Pollution and health risk assessment of soil, water and vegetables from an ion-adsorption rare earth mining area in Ganzhou, China

Abstract

Rare earth elements (REEs) are increasingly recognized as significant environmental pollutants due to their environmental persistence, bioaccumulation, and chronic toxicity. This study assessed REEs pollution in soil, water, and vegetables in an ion-adsorption rare earth mining area in Ganzhou, and evaluated the associated health risks to the local population. Results indicated that the REEs content in soil ranged from 168.58 to 1915.68 mg/kg, with an average of 546.71 mg/kg, substantially surpassing the background level for Jiangxi Province (243.4 mg/kg) and the national average (197.3 mg/kg). Vegetables displayed an average REE content of 23.17 mg/kg in fresh weight, far exceeding the hygiene standard of 0.7 mg/kg. Water samples contained REEs at a concentration of 4.09 µg/L. The estimated daily intake (EDI) of REEs from vegetables exceeded the threshold for subclinical damage, posing potential health risks, particularly for children and adolescents. Further analysis of the adjusted average daily intake (ADI) suggested that while most vegetable consumption remains within safe threshold, the intake of REEs from high-risk vegetables such as pakchoi and radish should be limited.

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Pollution and health risk assessment of soil, water
and vegetables from an ion-adsorption rare earth
mining area in Ganzhou, China
Liye Zhu
Gannan Medical University
Jinyu Huang
Gannan Medical University
GongHua Hu
Gannan Medical University
Qi Wang
Gannan Medical University
Hui Huang
Gannan Medical University
Sihui Wang
Gannan Medical University
Chunmei Wu
Gannan Medical University
Ziyue Sun
Gannan Medical University
Yi Fang
Gannan Medical University
Ming Hao
Gannan Medical University
Liang Xiong
Gannan Medical University
Research Article
Keywords: Rare earth elements, Emerging pollutants, Health risk assessment
Posted Date: October 7th, 2024
DOI: https://doi.org/10.21203/rs.3.rs-4883640/v1

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License:   This work is licensed under a Creative Commons Attribution 4.0 International License. 
Read Full License
Additional Declarations: No competing interests reported.

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Abstract
Rare earth elements (REEs) are increasingly recognized as signicant environmental pollutants due to
their environmental persistence, bioaccumulation, and chronic toxicity. This study assessed REEs
pollution in soil, water, and vegetables in an ion-adsorption rare earth mining area in Ganzhou, and
evaluated the associated health risks to the local population. Results indicated that the REEs content in
soil ranged from 168.58 to 1915.68 mg/kg, with an average of 546.71 mg/kg, substantially surpassing
the background level for Jiangxi Province (243.4 mg/kg) and the national average (197.3 mg/kg).
Vegetables displayed an average REE content of 23.17 mg/kg in fresh weight, far exceeding the hygiene
standard of 0.7 mg/kg. Water samples contained REEs at a concentration of 4.09 µg/L. The estimated
daily intake (EDI) of REEs from vegetables exceeded the threshold for subclinical damage, posing
potential health risks, particularly for children and adolescents. Further analysis of the adjusted average
daily intake (ADI) suggested that while most vegetable consumption remains within safe threshold, the
intake of REEs from high-risk vegetables such as pakchoi and radish should be limited.
Introduction
Rare earth elements (REEs) consist of 17 elements, including 15 lanthanides—lanthanum (La), cerium
(Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu),
gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb),
and lutetium (Lu)—plus scandium (Sc) and yttrium (Y). Based on their atomic numbers and masses,
REEs are typically classied two groups known as light rare earth elements (LREEs: La, Ce, Pr, Nd, Pm,
Sm, and Eu) and heavy rare earth elements (HREEs: Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) (Ramos et al.,
2016; Arienzo et al., 2022). REEs are crucial in diverse elds such as military technology, articial
intelligence, metallurgy, and medicine due to their unique physicochemical properties (Chakhmouradian
& Wall, 2012). China holds approximately 23% of the global REEs reserves, with signicant contributions
from Ganzhou, Jiangxi Province, where one-thirds of the country's ion-absorbed REE resources are found
(Li et al., 2010). However, traditional mining methods such as pool, heap, and in-situ leaching have
caused severe environmental issues, including soil acidication, structural damage, and potential risks to
water and vegetation (Li & Wu, 2017; Li et al., 2020a; Nie et al., 2020).
Pollutants from REEs mining activities readily contaminate local soil and water systems, creating
ecological hazards. An ecological study in Dingnan County, Ganzhou, has demonstrated that tailing soils
contained REE concentrations ranging between 187 and 1148 mg/kg, with an average of 392 mg/kg.
Surface water near these mining sites revealed average REE concentrations of 7730 µg/L, while both
sediments and farmland soils far exceeded natural background levels, indicating notable environmental
contamination (Liu et al., 2019). Another study in the same county identied tailings with low organic
content and high REE concentrations, reaching up to 808.5 mg/kg (Zhao et al., 2019). Along the
Dongjiang River near Xunwu County, REE concentrations ranged from 0.18 to 87.7 mg/L, surpassing
background levels by up to 14,126 times (Wei et al., 2001). In Longnan County, Ganzhou, the average soil
REE concentration was 976.94 mg/kg, signicantly higher than both Jiangxi and national background

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levels (Jin et al., 2014). Moreover, this contamination extends beyond environmental media to
agricultural products. For instance, REEs measured in ten different crops from mining sites in Longnan
County ranged from 1.04 to 78.57 mg/kg, exceeding China's vegetable hygiene standard limit of 0.7
mg/kg (Jin et al., 2014). A study examining various food types from six Chinese provinces found that
some vegetables exceeded the safety limits for total REEs (Jiang et al., 2012). Such widespread
contamination underscores the urgent need for comprehensive studies on REEs transfer and ecological
risks, especially regarding their impact on human health (Li et al., 2013; Gwenzi et al., 2018; Arbalestrie et
al., 2022).
REEs can enter the human body through various exposure routes and accumulate in different tissues or
organs, posing a threat to human health. Prolonged exposure to REE dust in mining and processing
industries has been linked to pneumoconiosis development (Hirano & Suzuki, 1996; Censi et al., 2011).
As non-essential elements, excessive REE intake can lead to physiological and immune dysfunction (Yu
et al., 2007). Additionally, elevated REE levels have been also associated with severe health issues like
DNA damage and carcinogenesis (Bai et al., 2019; Gaman et al., 2021). Notably concerning is the
potential neurotoxic effect on children, where exposure could impair cognitive functions, such as
intelligence quotient (IQ) and memory (Li et al., 2020b; Wei et al., 2020). Animal studies further conrm
that REE exposure can negatively impact respiratory, cardiovascular, neurological, and reproductive
systems (Nakamura et al., 1997; Toya et al., 2010; Lin et al., 2017; Gao et al., 2022; Lee & Park, 2022;
Xiong et al., 2023).
The present research focuses on the environmental and health impacts of REEs in Northern Ganxian
District, Ganzhou, Jiangxi Province, and an area known for its ion-adsorption rare earth deposits. The
study aims to comprehensively assess REEs levels in soil, water and vegetables to understand how REEs
transfer from the environment to agricultural products and ultimately to human consumers. It also
examines variations in REE absorption by different vegetable types, essential for identifying crops that
pose higher consumption risks. Moreover, the study evaluates the potential health risks from ingesting
REEs through these environmental mediums. The ndings are expected to inform the development of
targeted environmental protection policies and health measures to mitigate the impact of REE
contamination on local population health.
Materials and methods
Study area and sample collection
This study was conducted in an ion-adsorption rare earth mining area within Jiangkou Town, northern
Ganxian District of Ganzhou City (115°7'33"~115°8'4"E longitude and 25°52'53"~25°53'22"N latitude). In
the study area, the soil, primarily composed of red soil, is characterized by a deep, loose structure with
poor corrosion resistance and limited water and fertilizer retention capabilities. These conditions are
conducive to the presence of rare earth.

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A total of 21 soil samples (0–20 cm depth), 19 vegetable samples and 15 water samples were collected
during October 2023 and April 2024 (Fig. 1). Soil samples were air-dried, cleared of gravel and organic
debris, and then passed through a 10-mesh nylon sieve. The samples were then ground in an agate
mortar, sieved through a 100-mesh nylon sieve, and analyzed. The soil pH, determined using a 1:2.5 soil-
to-water ratio, ranged from 3.94 to 6.14, averaging 4.52, indicating mild acidity. Vegetable samples were
washed three times with deionized water, oven-dried at 75°C until constant weight, ground, sieved
through a 100-mesh nylon sieve, and stored in polyester bottles at -20°C for later analysis. Water
samples were ltered through a 0.45 µm nylon membrane and stored at 4°C until further analysis.
Sample analysis
Samples were digested using a microwave digestion system (MARS 6, CEM, USA) with 0.500 g of each
sample treated with 8 mL of a 3:1 nitric and hydrochloric acid mixture. Vegetable samples received an
additional 2 mL of hydrogen peroxide. Following the acid-driven treatment, the solution was diluted to 10
mL in a volumetric ask using a 2% nitric acid solution, and then ltered through a 0.45 µm nylon
membrane before analysis.
The content of 16 REEs in the samples was determined by inductively coupled plasma mass
spectrometry (ICP-MS, NexION 350X, PerkinElmer, USA). Concentrations were expressed in milligrams
per kilogram dry weight for soil and wet weight for vegetables. Calibration used standard solutions
ranging from 0.1 to 20 µg/L (GNM-M160181-2013, National Nonferrous Metals and Electronic Materials
Analysis and Testing Center, China). In, Re, and Rh (GNM-M030025-2013) were used as internal
standards at a concentration of 25 µg/L to ensure analytical quality. The detection limits ranged from
0.0063 to 0.0611 µg/L, calculated as three times the standard deviation from eleven blank solutions
(Table S1). Each sample underwent duplicate analysis. Accuracy and precision were assessed using
national standard samples (soil GBW07565 and spinach GBW10015a, national certied reference
materials of China), with recovery rates from 89.45–116.77% (Table S1).
Geostatistical and REEs characteristic parameters analysis
Geochemical parameters provide insights into the enrichment, fractionation, and sources of REEs in
soils. The North America Shale Composite (NASC) normalization method is commonly applied to
minimize the zigzag patterns in REE distributions, a phenomenon attributed to the Oddo-Harkins rule.
This study specically examines Eu and Ce anomalies (denoted as δEu and δCe) to assess REE
geochemical behavior in soil, calculated using the equations (1) and (2):
δEu = EuN/(SmN×GdN)1/2 (1)
δCe = CeN/(LaN×PrN)1/2 (2)
where the subscript N indicates the NASC-normalized values of the measured concentrations of REEs.
Anomalies are classied as positive when values exceed 1.05 and negative when below 0.95 (Algeo &

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Maynard, 2004).
Additionally, to assess REE differentiation, ratios such as LREEs/HREEs, the NASC-normalized La/Sm
((La/Sm)N) and Gd/Yb ((Gd/Yb)N) were calculated. These ratios are dened as:
(La/Sm)N
(Gd/Yb)N
where "sample" represents the concentration of La, Sm, Gd and Yb in the studied soils, and the subscript
N represents the NASC-normalized values.
Pollution assessment of REEs in soil
The pollution status of the studied soil was assessed by the geo-accumulation index (
I
geo), using the
following Eq.(3):
= )] (3)
where
Ci
represents the concentration of a specic REE
i
in the soil;
Bi
denotes the background value for
that REE
i
in the soil of Jiangxi Province, China. The classication criteria of
I
geo is shown in Table S2.
Potential ecological risks of REEs in soil
Ecological risks from REEs were assessed using method developed by Hakanson (Hakanson, 1980),
which considers both individual and cumulative element risks. The equations involved are (4), (5) and
(6):
4
5
RI = Σ (6)
where and denote the contamination factor and ecological risk factor of element
i
in soil; C
i
is
the concentration of element
i
in soil; and refers to the pre-industrial background value and toxic
response factor of element
i
in soil, respectively. Risk classication is detailed in Table S2.
Health Risk Assessment for REEs
=Lasample/LaN
Smsample/SmN
=Gdsample/GdN
Ybsample/YbN
I
geo log2[Ci/(1.5Bi
Ci
f
=
Ci
/
Ci
b
Ei
r
=
Ci
f
∙
Ti
r
Ei
r
Ci
fEi
r
Ci
bTi
r

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The health risks assessment of REEs in vegetables for both children and adults near mining areas were
evaluated using the estimated daily intake (EDI) model proposed by the Environmental Protection
Agency of the United States (US EPA, 2000). This model calculates exposure doses based on the
following Eq.(7):
EDI= (7)
EDI (µg/kg/day) indicates the estimated daily intake of REE, where CREE represents the sum of REEs in
vegetable based on wet weight (mg/kg ww); CR is the vegetable consumption rate by different age
groups (%) (from the Fifth China Total Diet Study, FCTDS) (Wu et al., 2018), BW is the average body
weight of different age groups (%) (from FCTDS). The vegetable consumption rate for children is typically
estimated to be 57% of that of adults (US FDA, 2003).
To assess the long-term health risks of REEs from consuming vegetables and water, the average daily
intake (ADI) for children and adults was calculated as following Eq.(8):
ADI = (8)
where ADI is the average daily intake of REEs (mg/kg/day); C is the content of REEs in the sample
(mg/kg); GW is the daily intake (kg/day), the average daily intake of total vegetables is in 0.22 kg/day for
children and 0.85 kg/day for adults (from FCTDS), respectively, and the average daily intake of water is
1.1 L/day for children and 1.6 L/day adults (from the Chinese Dietary Guidelines)(Chinese Nutrition
Society. (2022)); EF is exposure frequency, which is 365 days/year for children and adults; ED refers to
exposure period, which is 6 years for children and 25 years for adults; BW is the bodyweight, which is 15
kg and 60 kg for children and adults, respectively; AT refers to the average time, which is 2190 days for
children and 9125 days for adults.
Statistical analysis
Statistical analyses were conducted to compare average results from various soil and vegetable
samples by using a one-way analysis of variance (ANOVA) followed by Scheffe's test for multiple
comparisons. Spearman correlation and principal component analysis were performed to explore the
relationships between soil and vegetable REEs. A signicance level of (
P
< 0.05) was applied for multiple
comparisons and analyses. Data analysis was carried out using SPSS software package version 14.0
(SPSS Inc., USA) and Excel 2010.
Results and discussion
REEs content in study soils
The total concentration of REEs (ΣREEs) in study soils ranged from 168.58 to 1915.68 mg/kg, with an
average of 546.71 mg/kg (Table S3), exceeding the natural background levels in Chinese soil (197.3
mg/kg) and Jiangxi soil (243.4 mg/kg) (Wang et al., 2022). The hierarchy of average concentrations for
individual REEs is as follows: Ce > Y > Nd > La > Sc > Gd > Pr > Sm > Dy > Er > Yb > Tb > Ho > Eu > Lu > Tm.
CREE*CR
BW
C× GW× EF× ED
BW× AT

Page 8/20
Notably, Ce, Y, Nd, and La collectively contributed over 80% of the total REE concentration, with Ce being
the most prevalent, ranging from 55.18 mg/kg to 458.31 mg/kg. The concentrations of HREEs varied
from 44.80 to 771.74 mg/kg with an average of 175.64 mg/kg, whereas LREEs ranged from 119.50 to
1068.59 mg/kg with an average of 348.61 mg/kg. Moreover, the Y was the most abundant HREE,
comprising 23.63% of total REEs, while the HREEs accounted for 32.13%, indicating typical of a Y-
enriched ion-adsorption rare earth deposit.
Distribution characteristics of REEs in study soils
The distribution of REEs in the study soils was characterized by the ratios of LREE/HREE, NASC-
normalized La/Sm and Gd/Yb, along with the anomalies of Ce and Eu (Table1). The ratios of
LREE/HREE, ranging from 1.02 to 7.10 with an average of 2.94, suggest a higher content of LREEs
relative to HREEs. However, these ratios are signicantly lower than those in northern China, indicating a
comparative enrichment of HREEs in the study area (Liang et al., 2014). The slope of LREE and HREE
concentration curves can be reected by normalized (La/Sm)N and (Gd/Yb)N ratios, respectively
(Schilling & Winchester, 1966). In this study, the (Gd/Yb)N ratio of 3.15 points to a high degree of internal
fractionation of HREEs compared to LREEs, which had a (La/Sm)N ratio of 1.16. This aligns with the
broader distribution pattern of "light north, heavy south" across China.
Table 1
Geochemical characteristic parameters of soil rare earth elements in the
study area
Statistics ΣLREEs/ΣHREEs (La/Sm)N(Gd/Yb)NδCe δEu
Minimum 1.02 0.74 1.43 0.56 0.13
Maximum 7.10 1.69 5.55 1.14 0.35
Mean 1.98 1.16 3.15 0.84 0.25
SD 1.88 0.29 1.14 0.16 0.06
Median 2.62 1.17 3.22 0.81 0.26
Note: SD: Standard deviation.
Ce and Eu can exist in multiple valence states (Ce4+ and Eu2+), differentiating their fractionation behavior
from other REEs. The anomalies of Ce and Eu are indicative of specic geochemical processes and
sources of REEs (Yu et al., 2022). In our study, all soil samples consistently showed negative Eu and Ce
anomalies, with mean values of 0.25 and 0.84, respectively. The δCe/δEu ratio in studied soil averaged
3.36, suggesting a predominance of reducing conditions, as this ratio exceeds 1. Under such conditions,
Eu3+ can be reduced to Eu2+ and potentially lost, especially under strong reducing conditions. Meanwhile,
positive Ce anomalies often correlate with high sediment alkalinity (Kim et al., 2012). As soil acidity
increases, the transformation of Ce3+ to Ce4+ occurs, often alongside the precipitation of iron or

Page 9/20
manganese oxides, contributing to the observed negative Ce anomalies. Consequently, the studied soil
exhibited marked negative δEu and slightly negative δCe anomalies, attributable to mild acidic and
strongly reducing conditions.
Pollution and potential ecological risks in study soils
The pollution status of REEs was assessed using
I
geo, which provided insights into the ecological risks of
soil contamination. The hierarchy of average
I
geo values for REEs ranged from Gd (1.51) to Tm (-0.29),
with Gd reaching moderate pollution levels (Fig.1a). The results indicated that Nd (0.83) and Y (0.79),
both HREEs, displayed similar distribution patterns, ranging from no pollution to high pollution across all
sample sites. Seven other elements had average
I
geo values above zero (Tb (0.68), Pr (0.56), La (0.21), Ce
(0.13), Dy (0.11), Sc (0.05)), indicating varying levels of pollution from none to moderate. Approximately
one-third of the sampling sites were considered unpolluted, with only two out of 21 sites (S20 and S7)
showing moderate pollution with
I
geo values exceeding 1. The remaining sites indicated between
unpollution to moderate pollution categories. The LREEs primarily revealed the lower contamination
categories, in contrast to the broader dispersion observed for HREEs, which contributed more
signicantly to soil pollution.
The ecological risk of REEs is shown in Fig.2b. Based on the results, all REEs had average values
lower than 40.0, indicating a low ecological risk. The cumulative average RI values for 21 soil sites
ranged from 82.32 to 573.29, ranging between 150 and 300, indicating that the overall mining area is at a
moderate risk. According to criteria, two of 21 sites (S20 and S7) had RI values (573.29 and 418.41,
respectively) above 300, indicating a considerable ecological risk of REEs in these sites. At the same
time, 57% of the sites were medium risk, while the rest were low risk. Eu, Ho, Lu, Dy and Gd were
identied as primary contributors to ecological risk, with numerous sites exhibiting medium risks due to
high concentrations and toxicity coecients of these elements (Nkrumah et al., 2021), posing potential
threats to the ecosystem. To sum up, the
I
geo and RI assessments suggest that the soil in the study area
generally faces low to moderate ecological risks, with sites S7 and S20 requiring further attention and
potential remediation.
Transport and impact of REE in soil-plant system
REEs may disrupt plant ion transport, inuencing its growth by modifying nutrient uptake and
physiological functions. Study indicates that REEs absorbed from the soil tend to accumulate in the
edible parts of crops, potentially increasing human exposure through diet (Li et al., 2013). Thus, the
present study detected REE concentrations in 19 vegetable samples, nding a range from 0.52 to 78.93
mg/kg and an average of 23.17 mg/kg (Table S4). These levels substantially surpass the Chinese
National Standard of 0.7 mg/kg fresh weight (GB2762-2005) and those found in commercially available
vegetables in China, which range from 0.28 to 1.40 mg/kg (Jiang et al., 2012). In the examined mining
area, REE concentrations in vegetables were also markedly higher than those reported from other mining
areas in Fujian (3.58 mg/kg) and Jiangxi provinces (6.55 mg/kg) (Zhang et al., 2000b; Li et al., 2013),
Ei
r

Page 10/20
akin to ndings from a HREEs mine in Longnan county ranging from 1.55 to 78.57 mg/kg (Jin et al.,
2014). The uptake and translocation of REEs across plant species are diverse, typically, LREEs are more
easily enriched in plants compared to HREEs (McLennan and Taylor, 2012). Consistently, we found that
over 50% of the total REEs in vegetables were attributed to La and Ce in this study (Table S4).
Besides these differences in enrichment, this study observed varying REE absorptive capacities across
different vegetable species. We categorized the vegetable samples into three groups: root vegetables,
leafy vegetables, and solanaceous vegetables. Solanaceous vegetables exhibited the lowest REE
concentrations, ranging from 0.52 to 3.09 mg/kg with an average of 1.81 mg/kg. In contrast, root
vegetables had higher concentrations, ranging from 6.11 to 78.93 mg/kg with an average of 25.69
mg/kg. Leafy vegetables presented concentrations between 0.61 and 47.40 mg/kg, averaging 25.67
mg/kg (Table S5). Consistent with the results reported by Zhang et al, our ndings show comparable REE
content in both leafy and root vegetables, suggesting that roots and lush foliage facilitate greater REE
uptake from soils (Zhang et al., 2000a).
REE accumulation in vegetables near mining sites correlates with soil bioavailability. We conducted a
systematic analysis using Spearman correlation matrices to investigate the migration characteristics of
REEs in different vegetables. Our ndings indicated signicant positive correlations between the soil
concentrations of Pr, Nd, Sm, Dy, Ho, Er and Tb and their presence (
P
< 0.05) in leafy vegetables (Fig.3a).
Root vegetables showed signicant correlations with all soil REEs except Ce and Tm (
P
< 0.05, Fig.3b)
and solanaceae vegetables correlated signicantly with all soil REEs except Tm, Lu, and Sc (
P
< 0.05,
Fig.3c). These ndings suggest selective absorption and accumulation of REEs by different vegetable
species.
Principal component analysis (PCA) of soil and vegetable samples revealed two distinct clusters along
the rst two principal components (PC1 and PC2), explaining 86.6% and 8.9% of the variance,
respectively (Fig.3). This analysis conrmed consistent REE distribution patterns across different sites,
emphasizing their ecological interconnectedness. Notably, the PCA indicated distinct groupings of LREE
and HREE in PC2, with Sc and Y being the most signicant variable. Excluding Sc and Y, the remaining
REEs signicantly inuenced PC1, demonstrating unique REE patterns for each vegetable variety despite
identical soil and climate conditions.
Human health Risk Assessment
REEs are increasingly recognized as emerging pollutants due to their environmental persistence,
bioaccumulation, and chronic toxicity (Queiros et al., 2023; Wang et al., 2023). Concerningly, REEs may
adversely affect childhood neurodevelopment, potentially leading to reduced IQ and memory decits
(Wei et al., 2020). Previous study suggested that a daily REE intake of up to 70 µg/kg is generally safe for
human health, but levels between 100 and 110 µg/kg/day could cause subclinical damage (Zhu et al.,
1997). Consequently, it is essential to closely monitor the REE intake of residents near mining areas,
particularly children aged 2 to 12 years, who are particularly vulnerable to pollutants through ingestion
pathway.

Page 11/20
Our study estimated that daily intake of REEs through vegetables signicantly exceeded the safe
threshold of 70 µg/kg/day for all age and gender groups. Notably, children aged 2 to 12 years were at the
highest risk, with intake levels reaching 2.29 times (ages 2 to 7) and 1.73 times (ages 8 to 12) the
subclinical threshold (Table2). In contrast, individuals over 13 years exhibited intake levels near the risk
threshold, with minimal variation across genders. Regarding water sources, REE concentrations were
lower than in other mining regions such as Dingnan and Longnan counties, ranging from 2.00 to 6.87
µg/L with an average of 4.09 µg/L (Jin et al., 2014; Liu et al., 2019). Although the average daily intake
(ADI) of REEs from water was signicantly below the recommended limits, suggesting minimal risk
(Table3), the ADI from vegetables in children and adults consistently reached up to three times the
subclinical threshold, indicating signicant health risks. When adjusting for consumption frequency of
different vegetable species, the daily cumulative REEs intake from selected vegetables was 49.46
µg/kg/day (Table4), nearing the tolerable ADI of 51.5 µg/kg·BW set by the China Scientic Committee
(Yang et al., 2022). Pakchoi and radish, which contribute 76.99% to the dietary REE risk, are of primary
concern for residents in mining areas. It is important to note that the daily dietary intake also includes
grains, meats, fruits, and other foods. For instance, Jin et al. reported that the daily cumulative intake of
REEs through various crops and well water in mining areas reached up to 295.33 µg/kg (Jin et al., 2014).
Given the high REE levels observed in studied soil and vegetables, further comprehensive risk
assessment of REEs in daily diet is warranted.
Table 2
EDI of total REEs via vegetable consumption in mining areas by different gender and age groups
Gender/age group BWa
(kg)
CRa
(g)
EDI
2 ~ 7 years 17.9 194.8 252.2
8 ~ 12 years 33.1 272.4 190.7
Male, 13 ~ 19 years 56.4 396.7 163.0
Female, 13 ~ 19 years 50.0 317.9 147.3
Male, 20 ~ 50 years 63.0 436.4 160.5
Female, 20 ~ 50 years 56.0 412.1 170.5
Male, 51 ~ 65 years 65.0 477.9 170.4
Female, 51 ~ 65 years 58.0 447.0 178.6
Male, > 65 years 59.5 413.3 160.9
Female, > 65 years 52.0 364.1 162.2
Note: EDI: estimated daily intake, µg/kg/day. a Data were from the fth China total diet study.

Page 12/20
Table 3
Average daily intake dose of REEs of local children and adults in mining area via vegetables and water
Group Sample Average
content
(mg/kg)
Days of
consumption
(days/year)
Daily
consumption
(kg)
Average
bodyweight
(kg)
Average
daily intake
(µg/kg/day)
Children
Adult
Vegetables 23.17 365 0.22
0.85
15
60
339.83
338.24
Children
Adult
Water 4.09a365 1.10b
1.60b
15
60
0.30
0.10
Note: a The unit of REEs in water is µg/L; b The unit of REEs in water daily consumption is L.
Table 4
Adjusted ADI of REEs based on consumption frequency of different vegetable species
Vegetable
species Average
content
(mg/kg)
Days of
consumptiona
(days/year)
Daily
consumption
(kg)
Average daily
intake
(µg/kg/day)
Proportion
(%)
Pakchoi 33.78 180 0.10 27.76 56.13
Radish 11.31 100 0.20 10.33 20.88
Spinach 17.56 60 0.05 2.41 4.86
Bamboo
shoot 8.16 30 0.10 1.12 2.26
Celery 50.47 60 0.05 6.91 13.98
Water fennel 9.34 30 0.05 0.64 1.29
Red pepper 1.81 180 0.02 0.30 0.60
Total    49.46 100.00
Note: a Data were from a study conducted by Jin et al (Jin et al., 2014).
Conclusions
The concentration of REEs in soil from the studied area was signicantly higher than the background
levels in China and Jiangxi province. The distribution patterns in the mining area showed a trend of HREE
enrichment. Vegetables from these sites, particularly leafy and root vegetables, exhibited higher REE
concentrations than those permitted by China's National Standards. Health risk assessments reveal that
both the EDI and ADI for REEs via vegetables exceed the critical values for subclinical damage, posing a

Page 13/20
potential health threat to local residents. Given the strong enrichment capacity of leafy and root
vegetables, particularly pakchoi and radish, it is advisable for locals to limit their consumption to
mitigate exposure risks. Additionally, the potential impacts of prolonged low-level REE via dietary intake
exposure on residents, especially children and adolescents, require further investigation.
Declarations
Author Contribution
Conceptualization: Liang Xiong; Formal analysis: Liye Zhu and Jinyu Huang; Investigation: Liye Zhu, Jinyu
Huang, Hui Huang, Sihui Wang, Ziyue Sun, Yi Fang and Ming Hao; Methodology: Jinyu Huang, Qi Wang,
and Liang Xiong; Data curation: Qi Wang, Chunmei Wu and Ming Hao; Writing - original draft: Liye Zhu;
Writing - Review & Editing: Liang Xiong; Funding Acquisition: GongHua Hu and Liang Xiong. All authors
reviewed the manuscript.
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Figures

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Figure 1
Locations of sampling sites in an ion-adsorption rare earth mining area located at Jiangkou Town,
Ganxian District of Ganzhou City

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Figure 2
Box-plot of (a) geo-accumulation index (
Igeo
) and (b) potential ecological risk of REEs in studied soils.

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Figure 3
Heat map of Spearman's correlation analysis between soil REEs and vegetables of roots (a), leaves (b),
and solanaceae (c). Correlation coecient value signicant is marked by asterisks (*
P
< 0.05, **
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and ***
P
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Figure 4
Bi-plot of the principal component analysis based on REEs in soil and vegetables.
Supplementary Files
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