Journal of Environmental Quality 31:369-374 (2002)
© 2002 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
EXECUTIVE SUMMARIES
This Issue in Journal of Environmental Quality
 |
Timing is Everything!
|
|---|
For studies of soil organic P by 31P-NMR spectroscopy, quantitation of P species will not be accurate if peaks suffer from signal saturation. Therefore, delay times between scans must be long enough for all P species to fully relax back to equilibrium. Cade-Menun et al. measured the relaxation times of P species in three common soil extractants for P–NMR: NaOH, NaOH–EDTA, and NaOH–Chelex. They showed relaxation times for P species will vary by extractant, and can be correlated to the concentration of paramagnetic ions (e.g., Fe and Mn) in solution. Extracts with low paramagnetic ion concentrations require longer delay times between scans to avoid signal saturation.
B. Cade-Menun
(bjcm{at}pangea.stanford.edu)
Soil and Litter Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy: Extractants, Metals, and Phosphorus Relaxation Times. J. Environ. Qual. 31:457–465.
|
Permeability and Pore Size Distribution of Porous Media
|
|---|
Porosity and permeability of porous and fractured geological media decrease during exploitation of formation fluids such as petroleum, natural gas, or ground water due to the decrease in fluid pressure. This may result in ground subsidence and damage to petroleum, natural gas, or ground water wells. Therefore, an evaluation of the behavior of permeability and porosity under formation fluid pressure changes is important to petroleum and ground water industries. This study establishes a method that allows simultaneous measurement of permeability, porosity, and pore size distribution of cores. While permeability is determined in a classical Darcy setup, pore size distribution is obtained by low-field standard NMR relaxation time spectrometry, and porosity is determined with standard NMRI. The experiments allow derivation of the mechanisms responsible for pressure-dependent porosity and permeability changes.
W. Kinzelbach
(kinzelbach{at}ihw.baug.ethz.ch)
Variations of Permeability and Pore Size Distribution of Porous Media with Pressure. J. Environ. Qual. 31:
500–505.
|
Submergence Decreases Humification in Lowland Rice
|
|---|
To determine the effects of intensive cropping of tropical lowland rice and the associated soil submergence on chemical properties of soil organic matter, we used solid-state 13C and 15N and solution 31P nuclear magnetic resonance spectroscopy to analyze the labile mobile humic acid and the more recalcitrant Ca humate fractions extracted from a series of soils supporting several long-term field experiments in the Philippines. All analyses associated an increasing intensity of rice cropping with larger proportions of less humified material in both fractions, such as diester P, amide N, and phenolic C. We established significant correlations between proportions of various spectral areas as well as between some spectral areas and other humic acid properties such as visible light absorption and free radical concentration (positive indices of humification) and H concentration (negative index of humification).
N. Mahieu (n.mahieu{at}qmul.ac.uk)
Multinuclear Magnetic Resonance Analysis of Two Humic Acid Fractions from Lowland Rice Soils. J. Environ. Qual. 31:
421–430.
|
Soil–Water Studied by Stray-Field NMR
|
|---|
Soil samples consist of solid, liquid, and gaseous phases. A device to study undisturbed samples in which the matric potential of water can be varied will aid interpretation of water retention curves. Kinchesh et al. describe the construction and characterization of a unique device to study 5-cm-diameter soil cores by NMR in the strong stray field gradient of a superconducting magnet. Measurements of relative pore-size distribution in a 100-micron-thick slice are demonstrated and the effect of varying the matric potential on the filled pore distribution are presented. Some large-diameter pores remain filled even when the soil is partially drained, which confirms the hypothesis that the parallel-sided capillary tube model is insufficient to describe a soil containing pores interconnected by narrow necks.
A.R. Preston
(a.r.preston{at}qmul.ac.uk)
Stray Field Nuclear Magnetic Resonance of Soil Water: Development of a New, Large Probe and Preliminary Results. J. Environ. Qual. 31:
494–499.
|
Paramagnetic Effects on Carbon-13 NMR Spectra
|
|---|
Paramagnetic species—such as Fe oxides and Fe, Cu, and Mn cations—have long been known to cause problems in obtaining 13C NMR spectra of soil organic matter. Smernik and Oades now quantify this interference in terms of decreases in 13C NMR observability for model systems and isolated soil organic matter, doped with a range of paramagnetic species. Signal loss is shown to depend on the nature of the species and intimacy of mixing, as well as the concentration of the paramagnetic species. Three mechanisms for signal loss are identified for CPMAS spectra. Signal loss and increases in relaxation rates caused by paramagnetic doping are put to good use in identifying the nature of cation exchange sites on soil organic matter and in probing its submicron structure.
R. Smernik
(ronald.smernik{at}adelaide.edu.au)
Paramagnetic Effects on Solid State Carbon-13 Nuclear Magnetic Resonance Spectra of Soil Organic Matter. J. Environ. Qual. 31:
414–420.
|
Improvements in the 2-D NMR of Humic Substances
|
|---|
Nuclear magnetic resonance spectroscopy has long been a tool in organic chemistry and biochemistry. Recently, this powerful technique has been used successfully to study humic substances from soils and sediments. Two-dimensional NMR experiments can provide much more detail than that obtained from 1-D; however, the multitude of experiments available can make its application complicated. This paper presents data that demonstrate some 2-D experiments are better suited for humic substances than others. This information will assist the future application of 2-D NMR to humic substances.
A.J. Simpson
(asimpson{at}chemistry.ohio-state.edu)
Improvements in the Two-Dimensional Nuclear Magnetic Resonance Spectroscopy of Humic Substances. J. Environ. Qual. 31:
388–392.
|
NMR Imaging in Porous Media
|
|---|
Nuclear magnetic resonance imaging (NMRI) methods can be used in various ways for visualization of fluid flow and transport in porous media. The review shows examples for the application of two different principles: direct velocity imaging and the imaging of NMR tracer front movement in single phase, multiphase, and density flows. They illustrate the capacity of NMRI to give structural information both of the medium and the fluid distributions, as well as their temporal development. The resulting data can be used in a black box–white box comparison and as benchmarks for numerical models.
W. Kinzelbach
(kinzelbach{at}ihw.baug.ethz.ch)
Nuclear Magnetic Resonance Imaging for Studies of Flow and Transport in Porous Media. J. Environ. Qual. 31:
477–486.
|
Bioremediation of TNT-Contaminated Sites
|
|---|
Organic pollutants are degraded in the soil and simultaneously nonextractable residues are formed. Through their binding to soil, the transformed pollutants are no longer accessible to the biota; consequently, this process results in the bioremediation of contaminated sites. We investigated the transformation and binding of the explosive TNT (2,4,6-trinitrotoluene) using catechol, a humic monomer, or soil humic acid as cosubstrates. TNT was first reduced by anaerobic microorganisms and, after treatment with the fungal enzyme laccase, the resulting metabolites bound to humic material in the soil. This observation was confirmed using 15N–NMR spectra of 15N-labeled TNT and its ensuing metabolites.
Jean-Marc Bollag
(jmbollag{at}psu.edu)
Enzymatic Transformation and Binding of Labeled 2,4,6-Trinitrotoluene to Humic Substances during an Anaerobic/Aerobic Incubation. J. Environ. Qual. 31:
437–444.
|
Condensed Tannins Linked to Nutrient Cycling?
|
|---|
The fate of plant-derived condensed tannins in soils and their influence on nutrient cycling are hardly known. Lorenz and Preston show high-tannin fractions are extractable from a black spruce humus from a site in Northern Ontario, even if humus tannin levels are very low. Characterization of the extracts by 13C CPMAS NMR shows no evidence of tannin–protein complexes proposed as a mechanism for nitrogen sequestration. Further studies are needed to detect or isolate tannin–protein structures in humus and if condensed tannins contribute to forest management problems observed in black spruce ecosystems.
K. Lorenz
(lorenzk{at}uni-hohenheim.de)
Characterization of High-Tannin Fractions from Humus by Carbon-13 Cross- Polarization and Magic-Angle Spinning Nuclear Magnetic Resonance. J. Environ. Qual. 31:
431–436.
|
MRI of Fluid Flow in Porous Media
|
|---|
The movement of water in porous media, which makes up most of the shallow aquifers, is of prior importance for, e.g., an assessment of the risk of contamination of drinking water wells. Conventional laboratory techniques do not allow measurement of the flow velocity or the diffusion of water directly, thus leaving some uncertainty. This study demonstrates a method to measure these important parameters directly within the soil or sediment, while preserving the integrity of the sample. With magnetic resonance imaging (MRI), the propagation water in a sample can be visualized directly without adding any tracer chemicals. It is also possible to increase the spatial and temporal resolution of the experiment significantly. A better understanding of the processes involved in contaminant transport gained from MRI experiments contributes to an improvement in the prediction of the fate of contaminants in ground water.
T. Baumann
(thomas.baumann{at}ch.tum.de)
Flow and Diffusion Measurements in Natural Porous Media Using Magnetic Resonance Imaging. J. Environ. Qual. 31:
470–476.
|
Inositol Phosphate Measurement Simplified
|
|---|
Inositol phosphates are among the most important forms of P in nature, but are poorly understood because they are difficult to measure. We developed a method for measuring inositol hexakisphosphate, the most abundant type of inositol phosphate, in soil and water samples. The method involves the simultaneous separation and concentration of the compound onto a gel and detection by 31P nuclear magnetic resonance spectroscopy. With development, this method should help to reveal important information about these enigmatic P compounds.
B. Turner
(bturner{at}nwisrl.ars.usda.gov)
A Novel Technique for the Pre-Concentration and Extraction of Inositol Hexakisphosphate from Soil Extracts with Determination by Phosphorus-31 Nuclear Magnetic Resonance. J. Environ. Qual. 31:
466–470.
|
Mobile Phosphorus Determination Using Solid-State NMR
|
|---|
The solubility, form, and risk of P loss changes with soil P concentration. McDowell et al. used solid-state 31P NMR spectroscopy, high-power decoupling magic angle spinning NMR, and cross polarization NMR to determine potentially mobile P associated with Al and Ca in arable soils with Olsen P concentrations of 40 to 102 mg P kg-1. Above a threshold of 59 mg Olsen P kg-1, the potential for P loss increases. Comparison among soils indicated P above the threshold was present as a combination of soluble and loosely adsorbed (protonated–cross-polarized) P forms, largely associated with Ca as Monetite (CaHPO4) and dicalcium phosphate dihydrate (CaHPO4·2H2O), and some Al associated P as Wavellite. These findings demonstrate solid-state NMR can provide good information on the chemical nature and risk of soil P species to water enrichment.
R. McDowell
(richard.mcdowell{at}agresearch.co.nz)
Analysis of Potentially Mobile Phosphorus in Arable Soils Using Solid State Nuclear Magnetic Resonance. J. Environ. Qual. 31:
450–456.
|
Design Determines Detention Pond Performance
|
|---|
Wet detention ponds are a common mitigation tool used to reduce inputs of nonpoint-source pollutants into natural water bodies. However, their efficacy at pollution reduction varies greatly among ponds. Mallin et al. conducted a 29-month study comparing inflow and outflow parameter concentrations of three regional wet detention ponds. The results demonstrated removal of nutrients, turbidity, and fecal coliform bacteria was high in ponds that combined large and diverse coverage of aquatic macrophytes with a high pond length/width ratio. Combining wet detention ponds with natural wetlands also aided in nutrient removal, whereas placing pond inputs near the outflow structure greatly reduced nutrient removal efficacy.
M.A. Mallin (mallinm{at}uncwil.edu)
Pollutant Removal Efficacy of Three Wet Detention Ponds. J. Environ. Qual. 31:
654–660.
|
Heteroaromatic-N After Prolonged Humification
|
|---|
Subjecting organic material from recent and fossilized sediments to solid-state 15N NMR spectroscopy, the transformation of organic N from plant debris was examined during peatification and coalification. While for recent material no indication of heteroaromatic N accumulation was found, spectra of the fossilized sample material was dominated by pyrrole-type N. As revealed from the deepest peat layer of a Holocene sapropel from Mangrove Lake, Bermuda, the transformation occurs between an advanced stage of peatification and an early stage of coalification, most probably due to abiotic processes.
H. Knicker
(knicker{at}weihenstephan.de)
Formation of Heteroaromatic Nitrogen after Prolonged Humification of Vascular Plant Remains as Revealed by Nuclear Magnetic Resonance Spectroscopy. J. Environ. Qual. 31:
444–449.
|
Transport Imaging in Porous Media
|
|---|
The detailed characterization of transport processes in porous media is of crucial importance to understand the fate of contaminants in soils. With development of the nuclear magnetic resonance imaging technique in recent years, a powerful instrument is available for detailed, high resolution, 3-D imaging of tracer concentrations in porous media. With this method, we have investigated the movement of Ni2+ in columns packed with glass beads and quartz sand. From the obtained 3-D movie, we have calculated the 3-D flow velocity field as well as the statistical properties, which serve either as the basis for novel 3-D computer models, or for their validation. Also, we have calculated the mean effective dispersion coefficient, which is established only after a minimum flow distance, depending on grain size.
K.-H. Herrmann
(k.-h.herrmann{at}fz-juelich.de)
Three-Dimensional Nickel Ion Transport through Porous Media Using Magnetic Resonance Imaging. J. Environ. Qual. 31:
506–514.
|
Do Harvesting and Climate Affect Forest Soil Organic Matter?
|
|---|
Harvesting of old-growth coastal forest in British Columbia has raised concerns about sustainability and preservation of its unique characteristics. We characterized C pools in recently harvested to old-growth stands on the west coast of Vancouver Island and the drier, slightly warmer east coast. Neither climate nor harvesting affected C concentration of five poorly decomposed organic matter pools. Carbon quality (carbon-13 NMR) also showed little harvesting effect, but small-scale variation, mainly due to coarse woody debris (a defining feature of old-growth) vs. tannin-rich roots. Wood had a greater influence in the west, and charcoal in the drier east side. The large old-growth legacy has minimized the impact of one harvest on organic matter, but more intensive management will likely reduce wood and charcoal inputs and microsite variability, with potential impact on biodiversity.
C.M. Preston
(cpreston{at}pfc.forestry.ca)
Harvesting and Climate Effects on Organic Matter Characteristics in British Columbia Coastal Forests. J. Environ. Qual. 31:
402–413.
|
High-Resolution Measurement of Trace Gases
|
|---|
A new technique is presented for the rapid, high-resolution identification and quantification of multiple trace gases above soils, at concentrations down to 10 ppb. The technique, selected ion flow tube mass spectrometry (SIFT-MS), uses selected chemical ionization methods to identify and quantify trace gases. The method is demonstrated by measuring emissions of NO, NH3, and organics from soils treated with synthetic cattle urine, and shows that of the applied N, 7% is emitted as NH3–N, 10% as NO–N, and none as N organics. The SIFT method allows simultaneous in situ measurement of multiple gas components with high spatial resolution of <10 cm and time resolution of <20 seconds, allowing the identification of emission hot-spots, measuring localized and rapid variations above agricultural and contaminated soils, and integrated emissions over longer periods.
M.N. Mautner
(mautnerm{at}lincoln.ac.nz)
Real-Time, High-Resolution Quantitative Measurement of Multiple Soil Gas Emissions: Selected Ion Flow Tube Mass Spectrometry. J. Environ. Qual. 31:
515–524.
|
Industrial Impact on Marsh Soils
|
|---|
The Bahia Blanca Estuary in Argentina is linked to a petrochemical industrial complex whose raw materials and final products contaminate the surrounding areas. To establish the effects of the industrial waste disposal on nearby coastal soils, 17 samples were taken at different distances from the loading dock and the outfall pipes of the industrial complex. The contaminant effluents caused changes in the physicochemical properties of soils near the dumping point, though with important spatial variations due to heterogeneity of their distribution, their apportionment in aqueous suspension, and tidal oscillations. Hydrocarbons, zinc, copper, and lead were found at levels that modified the physical and chemical characteristics of the soils. The continuity of the porous space of the soil matrix is impeded by the presence of pollutants, which generate areas highly limiting to water flow.
M.L. Andrade (mandrade{at}uvigo.es)
Industrial Impact on Marsh Soils at the Bahia Blanca Ria, Argentina. J. Environ. Qual. 31:
532–538.
|
Management Techniques to Reduce Ground Water Nitrate Contamination
|
|---|
Nitrate contamination of ground water in proximity to citrus growing regions of central Florida is an environmental concern. Understanding water and nutrient transport through the soil profile is important for efficient irrigation and nutrient management to minimize excess nutrient leaching below the root zone. Intensive soil sampling following fertilizer and tracer application was adapted to critically evaluate water and nutrient transport through a sandy soil profile. The results suggest that efficient irrigation management, aimed to replenish the water deficit within rooting depth, along with increased application frequency of fertilizers in small quantities, improve nutrient uptake efficiency while minimizing leaching loses. The bromide tracer and numerical modeling approach further validated these findings.
S. Paramasivam (siva{at}savstate.edu)
Fate of Nitrate and Bromide in an Unsaturated Zone of a Sandy Soil under Citrus Production. J. Environ. Qual. 31:
671–681.
|
Lead Bioavailability and Metal Phytoavailability
|
|---|
This study was carried out to evaluate the effects of plant growth on soil Pb bioavailability to humans after addition of P and/or Mn oxide, and the effects of P and/or Mn oxide on Pb, Cd, and Zn phytoavailability in three metal-contaminated soils. Results indicate the addition of P and/or Mn oxide reduced bio-available Pb based on physiologically based extraction test (PBET) compared to the control, even after extensive cropping. The PBET data also suggest removal of P from soluble P sources by plants could negate the beneficial effects of P on bioavailable Pb, unless sufficient soluble P was added or soluble P was combined with Mn oxide. Moreover, shoot tissue concentrations of all three metals of interest were reduced by the addition of soluble P.
G.M. Hettiarachchi
(hettiarachchi.ganga{at}epa.gov)
In Situ Stablization of Soil Lead Using Phosphorus and Manganese Oxide: Influence of Plant Growth. J. Environ. Qual. 31:
464–572.
|
River Phosphorus Concentrations Linked to Soil Types
|
|---|
Diffuse P inputs to Irish surface waters are increasingly linked to agricultural activities and a reliable catchment management tool is vital. Combining water quality data with catchment characteristics has produced models that predict river P concentrations in catchments so areas at risk of diffuse P pollution can be delineated. The development of these models has identified soil type as a key catchment characteristic that drives nutrient losses from the landscape to surface waters. A statistical analysis of 35 river catchments and their characteristics indicated areas with predominantly wet soil coverage delivered more P to surface waters than those with mostly well-drained soils. Results highlight the importance of soil type, in terms of hydrology, when considering losses of nutrients from soil to water.
K. Daly
(kdaly{at}johnstown.teagasc.ie)
Modeling Phosphorus Concentrations in Irish Rivers Using Land Use, Soil Type, and Soil Phosphorus Data. J. Environ. Qual. 31:
590–599.
|
Environmentally Friendly Fate of New Herbicide
|
|---|
Mesotrione is a new triketone herbicide discovered after the screening of chemicals related to the "natural herbicide," leptospermone, secreted from the bottle bush plant. Mesotrione has the same mode of action as leptospermone with an improved potency and an unusual environmental fate due to the way its adsorption and degradation behavior are combined. As expected for a weak acid, mesotrione adsorption decreased as soil pH increased, but the half-lives also got shorter as soil pH increased. Thus, only "paired" values of adsorption and half-life are relevant for environmental fate assessments. Consequently, leaching potential did not vary with soil pH, since the large variations in adsorption with pH were counter-balanced by changes in half-life values.
J.S. Dyson
(jeremy.dyson{at}syngenta.com)
Adsorption and Degradation of the Weak Acid Mesotrione in Soil and Environmental Fate Implications. J. Environ. Qual. 31:
613–618.
|
N Fixation, CO2, and Climate Effects on Legume Growth
|
|---|
A dynamic ecophysiological model was developed for the legume soybean growing in northern China, which synthesized symbiotic N fixation and main physiological processes under variable CO2 and climatic conditions. Measurements in a CO2 enrichment experiment were used to parameterize and validate the model. The simulations showed increasing CO2, precipitation, and efficiency of N fixation have positive effects on biomass accumulation under semiarid conditions. Factors with positive effects on plant growth tended to promote each other in the simulation range, except the relationship between CO2 and climatic factors.
Q. Gao (gaoq{at}bnu.edu.cn)
Simulating Interactive Effects of Symbiotic Nitrogen Fixation, Carbon Dioxide Elevation, and Climatic Change on Legume Growth. J. Environ. Qual. 31:
634–641.
|
Necrosis Related to Tissue NaCl Concentration
|
|---|
Tailings materials produced by the oil sands mining industry are relatively alkaline and saline, containing Na, Cl, and SO4 at levels that may inhibit plant growth. Franklin et al. show that while shoot concentrations of nutritional elements are altered in jack pine seedlings treated with tailings water, injury and growth reduction over the first growing season are not the result of nutrient deficiency. Rather, needle necrosis was related to tissue levels of Na and Cl, indicating ion toxicity. Results are based on seedlings treated in sand culture, during a 10-week period, and suggest the use of jack pine in reclamation should be limited to sites containing low levels of Na and Cl.
J. Zwiazek
(janusz.zwiazek{at}ualberta.ca)
Jack Pine Growth and Elemental Composition Are Affected by Saline Tailings Water. J. Environ. Qual. 31:
648–653.
|
Shallow Soils Buffer Rain Qualities
|
|---|
Shallow, organic matter–rich, nutrient-poor soils are common for the areas of southern Norway that have received large amounts of acid precipitation. Strand et al. show an improvement in rain quality does not equally reduce the acidity of leachate from these shallow soils. The results suggest a reduction in sulfate in the rain has greatest effect on leachate quality, while reduced acidity, nitrate, and ammonium is not clearly reflected in the leachate. Seasonal variations and amount of precipitation are of great importance. These results are based on a 4-year lysimeter study using soil monoliths and rain of different qualities and quantities.
L.T. Strand (line.strand{at}ijvf.nlh.no)
Leaching from Organic Matter–Rich Soils by Rain of Different Qualities: I. Concentrations. J. Environ. Qual. 31:
547–556.
|
Polyacrylamide Removes Itself from Irrigation Runoff
|
|---|
A water soluble, nontoxic polymer, polyacrylamide (PAM) is added in very small quantities to irrigation water to reduce erosion in irrigation furrows. While PAM is used on hundreds of thousands of farmed acres in the USA, little is known of its fate in furrow streams and runoff, or how far it may be transported in downstream waters. Lentz et al. show PAM does not persist long in treated furrow streams or in wastewater ditches that convey field runoff from farms. When used according to established guidelines, the likelihood PAM will enter downstream natural surface waters appears small. Information garnered will help farmers minimize the PAM quantities used and amounts that escape targeted fields, yet still obtain maximum protection from erosion.
R.D. Lentz
(lentz{at}nwisrl.ars.usda.gov)
Fate and Efficacy of Polyacrylamide Applied in Furrow Irrigation: Full-Advance and Continuous Treatments. J. Environ. Qual. 31:
661–670.
|
Dissolution Kinetics of Heavy Metals in Dutch Sediments
|
|---|
Heavy metal and sulfide dissolution kinetics in sediment were studied at different concentrations of added acid and varying extraction times. Acid concentration appeared to be of more influence than extraction time. The acid volatile sulfide (AVS) content, as well as the ratio of simultaneously extracted metals (SEM, sum of Cd, Cu, Ni, Pb, and Zn) and AVS, decreased with increasing final pH. This observation is of great practical importance, since the SEM/AVS ratio is well known for use in environmental risk assessment studies of sediments.
S.E.J. Buykx (susan.buykx{at}rivm.nl)
Dissolution Kinetics of Heavy Metals in Dutch Carbonate- and Sulfide-Rich Freshwater Sediments. J. Environ. Qual. 31:
573–580.
|
Wildfire Intensifies Wind Erosion
|
|---|
Redistribution of soil, nutrients, and contaminants is often driven by wind erosion in semiarid shrublands, and is especially pronounced during episodic high-velocity winds. Vegetation cover, which moderates wind erosion, can be reduced rapidly and dramatically by wildfire but few studies have evaluated temporal and spatial components of wind erosion with respect to: (i) weekly erosion rates as a function of episodic high-velocity winds, (ii) wind erosion rates on burned and unburned sites, and (iii) within-site spatial heterogeneity in erosion. Measuring wind erosion in unburned and recently burned Chihuahuan desert shrubland, Whicker et al. highlight the importance of considering finer temporal and spatial dynamics finding: (i) weekly wind erosion was predicted more accurately by daily-peak rather than daily-average wind velocities; (ii) much greater erodibility in burned vs. unburned shrubland, as indicated by several erosion metrics; and (iii) burned shrubland lost soil from areas between, and especially from areas under, burned shrub canopies, whereas soil accumulated under shrubs in the unburned area.
J.J. Whicker (jjwhicker{at}lanl.gov)
Temporal and Spatial Variation of Episodic Wind Erosion in Unburned and Burned Semiarid Shrubland. J. Environ. Qual. 31:
599–612.
|
Heavy Metal Sorption in Tropical Soils
|
|---|
Contamination of the environment by heavy metals is a problem in many developing areas of the tropics. Unfortunately, research focusing on sorption reactions of heavy metals in tropical soils has received much less attention than studies conducted on temperate region soils. Sorption characteristics of Cd and Pb in several highly weathered soils from Puerto Rico were assessed at varying metal concentrations, pH values, and as a function of soil surface charge. All soils sorbed more Pb than Cd, and Pb sorption occurred via both electrostatic and chemisorption reactions while Cd was predominantly physisorbed. Thus, Pb was sorbed much more strongly than Cd in our tropical soils and likely poses less of a threat to underlying ground water systems due to its lower mobility and availability.
C. Appel (chip{at}gnv.ifas.ufl.edu)
Concentration, pH, and Surface Charge Effects on Cadmium and Lead Sorption in Three Tropical Soils. J. Environ. Qual. 31:
581–589.
|
Microcosm Wetlands for Wastewater Treatment
|
|---|
This study evaluated the feasibility of using constructed wetlands (CW), with less land requirement, by operating a group of microcosm wetlands at hydraulic retention times (HRTs) of <4 days in southern Taiwan. An artificial, simulated municipal wastewater containing 200 mg L-1 of chemical oxygen demand (COD), 20 mg L-1 of NH+4–N (AN), and 20 mg L-1 of PO3-4–P (OP) was the inflow source. Three emergent (reed, water primrose, and dayflower) and two floating (water spinach and water lettuce) plants were tested. The planted systems showed more nutrient removal than unplanted systems; however, the type of macrophytes in CW did not make a major difference in treatment. For AN and OP removal, the highest efficiencies occurred at an HRT of 3 days, whereas maximum removal rates of AN and OP occurred at an HRT of 2 days. The efficient removal of these constituents obtained with HRTs between 2 and 4 days, indicates the possibility of using a CW system for wastewater treatment with less land requirement.
Shuh-Ren Jing
(jingsr{at}mail.chna.edu.tw)
Microcosm Wetlands for Wastewater Treatment with Different Hydraulic Loading Rates and Macrophytes. J. Environ. Qual. 31:
690–696.
|
Light Intensity Interacts with Toxicity in Algal Tests
|
|---|
In algal tests with dyes, growth of algae can be inhibited in two ways: physically by light absorption and chemically by toxic action of the dye. Up to now, it was not clear whether there is an interaction between these two factors and how these factors work in combination. Cleuvers et al. show the sensitivity of Scenedesmus subspicatus against the model toxicant potassium dichromate is positively correlated to photon flux density during the algal growth inhibition test. Low photon flux densities lead to reduced effects and higher EC50 levels. Further, the combination effect of the chemical and physical effects can be properly calculated only by using the concept of independent action. Thus, if chemical and physical effects are measured in combination, as is the case in tests with dyes, current test protocol for the algal growth inhibition test may lead to wrong estimations of the toxic potential.
M. Cleuvers
(cleuvers{at}bio5.rwth-aachen.de)
Combination Effect of Light and Toxicity in Algal Tests. J. Environ. Qual. 31:
539–547.
|
Little Leaching of Biosolids Phosphorus
|
|---|
Understanding P leaching from biosolids is important for developing rational P-based nutrient management strategies. Elliott et al. report P leaching from sandy soils is much lower for most biosolids than for commercial fertilizer and chicken manure. Compared to manures and fertilizers, most biosolids are enriched in Al and Fe through wastewater and solids treatment processes. Poorly crystalline forms of Al and Fe have strong P-sorbing potential and thus biosolids P tends to be insoluble and nonleachable. A phosphorus saturation index, determined by a simple oxalate extraction of the pre-applied biosolids, is proposed as a practical indicator of bio-solids P leachability.
H.A. Elliott (hae1{at}psu.edu)
Phosphorus Leaching from Biosolids-Amended Sandy Soils. J. Environ. Qual. 31:
681–689.
|
Arsenic Hyperaccumulation by Brake Fern
|
|---|
The use of green plants to remove contaminants from soils is a cost-effective and environmentally sound approach. Brake fern is the first plant reported to hyperaccumulate arsenic, a carcinogenic element often used as an herbicide. Greenhouse studies by Tu and Ma show Brake fern has a staggering capacity to tolerate and soak up arsenic in soils. Thus, the fern may be an excellent candidate for cleaning up thousands of sites contaminated by arsenic from industrial, mining, agricultural, or other operations around the world.
Cong Tu (ctu2{at}unity.ncsu.edu)
Effects of Arsenic Concentrations and Forms on Arsenic Uptake by the Hyperaccumulator Ladder Brake. J. Environ. Qual. 31:
641–647.
TOP
Timing is Everything!
Permeability and Pore Size...