Radiation Protection and Environment

ORIGINAL ARTICLE
Year
: 2014  |  Volume : 37  |  Issue : 3  |  Page : 143--149

Comparison of natural distribution pattern of uranium in groundwater in the vicinity of tailings management facilities at Jaduguda and Turamdih in Singhbhum region, Jharkhand


VN Jha1, Rajesh Kumar2, NK Sethy1, SK Sahoo3, PM Ravi3, RM Tripathi4,  
1 Department of Atomic Energy, Jaduguda, Jharkhand; Health Physics Unit, Jaduguda, Jharkhand; Environmental Studies Section, Bhabha Atomic Research Centre, Mumbai; Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India
2 Department of Atomic Energy, Jaduguda, Jharkhand; Health Physics Unit, Turamdih, Jharkhand; Environmental Studies Section, Bhabha Atomic Research Centre, Mumbai; Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India
3 Department of Atomic Energy, Jaduguda, Jharkhand; Environmental Studies Section, Bhabha Atomic Research Centre, Mumbai; Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India
4 Department of Atomic Energy, Jaduguda, Jharkhand; Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India

Correspondence Address:
V N Jha
Health Physics Unit, Jaduguda Mines (PO), East Singhbhum, Jharkhand - 832 102
India

Abstract

The results of uranium analyses in groundwater samples collected from areas adjacent to Turamdih and Jaduguda sites of solid waste disposal facilities (tailings pond) of process waste of the uranium industry are presented in the paper. These villages are within a distance of 0.5 km from tailings pond at either site. The concentration of uranium in approximately one-third of the samples was below the minimum detection limit (MDL) of 0.5 mg/m 3 . The highest uranium concentration of 16 mg/m 3 was found in tube well sample at the base of uranium mineralized hill of Turamdih with a median concentration of 0.95 mg/m 3 . Around tailings management facility at Jaduguda, the median concentration was 1.1 mg/m 3 with a maximum concentration of 10.9 mg/m 3 . The variations in monitoring results reflect the nature of uranium mineralization at the two sites. The results around Turamdih tailings pond show a high degree of asymmetry. Barring the MDL values, the lognormal distribution of uranium in groundwater around Jaduguda tailings pond was observed. The results reflect the natural distribution of uranium around the facility and contribution of tailings pond was not found in groundwater sources adjoining these facilities.



How to cite this article:
Jha V N, Kumar R, Sethy N K, Sahoo S K, Ravi P M, Tripathi R M. Comparison of natural distribution pattern of uranium in groundwater in the vicinity of tailings management facilities at Jaduguda and Turamdih in Singhbhum region, Jharkhand.Radiat Prot Environ 2014;37:143-149


How to cite this URL:
Jha V N, Kumar R, Sethy N K, Sahoo S K, Ravi P M, Tripathi R M. Comparison of natural distribution pattern of uranium in groundwater in the vicinity of tailings management facilities at Jaduguda and Turamdih in Singhbhum region, Jharkhand. Radiat Prot Environ [serial online] 2014 [cited 2020 Jul 2 ];37:143-149
Available from: http://www.rpe.org.in/text.asp?2014/37/3/143/154867


Full Text

 INTRODUCTION



Dissolved uranium present in the groundwater is a potential source of exposure for members of the public through drinking water pathway in rural areas of India. Presence of soluble uranium compound in the earth crust as well as releases from anthropogenic activities like mining and milling of uranium, phosphate, copper and tin industries may enhance the level of uranium in the associated environment particularly in the groundwater. The distribution of uranium in groundwater depends on an array of variables such as type of uranium compound present in the earth crust or released into the environment, pH, redox condition and concentrations of coexisting dissolved ions.

In certain areas, if the economically viable deposits of uranium are present in the earth crust, uranium ore is excavated and processed depending on the mineralogy of the ore. Singhbhum region of Jharkhand is known for its widespread uranium deposit. Management of process waste or tailings from the uranium industry requires special consideration due to the huge quantity and radioactive nature of the waste. The existing waste management technology is based on fixation of uranium, heavy metals and others radionuclides by lime at elevated pH and separation of coarse and fine fractions. The coarse fraction is used as a backfill material and the fines are discharged into the waste depository called tailings pond. The leaching of the uranium series radionuclides by precipitation water followed by changes in physicochemical characteristics of the matrix may enhance its migration probability from the bulk pile to adjoining groundwater table. During the construction stage of tailings pond these aspects are considered by selecting the sites with hill support on two or more sides and multilayer barrier on the other sides to control the migration of radionuclides. If the states of art technology and control measures are effectively implemented to minimize the migration of uranium toward adjoining groundwater table, the probability of contamination of groundwater can be minimized to a great extent. Apart from the probable migration of uranium from the tailings pile, there is widespread uranium mineralization in this area and accordingly wide variation in uranium level in groundwater is expected around the tailings pond also. Due to the variability in solubility and precipitation conditions of the geological formation and the environment, lower and higher levels of uranium may occur in groundwater.

Present paper summarizes the results of uranium analyses in groundwater samples collected from areas around two different waste disposal sites of UCIL, that is, Turamdih and Jaduguda. The facility at Jaduguda is operational for more than four decades, whereas, the facility at Turamdih is operational for the last 6 years.

 MATERIALS AND METHODS



Study area

The study was conducted in Singhbhum region of Jharkhand state of Eastern India. Singhbhum is one of the most well-known mineral abundant zones in the country, and extensive mineral exploration has been carried out in this zone since a long time. [1] Uranium and copper deposits of economically viable grades are mined and processed in this region since decades. The Singhbhum copper-uranium belt in eastern India contains the largest amount of copper ore and uranium in the country. [2] The oldest uranium mines and ore processing unit of the country is situated at Jaduguda. Over the years, the operations of uranium mining and processing have diversified and at present there are six developed uranium mines with two centralized ore processing units. Mined uranium ore of Jaduguda, Narwapahar and Bhatin situated within a distance of 12 km is processed at centralized ore-processing unit at Jaduguda. Ore from Banduhurang and Turamdih mines is processed at ore processing unit of Turamdih. The processed fine component of waste of the uranium industry containing the entire set of uranium series radionuclide is discharged in an engineered impoundment system called tailings pond. [3] Tailings pond is designed to hold practically the entire amount of fine tailings generated during the processing of uranium ore.

Design features of Jaduguda and Turamdih tailings pond are different in their mode of construction. The design feature is to provide structural stability of the earthen bund during extreme natural calamities such as heavy rain and seismic events. At Jaduguda, the tailings pond is in a valley with natural hill on three sides and an earthen bund forming the fourth side. At the construction stage, the impermeable materials were used to restrict the migration of radionuclides into the adjoining groundwater table. Neutral fine slurry is allowed to settle, and the liquid is decanted through a set of decantation well. Through gravity, the decanted effluent is transferred in open concrete channel at effluent treatment plant (ETP) for removal of dissolved uranium, radium and heavy metals. [4],[5]

Turamdih tailings pond is located between two hills running almost parallel toward the south side of the process plant. The area is a sloping valley. The discharged fine tailings slurry like Jaduguda is allowed to settle, and liquid effluent is collected in decant water ponds at the downstream side. In the downstream side of the tailings pond (western side), a decant water pond is built for the storage and pumping the decanted water to ETP. A check dam is provided alongside the decant water pond to account the natural extreme events. To minimize the ingress of surface rainwater runoff from the hill side catchment area into tailings pond, garland drain along with the service road has been provided around tailings pond, which leads to the natural surface drain. [6] The decanted effluent is treated at ETP of Turamdih.

Sample collection and processing

Groundwater samples were collected from villages around tailings pond at Jaduguda and Turamdih. Due to the three side limitation of hill, only one side of the tailings is the villages in the proximity of tailings pond at Jaduguda. However, some of the villages are on the other side of the hill. A streamlet is adjoining the tailings pond at Jaduguda, which gets dry during the summer season [Figure 1]. Groundwater sources are mostly dug well, or tube well used for the purpose of drinking. The use of the source depends on the requirement; the well is mostly confined to be used for one or two families, whereas, tube well are used as public drinking water source. The well water is also used for irrigation and gardening purpose. The uses pattern of groundwater is by and large identical at both the sites. The Turamdih tailings pond is bit away from the adjoining villages. At either site, some of the villages are in the foothill adjoining the tailings pond. Samples were collected from adjoining sources around tailings pond, filtered using 0.45 μm and preserved using dilute nitric acid.{Figure 1}

Analyses

Known volume of the sample was evaporated to near dryness with final fuming by addition of few drops of concentrated sulfuric acid. The evaporated samples were refluxed with 0.25 N H 2 SO 4 and subjected to solvent extraction using alamine (2%) in benzene solvent and aqueous: Organic ratio of 2:1. The organic layer was transferred into platinum planchet and analyzed using fluorimetric techniques. [7],[8] Along with the samples, National Institute of Standards and Technology standards were also processed in an identical manner. Chemically separated uranium is transferred to platinum disc, fused with fusion mixture NaF-Na 2 CO 3 (1:7) and subjected to ultraviolet (UV) radiation (3,650 Å) to measure the fluorescence intensity at 5546 ÅÅ specific to uranium. The uranium content of the original sample was obtained from fluorimetric reading of standard, sample and blank by further applying the sampling parameters. Minimum detectable concentration of uranium using UV-fluorimeter method works out to be 0.5 μg/L at 95% confidence level.

Data analysis

The dataset was statistically analyzed using Microsoft for Microsoft Excel, Math Works Natick, Massachusetts, U.S.A. 2008 software package. The data distribution was based on the statistical test for null hypothesis (h = 0). To ascertain the normality three tests such as Kolmogorov-Smirnov (KS), Jarque-Bera and Lilliefors test were attempted. The relevant parameters such as mean, median, standard deviation, geometric mean (GM) and geometric standard deviation (GSD) were evaluated for the dataset after estimating the distribution behavior of the data. The treatment of censored data is based on ranking the data and plotting the probability value of the ranked data. [9]

 RESULTS AND DISCUSSION



Total, 90 samples were collected from groundwater samples around Jaduguda during the year 1996-2008. Similarly, total 72 samples were collected around tailings pond at Turamdih during the year 2007-2012. Frequency distribution plot of uranium natural distribution around Jaduguda is presented in [Figure 2] and [Figure 3]. In the case of Jaduguda 33% of the analytical results were censored, whereas, in the case of Turamdih, 28% of the results were censored (<0.5 mg/m 3 ). The probability plot based on ranked data for Jaduguda and Turamdih are presented in [Figure 4] and [Figure 5]. The ranking method is used for the unbiased estimation of median concentration to nullify the effect of individual data below the limit of detection. [9]{Figure 2}{Figure 3}{Figure 4}{Figure 5}

Different trend lines such as exponential, power, logarithmic, polynomial were drawn out of which the logarithmic relationship between uranium concentration around tailings pond at Jaduguda and cumulative probability was ascertained based on the coefficient of determination (R2 = 0.97). The median concentration, worked out around tailings management facility at Jaduguda from the regression equation, was 1.03 mg/m 3 , which is slightly less than the median concentration of 1.1 mg/m 3 obtained mathematically with a maximum concentration of 10.86 mg/m 3 . The mean, standard deviation, skewness and kurtosis values of 2 mg/m 3 , 2.17, 2.2 and 4.98 and wide variation between mean, median and mode for Jaduguda data reveal that the distribution is not normal. The median, error around the median, first and third quartile, rest of the data and outliers for Jaduguda region are presented in the box plot [Figure 6].{Figure 6}

As evident from the boxplot, there is high degree asymmetry in the dataset around Jaduguda. Barring the censored data (minimum detection limit values) the dataset can be represented by lognormal distribution as evident from KS density plot [Figure 7], Jarque-Bera and Lilliefors test. The output of the Jarque-Bera test is h = 0, P = 0.22, j = 2.12, c = 5.13 and Lillietest is h = 0, P = 0.38, l = 0.082, c = 0.11 for log transformed data barring the censored value. GM can also be considered as an estimator of the parameter based on the property of the distribution. The GM for the original data worked out to be 1.25 mg/m 3 with GSD of 2.45. The 95% confidence interval (CI) of the data (2.5 th percentile and 97.5 th percentile) can be computed to be 0.5 and 8.73 mg/m 3 . These values are far less than the drinking water standard of 60 mg/m 3 prescribed in India. Similarly, the median concentration worked out around tailings management facility at Turamdih from the regression equation was 0.92 mg/m 3 , which is slightly less than the median concentration of 0.95 mg/m 3 obtained mathematically with a maximum concentration of 16 mg/m 3 . Though the highest uranium concentration of 22 mg/m 3 was also found in a tube well sample of Turamdih, it was not included in the computation of statistical parameter since the source is hardly used by the local residents. While estimating the distribution, it has been found that the distribution is highly asymmetrical with skewness of 1.9. The distribution is a mixture of two lognormal distributions as evident from the KS density plot [Figure 8]. Accordingly the maximum likely hood estimate along with 95% CI based on lognormal assumption is computed. Two likely hood uranium concentrations was ascertained clustered around 1.4 and 3.2 mg/m 3 with 95% CI of 1.05, 1.81 and 2.7, 4.1 mg/m 3 .{Figure 7}{Figure 8}

The nature of uranium mineralization at the two sites are entirely different. Turamdih tailings pond is in the vicinity of uranium mineralized hill and some of the groundwater sources are on the foot hill of the uranium deposit, whereas, a geological fault is passing close to the tailings pond at Jaduguda. Most of the groundwater sources are probably on one side of the fault line. The variation in monitoring results reflects the nature of uranium mineralization at the two tailings disposal sites. The results show a high degree of asymmetric around tailings pond at Turamdih attributed to the variation in geological characteristics. The median concentration is well below the median concentration of uranium in the pretreated tailings effluent which is typically 7-176 mg/m 3 around Turamdih with a median concentration of 23 mg/m 3 and 10-1,084 mg/m 3 with a median of 37 mg/m 3 . At both the tailings disposal sites, the impact of discharges on increasing the uranium concentration in groundwater has not been observed in the adjoining groundwater sources. One-way ANOVA computed for uranium natural variation between the years around tailings pond at Jaduguda reveal that the variation is statistically insignificant with F = 1.72; Fcritical = 1.94 and P = 0.09 [Table 1]. The levels are reflecting the natural distribution only, and the design feature of both the tailings impoundment facility is successfully able to retain the tailings within the pile.{Table 1}

Global distribution also reveals wide difference in the level of uranium in groundwater due to the difference in lithology, geomorphology and other geological conditions. As low as 0.9 ng/L mean concentration in portable water was reported in five Japanese cities. [10] A mean uranium concentration of 2.55 mg/m 3 was reported in drinking water from 978 sites in USA during eighties. [11],[12] Concentration as high as 700 mg/m 3 was found in private supplies of Canada. [13],[14] Groundwater in California has been found to contain uranium at concentrations as high as 135.6 mg/m 3 and 30% of wells tested in a recent study had concentrations >35 mg/m 3 . [15] Agricultural drainage waters in California's San Joaquin Valley have particularly high uranium concentrations with values as high as 22,300 mg/m 3 . Concentrated deposits of uranium in the environment occur in uraninite, U (IV) O 2 (s), ore bodies, and may be generated in the future at geologic repositories.

During the weathering of uraninite, a series of secondary minerals including uranium (VI) oxyhydroxides, phosphates, silicates, sulfates, and carbonates is precipitated. [16] Uranium in the +VI oxidation state is relatively soluble and can be detected in almost any natural water. Uranium is most concentrated in sedimentary rocks, particularly organic shales, and is also found in significant amounts in metamorphic and igneous rocks, with higher concentrations in granites than in basalts. [17] At both sites of the study area, the principal mineral deposit is uraninite. In Jaduguda region, the deposit is mostly underground, whereas, at Turamdih-Banduhurang region, both underground and near surface deposits of uranium is found.

The weathering process is more active near the surface deposits and accordingly the uranium distribution pattern in the groundwater may fluctuate. Apart from this, seasonal variation is also expected. In an attempt to correlate some of the important parameters such as pH, SO 4 , Cl and total hardness with uranium concentration in groundwater samples around Jaduguda tailings pond, it has been found that there is a highly significant positive correlation between uranium concentration and the anions [Table 2]. Unlike anions, pH is not correlated with uranium concentration in groundwater samples collected from areas around tailings pond at Jaduguda. Such insignificant correlation can be explained by narrow fluctuation in pH (nearly neutral) in different seasons or at different locations with respect to tailings pond. Variation in solubility conditions within such narrow range in natural condition is difficult to ascertain. Present study was however confined near the waste depository of uranium process industry to observe its role in enhancing the level of uranium in adjoining groundwater as compared to the natural background.{Table 2}

The results reflect the natural distribution of uranium around the facility and contribution of tailings pond was not found in groundwater sources adjoining Jaduguda and Turamdih facilities after 50 and 7 years of operation. The median concentration of uranium approximately 1 mg/m 3 in groundwater around both the tailings pond are far below the drinking water concentration (DWC) standard of 60 mg/m 3 prescribed in India.

 CONCLUSIONS



The results of uranium analyses in groundwater samples collected around two uranium mill tailings pond of Singhbhum, Jharkhand reveal that the distribution of uranium is function of lithology, geomorphology and other geological conditions. Despite more than four decades of continuous discharges on tailings pond at Jaduguda, the levels are comparable to the area background. Similarly, around Turamdih tailings pond also, the impact of discharges on enhancing the uranium level in groundwater has not been observed. The median concentration of uranium around tailings pond at either site is substantially lower than the DWC limit of 60 mg/m 3 recommended in India.

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