) and C content (0.96 Mg ha−1) were greater in NT with CW than in other treatments, except in CT with CRP and W–F and in NT with CRP and W–W–F. The SOC at the 0‐ to 5‐cm depth was 23% greater in NT (6.4 Mg ha−1) than in CT. The POC was not influenced by tillage and crop rotation, but POC to SOC ratio at the 0‐ to 20‐cm depth was greater in NT with W–L (369 g kg−1 SOC) than in CT with CW, W–F, and W–L. From 1998 to 2003, SOC at the 0‐ to 20‐cm depth decreased by 4% in CT but increased by 3% in NT. Carbon can be sequestered in dryland soils and plant residue in areas previously under CRP using reduced tillage and increased cropping intensity, such as NT with CW, compared with traditional practice, such as CT with W–F system, and the content can be similar to that in CRP planting.
Forest Environmental Investments and Implications for Climate Change Mitigation
Authors: Alig Ralph J. , Bair Lucas S.
Published: July 2006

Forest environmental conditions are affected by climate change, but investments in forest environmental quality can be used as part of the climate change mitigation strategy. A key question involving the potential use of forests to store more carbon as part of climate change mitigation is the impact of forest investments on the timing and quantity of forest volumes that affect carbon storage. Using an economic optimization model, we project levels of U.S. forest volumes as indicators of carbon storage for a wide range of private forest investment scenarios. Results show that economic opportunities exist to further intensify timber management on some hectares and reduce the average timber rotation length such that the national volume of standing timber stocks could be reduced relative to projections reflecting historical trends. The national amount of timber volume is projected to increase over the next 50 yr, but then is projected to decline if private owners follow an economic optimization path, such as with more forest type conversions and shorter timber rotations. With perfect foresight, future forest investments can affect current timber harvest levels, with intertemporal linkages based on adjustments through markets. Forest investments that boost regenerated timber yields per hectare would act to enhance ecosystem services (e.g., forest carbon storage) if they are related to the rate of growth and extent of growing stock inventory.
Carbon Sequestration Potential in Reclaimed Mine Sites in Seven East‐Central States
Authors: Sperow Mark
Published: July 2006

Terrestrial systems represent a significant potential carbon (C) sink to help mitigate or offset greenhouse gas emissions. Nearly 3.2 Mha are permitted for mining activities in the United States, which are required to be reclaimed with vegetative cover. While site‐specific studies have assessed C accumulation on reclaimed mine sites, regional analyses to estimate potential C increases have not been conducted. For this analysis, potential C sequestration is analyzed on 567 000 ha of mine land in a seven‐state region reclaimed to cropland, pasture, or forest. Carbon accumulation is estimated for cropland, pasture, and forest soils, forest litter layer, and aboveground biomass by estimating average annual rates of C accumulation from site‐specific and general C sequestration studies. The average annual rate of C storage is highest when mine land is reclaimed to forest, where the potential sequestration is 0.7 to 2.2 Tg yr−1 The C from soils, litter layer, and biomass from mine lands reclaimed to forest represents 0.3 to 1.0% of the 1990 CO2 emissions from the study region (919 Tg CO2). To achieve the greenhouse gas (GHG) emission reduction goal of 7% below the 1990 level as proposed by the Kyoto Treaty requires CO2 emissions in the study area to be reduced by just over 64 Tg CO2 The potential carbon storage in mine sites reclaimed to forest could account for 4 to 12.5% of these required reductions.
Forest Carbon Management in the United States
Authors: Birdsey Richard , Pregitzer Kurt , Lucier Alan
Published: July 2006

This paper reviews the effects of past forest management on carbon stocks in the United States, and the challenges for managing forest carbon resources in the 21st century. Forests in the United States were in approximate carbon balance with the atmosphere from 1600–1800. Utilization and land clearing caused a large pulse of forest carbon emissions during the 19th century, followed by regrowth and net forest carbon sequestration in the 20th century. Recent data and knowledge of the general behavior of forests after disturbance suggest that the rate of forest carbon sequestration is declining. A goal of an additional 100 to 200 Tg C/yr of forest carbon sequestration is achievable, but would require investment in inventory and monitoring, development of technology and practices, and assistance for land managers.
Effects of Elevated Atmospheric Carbon Dioxide on Biomass and Carbon Accumulation in a Model Regenerating Longleaf Pine Community
Authors: Runion G. B. , Davis M. A. , Pritchard S. G. , Prior S. A. , Mitchell R. J. , Torbert H. A. , Rogers H. H. , Dute R. R.
Published: July 2006

Plant species vary in response to atmospheric CO2 concentration due to differences in physiology, morphology, phenology, and symbiotic relationships. These differences make it very difficult to predict how plant communities will respond to elevated CO2 Such information is critical to furthering our understanding of community and ecosystem responses to global climate change. To determine how a simple plant community might respond to elevated CO2, a model regenerating longleaf pine community composed of five species was exposed to two CO2 regimes (ambient, 365 μmol mol−1 and elevated, 720 μmol mol−1) for 3 yr. Total above‐ and belowground biomass was 70 and 49% greater, respectively, in CO2–enriched plots. Carbon (C) content followed a response pattern similar to biomass, resulting in a significant increase of 13.8 Mg C ha−1 under elevated CO2 Responses of individual species, however, varied. Longleaf pine (Pinus palustris Mill.) was primarily responsible for the positive response to CO2 enrichment. Wiregrass (Aristida stricta Michx.), rattlebox (Crotalaria rotundifolia Walt. Ex Gmel.), and butterfly weed (Asclepias tuberosa L.) exhibited negative above‐ and belowground biomass responses to elevated CO2, while sand post oak (Quercus margaretta Ashe) did not differ significantly between CO2 treatments. As with pine, C content followed patterns similar to biomass. Elevated CO2 resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO2–enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO2 plots, but only 8% under high CO2 Therefore, while longleaf pine may perform well in a high CO2 world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO2 on plant communities are complex, dynamic, and difficult to predict, clearly demonstrating the need for more research in this important area of global change science.
Long‐Term Trends in Nitrous Oxide Emissions, Soil Nitrogen, and Crop Yields of Till and No‐Till Cropping Systems
Authors: Grandy A. Stuart , Loecke Terrance D. , Parr Sara , Robertson G. Philip
Published: July 2006

No‐till cropping can increase soil C stocks and aggregation but patterns of long‐term changes in N2O emissions, soil N availability, and crop yields still need to be resolved. We measured soil C accumulation, aggregation, soil water, N2O emissions, soil inorganic N, and crop yields in till and no‐till corn–soybean–wheat rotations between 1989 and 2002 in southwestern Michigan and investigated whether tillage effects varied over time or by crop. Mean annual NO3−concentrations in no‐till were significantly less than in conventional till in three of six corn years and during one year of wheat production. Yields were similar in each system for all 14 years but three, during which yields were higher in no‐till, indicating that lower soil NO3−concentrations did not result in lower yields. Carbon accumulated in no‐till soils at a rate of 26 g C m−2yr−1over 12 years at the 0‐ to 5‐cm soil depth. Average nitrous oxide emissions were similar in till (3.27 ± 0.52 g N ha d−1) and no‐till (3.63 ± 0.53 g N ha d−1) systems and were sufficient to offset 56 to 61% of the reduction in CO2equivalents associated with no‐till C sequestration. After controlling for rotation and environmental effects by normalizing treatment differences between till and no‐till systems we found no significant trends in soil N, N2O emissions, or yields through time. In our sandy loam soils, no‐till cropping enhances C storage, aggregation, and associated environmental processes with no significant ecological or yield tradeoffs.
Nitrous Oxide Emissions from Corn–Soybean Systems in the Midwest
Authors: Parkin Timothy B. , Kaspar Thomas C.
Published: July 2006

Soil N2O emissions from three corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] systems in central Iowa were measured from the spring of 2003 through February 2005. The three managements systems evaluated were full‐width tillage (fall chisel plow, spring disk), no‐till, and no‐till with a rye (Secale cereale L. ‘Rymin’) winter cover crop. Four replicate plots of each treatment were established within each crop of the rotation and both crops were present in each of the two growing seasons. Nitrous oxide fluxes were measured weekly during the periods of April through October, biweekly during March and November, and monthly in December, January, and February. Two polyvinyl chloride rings (30‐cm diameter) were installed in each plot (in and between plant rows) and were used to support soil chambers during the gas flux measurements. Flux measurements were performed by placing vented chambers on the rings and collecting gas samples 0, 15, 30, and 45 min following chamber deployment. Nitrous oxide fluxes were computed from the change in N2O concentration with time, after accounting for diffusional constraints. We observed no significant tillage or cover crop effects on N2O flux in either year. In 2003 mean N2O fluxes were 2.7, 2.2, and 2.3 kg N2O‐N ha−1 yr−1 from the soybean plots under chisel plow, no‐till, and no‐till + cover crop, respectively. Emissions from the chisel plow, no‐till, and no‐till + cover crop plots planted to corn averaged 10.2, 7.9, and 7.6 kg N2O‐N ha−1 yr−1, respectively. In 2004 fluxes from both crops were higher than in 2003, but fluxes did not differ among the management systems. Fluxes from the corn plots were significantly higher than from the soybean plots in both years. Comparison of our results with estimates calculated using the Intergovernmental Panel on Climate Change default emission factor of 0.0125 indicate that the estimated fluxes underestimate measured emissions by a factor of 3 at our sites.
Carbon Supply and Storage in Tilled and Nontilled Soils as Influenced by Cover Crops and Nitrogen Fertilization
Authors: Sainju Upendra M. , Singh Bharat P. , Whitehead Wayne F. , Wang Shirley
Published: July 2006

Soil carbon (C) sequestration in tilled and nontilled areas can be influenced by crop management practices due to differences in plant C inputs and their rate of mineralization. We examined the influence of four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secale cereale L.)], biculture of legume and nonlegume (vetch and rye), and no cover crops (or winter weeds)} and three nitrogen (N) fertilization rates (0, 60 to 65, and 120 to 130 kg N ha−1) on C inputs from cover crops, cotton (Gossypium hirsutum L.), and sorghum [Sorghum bicolor (L.) Moench)], and soil organic carbon (SOC) at the 0‐ to 120‐cm depth in tilled and nontilled areas. A field experiment was conducted on Dothan sandy loam (fine‐loamy, siliceous, thermic Plinthic Paleudults) from 1999 to 2002 in central Georgia. Total C inputs to the soil from cover crops, cotton, and sorghum from 2000 to 2002 ranged from 6.8 to 22.8 Mg ha−1 The SOC at 0 to 10 cm fluctuated with C input from October 1999 to November 2002 and was greater from cover crops than from weeds in no‐tilled plots. In contrast, SOC values at 10 to 30 cm in no‐tilled and at 0 to 60 cm in chisel‐tilled plots were greater for biculture than for weeds. As a result, C at 0 to 30 cm was sequestered at rates of 267, 33, −133, and −967 kg C ha−1 yr−1 for biculture, rye, vetch, and weeds, respectively, in the no‐tilled plot. In strip‐tilled and chisel‐tilled plots, SOC at 0 to 30 cm decreased at rates of 233 to 1233 kg C ha−1 yr−1 The SOC at 0 to 30 cm increased more in cover crops with 120 to 130 kg N ha−1 yr−1 than in weeds with 0 kg N ha−1 yr−1, regardless of tillage. In the subtropical humid region of the southeastern United States, cover crops and N fertilization can increase the amount of C input and storage in tilled and nontilled soils, and hairy vetch and rye biculture was more effective in sequestering C than monocultures or no cover crop.
Effect of Land‐Cover Change on Terrestrial Carbon Dynamics in the Southern United States
Authors: Chen Hua , Tian Hanqin , Liu Mingliang , Melillo Jerry , Pan Shufen , Zhang Chi
Published: July 2006

Land‐cover change has significant influence on carbon storage and fluxes in terrestrial ecosystems. The southern United States is thought to be the largest carbon sink across the conterminous United States. However, the spatial and temporary variability of carbon storage and fluxes due to land‐cover change in the southern United States remains unclear. In this study, we first reconstructed the annual data set of land‐cover of the southern United States from 1860 to 2003 with a spatial resolution of 8 km. Then we used a spatially explicit process‐based biogeochemical model (Terrestrial Ecosystem Model [TEM] 4.3) to simulate the effects of cropland expansion and forest regrowth on the carbon dynamics in this region. The pattern of land‐cover change in the southern United States was primarily driven by the change of cropland, including cropland expansion and forest regrowth on abandoned cropland. The TEM simulation estimated that total carbon storage in the southern United States in 1860 was 36.8 Pg C, which likely was overestimated, including 10.8 Pg C in the southeast and 26 Pg C in the south‐central. During 1860–2003, a total of 9.4 Pg C, including 6.5 Pg C of vegetation and 2.9 Pg C of soil C pool, was released to the atmosphere in the southern United States. The net carbon flux due to cropland expansion and forest regrowth on abandoned cropland was approximately zero in the entire southern region between 1980 and 2003. The temporal and spatial variability of regional net carbon exchange was influenced by land‐cover pattern, especially the distribution of cropland. The land‐use analysis in this study is incomplete and preliminary. Finally, the limitations, improvements, and future research needs of this study were discussed.
Use of Physical Properties to Predict the Effects of Tillage Practices on Organic Matter Dynamics in Three Illinois Soils
Authors: Yoo Gayoung , Nissen Todd M. , Wander Michelle M.
Published: July 2006

This work builds on a previous study of long‐term tillage trials that found use of no‐tillage (NT) practices increased soil organic carbon (SOC) sequestration at Monmouth, IL (silt loam soil) by increasing the soil's protective capacity, but did not alter SOC storage in DeKalb, IL (silty clay loam), where higher clay contents provided a protective capacity not affected by tillage. The least limiting water range (LLWR), a multi‐factor index of structural quality, predicted observed soil CO2 efflux patterns. Here we consider whether LLWR can predict sequestration trends at a third site, Perry, IL (silt loam soil) where SOC content is lower and bulk density is higher than in previously considered sites, and determine whether pore size characteristics can help explain the influence use of NT practices has had on SOC sequestration at all three locations. At Perry, LLWR was again related with differences in specific soil organic carbon mineralization rates (RESPsp) (2000–2001). Reduced RESPsp rates explain increases in SOC storage under NT management observed only after 17 yr. Trends in RESPsp suggest use of NT practices only enhance physical protection of SOC where soil bulk density is relatively high (approximately 1.4 g cm−3). In those soils (Monmouth and Perry), use of NT management reduced the volume of small macropores (15–150 μm) thought to be important for microbial activity. Physical properties appear to determine whether or not use of NT practices will enhance C storage by increasing physical protection of SOC. By refining the functions used to compute the LLWR and our understanding of the interactions between management, pore structure, and SOC mineralization, we should be able to predict the influence of tillage practices on SOC sequestration.
Nutrient Transport from Livestock Manure Applied to Pastureland Using Phosphorus‐Based Management Strategies
Authors: Soupir M. L. , Mostaghimi S. , Yagow E. R.
Published: July 2006

Land applications of manure from confined animal systems and direct deposit by grazing animals are both major sources of nutrients in streams. The objectives of this study were to determine the effects of P‐based manure applications on total suspended solids (TSS) and nutrient losses from dairy manures and poultry litter surface applied to pasturelands and to compare the nutrient losses transported to the edge of the field during overland flow events. Two sets of plots were established: one set for the study of in‐field release and another set for the study of edge‐of‐the‐field nutrient transport. Release plots were constructed at three pastureland sites (previous poultry litter applications, previous liquid dairy manure application, and no prior manure application) and received four manure treatments (turkey [Meleagris gallopavo] litter, liquid dairy manure, standard cowpies, and none). Pasture plots with a history of previous manure applications released higher concentrations of TSS and higher percentages of total P (TP) in the particulate form. Transport plots were developed on pasture with no prior manure application. The average flow‐weighted TP concentrations were highest in runoff samples from the plots treated with cowpies (1.57 mg L−1). Reducing excess P in dairy cow diets and surface applying manure to the land using P‐based management practices did not increase N concentrations in runoff. This study found that nutrients are most transportable from cowpies; thus a buffer zone between pastureland and streams or other appropriate management practices are necessary to reduce nutrient losses to waterbodies.
Mapping Ground Water Vulnerability to Pesticide Leaching with a Process‐Based Metamodel of EuroPEARL
Authors: Tiktak A. , Boesten J. J. T. I. , van der Linden A. M. A. , Vanclooster M.
Published: July 2006

To support EU policy, indicators of pesticide leaching at the European level are required. For this reason, a metamodel of the spatially distributed European pesticide leaching model EuroPEARL was developed. EuroPEARL considers transient flow and solute transport and assumes Freundlich adsorption, first‐order degradation and passive plant uptake of pesticides. Physical parameters are depth dependent while (bio)‐chemical parameters are depth, temperature, and moisture dependent. The metamodel is based on an analytical expression that describes the mass fraction of pesticide leached. The metamodel ignores vertical parameter variations and assumes steady flow. The calibration dataset was generated with EuroPEARL and consisted of approximately 60 000 simulations done for 56 pesticides with different half‐lives and partitioning coefficients. The target variable was the 80th percentile of the annual average leaching concentration at 1‐m depth from a time series of 20 yr. The metamodel explains over 90% of the variation of the original model with only four independent spatial attributes. These parameters are available in European soil and climate databases, so that the calibrated metamodel could be applied to generate maps of the predicted leaching concentration in the European Union. Maps generated with the metamodel showed a good similarity with the maps obtained with EuroPEARL, which was confirmed by means of quantitative performance indicators.
Phosphorus and Nitrogen in Rainfall Simulation Runoff after Fresh and Composted Beef Cattle Manure Application
Authors: Miller Jim J. , Olson Edith C. S. , Chanasyk David S. , Beasley Bruce W. , Larney Francis J. , Olson Barry M.
Published: July 2006

Fresh beef cattle (Bos taurus) manure has traditionally been applied to cropland in southern Alberta, but there has been an increase in application of composted manure to cropland in this region. However, the quality of runoff under fresh manure (FM) versus composted manure (CM) has not been investigated. Our objective was to compare runoff quality under increasing rates (0, 13, 42, 83 Mg ha−1 dry wt.) of FM and CM applied for two consecutive years to a clay loam soil cropped to irrigated barley (Hordeum vulgare L.). We determined total phosphorus (TP), particulate phosphorus (PP), dissolved reactive phosphorus (DRP), total nitrogen (TN), NH4–N, and NO3–N concentrations and loads in runoff after one (1999) and two (2000) applications of FM and CM. We found significantly (P ≤ 0.05) higher TP, DRP, and NH4–N concentrations, and higher DRP and TN loads under FM than CM after 2 yr of manure application. The TP loads were also higher under FM than CM at the 83 Mg ha−1 rate in 2000, and DRP loads were higher for FM than CM at this high rate when averaged over both years. Application rate had a significant effect on TP and DRP concentrations in runoff. In addition, the slope values of the regressions between TP and DRP in runoff versus application rate were considerably higher for FM in 2000 than for FM in 1999, and CM in both 1999 and 2000. Significant positive relationships were found for TP and DRP in runoff versus soil Kelowna‐extractable P and soil water‐extractable P for FM and CM in 2000, indicating that interaction of runoff with the soil controlled the release of P. Total P and DRP were the variables most affected by the treatments. Overall, our study found that application of CM rather than FM to cropland may lower certain forms of P and N in surface runoff, but this is dependent on the interaction with year, application rate, or both.
Soil Microbial Communities and Enzyme Activities under Various Poultry Litter Application Rates
Authors: Acosta‐Martínez V. , Harmel R. Daren
Published: July 2006

The potential excessive nutrient and/or microbial loading from mismanaged land application of organic fertilizers is forcing changes in animal waste management. Currently, it is not clear to what extent different rates of poultry litter impact soil microbial communities, which control nutrient availability, organic matter quality and quantity, and soil degradation potential. From 2002 to 2004, we investigated the microbial community and several enzyme activities in a Vertisol soil (fine, smectitic, thermic, Udic Haplustert) at 0 to 15 cm as affected by different rates of poultry litter application to pasture (0, 6.7, and 13.4 Mg ha−1) and cultivated sites (0, 4.5, 6.7, 9.0, 11.2, and 13.4 Mg ha−1) in Texas, USA. No differences in soil pH (average: 7.9), total N (pasture: 2.01–3.53, cultivated: 1.09–1.98 g kg−1 soil) or organic C (pasture average: 25–26.7, cultivated average: 13.9–16.1 g kg−1 soil) were observed following the first four years of litter application. Microbial biomass carbon (MBC) and nitrogen (MBN) increased at litter rates greater than 6.7 Mg ha−1 (pasture: MBC = >863, MBN = >88 mg kg−1 soil) compared to sites with no applied litter (MBC = 722, MBN = 69 mg kg−1 soil). Enzyme activities of C (β‐glucosidase, α‐galactosidase, β‐glucosaminidase) or N cycling (β‐glucosaminidase) were increased at litter rates greater than 6.7 Mg ha−1 Enzyme activities of P (alkaline phosphatase) and S (arylsulfatase) mineralization showed the same response in pasture, but they were only increased at the highest (9.0, 11.2, and 13.4 Mg ha−1) litter application rates in cultivated sites. According to fatty acid methyl ester (FAME) analysis, the pasture soils experienced shifts to higher bacterial populations at litter rates of 6.7 Mg ha−1, and shifts to higher fungal populations at the highest litter application rates in cultivated sites. While rates greater than 6.7 Mg ha−1 provided rapid enhancement of the soil microbial populations and enzymatic activities, they result in P application in excess of crop needs. Thus, studies will continue to investigate whether litter application at rates below 6.7 Mg ha−1, previously recommended to maintain water quality, will result in similar improved soil microbial and biochemical functioning with continued annual litter application.
Waterborne outbreaks reported in the United States
Authors: Craun Michael F. , Craun Gunther F. , Calderon Rebecca L. , Beach Michael J.
Published: July 2006

Epidemic waterborne risks are discussed in this paper. Although the true incidence of waterborne illness is not reflected in the currently reported outbreak statistics, outbreak surveillance has provided information about the important waterborne pathogens, relative degrees of risk associated with water sources and treatment processes, and adequacy of regulations. Pathogens and water system deficiencies that are identified in outbreaks may also be important causes of endemic waterborne illness. In recent years, investigators have identified a large number of pathogens responsible for outbreaks, and research has focused on their sources, resistance to water disinfection, and removal from drinking water. Outbreaks in surface water systems have decreased in the recent decade, most likely due to recent regulations and improved treatment efficacy. Of increased importance, however, are outbreaks caused by the microbial contamination of water distribution systems. In order to better estimate waterborne risks in the United States, additional information is needed about the contribution of distribution system contaminants to endemic waterborne risks and undetected waterborne outbreaks, especially those associated with distribution system contaminants.
The rate of acute gastrointestinal illness in developed countries
Authors: Roy Sharon L. , Scallan Elaine , Beach Michael J.
Published: July 2006

This paper reviews estimates of the incidence and prevalence of acute gastrointestinal illness (AGI) from 33 studies. These studies include prospective cohort studies, retrospective cross-sectional population-based surveys, and intervention trials from the United States and six other developed countries published since 1953. The incidence and prevalence estimates for AGI reported in these studies range from 0.1 to 3.5 episodes per person-year. However, comparisons of these rates are problematic owing to significant variation in study design, sampling methodology, and case definitions and should be made with caution. In the United States, the Centers for Disease Control and Prevention's (CDC) Foodborne Diseases Active Surveillance Network (FoodNet) estimates a rate of 0.65 episodes of AGI per person-year. This estimate includes diarrhea and/or vomiting of infectious or non-infectious origin, with a measure of severity (impairment of daily activities or diarrhea duration greater than 1 day), and has been adjusted for combined respiratory–gastrointestinal illnesses. However, it excludes episodes of diarrhea or vomiting due to any long-lasting or chronic illness or condition. Limitations in study design result in an unknown degree of uncertainty around this point estimate.
Towards a US national estimate of the risk of endemic waterborne disease – sero-epidemiologic studies
Authors: Casemore David
Published: July 2006

Worldwide literature on serological methods and sero-surveys on waterborne pathogens has been reviewed. Outbreak investigation and research reports have also been examined to aid understanding of the serological response and transmission dynamics. The aim was to seek an estimate of seroprevalence and to determine if this could inform the US national estimate of risk for endemic waterborne infection associated with public water supplies. Antibody responses indicate infection, both symptomatic and asymptomatic, so probably give a truer indication of prevalence. Outbreak data can probably be regarded as the upper bound for seroprevalence estimations. Antibody is not necessarily protective per se but is a good indicator for at least partial resistance to symptomatic infection; absence of antibody will normally imply susceptibility. Pathogens transmitted by water are commonly transmitted by other routes. However, the fact that other transmission routes are more common does not detract from the potential protective effect of immunity when waterborne transmission occurs. Data indicate that seroprevalence varies widely, reflecting geographic, social and hygiene factors, but is generally greater where surface water sources are used rather than groundwater. Areas of low seroprevalence may expect a high attack rate in the event of contamination of their water supply.
Water resources administration institution in China
Authors: Yan Feng , Daming He , Kinne Beth
Published: July 2006

Water is one of the basic natural resources and a strategic economic one. According to Chinese law (The Constitution and The 2002 Water Law), water resources are national properties and the state government has the responsibility to administer and protect them. At present, water administration is shared by several ministries of the State Council and called “nine dragons administer water”. This paper illustrates the overall water administration scheme. It focuses on the overlapping mandates and interactions between various ministries, particularly those between the Ministry of Water Resources (MWR) and the State Environment Protection Administration (SEPA). The paper then analyzes the reasons why conflicts and disputes over ministry policies and strategies occur and the resultant lowering of administration efficiency and degradation of the water environment. Considering the complexity of water administration and the multiple demands on and limited water resources, some trends must be developed in water administration institutions to improve the efficiency of water administration. In particular, water administration must be strengthened and unified; administrative power must be separated from supervisory power; watershed management and planning must be strengthened; and cooperation among the related water departments must be increased.
Removal of inhibitory phenolic compounds by biological activated carbon coupled membrane bioreactor
Authors: Thuy Q.T.T. , Visvanathan C.
Published: July 2006

Phenolic compounds cause problems for conventional treatments due to their toxic and inhibitory properties. This work investigated the treatability of phenolic compounds by using two membrane-bioreactor systems, namely: activated sludge coupled with MBR (AS-MBR) and biological granular activated carbon coupled with MBR (BAC-MBR). Initially, the system was fed with phenol (500 mg/L) followed by adding 2,4-dichlorophenol (2,4-DCP). Phenol, 2,4-DCP, TOC and COD removal were higher than 98.99% when the organic load ranged between 1.80 and 5.76 kg/m3.d COD. In addition to MBR system development, removal mechanisms were also investigated. Relatively low values of phenol adsorption of GAC and biomass, and high maximum substrate removal rates obtained from a biokinetic experiment, proved that the removals were mainly due to biodegradation. Analysis of sludge indicated a significant difference in the sludge characteristics of the two reactors. The high EPS content in BAC-MBR led to higher viscosity and poor sludge settling properties. The relationship between sludge properties and EPS components revealed that settleability had no direct correlation with EPS, though it was better correlated to protein/carbohydrate ratios.