F1000Research F1000Research 2046-1402 F1000 Research Limited London, UK 10.12688/f1000research.178758.1 Research Article Articles Analysis of the radionuclides and heavy metals concentrations of the Vaal River, South Africa.

[version 1; peer review: awaiting peer review]

 Chobeka Boitshekwane Conceptualization Data Curation Formal Analysis Investigation Methodology Project Administration Resources Validation Visualization Writing – Original Draft Preparation Writing – Review & Editing https://orcid.org/0000-0003-2010-0423 1 Mathuthu Manny Supervision Validation Writing – Review & Editing a 1 Atsile Ocwelwang Supervision Validation Writing – Review & Editing b 2 Centre for Applied Radiation Science and Technology, North West University, Mmabatho, 2745, South Africa Centre for Nuclear Safety and Security, National Nuclear Regulator, Centurion, 7106, South Africa manny.mathuthu@nwu.ac.za AOcwelwang@nnr.co.za

No competing interests were disclosed.

 16 6 2026 2026 15 950 22 4 2026 Copyright: © 2026 Chobeka B et al. 2026 This is an open access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background

This study was conducted to examine the radionuclide and heavy metal concentrations in the water upstream and downstream of the Vaal River.

 Methods

The study used the ICP-MS to determine radionuclides and heavy metals. A total of 27 water samples were collected were collected for analysis. The analysis was mainly for Li, B, Pb, Cu, Co, Ni, Zn, Mn, Fe, and P radionuclides, such as K, Th, and U, using ICP-MS.

 Results

The carcinogenic human health risk values (mg/l) of heavy metals were estimated using the USEPA 2011 guidelines. The chronic daily intake (CDI), hazard quotient (HQ), and hazard index (HI) due to the ingestion of river water were calculated from the adopted USEPA 2011 guidelines. The risk values were estimated for an adult at 70 years of age with a body weight of 70 kg and a child at 15 years of age with a body weight of 15 kg. CDI in mg/kg/day had high concentrations of Cu at 9, 33E+02, B, P, and Zn at a constant concentration of 5, 60E+02. The calculated risk value was greater than 1 because of the carcinogenic risk of cancer.

K, Th, and U in Bq/l were also analyzed using ICP-MS. Radium equivalent activity (and) dose rate.

(D), annual effective dose (AEDE), external hazard (Hex), and internal hazard (Hin) indices were used to determine potential radiological risks. The calculated average radiation hazard for Raeq was (33,803 Bq/l), D (18,158 nGy/h), AEDE (0, 0222 nGy/hr), Hex (0,091) and Hin (0,096) in this study. These hazard parameters were lower than the world average permissible limit, and as a result, the hazard parameters did not pose radiological risks due to the ingestion of river water.

 Conclusions

According to the calculated Raeq, D, AEDE, Hex, and Hin index hazard parameters used for river water analysis, this study does not pose radiological risks to humans. The heavy metal concentrations in this study also proved that the Vaal River is not safe for public use. This is a result of the high concentrations of heavy metals in water across all elements. Therefore, additional river monitoring is required to maintain public safety.

 Vaal River ICP-MS Radionuclides Heavy metals Water. Faculty of Natural and Agricultural Science North West University The author(s) declared that no grants were involved in supporting this work. Introduction

The issue of river water pollution due to various anthropogenic activities in South Africa is of major concern ( Claassens et al., 2016; Zhou et al., 2020). Water pollution refers to the contamination of water bodies, such as rivers or lakes, by human activity, which has a negative impact on water users ( Ajibade et al., 2021). Toxins from sewage discharge, industrial operations, mining, agriculture, and urban or storm-water runoff interact with water bodies to cause contamination ( Zhou et al., 2020; Khan et al., 2022). When humans use contaminated water for various activities such as drinking or irrigation, it can cause ecosystem destruction and spread water-borne diseases ( Zhou et al., 2020; Moloi et al., 2020; Mokarram et al., 2020; Mararakanye et al., 2022). The more polluted the water bodies, the worse the water quality becomes ( du Plessis, 2021). According to numerous studies, the main causes of poor water quality in South Africa are mining, urbanization, and other anthropogenic causes ( Durand, 2012; Manyatshe et al., 2017; van Rensburg et al., 2016; Winde et al., 2017).

South Africa has many aspects of water challenges that can affect its economic growth, especially when the levels of water scarcity, droughts, and increasing and deteriorating water resources are not well addressed ( Plessl et al., 2019; van Rensburg et al., 2016; Wepener et al., 2011). Potable water is essential for life. Therefore, it is important to ensure that its quality is maintained through careful monitoring activities ( du Plessis, 2021).

South Africa is known for its mining industry, which plays an important economic role ( Winde et al., 2017; Worlanyo and Jiangfeng, 2021). South Africa is also considered to be the largest gold producer ( Winde and de Villiers, 2002). The Gauteng province within the Witwatersrand Basin of South Africa has more uranium than gold, which was mined as a byproduct. The mining of uranium within the Gauteng province is mainly on the outskirts of Johannesburg near Randfontein and west of Witwatersrand ( Winde and de Villiers, 2002). Uranium waste recovered from gold mining operations was deposited in Witwatersrand mud dams. Over the years, waste piles have grown and have intensified radionuclides in the environment ( Winde et al., 2017; Worlanyo and Jiangfeng, 2021).

According to Du Plessis (2021), the sustainability of South Africa’s freshwater resources is critical. South African water bodies require attention and status to ensure that the quality of water is at the desired state for users ( Makubalo and Diamond, 2020). Within Gauteng and North - West Province of South Africa, the deterioration of rivers due to mining activities is noticeable ( Durand, 2012). Mines are allegedly the major environmental sources of radionuclides and heavy metals ( Durand, 2012; Manyatshe et al., 2017; van Rensburg et al., 2016, Winde et al., 2017).

The radionuclides and heavy metals are normally released during surface mining operations ( Manyatshe et al., 2017; van Rensburg et al., 2016; Winde et al., 2017). They are found everywhere in the environment and can accumulate easily in soil and water ( Manyatshe et al., 2017; van Rensburg et al., 2016; Winde et al., 2017). The activity concentrations of radioactive materials and heavy metals produced during mining processes can pose serious risks to people and the environment when exposed to persistent levels ( Groffen et al., 2018; Marara and Palamuleni, 2019; Moloi et al., 2020).

Furthermore, mines are considered liable for a series of environmental issues and human health problems ( Plessl et al., 2019; van Rensburg et al., 2016; Wepener et al., 2011) and can potentially cause severe risks to the environment and people ( Plessl et al., 2019; van Rensburg et al., 2016). Some of these risks may cause damage to water bodies, biodiversity loss, and lifestyle changes as well as affect food security and potentially cause pollution ( Plessl et al., 2019; van Rensburg et al., 2016). These risks can be due to the decay series of long-lived natural uranium (U) and thorium (Th) ( Madzunya et al., 2020). The radionuclides can enter into the environment and cause various health effects when ingested or inhaled in high concentrations resulting in sicknesses such as cancer and eye problems ( Davies and Mundalamo, 2010).

According to Durand (2012), the Gauteng and North - West mine effluents contain thorium, uranium, radium, and polonium, which are considered radioactive. These pollutants accumulate in river sediments and soil, posing a severe threat to the water, environment, and people ( Durand, 2012). The presence of toxic pollutants tends to affect people through ingestion, inhalation, and absorption ( Davies and Mundalamo, 2010). Exposure to these pollutants may cause damage to the kidneys, blindness, paralysis, cancer, tissue diseases, and changes in the immune system ( Durand, 2012; Jibiri and Okeyode, 2012; Moloi et al., 2020).

The permissible limit of uranium in drinking water is 30 mg/l as to the recommendations of the World Health Organization (WHO) ( Burritt and Christ, 2018). The level is based on epidemiological studies of consumption of 2 litres of drinking water by a 70 kg adult per day, with 80% tolerable daily intake ( Ma et al., 2020).

 Problem statement

The Vaal River provides potable water to various industries in the Gauteng, North - West, Northern Cape, Free State, and Mpumalanga provinces of South Africa ( Davies and Mundalamo, 2010; Durand, 2012; Manyatshe et al., 2017). However, these industries tend to discharge polluted water back into the river system and affect the state of the river economically, environmentally, and ecologically ( Atangana and Oberholster, 2021; Marara and Palamuleni, 2019; Moloi et al., 2020).

The river flows through gold mines and is potentially contaminated with substantial amounts of radionuclides, heavy metals, and other toxic chemicals ( Manyatshe et al., 2017). Furthermore, the Vaal River is argued to be a dumping site for radiotoxic and heavy metals from various industries, including mining. The state of the river showed no signs of improvement ( Chokwe and Okonkwo, 2019; Wepener et al., 2011). At this rate, the continued pollution of the river will potentially have serious impacts on human health, food production, and the environment ( Chokwe and Okonkwo, 2019; Plessl et al., 2019; van Rensburg et al., 2016.

Numerous studies have been conducted on the Vaal River water system and its pressing problems ( Ajibade et al., 2021; Chokwe and Okonkwo, 2019; Claassens et al., 2016; Davies and Mundalamo, 2010). There are reports and guidelines regarding pollution of the Vaal River; however, progress has not been made in addressing issues related to river pollution of the river ( du Plessis, 2021 and van Rensburg et al., 2016). Furthermore, few studies on radionuclides and heavy metals in the Vaal River have been conducted. Recent studies conducted around the Vaal River have focused on the radioactivity levels and dosages of mine dam tailings and the exposure of people to ( Moshupya et al., 2022; Zupunski et al., 2023). The Vaal River challenges were not addressed in terms of satisfaction. The state of the river showed no signs of improvement ( Chokwe and Okonkwo, 2019; Wepener et al., 2011). At this rate, the continued pollution of the river will potentially have serious impacts on human health, food production, and the environment ( Chokwe and Okonkwo, 2019; Plessl et al., 2019; van Rensburg et al., 2016.

The study area was selected based on several pollution concerns from various studies on the Vaal River ( Chokwe et al., 2017; Moloi et al., 2020). This study is based on rivers as a possible pathway for heavy metals and radionuclides. The intention of this study is to assess the water quality of rivers for future reference. This study considers possible angles that may contribute to river water pollution, which affects the water quality of the river, and proposes a conceptual management model for the Vaal River.

Furthermore, it is important to note that many South African gold mines extracting ore contain not only gold but also a substantial amount of uranium (U), which is inadvertently transported to the surface inadvertently ( Winde and de Villiers, 2002). The main problem with uranium mining is its widespread effects on the environment, such as increased levels of radiation, radioactive dust, and water-borne toxins ( Madzunya et al., 2020).

 Aim of the study

The intention of this assessment was to investigate the concentration levels of radionuclides and heavy metals in the water quality of the Vaal River.

 Objectives

The objectives of this study were to:

Determining the water quality of the Vaal River in terms of heavy metal pollutants using ICP-MS.

Evaluate the radiological health risk indices due to NORM.

Methods

This study was carried out within the Vaal River borders of the North - West, Gauteng, Free State, and Mpumalanga provinces of South Africa. The Vaal River is the longest river within South Africa borders ( Wepener et al., 2011). The river provides potable water to Gauteng and its neighboring provinces for various consumers and industries ( Manyatshe et al., 2017). Apart from Gauteng, the river provides water to North - West, Northern Cape, Free State, and Mpumalanga provinces. The focus of this study was primarily on accessible parts of the river, located in Gauteng, North - West, and some parts of the Free State. It is worth noting that the Vaal River is the primary water source for various anthropogenic activities such as mining, agriculture, and recreation in Gauteng and the North - West Province ( Manyatshe et al., 2017). The river flows through Gauteng and North - West provinces, including but not limited to Vanderbijlpark, Orkney, Potchefstroom, and Klerksdorp ( van Rensburg et al., 2016).

The Vaal River flows through the Northern Cape, Mpumalanga, Free State, Gauteng, and the North - West province, as shown in Figure 1 ( Weideman et al., 2020; Wepener et al., 2011). Water drawn from the upstream of the Vaal River was used to meet the industrial needs of Gauteng and the surrounding provinces ( Wepener et al., 2011). Other uses of the river for consumers and industries include coal mining, electricity generation, and urban use ( Davies and Mundalamo, 2010; du Plessis, 2021; Durand, 2012). Figure 1 shows the study area and its boundaries.

Study area. Data collection, preparation and analysis

Water samples were collected from various sampling points along the Vaal River. Samples were collected along riverbanks based on safety and accessibility. Sampling points were chosen based on their proximity to the river. The samples were collected in and around the Gauteng and North - West Provinces, with some samples collected within the borders of the Free State Province. Gauteng Province represents the upstream of the river, while North - West Province represents the lower stream. The collected samples were geolocated using a global-positioning system (GPS).

 Water sample preparation

Water samples were stored in 2-liter polyethene bottles. The bottles were filled into the brim with no gaps to prevent carbon dioxide from being trapped and dissolved in water, which could affect the chemistry. Water samples were preserved by adding 11 M HCI to the containers at a rate of 10 ml per liter. The samples were filtered using a filter paper and a Buchner funnel to remove all unnecessary particles. Water samples were filled into 5 ml plastic bottles and labelled for identification purposes.

 The analytic method used for sample analysis

The water samples were analyzed using inductively coupled plasma – mass spectrometry (ICP –MS) (Elmer NexION 2000). This method was used to measure the concentrations of heavy metals such as Li, B, Pb, Cu, Co, Ni, Zn, Mn, Fe, and P, as well as U, Th, and K in water. This method is highly effective for detecting different elements in environmental samples and computing the total number of elements of interest.

 Calculation of the activity concentration

This study adopted several equations to calculate the potential harm of toxic and harmful substances to humans over a given period. The USEPA (1989) and UNSCEAR (2000) guidelines were used to calculate human health risks.

The concentrations of heavy metals, U, Th, and K in Bq/l were obtained using ICP-MS operated under the total quant method. A 10 ml multi activity calibration standard (Perkin Elmer) with elements was used to validate the accuracy of the method. The analysis was performed in triplicate. Blanks and standards were employed to test the precision, accuracy, and reagent purity of the analytical procedures.

The activity concentration of all radioelements was converted into Bq/l using the following conversion factors (1–2) from the IAEA technical report No1363: 1 % of K = 313 Bq / l 1 ppm of U = 12.35 Bq / l 1 ppm of Th = 4.06 Bq / l

Radionuclide in water

Because radiological hazards are determined, the total activity concentration does not provide an exact indication of radiation hazards associated with materials. Raeq, D, AEDE, Hex, and Hin indices were calculated against the recommended limits by UNSCEAR 2000 of 370 Bq/l, 55 nGy/h and 1 mSvy-1 respectively.

Radium equivalent activity

Because of the inconsistent distribution of natural radionuclides in the soil samples, the actual activity concentration levels of K, U, and Th were evaluated using a common radiological index known as the radium equivalent activity (Raeq). It is the most used index for assessing radiation risk ( Gruber et al., 2009). Equation (4) shows the radium equivalent activity (Raeq). Raeq ( Bq / l ) = Au + 1.43 ATh + 0.07 7Ak

The concentrations of U, Th, and K in Bq/l are represented by Au, ATh, and Ak, respectively. The maximum acceptable radium equivalent activity for the public is 370 Bq/l, which corresponds to an effective dose of 1 mSv/y. The activity concentration limit recommended by UNSCEAR is 370 Bq/l ( UNSCEAR, 2000).

 Absorbed dose rate (D)

Radiation exposure due to radionuclides found in water is one of many parameters during the assessment of any radiological hazard. Connection between radioactivity concentrations of natural radionuclides and their exposure is the absorbed dose rate 1 m above the ground surface. The absorbed dose (D) was then measured of the amount of energy imparted per unit mass of irradiated material. Where Au, ATh, and Ak are the concentrations for U, Th, and K, respectively. The UNSCEAR recommends a dose limit of 55 nGy/h, as shown in the equation: (5) ( UNSCEAR, 2000). This equation was used to compute the absorbed dose rate using the average concentrations of U, Th, and K (Bq/l) in water samples. D ( nGy / hr ) = 0.462 AU + 0.604 ATh + 0.0417 AK

Annual effective dose equivalent

To quantify the radiological risk directly, the annual effective dose equivalent (AEDE) is determined from the D rate by using the conversion factor of 0.7 nGy/hr (the measurement for dose rate were converted from nSv/hr to nGy/hr), an outdoor occupancy factor of 0.2, and an exposure duration per year (8760/hr) as represented in equation (5) and (6). The total tissue-weighted equivalent dose administered to the body’s designated organs and tissues is known as the effective dosage. It is mostly used for regulatory purposes to show compliance with exposure dose limitations ( Moshupya et al., 2022). The dose limit recommended by UNSCEAR is 1 mSv/year ( UNSCEAR, 2000). AEDE = D ( nG . hr ) × 8760 × 0.7 × 0.2 Sv Gy × 10 − 6

The absorbed dose was quantified by using the annual effective dose equivalent. This dose is derived from outdoor terrestrial gamma radiation sources and is calculated using two factors: the outdoor occupancy factor and conversion coefficient from the dose in air to the effective dose. The annual effective dose equivalent was estimated using equation 7–8 in conjunction with UNSCEAR’s recommended limit of 1 mSv/year.

Equation 3–10 and 3–11 were used to calculate the external hazard indices (Hex) of exposure to natural radioactive elements and decay products. This was done to maintain the radiation exposure attributable to natural radionuclides in the samples at a maximum of 1 mSv/yr ( Almayahi et al., 2012). H ex = Au 370 + ATh 259 + AK 48100 H in = Au 158 + ATh 259 + AK 48100 External and internal hazard indices for drinking water were calculated in this study. According to ( Mathuthu et al., 2021) the external and internal hazard indices must be less than 1 mSv. y-1in order to maintain radiation hazard significance.

 Heavy metals in water

In this study, carcinogenic or non-carcinogenic health hazards due to the ingestion of river water were determined using the general exposure pathway equations adopted from (US EPA 1999), for the adult and child age groups ( Phalen, 1998). The levels of human exposure to heavy metals were calculated using Equation 9, chronic daily intake (CDI) (mg/kg-day) as follows: CDI = CW × IR ABSgi × EF × ED BW × AT Where CW (mg/L) is the heavy metal concentration in drinking water, IR (L/day) is the ingestion rate – 2.0 L/day used in this study, ABSgi (no unit) is the gastrointestinal absorption factor (0.001) used in this study ( Ismael et al., 2022), EF (days/years) is the exposure frequency (365 days/year) used in this study, and ED (years) is.

The exposure duration – 70 years lifetime (US EPA 1999); BW (kg) is the body weight of the exposed adult person (70 kg) used in this study as average, age-specific values (US EPA 1999), and AT (days/year) is the average time, a non-carcinogenic effect period of exposure that is pathway-specific, derived as ED × 365 days/year, that is, 25550 days/year used in this study ( USEPA, 1999).

The computed CDI of the heavy metals was used to calculate the hazard quotient (HQ), a non-carcinogenic health indicator risks quantity, from Equation 10: HQ = CDI RfD Where RfD (mg/kg/day) is the reference orally ingested dose adopted from the US EPA. An estimated HQ value less than 1 is within the acceptable level of non-carcinogenic risk, whereas an HQ value greater than 1 is considered an unacceptable risk with the potential to cause adverse health hazard impacts on humans ( US EPA 1989). The hazard Index (HI), a non-carcinogenic health risk parameter, is the sum of all the HQs of individual contaminants and provides the estimated values of all potential health risks ( Uugwanga and Kgabi, 2021). It is determined based on the US EPA guidelines using Equation 11: HI = ∑ k = 1 n HQ HM Where HQHM represents the individual heavy metal HQ being added. The computed HI values were compared to the standard values to ascertain the level or possibility of a non-carcinogenic health impact on humans. Hence, for HI values less than 1, there is no non-carcinogenic health risk, whereas for HI values greater than 1, for an exposed person, there are chances of non-carcinogenic health risk impact occurring ( Moghadam et al., 2024).

 Results and discussions

This study analyzed water samples from the Vaal River for radionuclides and heavy metals. The aim was to assess potential health risks to people. The risks were measured using the (Raeq), absorbed dose (D), annual effective dose equivalent (AEDE), external hazard (Hex) and internal hazard (Hin) indexes ( UNSCEAR, 2000). The heavy metal concentrations of Li, B, P, Ni, Se, Fe, Mn, Pb, Zn, and Co were also examined. Following the 2011 USEPA guidelines, the CDI, HQ, and HI of the Vaal River were measured using calculations adopted from US EPA guidelines. The risk values were estimated using an adult of 70 years at 70 kg body weight and a child of 15 years at 15 kg body weight. The results were compared with the world average permitted values. This was done to confirm that the concentrations adhered to global guidelines. Studies conducted in the Vaal area have also been used to investigate the evolution of pollution problems in the Vaal River.

The K, Th, and U in Bq/l from the ICP-MS technique were converted into activity concentrations, and the Raeq, D, AEDE, Hex, and Hin hazard parameters were used to determine human health risks. Correlation factors for ICP-MS were used to measure the radionuclides.

Findings on radionuclides and heavy metals

This study focused on radionuclides and heavy metals in the Vaal River, South Africa. The main point of interest was driven by curiosity about the pollution level of the river, water quality, and potential impacts on humans. The pollution levels and health hazards posed by radionuclides and heavy metals were assessed using various methods.

 Activity concentrations of radionuclides in water

Water samples collected along the Vaal River were analyzed for K, Th, and U using ICP-MS. The average, maximum, minimum, and standard deviations of the samples were calculated, as shown in Table 1. From the calculated concentrations of each sample, hazard parameters such as Raeg, D, AEDE, Hex, and Hin were calculated, as indicated in Table 1. The average radiation hazards of Raeg, D, AEDE, Hex, and Hin were 33,803 Bq/l, 18,158 nGy/h, 0, 0222 nGy/hr, 0,091 and 0,096 respectively. These hazard parameters pose no radiological risks to people owing to the ingestion of water. This is because of the lower concentrations when compared to the UNSCEAR limit of 370 Bg/l for Raeq, 55 nGy/h for D. 1 mSv/yr, and 1 ratio for Hex and Hin.

K, Th and U activities and the hazard indices.
K (Bq/l) Th (Bq/l) U (bq/l) Raeq (Bq/l D (nGy/hr) AEDE (nGy/hr) H ex H in
EM1 467.3 0.021 2.46 38.5 20.634 0.025 0.104 0.111
PB1 359.4 0.002 0.643 28.3 15.285 0.019 0.076 0.078
PB2 428.9 0.005 0.547 33.6 18.142 0.022 0.091 0.092
PB3 429.2 0.003 0.642 33.7 18.198 0.022 0.091 0.093
PB4 392.1 0.004 0.511 30.7 16.59 0.02 0.083 0.084
PB5 412.5 0.003 0.539 32.3 17.452 0.021 0.087 0.089
PB6 432.3 0.002 0.52 33.8 18.269 0.022 0.091 0.093
PB7 423.9 0.004 0.486 33.1 17.904 0.022 0.089 0.091
PB8 432.4 0.002 0.455 33.8 18.243 0.022 0.091 0.092
PB9 402.7 0.039 0.632 31.7 17.108 0.021 0.086 0.087
PB10 412.4 0.004 0.449 32.2 17.406 0.021 0.087 0.088
PB11 401.9 0.002 0.412 31.4 16.95 0.021 0.085 0.086
PB12 427.6 0.002 0.486 33.4 18.054 0.022 0.09 0.092
PB13 439.1 0.002 0.485 34.3 18.563 0.023 0.093 0.094
PB14 446.8 0.006 0.598 35.1 18.913 0.023 0.095 0.096
PB15 362.7 0.003 0.543 28.5 15.376 0.019 0.077 0.078
PB16 392.9 0.003 0.513 30.8 16.622 0.02 0.083 0.084
PV1 441.5 0.006 0.774 34.8 18.772 0.023 0.094 0.096
PV2 454.7 0.006 0.612 35.6 19.247 0.024 0.096 0.098
PV3 444.3 0.005 0.691 34.9 18.85 0.023 0.094 0.096
SD2 386.9 0.013 0.639 30.4 16.437 0.02 0.082 0.084
SD3 430.1 0.013 7.751 40.9 21.525 0.026 0.11 0.131
ST2 444.1 0.09 0.65 34.9 18.82 0.23 0.094 0.096
VW2 243.8 0.006 22.796 42.6 21.155 0.026 0.115 0.177
VW3 463.9 0.737 0.209 36.1 19.449 0.024 0.097 0.098
Av 414.928 ± 42.000 0.036 ± 0.005 1.802 ± 0.900 33.803 ± 2.500 18.158 ± 1.800 0.022 ± 0.002 0.091 ± 0.001 0.096 ± 0.010
Max 467.3 0.737 22.796 42.62 21.525 0.026 0.115 0.177
Min 243.774 0.002 0.209 28.319 15.285 0.019 0.076 0.078
Std 45.391 0.146 4.617 3.336 1.565 0.002 0.009 0.02

The average radiation hazards of Raeq, D, AEDE, Hex, and Hin were 33,803 ± 2,500 Bq/l, 18,158 ± 1.800 nGy/hr, 0,222 ± 0.002 nGy/hr, 0,091 ± 0.001 and 0,096 ± 0.010, respectively. These hazard parameters pose no radiological risks to people due to the ingestion of water. This is because of the lower concentrations when compared to the UNSCEAR limit of 370 Bg/l, 55 nGy/h, 1 mSv/yr, and ratio of 1 for Raeq, D, AEDE, Hex, and Hin, respectively, as shown in Table 2.

K, Th, U activities and UNSCEAR recommended limits.
River Water
K (Bq/l) Th (Bq/l) U (Bq/l) Raeq (Bq/l) D (nGy/yr) AEDE (mSv/yr) Hex Hin
Average 414.928 0.036 1.802 33.803 18.158 0.222 0.091 0.096
Max 467.259 0.737 22.796 42.62 21.525 0.026 0.0115 0.177
Min 243.774 0.002 0.209 28.319 15.285 0.019 0.076 0.078
Std 45.391 0.146 4.617 3.336 1.565 0.002 0.009 0.02
Recommended limits ( UNSCEAR, 2000 ) 370 55 1 1 1

Table 2 presents the average, maximum, minimum, and standard deviation of each K, Th, and U in Bq/l for the selected radionuclide analyzed using ICP-MS. According to the tabulated concentrations, all hazard parameters were below the limits recommended by the UNSCEAR 2000 guidelines. This proves that the sites where samples were collected pose no radiological risk to people as of 2023.

Correlation factors were used for the dose rate (D) against the annual effective dose (AEDE) and the radium equivalent (Raeq), as shown in Figure 2 and Figure 3, shows the correlation between D and AEDE. The results showed that the annual absorbed dose (D) was strongly correlated with both Raeq and AEDE.

Correlation Factor D and Raeq. Correlation Factor D and AEDE. Heavy metal concentrations in water

The sample sites in which the Vaal River upstream and downstream waters were collected and analyzed increased the concentrations of the elements in the river course. The concentration of the elements increased as the river flowed downstream, as shown in Figure 4.

Heavy metals in water. Study limitations and strengths

The sampling sites in this study were chosen based on accessibility and safety. The Vaal River is underrepresented because the results were based on the location where the samples were collected. The samples were also collected once during winter; therefore, other seasons were not represented. It is noteworthy that most of the samples were collected from the public bridge of the Vaal River, which is heavily utilized by the public; hence, the study’s findings are relevant. The benefit of collecting samples in public places is that they provide the necessary cautions for use. Moreover, samples were taken upstream of the Vaal River in a resort where people visit for entertainment and relaxation; therefore, the site’s potential dangers must be assessed for public safety. The downstream of the Vaal River, where samples were collected, is also of public use for accommodation; therefore, it is important for users to know of the potential dangers where possible.

 Conclusions

The study intended to investigate the concentration levels of the radioactive and heavy metals of the Vaal River, to evaluate the human health risks due to ingestion of water. The ICP-MS technique was used due to its lower interference, and quick multi-element analysis benefits for environmental samples.

The average radiation hazard of Raeq, D, AEDE, Hex and Hin comply with the safety limit of UNSCEAR. As a result, pose no radiological risks to humans. This is justified by using an adult of 70 years and a child of 15 years for a period of a year. This also implies that the sites where samples were collected have lower concentrations of radioactive materials.

In relation to the heavy metal concentration levels of the study, Mn and Fe presented higher concentration. These elements are known to be common and highly dissolved in water; however, higher concentrations could be due to the human activities of industrial and agricultural effluent. The HI of the study presented a ratio greater than 1, which implies a carcinogenic risk toward humans. The elevated concentrations are possibly due to the nearby mine effluent, especially taking into consideration that the river is situated near the mine. There is also the possibility of discharges from the local municipalities and agricultural run-off since the space is extensively used for various uses such as industrial and municipal activities.

Based on the findings of prior studies and this study, the site is not safe for public use until more investigation is carried out. As a result, additional monitoring and regulatory control measures are required to safeguard the safety of all residents in these areas.

Recommendations

More research is required to better understand the origins of contamination along the Vaal River. Surface, subterranean, erosion, run-off evaluation, and the development of pilot treatment methods such as covering mining waste with vegetation and introducing natural plants that might assist in limiting water pollution could all be examples of pollution interventions.

Sites along the Vaal River that were not included in this analysis can be investigated further for heavy metal and radioactive contamination. Membrane technology applications can be investigated, and the results can be used to address the difficulties of pollution in the Vaal River.

 Ethics

Ethical approval was not required.

 Data availability

The authors confirm that all data underlying the findings are fully available without restrictions.

Repository name: Analysis of the radionuclides and heavy metal concentrations of the Vaal River, South Africa. https://figshare.com/articles/figure/Vaal_River_study_area/31960716 (BOITSHEKWANE TRYPHINA C.)

The project contains the following underlying data:

Figure 1 (QGIS map: study area map showing the Vaal River and its boundaries).

Figure 2 (showing correlations between D and Raeq).

Figure 3 (Showing correlation between D and AEDE).

Figure 4 (concentrations of heavy metals in river water).

Table 1(K, Th and U activities as well as the hazard indices).

Table 2 (K, Th and U limits).

GPS coordinates (coordinates collected during sample collection).

License: CC BY 4.0.

Email: 20941250@mynwu.ac.za or btchobeka@gmail.com

Acknowledgements

Profound thanks go to my supervisor Prof. Manny Mathuthu and Co-Supervisor Dr. Atsile Ocwelwang, Center for Applied Science and Technology (CARST) Laboratory, North - West University (NWU), Faculty of Natural and Agricultural Science (FNAS), my peer students and colleagues for extended assistance, and my family for the support provided.

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