Civil and Environmental Engineering Commons^™

Selecting Sprinkler Packages For Center Pivots, Derrel L. Martin, William L. Kranz, Allen L. Thompson, Hong Liang

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Center pivots are the primary method of irrigation across the U.S. Great Plains. Center-pivot irrigation is also the fastest growing method of irrigation in the U.S. and around the world. Pivots have the potential to be very efficient and uniform if sprinkler devices are properly selected for local field conditions. New water application devices provide for selection that minimizes runoff and controls droplet sizes to reduce evaporation and drift losses. We present updates to models for computing runoff potential based on characteristics of sprinkler devices and soil textural classes. A dimensionless solution to the Green-Ampt infiltration method for center pivots …

Sensitivity Of Grass- And Alfalfa-Reference Evapotranspiration To Weather Station Sensor Accuracy, Dana O. Porter, Prasanna H. Gowda, Thomas H. Marek, Terry A. Howell, Jerry Moorhead, Suat Irmak

Department of Agricultural and Biological Systems Engineering: Faculty Publications

A sensitivity analysis was conducted to determine the relative effects of measurement errors in climate data input parameters on the accuracy of calculated reference crop evapotranspiration (ET) using the ASCE-EWRI Standardized Reference ET Equation. Data for the period of 1995 to 2008 from an automated weather station located at the USDA-ARS Conservation and Production Research Laboratory at Bushland, Texas were used for the analysis. Results

indicated that grass (ET_os) and alfalfa (ET_rs) reference crop ET were most sensitive to measurement errors in wind speed and air temperature followed by incoming shortwave (solar) radiation, and that data …

Evaluation Of A Rhodamine-Wt Dye/Glycerin Mixture As A Tracer For Testing Direct Injection Systems For Agricultural Sprayers, Joe D. Luck, Scott A. Shearer, Brian D. Luck, Fred A. Payne

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The purpose of this study was to provide valuable insight regarding the use of Rhodamine WT (red) dye as a tracer for evaluating injected concentrations. More specifically, the effects of mixing the dye with glycerin to simulate the viscosity of a pesticide (e.g., glyphosate) or injecting the dye/glycerin mixture into deionized (DI) versus tap water on developing appropriate calibration equations were evaluated. Test results indicated that mixing the dye in a solution of glycerin and DI water significantly affected absorbance measurements compared to the dye mixed solely in DI water. The error in estimating absorbance was 7.4% between the two …

Swat: Model Use, Calibration, And Validation, Jeffrey G. Arnold, Daniel N. Moriasi, Philip W. Gassman, Karim C. Abbaspour, Michael J. White, Raghavan Srinivasan, Chinnasamy Santhi, Daren Harmel, Ann Van Griensven, Michael W. Van Liew, Narayanan Kannan, Manoj K. Jha

Department of Agricultural and Biological Systems Engineering: Faculty Publications

SWAT (Soil and Water Assessment Tool) is a comprehensive, semi-distributed river basin model that requires a large number of input parameters, which complicates model parameterization and calibration. Several calibration techniques have been developed for SWAT, including manual calibration procedures and automated procedures using the shuffled complex evolution method and other common methods. In addition, SWAT-CUP was recently developed and provides a decision-making framework that incorporates a semi-automated approach (SUFI2) using both manual and automated calibration and incorporating sensitivity and uncertainty analysis. In SWAT-CUP, users can manually adjust parameters and ranges iteratively between autocalibration runs. Parameter sensitivity analysis helps focus the …

Soil Water Extraction Patterns And Crop, Irrigation, And Evapotranspiration Water Use Efficiency Of Maize Under Full And Limited Irrigation And Rainfed Settings, Koffi Djaman, Suat Irmak

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The effects of full and limited irrigation and rainfed maize production practices on soil water extraction and water use efficiencies were investigated in 2009 and 2010 under center-pivot irrigation near Clay Center, Nebraska. Four irrigation regimes (fully irrigated treatment (FIT), 75% FIT, 60% FIT, and 50% FIT) and a rainfed treatment were implemented. The crop water use efficiency (CWUE, or crop water productivity), irrigation water use efficiency (IWUE), and evapotranspiration water use efficiency (ETWUE) were used to evaluate the water productivity performance of each

treatment. The seasonal rainfall amounts in 2009 and 2010, respectively, were 426 mm (18% below normal) …

Large-Scale On-Farm Implementation Of Soil Moisture-Based Irrigation Management Strategies For Increasing Maize Water Productivity, Suat Irmak, Michael J. Burgert, Haishun Yang, Kenneth G. Cassman, Daniel T. Walters, William R. Rathje, Jose O. Payero, Patricio Grassini, Mark S. Kuzila, Kelly J. Brunkhorst, Dean E. Eisenhauer, William L. Kranz, Brandy Vandewalle, Jennifer M. Rees, Gary L. Zoubek, Charles A. Shapiro, Gregory J. Teichmeier

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Irrigated maize is produced on about 3.5 Mha in the U.S. Great Plains and western Corn Belt. Most irrigation water comes from groundwater. Persistent drought and increased competition for water resources threaten long-term viability of groundwater resources, which motivated our research to develop strategies to increase water productivity without noticeable reduction in maize yield. Results from previous research at the University of Nebraska-Lincoln (UNL) experiment stations in 2005 and 2006 found that it was possible to substantially reduce irrigation amounts and increase irrigation water use efficiency (IWUE) and crop water use efficiency (CWUE) (or crop water productivity) with little or …

Evaporative Losses From A Common Reed-Dominated Peachleaf Willow And Cottonwood Riparian Plant Community, Isa Kabenge, Suat Irmak

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Our study is one of the first to integrate and apply within-canopy radiation physics parameters and scaling-up leaf-level stomatal resistace (r_L) to canopy resistance (r_c) approach to quantify hourly transpiration (TRP) rates of individual riparian plant species—common reed (Phragmites australis), peachleaf willow (Salix amygdaloides), and cottonwood (Populus deltoides)— in a mixed riparian plant community in the Platte River Basin in central Nebraska. Two experimental years (2009 and 2010) were contrasted by warmer air temperature and presence of flood water in 2010. The seasonal average r_c values for common reed, …

P95. In Vivo Loads In The Cervical Spine: A Preliminary Investigation Using A Force-Sensing Implant, Rebecca A. Wachs, Mary Beth M. Grabowsky, Joseph C. Glennon, Eric H. Ledet

Department of Agricultural and Biological Systems Engineering: Faculty Publications

BACKGROUND CONTEXT: It is estimated that up to 80% of the general population will experience at least one significant bout of low back pain in their lifetime. The leading known cause of low back pain is degenerative disc disease (DDD). Many established risk factors for low back pain and DDD are mechanical in nature and are often related to occupational activities, such as poor posture and frequent/heavy lifting. Altered mechanical loading in the spine has been shown to be a potential stimulus for disc degeneration. However, a link between occupational/environmental factors and intervertebral loading has never been demonstrated in vivo. …

Curcumin-Loaded Magnetic Nanoparticles For Breast Cancer Therapeutics And Imaging Applications, Murali M. Yallapu, Shadi F. Othman, Evan T. Curtis, Nichole A. Bauer, Neeraj Chauhan, Deepak Kumar, Meena Jaggi, Subhash C. Chauhan

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Breast cancer is a commonly diagnosed cancer among women in the United States. It is estimated that 230,480 women were diagnosed with, and 39,520 women died from, breast cancer in 2011 in the United States.¹ Basal-like breast cancer accounts for 15% of all breast cancers and has a poor prognosis. The majority of these cancers are referred to as triple-negative breast cancers because they do not over express estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2.^2,3 Chemotherapy is an effective option to treat such cancers; however, chemotherapy is always associated with several sets of side …

History Of The Biological Systems Engineering Program In Nebraska, University Of Nebraska-Lincoln, William E. Splinter

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The Farm Machinery/Agricultural Engineering/Biological Systems Engineering program current and former faculty members at the University of Nebraska, as demonstrated here, has made a statewide, national, and worldwide impact on the efficient production of food. The quality of this recognition is evidenced best by peer professionals through recognized ASABE awards received by Nebraska alumni or professors. Since its inception in 1909 and until 2010, there have been 10 national presidents, 19 gold medal recipients and 33 named national award recipients. Currently there are 31 ASABE Fellows and two members of the National Academy of Engineering. This national recognition comes as a …

Stage-Dependent Transient Storage Of Phosphorus In Alluvial Floodplains, Derek M. Heeren, Garey A. Fox, Ronald B. Miller, Daniel E. Storm, Amanda K. Fox, Chad J. Penn, Todd Halihan, Aaron R. Mittelstet

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Models for contaminant transport in streams commonly idealize transient storage as a well-mixed but immobile system. These transient storage models capture rapid (near-stream) hyporheic storage and transport, but do not account for large-scale, stage-dependent interaction with the alluvial aquifer. The objective of this research was to document transient storage of phosphorus (P) in coarse gravel alluvium potentially influenced by large-scale, stage-dependent preferential flow pathways (PFPs). Long-term monitoring was performed at floodplain sites adjacent to the Barren Fork Creek and Honey Creek in northeastern Oklahoma. Based on results from subsurface electrical resistivity mapping which was correlated to hydraulic conductivity data, observation …

Streambank Erosion And Instability Induced By Groundwater Seepage, Taber L. Midgley, Garey A. Fox, Glenn V. Wilson, Derek M. Heeren, Andrew Simon, Eddy J. Langendoen

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Excessive sediment is one of the most common surface water pollutants. It diminishes water quality and destroys aquatic habitat. Streambank erosion is known to be a major source of sediment in streams and rivers, contributing as much as 80% of the total sediment load in some watersheds. Little work has been done to study the effects of seepage on streambank erosion and failure. Prior research, primarily in the laboratory under well-defined and controlled conditions, has examined seepage as a mechanism for bank erosion, but more needs to be done to validate conclusions derived from the laboratory with field data. This …

Identifying Changes In Climatic Trends And The Fingerprints Of Landuse And Landcover Changes In The High Plains Of The Usa, Denis Mutiibwa

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Human activities such as conversion of natural ecosystem to croplands and urban-centers, deforestation and afforestation impact biophysical properties of land surface such as albedo, energy balance, and surface roughness. Alterations in these properties affect the heat and moisture exchanges between the land surface and atmospheric boundary layer. The objectives of this research were; (i) to quantitatively identify the High plains’ regional climate change in temperatures over the period 1895 to 2006, (ii) detect the signatures of anthropogenic forcing of LULC changes on the regional climate change of the High Plains, and (iii) examine the trends in evolving regional latent heat …

A Look At 20th Century Droughts, Vijay P. Singh, Ashok K. Mishra

2011 Symposium on Data-Driven Approaches to Droughts

Droughts exercise a profound effect on the social and economic fabric of nations. Many nations of the world experienced droughts encompassing the full spectrum of severity, areal extent and duration. The result has been that the economic development was hampered and many countries have not yet recouped fully from the ravages of droughts. The first decade of the 21st century has also witnessed varying degrees of droughts across the globe. Therefore, we ask the following questions: (a) Do droughts affect every part of the world? (b) Are there similarities in major droughts around the world? (c) Are climate change and …

Economic And Environmental Sustainability Of Using Bio-Fuels For Small Nebraska Greenhouses, David M. Mabie

Department of Environmental Engineering: Theses and Other Student Research

The primary goal of this paper was to increase profitability in Nebraska greenhouses by using biomass fuels for heating instead of propane. Several different fuels were tested, including whole shelled corn, dry distiller’s grains pelletized, wood pellets and blends between each biomass. The main fuel focus was on whole shelled corn. Bomb calorimetry tests were performed on biomass fuels and their respective ashes. Several furnace and heat exchanger efficiency tests were performed, with cost effectiveness analysis for each fuel type. Emissions data was also collected for each fuel on carbon monoxide, carbon dioxide, nitrous oxides, sulfuric oxides, and particulate matter. …

Estimation Of Land Surface Evapotranspiration With A Satellite Remote Sensing Procedure, Ayse Kilic, Ian Ratcliffe, Pariskhit Ranade, Kenneth Hubbard, Ramesh K. Singh, Babuarao Kamble, Jeppe Kjaersgaard

Great Plains Research: A Journal of Natural and Social Sciences (through 2013)

There are various methods available for estimating magnitude and trends of evapotranspiration. Bowen ratio energy balance system and eddy correlation techniques offer powerful alternatives for measuring land surface evapotranspiration. In spite of the elegance, high accuracy, and theoretical attractions of these techniques for measuring evapotranspiration, their practical use over large areas can be limited due to the number of sites needed and the related expense. Application of evapotranspiration mapping from satellite measurements can overcome the limitations. The objective of this study was to utilize the METRIC^TM (Mapping Evapotranspiration at High Resolution using Internalized Calibration) model in Great Plains environmental …

Do Invasive Riparian Woody Plants Affect Hydrology And Ecosystem Processes?, Julie Huddle, Tala Awada, Derrel Martin, Xinhua Zhou, Sue Ellen Pegg, Scott Josiah

Great Plains Research: A Journal of Natural and Social Sciences (through 2013)

© 2011 Copyright by the Center for Greot Plains Studies, University of Nebraska-Lincoln

Identification Of ‘Carbon Hot-Spots’ And Quantification 1 Of Ghg Intensities In The Biodiesel Supply Chain Using Hybrid Lca And Structural Path Analysis, Adolf Acquaye, Thomas Wiedmann, Kuishang Feng, Robert Crawford, John Barrett, Johan Kuylenstierna, Aidan Duffy, Lenny Koh, Simon Mcqueen-Mason

Articles

It is expected that biodiesel production in the EU will remain the dominant contributor as part of a 10% minimum binding target for biofuel in transportation fuel by 2020 within the 20% renewable energy target in the overall EU energy mix. Life cycle assessments (LCA) of biodiesel to evaluate its environmental impacts have, however, remained questionable, mainly because of the adoption of a traditional process analysis approach resulting in system boundary truncation and because of issues regarding the impacts of land use change and N2O emissions from fertiliser application. In this study, a hybrid LCA methodology is used to evaluate …

Comparison Of Aquifer Sustainability Under Groundwater Administrations In Oklahoma And Texas, Aaron R. Mittelstet, Michael D. Smolen, Garey A. Fox, Damian C. Adams

Department of Agricultural and Biological Systems Engineering: Faculty Publications

We compared two approaches to administration of groundwater law on a hydrologic model of the North Canadian River, an alluvial aquifer in northwestern Oklahoma. Oklahoma limits pumping rates to retain 50% aquifer saturated thickness after 20 years of groundwater use. The Texas Panhandle Groundwater Conservation District’s (GCD) rules limit pumping to a rate that consumes no more than 50% of saturated thickness in 50 years, with reevaluation and readjustment of permits every 5 years. Using a hydrologic model (MODFLOW), we simulated river-groundwater interaction and aquifer dynamics under increasing levels of ‘‘development’’ (i.e., increasing groundwater withdrawals). Oklahoma’s approach initially would limit …

Effect Of Additive On The Performance Characteristics Of Centrifugal And Progressive Cavity Slurry Pumps With High Concentration Fly Ash Slurries, Sunil Chandel, S.N. Singh, V. Seshadri

Coal Combustion and Gasification Products Journal Archive

Slurry pumps that are used in the hydraulic transportation of fly ash slurries through pipes in thermal power plants can be broadly classified into two main categories namely positive displacement and centrifugal pumps. The two types of pumps differ considerably in construction as well as in operating principle compared to the conventional pumps. The present study reports the effect of additive on the performance characteristics of centrifugal and progressive cavity screw pumps with fly ash slurries at high concentrations (above Cw < 50% by weight). Mixture of sodium carbonate and Henko detergent (5:1) at a concentration of 0.2% by weight has been used as an additive. For each type of pump, the effect of additive on the performance characteristics has been experimentally evaluated at rated speed with fly ash slurries in the concentration range of 50 to 70% by weight. The pump total head, overall efficiency and pump input power as a function of flow rate have been measured. The results obtained from the centrifugal slurry pump performance show that at rated speed, the performance of the pump improves with the addition of drag reducing additive. In the case of progressive cavity screw pump, pump performance characteristics and behavior were completely different as compared to the centrifugal slurry pump. At rated speed, the performance of screw pump deteriorates with the addition of drag reducing soap solution.

2011 Nebraska Water Monitoring Programs Report, Marty Link

Nebraska Department of Environmental Quality: Reports

The Nebraska Department of Environmental Quality (NDEQ) is charged with monitoring, assessing, and to the extent possible, managing the state’s water resources. The purpose of this work is to protect and maintain good quality water and encourage or execute activities to improve poor water quality. Monitoring is done on the over 18,000 miles of flowing rivers and streams, our greater than 280,000 acres of surface water in lakes and reservoirs, and the vast storage of groundwater in Nebraska’s aquifers.

Zinc Speciation In Power Plant Burning Mixtures Of Coal And Tires, Luis F.O. Silva, Marcos L.S. Oliveira, Carmen Serra, James C. Hower

Coal Combustion and Gasification Products Journal Archive

Fly ash from the cyclone-boiler co-combustion of high-S, high volatile bituminous coal and tire-derived fuel (tdf) was studied using a variety of chemical, optical, and microbeam techniques. Fly ash, dominated by Al-Si glass with lesser amounts of coalderived carbons, Fe-spinels, and tire-derived carbons, has Zn concentrations ranging from 2200 ppm (1st ESP row) to 6900 ppm Zn (3rd ESP row). Zinc occurs in Zn-rich nanoparticles in the Al-Si glass phases and as ZnO in amorphous and crystalline nanominerals, Fe- and Zn-sulfides, Pb-Al-Fe sulfates, and Zn sulfates. Iron-rich, Al- and Ti-bearing spinels contain accessory Zn2+,Cr3+,Mn2+, and Pb2+. Fe-sulfates and phosphates nanoparticles …

Co-Disposal Of Dry Fgd By-Product With Coal Gasification Ash And Inorganic Brines, Jabulani S. Mahlaba, P.C. Pretorius, Subal Maharajh, M.P. Augustyn

Coal Combustion and Gasification Products Journal Archive

There is a growing pressure from the environmental authorities and public bodies to reduce anthropogenic pollution. Stringent environmental legislation is being implemented for industries around the world, even more so for coal consuming industries. Control of gaseous emissions is one of the areas that are receiving considerable attention towards sustainable development. Coal combustion in coal-fired power utilities emits SO~x~ to the atmosphere. Dry flue gas desulphurisation (FGD) is a well known technology often used to mitigate sulphur emissions in coal-fired power utilities. It traditionally uses lime to neutralise SO~x~, and forms a mixture of anhydrite (CaSO~4~), and calcium sulphite (CaSO~3~). …

Magnetite Nanoparticles For Medical Mr Imaging, Zachary R. Stephen, Forrest M. Kievit, Miqin Zhang

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for non-invasive clinical diagnosis due to its high soft tissue contrast, spatial resolution, and penetration depth1. In addition, images are acquired without the use of ionizing radiation or radiotracers that would cause unwanted harmful side-effects. A considerable amount of research in medical MR imaging is focused on the development of contrast agents that can provide better delineation between healthy and diseased tissue. Magnetic nanoparticles (MNPs) are a major class of nanoscale material currently under extensive development for improved diagnosis of a wide range of diseases, …

A Multi-Analytical Approach To Understand The Chemistry Of Fe-Minerals In Feed Coals And Ashes, Marcos L.S. Oliveira, Frans Waanders, Luis F.O. Silva, Andre Jasper, Carlos H. Sampaio, Dursman Mchabe, Rachel S. Hatch, James C. Hower

Coal Combustion and Gasification Products Journal Archive

Seven feed coals used in the Brazilian power generation industry were obtained and subsequently analysed together with fly ash and bottom ash from a major Brazilian power plant. The samples were investigated by means of room temperature FeMo¨ssbauer analyses, X-ray diffraction, Raman spectroscopy, scanning electron microscope and petrographic analysis. In addition, nanometer-sized crystalline phases in coals and ashes were characterised using an energy-dispersive X-ray spectrometer and a high-resolution transmission electron microscope. The major identified Fe-bearing minerals in the coals were found to be actinolite, ankerite, chalcopyrite, chlorite, goethite, illite, ilmenite, magnesioferrite, natrojarosite, pyrite, pyrrhotite, and siderite; whilst in the fly …

Compositional Variations In Pilot Gasifier And Laboratory-Produced Slags And Their Impacts On Slag Viscosity And Coal Assessment, Alexander Ilyushechkin, Daniel Roberts, David Harris

Coal Combustion and Gasification Products Journal Archive

The flow behaviour of coal mineral matter at high temperatures is an important parameter for coal use in entrained-flow gasification technologies. Recently, gasification performance data was obtained from a series of pilot-scale gasification tests on a suite of well-characterised Australian black coals. Evaluation of the results of the pilot tests and the detailed laboratory investigations provided the opportunity for evaluation of the practical applicability of different laboratory and modelling techniques for coal assessment in terms of mineral matter behaviour in entrained flow gasification. A series of viscosity measurements was made over the range 1200–1600uC using slags produced in a pilot …

Compaction Of High-Ca Fly Ash-Al- And Al-Alloy-Composites: Evaluation Of Their Microstructure And Tribological Performance, Grigorios Itskos, Angeliki Moutsatsou, Pradeep K. Rohatgi, Nikolaos Koukouzas, Charalampos Vasilatos, Eleni Katsika

Coal Combustion and Gasification Products Journal Archive

In this study, highly calcareous and siliceous fly ash particles were utilized for the fabrication of Al- and Al-alloy-based MetalMatrix Composites (MMCs) by means of powder metallurgy. After compacting and sintering Al and Al/Si powders containing 10, 15, and 20wt. % ash particles, the homogenous (and with minimal amount of voids) microstructure of the produced composites was verified by means of Scanning Electron Microscopy (SEM). The composites were tested for their dry sliding wear behavior using a pin-on-disc machine against spheres of alumina. The worn surfaces of composites were then examined by using SEM and Energy Dispersive X-Ray Spectroscopy (EDS). …

Influence Of Chemical Reagents On Rheological Properties Of Fly Ash-Water Slurry At Varying Temperature Environment, H.K. Nail, M.K. Mishra, Karanam U.M. Rao

Coal Combustion and Gasification Products Journal Archive

About 70% of total electrical energy is generated from thermal power plants in India which in turn release about 160 Mt of fly ash as solid waste annually. Transportation and disposal of such a huge amount of fly ash is a major problem faced by the power plants. Presently fly ash is transported as lean slurry in pipe lines requiring about 80 to 85% of water with high energy input. A major impediment in high volume transportation of fly ash is its high specific gravity as compared to that of water. The objective of the present study was to evaluate …

Impact Of Manufactured Coal Ash Aggregates On Water Quality During Open Pit Restoration: 1. A Statistical Screening Test, Sangchul Hwang, Isomar Latorre

Coal Combustion and Gasification Products Journal Archive

Utilization of manufactured coal ash aggregates (MAs) as a subsoil substitute during restoration of an open pit was assessed in a three-factor, two-level factorial analysis. The factors of interest were the MA application rate (2:1 or 1:2 topsoil/MA volume ratio), rainfall intensity (high or low), and aggregate size (2.36–4.75 mm or 4.75–9.53 mm). Among the water quality parameters examined (pH, turbidity, heavy metal content (lead and cadmium), conductivity, and hardness), the last two parameters were significantly higher (p,0.05) in soil amended with MAs than in a control reactor using sand. A low rainfall intensity and larger aggregate size resulted in …

The Leachability Of Major Elements At Different Stages Of Weathering In Dry Disposed Coal Fly Ash, S.A. Akinyemi, A. Akinlua, W.M. Gitari, R.O. Akinyeye, L.F. Petrik

Coal Combustion and Gasification Products Journal Archive

Large quantities of solid residue are generated by coal-fired power stations in many parts of the World. The disposal and management of the unused fly ash remains a major problem to the environment. The weathered dry disposed ash cores comprise of major element constituents such as Al, Si, Ca, Mg, Fe, Mn, Na+ and K+. The mobility patterns and mineralogical associations of major elements in weathered dry disposed ash dumps aged 1-year-old, 8-year-old and 20-year-old from a coalfired power station in South Africa were investigated using a modified sequential extraction scheme. The extraction sequence was as follows: (1) water soluble, …