Phosphate Dust Research Articles

Physiological and cannabinoid responses of hemp (Cannabis sativa) to rock phosphate dust under tropical conditions.

Growing a high-value crop such as industrial hemp (Cannabis sativa L.) in post-mining environments is economically and environmentally attractive but faces a range of biotic and abiotic challenges. An opportunity to investigate the cultivation of C. sativa presented itself as part of post-mining activities on Christmas Island (Australia) to profitably utilise disused phosphate (PS) quarries. Challenges to plant growth and cadmium (Cd) uptake were addressed in this study using potted plants under fully controlled conditions in a growth chamber. A complete nutritional spectrum, slow-release fertiliser was applied to all plants as a control treatment, and two levels of rock PS dust, a waste product of PS mining that contains 35% phosphorus (P) and 40ppm of naturally occurring Cd, were applied at 54 and 162gL-1. After 12weeks, control plants (no PS dust) significantly differed in phenological development, with no flower production, lower aboveground biomass and reduced photosynthesis efficiency than those with P applied as rock dust. Compared with the controls, the 54gL-1 level of P dust increased shoot biomass by 38%, while 162gL-1 increased shoot biomass by 85%. The concentration of Δ9-tetrahydrocannabinol also increased with the higher P levels. Cd uptake from PS dust by C. sativa was substantial and warrants further investigation. However, there was no increase in Cd content between the 54 and 162gL-1 application rates in seed and leaf. Results indicate that hemp could become a high-value crop on Christmas Island, with the readily available rock PS dust providing a source of P.

Rheological properties and small-angle X-ray scattering studies of phosphate dust obtained from baghouse collectors

Abstract Baghouse dust collectors are using in the drying unit of Beni Idir situated in Beni-Idir Khouribga city, Morocco, to retrieve phosphates particles from dust air-drying before its expulsion through the smokestacks. The phosphate dust samples used in this study were taken from the filtration chamber of the baghouse dust collectors. The first sample (S1) is untreated calcium phosphate dust, the second (S2) is the calcium phosphate dust from the outside of filter media while the third one (S3) is the calcium phosphate dust from the inside of filter media which causes clogging depth. In this paper, the rheology and the small-angle X-ray scattering (SAXS) of the three samples were investigated to elucidate the changes in terms of local structure, the viscosity, and the shear stress parameters. The rheological behavior of the dust samples was investigated for a solid mass concentration ranging from 50 to 60%, the three samples (S1) (S2) and (S3) had a solid mass concentration of C1=60%, C2=55% and C3=50% and a shear rate in the range from 1 to 1000 s−1. The results indicated that during the filtration process, the pseudo-plastic behavior of the dust phosphate changed to that of Bingham. Comparing the results of the sample’s viscosity, we found that the viscosity decreased during the process filtration. The SAXS results suggested that the dust phosphate samples possess a fractal surface structure of enormous dust particles with a rough surface interface. This new study highlights the rheological behavior of grain phosphates that could be extrapolated to other mining powder as grains material or in solution. It is important to understand the rheological characteristics of materials, their flow, and the subsequent deformation of matter as a result of the flow.

The effect of selected inhibitors on the characteristics of wood dust explosion

The mass concentration of four inhibitors which is required to suppress pine dust explosion were measured in laboratory-scale system. Measurements were conducted using four commercially available additives commonly used to decrease the fire and explosion hazards, three extinguishing powders: BC FOREX C, ABC Favorit X90, BC 101K and rock dust powder consisting calcium carbonate CaCO3 and magnesium carbonate MgCO3. The inhibition effect was investigated by measuring explosion pressure of various dust/powder mixtures using a 20 dm3 sphere by PN-EN 14034. On the basis of pressure-time curves the derivatives of pressure with respect to time (dp/dt), maximum explosion pressure pmax and maximum rate of explosion pressure rise (dp/dt)max were determined. It was found that inhibiting dust explosions with additives of various dry powders is a very effective way to decrease explosion effects. The experimental results have also shown that inhibiting effectiveness is strictly related to chemical composition of the powder. The order of effectiveness was monoammonium phosphate, sodium bicarbonate, potassium bicarbonate and rock dust.

Some Physical Features of Glasses Synthesized from Some Environmental Wastes

New glasses based on wastes of limestone, phosphate, and cement kiln dust besides white sand were manufactured. The structure of the prepared glasses was studied by FTIR, thermal analysis, UV spectroscopy and ultrasonic techniques. The analysis revealed that increasing the content of SiO2 influences the concentrations of the structural units constituting the amorphous network. The values of the physical parameters; the density, ultrasonic velocity, the elastic moduli, the refractive index, the optical band gap and the glass transition temperature increase as the SiO2 content increases, which was attributed to the former role of SiO2 which strengthens the calcium borate network and the conversion of non-bridging oxygens into bridging oxygens. These factors increase the crosslink density and connectivity within the glass network and hence its rigidity.

Calcium Composition and Microstructure of Coral <i>Stylophora pistillata</i> under Phosphate Pollution Stress in the Gulf of Aqaba

Corals and coral-reef ecosystems have been known to be extremely sensitive to environmental pollution, which effects on growth and calcification of their skeletons. Diffused phosphate dust during loading and shipment in seawater was found to cause serious impacts on corals by inhibiting calcification in their skeletons. Calcium concentrations in cultured fragments of coral Stylophora pistillata from Phosphate Terminal (PT) site in the Jordanian Gulf of Aqaba were investigated and compared with fragments from the same colony cultured in the Marine Science Station (MSS) site as marine protected area. Energy Disperse X-rays (EDX) spectroscopy and Scanning Electron Microscopy (SEM) were employed to determine the elemental composition of coral fragments and identify their microstructural characteristics, respectively. EDX results showed that coral samples from the Phosphate Terminal (PT) site were poorly mineralized with significantly low concentrations of calcium which were only about 12% of those from the MSS control site. Moreover, higher amounts of O and C in the elemental analysis of corals from the PT site indicated domination of organic matrix content in their skeleton which is typical for corals under phosphate pollution stress. This result was in accordance with the SEM images of the PT samples which exhibited alteration in their microstructure morphology resembling organic matrix as a major constituent, unlike the SEM images from the MSS protected area. These results strongly suggest that phosphate dust which is diffused during exportation through loading and shipping in the Gulf of Aqaba has adverse impacts on corals and marine ecosystem through decreasing calcium mineralization in their skeletons.

Assessment of elemental distribution and heavy metals contamination in phosphate deposits: potential health risk assessment of finer-grained size fraction

The concentrations and chemical distributions of heavy metals (Cd, Cr, Ni, Zn, U, and V) in the Al-Jiza phosphate ores were investigated. Typically, the mean concentration values of Cd, Cr, Ni, U, and Zn are 15 ± 8, 109 ± 21, 34 ± 6, 211 ± 55, 142 ± 55, and 161 ± 57 mg kg(-1), respectively. On the other hand, the encountered average concentration values of Cd, Cr, Ni, Zn, U, and V in the phosphate dust particles (<0.053) were found to be 22 ± 5, 179 ± 5, 67 ± 11, 441 ± 14, 225 ± 58, and 311 ± 9 mg kg(-1), respectively. The contamination factors of U and Cr are greater than 1, indicating that these heavy metals could be potentially hazardous, if released to the environment. Multivariate statistical analysis allowed the identification of three main factors controlling the distribution of these heavy metals and the other chemical constituents. The extracted factors are as follows: francolite mineral factor, clay minerals factor, and diagenesis factor. Health risk assessments of non-cancerous effects in finer-grained size fraction that might be caused by contamination with the heavy elements have been calculated for both children and adults. The risk assessments in case of children for non-cancerous effects showed that U has values greater than the safe level of hazard index (HI = 1). In case of adults, the value of risk for U is also higher as compared to those of Cd, Ni, Cr, and Zn where it lies within the safe range of hazard index (HI < 1). Child health risk assessment indicates that children are more vulnerable to contaminants from phosphate mining than adults.

Radioactivity levels and radiological hazard indices at the Saudi coastline of the Gulf of Aqaba

The coast of the Gulf of Aqaba is subjected to several sources of pollution due to several activities occurring at the coastal area. The activities vary between industrial, tourist and other development aspects at the Jordanian coastline of the Gulf of Aqaba. Phosphate industry has been considered a major source polluting the marine environment. According to official reports, 4–7 million tons of raw phosphate is exported through the Gulf of Aqaba. During transportation and loading, a small proportion of this enters the waters of the Gulf. Phosphate dust has also been considered another source of nutrients loading to the Gulf. 19 sediment samples were collected along the Saudi Gulf coastline, from the Saudi-Jordan border down to the end of the Gulf at Tiran Strait. Measurements of the activity concentrations of 226Ra, 232Th, 40K and 137Cs in Bq/kg (in dry weight) of the collected samples were carried out using gamma-ray spectrometry based on a highly pure germanium coaxial detector (HPGe). The concentrations of 238U and 232Th were also determined using ICP-MS technique. The average specific activities for 226Ra, 232Th, 40K and 137Cs were found to be 11.4±1.5, 22.5±3.7, 641.1±61.3 and 3.5±0.7 Bq/kg, respectively. The results show that the mean activity of 226Ra and 232Th is lower than the world average of 25 Bq/kg for both of them, whereas the mean value for 40K is about double the world average of 370 Bq/kg. The presence of 137Cs in the analyzed samples is low in most locations. The mean concentrations of 238U and 232Th in the study area are 1.2 and 5.4 mg/kg, respectively, and the ratio 238U/ 232Th is 0.2, which is lower than the global ratio of 0.3. The ratio of 226Ra/ 228Ra was found to decrease southwards in the direction of Tiran Strait, away from the phosphate industry in Jordan. Mean values for radium equivalent, absorbed dose, annual effective dose, external and internal hazard index and representative level index were determined as: 92.9 Bq/kg, 45.6 nGy/h, 56.0 μSv/y, 0.13, 0.28 and 0.73, respectively.

Concentrations of 222Rn, 220Rn and their decay products measured in outdoor air in various rural zones (Morocco) by using solid-state nuclear track detectors and resulting radiation dose to the rural populations

Alpha and beta activities per unit volume of air due to radon ((222)Rn), thoron ((220)Rn) and their progenies were measured in the outdoor air at different locations in Morocco by using both CR-39 and LR-115 type II solid-state nuclear track detectors (SSNTDs). In addition, the radon concentration was continuously measured in one location by using the methods with SSNTDs and AlphaGuard counter. The influence of the geological and meteorological conditions as well as phosphate and building material dust on the radon concentration in the outdoor air of the areas studied was investigated. The committed equivalent doses due to (218)Po and (214)Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of outdoor air. The annual effective dose due to radon short-lived progeny from the inhalation of outdoor air by the members of the rural population was estimated.

Impact of phosphate industry on the environment: A case study

This paper presents results obtained from studying the impact of the Syrian phosphate industry on the environment. This work is based on evaluating naturally occurring radionuclide concentrations in the surrounding environment at the locations of this industry, viz. mines, phosphate fertilizers factory and phosphate export platforms. Air particulates, soil, water (river, lake and sea water), biota and plant samples were collected and analyzed. Natural radionuclides ( 226Ra, natU, 210Po, 210Pb) were determined by means of low background gamma spectrometry and alpha spectrometry. The results showed that the distribution and enhancement of natural radionuclides in the surrounding environment in these three locations are mainly due to fallout of phosphate dust generated during loading and processing of phosphate ore. The extent of contamination was related to climate conditions. Radon gas and its daughters generated from phosphate ores were found to be the main source of enhanced concentrations of 210Po and 210Pb in soil and leafy plants. These results can be considered as baseline data and can be used to prove the effectiveness of any future pollution controls adopted.

Qualitative evaluation of the mineralogical and chemical composition of dry deposition in the central and southern highlands of Jordan.

The chemical and mineralogical composition of dry deposition in the western highlands of central and south Jordan at the end of the summer season 2000, reflect the composition of soils in addition to anthropogenic activities at these areas. Calcite predominated in the central region whereas calcite and quartz are the dominant minerals in south Jordan. The concentrations of Hg, Cr, Ni, Cu, Pb and Zn were higher in central Jordan, which might be attributed to higher anthropogenic activities than south. On the other hand, Fe, Mn, Ti, Ba, Sr, Y and Rb were higher in the south of Jordan reflecting the composition of soil at these sites. At Aqaba city, the only port of Jordan, where Cr, Cd, As and S were higher than other areas. This variation might be attributed to the contribution of phosphate dust in the atmosphere through handling processes.

Experimental investigation of phosphate dust collection in impinging streams (IS)

AbstractAn experimental study on collection of dry phosphate dust and coalescence of moistened phosphate dust in an Impinging‐stream (IS) collector has been conducted in the presence and in the absence of a water spray.The total collection efficiency with a water spray of specific consumption of 0.3 kg water/kg dust was 95–97%. Air velocity at the inlet pipes varied between 10–30 m/s and the inclination angle with respect to the horizontal, a, of the IS was 40−60°. The water spray increased the collection efficiency by 5–20% in comparison to dry collection.In the coaxial configuration, α = 0°, it has been obtained that in the presence of a water spray, up to 55–85% of the dust accumulated on the walls of the collector, which was undesirable. Applying the inclined IS decreased the above quantities up to 5–15% with an optimal inclination angle of α = 40°.A simple model for collection of the particles has been established, showing a satisfactory agreement with experimental results.

Estimates of the Occupational Radiological Hazard in the Phosphate Fertilizers Industry in Poland

The radiological hazard for workers in the phosphate fertilisers industry was assessed based on measurements in five phosphate plants in Poland. Measurement of absorbed dose rates in air, gamma doses, radon gas concentrations in air, and concentrations of natural radionuclides (238U, 226Ra, 210Po, 232Th, and 40K) in samples of raw phosphate rocks, products and by-products were performed using an ionisation chamber, thermoluminescent detectors, solid state-nuclear track detectors, a and gamma spectrometry, respectively. Using models for dose estimates, individual occupational doses were evaluated for phosphate industry workers involved in the production of fertilisers. On average, the estimated dose for yearly exposure ranged from 2.8 to 5.6 mSv, with the biggest contribution typically coming from phosphate dust. This is a significant amount when compared with the value of the annual dose limit of 1 mSv for the public, but still well below the occupational dose limit of 50 mSv per year.

Fluoride content of water, dust, soils and cereals in the endemic dental fluorosis area of Khouribga (Morocco)

The fluoride contents of drinking water, dust, soil, straw, raw barley (ears and stems) and barley grains in Khouribga were compared with those from Beni-Mellal, 90 km east of Khouribga where no fluorosis occurs. Identical fluoride levels were found in water samples from both areas, whereas high amounts of F − were in soil, dust, dried straw and dried barley grown in Khouribga. Equilibrated with water, large phosphate rock particles, probably of francolite, and smaller phosphate particles of clay-contaminated francolite, randomly collected in the factories of Khouribga never contained more than 1.2 parts/10 6F −. Unwashed samples of straw and whole barley had a higher F − content than washed samples. The marked fluorosis in herbivores of the Khouribga area comes more from the ingestion of dust-contaminated food (unwashed straw and unwashed raw barley) with a high fluoride content than from inhalation of fluoride-containing dust. By contrast, the endemic human fluorosis in the same region is mostly due to inhalation of fluoride-containing phosphate dust, and not to fluoride in the drinking water and only exceptionally to fluoride deposited during storage onto cereals, because grains grown in Khouribga have a low fluoride content.

The uranium content of sediments from the Jordan Gulf of Aqaba

The uranium content of nearshore sediments in the Jordan Gulf of Aqaba has been determined. The concentrations are shown to vary according to sediment type or habitat in unpolluted areas, while in a polluted area the concentration is related to phosphate dust pollution.

Coral death from sewage and phosphate pollution at Aqaba, Red Sea

Localized pollution of coral reef areas is occurring at Aqaba, Red Sea, as a result of sewage discharge, and as a result of spillage of phosphate dust during loading of phosphate mineral onto ships. The rate of death of colonies of the coral Stylophora pistillata was found to be 4–5 times as great in the polluted area as in a control area. Coral damage in the control area is generally caused by grazing or by extreme low tide, but the cause of coral death in the polluted area was not readily apparent. The growth of algae, both on the damaged corals, and on glass slides placed out in the reef, was greatly stimulated in the polluted area, but it appeared that such algal growth was not the direct cause of coral death. Corals in the polluted area may be under stress because of reduced light intensity, inhibition of calcification by excess phosphate, and increased sediment load. It was found that in the polluted area there was a greater weight of sediment settling on the glass slides for a given weight of algae. But in addition, since algal growth was faster in the polluted area, the sediment load was increased by the sediment trapping capacity of the enhanced algal growth. Thus it is suggested that increased algal growth stimulated by increased nutrient concentrations may be important in greatly increasing the sediment load experienced by corals.

High blood and urine levels of cadmium in phosphate workers: a preliminary investigation.

A preliminary study is described in which blood and urine levels of cadmium are determined in phosphate fertilizer workers exposed to phosphate dust. Control samples were taken from non-smokers who did not eat oysters regularly and who had eaten none for at least four weeks prior to the study. A cross section of phosphate workers was sampled. Various blends of phosphate fertilizers were analyzed. Analysis was by graphite furnace atomic absorption spectrometry. Results show that levels in fertilizers ranged from 42-147 ppm. The mean whole blood level of phosphate workers was 7.21 + or - 2.05 ng/ml and 0.92 + or - 0.18 ng/ml in controls. The mean urine level of phosphate workers was 5.24 + or - 0.53 ng/ml compared to 0.54 + or - 0.20 ng/ml for controls. No immediate symptoms of acute or subacute cadmium intoxication were observed but high levels indicate a need for studies to elucidate any long-term effects of exposure to cadmium-containing phosphate dust. 3 tables (JMT)

A study of dental mottling in children in Khouribga, Morocco

The prevalence of dental mottling is known to be high in Khouribga. However, the fluoride content of the drinking water is too low to explain the high prevalence and severity of dental mottling. Our purpose was to study the distribution of dental mottling in Khouribga and to attempt to find the aetiological factor responsible for this high prevalence and severity of dental mottling. Using the criteria described by Dean (1934) 707 children in the age group 7 to 14 yr were examined. Dental mottling was correlated to place of residence and age. The results showed that the closer to the factory the child lived, the higher the severity of dental mottling. Analysis of the dust exhaust from the furnaces of the factory showed a content of fluoride of approximately 2.0 per cent. Furthermore, it was demonstrated that the severity of dental mottling was higher in 10–14 yr old children, than in 7–9 yr old children. This latter finding could be related to the installation of dust filters approximately 8 yr prior to the study, in an attempt to reduce the loss of phosphate during the refinement process. It is concluded that dental mottling in Khouribga is caused primarily by fluoride containing phosphate dust.

Ecology of coral reefs in the Gulf of Aqaba (Red Sea) influenced by pollution.

1. This paper summarizes observations performed during 1966, 1968, and 1972, on coral reef flats 7 km south of Eliat (Gulf of Aqaba, Red Sea). The aim of this research was to describe the change in numbers of living coral colonies found on the coral tables in connection with pollution occuring in this habitat. A transect technique, developed by Loya and Slobodkin (1971) was used in this research. 2. In each of the three years, 19 ten metre transects were performed in various directions, on the same coral tables. 3. In 1966, 541 living coral colonies were counted in a total of 190 m of transects. At the identical place, this number had decreased to only 195, in 1972. The decrease in corals was found to be accompanied by a prominant increase in algae growth, that expend and develop, thus covering the coral specimens. 4. Especially sensitive to algal development are the branching micropolypal, coral species, that are the representatives of the genera Acropora, Seriatopora, and Stylophora. Of the above three genera counted in 1966, only 10 out of 192 colonies were found intact, in 1972. 5. The high mortality of corals in this locality occured during the years in which an oil terminal plus a mineral and phosphate loading harbour were developed at Eilat. 6. The frequent oil spills, together with the phosphate dust that reaches the sea, seem to be the factors that cause eutrophication in the shallow lagoon waters of the coral region, and thus the development of algae on the coast of corals is stimulated.

Tests for phosphates from Rum Jungle, Northern Territory

Phosphate-rich rock from Rum Jungle, N.T., was tested as fertilizer against Christmas Island rock phosphate dust (CIRPD) and superphosphate in two pot and three field experiments. The Rum Jungle material had little short-term value as fertilizer, but the long-term residual effects were about 60 per cent of those of CIRPD. Calcining at 450�C gave a marked improvement in short-term response in pots, but had little effect in a long-term field experiment. Pelletting the Rum Jungle material with sulphur and Thiobacillus ('biosuper') increased its effectiveness in the field at the end of the second year to the equivalent of that of superphosphate.

Cholinesterase inhibition by organic phosphate dust. Whole blood cholinesterase inhibition in vitro by an organic phosphate antihelminthic.

Cholinesterase inhibition by organic phosphate dust. Whole blood cholinesterase inhibition in vitro by an organic phosphate antihelminthic.