Issue
Radioprotection
Volume 56, Number 4, October - December 2021
Page(s) 309 - 318
DOI https://doi.org/10.1051/radiopro/2021015
Published online 17 June 2021

© SFRP, 2021

1 Introduction

Naturally occurring radionuclides are present at trace levels in all mineral material – including waste. Disposal of waste containing an enhanced concentration in natural radionuclides has only relatively recently been addressed in regulations: e.g. the International Atomic Energy Agency (IAEA) Basic Safety Standards (BSS) (IAEA, 2014) as well as European Basic Safety Standards (EU, 2013a) require Member States to identify practices involving Naturally Occurring Radioactive Material (NORM) and to assess the radiological risk of these activities, including their waste management. Several countries have developed regulatory schemes to insure a safe disposal of waste containing naturally occurring radionuclides with an activity concentration exceeding regulatory levels (also called NORM waste). This regulatory framework includes limits on activity concentration and total activity (Mora et al., 2016) which may be disposed onto landfills and record-keeping procedures insuring the traceability of NORM waste disposed onto landfills (Pepin et al., 2013).

In the past, nothing prevented these NORM waste to be disposed onto landfill without adequate management and the question of their potential impact on environmental compartments, especially groundwater, may occur. To investigate this risk, the Belgian Federal Agency for Nuclear Control (FANC), the Belgian radiation protection authority, has integrated into its radiological monitoring program a set of measurements that aim at screening the presence of natural radionuclides in leachate, waste water treatment plant (WWTP) discharge and groundwater of landfills – both landfills currently in operation and old dumpsites (or legacy landfills). Sampling and monitoring were organised in collaboration with environmental agencies in charge of landfills monitoring.

Landfill leachates contain a number of both organic and inorganic pollutants: a review of typical concentration of main contaminants in leachate may be found in Andreottola et al. (1990), Haarstad and Maehlum (2011) and Bietlot et al. (2017a). Landfills are complex (bio)chemical reactors and it is very difficult to predict the chemical composition of leachate: this depends on several factors, such as composition of the waste, relative humidity, pH (most metals being released under acidic conditions), redox potential and age of the landfill. Moreover some specific interactions between chemical components of the leachate and waste may enhance the solubility of some pollutants. For instance, fulvic and humic acid present in leachate are powerful complexing ligands and may play a role in long-term mobilization of heavy metals. Even when the activity concentration of natural radionuclides in the landfilled waste do not exceed background concentrations in soil, these traces of radionuclides may be mobilized due to the peculiar physical and chemical conditions within a landfill.

Landfilling of waste is an old practice, which has been poorly regulated in many European countries up to the 1980s. For instance, former quarries have commonly been used as dumpsite for waste disposal with few, if any, protection measures to mitigate the impact of this disposal on the environment. These old dumpsites had no bottom liner or leachate collection system to avoid penetration of the leachate in the surrounding groundwater. Many of these former dumpsites form nowadays a source of groundwater or surface water contamination; they request active remediation measures as well as a monitoring program to follow their environmental impact.

Groundwater contamination with natural radionuclides is well documented with a large amount of monitoring data around uranium mining and milling facilities (IAEA, 2005). Several studies have also investigated the environmental impact of sites where a specific type of NORM waste has been disposed, such as phosphogypsum stack (Rutherford et al., 1994; Sandhu et al., 2018; Guerrero et al., 2020). However, only scarce data are available on the level of natural radionuclides activity concentration in water compartment of landfills in general. The concentration of uranium in leachate of several Norwegian landfills was investigated in Øygard and Gjengedal (2009) and the authors concluded to the absence of an enhanced uranium concentration in these leachates compared to background levels. However, in 2007, some media articles in the Dutch press reported enhanced uranium concentration in the groundwater of some Dutch landfills (De Volkskrant, 2007) but unfortunately these results have not been published. Some studies (Haarstad and Maehlum, 2012; Gellerman, 2018) looked at the concentration of tritium (H-3) in discharge water, leachate and groundwater of landfills: while activity concentration up to 576 Bq/l in the discharge of a landfill was reported in Gellerman (2018), tritium in leachate and groundwater was only detected sporadically in Haarstad and Maehlum (2012).

The purpose of the present study is to fill this gap and to present a set of consolidated data on typical concentrations of natural radionuclides in leachate, discharge water and groundwater of landfills in Belgium. Sixteen currently in operation landfills for hazardous and non-hazardous waste have been investigated as well as 10 historical dumpsites for industrial and household waste. These data have been collected on a period of several years to verify the time-dependence of the measured concentrations.

As landfilling of NORM waste under controlled conditions is now becoming a widely accepted practice, these additional data on typical concentrations of natural radionuclides in leachate and discharge water of landfills may also be used in the context of monitoring the environmental impact of landfilling of NORM waste in order to discriminate impact of newly disposed NORM waste from historical impact.

2 Context of sampling and measurements

The measurements presented in this paper have been performed in the context of the radiological surveillance programme of FANC, the Belgian radiation protection and nuclear safety authority. This programme is described in Sombré and Lambotte (2004) and essentially focuses on the monitoring of nuclear facilities located in Belgium and near the Belgian border. It also monitors the impact of NORM industries and legacy sites in Belgium and a summary of the main results is yearly published in the annual surveillance report of FANC.

For landfills in operation, the Scientific Institute of the Walloon Region (ISSeP), working on behalf of the Walloon Administration, is in charge of assessing the environmental impact of landfills in Wallonia. In this framework, ISSeP performs periodical monitoring campaigns of these landfills (Bietlot et al., 2011, 2017a, 2017b). Several samples of leachates, waste water treatment plant discharge and groundwater which have been sampled by ISSeP have been further analysed by FANC. Some additional samples have been taken in the context of the compulsory self-monitoring undertaken by the operator of the landfills. The samples and analyses for landfills in operation cover a period from 2012 to 2019.

For old waste dumpsites, FANC collaborates with SPAQuE, an organisation in the Walloon Region of Belgium, that is in charge of investigation, remediation and surveillance of former industrial sites. SPAQuE monitors non-radioactive pollutants around several former municipal and industrial waste dumpsites. For this study, some piezometers around the investigated old dumpsites have also been sampled for analysis of radioactive parameters. Selection of the most relevant piezometers was done on basis of the degree of chemical contamination of the groundwater – contamination with radionuclides being expected to be associated with contamination with other heavy metals. The measurements cover a period from 2015 to 2020.

Frequency of sampling for radiological analyses has been variable: while a majority of investigated sites have been investigated only once, some of them have been sampled three or four times when a non-trivial value for some of the radionuclides had been detected.

For most samples, screening measurements of gross alpha and gross beta activities have been performed. Ra-226 has been measured for almost all samples and uranium for a majority of them. Other radionuclides such as Po-210, Ra-228, tritium and Cs-137 have been sporadically measured.

A volume of 2.5 litre was systematically sampled either with a peristaltic pump for groundwater or directly from taps in the water treatment plant for leachate and discharge water. An additional volume was sampled when Pb-210, Po-210 or Ra-228 had to be analysed.

The analyses have been performed by the Belgian laboratories contracted by FANC for the national radiological surveillance programme: IRE-Elit, SCK-CEN and Vivaqua. Samples treatment at the laboratory is based on ISO standard 5667-3 (ISO, 2018). Samples were first filtered and acidified. When analysis of H-3 was requested however, a 250 ml volume was sampled before acidification. When Pb-210 and Po-210 had to be analysed, a volume of 3 litre was isolated and acidified with HCl. One litre (resp. 2 litre) acidified sample was isolated for the analysis of Po-210 (resp. Pb-210). The rest of the sample was acidified to pH < 1.5 by adding 1 ml/L HNO3. After a second filtration, a volume of 250 ml was isolated for gross alpha and gross beta measurement, 500 ml for uranium and 250 ml for Ra-226 measurement.

Determination of uranium has been performed either through mass measurement with ICP-MS according to ISO standard 17294-2 (ISO, 2016) or through activity concentration determination of U-238 and U-234 with alpha spectrometry according to ISO standard 13166 (ISO, 2020a). Ra-226 was measured using Liquid Scintillation Counting (LSC) according to ISO 13165-1 (ISO, 2013) and Po-210 by alpha spectrometry according to ISO 13161 (ISO, 2020b).

3 Sites investigated

3.1 Landfills in operation

Operational landfills are classified according to the European Council Directive 99/31/EC (EU, 1999) as either landfill for hazardous waste, non-hazardous waste or inert waste. In this study, a total of 13 landfills for non-hazardous waste have been investigated. All of them are equipped with a leachate collection system in which leachates from different sections of the landfill can be collected separately. These sites mainly accept non-hazardous industrial waste. Measurements have been performed on leachate, groundwater and on the leachate treatment plant discharge. In two cases, the water of the creek in which the effluent of the leachate treatment plant is discharged has been measured too.

In addition, leachate and groundwater of 3 landfills for hazardous waste have also been investigated.

3.2 Former dumpsites

A total of 10 old waste dumpsites included in the monitoring network programme of SPAQuE have been investigated. They have generally been operated in the 1970–1980s and all of them are the source of groundwater pollution. A detailed inventory of the waste which was dumped on these sites is obviously not available but investigations by SPAQuE have shown that e.g. the following categories of waste had been disposed: industrial waste such as waste from metallurgical industries or foundries, hospital waste and household waste. Some of these dumpsites have been the subject of an extensive remediation with placement of an impermeable capping and, in some cases, pump-and-treat solutions for groundwater contamination. Some have not been remediated extensively but groundwater pollution is periodically monitored for all of them.

4 Results for leachate, discharge and surface water of landfills in operation

4.1 Leachates

A total of 71 samples of leachates have been analysed. Results for the leachates from landfills for non-hazardous and hazardous waste are displayed in Table 1.

Some leachates have been measured more than once: in these cases, an average value has first been calculated on the set of samples corresponding to the sampling station measured in successive years before averaging on all measurements. In the calculation of the average, when the measured value was below detection limit, half this detection limit was taken as representative value – as prescribed in the European directive 2009/90/EC (EC, 2009). Average and median values were calculated only when at least 5 results above the detection limit were available.

The median or average values for uranium concentration in leachate are similar to background values in Belgian groundwater. This result is in line with the results of Øygard and Gjengedal (2009) in which no significant increase of uranium concentration in leachate of Norwegian landfills had been observed. However, although a majority of results does not indicate significant values for uranium concentration, a few samples from landfills for non-hazardous waste show a concentration higher than 10 μg/l. Only one sample showed a uranium concentration above the World Health Organisation (WHO) recommendation of 30 μg/l for uranium in drinking-water (WHO, 2017).

The three landfills for hazardous waste which have been investigated do not show enhanced concentration of uranium in their leachate.

Table 2 shows the distribution of results for Ra-226. Here, the highest activity concentration has rather been observed in landfills for hazardous waste with a few samples showing a Ra-226 activity concentration exceeding the parameter value of 0.5 Bq/l for drinking water set in the European directive 2013/51/Euratom (EU, 2013b). Note that this reference to the parameter values for drinking water is made for the sake of comparison only – obviously, these values do not apply to leachates.

Although landfills for non-hazardous and hazardous waste seem to show different distributions for uranium and radium concentration in their leachate, the data set is too limited to draw any conclusion on a possible correlation between the category of waste disposed and these pattern of contamination in the leachate.

Among the other radionuclides measured, an enhanced value of Ra-228 activity concentration (1.22 Bq/l) had been measured in the leachate of one of the investigated landfills. The concentration of uranium in this leachate was also initially found to be significant with a value of 46 μg/l at the time of the first analysis.

The Ra-228 activity concentration and the uranium concentration in this specific leachate were measured again in the following years to study the temporal variation of these two concentrations. As shown in Figure 1, Ra-228 activity concentration decreased steadily, which may be explained by a combination of the radioactive decay of Ra-228, exhaustion of the source of Ra-228 in the waste and changes in chemical conditions of the leachate. A similar decrease was observed for uranium but an additional and more recent measurement showed an increase of the U concentration again. Here also, the evolution of chemical conditions within the leachate, which reflects various stages of degradation of the waste, may explain the observed temporal variation of uranium concentration.

Only few measurements have been performed to identify artificial radionuclides. One measurement indicated a presence of Cs-137 with an activity concentration of 2.3 Bq/l, which is probably related to the washing of the Cs-137 present in soil and some organic material. Tritium was also measured in the leachate of one of the landfills with an activity of maximum 40 Bq/l. Although this shows the possible presence of non-trivial values of H-3 in landfills leachates, these few measured values are below the results of Gellerman (2018) where H-3 activity concentration in discharge water of landfills up to a few hundreds of Bq/litre was observed. On the other hand, in Haarstad and Maehlum (2012), where the possibility to use tritium as tracer for leaking landfill leachate into groundwater had been investigated, no tritium had been observed above detection limit in the analysed leachates.

Table 1

Overview of measurements results on leachate samples – Landfills for non-hazardous and hazardous waste. Results are expressed in Bq/l, except U in μg/l.

Table 2

Distribution of Ra-226 activity concentration (in mBq/l) in leachates from landfills from hazardous and non-hazardous waste.

thumbnail Fig. 1

Variation of Ra-228 activity concentration and U concentration in a leachate of one of the investigated landfills.

4.2 Leachate treatment plant discharge, surface water and groundwater

The discharge water from the leachate treatment plant of 9 landfills for non-hazardous waste has been investigated. Overview of the results is displayed in Table 3.

As for leachates, a significant variation is found from one landfill to the other. Uranium is lower than in leachates but Ra-226 shows similar maximal and average values. The amount of salt, and consequently of K-40, may still be significant in some cases, which explains the high gross beta values in some samples.

For two landfills, the radiological quality of the discharge river has also been investigated. In both cases, these discharge rivers are creeks with a low debit. Radiological parameters (gross alpha and beta, K-40, uranium and Ra-226 activity concentration) have been measured both upstream and downstream of the discharge points. For one of these two landfills, the gross alpha activity of the river downstream was higher than upstream – related to a difference in uranium concentration. A second measurement had been performed three years later to confirm this first result. This is illustrated by Figure 2.

The difference in uranium concentration was still observed at the time of the second measurement (2017) but with a smaller magnitude. Uranium concentration in the leachate treatment plant discharge of that landfill was also measured in 2017 and was the highest (7.3 μg/l) of all measured values in discharge water. The slight increase of uranium concentration in the creek is thus clearly related to the discharge.

Other heavy metals have been measured in the discharge creek by ISSeP and most of them display a higher concentration downstream than upstream, especially arsenic. The K-40 activity concentration is also significantly higher downstream than upstream: this is correlated to the amount of chlorides, which concentration was about 5 times higher downstream than upstream.

Although these results show that the water discharge of the landfill may have a measurable impact on the radiological quality of the creek, there is no consequence from a health point of view: the uranium concentration remains largely below the WHO drinking water recommendation for uranium of 30 μg/l.

Similar measurements were performed for the discharge river of another landfill: in that case, no significant difference in radionuclide concentrations was found between up- and downstream – except a higher concentration in K-40 downwards (0.124 Bq/l for 0.04 Bq/l upstream) but of much smaller significance than in the previous case.

The impact of the discharge water from the leachate treatment plant on the radiological quality of the discharge river is thus variable. In the only occurrence where it has been observed, it was accompanied by a significant impact on chemical parameters, such as chloride, sulphate and some metal concentrations.

Regarding groundwater, the radiological measurements around landfills for non-hazardous and hazardous waste are displayed in Table 4.

All values are within the range of background values for groundwater measured in the national radiological surveillance program of Belgium. There is no visible impact of the landfills in operation on the radiological quality of the groundwater.

Table 3

Overview of measurements in discharge water from landfills for non-hazardous waste. Results are expressed in Bq/l, except U in μg/l.

thumbnail Fig. 2

U concentration (in μg/l) in a creek upstream and downstream the discharge point of one investigated landfill.

Table 4

Radiological measurements in groundwater around landfills for non-hazardous and hazardous waste. Results are expressed in Bq/l, except U in μg/l.

5 Groundwater around old waste dumpsites

The results for groundwater around the 10 investigated old dumpsites are displayed in Table 5. As for landfills in operation, minimal, maximal, average and median values of the analysed parameters are shown. Some of the wells have been measured more than once – during successive years; in this case, the average is first calculated on measurements made at the same sampling point over different years before averaging on different sampling points.

The values show a larger distribution than for groundwater around landfills in operation. In particular, uranium concentration displays some values which are clearly higher than normal background values in Belgian groundwater. Among the 10 investigated old dumpsites, 3 have an increased uranium concentration, above 10 μg/l, in their groundwater – with the highest value just above WHO recommendation for drinking water. These 3 sites have been investigated in more details. In particular, a systematic comparison between radiological parameters and some non-radioactive contaminants has been made – thanks to the results of chemical analyses provided by SPAQuE.

The first site is a former sand quarry which had been used as an authorized landfill between 1973 and 1983. After 1983, illegal dumping still took place until 1989. The dumpsite has been remediated in 2003 and has been under surveillance by SPAQuE since 1996. Figure 3 displays the uranium and Ra-226 concentration measured at five piezometers (P) that were localised along the flow of the groundwater. For comparison, cobalt and chlorides concentration are also displayed.

The peak of contamination is clearly in well P6 for both uranium and Ra-226. Among the chemical parameters, the same well P6 also shows a peak of concentration for Ba, Sr, Mg, Co and chloride. Arsenic is not present as contaminant. It should be mentioned that the uranium concentration in well P6 has been measured for three consecutive years and appears to remain stable around 15 μg/l.

A similar pattern of contamination was observed around a second dumpsite. This second site was initially a sand quarry in the 1960s. Upon the end of sand extraction in 1971, the site was used as a waste dump for local industries and for household waste for inhabitants of the area. The waste dump was closed in 1987 and the waste covered with a layer of ground. Figure 4 shows the concentration of uranium, Ra-226, cobalt and chlorides in the wells W SA, W S3b and W S4 which are located in a sand aquifer upstream and downstream from the site but all very close from the waste deposits. Here, the uranium concentration in the most contaminated well (W S3b) was higher (32 μg/l) than in the previous site. As for the first one, one observes that the peak of contamination for uranium appeared in the same well as the peak of contamination for Ba, Sr, Co and chloride. In this case, arsenic is also present as a contaminant.

A third old dumpsite – again a former sand quarry – shows enhanced uranium concentration in the surrounding groundwater. Here the maximal uranium concentration amounts to 28 μg/l. Only one well had been measured for radioactive parameters and this higher value for uranium was also observed in a well showing higher values for chemical parameters, such as chlorides, Ba, Sr and Co.

While the enhanced uranium concentration observed in the groundwater of these three old dumpsites appears to be associated with an enhanced concentration of Ba, Sr, Co and chloride, there is no clear linear correlation between these concentrations. Table 6 gives the Pearson’s correlation coefficient between the uranium concentration and the concentrations of other investigated chemicals. Spearman’s rank correlation coefficients between the same sets of data were also calculated. In the calculation of these coefficients, we included the available values of concentrations from all 10 investigated dumpsites and not only from the three sites showing an enhanced uranium concentration. The data sets however remain too limited to draw meaningful conclusions on possible correlations.

The pollution of groundwater around these sites is due to the mixing of the leachate plume from the waste into the groundwater. Old dumpsites were of course not equipped with a leachate collection system and in many cases there was no impermeable layer under the waste deposit. Moreover, almost no measures were taken at that time to prevent penetration of rainwater into the waste mass. The level of uranium contamination in these groundwater samples around former dumpsites is similar to the highest values measured in leachates from landfills in operation (Sect. 4.1).

One may also note that the three aquifers for which an enhanced uranium concentration has been observed are all three sand aquifers.

Table 5

Radiological measurements in groundwater around old dumpsites. Results are expressed in Bq/l, except U in μg/l.

thumbnail Fig. 3

Concentration of uranium, cobalt (in μg/l) and chlorides (in mg/l) and activity concentration of Ra-226 (in mBq/l) in the successive piezometers (P) along the first landfill. Measurement uncertainties for Co and Cl− were not available.

thumbnail Fig. 4

Concentration of uranium, cobalt (in μg/l) and chlorides (in mg/l) and activity concentration of Ra-226 (in mBq/l) in the successive wells along the second landfill.

Table 6

Pearson’s correlation coefficient and Spearman’s rank correlation coefficient between the concentration of uranium and of some other metals, Ra-226, chloride and sulphate in the wells of the 10 investigated landfills.

6 Isotopic ratio of U-238 and U-234

It is well-known that the two uranium isotopes U-238 and U-234 are generally not in equilibrium in water samples. This is due to the alpha recoil which will favour the solubility of U-234 by disturbing the crystal matrix in which the uranium atom is trapped. Several works have investigated the possibility to use the isotopic ratio of these isotopes as a tracer for the origin of the uranium (Osmond and Cowart, 2000; Zielinski et al., 2000). A ratio higher than one is achieved on a larger time-scale and a ratio close to one is rather correlated to a contamination due to human activities. A common method of analysis is to plot the U-234/U-238 activity ratio against the uranium concentration or its reciprocal to identify mixing and aquifer water interactions (Osmond and Cowart, 2000).

In the present study, the activity concentration of U-238 and U-234 is not available for each sample, as uranium was determined through mass determination for many of the samples. When both isotopes have been determined separately, we plotted the U-234/U-238 isotopic ratio as a function of U-238 activity concentration. Figure 5 displays the isotopic ratio for leachate and discharge water of landfills in operation and Figure 6 for groundwater around landfills in operation and old dumpsites.

In both diagrams, small values of uranium concentration are associated with a large uncertainty for the isotopic ratios.

Isotopic ratio in leachate or discharge water seems to show a different trend compared to the ratio in groundwater. The ratio converges towards 1 for contaminated groundwater around old dumpsites, which seems to confirm the conclusions of Osmond and Cowart (2000) where an isotopic ratio close to one was considered as a tracer for anthropogenic contamination. For leachate, the isotopic ratio tends towards 1.5 for larger uranium concentration. This higher value of the isotopic ratio for the leachates remains unexplained but the extent of uncertainties requires carefulness in the interpretation of these results.

thumbnail Fig. 5

U-234/U-238 isotopic ratio in leachate (blue dots) and discharge or surface water (orange triangles) of operational landfills as a function of U-238 concentration (in Bq/l) in logarithmic scale.

thumbnail Fig. 6

U-234/U-238 isotopic ratio in groundwater of operational landfills (orange triangles) and old dumpsites (blue dots) as a function of U-238 concentration (in Bq/l) in logarithmic scale.

7 Discussion and conclusions

The main purpose of this study was to investigate the potential impact of naturally occurring radionuclides present in waste disposed onto ordinary landfills on the quality of the surrounding water. To this end, activity concentrations of several natural radionuclides in leachate, leachate treatment plant discharge and groundwater from a set of landfills in Belgium have been measured: 16 landfills in activity and 10 old dumpsites where significant pollution had been observed and which are currently still monitored. This set of data may serve as reference for typical values of natural radionuclides in the water of landfills not only for Belgium but also for other countries.

For landfills in operation, a few results show an enhanced concentration of uranium in the leachate – higher than 10 μg/l. Some increased values for Ra-226 and Ra-228 have also been measured and, among artificial radionuclides, Cs-137 was observed in some samples.

In one occurrence, the waste water discharge from the leachate treatment plant leads to a slight increase of the uranium concentration in a local creek.

Regarding groundwater, while none of the investigated landfills in activity showed an uranium concentration above 10 μg/l in the surrounding groundwater, almost 1 out of 3 investigated old dumpsites displays an uranium concentration above this value with a maximal concentration just above the WHO drinking-water recommendation for uranium of 30 μg/l. This is in line with the results regarding leachate: these old dumpsites were not equipped with a leachate collection system and consequently the leachate may have mixed directly with the local groundwater. Isotopic ratio of U-234 to U-238 had also been looked at and a value close to one for the contaminated groundwater tends to confirm the anthropogenic character of the presence of uranium.

The presence of uranium contamination in groundwater is systematically associated to the presence of other, non-radioactive, contaminants.

Landfills are complex chemical reactors and may constitute a field of investigation to study the influence of changing chemical conditions on mobilization of radionuclides, e.g. under influence of the different stages of waste mineralisation. Further work may focus on how these chemical conditions affect the behaviour of radionuclides in leachate and groundwater: e.g. the redox potential as it is well-known that uranium is redox sensitive – being less mobile in reducing conditions (USEPA, 1999). As for other contaminants, potential impact on water compartments from disposal of waste containing naturally occurring radionuclides is more influenced by the physico-chemical conditions of disposal than merely by the activity concentration in the waste.

Another item for further investigation is the speciation of uranium in leachate or in contaminated groundwater and its complexation with humic or fulvic acids. In leachate in particular, humic acid is known to be a factor influencing the complexation of heavy metals – enhancing therefore their mobility. Several studies (Lenhart et al., 2000; Wei et al., 2007) have looked at the complexation behaviour of humic acids with respect to uranium. In Lenhart et al. (2000), both humic and fulvic acids were demonstrated to strongly bind U(VI).

Finally, although the results presented here show some occurrences of an enhanced concentration of radionuclides in leachate and groundwater of landfills, the impact in term of public health and radiation protection can be considered as negligible as these concentrations almost never exceed drinking-water standards.

Acknowledgements

The authors are grateful to the laboratories, which performed the radiological analyses presented in this work: SCK-CEN, IRE Lab and VIVAQUA. We are also grateful to the sampling teams of SPAQuE and ISSeP for their field work.

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Cite this article as: Pepin S, Dehandschutter B, Claes J, Biermans G, Nootens S, Sombré L, Poffijn A, Escourrou C, Bietlot E, Loo M. 2021. Enhanced natural radioactivity in leachate and groundwater of Belgian landfills. Radioprotection 56(4): 309–318

All Tables

Table 1

Overview of measurements results on leachate samples – Landfills for non-hazardous and hazardous waste. Results are expressed in Bq/l, except U in μg/l.

Table 2

Distribution of Ra-226 activity concentration (in mBq/l) in leachates from landfills from hazardous and non-hazardous waste.

Table 3

Overview of measurements in discharge water from landfills for non-hazardous waste. Results are expressed in Bq/l, except U in μg/l.

Table 4

Radiological measurements in groundwater around landfills for non-hazardous and hazardous waste. Results are expressed in Bq/l, except U in μg/l.

Table 5

Radiological measurements in groundwater around old dumpsites. Results are expressed in Bq/l, except U in μg/l.

Table 6

Pearson’s correlation coefficient and Spearman’s rank correlation coefficient between the concentration of uranium and of some other metals, Ra-226, chloride and sulphate in the wells of the 10 investigated landfills.

All Figures

thumbnail Fig. 1

Variation of Ra-228 activity concentration and U concentration in a leachate of one of the investigated landfills.

In the text
thumbnail Fig. 2

U concentration (in μg/l) in a creek upstream and downstream the discharge point of one investigated landfill.

In the text
thumbnail Fig. 3

Concentration of uranium, cobalt (in μg/l) and chlorides (in mg/l) and activity concentration of Ra-226 (in mBq/l) in the successive piezometers (P) along the first landfill. Measurement uncertainties for Co and Cl− were not available.

In the text
thumbnail Fig. 4

Concentration of uranium, cobalt (in μg/l) and chlorides (in mg/l) and activity concentration of Ra-226 (in mBq/l) in the successive wells along the second landfill.

In the text
thumbnail Fig. 5

U-234/U-238 isotopic ratio in leachate (blue dots) and discharge or surface water (orange triangles) of operational landfills as a function of U-238 concentration (in Bq/l) in logarithmic scale.

In the text
thumbnail Fig. 6

U-234/U-238 isotopic ratio in groundwater of operational landfills (orange triangles) and old dumpsites (blue dots) as a function of U-238 concentration (in Bq/l) in logarithmic scale.

In the text

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