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.     

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.     

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.     

Natural radionuclides distribution and environmental impacts of ferruginous sand-siltstone (raw material) and their manufactured Ahmer oxide used as wall paints

Commercially known Ahmer oxide paints are prepared from raw material mainly composed of red iron oxides (hematite) and iron oxyhydroxides. The raw material used in manufacturing of Ahmer oxide comes from some localities in southwest Sinai such as Abu Thor, Allouga, and El lehian. The adsorption of uranium and other radioelements on iron oxides could make the raw material (red iron oxides) and their products environmentally hazardous. The studied samples were subjected to radiometric analysis using NaI (Tl) gamma-ray spectrometer. The average activity concentration of U, Th, Ra, and K are 108.7, 458.8, 88.8, and 627.5?Bq?kg^?1, respectively in raw material and 136.4, 14.6, 58.3, and 95.9?Bq?kg^?1 in Ahmer oxide. High values of activity concentrations of ²³⁸U, ²²⁶Ra, and ⁴⁰K were recorded in Allouga and El lehian raw material. High radioactivities of Allouga and El lehian raw material are mainly attributed to the presence of torbernite, zircon, and monazite, in addition to adsorbed elemental uranium in Ahmer oxide. absorbed dose rate (D), annual effective dose equivalent, radium equivalent activity (Ra_eq), external hazard index (H_ex), and internal hazard index (H_in), as well as representative gamma index (Iγ) were determined from the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K. Some of the studied samples do not satisfy the universal standards.     

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.     

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.     

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.     

Using trace element concentrations in Corbicula fluminea to identify potential sources of contamination in an urban river

We used the biomonitor, Corbicula fluminea, to investigate the contributions of trace elements associated with different point sources and land uses in a large river. Trace elements were analyzed in tissues of clams collected from 15 tributary streams draining five land use or point source types: agriculture, forest, urban, coal-fired power plant (CFPP), and wastewater (WWTP). Clams from forested catchments had elevated Hg concentrations, and concentrations of arsenic and selenium were highest (5.0+/-0.2 and 13.6+/-0.9 microg g(-1) dry mass (DM), respectively) in clams from CFPP sites. Cadmium concentrations were significantly higher in clams from urban and CFPP sites (4.1+/-0.2 and 3.6+/-0.9 microg g(-1) DM, respectively). Non-metric multidimensional scaling (NMS) of tissue concentrations in clams clustered at CFPP and forest/agriculture sites at opposite ends of the ordination space, and the distribution of sites was driven by Cu, Zn, Cd, and Hg.     

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.     

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.     

Environmental fate of tetracycline resistance genes originating from swine feedlots in river water

Tetracyclines are antibiotics commonly used in swine farms to treat disease and promote growth. However, there are growing concerns regarding the discharge of animal feces into the environment owing to the potential for development and dissemination of tetracycline resistance genes (TRGs). In this study, farming wastewater from one Chinese swine farm as well as river water from seven locations downstream of the farm was sampled. Polymerase chain reaction (PCR) showed that 12 TRGs, including six efflux pump genes (tet(B), tet(C), tet(D), tet(E), tet(G) and tet(L)), five ribosomal protection proteins (RPPs) genes (tet(O), tet(M), tet(Q), tet(W) and tet(S)), and one enzymatic modification gene (tet(X)), were present in all wastewater and river water samples. Quantitative real-time PCR (qPCR) showed that the abundance of tet(C), tet(X), tet(O), tet(M), tet(Q) and tet(W) decreased with downstream flow. Among the detected TRGs, tet(C) had the highest abundance, ranging from 459.5 copies/16S rRNA gene copies in wastewater to 33.8 copies/16S rRNA gene copies in river water samples collected from the last location. Furthermore, pig-specific Bacteroidales 16S rRNA genetic marker was quantified by qPCR to determine the level of fecal pollution in the river water. Bivariate correlation analysis confirmed that the total relative abundance of the six TRGs was significantly correlated with the level of swine feces in the aquatic environment (R² = 0.63, P < 0.05), suggesting that swine feces mainly contributed to the spread of TRGs in the river water.

Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Environmental Science and Health, Part A to view the free supplemental file.     

Plant uptake of radionuclides in lysimeter experiments

The results of seven years lysimeter experiments to determine the uptake of 60Co, 137Cs and 226Ra into agricultural crops (endive, maize, wheat, mustard, sugarbeet, potato, Faba bean, rye grass) are described. The lysimeter consists of twelve monolithic soil profiles (four soil types and three replicates) and is located in Seibersdorf/Austria, a region with a pannonian climate (pronounced differences between hot and semi-arid summers and humid winter conditions, annual mean of precipitation: 517 mm, mean annual temperature: 9.8 degrees C). Besides soil-to-plant transfer factors (TF), fluxes were calculated taking into account biomass production and growth time. Total median values of TF's (dry matter basis) for the three radionuclides decreased from 226Ra (0.068 kg kg(-1)) to 137Cs (0.043 kg kg(-1)) and 60Co (0.018 kg kg(-1)); flux values exhibited the same ranking. The varying physical and chemical properties of the four experimental soils resulted in statistically significant differences in transfer factors or fluxes between the investigated soils for 137Cs and 226Ra, but not for 60Co. Differences in transfer between plant species and plant parts are distinct, with graminaceous species showing, on average, TF values 5.8 and 15 times lower than dicotyledonous species for 137Cs and 60Co, respectively. This pattern was not found for 226Ra. It can be concluded that 137Cs transfer is heavily influenced by soil characteristics, whilst the plant-specific factors are the main source of TF variability for 60Co. The variability of 226Ra transfer originates both from soil properties and plant species behaviour.     

Polychlorinated biphenyls in the Kupa River, Croatia, Yugoslavia

The presence of polychlorinated biphenyls (PCBs) was investigated in samples of water, suspended particles, sediments and fish from the Kupa river, Croatia, Yugoslavia, along a river stretch extending up to 10 km upstream and 200 km downstream of the primary contaminated karst region. Contamination was due to improper disposal of industrial waste discharge. The PCB levels detected in the samples collected downstream ranged from 1 to 52 ng 1⁻¹ for water, from 50 to 190 μg kg⁻¹ for suspended particles and from 8 to 39 μg kg⁻¹ for the sediment. A wide range of PCB concentrations, from 0.1 to 42.3 μg g⁻¹, which were measured in edible portions of different fish confirmed a long-term contamination of the river with PCBs. As the Kupa may be classified among low to moderately contaminated waters, it is essential that the investigations of the presence and behaviour of PCBs in the river and its environment be continued.     

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.     

Radium-226 in cattails, Typha latifolia, and bone of muskrat, Ondatra zibethica (L.), from a watershed with uranium tailings near the city of Elliot Lake, Canada

Radium-226 concentrations were measured in the main food plants (cattails, Typha latifolia) and bone of adult muskrats (Ondatra zibethica (L.)), taken from a study area near Quirke Lake in the Serpent River drainage basin. This watershed receives drainage containing radionuclides from the U tailings near the City of Elliot Lake, Ontario, Canada. Two control sites (one local, one 130 km distant) were also sampled. Radium-226 levels in cattails varied by plant part and place of collection. Roots sampled in the study area had the highest mean (226)Ra level (1135.0 mBq g(-1)), stems and leaves had 284.2 and 275.9 mBq g(-1), respectively (dry-weight basis, n = 6 in all cases). Local and distant control cattails carried much lower (226)Ra levels (20.2 and 15.2 mBq g(-1) dry weight, respectively, using pooled equal portions of all plant parts, n = 3 in both cases). Muskrats from waters with mean total (226)Ra levels in the period, 1984-1987 greater than 75.0 mBq litre(-1) ('study-high' sites), near U tailings within 10 km of Quirke Lake, had a mean (geometric) bone level of (226)Ra of 344.9 mBq g(-1) (dry-weight basis, n = 36); those from nearby waters, containing < 75.0 mBq litre(-1) of (226)Ra ('study-low' sites), had a mean bone level (80.3 mBq g(-1), n = 9) similar to animals taken in unaffected local control areas 20 km from the tailings (79.1 mBq g(-1), n = 12); animals from the distant control area, near Sudbury, Ontario, had the lowest mean burden (11.5 mBq g(-1), n = 24). Levels were unrelated to age or sex of the animals. Dry-weight based (226)Ra concentration ratios (bone concentration/plant tissue concentration) were calculated to range from 0.3-1.4 in the study-high area to 2.4-6.3 in the local control area. Wet-weight based concentration ratios were about 4.3 times higher. Concentration ratios were similar to values calculated for other species and in general agreement with values calculated for humans. The muskrat is judged to be a useful indicator (biomonitor) of environmental (226)Ra levels as there is a highly significant positive correlation coefficient (r = 0.74) between bone and ambient (water) concentrations of the radionuclide (F79 = 95.04, P < 0.0001) Estimated yearly (226)Ra intake by people eating muskrats was calculated to be below the current allowable level set by Canadian regulatory authorities.     

Radium-226 levels and concentration ratios between water, vegetation, and tissues of ruffed grouse (Bonasa umbellus) from a watershed with uranium tailings near Elliot Lake, Canada

Radionuclide levels measured in bone, muscle, kidney and liver tissues, gut contents and diet items of 47 grouse from the Serpent River drainage basin, containing uranium (U) tailings at Elliot Lake, and from control areas in Ontario, showed variation by site and tissue. The mean level of 226radium (Ra) in bones of grouse sampled from Elliot Lake (28.5 mBq g(-1)) was higher than that in bones of birds from a distant control site near Sudbury, Ontario (8.0 mBq g(-1)) but similar to the value in a local control population (28.1 mBq g(-1)). Birds from Mid- and Low-Serpent River basin populations (with 17.1 and 17.7 mBw g(-1), respectively) did not differ from local or distant control populations; muscle, liver and kidney had lower 226Ra concentrations, which did not differ significantly among populations. Levels of 226Ra in the crop contents and intestine did not differ significantly by site and were similar to those of food items consumed by the birds. Stomach content values were higher in birds sampled in Elliot Lake and at the local control site than in those taken at the distant control site; birds sampled downstream from Elliot Lake did not differ from distant controls in this regard. Levels of 232thorium (Th) and 230Th were below detection limits (0.1 microg g(-1) and 5.0 mBq g(-1), respectively) in bone, muscle and liver tissue in two grouse with elevated levels of 226Ra. Other radionuclides were measurable in some tissues: 238U in bone at 0.4 microg g(-1), in muscle to 0.2 microg g(-1), in liver to 1.0 gmg g(-1.), 228Th was found only in muscle (8.0 mBq g(-1)), 210poloniuim (Po) was found in bone, muscle and liver (maxima: 24.0, 7.0, 16.0 mBq g(-1)) with the exception of one muscle sample; 210lead (Pb) was detected in only one liver sample (50.0 mBq g(-1)). Environmental levels fell within ranges previously reported at the sites, or at similar locations elsewhere. Leaves of trembling and largetooth aspen growing in the basin had mean 226Ra levels of 14.8 and 52.7 mBq g(-1) (dry weight) respectively, and fungal material carried up to 215.4 mBq g(-1) (air-dried), with some variation by site. River and lake waters sampled near the U tailings had 118.1 mBq litre(-1) of dissolved 226Ra; at the distant control site the value was 12.1 mBq litre(-1). The concentration ratios (CR) between bone of grouse collected at the Elliot Lake sites and trembling and largetooth aspen leaves were 1.38 and 1.09 (fresh weight basis); from other diet items and to other tissues the values were less than unity. Bone tissue: water ratios, based on dissolved 226Ra levels, ranged to 30.89. People eating grouse from the study area are unlikely to consume radionuclides in excess of limits currently established by Canadian regulatory authorities.     

Patterns of mercury and methylmercury bioaccumulation in fish species downstream of a long-term mercury-contaminated site in the lower Ebro River (NE Spain)

Since the 19th century, large amounts of industrial waste were dumped in a reservoir adjacent to a chlor-alkali plant in the lower Ebro River (NE Spain). Previous toxicological analysis of carp populations inhabiting the surveyed area have shown that the highest biological impact attributable to mercury pollution occurred downstream of the discharge site. However, mercury speciation in fish from this polluted area has not been addressed yet. Thus, in the present study, piscivorous European catfish (Silurus glanis) and non-piscivorous common carp (Cyprinus carpio) were selected, to investigate the bioavailability and bioaccumulation capacities of both total mercury (THg) and methylmercury (MeHg) at the discharge site and downstream points. Multiple Correspondence Analysis (MCA) was applied to reduce the dimensionality of the data set, and Multiple Linear Regression (MLR) models were fitted in order to assess the relationship between both Hg species in fish and different variables of interest. Mercury levels in fish inhabiting the dam at the discharge site were found to be approximately 2-fold higher than those from an upstream site; while mercury pollution progressively increased downstream of the hot spot. In fact, both THg and MeHg levels at the farthest downstream point were 3 times greater than those close to the waste dump. This result clearly indicates downstream transport and increased mercury bioavailability as a function of distance downstream from the contamination source. A number of factors may affect both the downstream transport and increased Hg bioavailability associated with suspended particulate matter (SPM) and dissolved organic carbon (DOC).     

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.     

Eco-restoration: Simultaneous nutrient removal from soil and water in a complex residential-cropland area

An eco-restoration system to remove excess nutrients and restore the agricultural ecosystem balance was proposed and applied from August 2006 to August 2008 in a residential-cropland complex area (1.4 × 10⁵ m²) in Kunming, western China, where the self-purifying capacity of the agricultural ecosystem had been lost. The proposed eco-restoration system examined includes three main foci: farming management, bioremediation, and wastewater treatment. The results showed that the removal efficiencies of total phosphorus (TP) and total nitrogen (TN) from the complex wastewater were 83% and 88%, respectively. The Simpson’s diversity indices of macrophytes and zoobenthos indicated that the system had increased macrophyte and zoobenthic diversity as well as improved growth conditions of the plankton habitats. The results demonstrated that the proposed eco-restoration system is a promising approach for decreasing the output of nutrients from soil, improving agricultural ecosystem health, and minimizing the downstream eutrophication risk for surface waters.     

Cancer risk assessment after exposure from natural radionuclides in soil using Monte Carlo techniques

Purpose  

The purpose of this paper is to assess fatal cancer risk after external and internal (inhalation and ingestion) exposure from natural radionuclides in soil like ²³⁸U, ²³²Th, ⁴⁰K, and ²²⁶Ra on the territory of Bela Crkva, Serbia. Although receiving doses are low from sources like natural radionuclides in soil, because of stochastic effects of ionizing radiation, risk for developing cancer exists and can be quantified.