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G A O'Connor

Publications and source records attributed to G A O'Connor.

At least 19 recordsLinked to original sources
PubMed2006

Heavy metal sequential extraction methods--a modification for tropical soils.

Sequential extractions of metals can be useful to study metal distributions in various soil fractions. Although several sequential extraction procedures have been suggested in the literature, most were developed for temperate soils and may not be suitable for tropical soils with high contents of Mn and Fe oxides. The objective of this study was to develop a sequential fractionation procedure for Cu and Zn in tropical soils. Extractions were performed on surface (0-20 cm) samples of ten representative soils of Sao Paulo State, Brazil. Chemically reactive Mn forms were satisfactorily assessed by the new modified procedure. Amorphous and crystalline Fe oxides were more selectively extracted in a new two-step extraction. Soil-born Zn and Cu were primarily associated with recalcitrant soil fractions. The proposed procedure provided more detailed information on metal distribution in tropical soils and better characterization of the various components of the soil matrix. The new procedure is expected to be an important tool for predicting the potential effects of environmental changes and land application of metals on the redistribution of chemical forms of metals in tropical soils.

Copper↗
PubMed2006

Phosphorus release from a manure-impacted spodosol: effects of a water treatment residual.

Long-term depositions of animal manures affect P dynamics in soils and can pose environmental risks associated with P losses. Laboratory studies were done on P solubility characteristics in a manure-impacted Immokalee soil (sandy, siliceous, hyperthermic Arenic Alaquod) and the effectiveness of water treatment residual (WTR) in controlling P leaching. Soil samples with contrasting initial total P concentrations were prepared by mixing samples of a manure-impacted surface A horizon and a minimally P-impacted E horizon. Effects of mixing various ratios of A and E horizons, WTR rates (0, 25, 50, and 100 g kg(-1)), and depths of WTR incorporation (mixed throughout the soil column or partially incorporated) on P leaching were determined. Between 62 and 77% of total P was released from the soil mixes by successive water extractions, suggesting a considerable buffering capacity of this manure-impacted soil to resupply P into solution. Between 224 and 408 mg kg(-1) P were leached during the 36-wk leaching period in the absence of WTR. Mixing WTRs with soil reduced soluble P concentration in leachates by as much as 99.8% compared with samples without WTR. Thoroughly mixing WTR with the entire soil column (15 cm) was much more efficient than mixing WTR with only the top 7.5 cm of soil. Calcium- and Mg-P forms appear to control P release in soils without WTR, whereas sorption-desorption reactions probably determine P leaching in WTR-treated samples. Soil P distribution in various chemical forms was affected by WTR additions. Data suggest that WTR-immobilized P is stable in the long term.

Aluminum↗
PubMed2005

Runoff phosphorus losses from surface-applied biosolids.

Runoff losses of dissolved and particulate phosphorus (P) may occur when rainfall interacts with manures and biosolids spread on the soil surface. This study compared P levels in runoff losses from soils amended with several P sources, including 10 different biosolids and dairy manure (untreated and treated with Fe or Al salts). Simulated rainfall (71 mm h(-1)) was applied until 30 min of runoff was collected from soil boxes (100 x 20 x 5 cm) to which the P sources were surfaced applied. Materials were applied to achieve a common plant available nitrogen (PAN) rate of 134 kg PAN ha(-1), resulting in total P loading rates from 122 (dairy manure) to 555 (Syracuse N-Viro biosolids) kg P ha(-1). Two biosolids produced via biological phosphorus removal (BPR) wastewater treatment resulted in the highest total dissolved phosphorus (13-21.5 mg TDP L(-1)) and total phosphorus (18-27.5 mg TP L(-1)) concentrations in runoff, followed by untreated dairy manure that had statistically (p = 0.05) higher TDP (8.5 mg L(-1)) and TP (10.9 mg L(-1)) than seven of the eight other biosolids. The TDP and TP in runoff from six biosolids did not differ significantly from unamended control (0.03 mg TDP L(-1); 0.95 mg TP L(-1)). Highest runoff TDP was associated with P sources low in Al and Fe. Amending dairy manure with Al and Fe salts at 1:1 metal-to-P molar ratio reduced runoff TP to control levels. Runoff TDP and TP were not positively correlated to TP application rate unless modified by a weighting factor reflecting the relative solubility of the P source. This suggests site assessment indices should account for the differential solubility of the applied P source to accurately predict the risk of P loss from the wide variety of biosolids materials routinely land applied.

Agriculture↗
PubMed2002

Effects of residual and reapplied biosolids on performance and mineral status of grazing beef steers.

An experiment was designed to assess the mineral status of 60 Angus yearling beef steers grazing bahiagrass pastures fertilized with large amounts of biosolids from three sources: Baltimore, MD; Tampa, FL; and Largo, FL. Biosolids were classified as exceptional quality and thus had no regulatory restrictions on loading rate. They differed primarily in concentration of Mo (12 to 56 mg/kg of DM). Residual treatments (biosolids applied only the previous year) for Baltimore biosolids were applied at 22.4 and 44.8 t/ha, and Tampa biosolids were either 16.8 or 33.6 t/ ha. The reapplied treatments (applied in consecutive years) for both Baltimore and Tampa sludges were applied at 22.4, 44.8, 16.8 , and 33.6 t/ha, respectively. The two Largo biosolids treatments were either 56 or 112 t/ha and were applied only in the 2nd yr. Liver biopsies and blood samples were collected on d 1, 95, and 180. Liver and plasma were analyzed for minerals and blood was analyzed for hemoglobin, hematocrit, and superoxide dismutase of polymorphonuclear neutrophils. Experimental animals were generally adequate in macromineral status and Co, Fe, and Mn throughout the experiment. Copper deficiency was evident based on the clinical signs of hair coat discoloration, very low plasma Cu at d 95, and the continuous decline in liver Cu over 180 d. A sharp decline in plasma Cu was observed for all treatments from d 1 to 95, after which Cu concentrations rebounded to normal concentrations (> 0.65 microg/mL) by d 180. Liver Mo was well below concentrations indicating toxicity (> 5.0 mg/kg). The steep decline in liver Cu over the first 95 d reflects the dietary Cu deficiency and the possibility of high forage S (0.26 to 0.52%) interfering with Cu metabolism. Biosolids application to bahiagrass pastures was not detrimental to mineral status except for declining Cu stores; however, the controls likewise declined, but to a lesser degree.

Animal Feed↗
PubMed2000

Effects of pasture applied biosolids on performance and mineral status of grazing beef heifers.

Angus x Hereford heifers (n = 50) were randomly assigned to bahiagrass pastures treated with biosolids varying in mineral content and evaluated for mineral status, with special attention to Cu. Biosolids and NH4NO3 were all applied at the rate of either 179 kg N/ha (X) or twice this (2X). Fertilizer was applied to .81-ha pastures for the following treatments: 1) Baltimore biosolids (1X = 179 kg N/ha); 2) Baltimore biosolids (2X = 358 kg N/ha); 3) Tampa biosolids (1X = 179 kg N/ha); 4) Tampa biosolids (2X = 358 kg N/ha); or 5) control NH4NO3 (1X = 179 kg N/ha) applied at two times. Pastures were divided into five blocks with each treatment represented once in each block. Copper loads varied from 8.8 to 42.2 kg/ha, and Mo loads varied from .27 to 1.11 kg/ha. Heifers (two per pasture) grazed their assigned pastures exclusively for 176 d. Liver biopsies were taken from all animals at d 1, 99, and 176, and blood samples on d 1, 50, 99, 135, and 176. Liver and plasma were analyzed for selected mineral contents, and blood was analyzed for hemoglobin and hematocrit. Experimental animals were generally low in mineral status when assigned to pastures and deficient in Se and P. By d 50, plasma Ca, Mg, Se, P, and Zn were adequate for all treatments. Plasma Cu declined (P < .03) for all treatments from d 50 to 176. Plasma Cu reflected depleted liver Cu storage, with the two Tampa and highest Baltimore treatment means lower in plasma Cu than the control at 176 d. Liver Fe concentrations were adequate for all treatments, and Mo concentrations (< 2.18 mg/kg) did not approach levels indicative of toxicity. Liver Cu declined (P < .05) with time for all treatments. By d 99, animals receiving the two Baltimore treatments and the lowest Tampa application rate had lower (P < .05) liver Cu than the control, and all treatments were lower at 176 d. The decline of animal Cu status (liver and plasma) reflects the low Cu status of bahiagrass and the possibility of high forage S (.30 to .47%) interfering with Cu metabolism. Forage Mo was low but was slightly higher in biosolids-treated pastures. High levels of biosolids applications to bahiagrass pastures were not detrimental to mineral status except Cu, which had a tendency to decline in plasma and for all biosolids treatments declined in liver.

Animal Feed↗
PubMed1996

Organic compounds in sludge-amended soils and their potential for uptake by crop plants.

Numerous toxic organic chemicals (TOs), with a wide range of chemical properties, can occur in sewage sludges. The vast majority of sludge-borne TOs occur at low concentrations, and even lower TO concentrations are expected in sludge-amended soils. Further, most TOs are so strongly reactive in the soil-sludge matrix that their bioavailabilities to plants are expected to be low. A host of experimental techniques have been employed to measure TO plant uptake and to relate bioavailability to TO chemical and physical properties. The strengths and weaknesses of several experimental approaches are examined, and the resulting data are evaluated. Sound experimental data, especially field data and/or data from studies with endogenously sludge-borne TOs, indicate negligible contamination of crop plants with TOs in sludge-amended soils. Assessing the potential for plant uptake of sludge-borne TOs involves determining: (a) which TOs are most likely present in biosolids and what are their toxicities; (b) what quantities of TOs are likely to be added to the growth media via biosolids application; (c) what effects various dissipation/dispersion reactions have on the potential bioavailability of TOs; and (d) what are the various mechanisms for plant uptake/metabolism of TOs.

Biological Availability↗
PubMed1996

Residual block after mivacurium with or without edrophonium reversal in adults and children.

BACKGROUND: The rapid recovery from mivacurium- induced neuromuscular block has encouraged omission of its reversal. The purpose of this study was to determine, in children and in adults, whether failure to reverse mivacurium neuromuscular block was associated with residual neuromuscular block on arrival in the postanesthesia care unit. METHODS: In 50 children, aged 2-12 yr, and 50 adults, aged 20-60 yr, anesthesia was induced and maintained with propofol and fentanyl, and neuromuscular block was achieved by an infusion of mivacurium, to maintain one or two visible responses to train-of-four (TOF) stimulation of the ulnar nerve. At the end of surgery, mivacurium infusion was stopped, and 10 min later, reversal was attempted with saline or 0.5 mg x kg(-1) edrophonium by random allocation. On arrival in the postanesthesia care unit, a blinded observer assessed patients clinically and by stimulation of the ulnar nerve with a Datex electromyogram in the uncalibrated TOF mode. RESULTS: Children arrived in the postanesthesia care unit 8.2 +/- 3-4 min after reversal of neuromuscular block and showed no sign of weakness, either clinically or by TOF stimulation. Although TOF ratio was greater in children who had received edrophonium (1.00 +/- 0.05 vs. 0.93 +/- 0.01, P<0.01), TOF was >0.7 in all children. Adults arrived in the postanesthesia care unit 12.9 +/- 5.3 min after reversal of neuromuscular block(P<0.01 vs. children). Six in the saline group demonstrated weakness (two required immediate reversal of neuromuscular block, and TOF was <0.7 in four others), compared with TOF <0.7 in only one of the edrophonium group (P<0.05). CONCLUSIONS: This study demonstrated that, in adults, failure to reverse mivacurium neuromuscular block was associated with an increased incidence of residual block. Such weakness was not observed in children receiving similar anesthetic and neuromuscular blocking regimens.

Adult↗
PubMed1987

Leapfrog leg.

Explore the source record for details and available documents.

Athletic Injuries↗
PubMed1984

Spinal cord compression by an osteochondroma in a patient with multiple osteochondromatosis. Case report.

The authors present the case of a 24-year-old woman with osteochondromatosis who experienced gradual onset of cervical myelopathy. Metrizamide myelography and metrizamide-enhanced computered tomography revealed extensive extradural cervical spinal cord compression, and surgical removal of a lower cervical osteochondroma was performed. Although osteochondroma is the most common of the benign bone tumors, neurological involvement due to spinal cord compression is rare. Somatosensory evoked responses obtained before, during, and after surgery are also presented.

Adult↗
PubMed1981

Spinal cord conduction pathway for cerebellar evoked potentials from C-fibers.

Evoked responses from saphenous nerve C fiber stimulation were identified on the ipsilateral intermediate cerebellar cortex. This late potential has a latency between 180 and 250 msec, duration 50-70 msec, and an amplitude 10-20 micro V. The potential is conducted in the ipsilateral dorsal quadrant as determined by differential section of the spinal cord. The probable pathway is assigned to the dorsal spinocerebellar tract.

Animals↗
PubMedDate not supplied

A dynamic method of repair for acute and chronic acromioclavicular disruption.

The authors have presented a surgical procedure for disruption of the acromioclavicular joint with or without fracture of the lateral end of the clavicle. The results of the dynamic repairs have been excellent with restoration of stability and normal strength in all cases. The majority of this group were vigorous young high school college and professional athletes prior to their injury and all were returned to their previous activities.

Acromioclavicular Joint↗
PubMedDate not supplied

The saphenous nerve: its course and importance in medial arthrotomy.

Both lower extremities of 10 cadavers (20 specimens) were dissected to delineate the course of the saphenous nerve and its two major divisions (sartorial and infrapatellar branches). The course of the saphenous nerve followed the standard text description, except at the point in the sartorius muscle where the infrapatellar branch exited to become a subcutaneous structure. The location of this branch varied slightly in each cadaver but was the same for both lower extremities in the same cadaver. The location of the sartorial nerve and its relationship to the tendons of the pes anserinus was consistant in all 20 specimens. Since 69% of a group of 75 patients found altered sensation significant after routine sectioning of the infrapatellar nerve following medial meniscectomy, a group of surgeons at the University of Michigan is now protecting the infrapatellar branch of the saphenous nerve at operation. Early results on a small number of patients indicate that no alteration in sensation occurs if the nerve is carefully retracted.

Cadaver↗
PubMedDate not supplied

Bioavailability of biosolids molybdenum to corn.

This study was part of a larger effort to generate field data appropriate to the assessment of biosolids molybdenum (Mo) risk to ruminants. Corn (Zea mays L.) is an important component of cattle diet, and is a logical crop for biosolids amendment owing to its high N requirement. Paired soil and corn stover samples archived from two unique field experiments were analyzed to quantify the relationship (uptake coefficient, UC) between stover Mo and soil Mo load. Both studies used biosolids with total Mo concentrations typical of modern materials. Data from long-term (continuous corn) plots in Fulton County, IL confirm expected low Mo accumulation by corn stover, even at very high biosolids loads and soil Mo loads estimated to be near 18 kg Mo ha(-1). Uptake slopes were actually negative, but USEPA protocol would assign UC values of 0.001. Data from plots in Minnesota also suggested essentially no correlations between stover Mo and soil Mo loads for continuous corn. However, greater Mo accumulation in corn grown following soybean [Glycine max (L.) Merr.] suggests the possibility of enhanced Mo bioavailability to corn in corn-soybean rotations. Nevertheless, molybdenosis risk to cattle consuming corn stover produced on biosolids-amended land is small as stover Mo concentrations were always low and stover Cu to Mo ratios exceeded 2:1, which avoids molybdenosis problems.

Agriculture↗
PubMedDate not supplied

Biosolids effects on phosphorus retention and release in some sandy Florida soils.

The soil solid phase components most responsible for P sorption in Florida soils are Fe and Al oxides. Thus, we hypothesized that land application of biosolids would significantly increase a soil's P retention by increasing its content of P-sorbing solids, especially when biosolids with high Fe and Al concentrations are applied to soils that sorb P poorly. Biosolids effects were quantified by a series of single-point isotherms on soils from two field studies sampled for up to 4 yr after initial biosolids application. Biosolids additions had little effect on P retention in a soil with abundant oxalate-extractable Fe and Al and a correspondingly large native P-sorbing capacity. However, biosolids significantly increased P retention in a soil with low oxalate-extractable Fe and Al content and low native P-sorbing capacity. Biosolids effects on P retention lasted 1 to 3 yr after application, depending on biosolids source and rate of application, and generally mimicked persistence of increased extractable Fe and Al concentrations in the poorly P-sorbing soil. Disappearance of added Fe and Al (and, hence, P retention capacity) from the surface horizons over time was relatively rapid, perhaps due to abundant organic acid production associated with biosolids degradation. Phosphorus in biosolids containing (or tailored to contain) abundant Fe and/or Al can be expected to behave as a slowly available P source, and to be less subject to leaching losses than completely soluble P sources.

Absorption↗