Radiometric and environmental impacts of mill tailings at experimental plant processing unit,Allouga, Egypt

Abstract

Uranium mining and ore processing are known to be harmful to the environment and human health if the waste generated is not managed properly. The aim of the present study is to determine the radiological indices in the mill tailings and review the possible attempts to utilize and minimize its hazardous effect. The activity concentrations of natural radionuclides, ²³⁸U, ²³²Th, ²²⁶Ra, and ⁴⁰K have been measured by gamma spectrometry using HP-Ge detector. The average activity concentrations of ²³⁸U, ²³²Th, ²²⁶Ra, and ⁴⁰K in the tailings wastes were 2071.8, 59.92, 6921.262, and 445. 57?Bq/kg respectively which are higher than the international average limit. The ranges of hazard indices such as Radium equivalent activity (Ra_eq), external hazard index (H_ex), internal hazard index (H_in), γ-radiation hazard index I_γ, Dose rate (nGy/h) and annual effective dose equivalent (AED), were estimated. Uraniumm isotopic ratios in the ore –material and mill tailing samples indicate migration out of radionuclides to the surrounding environment causing contamination and many dangerous diseases. Fairly, all investigated tailing waste samples do not satisfy the universal standards, the studied wastes relatively still have high uranium contents and need reprocessing.     

Radionuclides in some edible and medicinal macrofungal species from Tara Mountain,Serbia

Edible and medicinal macrofungi used in human diet represent not only important sources of nutritive elements but toxic substances as well (heavy metals and radionuclides). Radioactivity levels of four radionuclides (⁴⁰K, ¹³⁷Cs, ²²⁶Ra, ²²⁸Ra) were determined in the basidiomata (fruiting bodies of a Basidiomycetes) of six lignicolous (Fomitopsis pinicola, Ganoderma applanatum, Hericium clathroides, Megacollybia platyphylla, Pluteus cervinus, Trametes gibbosa) and three mycorrhizal (Boletus luridus, Boletus sp. 1, Boletus sp. 2) species as well as their soil (wood) substrates by gamma spectrometry (high-resolution high-purity germanium (HPGe) detector). The aim was to investigate their ability for radionuclide absorption according to transfer factors (from soil and wood), to predict potential bioindicator species as well as species with potential risk for human use. Samples were taken during years 2011 and 2012, at two sites in forest ecosystem of Tara Mountain (Serbia). Observed concentration ranges per dry weight were as follows: 29–3,020 Bq/kg (⁴⁰K), 21.9–735 Bq/kg (¹³⁷Cs), 3–39 Bq/kg (²²⁶Ra), and 2.0–18 Bq/kg (²²⁸Ra). Obtained results indicate that the type of basidiome (fleshy/tough), most likely due to a different metabolic rate, has a very important role in radionuclide accumulation. The highest activity concentrations of all analyzed radionuclides were found in species with fleshy basidiomata—P. cervinus, H. clathroides, M. platyphylla, and Boletus species. A species-specific influence on radionuclide uptake was more prominent comparing to habitat differences and the role of fungal trophic mode. No significant variations were observed regarding radionuclide activity among the same fungal species from different sampling sites.     

Assessment of natural radioactivity levels in soil samples from some areas in Assiut, Egypt

The natural radioactivity of soil samples from Assiut city, Egypt, was studied. The activity concentrations of 28 samples were measured with a NaI(Tl) detector. The radioactivity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K showed large variations, so the results were classified into two groups (A and B) to facilitate the interpretation of the results. Group A represents samples collected from different locations in Assiut and characterized by low activity concentrations with average values of 46.15?±?9.69, 30.57?±?4.90, and 553.14?±?23.19 for ²²⁶Ra, ²³²Th, and ⁴⁰K, respectively. Group B represents samples mainly collected from the area around Assiut Thermal Power Plant and characterized by very high activity concentrations with average values of 3,803?±?145, 1,782?±?98, and 1,377?±?78 for ²²⁶Ra, ²³²Th, and ⁴⁰K, respectively. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity (Ra_eq), the absorbed dose rate (D), the annual effective dose rate (E), the external hazard index (H _ex), and the annual gonadal dose equivalent (AGDE) have been calculated and compared with the internationally approved values. For group A, the calculated averages of these parameters are in good agreement with the international recommended values except for the absorbed dose rate and the AGDE values which are slightly higher than the international recommended values. However, for group B, all obtained averages of these parameters are much higher by several orders of magnitude than the international recommended values. The present work provides a background of radioactivity concentrations in the soil of Assiut.     

Uranium and neptunium retention mechanisms in Gallionella ferruginea/ferrihydrite systems for remediation purposes

The ubiquitous β-Proteobacterium Gallionella ferruginea is known as stalk-forming, microaerophilic iron(II) oxidizer, which rapidly produces iron oxyhydroxide precipitates. Uranium and neptunium sorption on the resulting intermixes of G. ferruginea cells, stalks, extracellular exudates, and precipitated iron oxyhydroxides (BIOS) was compared to sorption to abiotically formed iron oxides and oxyhydroxides. The results show a high sorption capacity of BIOS towards radionuclides at circumneutral pH values with an apparent bulk distribution coefficient (K_d) of 1.23 × 10⁴ L kg^?1 for uranium and 3.07 × 10⁵ L kg^?1 for neptunium. The spectroscopic approach by X-ray absorption spectroscopy (XAS) and ATR FT-IR spectroscopy, which was applied on BIOS samples, showed the formation of inner-sphere complexes. The structural data obtained at the uranium L_III-edge and the neptunium L_III-edge indicate the formation of bidentate edge-sharing surface complexes, which are known as the main sorption species on abiotic ferrihydrite. Since the rate of iron precipitation in G. ferruginea-dominated systems is 60 times faster than in abiotic systems, more ferrihydrite will be available for immobilization processes of heavy metals and radionuclides in contaminated environments and even in the far-field of high-level nuclear waste repositories.

     

Environmental Impact in Sediments and Seawater due to Discharges of Ba, 226Ra, 228Ra,V, Ni and Pb by Produced Water from the Bacia de Campos Oil Field Offshore Platforms

Produced water samples from the Bacia de Campos oil field offshore Pargo andPampo platforms were analyzed for Ba, ²²⁶Ra, ²²⁸Ra, V, Ni and Pb. The activity concentrations measured were in the range of 1.6–6.0 Bq/L for ²²⁶Ra and 0.7–8.2 Bq/L for ²²⁸Ra for both platforms. For Ba, V, Ni and Pb the concentrations measured were in the range of 5.6–25.7 mg/L, 0.15–0.46 μg/L, 4.85–12.14 μg/L and 4.04–12.37 μg/L. A strong correlation between barium and radium isotopes concentration was observed (²²⁶Ra: R² = 0.897;²²⁸ Ra: R² = 0.737). In order to evaluate the environmental impact from discharges of produced water into the sea, the seawater and sediment samples were collected at distances from 250 to 1000 m around the platforms. The seawater samples were analyzed for dissolved and particulate material and the sediment samples for total and leachable fraction. The results show that even for the shortest sampling distance (250 m) from the discharge point, Ba, ²²⁶Ra, ²²⁸Ra, V, Ni and Pb concentrations in seawater and sediment were similar to the local background, indicating that dispersion by local currents minimizes any environmental impact involving these parameters.     

Enhancement of natural radioactivity in fertilized soil of Faisalabad, Pakistan

Background, goal, and scope

Natural radioactivity in phosphate rock (PR) is transferred to phosphate fertilizer (PF) during the manufacturing process of the PF. The continuous addition of the PF to the cultivated soil accumulates the radionuclides in the land and increases the level of radioactivity in the soil. The purpose of the present study was to investigate the enhanced level of accumulated radioactivity due to the continuous addition of the PF in the farmlands of Nuclear Institute of Agriculture and Biology (NIAB) at Faisalabad in Pakistan. The selected study area consisted of the highly fertilized farmlands and an unfertilized barren land of the NIAB.

Introduction

The understudy area is very fertile for the growth of various types of crops; therefore, four agricultural research institutes have been established at Faisalabad and NIAB is one of those. The NIAB has developed various research farmlands at different places in Pakistan. The crop yield has been increased by adding various fertilizers in the farmlands. The addition of the PF accompanied with the radionuclides enhances radioactivity in the fields. Human being is exposed directly or indirectly to this radiological hazard. A prolong exposure may become a cause of health risk.

Materials and methods

The area of study consisted of three types of lands: the land under cultivation for the last 40 and 30?years called Site 1 and Site 2, respectively, and the barren land was called Site 3. A total of 75 soil samples were collected within the crop rooting zone (up to 25?cm deep) of the soil of the NIAB farms. The samples were dried, pulverized to powder, sealed in plastic containers, and stored to achieve equilibrium between ²²⁶Ra and ²²²Rn. Activity concentrations of the radionuclides ²³⁸U (²²⁶Ra), ²³²Th, and ⁴⁰K in soil samples were determined by using a high resolution gamma ray spectrometry system, consisting of an high purity germanium detector coupled through a spectroscopy amplifier with a PC based MCA installed with Geni-2000 software.

Results

The measured activity concentration levels of ⁴⁰K were 662?±?15, 615?±?17, and 458?±?20?Bq?kg^?1, ²²⁶Ra were 48?±?6, 43?±?5, and 26?±?4?Bq?kg^?1, and that of ²³²Th were 39?±?5, 37?±?5, 35?±?5?Bq?kg^?1, respectively, in the soil of the Sites 1, 2, and 3. Gamma dose rate 1?m above the soil surface was 55, 51, and 40?nGy?h^?1 from Sites 1, 2, and 3, respectively. External dose rates in the rooms constructed of the bricks made of the soil from Sites 1, 2, and 3 were 161, 149, and 114?nGyh^?1, respectively.

Discussions

Activity concentration values of ⁴⁰K and ²²⁶Ra in the soil of Sites 1 and 2 were higher than that in the soil of Site 3. The relative rise of ⁴⁰K was 43?% and 34?% and that of ²²⁶Ra was 85?% and 65?% respectively in these sites. Activity concentrations of ²³²Th in all these sites were in the background range. Gamma dose rate 1?m above soil surface of Sites 1 and 2 was 40?% and 30?% respectively higher than that from the soil of Site 3. The rise in activity of ⁴⁰K and ²²⁶Ra and gamma dose from the Site 1 was greater than that from the Site 2. The least activity and dose were observed from the Site 3. Gamma dose in the dwellings made of fertilized soil bricks of Site 1 and Site 2 were respectively calculated to be 41?% and 32?% higher than that in the abodes made of unfertilized soil bricks of Site 3.

Conclusions

Activity concentrations of ²²⁶Ra and ⁴⁰K were observed to be enhanced in the fertilized farmlands of the NIAB. Outdoor and indoor gamma dose as radiological hazard were found to be increasing with the continuous addition of PF in the understudy farmlands.

Recommendations

It is recommended that naturally occurring radioactive metal should be removed during the process of manufacturing of the PF from the PR.

Prospective

The rise in radioactivity in the farmlands due to the addition of the PF can be a source of direct or indirect exposure to radiation that may enhance cancer risk of the exposed individuals.     

Assessment of 222Rn emanation from ore body and backfill tailings in low-grade underground uranium mine

This paper presents a comparative study of ²²²Rn emanation from the ore and backfill tailings in an underground uranium mine located at Jaduguda, India. The effects of surface area, porosity, ²²⁶Ra and moisture contents on ²²²Rn emanation rate were examined. The study revealed that the bulk porosity of backfill tailings is more than two orders of magnitude than that of the ore. The geometric mean radon emanation rates from the ore body and backfill tailings were found to be 10.01?×?10^?3 and 1.03 Bq m^?2 s^?1, respectively. Significant positive linear correlations between ²²²Rn emanation rate and the ²²⁶Ra content of ore and tailings were observed. For normalised ²²⁶Ra content, the ²²²Rn emanation rate from tailings was found to be 283 times higher than the ore due to higher bulk porosity and surface area. The relative radon emanation from the tailings with moisture fraction of 0.14 was found to be 2.4 times higher than the oven-dried tailings. The study suggested that the mill tailings used as a backfill material significantly contributes to radon emanation as compared to the ore body itself and the ²²⁶Ra content and bulk porosity are the dominant factors for radon emanation into the mine atmosphere.     

Arsenic Background Definition: Introduction and Objectives

Produced water samples from the Bacia de Campos oil field offshore Pargo and Pampo platforms were analyzed for Ba, 226 Ra, 228 Ra, V, Ni and Pb. The activity concentrations measured were in the range of 1.6-6.0 Bq/L for 226 Ra and 0.7-8.2 Bq/L for 228 Ra for both platforms. For Ba, V, Ni and Pb the concentrations measured were in the range of 5.6-25.7 mg/L, 0.15-0.46 µg/L, 4.85-12.14 µg/L and 4.04-12.37 µg/L. A strong correlation between barium and radium isotopes concentration was observed ( 226 Ra: R 2 = 0.897; 228 Ra: R 2 = 0.737). In order to evaluate the environmental impact from discharges of produced water into the sea, the seawater and sediment samples were collected at distances from 250 to 1000 m around the platforms. The seawater samples were analyzed for dissolved and particulate material and the sediment samples for total and leachable fraction. The results show that even for the shortest sampling distance (250 m) from the discharge point, Ba, 226 Ra, 228 Ra, V, Ni and Pb concentrations in seawater and sediment were similar to the local background, indicating that dispersion by local currents minimizes any environmental impact involving these parameters.     

Adsorption of glyphosate on Brazilian subtropical soils rich in iron and aluminum oxides

Abstract

We investigated the adsorption of glyphosate onto five subtropical soils of Paraná and São Paulo states, Brazil, a region of intense agricultural activities, aiming at the determination of kinetic and isotherm adsorption parameters which enable the evaluation of the potential leaching of the herbicide. The adsorption was fast, being described by the pseudo-second order and intraparticle diffusion models, thus suggesting that mixed mechanisms are involved. The Oxisol containing the highest concentrations of metal oxides (209.5?g kg^?1 Fe₂O₃ and 160.2?g kg^?1 Al₂O₃) was the sample with the highest rate constant, indicating the adsorption sites are readily available. All the soils are rich in aluminum and iron oxides, explaining the Freundlich coefficients (K_F) between 642 and 1360?mg^1-1/n kg^?1 L^1/n, which are higher than most of the coefficients described for other soils around the world. The maximum desorption (15% of the adsorbed amount) was observed for the Oxisol. For the other soils, desorption ranged from 2 to 7%. These results suggest that the leaching of free glyphosate to nearby surface and groundwaters is unlikely unless excessive doses are used. The adsorption parameters are useful for managing the right doses applied to the crops, thus avoiding contamination of adjacent areas.     

Analysis of the different source terms of natural radionuclides in a river affected by NORM (Naturally Occurring Radioactive Materials) activities

The present work studied the radioacitivity impact of a coal-fired power plant (CFPP), a NORM industry, on the water of the Regallo river which the plant uses for cooling. Downstream, this river passes through an important irrigated farming area, and it is a tributary of the Ebro, one of Spain’s largest rivers. Although no alteration of the ²¹⁰Po or ²³²Th content was detected, the ^234,238U and ²²⁶Ra contents of the water were significantly greater immediately below CFPP’s discharge point. The ²²⁶Ra concentration decreased progressively downstream from the discharge point, but the uranium content increased significantly again at two sampling points 8 km downstream from the CFPP’s effluent. This suggested the presence of another, unexpected uranium source term different from the CFPP. The input from this second uranium source term was even greater than that from the CFPP. Different hypotheses were tested (a reservoir used for irrigation, remobilization from sediments, and the effect of fertilizers used in the area), with it finally being demonstrated that the source was the fertilizers used in the adjacent farming areas.     

Mobility of radium and trace metals in sediments of the Winterbeek: Application of sequential extraction and DGT techniques

For several decades, phosphate ores containing ²²⁶Ra as well as several trace metals have been processed in Belgium to produce calcium phosphate for use in cattle food. The waste water is discharged in two small rivers, the Laak and the Winterbeek.In this study, the levels of ²²⁶Ra and trace metals in surface water and sediments of the Winterbeek were investigated and the mobility of these compounds was assessed using DGT (Diffusive Gradient in Thin Films) and sequential extraction techniques.The concentrations of ²²⁶Ra and trace metals in water and sediment indicate a decreasing trend in inputs to the Winterbeek.The mobility of ²²⁶Ra, assessed by DGT, is related to the reductive mobilization of Fe. The sequential extraction technique shows that at some stations an important fraction of ²²⁶Ra is found to labile sediment phases.Diffusive ²²⁶Ra sediment fluxes, are however, relatively small and have only a minor contribution to the water column concentration of ²²⁶Ra.     

铁氧化物复合氧化铝催化臭氧化过程中溴酸盐的生成控制简

以市售活性炭、硅藻土和氧化铝小球为载体,考察了负载铁基活性组分对催化臭氧化过程中溴酸盐的控制情况,其中,铁基复合氧化铝小球体现出更好的溴酸盐还原特性和催化剂稳定性,证实催化剂中铁氧化物是溴酸盐得到有效控制的主要活性组分。进一步考察了铁基复合氧化铝小球催化臭氧化处理实际原水过程中对溴酸盐的生成控制,以及反应过程中溶解性有机碳（DOC）的去除情况。结果表明,与单独臭氧化相比,该催化剂既能有效去除水中的溶解性有机物,又能明显抑制溴酸盐的生成,反应50 h,其活性并没有明显下降。催化剂失活主要归因于吸附位点数量的下降,可以通过负载铁氧化物来实现催化剂的再生。     

Concentrations of heavy metal and radioactivity in surface water and sediment of Hazar Lake (Elaziğ, Turkey)

Concentration of heavy metals and natural gross radioactivity were measured in the surface water and sediment of Hazar Lake (Elazi?, Turkey). Eight sampling sites were pre-defined in different locations of the lake. A preliminary study on heavy metals (Zn, Fe, Mn, Ni, Cu, Cr, Co and Pb), major elements (Na, K, Ca, Mg) concentrations and natural radioactivity related to 226Ra, gross-alpha and gross-beta radiations in the surface water and deep sediments were determined. The obtained results showed that, in general, the heavy metals (Zn, Fe, Mn, Ni, Cu and Pb) and major elements (Na, K, Ca, Mg) concentrations in water did not exceed WHO (World Health Organization, 1999), EC (Europe Community, 1998), EPA (Environment Protection Agency, 2002) and TSE-266 (Turkish Standard, 1997) guidelines. Generally, heavy metals and major elements concentration of the sediments were found decrease in sequence of Fe>Mg>Ca>Mn>Zn>Ni>Cr>Cu>Co>Pb. The results of this study indicated that a general absence of serious pollution in the Hazar Lake. The results obtained from the radioactivity determination indicate that the surface water radioactivity concentration of 226Ra, gross-alpha and gross-beta were ranging from 0.52+/-0.02 to 2.02+/-0.06 Bq/l and from 0.65+/-0.03 to 2.52+/-0.07 Bq/l and from 0.01+/-0.01 to 0.14+/-0.01 Bq/l, respectively. Deep sediment radioactivity concentrations of 226Ra is ranging from 0.07+/-0.03 to 0.32+/-0.07 Bq/g.     

The ability of Helianthus annuus L. and Brassica juncea to uptake and translocate natural uranium and 226Ra under different milieu conditions

Seedlings of Helianthus annuus L. (HA) and Brassica juncea (BJ) were used to test the effect of the pH, the presence of phosphates, and the addition of ethylene-diamine-tetraacetic acid (EDTA) or citrate on the uptake and the translocation of uranium isotopes ((238)U, (235)U, and (234)U) and (226)Ra. The results indicated that the presence of phosphates generally reduces the uptake and transfer of uranium from the roots to the shoots of HA. In the case of BJ, while phosphate enhanced the retention of uranium by roots, the translocation was poorer. Likewise, for (226)Ra, the best translocation was in the absence of phosphates for both species. The addition of citrate increased the translocation of uranium for both species, but had no clear effect on the transfer of (226)Ra. The effect of EDTA was much more moderate both for uranium and for (226)Ra, and for both plant species. Only noticeable was a slightly better uptake of (226)Ra by BJ at neutral pH, although the translocation was lower.     

Investigation of uranium binding forms in selected German mineral waters

Cryogenic time-resolved laser-induced fluorescence spectroscopy was successfully used to identify uranium binding forms in selected German mineral waters of extremely low uranium concentrations (<2.0 μg/L). The measurements were performed at a low temperature of 153 K. The spectroscopic data showed a prevalence of aquatic species Ca₂UO₂(CO₃)₃ in all investigated waters, while other uranyl–carbonate complexes, viz, UO₂CO_3(aq) and UO₂(CO₃)₂ ^2?, only existed as minor species. The pH value, alkalinity (CO₃ ^2?), and the main water inorganic constituents, specifically the Ca²⁺ concentration, showed a clear influence on uranium speciation. Speciation modeling was performed using the most recent thermodynamic data for aqueous complexes of uranium. The modeling results for the main uranium binding form in the investigated waters indicated a good agreement with the spectroscopy measurements.     

Mineral constituents in Leccinum scabrum from lowland locations in the central Europe and their relation to concentration in forest topsoil

Leccinum scabrum is an edible mushroom common in European regions in the northern hemisphere. Macro and trace mineral constituents such as Ag, Al, Ba, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, P, Rb, Sr and Zn were studied in L. scabrum and in the top soil collected from the same location underneath soil substratum. The “pseudo-total” and labile (extractable fraction of minerals) were measured to get insight into the levels, distribution between the morphological parts of fruiting bodies, potential for their bioconcentration by mushroom and evaluated for human exposure via consumption of the mushroom. The sampling sites include the Dar?lubska Wilderness, Trójmiejski Landscape Park, Sobieszewo Island, Wdzydze Landscape Park and outskirts of the K?trzyn town in Mazury from the norther part of Poland. Median values of K, Rb and P concentrations in dehydrated L. scabrum were for caps in range 27,000–44,000 mg kg^?1, 90–320 mg kg^?1 and 6,200–9,100 mg kg^?1, and followed by Mg at 880–1,000 mg kg^?1, Ca at 48–210 mg kg^?1 and Al at 15–120 mg kg^?1. The median concentrations of Cu, Fe, Mn and Zn in caps were in range 15–27 mg kg^?1 db 38–140 mg kg^?1, 5.3–27 mg kg^?1 and 130–270 mg kg^?1. For Ba and Sr, concentrations on the average were at ～1 mg kg^?1, and almost equally distributed between the caps and stipes of the fruiting bodies. L. scabrum mushrooms were low in toxic Ag, Cd, Hg and Pb, for which the median values in dried caps from five locations were, respectively, in range 0.48–0.98 mg kg^?1 (cap to stipe index, Q_C/S, was 2.5–4.1), 1.0–5.8 mg kg^?1 (Q_C/S 2.9–3.8), 0.36–0.59 mg kg^?1 (Q_C/S 1.6–2.7) and 0.20–0.91 mg kg^?1 (Q_C/S 1.2–1.9). Substantial variations in the concentrations of the “pseudo-total” fraction (extracted by aqua regia) or labile fraction (extracted by 20% solution of nitric acid) of the elements determined in forest topsoils were noted between some of the locations examined. The elements K, P, Cd, Cu, Hg, Mn, Na, Rb and Zn can be considered as those which were bioconcentrated by L. scabrum in fruiting bodies, while the rates of accumulation varied with the sampling location.     

Effects of soil attributes and straw accumulation on the sorption of hexazinone and tebuthiuron in tropical soils cultivated with sugarcane

Brazil is the largest sugarcane producer in the world in which hexazinone (3-cyclohexyl-6-dimethylamino-1-methyl-1,3,5-triazine-2,4-dione) and tebuthiuron (1-(5-tert-butyl-1,3,4-thiadiazol-2-yl)-1,3-dimethylurea) are heavily used. Sugarcane harvesting is changing from the manual system with previous straw burning to the mechanized system without straw burning. The lack of burning results in soil organic carbon accumulation mainly in clayey soils, which should affect herbicides availability and fate. Therefore, we evaluated sorption of these herbicides in soil samples with and without straw burning. Both herbicides presented low apparent sorption coefficients (mean K_d,app= 0.6 and 2.4 L kg^?1 for hexazinone and tebuthiuron, respectively), suggesting that they may leach to groundwater. Moreover, their sorption correlated primarily with soil organic carbon (SOC), but iron oxide contents extracted with ammonium oxalate (Fe₂O₃^AOX) also affected it (K_d,app = ?0.228 + 0.0397 SOC + 0.117 Fe₂O₃^AOX for hexazinone and K_d,app = ?1.407 + 0.201 SOC + 0.348 Fe₂O₃^AOX for tebuthiuron). Soil organic carbon accumulation due to straw maintenance in the field positively affected sorption of both herbicides, but its effects were not enough to classify them as “non-leachers.”     

Impact of uranium mines closure and abandonment on groundwater quality

The aim of the study is to assess the evolving mine water quality of closed uranium mines (abandoned between 1958 and 1992) in the Czech Republic. This paper focuses on the changes in mine water quality over time and spatial variability. In 2010, systematic monitoring of mine water quality was performed at all available locations of previous uranium exploitation. Gravity flow discharges (mine adits, uncontrolled discharges) or shafts (in dynamic state or stagnating) were sampled. Since the quality of mine water results from multiple conditions—geology, type of sample, sampling depth, time since mine flooding, an assessment of mine water quality evolution was done taking into account all these conditions. Multivariate analyses were applied in order to identify the groups of samples based on their similarity. Evaluation of hydrogeochemical equilibrium and evolution of mine waters was done using the Geochemist’s Workbench and PHREEQC software. The sampling proved that uranium concentrations in mine waters did not predominantly exceed 0.45 mg/L. In case of discharges from old adits abandoned more than 40 years ago, uranium concentrations were below the MCL of US Environmental Protection Agency for uranium in drinking water (0.03 mg/L). Higher concentrations, up to 1.23 mg/L of U, were found only at active dewatered mines. Activity concentration of ²²⁶Ra varied from 0.03 up to 1.85 Bq/L except for two sites with increased background values due to rock formation (granites). Radium has a typically increasing trend after mine abandonment with a large variability. Concerning metals in mine water, Al, Co and Ni exceeded legislative limits on two sites with low pH waters. The mine water quality changes with a focus on uranium mobility were described from recently dewatered mines to shafts with water level maintained in order to prevent outflows to surface water and finally to stagnating shafts and discharges of mine water from old adits. The results were in good agreement with published experience on mine water stratification, its disturbance by pumping or natural water decant and the “first flush” phenomenon after mine flooding.     

Effect of the veterinary ionophore monensin on the structure and activity of a tropical soil bacterial community

Abstract

Monensin (MON) is a coccidiostat used as a growth promoter that can reach the environment through fertilization with manure from farm animals. To verify whether field-relevant concentrations of this drug negatively influence the structure and activity of tropical soil bacteria, plate counts, CO₂ efflux measurements, phospholipid fatty acids (PLFA) and community-level physiological profiling (CLPP) profiles were obtained for soil microcosms exposed to 1 or 10?mg kg^?1 of MON across 11?days. Although 53% (1?mg kg^?1) to 40% (10?mg kg^?1) of the MON concentrations added to the microcosms dissipated within 5?days, a subtle concentration-dependent decrease in the number of culturable bacteria (<1 log CFU g^?1), reduced (?20 to ?30%) or exacerbated (+25%) soil CO₂ effluxes, a marked shift of non-bacterial fatty acids, and altered respiration of amines (1.22-fold decrease) and polymers (1.70-fold increase) were noted in some of the treatments. These results suggest that MON quickly killed some microorganisms and that the surviving populations were selected and metabolically stimulated. Consequently, MON should be monitored in agronomic and environmental systems as part of One Health efforts.     

Evaluation of the 226Ra transport by river sediments surrounding the Brazilian uranium mining and milling facilities

A study of the (226)Ra contamination of the river sediments surrounding the Brazilian uranium mining and milling facilities was carried out. The nondetrital (226)Ra concentrations were determined performing a 0.5 N HCl leaching. Some preliminary speciations experiments using Tessier's sequential extraction procedure were also carried out. (228)Ra was used as a monitor of the natural variations. In general one could not observe increase in the non-detrital (226)Ra fraction between the pre-operational and operational data. Additionally, speciations experiments have shown the exchangeable fraction to be the main one responsible for (226)Ra content. Although the results indicate that the sediment is an important means of radium downstream transport, its availability suggests the soluble form to be the main path through the main foodchain. Attention must be paid to the release of (226)Ra bound to barium sulphate from the chemical processing effluent since increments of that fraction were observed in bottom sediments.