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George A. O'Connor

Bio: George A. O'Connor is an academic researcher from University of Florida. The author has contributed to research in topics: Biosolids & Soil water. The author has an hindex of 34, co-authored 118 publications receiving 3717 citations. Previous affiliations of George A. O'Connor include New Mexico State University & University of Texas at San Antonio.


Papers
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Journal ArticleDOI
TL;DR: In this article, simple properties of chemicals -half-life (T1/2), log octanol-water partition coefficient (log Kow) and Henery's Law constant (Hc) -were developed to screen organic chemicals for potential plant uptake.

246 citations

Journal ArticleDOI
TL;DR: The phosphorus saturation index (PSI) based on a simple oxalate extraction of the WTR and biosolids is potentially useful for determining WTR application rates for controlled reduction of P in drainage when biosolid are applied to low P-sorbing soils.
Abstract: Laboratory and greenhouse studies compared the ability of water treatment residuals (WTRs) to alter P solubility and leaching in Immokalee sandy soil (sandy, siliceous, hyperthermic Arenic Alaquod) amended with biosolids and triple superphosphate (TSP). Aluminum sulfate (Al-WTR) and ferric sulfate (Fe-WTR) coagulation residuals, a lime softening residual (Ca-WTR) produced during hardness removal, and pure hematite were examined. In equilibration studies, the ability to reduce soluble P followed the order: Al-WTR > Ca-WTR = Fe-WTR » hematite. Differences in the P-fixing capacity of the sesquioxide-dominated materials (Al-WTR, Fe-WTR, hematite) were attributed to their varying reactive Fe- and Al-hydrous oxide contents as measured by oxalate extraction. Leachate P was monitored from greenhouse columns where bahiagrass (Paspalam notatum Flugge) was grown on Immokalee soil amended with biosolids or TSP at an equivalent rate of 224 kg P ha -1 and WTRs at 2.5% (56 Mg ha -1 ). In the absence of WTRs, 21% of TSP and 11% of Largo cake biosolids total phosphorus (P T ) leached over 4 mo. With co-applied WTRs, losses from TSP columns were reduced to 3.5% (Fe-WTR), 2,5% (Ca-WTR), and <1% (Al-WTR) of applied P. For the Largo biosolids treatments all WTRs retarded downward P flux such that leachate P was not statistically different than for control (soil only) columns. The phosphorus saturation index (PSI = [P ox ]/ [Al ox + Fe ox ], where P ox , Al ox , and Fe ox are oxalate-extractable P, Al, and Fe, respectively) based on a simple oxalate extraction of the WTR and biosolids is potentially useful for determining WTR application rates for controlled reduction of P in drainage when biosolids are applied to low P-sorbing soils.

188 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed a sequential fractionation procedure for Cu and Zn in tropical soils and performed on surface (0-20 cm) samples of ten representative soils of Sao Paulo State, Brazil.

188 citations

Journal ArticleDOI
TL;DR: In this article, the authors evaluated P forms and leachability of eight biosolids products, chicken manure (CM), and commercial fertilizer (triple superphosphate, TSP) for Bahiagrass (Paspalum notatum Flugge) for 4 mo on two acid, P-deficient Florida sands.
Abstract: Increasing emphasis on phosphorus (P)-based nutrient management underscores the need to understand P behavior in soils amended with biosolids and manures. Laboratory and greenhouse column studies characterized P forms and leachability of eight biosolids products, chicken manure (CM), and commercial fertilizer (triple superphosphate, TSP). Bahiagrass (Paspalum notatum Flugge) was grown for 4 mo on two acid, P-deficient Florida sands, representing both moderate (Candler series: hyperthermic, uncoated Typic Quartzipsamments) and very low (Immokalee series: sandy, siliceous, hyperthermic Arenic Alaquods) P-sorbing capacities. Amendments were applied at 56 and 224 kg P(T) ha(-1), simulating P-based and N-based nutrient loadings, respectively. Column leachate P was dominantly inorganic and lower for biosolids P sources than TSP. For Candler soil, only TSP at the high P rate exhibited P leaching statistically greater (alpha = 0.05) than control (soil-only) columns. For the high P rate and low P-sorbing Immokalee soil, TSP and CM leached 21 and 3.0% of applied P, respectively. Leachate P for six biosolids was <1.0% of applied P and not statistically different from controls. Largo biosolids, generated from a biological P removal process, exhibited significantly greater leachate P in both cake and pelletized forms (11 and 2.5% of applied P, respectively) than other biosolids. Biosolids P leaching was correlated to the phosphorus saturation index (PSI = [Pox]/[Al(ox) + Fe(ox)]) based on oxalate extraction of the pre-applied biosolids. For hiosolids with PSI < or = approximately 1.1, no appreciable leaching occurred. Only Largo cake (PSI = 1.4) and pellets (PSI = 1.3) exhibited P leaching losses statistically greater than controls. The biosolids PSI appears useful for identifying biosolids with potential to enrich drainage P when applied to low P-sorbing soils.

151 citations

Journal ArticleDOI
TL;DR: Phosphorus sorption kinetics by the WTRs exhibited a slow phase that followed an initial rapid phase, as typically occurs with metal hydroxides, which may be explained by intraparticle P diffusion in micropores.
Abstract: Drinking-water treatment residuals (WTRs) can immobilize excess soil phosphorus (P), but little is known about the long-term P retention by WTRs. To evaluate the long-term P sorption characteristics of one Fe- and one Al-based WTR, physicochemical properties pertinent to time-dependency and hysteresis of P sorption were assessed. This study also investigated the P sorption mechanisms that could affect the long-term stability of sorbed P by WTRs. Phosphorus sorption kinetics by the WTRs exhibited a slow phase that followed an initial rapid phase, as typically occurs with metal hydroxides. Phosphorus sorption maxima for both Fe- and Al-based WTRs exceeded 9100 mg of P kg-1 and required a greater specific surface area (SSA) than would be available based on BET-N2 calculations. Electron microprobe analyses of cross-sectional, P-treated particles showed three-dimensional P sorption by WTRs. Carbon dioxide gas sorption was greater than N2, suggesting steric restriction of N2 diffusion by narrow micropore openin...

150 citations


Cited by
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Journal ArticleDOI
Rolf Sander1
TL;DR: According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution as discussed by the authors, and a compilation of 17 350 values of Henry's Law constants for 4632 species, collected from 689 references is available at http://wwwhenrys-law.org
Abstract: Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles Therefore, it is necessary to understand the distribution between the phases According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution Henry's law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format The compilation contains 17 350 values of Henry's law constants for 4632 species, collected from 689 references It is also available at http://wwwhenrys-laworg

1,935 citations

01 Jan 2016

1,907 citations

Journal ArticleDOI
TL;DR: This review outlined the latest applications of iron oxide nanomaterials in wastewater treatment, and gaps which limited their large-scale field applications, as well as the outlook for potential applications and further challenges.

1,632 citations

Journal ArticleDOI
TL;DR: A comprehensive and critical review of the environmental fate of eighteen commercial phthalate esters with alkyl chains ranging from 1 to 13 carbons was performed by as discussed by the authors, which revealed that most published values exceed true water solubilities due to experimental difficulties associated with solubility determinations for these hydrophobic organic liquids.

1,400 citations

Journal ArticleDOI
TL;DR: The following tables highlight daily diet dry matter and nutrient density requirements for diffferent classes of cattle at various stages of production based on the National Research Council’s Nutrient Requirements of Beef Cattle.

1,123 citations