Phosphogypsum is a by-product of the manufacture of phosphoric acid from phosphate rock and is a potential source of sulfur and calcium for crops. There are currently more than 700 million Mg of phosphogypsum in Florida alone stacked in waste piles and an additional 30 million Mg produced annually. A field study was conducted to determine whether addition of phosphogypsum to bahiagrass would increase production and quality. Results indicate that addition of up to 4.0 Mg/ha phosphogypsum increased bahiagrass yields, protein content, and in vitro digestibility of forage. This study has demonstrated that phosphogypsum can be used as an alternative source of sulfur and calcium for forage crops.

Phosphogypsum (PG), a by-product in the manufacture of phosphoric acid, is primarily gypsum, The USEPA regulates the removal of PG from stacks because it contains Ra-226. Measures to quantify the transfer of radioactivity in PG to the agricultural environment are needed. The objective of the study was to collect data needed for assessment of the radiological impacts of PG applied to two Florida soils. Field experiments using 0, 10, and 20 Mg PG ha(-1) were conducted for 2 yr at the University of Florida RCREC, Ona, FL. PG-attributable levels of Ra-226, Pb-210,and Po-210 were observed in the top 5-cm layer of the soils. Surface Rn-222 flux increased by 0.067 to 0.078 mBq m(-2) s(-1) per Mg PG ha(-1). Radionuclide concentrations in regrowth forages increased at one site where the first post-treatment rainfall did not occur until 20 d after PG application, In mature forages, radionuclide levels generally increased with PG in both soils. No effects on radionoclide levels in subsurface water down to 90 cm and only slight effects on gamma radiation and on airborne Rn-222 measured Im from the ground were noted, The Linear regression slope for a radiological parameter normalized with respect to the pertinent radionuclide applied per m(2) per Mg PG ha(-1) is proposed as the transfer factor (TF) of that radionuclide in PG to the agricultural medium in terms of that parameter, The TF permits the calculation of the potential effect on certain radiological parameters of PGs containing different radionuclide concentrations from the one used in this study.

The production of phosphoric acid by acidulation of rock phosphate with sulfuric acid produces phosphogypsum (PG) as a byproduct. Phosphogypsum is primarily CaSO4 . 2H(2)O and is a potential source of S and Ca for crops. Because of the presence of small amounts of Ra-226, the U.S. Environmental Protection Agency (EPA) has imposed severe restrictions on the use of PG. The objective of the study was to evaluate the radiological impact of applying phosphogypsum to tilled land. The experimental land spanned over two soils (Myakka-sandy, siliceous, hyperthermic Aeric Haplaquods and Pomona-sandy, siliceous, hyperthermic Ultic Haplaquods) tilled and cropped to annual ryegrass (Lolium multiflorum Lam.) for 3 crop-years. The PG with 792 Ra-226, 836 Pb-210, and 744 Po-210 Bq kg(-1) was applied all at once at the start of the study at 2 and 4 Mg ha(-1), with no PG as control, and harrowed into the top 15-cm layer of the soil. This layer initially contained 15.9, 28.1, and 14.1 Bq kg(-1) of Ra-226, 210Pb, and Po-210 respectively. The 4 Mg PG ha(-1) would have increased the initial soil Ra-226 and Po-210 by 9% each and Pb-210 by 5%, assuming a soil bulk density of 1500 kg m(-3). The results, averaged over crop-year and over the 3-crop-year period, showed no measurable increases in Ra-226, Pb-210, or Po-210 in soil down to 90 cm sampled in layers of 15 cm, in groundwater sampled at 90 to 120 cm depth, in regrowth and mature forages, and in gamma radiation and airborne Rn-222 both measured 1 m above the plots. However, Rn-222 flux measured at the soil surface increased by 0.74 x 10(-4) Bq m(-2) s(-1) per Mg PG ha(-1). Thus, yearly application of 0.675 Mg ha(-1) (upper level of annual application rates for gypsum as S or Ca source for crops) over a 100-year period of PG used in the study could increase Rn-222 nux from the experimental land from 8.14 x 10(-4) to 58.09 x 10(-4) Bq m(-2) s(-1) at the end of said period, assuming no loss of Ra-226, the source of Rn-222 in soil and PG. This 100-year-end value, however, would still be less than half of 160.0 x 10(-4) Bq m(-2) s(-1), the average Rn-222 nux for U.S. soils. However, because of the long half-life of Ra-226 (1620 years), it is important that the experimental or field rates-of-loss of PC-attributable Ra-226 in soil and soil surface Rn-222 flux be determined. This can be facilitated by using much higher PG rates and more replicates than those used in the present study.

Phosphogypsum (PG) is an effective source of S and Ca for bahiagrass (Paspalum notatum Fluegge) pasture and is recommended as a source of S and Ca for other crops as well. Earlier studies by the authors showed that rates up to 1.0 Mg ha(-1) applied annually or 2 or 4 Mg ha(-1) applied once over a 3-year period increased bahiagrass yields linearly. The present study used 10 and 20 Mg ha(-1), with no PG as control, applied to bahiagrass on a spodic soil to help define the potential effects of PG at agronomic rates (less than or equal to 1.0 Mg ha(-1))on PC-associated agro-environmental variables. Results showed that 20 Mg PG ha(-1) reduced forage yield. There was no difference in yield between the control and the 10 Mg ha(-1) rate. Phosphogypsum reduced soil Mg very strongly, hence, co-utilization of PG with byproducts rich in Mg is recommended for crops that need large amounts of Mg in addition to S and Ca. Topsoil and subsurface water pH decreased with PG rates on the short term, however, PG should increase the pH over the long term as H+ and Al3+ are replaced on the exchange complex by Ca2+, brought into the free water phase, and leached into the deeper layers. There were little or no measurable effects on Cd, Cr, Pb, Se, and Hg in soil, groundwater, or bahiagrass forage tissue even at 20 Mg ha(-1). Evaluation of the PG used in the study indicated that it is not hazardous as defined by the EPA "toxicity characteristic" criterion for hazardous solid wastes.

Phosphogypsum (PG) is a by-product gypsum (CaSO4.2H2O) of the manufacture of phosphoric acid and is a major potential source of S and Ca for crops. The PG used in this study contained 25.6% Ca, 62.1% SO4-S, and 18 pCi Ra-226 g-1. Radon (Rn-222) emanations from a bahiagrass (Paspalum notatum Flugge) pasture on a typical Florida Spodosol fertilized with PG up to 4.0 Mg ha-1 as a source of S were measured as atmospheric ambient radon (pCi L-1) using electret ion chambers (EIC) and as radon surface flux (pCi m2 s-1) using large-area activated charcoal canisters (LAACC). Atmospheric ambient radon values before PG application measured twice, each over a 30-d period from June 11 to August 24, 1990, and after PG application measured seven times, each over a 30- or 60-d period from August 25, 1990 to July 16, 1991, averaged 0.17 +/- 0.07 and 0.19 +/- 0.09 pCi L-1, respectively. Post-application measurements over treated and untreated plots (including external controls) were 0.20 +/- 0.08 and 0.18 +/- 0.09 pCi L-1, respectively. These ambient values can be compared with the US median value of 0.39 pCi L-1 recently reported in a National Ambient Radon Study conducted by the EPA, in which EIC's were also used. The radon flux at the surface of the ground measured three times from October 1990 to April 1991 using LAACC averaged 0.034 +/- 0.006 and 0.035 +/- 0.006 pCi m-2 s-1 for treated and untreated plots, respectively. These preliminary results of a continuing three-year study, suggest that application of PG at rates normally used to supply crops with Ca or S is not likely to result in significant increase in radon flux at the surface of the ground or in radon concentration in the above-ground ambient atmosphere.

Phosphatic clay is a waste product from the Florida phosphate mining industry presently totaling 41000 ha. These clays contain no phytotoxic materials, are high in most plant nutrients, and Ra-226 and average about 460 g moisture per kilogram. A split-plot field experiment was conducted to study forage and grain yield, forage quality, plant nutrient concentrations, changes in soil nutrients, and Ra-226 contents of four grain crops in various rotations. The crop rotations (i) corn (Zea mays L. 'Jacques 247')-sunflower (Helianthus annuus L. 'Cargill 205'), (ii) sunflower-grain sorghum (Sorghum bicolor L. Moench 'Northrup King Savanna 5'), (iii) soybean (Glycine max L. Merr. 'Williams 80')-grain sorghum, and (iv) grain sorghum-soybean 'University of Florida V-1') were grown on a dry phosphatic clay with and without a 50-mm surface layer of quartz-sand tailings. Nitrogen was the only fertilizer element applied. Results show that corn and grain sorghum produced highest (P < 0.05) forage yields (15.7 and 13.4 Mg ha-1) and highest grain yields (8955 and 4302 kg ha-1) per harvest, respectively. Soybean harvested for forage (Crop 1) contained the highest crude protein (217 g kg-1) and in vitro organic matter digestibility (736 g kg-1). Concentrations of P, K, Ca, Mg, and Fe in most of the forages were adequate for the diets of beef cattle (Bos taurus), while those of Mn, Cu, and Zn were low. Mehlich I-extractable soil P (1601 mg kg-1), Ca (46% mg kg-1), and Mg (1173 mg kg-1) were considered very high and changed little over the 4-yr production period. Application of 50 mm of sand tailings tended to increase (P < 0.05) Mehlich I-extractable P, Ca, Mn, Cu, Zn, and Fe. Radium-226 concentration in the forage of all grain crops averaged 8.5 Bq kg-1, which was about 17 times higher than that in the grain (0.4958 Bq kg-1) of the same crops. Concentrations of 226 Ra in the forage (8.288 Bq kg-1) and grain (0.6771 Bq kg-1) were 1.1% and 0.09% of the concentration in clay (761 Bq kg-1) respectively. These data indicate that phosphatic clays can be a valuable resource for the production of corn and sorghum grain that contain low concentrations of Ra-226.

AbstractPhosphate mining in Florida produces phosphatic clay and quartz‐sand tailings waste products. Presently there are about 41 000 ha of phosphatic clay (slime ponds) in Florida. These clays contain no phytotoxic materials, are high in most plant nutrients, and average about 460 g moisture kg−1. A split‐plot field experiment was conducted to study forage yield, quality, plant nutrient concentrations, changes in soil nutrients, and 226Ra contents of 12 grass‐N source treatments. The treatment combinations (i) bahiagrass (Paspalum notatum Fluegge var. saurae Parodi ‘Pensacola’) + N, (ii) bahiagrass + white clover (WC) (Trifolium repens L. ‘Arcadia’), (iii) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis ‘Florico’) + N, (iv) Florico stargrass + WC, (v) Florico stargrass + alfalfa (Medicago sativa L. ‘Florida 77’), (vi) Florico stargrass + carpon desmodium (Desmodium heterocarpon (L.) D.C. ‘Florida’), (vii) Limpograss [Hemarthria altissima (Poir) Stapf et. C.E. Hubb. ‘Floralta’] + N, (viii) Limpograss + WC, (ix) Stargrass (C. nlemfuensis Vanderyst var. nlemfuensis ‘Florona’) + N., (x) Florona stargrass + WC, (xi) Florona stargrass + red clover (Trifolium pratense L. ‘Nolins’), and (xii) Florona stargrass + alfalfa, were grown on dry phosphatic clay with and without a 50 mm surface layer of quartz‐sand tailings. Nitrogen (500 kg ha−1 yr−1) was the only fertilizer element applied on grasses. No fertilizer was applied on legumes during the 4‐yr period. Results indicated that Floralta hemarthria + N, Florona stargrass + N, and Florona stargrass + alfalfa produced highest dry‐forage yields averaging 20.8, 18.1, and 17.7 Mg ha−1. Florico stargrass + WC and Floralta hemarthria + WC had annual averages of 233 and 211 g CP kg−1 and 769 and 751 g IVOMD kg−1, respectively. Grass + N treatments were about 5 to 10 percentage units lower in CP than grass + legumes. Forage mineral concentrations for P, K, Ca, Mg, Mn, Cu, Zn, and Fe, ranged from 1.3 to 39 times higher than required for growing and finishing cattle (Bos sp.). Mehlich I‐extractable soil P (1650 mg kg−1), Ca (4588 mg kg−1), and Mg (1130 mg kg−1) were very high and changed little after 4 yr of forage production. Forages had a differential uptake of 226Ra with Florona stargrass + N (1.28 pCi g−1) having the highest uptake and Pensacola bahiagrass + N (0.32 pCi g−1) having the lowest uptake. Radium 226 in the phosphatic clay was 22 pCi g−1, which was 80 times higher than levels in an unmined Spodosol; however, plant uptake was three times higher than plants grown on unmined soil. Data indicated that phosphatic clays are a fertile resource that can be used for forage production.

Radium-226 is a naturally-occurring radionuclide found in enhanced levels at Florida phosphate mines. We inventoried levels of radium-226 in the tissues of 4 wetland bird species from 2 mined and 2 umined areas in Florida. Bone tissues of wood duck (Aix sponsa), mottled duck (Anas fulvigula), common moorhen (Gallinula chloropus), and double-crested cormorant (Phalacrocorax auritus) colleted at phosphate mines contained more radium-226 than tissues from unmined areas. Radium-226 concentrations in these birds were within guidelines inferred from radiological standards designed for human protection and should not adversely affect bird populations.

This paper reviews the data generated in studies of land radioactivity and indoor airborne radon progeny associated with mined and reclaimed phosphate lands in Florida. Highest indoor radon progeny levels are associated with the slab-on-grade type of construction. Concentrations exceeding 0.03 WL are associated with overburden soils, deposits and fill, while concentrations up to about 0.03 WL are associated with tailings. The lower limit for distinguishing increases above non-enhanced natural concentrations is on the order of 0.01-0.02 WL. Results of this study show that about 25% of the land produced by present methods of mining and reclamation practices would require restrictions on the type of construction or would require special construction methods. It is projected that with modification of mining and tailings disposal practices, virtually all of the land produced by mining and reclamation would be satisfactory for unrestricted construction use.

TWENTY-FIFTH ANNUAL MEETING OF THE HEALTH PHYSICS SOCIETY: Abstracts of papers presented at the meeting: PDF Only

Input materials, products and by-products from a number of Florida phosphate mines and chemical plants were analyzed for 226Ra and 238U by high resolution gamma spectrometry. Concentrations were distinctly lower in North Florida than in Central Florida. In the matrix, the two nuclides were essentially in radioactive equilibrium (North Florida, 8 pCi/g; Central Florida, 38 pCi/g). Following beneficiation, concentrations in rock product, waste clays and sand tailings were approx. 100–300%, 100% and 10–25%, respectively, of those in the matrix. Radioactive equilibrium is markedly disrupted in phosphoric acid production; uranium follows the phosphoric acid while 226Ra appears in the by-product gypsum (North Florida, 14 pCi/g; Central Florida, 26 pCi/g) and also in sediments and scales. Ammoniated phosphate fertilizers had relatively low levels of 226Ra but significant 238U (North Florida, 25 pCi/g; Central Florida, 70 pCi/g). On the other hand, triple superphosphate had significant concentrations of both 226Ra (North Florida, 12 pCi/g; Central Florida, 20 pCi/g) and 238U (North Florida, 26 pCi/g; Central Florida, 56 pCi/g). In the electric furnace process, radioactivity is transferred to the slag (Central Florida, 61 pCi/g of each nuclide). Within either region, nearly all sample types showed a considerable range of concentrations.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn occupational health and safety program for a major universityC. E. Roessler , B. G. Dunavant , and T. R. Turk Cite this: J. Chem. Educ. 1977, 54, 2, A77Publication Date (Print):February 1, 1977Publication History Received3 August 2009Published online1 February 1977Published inissue 1 February 1977https://pubs.acs.org/doi/10.1021/ed054pA77https://doi.org/10.1021/ed054pA77research-articleACS PublicationsRequest reuse permissionsArticle Views59Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Twelve Florida native wethers averaging 37 kg initially were used in a 2 x 2 factorial arrangement of treatments to study the absorption, excretion and retention of radioactive and stable lead as influenced by dietary intake of lead and pathway of isotope administration. The animals were fed a natural diet containing 3.1 ppm lead and received either 50 or 1000 ppm dietary lead as lead acetate. A 107-day preliminary feeding period was followed by the administration of 830 ..mu..Ci of /sup 210/Pb orally or 270 ..mu..Ci of /sup 210/Pb intravenously. Fecal and urinary collections were made for 8 days. Blood samples were obtained by venipuncture at periodic intervals up to 198 hr following dosing, after which all sheep were sacrificed and selected tissues removed for analysis. Within 8 days, 68.5 and .06% of the total /sup 210/Pb oral dose appeared in the feces and urine, respectively. Animals administered /sup 210/Pb intravenously excreted 12.5% of the total /sup 210/Pb injected in the feces and 12.0% in the urine. Percent injected dose of /sup 210/Pb in whole blood decreased rapidly to less than 10% at 96 hr following dosing. Radioactivity in the blood of sheep given the /sup 210/Pb orally was nevermore » detected in more than trace quantities. Low dietary lead and intravenous administration of /sup 210/Pb resulted in the greatest tissue retention of /sup 210/Pb when expressed as percent of dose per kilogram of dry tissue. Tissue levels of stable lead were higher in sheep fed the higher level of dietary lead.« less