M. B. Kirkham

Remediation of heavy metal(loid)s contaminated soils - To mobilize or to immobilize?

Unlike organic contaminants, metal(loid)s do not undergo microbial or chemical degradation and persist for a long time after their introduction. Bioavailability of metal(loid)s plays a vital role in the remediation of contaminated soils. In this review, the remediation of heavy metal(loid) contaminated soils through manipulating their bioavailability using a range of soil amendments will be presented. Mobilizing amendments such as chelating and desorbing agents increase the bioavailability and mobility of metal(loid)s. Immobilizing amendments such of precipitating agents and sorbent materials decrease the bioavailabilty and mobility of metal(loid)s. Mobilizing agents can be used to enhance the removal of heavy metal(loid)s though plant uptake and soil washing. Immobilizing agents can be used to reduce the transfer to metal(loid)s to food chain via plant uptake and leaching to groundwater. One of the major limitations of mobilizing technique is susceptibility to leaching of the mobilized heavy metal(loid)s in the absence of active plant uptake. Similarly, in the case of the immobilization technique the long-term stability of the immobilized heavy metal(loid)s needs to be monitored.

Antioxidant responses to drought in sunflower and sorghum seedlings

To determine if antioxidant responses to drought differ between C3 and C4 plants, we grew Sorghum bicolor (C4 ) and Helianthus annuus (C3 ) under either watered or dry conditions in a growth chamber. Levels of leaf enzymatic antioxidants (ascorbate peroxidase, catalase, guaiacol peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase and superoxide dismutase), nonenzymatic antioxidants (ascorbate, glutathione and carotenoids) and stress parameters (Chl and malondialdehyde [MDA]) were determined. Under watered and drought conditions, Chl contents and leaf relative water contents (RWC) were higher in sorghum than in sunflower; however, MDA levels were higher in sunflower than in sorghum. Under watered conditions, inherent levels of antioxidants were not consistently higher or lower in sorghum than in sunflower. In response to drought, levels of antioxidants, Chl and MDA showed increase, decrease or remained unchanged depending on crop, duration of drought and kind of antioxidants. Duration of drought was divided arbitrarily into three stages. At an early stage of drought (watering had stopped for 3-4 d) when soil water content (WC) and leaf RWC had decreased only in sunflower, drought generally did not affect levels of antioxidants and stress parameters. At a middle stage of drought (watering had stopped for 5-6 d) when soil WC had decreased for both sorghum and sunflower but leaf WC and RWC had decreased only in sunflower, drought changed levels of some antioxidants in sunflower and sorghum. At a late stage of drought (watering had stopped for 7-8 d) when soil WC, leaf WC and RWC had decreased in sorghum and sunflower, most parameters studied were affected by drought. Because of the differential effect of drought, levels of antioxidants were not consistently higher or lower in sorghum than in sunflower under drought. These results show that, under both drought and watered conditions, sorghum does not have consistently higher or lower antioxidant levels than sunflower, and that antioxidant responses to drought differ in C3 and C4 plants.

EDTA-assisted heavy-metal uptake by poplar and sunflower grown at a long-term sewage-sludge farm

Little information is available concerning the efficacy of chelates applied to biosolids (sewage-sludge)-treated soil for heavy-metal removal. The purpose of the experiment was to determine the availability to sunflower (Helianthus annuus L.) and hybrid poplar (Populus deltoides Marsh. × P. nigra L.) seedlings, of non-essential (Cd, Ni, Pb) and essential heavy metals (Cu, Fe, Mn, Zn) in field soil injected with biosolids since 1976 and treated with ethylenediamine-tetraacetic acid (EDTA) in 2001. Sunflower was grown at two densities, 20 000 and 60 000 plants/ha, and poplar at 10 000 plants/ha. The tetrasodium salt of EDTA was applied at rates of 0, 0.5, 1, and 2 g EDTA salt per kg surface (25-cm depth) soil. The EDTA did not affect uptake by poplar of the three non-essential (Cd, Ni, Pb) and four essential (Cu, Fe, Mn, Zn) heavy metals. For sunflower, the 1.0 g/kg rate of chelate addition resulted in maximal removal of the three non-essential heavy metals (Cd, Ni, Pb). Uptake of the essential heavy metals by sunflower was little affected by the EDTA. At the 20 000 plants/ha density, leaves of sunflower grown with 1.0 g EDTA Na4ċ2H2O per kg soil accumulated more Cd, Ni, and Pb than leaves of sunflower grown without the EDTA salt. At this density, concentrations of Cd in leaves of sunflower without EDTA and with 1.0 g/kg EDTA salt were 2.2 and 6.5 μg/g, respectively; for Ni, they were 6.7 and 19.2 μg/g, respectively; and for Pb, they were 15.6 and 46.9 μg/g, respectively. At the 60 000 plants/ha density, stems of sunflower grown with 1.0 g EDTA Na4ċ2H2O per kg soil accumulated more Cd, Ni, and Pb than stems of sunflower grown without the EDTA salt. At this density, concentrations of Cd in stems of sunflower without EDTA and with 1.0 g/kg EDTA salt were 0.6 and 4.6 μg/g, respectively; for Ni, they were 1.7 and 17.6 μg/g, respectively; and for Pb, they were 5.2 and 42.8 μg/g, respectively. Removal of the non-essential heavy metals by sunflower was greater at the higher plant density (60 000 plants/ha) compared to the lower one (20 000 plants/ha).

Lipid peroxidation in sorghum and sunflower seedlings as affected by ascorbic acid, benzoic acid, and propyl gallate

Summary Lipid peroxidation in sorghum and sunflower seedlings as affected by free-radical scavengers ascorbic acid, benzoic acid, and n-propyl gallate was studied. Roots of 17-day-old plants were immersed for 24 h in nutrient solution or nutrient solution containing either polyethylene glycol (PEG) or the scavengers. Compared with the nutrient solution treatment, PEG increased lipid peroxidation in sunflower, but had no effect in sorghum. Compared with the PEG-treated plants, ascorbic acid inhibited lipid peroxidation in both sunflower and sorghum, and benzoic acid had no effect, whereas n-propyl gallate inhibited lipid peroxidation in sorghum, but did not affect it in sunflower. However, levels of superoxide and hydrogen peroxide and activities of superoxide dismutase (SOD), ascorbate peroxidase (AP) and catalase (CAT) in the two species were not affected by the free-radical scavengers when compared with the PEG treatment. The PEG and the free-radical scavengers increased the ratios of SOD to CAT or AP in sunflower, but did not affect them in sorghum. These results suggest that sorghum is more resistant to oxidative stress than sunflower, and drought injury.induced by lipid peroxidation might be lessened by exogenous application of proper free-radical scavengers.

Trace elements in soil: bioavailability, flux, and transfer.

Bioavailability of Trace Elements Bioavailability and Fate of Trace Elements in Long-Term Residual-Amended Soil Studies, G.F. Vance and G.M. Pierzynski An Experimental and Theoretical Study on Equilibrium Partitioning of Heavy Metals, E. Podlesakova, J. Nemecek, and R. Vacha Sequential Extraction of Metals from Artificially Contaminated Soils in the Presence of Various Composts, L. Madrid, E. Diaz-Barrientos, and I. Cardo Induced Hyperaccumulation: Metal Movement and Problems, C. Anderson, A. Deram, D. Petit, R. Brooks, R. Stewart, and R. Simcock Bioavailability of Cu, Zn, and Mn in Contaminated Soils and Speciation in Soil Solution, S.M. Reichman, N.W. Menzies, and D.L. Rimmer Fluxes, Transfer Partitioning of Trace Elements Heavy Metals in Dutch Soils: An Experimental and Theorectical Study on Equilibrium Partitioning, W.J.G.M. Peijnenburg, A.C. de Groot, and R.P.M. van Veen Isotopic Exchange Kinetics Method for Assessing Cadmium Availability in Soils, E. Gerard, G. Echevarria, T. Streckeman, and J.L. Morel Accumulation, Redistribution, Transport, and Bioavailability of Heavy Metals in Waste-Amended Soils, H.F. Xiang, W.L. Knigery, and H.M. Selim Contaminant Transport in the Root Zone, I. Vogeler, S.R. Green, B.E. Clothier, M.B. Kirkham, and B.H. Robinson Partitioning and Reaction Kinetics of Cd-109 and Zn-65 in an Alum Shale Soil as Influenced by Organic Matter at Different Temperatures, A. Almas. B.R. Singh, and B. Salbu Solid Phase Speciation of Cd, Ni, and Zn in Some Contaminated and Non-Contaminated Tropical Soils, A. Kashem and B.R. Singh Quality of Estimated Freundlich Parameters pf Cd Sorption from Pedotransfer Functions to Predict Cadmium Concentration of Soil Solution, G. Springob, D. Tetzlaff, A. Schon, and J. Bottcher Effect of Sorbed and Dissolved Organic Carbon on Molybdenum Retention by Iron Oxides, F. Lang and M. Kaupenjohann Speciation and Sorption of Lead (II) in Soils, A. Ponizovsky and E. Mironenko

Use of second derivatives of canopy reflectance for monitoring prairie vegetation over different soil backgrounds

Abstract Spectral derivative indices were compared with the commonly used near-infrared to red reflectance ratio ( NIR red ) and the normalized difference (ND) spectral indices. Two “windows” of second derivatives, ρ″0.69μm and ρ″0.74 μm, exist in the visible and NIR spectral regions, which can be used to estimate vegetation characteristics such as percent cover and leaf area index (LAI). Second derivatives centered on the red and NIR wavebands (MSS Bands 3 and 4) were calculated using broadband radiometer data for grassland sites which had been previously burned or had been left unburned for several years. The second derivative indices minimized the effect of the soil background differences caused by the prior burning treatments, and clearly showed the advantages of the derivative technique over the conventional NIR red ratio and ND spectral indices.

Effect of carbon dioxide on sorghum yield, root growth, and water use

Abstract The concentration of atmospheric carbon dioxide (CO 2 ) is rising. The effect of higher than ambient levels of CO 2 on plants grown in the sub-humid central Great Plains of the U.S.A. has not been investigated. Therefore, an experiment was conducted at Manhattan, Kansas, to study the effect of elevated levels of CO 2 on grain sorghum [ Sorghum bicolor (L.) Moench]. During the summer of 1984, the sorghum was grown in rhizotrons in which root and shoot growth could be monitored throughout the growth cycle. The tops of the plants were enclosed in plastic chambers, which contained one of four concentrations of CO 2 : 330 (ambient), 485, 660, and 795 μl 1 −1 . Enriched CO 2 delayed the boot, half bloom, and soft dough stages. Sorghum grown at elevated concentrations of CO 2 yielded more roots and shoots than plants grown with 330 μl 1 −1 . At all soil-profile depths, root numbers and weights were higher at elevated CO 2 than at ambient CO 2 . However, water use per unit dry matter of leaf, stem, root, and grain was decreased 13, 30, 31, and 29%, respectively, in plants grown at 795 μl 1 −1 CO 2 compared to plants at 330 μl 1 −1 CO 2 . Although elevated CO 2 levels increased the stomatal resistance and leaf temperature, an increase in leaf area indices resulted in a lower canopy resistance.

Auxin-Enhanced Root Growth for Phytoremediation of Sewage-Sludge Amended Soil

A technology to increase root growth would be advantageous for phytoremediation of trace metal polluted soil, because more roots would be available for metal uptake. The objective of this study was to determine if the auxin, indole-3-acetic acid (IAA), would increase root growth in soil with metals from sewage sludge, when the tetrasodium salt of the chelate EDTA (ethylenediamine-tetraacetic acid) was added to solubilize the metals. Sunflower (Helianthus annuus L.) plants grew in large pots containing either soil from a sludge farm or composted sludge. The EDTA salt was added at a rate of 1 g kg−1 soil 37 days after planting. IAA at the rate of 3 or 6 mg l−1 was sprayed on the leaves (500 ml) and added to the soil (500 ml) three times: 41, 50, and 74 days after planting. At harvest 98 days after planting, oven-dry weights were measured, and plant organs were analyzed for Cd, Cu, Fe, Mn, Ni, Pb, and Zn. Metal uptake was determined as the product of metal concentration in an organ and weight. IAA increased root growth of plants grown in the soil with sludge when no EDTA was present. With no EDTA, Mn and Ni in leaves of plants grown in the soil were higher at 3 and 6 mg l−1 IAA compared to 0 mg l−1 IAA. With and without EDTA, Cd and Pb in leaves of plants grown in the compost were higher with 3 and 6 mg l−1 IAA compared to 0 mg l−1 IAA.

Elevated carbon dioxide : impacts on soil and plant water relations

Elevated Atmospheric Carbon Dioxide: Drought Introduction Predictions Photosynthesis of C3 and C4 Plants Photosynthesis of CAM Plants Field Studies with Crops Controlled Environment Studies with Crops Trees Gymnosperm versus Angiosperm Trees CAM Plant Salinity Elevated Carbon Dioxide in the Soil: Composition of the Soil Atmosphere Introduction Composition of the Soil Atmosphere Organic Matter Rainfall, Irrigation, and Flooding Elevated Carbon Dioxide in the Soil: Interaction with the Soil Physical Factors That Affect Root Growth Introduction Soil Water Soil Compaction Soil Temperature Elevated Carbon Dioxide in the Soil: Variable Oxygen Concentration and Root Growth Introduction Variable Oxygen Concentration in the Soil Variation in Species Soil versus Root Evolution of CO2 Limiting Concentration of Oxygen Maximum CO2 in Soil That Allows Crop Growth Movement of Gases Up and Down a Plant Elevated Carbon Dioxide in the Atmosphere: Interaction with the Soil Physical Factors That Affect Root Growth Introduction Soil Water Soil Compaction Soil Temperature Elevated Atmospheric Carbon Dioxide: Root Growth Introduction Field Studies with Sorghum and Wheat Controlled-Environment Studies with Wheat Soybeans, Tepary Bean, Bush Bean, Barley, and Cotton Horticultural Crops Pasture Plants Native Grasses Carbon Isotope Ratios of Plants with Different Photosynthetic Pathways Trees C3 and C4 Crops Compared CAM Plants Root-to-Shoot Ratios Root Restriction Elevated Atmospheric Carbon Dioxide: Plant Water Potential, Osmotic Potential, and Turgor Potential Introduction Wheat Grassland Plants Soybeans Peas Trees Stress Relaxation Native Herbs Elevated Atmospheric Carbon Dioxide: Stomatal Conductance Introduction Leaf Resistances Units Factors That Control Stomatal Movements Stomatal Conductance and Elevated CO2 C3 and C4 Plants Compared Elevated Atmospheric Carbon Dioxide: Stomatal Density Introduction Woodwards 1987 Discovery: Stomatal Density Decreases with Increasing CO2 Concentration Importance of Herbariums to Study the Historical Record of Stomata Confirmation of the 1987 Discovery Contradictions to the 1987 Discovery: No Effect of Elevated CO2 on Stomatal Density Brown and Escombes Diameter Law Amphistomatous and Hypostomatous Leaves Sensitivity of Stomata to CO2 Studies since Woodwards 1987 Discovery Studies of Fossil Plants Stomatal Anatomy and Elevated CO2 How Does Stomatal Density Change with CO2 Concentration? Elevated Atmospheric Carbon Dioxide: Transpiration and Evapotranspiration Introduction Transpiration under Greenhouse Conditions Carbon Dioxide Enrichment in Greenhouses Ethylene Transpiration under Elevated CO2 Evapotranspiration-General Principles Evapotranspiration under Elevated CO2 Elevated Atmospheric Carbon Dioxide: Water Use Efficiency Introduction Definitions and Historical Aspects of Efficient Water Use Water Requirement of C3 and C4 Plants Water Use Efficiency under Elevated CO2 Water Use Efficiency of Fossil and Herbarium Plants Elevated Atmospheric Carbon Dioxide: C3 and C4 Plants Introduction C3 versus C4 Photosynthesis Advantage of C4 Photosynthesis Dry Matter Production of C3 and C4 Plants Evolution of C4 Plants C3 and C4 Plants under Elevated CO2 Elevated Atmospheric Carbon Dioxide: Plant Anatomy Introduction Leaves Comparison of C3 and C4 Leaves Leaf Ultrastructure Wood Anatomy and Density under Variable CO2 Concentrations Wood Anatomy under Variable Precipitation and Ambient CO2 Internal Leaf Characteristics of C3 and C4 Plants under Ambient CO2 Elevated Atmospheric Carbon Dioxide: Phenology Introduction Phenology Wheat Physiology and Phenology Methods to Determine Crop Development Q10, Degree-Day Concept and Heat Units Growth Stages of Wheat as Affected by Elevated CO2 Phenology under Elevated CO2 Questions to Be Answered about Elevated CO2 and Phenology Elevated Atmospheric Carbon Dioxide: Growth and Yield Introduction Wheat Rice Barley Oats Soybean Cotton Horticultural Crops Pasture and Grassland Plants Marsh Plants Herbs and Weeds CAM Plants Deciduous Trees Evergreen Trees and Shrubs Temperature Free-Air CO2 Exchange Studies Harvest Index Quality Yield Epilogue References Index A Summary appears at the end of each chapter.

Agricultural Use of Phosphorus in Sewage Sludge

Publisher Summary This chapter discusses the impact of sludges on agricultural land. Three types of sludges are considered—namely, organic sludge, chemical sludge, and combined sludge. If crops are removed from the land, the supply of phosphorus in the soil becomes the limiting factor in crop production. Large quantities of phosphorus compounds are used as fertilizers and an extensive phosphate deposit in a country represents a great natural resource. Sewage sludge is the by-product of wastewater treatment processes. Handling and disposal of sludge are the most costly phases of sewage treatment. The traditional means of sludge handling and disposal are ocean disposal through barging or pipeline transport, dewatering and drying with disposal in a landfill, incineration, and lagooning. Sludge has been spread on agricultural land for disposal, fertilizing, and soil conditioning purposes for decades. Phosphorus, in the form of phosphate, is one of the major uncontrolled pollutants in wastewater. High phosphorus removal is achieved from wastewater chemically or biologically. Addition of phosphate-precipitating chemicals, such as lime, aluminum sulfate, sodium aluminate, or ferric chloride, during sewage treatment minimizes effluent phosphate concentrations. Chemical sludges and combined sludges vary in phosphorus concentrations, depending upon the characteristics of the wastewater, the type of chemical, the quantity of the chemical, and the place of addition of the chemical during the wastewater treatment process.