bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant Biomass and Elemental Changes in Shrubland Forages following Biosolids Application
Authors: Pierce B.L. , Redente E.F. , Barbarick K. A. , Brobst R.B. , Hegeman P.
Published: July 2010

Land application of biosolids is a viable management practice for agriculture, but minimal information exists on beneficial uses for native rangeland. This study was conducted to determine the effect of surface‐applied biosolids on the canopy cover, aboveground biomass, and nutrient status of native plant species in a sagebrush (Artemisia spp.) community in western Colorado. Biosolids were applied once in 1991 at nine rates consisting of 0, 5, 10, 15, 20, 25, 30, 35, and 40 Mg ha−1 to plots measuring 3320 m2. Biosolids application increased the biomass of perennial grasses up to 300% at 25 Mg ha−1 treatment rates in 1993. We also found 60 to 70% increases in plant tissue N concentrations in western wheatgrass (Agropyron smithii Rydb.), bluebunch wheatgrass [A. spicatum (Pursch) Scribn. & Smith], and Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker]. The quality of grass forage was also improved through a change in the Cu/Mo ratios. Before biosolids application, the three grasses noted above had Cu/Mo ratios below 1.2/1, which is known to cause Mo‐induced Cu deficiencies in cattle (Bovis abortus), sheep (Ovis aries), and some wild ruminants. Biosolids treatment increased the Cu/Mo ratio above 2/1 for western wheatgrass and bluebunch wheatgrass 1 yr after application at low rates and 2 yr after amendment at intermediate application rates. The Cu/Mo ratio of Indian ricegrass also increased above 2/1 2 yr after surface application at intermediate biosolids application rates. Forage quantity and nutritional value of some native grasses was improved for livestock and wildlife consumption with biosolids application.
Humic‐Acid Transformation during Composting of Municipal Solid Waste
Authors: Chefetz Benny , Adani Fabrizio , Genevini Pierluigi , Tambone Fulvia , Hadar Yitzhak , Chen Yona
Published: July 2010

Composting of municipal solid waste (MSW) was studied in an attempt to characterize concomitant transformations of humic acid (HA). Humic acid and Core‐HA were extracted from MSW at various stages during composting using the following methods: (i) The common IHSS method (HA); and (ii) performing organic solvent and sulfuric acid extractions prior to the alkaline extraction (Core‐HA). Mass balance was calculated for each compost sample during composting, and cross polarization magic angle spinning (CPMAS) 13C‐NMR and fourier transform infrared (FTIR) spectroscopy measurements were employed on the purified HAs and Core‐HAs. The absolute level of HA decreased during composting by 50% whereas the level of Core‐HA was steady throughout the process. The 13C‐NMR and FTIR spectra of the HAs indicated a high rate of change in structure during composting. The aromatic and phenolic C‐containing groups increased by 23 and 16%, respectively. In contrast, the Core‐HA spectra were stable, with only minor changes recorded during composting. The “coating” materials (polysaccharides, peptides, and lipids) bonding to the “core” HA structure degraded during composting, resulting in HA structures of higher aromaticity. The FTIR spectra of both HA and Core‐HA exhibited minor peaks in the carboxyl C, and the high rate of aliphatic C‐containing groups recorded from the 13C‐NMR spectra resembled “young” (type III) humified materials from soils. The mass‐balance data, together with the spectroscopic analyses indicate that one of the major HA transformation processes occurring events during the process is the degradation of the coating materials, yielding the core HA structure.
Extractable Trace Elements in the Soil Profile after Years of Biosolids Application
Authors: Barbarick K. A. , Ippolito J. A. , Westfall D. G.
Published: July 2010

The U.S. Environmental Protection Agency (USEPA) and some state agencies regulate trace element additions to soil from land application of biosolids. We generally consider trace elements added in biosolids (sewage sludge) to accumulate in the soil surface without significant transport below the plow layer. We used 11 yr of field‐study information from biosolids addition to dryland hard red winter wheat (Triticum aestivum L. “Vona” or “TAM107”) to determine the distribution of NH4HCO3 diethylenetriaminepentaacetic acid (AB‐DTPA)‐extractable Cd, Cr, Cu, Mo, Ni, Pb, and Zn in 0 to 20 (plow layer), 20 to 60, 60 to 100, and 100 to 150 cm depth increments. This study is unique since it involves multiple biosolids application in a dryland summer fallow agroecosystem. We applied five or six applications of biosolids from the cities of Littleton and Englewood, CO, to Weld loam (a fine, montmorillonitic, mesic Aridic Paleustoll) or Platner loam (a fine, montmorillonitic, mesic Aridic Paleustoll) at four locations. This paper focuses on the 0 (control), the 56 or 67 kg of N ha−1 fertilizer rates, and the 6.7 and 26.8 dry Mg of biosolids ha−1 rates that we added every crop year. We observed significant (P < 0.10) accumulations of the trace elements in the plow layer of the biosolids‐amended soils. Only Zn showed consistent increases in extractable levels below the plow layer at all four sites. The biosolids Zn concentration (average of ∼1300 mg kg−1) was larger than any other trace element resulting in larger loading of this element.
Analysis of Metal‐EDTA Complexes by Electrospray Mass Spectrometry
Authors: Baron Dirk , Hering Janet G.
Published: July 2010

Solutions of the strong complexing agent ethylenediaminetetraacetic acid (EDTA) and Cu, Pb, Cd, Al, and Fe(III) were examined by electrospray mass spectrometry (ES/MS). Uncomplexed EDTA and metal‐EDTA complexes survive the electrospray process intact and can be detected simultaneously by mass spectrometry. Best sensitivity was achieved in the positive ion mode in which EDTA and EDTA‐metal complexes (present in solution as anions) were detected as protonated species with a single positive charge. Except for the protonation, the aqueous metal‐EDTA complexes are preserved and neither fragmentation of complexes nor formation of clusters with more than one metal or ligand were observed in the mass spectra. Detection limits are between approximately 1 to 2 µM for uncomplexed EDTA and for the Cu‐EDTA and Pb‐EDTA complexes, with a linear range up to 10−4 M. Calibrations based on solutions with equimolar concentrations of EDTA and Cu or Pb can be used to quantify EDTA‐metal complexes in solutions with excess EDTA or metal, and in solutions with more than one metal present. Isotopic signatures of metals in the metal‐ligand complexes are preserved, allowing the identification of the metal in a metal‐ligand complex. Isotopic signatures of metals can therefore aid in the identification of metal‐ligand complexes in unknown samples.
Ponderosa Pine Tree Rings as Historical Monitors of Zinc and Cadmium Pollution
Authors: Schaumloffel John C. , Filby Royston H. , Moore Barry C.
Published: July 2010

Concentrations of Zn and Cd were determined in growth rings of 13 ponderosa pines (Pinus ponderosa Dougl.) from two watersheds impacted by the discharge of heavy‐metal laden waste. Trees growing along rivers with contaminated sediments have greater concentrations of Zn and Cd than trees growing at uncontaminated reference sites. Concentrations of Zn and Cd in trees from the Coeur d'Alene region (Idaho, USA) decline progressively in younger growth rings. This indicates that reductions in mining activity and implementation of pollution control technologies have reduced Zn and Cd loading in this system. Samples from the Coeur d'Alene region contain Zn and Cd concentrations greater than those found trees from contaminated sites in the Lake Roosevelt (Washington, USA) region. Clearly, the effects of soil and other environmental conditions cannot be accounted for over the past 60 yr. However, dendrochemical analyses suggest that heavy‐metal sulfide wastes in the Coeur d'Alene region have a greater susceptibility to mobilization than siliceous slag wastes in Lake Roosevelt. Concentrations of Zn and Cd measured in a tree growing along an intervening river suggest that Zn and Cd from the Coeur d'Alene basin are diluted before reaching Lake Roosevelt. Radial translocation of Zn and Cd to the heartwood cannot be excluded as a possible influence on elemental distribution of Zn and Cd in ponderosa pine. Nonetheless, the data demonstrates that ponderosa pine can effectively integrate mobile Zn and Cd present in their environment during wood formation.
Groundwater Quality under Conventional and No Tillage: I. Nitrate, Electrical Conductivity, and pH
Authors: Patni N. K. , Masse L. , Jui P. Y.
Published: July 2010

The use of conservation tillage is increasing in North America, but information on its effect on water quality in cold climatic regions is limited. To obtain such information, the effect of no‐tillage (NT) and conventional tillage (CT) treatments on nitrate‐nitrogen (NO3‐N) concentration, specific electrical conductivity (EC), and pH in shallow groundwater (1.2, 1.8, 3.0, and 4.6 m depths) was studied over four successive crop years in corn fields (loam soil) of approximately 3 ha each, located in eastern Ontario. Water table elevation was also monitored during three crop years. Average NO3‐N concentration at the 1.2, 1.8, and 4.6 m depths was consistently higher under CT than under NT in every crop year and every season. However, the effect of tillage was not significant at P < 0.05. Nitrate concentration decreased significantly with depth. It was about two to three times the drinking water limit of 10 mg/L as NO3‐N at the 1.2, 1.8, and 3.0 m depths. At the 4.6 m depth, NO3‐N concentrations were mostly low but increased with time. Changes in water table elevation appeared to affect NO3‐N concentrations at the 1.2 m depth under NT only. At a given depth, EC and pH of groundwater were not affected by tillage treatment. However, within each tillage treatment, values increased significantly with depth. Results from this study indicated a large spatial variability in NO3‐N and EC values in groundwater, which could have masked small tillage effects. More intensive temporal and spatial sampling may be required to establish tillage treatment effects, if any.
Spatial and Temporal Variability of Phosphorus Retention in a Riparian Forest Soil
Authors: Lyons Jodi B. , Görres Josef H. , Amador José A.
Published: July 2010

Riparian zones remove P from surface runoff and can act as filters of nonpoint source (NPS) P pollution for surface waters. Riparian forest soils were investigated in spring and fall for their capacity to retain PO3−4‐P. Samples (300 on each date) were taken from a soil drainage catena from moderately well (MWD), somewhat poorly (SPD), and poorly drained (PD) soil in May and November of 1995 to examine spatial and temporal variability of P retention and its relationship to soil properties. The equilibrium P concentration at zero sorption (EPC0) was determined for each sampling point (lower EPC0, = higher P retention capacity). Mean (coefficient of variation, CV) EPC0 values were 3.8 (0.49) mg P L−1 in May and no P sorption was apparent in November for SPD soil, 1.0 (1.34) and 1.5 (1.03) P L−1 in May and November, respectively for MWD soil, and 0.5 (1.87) and 1.3 (1.13) mg P L−1, respectively for PD soil. The EPC0 was significantly and positively correlated to organic matter (OM) for all drainage classes on both dates. Low EPC0 values—high P retention capacity—in MWD and PD soil corresponded with high Feox and Alox values. For SPD soil, high mean EPC0 corresponded with low mean Feox and Alox values. The relationship between EPC0 and Feox and Alox was described by a hyperbolic function for MWD and PD soil, but not for SPD soil. The EPC0 did not exhibit spatial structure at the sampling scale used for any of the drainage classes, even though Feox, Alox, and OM content showed spatial structure.
Kinetics and Modeling of Dissolved Phosphorus Export from a Tile‐Drained Agricultural Watershed
Authors: Xue Yuan , David Mark B. , Gentry Lowell E. , Kovacic David A.
Published: July 2010

Agricultural runoff can be a source of P, a limiting factor for freshwater eutrophication. To develop a simple method to estimate P export from the cropland, we studied 1.2‐µm filtered dissolved phosphorus (DP) output from four tiles draining areas ranging from 8 to 25 ha, and from a river draining a 48 173 ha watershed in east‐central Illinois during 1993 to 1996. The land was under maize (Zea mays L.)‐soybean (Glycine max L.) rotation. The tiles were estimated to contribute more than 86% of the river flow and 65 to 69% of the river DP export during 1995 to 1996. The DP load from tiles followed consecutive pseudo first‐order kinetics in terms of tile flow (DP load depended on the amount of DP remaining in the soil matrix). The kinetic curves indicated a soluble‐inorganic‐P pool that was quickly depleted and replenished. In contrast, for DP export from the river at the watershed scale we observed pseudo zero‐order kinetics based on river flow (DP export was independent of how much DP remained in the watershed). The contribution from numerous tiles and surface runoff to the river may have stabilized DP export at the watershed scale and therefore could explain the different kinetic orders. For the study watershed, a one parameter equation could estimate watershed‐wide DP export: k′ × (surface water discharge from the watershed) × (watershed area), with k′ being 3.94 × 10−6 mg P L−1 ha−1. Our approach should be tested in watersheds with different geographic and agricultural characteristics.
Decomposition of Blackberry and Broomsedge Bluestem as Influenced by Ozone
Authors: Kim J.S. , Chappelka A. H. , Miller‐Goodman M. S.
Published: July 2010

Many researchers have reported on individual plant responses to O3, but few have investigated the effects of this pollutant on ecosystem function. Our investigation examined the influence of O3 on short‐term (Phase I) litter decomposition of blackberry (Rubus cuneifolus Pursh.) and broomsedge bluestem (Andropogon virginicus L.), two plant species native to early successional forest communities in the southern USA. Mixed blackberry/broomsedge litter (1:1) collected from plants exposed to different levels of O3 for one growing season was placed in open‐top chambers and exposed to different O3 levels of treatments for 24 wk. Litter also was incubated in microcosms in the laboratory at 25 or 30°C to determine the effects of climate change on O3‐treated litter. Initial C and N concentrations of the collected foliage did not differ significantly among treatments for either species. Blackberry litter had approximately twice as much N as broomsedge, and when collected from 2X O3 chambers, had significantly greater permanganate lignin than the other treatments. Initial permanganate lignin concentration of blackberry, over all O3 treatments, correlated significantly with remaining mass of the litter mixture after 24 wk exposure. Litter decomposed more slowly in the 2X chambers than in the other treatment chambers, regardless of litter source. Elevated O3‐exposed litter (2X) decomposed the slowest regardless of treatment applied. There were significant temperature and time effects observed with litter decomposition; litter incubated at 30°C decomposed faster than at 25°C. Our data suggest O3 may influence substrate quality and microbial activity, thus reducing the rate of litter decomposition in early successional forest communities.
Transplanting Native Plants to Revegetate Abandoned Farmland in the Western Mojave Desert
Authors: Grantz David A. , Vaughn David L. , Farber Robert J. , Kim Bong , Ashbaugh Lowell , VanCuren Tony , Campbell Rich , Bainbridge David , Zink Tom
Published: July 2010

Nursery‐grown, native plant species have potential application for revegetating disturbed arid and semiarid lands. We evaluated nursery‐grown fourwing saltbush [Atriplex canescens (Pursh) Nutt.], allscale saltbush [A. polycarpa (Torrey) S. Watson], bladderpod (Isomeris arborea Nutt.), honey mesquite [Prosopis glandulosa Torrey var. torreyana (L. Benson) M. Johnston], and rubber rabbitbrush [Chrysothamnus nauseosus (Pallas) Britton] transplanted to abandoned agricultural land throughout the western Mojave Desert. Two types of temporary plant enclosure for herbivory and environmental protection (plastic cones and wire cages) and three mulch treatments (straw, bark, and none) were tested at all six sites. Rubber rabbitbrush was difficult to propagate in the nursery and is not recommended for transplanting. Significant differences in plant performance occurred between sites with similar aerial environments but contrasting degrees of edaphic disturbance. Plastic cones were significantly superior to wire cages for plant vigor and survival but no differences were detected between mulch treatments. Fourwing saltbush was generally successful over all treatments and sites and is recommended for transplanting in this area. In a larger plot study, narrow augered holes led to superior survival of honey mesquite relative to wide, hand‐dug holes, and plastic cones were superior to wire cages. Mortality of all species was high due to dry, but not atypical, weather during the 2 yr of the study. We conclude that transplanting without intensive irrigation does not guarantee survival of even the most successful species. Its greater cost relative to direct seeding may not be warranted for large‐scale restoration of arid and semiarid environments.
Airborne Elements, Cell Membranes, and Chlorophyll in Transplanted Lichens
Authors: Garty J. , Cohen Y. , Kloog N.
Published: July 2010

The objective of the present study was to test the concentration of airborne mineral elements in the lichen Ramalina lacera (With.) J.R. Laund. in comparison with its physiological status. Thalli of Romalina lacera were collected in a remote unpolluted site and transplanted in a polluted region for 10 mo. An analysis of 20 elements in addition to an analysis of the status of cell membranes and the integrity of chlorophyll was performed after this period of transplantation. The lichen manifested a great potential for the accumulation of Pb, V, Ni, Zn, and Cu. Potassium and P were found to leach out. High concentrations of Ni, Mg, and B coincided with damage caused to cell membranes. The integrity of chlorophyll correlated with the concentration of K and correlated inversely with the concentration of Cr, Fe, Mn, Ni, Pb, and B.
Soil‐Climate Effects on Nitrate Leaching from Cattle Excreta
Authors: Stout W. L. , Gburek W. J. , Schnabel R. R. , Folmar G. J. , Weaver S. R.
Published: July 2010

Management intensive grazing (MIG) is a grazing system in which animals at a high stocking density are rotated through several paddocks at short time intervals (12–24 h) so that animal performance is maximized. Although MIG has the potential to increase dairy farm profitability in the northeast USA, recent work in this region has shown that a substantial amount of N recycled through urine is leached below the root zone. How soil properties, particularly water‐holding capacity, can affect NO3‐N leaching from beneath urine and feces spots under the climatic conditions of the northeast USA is not known. We conducted a field study to measure NO3‐N leaching loss from spring‐, summer‐, and fall‐applied urine and summer applied feces beneath N‐fertilized orchardgrass (Dactyls glomerata L., cv. Pennlate) using large drainage lysimeters installed in two soils that differed greatly in soil water storage capacity. The study sites were located in central Pennsylvania on a Hagerstown silt loam soil (fine, mixed, mesic Typic Hapludalf) and a Hartleton channery silt loam (loamy‐skeletal, mixed, mesic Typic Hapludult). Compared to the Hagerstown soil, the Hartleton soil provided an 85% decrease in plant N uptake, a 52% increase in leachate volume, but no significant increase in NO3‐N leaching beneath urine spots. However, the lower soil water‐holding capacity of the Hartleton soil caused the NO3‐N leaching losses to be more evenly distributed over the year.
Herbicide Distribution and Variability Across Goodwater Creek Watershed in North Central Missouri
Authors: Donald W. W. , Hjelmfelt A. T. , Alberts E. E.
Published: July 2010

One objective of the Missouri Management Systems Evaluation Area was to monitor and assess surface water quality, including spatial and temporal variability in herbicide concentrations within the 7250 ha Goodwater Creek Watershed. Stream water was sampled at all stream‐road intersections across the watershed on 10 occasions in 1993 and 1994. Maps of herbicide distribution established that widespread, seasonal contamination of streams in Goodwater Creek Watershed was due to nonpoint sources (e.g., widespread, but normal farm use) rather than from point sources. Box plots documented concentration variability over time. Concentrations of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), deethylatrazine [2,4‐diamino‐6‐chloro‐N‐(1‐methylethyl)‐1,3,5‐triazine], deisopropylatrazine [2,4‐diamino‐6‐chloro‐N‐ethyl‐1,3,5‐triazine], and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] were also monitored at least weekly from 1993 to 1994 at three V‐notch weirs through which 16.7, 43.4, and 100% of the watershed drained. Atrazine, deethylatrazine, and metolachlor were detected year round at concentrations above 0.1 µg/L. Atrazine concentrations observed at weirs were occasionally >100 µg/L and were similar to edge‐of‐field concentrations observed elsewhere shortly after spraying in May to June, probably because the watershed's poorly drained, silt loam soils contain a restrictive claypan horizon that limits infiltration and encourages surface runoff.
Nitrate Losses from a Corn‐Alfalfa Rotation: Lysimeter Measurement of Nitrate Leaching
Authors: Toth John D. , Fox Richard H.
Published: July 2010

An array of 18 zero‐tension pan lysimeters installed 1.2 m below the soil surface in 1988 was used to examine NO3 leaching in 1991 to 1995. The experiment was designed to study NO3 losses from continuous, fertilized corn, alfalfa, and the first year of corn rotated from alfalfa as a function of crop type, applied N fertilizer rate and longer‐term weather variability. The flow‐weighted mean leachate NO3‐N concentration from the 3‐yr alfalfa stand was 4 mg L−1. Annual leachate NO3‐N concentrations from continuous, fertilized corn and corn following alfalfa at the estimated Economically Optimum N (EON) rate averaged 15 mg L−1. Annual flow‐weighted average NO3‐N concentrations in leachate from post‐alfalfa corn receiving 50 and 100 kg N ha−1, which were above the EON rate, were 18 and 24 mg L−1, respectively. The masses of NO3‐N leached from the root zone of continuous corn at the estimated EON rate were 81 and 55 kg ha−1 in 1991 to 1992 and 1994 to 1995, respectively. Nitrate‐N losses from alfalfa in 1991 to 1992 were 9 kg ha−1. Nitrate concentrations in leachate from an alfalfa stand were one‐quarter to one‐fifth as high as from corn receiving the EON rate. This research provides evidence that including alfalfa in a rotation would result in a considerable reduction in the amount of NO3 leaving a farm in leachate.
How Humic Substances Dominate Mercury Geochemistry in Contaminated Floodplain Soils and Sediments
Authors: Wallschläger Dirk , Desai Madhukar V. M. , Spengler Markus , Windmöller Cláudia Carvalhinho , Wilken Rolf‐Dieter
Published: July 2010

The interaction of mercury (Hg) and humic substances (hs) was studied in floodplain topsoils and surface sediments of the contaminated German river Elbe. An intimate coupling exists between the geochemical cycles of Hg and organic carbon (OC) in this ecosystem. Humic substances exert a dominant influence on several important parallel geochemical pathways of Hg, including binding, transformation, and transport processes. Significant differences exist between the Hg‐hs associations in floodplains and sediments. Both humic acids (ha) and fulvic acids (fa) contribute to Hg binding in the sediments. In contrast, ultrafiltration experiments proved that Hg in the floodplain soils is almost exclusively bound to very large humic acids (ha) with a nominal molecular weight (MW) >300 000. Successive cation and anion exchange experiments demonstrated that those Hg‐ha complexes are inert toward competition by other cations, and also apparently predominantly electroneutral. Speciation transformation reactions in the solid phase were investigated by sequential extraction and thermal release experiments. Upon addition of Hg model compounds to a sediment matrix, all species were transformed to the same new speciation pattern, regardless of their original speciation. The accompanying alterations in availability and solubility were partially due to interconversion between the different Hg redox states, including Hg(I). Simultaneously, partial transformation of added Hg2+ into volatile Hg compounds (35% in 10 d) was observed. Finally, Hg association with water‐soluble ha continuously increased downstream, indicating that hs play a key role in both lateral and longitudinal Hg transport in the Elbe ecosystem.
The Phytoavailability of Cadmium to Lettuce in Long‐Term Biosolids‐Amended Soils
Authors: Brown Sally L. , Chaney Rufus L. , Angle J. Scott , Ryan James A.
Published: July 2010

A field study was conducted to assess the phytoavailability of Cd in long‐term biosolids‐amended plots managed at high and low pH. The experiment, established 13 to 15 yr prior to the present cropping, on a Christiana fine sandy loam soil (a clayey, kaolinitic, mesic Typic Paleudult) used a variety of biosolids. Two of the biosolids had total Cd concentrations of 13.4 and 210 mg kg−1. A Cd salt treatment, with Cd added to soil at a rate equivalent to the Cd added by the higher Cd biosolids applied at 100 Mg ha−1, was also included. The lettuce (Lactuca sativa var. longifolia) cultivar (Paris Island Cos) used in the initial study was also used in the current study. Lettuce Cd was compared between treatments, and in relation to the soil Cd/soil organic C (OC) ratio. There has been no significant increase in plant Cd since the initial cropping. With 16% of the biosolids added OC remaining, lettuce grown on the soil amended with the more contaminated biosolids was not different than that of the initial cropping. Further, significantly less Cd was taken up by lettuce grown on biosolids‐amended soil than lettuce grown on soil amended with equivalent rates of Cd salt. The Cd concentration in lettuce grown in the low Cd biosolids treatment was not different from the control. These results indicate that the potential hazards associated with food chain transfer of biosolids‐applied Cd are substantially lower than equivalent Cd salt treatments, and that the hazards do not increase over time.
Constrained Optimization of Spatial Sampling using Continuous Simulated Annealing
Authors: van Groenigen J. W. , Stein A.
Published: July 2010

Spatial sampling is an important issue in environmental studies because the sample configuration influences both costs and effectiveness of a survey. Practical sampling constraints and available preinformation can help to optimize the sampling scheme. In this paper, spatial simulated annealing (SSA) is presented as a method to optimize spatial environmental sampling schemes. Sampling schemes are optimized at the point‐level, taking into account sampling constraints and preliminary observations. Two optimization criteria have been used. The first optimizes even spreading of the points over a region, whereas the second optimizes variogram estimation using a proposed criterion from the literature. For several examples it is shown that SSA is superior to conventional methods of designing sampling schemes. Improvements up to 30% occur for the first criterion, and an almost complete solution is found for the second criterion. Spatial simulated annealing is especially useful in studies with many sampling constraints. It is flexible in implementing additional, quantitative criteria.
Greenhouse Gas Fluxes following Tillage and Wetting in a Wheat‐Fallow Cropping System
Authors: Kessavalou Anabayan , Doran John W. , Mosier Arvin R. , Drijber Rhae A.
Published: July 2010

Little is known about the relative contributions of episodic tillage and precipitation events to annual greenhouse gas emissions from soil. Consequently, we measured carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes from soil in wheat‐fallow cropping system in western Nebraska using vented surface chambers, before and immediately after tillage and wetting with 5.1 cm of water, during the fallow period in 1995/1996. Replicated fallow management treatments included no‐tillage, subtillage, and plow representing a wide range in degree of soil disturbance. Soil bulk density, water‐filled pore space, electrical conductivity (EC1:1), nitrate (NO3), and pH within the top 30.5 cm soil, and soil temperature at 0 to 7.6 cm were measured to assess their correlation with variations in gas flux and tillage and wetting. Atmospheric concentrations above the soil (at ~40 cm) increased by 15% for CO2 and 9 to 31% for N2O and 6 to 16% for CH4 within 1 min after tillage and returned to background concentrations within 2 h. Except immediately after tillage, net CH4 flux was negative, from the atmosphere into soil, and is referred to as CH4 uptake. Overall, increases (1.5–4‐fold) in CO2 and N2O losses from soil, and CH4 uptake by soil were short lived and returned to background levels within 8 to 24 h after tillage. Losses of CO2 and N2O increased to 1.7 and 5 times background emissions, respectively, for 24 h following wetting, while CH4 uptake declined by about 60% for 3 to 14 d after wetting. Water‐filled pore space in the surface soil fell below 60% within 24 h after saturation and exhibited an inverse relationship (R2 = 0.66) with CH4 uptake. A significant decline in soil NO3 and EC1:1 in the top 7.6 cm occurred following wetting. Under our experimental conditions, and the expected frequency of tillage and wetting events, failure to include these short‐lived episodic gas pulses in annual flux estimations may underestimate annual CO2 and N2O loss up to 13 and 24%, respectively, and overestimate CH4 uptake by up to 18% in this cropping system.
Biopore Mediated Subsurface Transport of Dissolved Orthophosphate
Authors: Jensen Marina Bergen , Jørgensen Peter R. , Hansen Hans Christian Bruun , Nielsen Niels Erik
Published: July 2010

Leaching of phosphorous (P) from structured agricultural soil may cause eutrophication of receiving fresh waters. Especially subsurface storm flows seem capable of subsurface transfer of surface‐located P. We used 32P‐autoradiography to trace preferential pathways supporting dissolved orthophosphate (Pi) transport through an undisturbed column of water‐saturated clayey subsoil (Aerie Giossaqualf, 0.48 m diam., height 0.73 m, water content 50.2 L). At a flow rate near the saturated hydraulic conductivity (Ksat) of the column, a pulse of 32P was applied to the column surface. To stain the water flow paths a pulse of Brilliant Blue dye was applied afterwards. Upon drainage, hyperfilms sensitive to 32P‐radiation were exposed horizontally at four depths within the upper 15 cm; below this depth a Geiger‐Müller detector showed no increased radioactivity. The 32P‐sorption pattern appearing on the hyperfilms consisted of discrete, circular spots, which coincided with the position of larger biopores (diam. >3 mm). In contrast, the water infiltration pattern depicted by the dye tracer was not restricted to biopores, but covered much larger areas of the column cross sections. Solute transport was further characterized by analyzing breakthrough curves of pulse‐applied 32P and tritium. The results of the study suggest that only macropores with wide apertures can provide the necessary conditions for vertical long distance transport of Pi through structured soil. Estimates suggest the rate‐limiting step of the Pi‐sorption process to be the diffusion from central stream tubes to sorption sites at macropore wall. Nonequilibrium caused by this sorption barrier is termed macropore nonequilibrium (MNE).
Spatial and Temporal Variations in Nitrate Contamination of a Rural Aquifer, California
Authors: Williams A. E. , Johnson J. A. , Lund L. J. , Kabala Z. J.
Published: July 2010

The quality of ground water in the Sierra Pelona watershed, California is examined as an example of a small rural groundwater basin in a mountainous area of arid climate. Water quality in this region has been seriously impacted by nitrate (NO3) contamination with 42% of wells sampled exceeding the EPA public drinking water maximum contaminant level (MCL) of 10 mg/L as NO3‐N at some point during 1992–1993. High NO3‐N concentrations reported from this region suggest degradation of water quality due to anthropogenic activity. Dissolved ion concentrations, particularly NO3, chloride and calcium varied radically in 55% of well waters sampled prior to, following, and months after an unusually wet winter. Our extensive well sampling program, chemical results and delineation of spatial and temporal NO3‐N variation allow us to constrain possible contamination sources and transport mechanisms active in the Sierra Pelona basin. The spatial distribution and temporal variability of NO3 indicate three patterns of contamination: (i) isolated wells impacted by numerous, localized NO3 sources which erratically affect a single well without significantly contaminating neighboring ones; (ii) a tight cluster of wells, unusually low in other ions but consistently high in NO3; (iii) moderate and generally consistent NO3 concentrations, found over a large, diffuse region of the Sierra Pelona alluvial aquifer. An understanding of the differing NO3 source(s) and contamination mode(s) that contribute to these observed contaminant patterns is critical to development and success of any strategy for contaminant mitigation and/or remediation.
Nitrogen and Phosphorus in Surface Runoff and Sediment from a Wheat‐Pea Rotation in Northeastern Oregon
Authors: Douglas C. L. , King K. A. , Zuzel J. F.
Published: July 2010

Runoff and erosion from cultivated fields are suggested as major sources of nitrogen (N) and phosphorus (P) entering lakes and streams. Loss of these nutrients can be impacted by soil and crop management practices. There is relatively little information on nutrients leaving agricultural fields in the dryland areas of the Pacific Northwest, especially as impacted by different crops and crop rotations. Nutrients in surface runoff and soil leaving a series of plots in northeast Oregon were evaluated for 5 yr. Objectives were to evaluate the effects of a wheat‐pea (Triticum aestivium L.‐Pisum sativum L.) rotation on N and P in surface runoff and eroded soil. Cumulative N and P lost in runoff were less than 3 and 0.2 kg ha−1, respectively. Total N lost from continuous fallow (CF) plots, even though they were never fertilized, ranged from 20 to 100 kg ha−1 yr−1. This was much more N than was lost from winter wheal (WW) (5–70 kg ha−1 yr−1) and spring pea (SP) (25–40 kg h−1 yr−1), because there was much more sediment loss from CF than from WW or SP plots. The same scenario occurred with P as with N, with loss from CF of 8 to 48 kg ha−1 yr−1, WW of 2 to 28 kg ha−1 yr−1, and from SP of 8 to 16 kg ha−1 yr−1. All fertilizer was surface‐applied and 25 to 76% of the fertilizer applied was lost in 5 yr, depending on the time of fertilizer application and the type of crop growing. Nutrient loss from these fields can be controlled by controlling soil erosion.
Evaluation of a Stepwise Procedure for Comparative Validation of Pesticide Leaching Models
Authors: Thorsen Mette , Jørgensen Peter R. , Felding Gitte , Jacobsen Ole H. , Spliid Niels H. , Refsgaard Jens Christian
Published: July 2010

Four pesticide leaching model codes (PELMO, PESTLA, MACRO, and MIKE SHE) were evaluated and compared through a rigorous validation procedure combined with the application of statistical evaluation criteria. The validation procedure followed a strict Stepwise approach based on suggestions put forward by a European work group on regulatory use of pesticide models (FOCUS). The experimental background comprised two different types of data sets. A laboratory and field lysimeter experiment were conducted on a Danish macroporous sandy loam soil. The aim of the study was to evaluate whether a priori model calibration on controlled laboratory data could improve the physical description of the flow and solute transport in the soil and hence the performance of uncalibrated models for predictions of field lysimeter data. The validation procedure proved to be valuable in terms of ensuring process‐based evaluation of model performances and consistent model comparisons. Controlled laboratory experiments and lysimeter experiments consistently showed very significant influence of preferential flow on water and solute transport. Model codes including a description of preferential flow processes (MACRO and MIKE SHE) required less calibration efforts to meet the selected performance criteria on the investigated soil type than those without such description (PELMO and PESTLA).
Seeding Native Plants to Restore Desert Farmland and Mitigate Fugitive Dust and PM10
Authors: Grantz David A. , Vaughn David L. , Farber Rob , Kim Bong , Zeldin Mel , VanCuren Tony , Campbell Rich
Published: July 2010

Windblown fugitive dust contributes to violations of air quality standards for particulate matter <10 pm aerodynamic diameter (PM10). In the western Mojave Desert of California, approximately 1070 ha of previously filled or over‐grazed land impacted downwind metropolitan areas by wind‐driven emissions of dust. A protocol of furrowing across the wind and direct seeding of three native perennial shrubs and a bunch grass helped reduce fugitive dust emissions in this area by more than 95%. Seeded species varied from 35 to 97% of living plant cover in individual years, reflecting rainfall patterns. In areas of deep sand, Indian ricegrass (Achnatherum hymenoides Roemer & Shultes) outperformed the shrubs, while fourwing saltbush [Atriplex canescens (Pursh) Nutt.] exhibited the most widespread establishment. This revegetation was achieved in an anomalous year with above average and late rainfall that eliminated early competition from annual species and later fostered abundant shrub growth. This success was not reproducible in more normal years, when minimal disturbance protocols such as broadcasting of seed on the untilled soil surface were as effective and less costly. We conclude: (i) direct seeding can lead to plant establishment in favorable years, but is likely to fail in any given year, (ii) direct seeding should be implemented with little soil disturbance, (iii) the native fourwing saltbush is the most likely species to become established in this environment, and (iv) unpredictable rainfall and temperature require that direct seeding be backed up with alternative strategies to achieve reliable dust and PM10 mitigation in arid environments.
Field‐Scale Nitrogen and Phosphorus Losses from Hayfields Receiving Fresh and Composted Broiler Litter
Authors: Vervoort R. W. , Radcliffe D. E. , Cabrera M. L. , Latimore M.
Published: July 2010

Composting broiler litter may increase the amount of stable organic components and reduce contamination of ground‐ and surface‐water with N and P from excessive land applications. Limited research has been done comparing field‐scale losses of nutrients from broiler litter applied to hayfields. This project determined field‐scale N and P runoff losses from fresh and composted litter applied to hayfields. Two rates of broiler litter, 10 Mg ha−1 yr−1 (1X) and 20 Mg ha−1 yr−1 (2X), and a mix of 10 Mg ha−1 yr−1 of broiler litter and 50 Mg ha−1 yr−1 of composted litter (1X + C), were split‐applied in April and September for 2 yr. Surface runoff and subsurface flow were monitored for inorganic and total N and P. Nitrate concentrations in subsurface flow remained below the USEPA standard of 10 mg L−1 for all treatments. Average dissolved reactive P (DRP) concentrations were statistically higher under the 1X + C treatment, followed by the 2X and 1X treatments, reaching a maximum of 8.5 mg L−1 under the 1X + C treatment. Differences between field and plot‐scale results were most likely controlled by the timing of application and occurrence of the first rainfall event. Concentrations of resin‐extractable P (Pr) in soil increased under all treatments, indicating accumulation of P after only 2.5 yr of application. In this research, the amount of P applied was the principal determinant of the DRP concentration in the surface runoff. Composting broiler litter increased the amount of stable organic components.
Distribution of Trace Elements in Soil from Repeated Sewage Sludge Applications
Authors: Berti W. R. , Jacobs L. W.
Published: July 2010

We studied the horizontal and vertical distribution in a soil profile (Metea sandy loam; loamy, mixed, mesic Typic Hapludalf) of trace elements as a result of their loading at phytotoxic levels to cropland. Municipal sludges containing high concentrations of Cd, Cr, Cu, Pb, Ni, and Zn were applied to cropland from 1977 to 1986 at three rates plus an untreated control. Total elemental analysis of soils collected in 1989 and 1990 indicated that lateral distribution of trace elements had occurred. This lateral distribution was most likely a result of the physical movement of soil particles with agronomic operations. The elements, however, were not distributed below the sampling depth of from 15 to 30 cm. Mass balance calculations resulted in average trace element recoveries that ranged from 45 to 155% of the total applied. These calculations were highly variable, indicative of the highly variable nature of sludge composition, lack of total uniform sludge applications, soil movement due to tillage operations, and sampling methods. Because of the potential errors associated in mass balance calculations, recoveries that have been calculated in this and other studies that deviate substantially from 100% should reasonably be expected. Direct examination of the relatively few ways in which trace elements are lost from a soil (i.e., plant uptake, soil movement via tillage, water and wind erosion, and deep leaching) may be more meaningful than mass balance calculations to determine the fate of trace elements applied to soil.
Reduction of Selenite to Elemental Selenium by Enterobacter cloacae SLD1a‐1
Authors: Dungan R. S. , Frankenberger W. T.
Published: July 2010

The facultative anaerobic bacterium Enterobacter cloacae strain SLD1a‐1 (ATCC‐700258) was studied in washed cell suspensions to assess optimal conditions required for the reduction of selenite (SeO32−) to elemental selenium (Se0). Enterobacter cloacae using glucose (1.4 mM) as an electron donor removed 79% of the added SeO32−(7.9 mM) from solution in 2.5 h. Optimal SeO32− reduction occurred at a pH of 6.5 and a temperature of 40°C. Carbohydrate sources arabinose, xylose, and sorbose were found to significantly enhance SeO32− reduction over that of glucose. The reduction of SeO32− at 7.9 mM was inhibited by nitrate at levels 1 to 100 times greater, nitrite at levels 5 and 10 times greater, while sulfite at levels of two to four times greater was found to stimulate the reduction of SeO32−. Enterobacter cloacae grows on anaerobically incubated plates containing NO3− as the sole terminal electron acceptor and acetate as the electron donor. Use of SeO32− as the terminal electron acceptor during anaerobic respiration did not support growth and could only be reduced to Se0 when NO3− was present.
Sorption, Degradation, and Mineralization of Carbaryl in Soils, for Single‐Pesticide and Multiple‐Pesticide Systems
Authors: Nkedi‐Kizza P. , Brown K. D.
Published: July 2010

Sorption, degradation, and mineralization of carbaryl (1‐naphthyl N‐methylcarbamate) alone and in mixtures with atrazine(2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) and diuron (N′‐(3,4‐dichlorophenyl)‐N,N‐dimethylurea) were characterized for two topsoils and their respective subsoils. In general, differences in sorption and transformation between single and multiple‐pesticide systems were less than differences due to soil type and between topsoil and subsoil. For a given soil, the topsoil containing more organic carbon (OC) than the subsoil exhibited a larger value for the Freundlich sorption coefficient (Kt). Similarly, a larger value for the soil solution degradation rate coefficient (k1) was obtained from topsoil than subsoil, likely due to greater microbial activity in the topsoil. However, for all soils, sorption of carbaryl on soils considerably increased the magnitude of the degradation half‐life (t1/2) for carbaryl in either single‐pesticide or multiple‐pesticide systems. In soils that contained <10 g kg−1 OC content, the effect of multiple‐pesticide systems was to enhance the mineralization of carbaryl. This was attributed to cometabolism. This study shows that carbaryl chemodynamic parameters (Koc and t1/2 values) can be used to adequately analyze the fate of carbaryl in the environment even when carbaryl exists in a mixture with atrazine and diuron.
River‐Groundwater Exchanges, Bank Filtration, and Groundwater Quality: Ammonium Behavior
Authors: Doussan C. , Ledoux E. , Detay M.
Published: July 2010

In many countries, bank‐filtrated water is an important component of the drinking water production. In this case, most of the water pumped from the alluvial aquifers originates from the adjacent river. Bank‐filtration is generally considered beneficial both quantitatively and qualitatively. However, in some cases bank filtration can cause deleterious effects to groundwater quality. This paper describes such a case, focusing on ammonium (NH4) concentrations. The data were gathered at an experimental bank‐filtration site which is part of a large well field along the Seine River (France). At this site, groundwater was sampled along a flow line path and pore water of river bed sediments was collected with peepers or by centrifuging core samples. The pore waters of the superficial river bed sediments have high ammonium concentrations (>30 mg NH4 L−1) whereas, in the groundwater, these concentrations are lower (≤20 mg NH4 L−1), with higher concentrations near the bank. The high NH4 concentration in the sediment is related to the heavy organic load in the river and the mineralization of this organic matter by benthic microflora. Among the different mechanisms that influence NH4 transport and retention in the porous medium, it emerges that sorption by the alluvial sediments (Kd = 1 − 10 × 10−3 m3 kg−1), or even the chalk (Kd = 48 × 10−3 m3 kg−1) seems to be effective in retaining NH4. This is illustrated by a model of NH4 transfer with retardation adapted to the conditions of the site. Precipitation of NH4 salts is probably not involved in regulating NH4 concentrafion at this site.
Phosphorus Flux between Sediment and Overlying Water in Lake Okeechobee, Florida: Spatial and Temporal Variations
Authors: Moore P. A. , Reddy K. R. , Fisher M. M.
Published: July 2010

Total P is increasing over time in the waters of Lake Okeechobee, Florida, but the concentrations do not correlate with external loads. The objectives of this study were to determine: (i) the P flux from various sediment types within the lake, (ii) the factors that control direction and magnitude of P flux, and (iii) the amount of P associated with various inorganic P phases within the sediment. Phosphorus flux was measured from intact sediment cores taken from eight sites that represent major sediment types and major inflows of Lake Okeechobee at four time periods in 1989–1990. At the same location‐times, dissolved reactive phosphorus (DRP) in porewater was determined using porewater equilibrators and/or sediment cores. Results indicate that P flux from sediments is very sensitive to changes in O2 status of the overlying water, with anaerobic conditions promoting large P fluxes. Despite steep porewater DRP gradients in sediments (varying from 0.1 mg P L−1 at the sediment/water interface to more than 1 mg P L−1 at lower depths), P flux was not regulated by such gradients. Such lack of dependence of P flux on DRP gradients highlights the role redox reactions (involving Fe) can play in P chemistry in the top few centimeters of the sediment. Internal P loads (i.e., flux from bottom sediments) were found to be approximately equivalent to external P loads (≈1 mg P m−2 d−1).