# Rare earth elements (REEs) in soils and plants of Bangka Island (Indonesia) focussing on (hyper)accumulation

Imam Purwadi, Peter D Erskine, Benny P Hutahaean, Tofan R Wijaya, Eddy Nurtjahya, Antony van Der Ent

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Imam Purwadi, Peter D Erskine, Benny P Hutahaean, Tofan R Wijaya, Eddy Nurtjahya, et al. Rare earth elements (REEs) in soils and plants of Bangka Island (Indonesia) focussing on (hyper)accumulation. Plant and Soil, 2024, 507, pp.1-15. 10.1007/s11104-024-06735-2. hal-04665342

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# Rare earth elements (REEs) in soils and plants of Bangka Island (Indonesia) focussing on (hyper)accumulation

Imam Purwadi · Peter D. Erskine · Benny P. Hutahaean · Tofan R. Wijaya · Eddy Nurtjahya · Antony van der Ent

Received: 3 September 2023 / Accepted: 10 May 2024
© The Author(s) 2024

## Abstract

*Background and Aims* Indonesia is one of the most biodiverse regions in the world, but only a few metal hyperaccumulator plants have been reported from this vast country. This study aimed to discover rare earth element (REE) hyperaccumulator plants on Bangka Island, an area known to have REE enriched soils associated with tin placer deposits.

Responsible Editor: Martin J. Hodson.

**Supplementary Information** The online version contains supplementary material available at https://doi.org/10.1007/s11104-024-06735-2.

I. Purwadi · P. D. Erskine · A. van der Ent (✉)
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, Brisbane, QLD, Australia
e-mail: a.vanderent@uq.edu.au

B. P. Hutahaean · T. R. Wijaya
Divisi K3LH, PT Timah Tbk, Batam, Indonesia

E. Nurtjahya
Program Studi Biologi, Universitas Bangka Belitung, Belitung, Indonesia

A. van der Ent
Laboratory of Genetics, Wageningen University and Research, Wageningen, The Netherlands

A. van der Ent
Université de Lorraine, INRAE, LSE, F-54000 Nancy, France

**Methods** Prior to this study, herbarium specimens at the Universitas Bangka Belitung Herbarium were screened using non-destructive X-ray Fluorescence (XRF) scanning to detect specimens with anomalous REE concentrations. Fieldwork was subsequently conducted to collect samples from plant species suspected to be (hyper)accumulators based on the earlier XRF survey. Scanning electron microscopy and micro-XRF were used to verify the possibility of surface contamination by soil particles in plant specimens, and inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine total elemental concentrations in the plant material.

*Results* *Blechnopsis orientalis* was found to hyper- accumulate REEs up to 3000 µg g⁻¹ as well as arsen- ic up to 2100 µg g⁻¹. The non-destructive analysis found no dust or soil contamination on *B. orientalis* specimens, confirming it as a genuine REE and arsenic hyperaccumulator. Additionally, the known REE hyper- accumulator *Dicranopteris linearis* was confirmed to be a REE hyperaccumulator on Bangka Island.

*Conclusion* *Blechnopsis orientalis* is a REE hyper- accumulator with high potential for phytoextraction as it is a faster growing and larger species than *D. linearis*. As *B. orientalis* and *D. linearis* are native to Bangka Island, both should be studied further for their application in rehabilitating and extracting REEs from the (abandoned) tin mine areas.

**Keywords** Rare earth · Arsenic · Fern · Hyperaccumulator · Phytoextraction · Phytoremediation
**Introduction**

Hyperaccumulators are plants that can attain high concentrations of specific metals and metalloids in their living tissues without any symptoms of physiological stress (van der Ent et al. 2013). Among this group of plants, rare earth elements (REE) hyperaccumulators have attracted recent attention because these plants could potentially be used to locate REE-enriched soils and deposits or for extracting REEs in phytomining from soil and industrial by-products and wastes, such as coal ash, red muds, mine tailings (Gaustad et al. 2021). Despite the growing importance of discovering new species of REE hyperac-cumulator plants, of 721 identified hyperaccumula-tor plants, only two species are currently known to hyperaccumulate REEs with potential for phytomin-ing (Reeves et al. 2017). Furthermore, most studies focused on *Dicranopteris linearis* (Burm.f.) Underw. (Gleicheniaceae) from China where it hyperaccumu-lates REEs when growing on REE mine waste soils and surrounding areas (Liu et al. 2018). REE hyper-accumulation is defined as a plant with more than 1000 µg g⁻¹ in its leaves/fronds (Baker and Brooks 1989). The low number of identified REE hyperac-cumulators is partly because REEs are present in relatively low concentrations (Tyler 2004) as well as their low bioavailability (Khan et al. 2017) in most soils. As REEs are not essential nutrients for plants, the mechanisms of REE uptake and accumulation in plants are poorly understood (Yuan et al. 2017). The roots of plants generate exudates that can strongly influence the mobility and bioavailability of REEs in soils (Khan et al. 2017). In *Phytolacca americana*, an REE hyperaccumulator, the roots absorb REEs via aluminium transporters and calcium channels (Yuan et al. 2017) which aligns with a study on 49 fern spe-cies that showed a positive correlation between REE and aluminium and calcium (Grosjean et al. 2019).

Discovery of REE hyperaccumulator plants else-
where in the World requires extensive screening of
plant taxa, for example, two more REE hyperaccu-
mulators were recently discovered (van der Ent et al.
2022) after scanning 27,000 herbarium specimens
originating from Australia, Papua New Guinea, New
Caledonia and Malaysia (Purwadi et al. 2023). A fol-
low-up study confirmed that these new REE hyperac-
cumulators (from the genus Helicia of the Proteaceae

family) occur on REE-bearing rock formations in
Queensland in Australia (van der Ent et al. 2022). As
was previously shown, screening plants occurring on
REE-rich soils will increase the likelihood of encoun-
tering REE hyperaccumulators (Purwadi et al. 2021a).
Analysing herbarium specimens also assists in the
endeavour to locate REEs hyperaccumulators (and/
or other hyperaccumulator plant taxa) by saving time
and cost to collect new samples in the field, often from
remote locales (van der Ent et al. 2019a). An ideal
case would be to focus on herbarium specimens origi-
nating from metal-enriched soils. However, in reality,
herbarium specimens are often collected without those
considerations. Furthermore, searching through mil-
lions of herbarium collections based on their location
data is more challenging than simply X-ray fluores-
cence (XRF) scanning entire selected genera, which
is the common strategy in herbarium XRF scanning
campaigns undertaken thus far (Nkrumah et al. 2018;
van der Ent et al. 2019b; Do et al. 2020).

Bangka Island, off the coast of Sumatra in Indo-
nesia, has high potential for discovery of new REE
hyperaccumulator plant species because the parent
granitic rocks were altered during metasomatic and
hydrothermal processes resulting in the enrichment
of tin (Sn) and REEs bearing minerals (Schwartz
and Surjono 1991), which have been weathered very
intensively producing placer, off- and on-shore depos-
its (Schwartz et al. 1995). Since the early eighteenth
century, Bangka Island has been mined for Sn (Ko
1986). In total, 1.2 million tons of Sn tailings are
produced annually (Szamalek et al. 2013). REEs are
not recovered and therefore the Sn mine tailings con-
tain REEs largely as monazite and xenotime, which
in turn are weathered, leading to the enrichment of
REEs in the soil profile (Setiawan 2018; Zglinicki
et al. 2021) with up 181 µg g⁻¹ tREEs in soils (Sya-
frizal et al. 2021). These types of REE deposits and
weathered REE tailings represent potential untapped
REE resources (Binnemansa et al. 2013; Golev et al.
2014; Binnemans et al. 2015; Mudd and Jowitt 2016).

Given the potential of Bangka Island for discovery
of REE hyperaccumulator plants, this study aimed
to first screen herbarium specimens at Herbarium
Bangka Belitungense to detect taxa with anoma-
lous REE concentrations, followed by fieldwork on
Bangka Island to collect plant material samples (and
associated soil samples) of target species identified as
having anomalous REE concentrations from the XRF
survey.

**Materials and methods**

Study area and soil and plant sample collection

Bangka Island is located in the Southeast Asian tin
belt, which stretches from Myanmar, Thailand to
Malaysia and ends in West Kalimantan, Indonesia.
Bangka Island and Belitung Island are often called
"tin islands" because these island have made Indo-
nesia the peak Sn producing country (United States
Geological Survey 2023). Herbarium Bangka Beli-
tungense is based at a public university on Bangka
Island and was established in 2007. The date on
which the herbarium specimens were collected is a
crucial factor in revisiting where they were collected
because old specimens collected decades or centuries
ago tend to have a problem with locational accuracy.
In total, 1006 specimens kept at Herbarium Bangka
Belitungense were measured using XRF analysis.
Each specimen was measured at least two times,
one time at a young and an old leaf/frond depending
on their size. For specimens with elemental anoma-
lies, additional measurements were conducted on
different parts. The raw spectra from the instrument
were exported as a CSV file, and then imported into
GeoPIXE software, a software package incorporat-
ing dynamic analysis used to fit and process XRF
data. Then the background spectrum and elemental
XRF peaks were fitted and converted into elemen-
tal concentration data as described in Purwadi et al.
(2022). During this study, the XRF instrument was
not fully calibrated and the output of the pipeline pro-
duced relative concentrations. Due to instrumental
limitations, only the concentrations of yttrium (Y) are
reported, and this was sufficient to detect specimens
with anomalous REE and trace elemental concentra-
tions as illustrated in previous studies (van der Ent
et al. 2022; Purwadi et al. 2023). From the results of
XRF scanning, it was found that *Blechnopsis orienta-
lis* showed Y concentration anomalies. Subsequently,
fieldwork sample collection focussed on *B. orientalis*
species with anomalies from across Bangka Island.
*Dicranopteris linearis* was also collected to com-
pare REE concentrations in *D. linearis* from Bangka

Island to other localities. The fieldwork location was
refined based on the specimen location of *B. orienta-
lis*. No roots of *B. orientalis* could be collected, and
only young and old lamina and rachis were collected,
whilst for *D. linearis* young and old *D. linearis* was
taken randomly from each colony. Soil samples (250
g) were collected down to depth of 20 cm from where
each *D. linearis* specimen was taken, but for *B. ori-
entalis*, the soil sample was taken within a 1 m dis-
tance, if possible. Each plant material sample was
thoroughly washed with water, then air-dried, and
finally oven-dried (48 h at 60 °C). Figure 1 shows the
sampling locations, and Fig. 2 shows the target spe-
cies *D. linearis* and *B. orientalis* field. Upon importa-
tion into Australia, all of the soil and plant samples
were gamma irradiated (50 kGy) at Steritech Pty.
Ltd. in Brisbane following Australian Quarantine
Regulations.

Soil and plant elemental analysis

All of the dried soil samples were sieved through
a 2 mm screen and sub-samples were weighed to
100±5 mg in quartz digestion vessels, and 5 mL
HNO3 (70%) and 2 mL HCl (37%) was added
(Wang and Brindle 2014; Han et al. 2021). Each
sample was then digested for 15 min. at 80% power
using a ColdBlock system (CB15S 15 channel sys-
tem, ColdBlock Technologies Inc). The digestates
were transferred to 50 mL tubes and made to vol-
ume (40 mL) with ultra-pure water (Millipore 18.2
MΩ·cm at 25 °C) and filtered (Whatman® Grade 1
filter paper) before analysis with inductively cou-
pled plasma atomic emission spectroscopy (ICP-
AES, as described below). The plant material sam-
ples were manually ground to a fine powder using
a mortar and pestle and weighed to 100±5 mg in
6 mL polypropylene tubes. Then 2 mL HNO3 (70%)
was added to each sample and left for 24 h before
being digested in a block heater (Thermo Scien-
tific™ digital dry bath) for a 2-h program (1 h at
70 °C followed by 1 h at 125 °C) and brough to vol-
ume (40 mL) with ultrapure water before analysis
with ICP-AES. The acid digestates were analysed
with a Thermo Scientific iCAP 7400 instrument for
macro-elements (Ca, K, Mg, Na, P), trace-elements
(Al, As, Co, Cr, Cu, Fe, Ga, In, Mn, Ni, Pb, Ti, Zn),
and REEs (Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd,
<figure><img src="image_2.png" /><figcaption>**Fig. 1** Maps showing a geographic overview of Indonesia with a red square highlighting Bangka Island (a). The inset image in (b) is a magnified view of Bangka Island (b), and further magnified in (c) and (d). The red circles indicate the locations where fern samples were collected. Map data copyrighted by OpenStreetMap contributors and Microsoft Bing map</figcaption></figure>

<figure><img src="image_3.png" /><figcaption>**Fig. 2** Field photographs depicting the typical collection sites for fern samples. Red and blue circles denoting *Blechnopsis orientalis* and *Dicranopteris linearis*, respectively, and white quartz tailings and a colony of *D. linearis* can be seen (a). The old fronds of *B. orientalis* emerges from between *Melastoma malabathricum* in (a) and (b). Occurrences of *B. orientalis* and *D. linearis* along the side of a mine site road (c).</figcaption></figure>

<figure><img src="image_4.png" /></figure>
Pr, Sm, Tb, Tm, Y, Yb), in radial and axial mode depending on the element and expected analyte concentration. Quality controls included matrix blanks, certified reference material (Sigma-Aldrich Periodic table mix 1 for ICP TraceCERT®, 33 elements, 10 mg L⁻¹ in HNO₃) and Standard Reference Material NIST 1570a *Trace Elements in Spinach Leaves* digested as described above for the plant and soil materials.

## Laboratory micro-X-ray fluorescence elemental mapping (micro-XRF)

Several *B. orientalis* frond samples were selected based on their REEs and As concentrations measured using portable XRF instrument. These selected specimens were mounted between sheets of 6 µm Ultralene thin film on a micro-XRF motion stage and scanned in a modified ATLAS X instrument (IXRF, Inc.) at the Centre for Microscopy and Microanalysis, the University of Queensland, Australia. The instrument is a custom-built system which incorporates two 50 kV–1000 µA sources fitted with polycapillary focussing optics. An XOS microfocus Mo-target tube producing 17.4 keV X-rays (flux of 2.2 × 10⁸ ph s⁻¹) focussed to 25 µm was used here. The micro-XRF spectra were acquired in mapping mode controlled using Iridium (IXRF, Inc.) software and the data processed in GeoPIXE software (Ryan 2000; Ryan et al. 2005) post hoc.

## Scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS)

One of the *B. orientalis* frond samples was freeze-dried (Thermoline), mounted on an Al-stub, sputter-coated with carbon and imaged using scanning electron microscopy with energy-dispersive X-ray spectroscopy (Hitachi SU3500) with 100–1000-fold magnification and 5 and 15 kV electron voltage. The lower accelerator energies were used for imaging using only secondary electron returns and higher accelerator energies for backscatter mode imaging and EDS point analyses. The data were analysed with AZtecEnergy Microanalysis software.

## Statistical analysis

The distribution of REEs follows the Oddo-Harkins rule which represents a zigzag pattern in which even atomic numbers of REEs are more abundant than those with odd atomic numbers (Ramos et al. 2016). Anomalous REE concentrations are normalised to chondritic abundance, a theoretical abundance of an element when the universe is formed (O'Neill 2016) and here we use the values provided in Taylor and McLennan (1995) to interpret soil REE concentrations.

## Results

### Herbarium XRF scanning for REE detection

In the herbarium XRF scanning 1006 specimens kept in Herbarium Bangka Belitungense were analysed, and 617 species were identified and after processing the raw XRF spectra, Y concentration anomalies (>50 µg g⁻¹) were detected in two species, namely, *Dicranopteris linearis* and *Blechnopsis orientalis*.

Rare earth element concentrations in *Blechnopsis orientalis* and *Dicranopteris linearis* and associated soils

The XRF scanning of herbarium specimens at Herbarium Bangka Belitungense led to the discovery of specimens with 1000 µg g⁻¹ > REE concentrations in *B. orientalis* (L.) C.Presl. This taxon was previously known as *Blechnum orientale* (L.) and is widespread in Southeast Asia (de Gasper et al. 2016, 2017; Schuettpelz et al. 2016). The fieldwork then focussing on *B. orientalis*. In addition, *D. linearis* was also collected to evaluate the hyperaccumulation traits of this species in Bangka Islands compared to elsewhere. Compared to upper continental crust abundance, the average concentration of Sc, Y, Eu, Ho, Er, and Lu in soils showed negative anomalies, while positive anomalies were observed in La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Tm, and Yb Fig. 3. Scatter plots of total REEs concentrations in soils and in *B. orientalis* and *D. linearis* (Fig. 4) reveal that there are no clear correlations between total REEs concentrations in soils and the old rachis, old pinna, young rachis, and young pinna of both fern species. In Figures S1 and
**Fig. 3** Minimum, mean, and maximum REE concentrations in soil samples divided by REE upper continental crust abundance concentrations provided by Taylor and McLennan (1995). Lines above the black line indicates enrichment and below indicates depletion. The numbers next to the dots represent one significant concentration in µg g⁻¹ and values are provided in Table S1

<figure><img src="image_5.png" /></figure>

**Fig. 4** Scatter plots between total REEs concentrations in soils and *Blechnopsis orientalis* and *Dicranopteris linearis*. The coefficient of determination for each regression is provided in the legend

<figure><img src="image_6.png" /></figure>

S2, soil samples were grouped into two clusters based on their elemental composition after principal component analysis, and each plant was assigned to the same group as its corresponding soil sample, but no significant correlation between soil total REE concentrations and shoot concentrations was observed. Several samples of *B. orientalis* and *D. linearis* contained total REEs concentrations > 1000 µg g⁻¹ whereas the soil had a total REE concentration < 10 µg g⁻¹. When comparing the mean and maximum REEs concentrations, the old pinna of *B. orientalis* had higher concentrations of all REEs than *D. linearis* (Table 1). For example, up to 930 µg g⁻¹ Y in *B. orientalis* and 350 µg g⁻¹ Y in *D. linearis* (Table 1). On average, the translocation of REEs in both *B. orientalis* and *D. linearis* follows a pattern with higher concentrations in the old pinna, followed by young pinna, young rachises/petioles, but the magnitude of translocation differs (Fig. 5). *Blechnopsis orientalis* tends to translocate REE more to old pinna compared to *D. linearis*, but the translocation

rate of *D. linearis* from old rachis to young pinna is higher than that in *B. orientalis*. The REE concentrations are shown in Fig. 6 and old pinnae of *B. orientalis* exceeds the REE hyperaccumulator threshold (1000 µg g⁻¹), confirming that it is an REE hyper accumulator as previously reported (Liu et al. 2018). In addition to REE concentrations, macronutrients and trace elements are given in Table 2 which shows that *B. orientalis* has higher macronutrient concentrations compared to *D. linearis* with an average *B. orientalis* have at least twice the P, K, Mg and Ca concentrations in that of *D. linearis*. Aluminium, which is toxic to most plants, was accumulated by some *D. linearis* up to 8000 µg g⁻¹, while some *B. orientalis* up to 790 µg g⁻¹. It was also found that the old pinna of a *B. orientalis* sample contain As up to 2100 µg g⁻¹ whilst *D. linearis* has <10 µg g⁻¹ As in (Table 3). The As concentrations in soils, had an average and maximum of 34 µg g⁻¹ and 273 µg g⁻¹ respectively. Three *B. orientalis* samples taken from the same vicinity had As concentrations up
<table><caption>**Table 1** Rare earth element (REE) concentrations in plant organs of *Blechnopsis orientalis* and *Dicranopteris linearis*</caption><thead><tr><th rowspan="2">n</th><th colspan="4">Blechnopsis orientalis</th><th colspan="4">Dicranopteris linearis</th><th colspan="2">LOD</th></tr><tr><th>old pinna</th><th>old rachis</th><th>young pinna</th><th>young rachis</th><th>old pinna</th><th>old petiole</th><th>old root</th><th>young pinna</th><th>young petiole</th><th>young root</th></tr></thead><tbody><tr><td>46</td><td>45</td><td></td><td>16</td><td>16</td><td>50</td><td>50</td><td>48</td><td>49</td><td>48</td><td>48</td></tr><tr><td>Sc</td><td>0.01–0.32<br>[0.13]</td><td>0.02–0.089<br>[0.055]</td><td>&lt;LOD</td><td>&lt;LOD</td><td>0.009–0.029<br>[0.019]</td><td>0.008–0.014<br>[0.011]</td><td>0.001–0.51<br>[0.089]</td><td>0.007–0.23<br>[0.081]</td><td>0.008–0.071<br>[0.039]</td><td>0.0025–0.41<br>[0.12]</td><td>0.0003<br>[0.12]</td></tr><tr><td>Y</td><td>0.11–930<br>[68]</td><td>0.02–18<br>[1.6]</td><td>0.45–42<br>[9.6]</td><td>0.03–21<br>[2.6]</td><td>0.08–350<br>[21]</td><td>0.006–15<br>[0.8]</td><td>0.008–63<br>[2.2]</td><td>0.02–260<br>[15]</td><td>0.004–23<br>[1.3]</td><td>0.0008–44<br>[2.7]</td><td>0.0005<br>[2.7]</td></tr><tr><td>La</td><td>0.02–440<br>[70]</td><td>0.002–24<br>[4.2]</td><td>0.59–77<br>[17]</td><td>0.001–27<br>[4.8]</td><td>0.11–280<br>[38]</td><td>0.006–34<br>[3.1]</td><td>0.01–16<br>[2.2]</td><td>0.16–440<br>[39]</td><td>0.03–150<br>[6.1]</td><td>0.01–110<br>[8.1]</td><td>0.001<br>[8.1]</td></tr><tr><td>Ce</td><td>0.9–640<br>[160]</td><td>0.34–24<br>[7.1]</td><td>3.4–170<br>[39]</td><td>0.1–82<br>[13]</td><td>0.01–600<br>[79]</td><td>0.35–82<br>[7.3]</td><td>0.13–28<br>[4.8]</td><td>0.04–680<br>[72]</td><td>0.03–280<br>[14]</td><td>0.14–220<br>[18]</td><td>0.0108<br>[18]</td></tr><tr><td>Pr</td><td>0.87–190<br>[42]</td><td>0.02–6<br>[1.6]</td><td>0.57–42<br>[9.2]</td><td>0.02–20<br>[3]</td><td>0.15–150<br>[20]</td><td>0.04–20<br>[2.3]</td><td>0.013–6.6<br>[1.2]</td><td>0.14–180<br>[20]</td><td>0.006–73<br>[4.5]</td><td>0.01–54<br>[5.1]</td><td>0.0033<br>[5.1]</td></tr><tr><td>Nd</td><td>0.11–330<br>[49]</td><td>0.04–7.2<br>[1.8]</td><td>0.1–40<br>[9.6]</td><td>0.15–19<br>[3.5]</td><td>0.06–220<br>[26]</td><td>0.078–19<br>[3.5]</td><td>0.033–10<br>[1.6]</td><td>0.062–270<br>[29]</td><td>0.1–93<br>[7.8]</td><td>0.12–98<br>[8.3]</td><td>0.0095<br>[8.3]</td></tr><tr><td>Sm</td><td>0.03–92<br>[8.8]</td><td>0.03–1.4<br>[0.35]</td><td>0.07–6.3<br>[1.6]</td><td>0.03–3.8<br>[0.54]</td><td>0.09–51<br>[4.5]</td><td>0.006–3.3<br>[0.4]</td><td>0.025–2.8<br>[0.38]</td><td>0.02–61<br>[4.3]</td><td>0.04–16<br>[0.8]</td><td>0.02–22<br>[1.1]</td><td>0.0029<br>[1.1]</td></tr><tr><td>Eu</td><td>0.01–1.7<br>[0.53]</td><td>&lt;LOD</td><td>0.006–0.23<br>[0.074]</td><td>0.17–0.17<br>[0.17]</td><td>0.008–5.8<br>[0.43]</td><td>0.08–0.076<br>[0.076]</td><td>&lt;LOD</td><td>0.001–3.4<br>[0.47]</td><td>0.01–0.72<br>[0.36]</td><td>0.03–0.56<br>[0.25]</td><td>0.0005<br>[0.25]</td></tr><tr><td>Gd</td><td>0.07–110<br>[11]</td><td>0.03–2.1<br>[0.44]</td><td>0.06–6.9<br>[1.5]</td><td>0.03–3.6<br>[0.74]</td><td>0.008–60<br>[4.5]</td><td>0.03–3.1<br>[0.66]</td><td>0.004–4<br>[0.59]</td><td>0.02–47<br>[4.1]</td><td>0.023–9.3<br>[1.2]</td><td>0.02–12<br>[1.3]</td><td>0.0017<br>[1.3]</td></tr><tr><td>Tb</td><td>0.04–3.1<br>[1.6]</td><td>&lt;LOD</td><td>&lt;LOD</td><td>&lt;LOD</td><td>0.35–0.35<br>[0.35]</td><td>&lt;LOD</td><td>0.09–1.2<br>[0.46]</td><td>0.14–0.14<br>[0.14]</td><td>&lt;LOD</td><td>0.01–0.94<br>[0.4]</td><td>0.0047<br>[0.4]</td></tr><tr><td>Dy</td><td>0.04–130<br>[9.6]</td><td>0.02–2.2<br>[0.29]</td><td>0.31–5.8<br>[1.6]</td><td>0.05–3.2<br>[0.54]</td><td>0.09–64<br>[3.9]</td><td>0.005–2.5<br>[0.26]</td><td>0.08–7.8<br>[0.59]</td><td>0.05–45<br>[3.1]</td><td>0.01–6.5<br>[0.56]</td><td>0.03–11<br>[0.8]</td><td>0.002<br>[0.8]</td></tr><tr><td>Ho</td><td>0.01–21<br>[2.2]</td><td>0.007–0.26<br>[0.077]</td><td>0.03–0.97<br>[0.28]</td><td>0.005–0.53<br>[0.12]</td><td>0.002–9.9<br>[0.74]</td><td>0.005–0.29<br>[0.08]</td><td>0.034–1.2<br>[0.19]</td><td>0.02–5.5<br>[0.65]</td><td>0.01–0.87<br>[0.16]</td><td>0.0006–0.88<br>[0.18]</td><td>0.0013<br>[0.18]</td></tr><tr><td>Er</td><td>0.03–53<br>[4.4]</td><td>0.01–0.8<br>[0.25]</td><td>0.05–1.9<br>[0.59]</td><td>0.04–1.4<br>[0.5]</td><td>0.03–24<br>[1.6]</td><td>0.014–0.82<br>[0.14]</td><td>0.013–4.7<br>[0.42]</td><td>0.03–16<br>[1.3]</td><td>0.0052–1.8<br>[0.35]</td><td>0.006–3.2<br>[0.44]</td><td>0.0014<br>[0.44]</td></tr><tr><td>Tm</td><td>0.003–8<br>[0.85]</td><td>0.002–0.019<br>[0.0092]</td><td>0.01–0.18<br>[0.062]</td><td>0.02–0.2<br>[0.081]</td><td>0.001–3.7<br>[0.22]</td><td>0.0034–0.098<br>[0.024]</td><td>0.0052–0.88<br>[0.11]</td><td>0.003–1.7<br>[0.2]</td><td>0.0018–0.042<br>[0.014]</td><td>0.003–0.32<br>[0.074]</td><td>0.0007<br>[0.074]</td></tr><tr><td>Yb</td><td>0.03–28<br>[3.3]</td><td>0.005–0.19<br>[0.053]</td><td>0.11–1.1<br>[0.46]</td><td>1.2–1.2<br>[1.2]</td><td>0.04–14<br>[1.2]</td><td>0.21–0.21<br>[0.21]</td><td>0.003–4.4<br>[0.47]</td><td>0.015–5.4<br>[1.1]</td><td>0.062–0.18<br>[0.12]</td><td>0.014–1.9<br>[0.34]</td><td>0.0019<br>[0.34]</td></tr><tr><td>Lu</td><td>0.0045–4.1<br>[0.52]</td><td>0.004–0.019<br>[0.0086]</td><td>0.0027–0.17<br>[0.058]</td><td>0.003–0.24<br>[0.055]</td><td>0.003–1.7<br>[0.17]</td><td>0.046–0.046<br>[0.046]</td><td>0.002–0.72<br>[0.064]</td><td>0.0004–0.67<br>[0.098]</td><td>0.058–0.058<br>[0.058]</td><td>0.0008–0.28<br>[0.035]</td><td>0.0003<br>[0.035]</td></tr></tbody></table>
<table><caption>**Table 1 (continued)**</caption><thead><tr><th rowspan="2">n</th><th colspan="3">Blechnopsis orientalis</th><th colspan="3">Dicranopteris linearis</th><th colspan="3">LOD</th></tr><tr><th>old pinna</th><th>old rachis</th><th>young pinna</th><th>young rachis</th><th>old pinna</th><th>old root</th><th>young pinna</th><th>young petiole</th><th>young root</th></tr></thead><tbody><tr><td></td><td>46</td><td>45</td><td>16</td><td>16</td><td>50</td><td>48</td><td>49</td><td>48</td><td>48</td></tr><tr><td>Sum</td><td>0.31–2900 [390]</td><td>0–85 [14]</td><td>0.73–400 [83]</td><td>0.5–180 [24]</td><td>1.3–1400 [190]</td><td>0.0062–180 [11]</td><td>0.098–1800 [160]</td><td>0–650 [20]</td><td>0.28–130 [11]</td></tr></tbody></table>

<figure><img src="image_7.png" /><figcaption>**Fig. 5** The translocation rate of total, heavy, and light REE in plant organs of *Blechnopsis orientalis* and *Dicranopteris linearis*</figcaption></figure>

to 2100 µg g⁻¹ while the mean soil As concentration was 34 µg g⁻¹.

Elemental distribution in *Blechnopsis orientalis* pinnules and contamination

*Blechnopsis orientalis* pinnae were screened with portable XRF and samples with REE anomalies were selected for subsequent micro-XRF and SEM-EDS

<figure><img src="image_8.png" /></figure>
<figure><img src="image_9.png" /><figcaption>**Fig. 6** Total REE concentrations in plant organs of *Blechnopsis orientalis* and *Dicranopteris linearis*. The red horizontal lines indicate the REE hyperaccumulator threshold at 1000 µg g⁻¹ total REEs</figcaption></figure>

analysis. Of the REEs, only La could be analysed, as the micro-XRF cannot excite any K-lines of elements Z>La, whilst the L-lines of the REEs suffer from line-overlaps with the first-row transition metals. As can be seen in Fig. 7, La concentrates at the edge of the pinnules. Across different pinnules of *B. orientalis*, the sample at the right side has an As anomaly, and ICP-AES results confirmed that this pinna had 2100 µg g⁻¹ As. Field collected plant material samples are often prone to surficial contamination by soil particulates (Gei et al. 2018), and the pinnules of *B. orientalis* were subjected to surface examination using SEM-EDS analysis. Figure 8 shows that no discernible surface contamination can be observed on the *B. orientalis* pinnule surface and no signals from REEs or As could be detected.

## Discussion

This study used portable XRF analysis to screen herbarium collections at Herbarium Bangka Belitungense leading to the discovery of *B. orientalis* as a hyperaccumulator of REEs. Field collected samples revealed that *B. orientalis* can also hyperaccumulate As. In a recent XRF screening study conducted at the herbarium of Muséum national d'Histoire naturelle (MNHN, Paris, France) *B. orientalis* from other localities in Southeast Asia were found to hyperaccumulate REEs up to 4200 µg g⁻¹

(Gourdard et al. 2024). In this study, *B. orientalis* had total REEs up to 2900 µg g⁻¹, which is almost three times the REE hyperaccumulator threshold of 1000 µg g⁻¹ and As up to 2100 µg g⁻¹, which is twice the As hyperaccumulator threshold of 1000 µg g⁻¹. The fractionation of REEs in *B. orientalis* follows the same trend as found in a recently reported REE hyperaccumulator, *Helicia glabriflora*, in which old fronds contain more REEs than young fronds, indicating strong translocation and distribution limitation of REEs from mature to young fronds (van der Ent et al. 2022). Lanthanum, one of REEs, accumulates at the margins of *B. orientalis* pinnules. Compared to *D. linearis*, REEs were highest at necrotic lesions (Liu et al. 2020, 2021). In addition to accumulating in the pinnule margin, As also accumulated in midveins, and K had a similar pattern. A study of As hyperaccumulators reported that As can induce increased K in fronds (Tu and Ma 2005). Arsenic hyperaccumulation is known from ferns, such as *Pityrogramma calomelanos* and *Pteris vittata* (Ma et al. 2001; Visoottiviseth et al. 2002), and a study suggested that other ferns species may hyperaccumulate As (Zhao et al. 2002). In, *B. orientalis* we record the first fern species to hyperaccumulate As outside the Pteridaceae, *Pteris* and *Pityrogramma* genera. Compared to the two previously known As hyperaccumulator plants, *B. orientalis* has relatively higher biomass. *Pteris vittate* is the first reported As hyperaccumulators, and together with other species from
<table><caption>**Table 2** Macronutrient and micronutrient concentrations in plant organs of *Blechnopsis orientalis* and *Dicranopteris linearis*</caption><thead><tr><th rowspan="2">n</th><th colspan="4">Blechnopsis orientalis</th><th colspan="4">Dicranopteris linearis</th></tr><tr><th>old pinna</th><th>old rachis</th><th>young pinna</th><th>young rachis</th><th>old pinna</th><th>old petiole</th><th>old root</th><th>young pinna</th><th>young petiole</th><th>young root</th></tr></thead><tbody><tr><td>Ca</td><td>73-11,000<br>[4900]</td><td>380-5100<br>[1800]</td><td>1000-5800<br>[2200]</td><td>490-3500<br>[1000]</td><td>150-3400<br>[1200]</td><td>40-2100<br>[310]</td><td>110-1500<br>[460]</td><td>210-4600<br>[1000]</td><td>31-2500<br>[320]</td><td>94-4800<br>[580]</td></tr><tr><td>K</td><td>4100-33000<br>[13000]</td><td>4000-25000<br>[14000]</td><td>7400-38000<br>[22000]</td><td>11,000-27000<br>[21000]</td><td>2500-15000<br>[6300]</td><td>1300-16000<br>[3500]</td><td>1500-8500<br>[4600]</td><td>1800-18000<br>[8500]</td><td>860-14000<br>[4500]</td><td>2000-12000<br>[5300]</td></tr><tr><td>Fe</td><td>4.1-990<br>[89]</td><td>0.61-260<br>[43]</td><td>10-54<br>[26]</td><td>3.2-92<br>[21]</td><td>1.2-150<br>[45]</td><td>0.081-110<br>[23]</td><td>12-2300<br>[220]</td><td>0.96-1100<br>[63]</td><td>0.18-240<br>[28]</td><td>3.4-1400<br>[220]</td></tr><tr><td>Mg</td><td>220-8800<br>[3200]</td><td>120-2800<br>[960]</td><td>1400-4300<br>[2600]</td><td>880-2900<br>[1600]</td><td>66-2200<br>[740]</td><td>51-2300<br>[240]</td><td>23-820<br>[310]</td><td>130-2200<br>[800]</td><td>24-1100<br>[300]</td><td>83-1800<br>[380]</td></tr><tr><td>P</td><td>210-3300<br>[890]</td><td>76-1900<br>[370]</td><td>190-6100<br>[1700]</td><td>260-1600<br>[570]</td><td>89-1400<br>[560]</td><td>22-1800<br>[170]</td><td>39-540<br>[170]</td><td>110-1600<br>[770]</td><td>27-720<br>[190]</td><td>64-1200<br>[240]</td></tr><tr><td>Mn</td><td>11-720<br>[84]</td><td>0.63-280<br>[33]</td><td>11-53<br>[27]</td><td>6.3-27<br>[13]</td><td>32-1100<br>[310]</td><td>9.3-180<br>[72]</td><td>4.3-320<br>[30]</td><td>16-1800<br>[250]</td><td>3.1-1100<br>[93]</td><td>3.3-790<br>[63]</td></tr><tr><td>Co</td><td>0.12-1.7<br>[0.86]</td><td>0.16-1.9<br>[0.69]</td><td>0.5-0.62<br>[0.56]</td><td>0.13-0.76<br>[0.51]</td><td>0.55-2.4<br>[1.1]</td><td>0.27-1.3<br>[0.76]</td><td>0.05-4.8<br>[1.2]</td><td>0.11-2.8<br>[0.87]</td><td>0.57-1.4<br>[0.89]</td><td>0.3-2.2<br>[1.1]</td></tr><tr><td>Ni</td><td>0.2-26<br>[4.4]</td><td>0.18-15<br>[5]</td><td>0.33-32<br>[14]</td><td>3.5-9.9<br>[6.7]</td><td>0.068-18<br>[3.6]</td><td>0.033-3.3<br>[1.7]</td><td>0.045-10<br>[2.3]</td><td>0.086-3.6<br>[1.9]</td><td>1.1-1.1<br>[1.1]</td><td>0.27-3.4<br>[1.6]</td></tr><tr><td>Zn</td><td>5.9-130<br>[25]</td><td>4.1-23<br>[11]</td><td>9.8-52<br>[26]</td><td>8-24<br>[14]</td><td>4.4-78<br>[26]</td><td>0.64-29<br>[8.1]</td><td>3.3-54<br>[13]</td><td>4.7-65<br>[29]</td><td>2.6-64<br>[11]</td><td>3.4-78<br>[16]</td></tr></tbody></table>

<figure><img src="image_10.png" /></figure>
<table><caption>**Table 3** Trace elemental concentrations in plant organs of *Blechnopsis orientalis* and *Dicranopteris linearis*</caption><thead><tr><th rowspan="2">n</th><th colspan="3">Blechnopsis orientalis</th><th colspan="3">Dicranopteris linearis</th><th rowspan="2">young root</th><th rowspan="2">young petiole</th><th rowspan="2">young pinna</th><th rowspan="2">old root</th><th rowspan="2">old petiole</th><th rowspan="2">old pinna</th><th colspan="3">Blechnopsis orientalis</th></tr><tr><th>old pinna</th><th>old rachis</th><th>young pinna</th><th>young rachis</th><th>old pinna</th><th>old petiole</th><th>old pinna</th><th>old rachis</th><th>young pinna</th><th>young rachis</th><th>old pinna</th><th>old petiole</th><th>old pinna</th><th>old rachis</th></tr></thead><tbody><tr><td>Al</td><td>14-790<br>[150]</td><td>3.7-210<br>[50]</td><td>2.6-260<br>[44]</td><td>3.4-87<br>[25]</td><td>120-5600<br>[2000]</td><td>74-1900<br>[230]</td><td>74-1900<br>[2000]</td><td>7.1-1.1<br>[1.1]</td><td>0.11-0.61<br>[0.36]</td><td>0.84-1.4<br>[1.1]</td><td>64-8000<br>[1800]</td><td>160-3200<br>[1300]</td><td>1.1-1.1<br>[1.1]</td><td>0.2-4.8<br>[2.5]</td><td>0.2-4.8<br>[2.5]</td><td>1.4-3.1<br>[2.3]</td></tr><tr><td>As</td><td>0.91-2100<br>[310]</td><td>54-410<br>[230]</td><td>&lt;LOD<br>[LOD]</td><td>&lt;LOD<br>[LOD]</td><td>0.03-1.2<br>[0.55]</td><td>0.32-0.52<br>[0.42]</td><td>0.09-3.9<br>[1.6]</td><td>0.32-0.52<br>[0.42]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.38-2.6<br>[0.29]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td></tr><tr><td>Cd</td><td>0.18-0.99<br>[0.59]</td><td>0.15-0.15<br>[0.15]</td><td>0.12-0.17<br>[0.14]</td><td>&lt;LOD<br>[LOD]</td><td>0.2-1.2<br>[0.69]</td><td>0.06-0.54<br>[0.3]</td><td>0.02-0.55<br>[0.29]</td><td>0.2-1.2<br>[0.69]</td><td>0.06-0.54<br>[0.3]</td><td>0.04-3.9<br>[1.4]</td><td>0.38-2.6<br>[0.29]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td></tr><tr><td>Cr</td><td>1.1-1.1<br>[1.1]</td><td>0.06-0.35<br>[0.23]</td><td>&lt;LOD<br>[LOD]</td><td>0.27-0.27<br>[0.27]</td><td>0.2-3.2<br>[1.2]</td><td>0.96-11<br>[4.8]</td><td>0.21-6.4<br>[2.9]</td><td>0.2-3.2<br>[1.2]</td><td>0.96-11<br>[4.8]</td><td>0.13-39<br>[5.6]</td><td>0.38-2.6<br>[0.29]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td></tr><tr><td>Cu</td><td>1.2-120<br>[16]</td><td>2-25<br>[6.5]</td><td>2.2-15<br>[8.9]</td><td>1.5-6.6<br>[3.6]</td><td>0.2-3.2<br>[1.2]</td><td>0.96-11<br>[4.8]</td><td>0.21-6.4<br>[2.9]</td><td>0.2-3.2<br>[1.2]</td><td>0.96-11<br>[4.8]</td><td>0.13-39<br>[5.6]</td><td>0.38-2.6<br>[0.29]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td><td>0.01-0.043<br>[0.029]</td><td>0.1-3.1<br>[1.6]</td></tr><tr><td>Pb</td><td>7.1-51<br>[23]</td><td>1.2-49<br>[26]</td><td>0.55-2.6<br>[1.6]</td><td>8.1-8.1<br>[8.1]</td><td>3.2-64<br>[27]</td><td>2-31<br>[12]</td><td>&lt;LOD<br>[LOD]</td><td>3.2-64<br>[27]</td><td>2-31<br>[12]</td><td>&lt;LOD<br>[LOD]</td><td>0.32-420<br>[73]</td><td>1.5-15<br>[8.1]</td><td>0.09-7.9<br>[2]</td><td>0.05-7.2<br>[0.85]</td><td>0.09-7.9<br>[2]</td><td>0.05-7.2<br>[0.85]</td><td>0.09-7.9<br>[2]</td></tr><tr><td>Ti</td><td>0.01-15<br>[2]</td><td>0.04-7<br>[0.88]</td><td>0.11-0.41<br>[0.19]</td><td>0.04-0.84<br>[0.3]</td><td>0.02-4.1<br>[0.47]</td><td>0.053-6.8<br>[0.52]</td><td>0.09-7.9<br>[2]</td><td>0.02-4.1<br>[0.47]</td><td>0.053-6.8<br>[0.52]</td><td>0.09-7.9<br>[2]</td><td>0.05-7.2<br>[0.85]</td><td>0.09-7.9<br>[2]</td><td>0.05-7.2<br>[0.85]</td><td>0.09-7.9<br>[2]</td><td>0.05-7.2<br>[0.85]</td><td>0.09-7.9<br>[2]</td></tr><tr><td>U</td><td>0.03-120<br>[30]</td><td>0.06-1.7<br>[0.58]</td><td>0.05-18<br>[4.1]</td><td>0.2-6.6<br>[1.9]</td><td>0.04-110<br>[21]</td><td>0.75-0.75<br>[0.75]</td><td>1.2-2<br>[1.5]</td><td>0.04-110<br>[21]</td><td>0.75-0.75<br>[0.75]</td><td>1.2-2<br>[1.5]</td><td>0.13-89<br>[28]</td><td>0.03-1.2<br>[0.36]</td><td>0.13-89<br>[28]</td><td>0.03-1.2<br>[0.36]</td><td>0.03-1.2<br>[0.36]</td><td>0.03-1.2<br>[0.36]</td><td>0.03-1.2<br>[0.36]</td></tr><tr><td>V</td><td>0.003-5.5<br>[1]</td><td>0.03-0.66<br>[0.36]</td><td>0.4-0.4<br>[0.4]</td><td>0.2-0.19<br>[0.19]</td><td>0.004-0.9<br>[0.3]</td><td>0.015-0.56<br>[0.24]</td><td>0.04-1.9<br>[0.71]</td><td>0.004-0.9<br>[0.24]</td><td>0.015-0.56<br>[0.24]</td><td>0.04-1.9<br>[0.71]</td><td>0.03-1.2<br>[0.36]</td><td>0.05-1.1<br>[0.54]</td><td>0.03-1.2<br>[0.36]</td><td>0.05-1.1<br>[0.54]</td><td>0.05-1.1<br>[0.54]</td><td>0.05-1.1<br>[0.54]</td><td>0.05-1.1<br>[0.54]</td></tr><tr><td>Zr</td><td>0.01-0.66<br>[0.24]</td><td>0.005-0.3<br>[0.12]</td><td>0.01-0.009<br>[0.009]</td><td>0.01-0.072<br>[0.043]</td><td>0.0005-0.65<br>[0.32]</td><td>0.0004-0.19<br>[0.074]</td><td>0.04-3.4<br>[0.67]</td><td>0.0005-0.65<br>[0.32]</td><td>0.0004-0.19<br>[0.074]</td><td>0.04-3.4<br>[0.67]</td><td>0.03-0.75<br>[0.27]</td><td>0.003-0.4<br>[0.091]</td><td>0.03-0.75<br>[0.27]</td><td>0.003-0.4<br>[0.091]</td><td>0.003-0.4<br>[0.091]</td><td>0.003-0.4<br>[0.091]</td><td>0.003-0.4<br>[0.091]</td></tr></tbody></table>
<figure><img src="image_11.png" /><figcaption>**Fig. 7** Laboratory micro-XRF elemental maps showing the distributions of P, K, Ca, Mn, Fe, As, and La in pinnules of *Blechnopsis orientalis*</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>**Fig. 8** SEM image of *Blechnopsis orientalis* pinnule surface in backscattered electron composition mode</figcaption></figure>

Pteridaceae, they hyperaccumulate and tolerate As (Gumaelius et al. 2004; Xie et al. 2009). In *P. vittata*, arsenate is taken up by phosphate transporters (Indriolo et al. 2010; Ditusa et al. 2016), and *B. orientalis* may also have a similar behaviour as shown in Fig. 7, in which the sample shows high intensities of P and As. The regression analysis of total REEs concentration in soil and ferns revealed no significant (positive) correlations. The ferns can attain > 1000 µg g⁻¹ when growing in soils with < 10 µg g⁻¹. This phenomenon aligns with a broader study's proposition (Stein et al. 2017), suggesting that the accumulation of metals in plants is not solely dictated by soil type. This implies that, even within similar soil environments, the accumulation of metals can exhibit divergence, a phenomenon highlighted by the existence

<figure><img src="image_13.png" /></figure>
of within-population variation. This variation under-
scores the intricate nature of ecological adaptation
in response to metal presence, potentially indicating
an adaptive response to the distinct challenges posed
by these metals. Compared to *D. linearis*, *B. orientalis* is large and fast-growing and a stronger REE
hyperaccumulator. In addition, *D. linearis* tends to
colonize open barren areas and whereas *B. orientalis* grows in wetter shaded areas. This differential habitat preference contributes to these fern species ecological diversity and specialization. Given the high
growth and REE hyperaccumulation characteristics
of *B. orientalis*, it has a potential for phytomining
(agromining), but further research and exploration
are necessary to determine the full potential and suitability for this purpose.

To date, most of the research on *D. linearis* and REE hyperaccumulation has been undertaken in China where this species grows on REE mine sites. This study revealed similar concentration patterns in which the fern hyperaccumulates aluminium and REEs (Liu et al. 2019). This result further supports the suggestion that REE hyperaccumulation is a constitutive trait of *D. linearis* (Koyama et al. 1987; Zhenggui et al. 2001; Purwadi et al. 2021b), with the hyper accumulator trait of *D. linearis* a common characteristic across its distribution range, beyond China.

**Acknowledgements** We would like to express our sincere gratitude and appreciation to the Ministry of Energy and Mineral Resources, Indonesia, and PT Timah Tbk for their invaluable support throughout our fieldwork activities and their permission for analysing the collected samples in our lab. We would like to extend special thanks to Mr. Firmansyah Adi Prianto from the Ministry for his guidance and help from the early stage of fieldwork to the presentation of this study. We would like to express our gratitude to Mr Angga Widya Yogatama from PT Timah Tbk for his invaluable insights and recommendations that greatly contributed to refining the selection of my fieldwork area. We are grateful to the Herbarium Bangka Belitungense for allowing examination and sampling of its herbarium specimens. Additionally, we extend our heartfelt thanks to Mr. Tegar Dwi Santoso for his assistance during the fieldwork. Also, we thank Mr. Vinod Nath for his help during lab work, and Dr Amelia Corzo-Remigio for her help during SEM analysis. We also acknowledge the expertise and support provided by Dr Lachlan W. Casey and Microscopy Australia at the Centre for Microscopy and Microanalysis, at the University of Queensland for the micro-XRF analysis.

**Author contributions** IP, AVDE, and PDE conceived the presented idea. EN prepared and measured herbarium specimens and identified local plant species. ACR performed SEM

analysis. IP, BPH, and TRW conducted fieldwork. All authors
discussed and wrote the manuscript.

**Funding** Open Access funding enabled and organized by CAUL and its Member Institutions. Imam Purwadi was the recipient of an Australian Government Research Training Program Scholarship at The University of Queensland, Australia.

**Data Availability** The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

**Conflicts of interest** The authors declare no conflicts of interest relevant to the content of this manuscript.

**Open Access** This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

References

Baker AJM, Brooks RR (1989) Terrestrial higher plants which hyperaccumulate metallic elements - a review of their distribution, ecology and phytochemistry. Biorecovery 1:81-126

Binnemans K, Jones PT, Blanpain B, Van Gerven T, Pontikes Y (2015) Towards zero-waste valorisation of rare-earth-containing industrial process residues: A critical review. J Clean Prod 99:17-38. https://doi.org/10.1016/j.jclepro.2015.02.089

Binnemansa K, Jones PT, Blanpain B, Van Gerven T, Yang Y, Walton A, Buchert M (2013) Recycling of rare earths: a critical review. J Clean Prod 51:1-22. https://doi.org/10.1016/j.jclepro.2012.12.037

de Gasper AL, de Dittrich VAO, Smith AR, Salino A (2016) A classification for *Blechnaceae* (*Polypodiales: Polypodiopsida*): New genera, resurrected names, and combinations. Phytotaxa 275:191. https://doi.org/10.11646/phytotaxa.275.3.1

de Gasper AL, Almeida TE, de Dittrich VA, O, et al (2017) Molecular phylogeny of the fern family Blechnaceae (*Polypodiales*) with a revised genus-level treatment. Cladistics 33:429-446. https://doi.org/10.1111/cla.12173

Ditusa SF, Fontenot EB, Wallace RW et al (2016) A member of the Phosphate transporter 1 (Pht1) family from the
arsenic-hyperaccumulating fern *Pteris vittata* is a high-affinity arsenate transporter. *New Phytol* 209:762-772. https://doi.org/10.1111/nph.13472

Do C, Abubakari F, Remigio AC et al (2020) A preliminary survey of nickel, manganese and zinc (hyper)accumulation in the flora of Papua New Guinea from herbarium X-ray fluorescence scanning. *Chemoecology* 30:1-13. https://doi.org/10.1007/s00049-019-00293-1

Gaustad G, Williams E, Leader A (2021) Rare earth metals from secondary sources: Review of potential supply from waste and byproducts. *Resour Conserv Recycl* 167:105213. https://doi.org/10.1016/j.resconrec.2020.105213

Gei V, Erskine PD, Harris HH, Echevarria G, Mesjasz-Przybyłowicz J, Barnabas AD, Przybyłowicz WJ, Kopittke PM, van der Ent A (2018) Tools for the discovery of hyperaccumulator plant species and understanding their ecophysiology. In: van der Ent A, Echevarria G, Baker AJM, Morel JL (eds) Agromining: Farming for Metals. Mineral Resource Reviews. Springer, Cham. https://doi.org/10.1007/978-3-319-61899-9_7

Golev A, Scott M, Erskine PD, Ali SH, Ballantyne GR (2014) Rare earths supply chains: Current status, constraints and opportunities. *Resour Policy* 41(1):52-59. https://doi.org/10.1016/j.resourpol.2014.03.004

Goudard L, Blaudez D, Sirguey C, Purwadi I, Invernon V, Rouhan G, van der Ent A (2024) Prospecting for rare earth element (hyper)accumulators in the Paris Herbarium using X-ray fluorescence spectroscopy reveals new distributional and taxon discoveries. *Ann Bot* 133(4):573-584. https://doi.org/10.1093/aob/mcae011

Grosjean N, Blaudez D, Chalot M et al (2019) Identification of new hardy ferns that preferentially accumulate light rare earth elements: a conserved trait within fern species. *Environ Chem* 17:191-200. https://doi.org/10.1071/EN19182

Gumaelius L, Lahner B, Salt DE, Banks JA (2004) Arsenic hyperaccumulation in gametophytes of *Pteris vittata*. A new model system for analysis of arsenic hyperaccumulation. *Plant Physiol* 136:3198-3208. https://doi.org/10.1104/pp.104.044073

Han Z, Edraki M, Nguyen AD, Mostert M (2021) Efficiency of acid digestion procedures for geochemical analysis of tungsten mining wastes. *Geochem Explor Environ Anal* 21(3). https://doi.org/10.1144/geochem2021-034

Indriolo E, Na GN, Ellis D et al (2010) A vacuolar arsenite transporter necessary for arsenic tolerance in the arsenic hyperaccumulating fern *Pteris vittata* is missing in flowinger plants. *Plant Cell* 22:2045-2057. https://doi.org/10.1105/tpc.109.069773

Khan AM, Bakar NKA, Bakar AFA, Ashraf MA (2017) Chemical speciation and bioavailability of rare earth elements (REEs) in the ecosystem: a review. *Environ Sci Pollut Res Int* 24:22764-22789. https://doi.org/10.1007/s11356-016-7427-1

Ko KU (1986) Preliminary synthesis of the geology of Bangka Island, Indonesia. *GEOSEA V Proceedings, Geological Society of Malaysia Bulletin* 20:81-96. https://doi.org/10.7186/bgsm20198606

Koyama M, Shirakawa M, Takada J et al (1987) Trace elements in land plants: Concentration ranges and accumulators of rare earths, Ba, Ra, Mn, Fe, Co and heavy halogens. J Radioanal Nucl Chem Artic 112:489-506. https://doi.org/10.1007/BF02132381

Liu WS, Zheng HX, Guo MN et al (2019) Co-deposition of silicon with rare earth elements (REEs) and aluminium in the fern *Dicranopterislinearis* from China. *Plant Soil* 437:427-437. https://doi.org/10.1007/s11104-019-04005-0

Liu WS, Van Der Ent A, Erskine PD et al (2020) Spatially Resolved Localization of Lanthanum and Cerium in the Rare Earth Element Hyperaccumulator Fern *Dicranopterislinearis* from China. *Environ Sci Technol* 54:2287-2294. https://doi.org/10.1021/acs.est.9b05728

Liu WS, Laird JS, Ryan CG et al (2021) Rare earth elements, aluminium and silicon distribution in the fern Dicranopteris linearis revealed by µpIXE Maia analysis. *Ann Bot* 128:17-30. https://doi.org/10.1093/aob/mcab026

Liu C, Ming Yuan, Liu W-S, Guo M-N, Huot H, Tang Y-T, Laubie B, Simonnot M-O, Morel JL, Qiu R-L (2018) Element case studies: Rare earth elements. In: van der Ent A, Echevarria G, Baker,AJM, Morel JL (eds) Agromining: Farming for Metals. Mineral Resource Reviews. Springer, Cham. https://doi.org/10.1007/978-3-319-61899-9_19

Ma LQ, Komar KM, Tu C et al (2001) A fern that hyperaccumulates arsenic. *Nature* 411:438-438. https://doi.org/10.1038/35078151

Mudd GM, Jowitt SM (2016) Rare earth elements from heavy mineral sands: assessing the potential of a forgotten resource. *Trans Inst Mining Metall, Section b: Applied Earth Science* 125(3):107-113. https://doi.org/10.1080/03717453.2016.1194955

Nkrumah PN, Echevarria G, Erskine PD, van der Ent A (2018) Correction to: Nickel hyperaccumulation in *Antidesmamontis-silam*: from herbarium discovery to collection in the native habitat. *Ecol Res* 33:1. https://doi.org/10.1007/s11284-018-1601-5

O'Neill HSC (2016) The smoothness and shapes of chondrite-normalized rare earth element patterns in basalts. *J Petrol* 57:1463-1508. https://doi.org/10.1093/petrology/egw047

Purwadi I, van der Werff H, Lievens C (2018) Reflectance spectroscopy and geochemical analysis of rare earth element-bearing tailings: A case study of two abandoned tin mine sites in Bangka Island, Indonesia. *Int J Appl Earth Obs Geoinf* 74:239-247. https://doi.org/10.1016/j.jag.2018.09.006

Purwadi I, Gei V, Echevarria G et al (2021a) Tools for the Discovery of Hyperaccumulator Plant Species in the Field and in the Herbarium. In: van der Ent A, Baker AJM, Echevarria G et al (eds) Agromining: Farming for Metals. Springer, Second, pp 183-195

Purwadi I, Nkrumah PN, Paul ALD, van der Ent A (2021b) Uptake of yttrium, lanthanum and neodymium in *Melastomamalabathricum* and *Dicranopterislinearis* from Malaysia. *Chemoecology* 31:335-342. https://doi.org/10.1007/s00049-021-00348-2

Purwadi I, Casey LW, Ryan CG et al (2022) X-ray fluorescence spectroscopy (XRF) for metallome analysis of herbarium specimens. *Plant Methods* 18:139. https://doi.org/10.1186/s13007-022-00958-z

Purwadi I, Abubakari F, Brown GK et al (2023) A systematic assessment of the metallome of selected plant families in
the Queensland (Australia) flora using X-ray flourescence spectroscopy. Aust J Bot. https://doi.org/10.1071/BT22028

Ramos SJ, Dinali GS, Oliveira C et al (2016) Rare Earth Elements in the Soil Environment. Curr Pollut Reports 2:28–50. https://doi.org/10.1007/s40726-016-0026-4

Reeves RD, Baker AJMM, Jaffré T et al (2017) A global database for plants that hyperaccumulate metal and metalloid trace elements. New Phytol 218:407–411. https://doi.org/10.1111/nph.14907

Ryan CG (2000) Quantitative trace element imaging using PIXE and the nuclear microprobe. Int J Imaging Syst Technol 11(4):219–230. https://doi.org/10.1002/ima.1007

Ryan CG, Etschmann BE, Vogt S, Maser J, Harland CL, Van Achterbergh E, Legnini D (2005) Nuclear microprobe - Synchrotron synergy: Towards integrated quantitative real-time elemental imaging using PIXE and SXRF. Nucl Instrum Methods Phys Res, Sect B 231(1–4):183–188. https://doi.org/10.1016/j.nimb.2005.01.054

Schuetpelz E, Schneider H, Smith AR et al (2016) A community-derived classification for extant lycophytes and ferns. J Syst Evol 54:563–603. https://doi.org/10.1111/jse.12229

Schwartz MO, Surjono (1991) The Pemali tin deposit, Bangka, Indonesia. Miner Depos 26:18–25. https://doi.org/10.1007/BF00202359

Schwartz MO, Rajah SS, Askury AK et al (1995) The Southeast Asian tin belt. Earth Sci Rev 38:95–293. https://doi.org/10.1016/0012-8252(95)00004-T

Setiawan I (2018) Towards the challenging REE exploration in Indonesia. IOP Conf Ser Earth Environ Sci 118:1–6. https://doi.org/10.1088/1755-1315/118/1/012075

Stein RJ, Höreth S, de Melo JRF et al (2017) Relationships between soil and leaf mineral composition are element-specific, environment-dependent and geographically structured in the emerging model Arabidopsis halleri. New Phytol 213:1274–1286. https://doi.org/10.1111/nph.14219

Syafrizal S, Hede ANH, Hakim AY Al, Permatasari MI (2021) Identifikasi Keberadaan Rare Earth Elements Tipe Ion Adsorption Pada Lempung: Sampel Dari Muntok Dan Lubuk Besar, Pulau Bangka. J GEOSAPTA 7:125. https://doi.org/10.20527/jg.v7i2.10897

Szamałek K, Konopka G, Zglinicki K, Marciniak-Maliszewska B (2013) New potential source of rare earth elements. Gospod Surowcami Miner - Miner Resour Manag 29:59–76. https://doi.org/10.2478/gospo-2013-0041

Taylor SR, McLennan SM (1995) The geochemical evolution of the continental crust. Rev Geophys 33:241. https://doi.org/10.1029/95RG00262

Tu C, Ma LQ (2005) Effects of arsenic on concentration and distribution of nutrients in the fronds of the arsenic hyper- accumulator Pteris vittata L. Environ Pollut 135:333–340. https://doi.org/10.1016/j.envpol.2004.03.026

Tyler G (2004) Rare earth elements in soil and plant systems – A review. Plant Soil 267:191–206. https://doi.org/10.1007/s11104-005-4888-2

United States Geological Survey (2023) Mineral Commodity Summaries 2023

van der Ent A, Baker AJM, Reeves RD et al (2013) Hyperaccumulators of metal and metalloid trace elements: Facts and fiction. Plant Soil 362:319–334. https://doi.org/10.1007/s11104-012-1287-3

van der Ent A, Echevarria G, Pollard AJ, Erskine PD (2019a) X-Ray Fluorescence Ionomics of Herbarium Collections. Sci Rep 9:4–8. https://doi.org/10.1038/s41598-019-40050-6

van der Ent A, Ocenar A, Tisserand R et al (2019b) Herbarium X-ray fluorescence screening for nickel, cobalt and manganese hyperaccumulator plants in the flora of Sabah (Malaysia, Borneo Island). J Geochemical Explor 202:49–58. https://doi.org/10.1016/j.gexplo.2019.03.013

van der Ent A, Nkrumah PN, Purwadi I, Erskine PD (2023) Rare earth element (hyper)accumulation in some *Proteaceae* from Queensland, Australia. Plant Soil 485:247–257. https://doi.org/10.1007/s11104-022-05805-7

Visoottiviseth P, Francesconi K, Sridokchan W (2002) The potential of Thai indigenous plant species for the phytoremediation of arsenic contaminated land. Environ Pollut 118:453–461. https://doi.org/10.1016/S0269-7491(01)00293-7

Wang Y, Brindle ID (2014) Rapid high-performance sample digestion for ICP determination by ColdBlockTM digestion: Part 2: Gold determination in geological samples with memory effect elimination. J Anal At Spectrom 29:1904–1911. https://doi.org/10.1039/c4ja00189c

Xie QE, Yan XL, Liao XY, Li X (2009) The arsenic hyper- accumulator fern *Pteris vittata* L. Environ Sci Technol 43:8488–8495. https://doi.org/10.1021/es9014647

Yuan M, Guo MN, Liu WS et al (2017) The accumulation and fractionation of Rare Earth Elements in hydroponically grown *Phytolaccaamericana* L. Plant Soil 421:67–82. https://doi.org/10.1007/s11104-017-3426-3

Zglinicki K, Szamałek K, Wolkowicz S (2021) Critical minerals from post-processing tailing. A case study from Bangka island, Indonesia. Minerals 11(4):352. https://doi.org/10.3390/min11040352

Zhao FJ, Dunham SJ, McGrath SP (2002) Arsenic hyperaccumulation by different fern species. New Phytol 156:27–31. https://doi.org/10.1046/j.1469-8137.2002.00493.x

Zhenggui W, Ming Y, Xun Z et al (2001) Rare earth elements in naturally grown fern *Dicranopterislinearis* in relation to their variation in soils in South-Jiangxi region (Southern China). Environ Pollut 114:345–355. https://doi.org/10.1016/S0269-7491(00)00240-2

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