How Does Ambrosia artemisiifolia L. Bioaccumulate and Translocate Cr, Cu, Pb, As, Cd, Hg, and Zn in Polluted Soils?

Abstract

The present study is aimed at assessing the bioaccumulation and translocation of Cr, Cu, As, Cd, Hg, Pb and Zn in the soil–plant system (Ambrosia artemisiifolia L.) and characterising soil contamination in the anthropogenic zone of Dnipro, a major industrial and economic centre of Ukraine, using inductively coupled plasma atomic emission spectrometry. Analysis of the obtained values of the geoaccumulation index and enrichment factor showed that the sources of origin differ between the studied plots, with some plots showing natural origin and others showing anthropogenic origin. Ambrosia artemisiifolia L. can be recommended for phytoextraction of soils contaminated with Zn, Cu, and Cr, as well as for phytostabilization of soils contaminated with Pb.

1. Introduction

Industrial development and urbanisation of many countries, including Ukraine, during the last decades have been accompanied by significant anthropogenic impact on environmental components. The problem is particularly acute in large industrial centres, where metallurgy, energy, machine building, chemical, and battery industries are concentrated [1,2,3,4,5,6,7]. One such centre is the city of Dnipro, one of the largest industrial hubs in Eastern Europe, where the industrial load on the soil and atmosphere is formed both by existing production facilities and by the accumulated industrial heritage.

Research conducted in recent years has shown that man-made emissions from ferrous and non-ferrous metallurgy enterprises, thermal power plants, battery production and processing, as well as dust from slag heaps, are key sources of heavy metals (HMs) entering the environment [2,3,4].

The city of Dnipro, located in the south-eastern part of the country, is one of the largest industrial centres in Ukraine and Eastern Europe, populated by approximately 1 million people. The city is home to key industries such as ferrous metallurgy, chemical production, machine building and construction materials production, battery manufacturing, and waste battery recycling, which contribute significantly to environmental degradation, affecting soil and air quality [8,9].

The accumulation of HMs in soils has become a global environmental problem that directly affects crop productivity and food security. Ukrainian chernozem soils, which are most common in the Dnipro region, are of global strategic importance, accounting for about 62% of all agricultural land in Ukraine [5,8,9]. Together with chernozems in other regions, they are a key resource for ensuring global food security. That is why even slight contamination of these soils with HMs can lead to a sharp decline in crop yields and deterioration in food quality.

HMs and metalloids are characterised by high chemical stability, toxicity, and bioaccumulation potential [10,11,12,13,14]. Their accumulation in the soils of industrial areas poses a risk not only to plant communities and soil biota, but also to human health due to the migration of pollutants into food chains [10,11]. At the same time, a significant portion of pollutants may be in bioavailable forms, which increases the likelihood of their inclusion in the biological cycle [12].

Figure 1 presents the plant’s basic principles of HMs bioavailability and bioaccumulation.

One of the current methods for minimising the concentration of HMs in contaminated soil is phytoremediation, which includes the use of plants to extract, fix, or transform pollutants [15]. The successful implementation of phytoremediation technologies requires the selection of species with high resistance to the toxic effects of metals, the ability to grow rapidly, and significant biomass-forming capacity [16,17,18].

Ambrosia artemisiifolia L (A. artemisiifolia) is an annual invasive species of North American origin that is widespread in Ukraine, including in areas with high anthropogenic pressure [19,20,21,22,23]. In addition to being a strong allergen [24], A. artemisiifolia is officially recognised as a dangerous quarantine weed in many countries, including Ukraine and some EU member states. It displaces native plant species, severely inhibits the growth of cultivated plants and causes significant damage to agriculture. This species demonstrates high ecological plasticity, resistance to heavy metal pollution and the ability to form dense cenopopulations even on degraded substrates [20,21,22,23,25]. Studies have shown that this species is capable of accumulating Zn, Pb, and Cu in conditions of roadside and industrial pollution [26], which allows it to be considered as a potential phytoremediation agent, especially in post-industrial landscapes [27,28,29,30,31,32].

This study aims to assess the accumulation and transformation of HMs in A. artemisiifolia in the industrial zone of Dnipro, surrounded by battery manufacturing and recycling facilities, taking into account both the total and mobile content of metals in soils. The results will allow for assessing the potential of this species in phytoextraction and phytostabilization strategies in urbanised and post-industrial areas of Ukraine.

Furthermore, in the context of Ukraine’s black soil, which is of global strategic importance for food safety, this is the first study of the bioaccumulative properties of A. artemisiifolia. in the soil–plant system.

The accumulation of HMs in plants can have indirect effects on both human health and environmental quality. Considering the ongoing military actions in Ukraine due to Russian aggression, which may affect the environment, including the study area, studies of the soil–plant system become even more important. And the results of our research can be used for monitoring HM pollution and mitigation of pollution effects in the ecosystems of the region.

2. Materials and Methods

In the summer of 2021, the concentrations of Hg, Cr, Zn, As, Cd, Pb, and Cu in soil and A. artemisiifolia were investigated at three experimental plots situated 1.00 km, 5.5 km, and 12.02 km from major sources of pollution (battery manufacturing and recycling facilities) in Dnipro, Ukraine. The conditions and locations of sampling are shown in [33] and Figure 2.

It is important to recognise that all investigated sites are subjected to a cumulative burden of anthropogenic emissions originating from multiple sources, beyond those identified as the primary contributors. For instance, plot 1 lies in the vicinity of the Northern Industrial Zone, where facilities for the collection and preliminary processing of ferrous and non-ferrous scrap metal are located (approximately 0.5–1.0 km to the west). Plot 2 is positioned 2.0–2.5 km south of the slag deposits of the Prydniprovska Thermal Power Plant, whereas plot 3 is situated 3.3 km north-west of the Novomoskovsk Pipe Plant and 50 m north of the M04 (E50) highway. Such additional emission sources may introduce confounding factors, leading to spatial heterogeneity in heavy metal accumulation within soils and plants, and consequently need to be considered when interpreting the results of this study.

Future field studies need to consider these aspects and use techniques to minimise potential errors, such as modelling atmospheric deposition of pollutants or analysing chemical markers to identify individual sources, etc. Overall, the study area has been significantly altered by human activity [34].

Soil samples and A. artemisiifolia were collected in summer 2021 (before the full-scale invasion of Ukraine by Russia) in accordance with the requirements of Ukrainian state standards [35]. Soil sampling was conducted within a 10 × 10 m (100 m²) plot using an envelope design: subsamples were taken at the four corners and the centre (five per plot), composited, and this procedure was performed in four independent replicates. Sampling depth was 0–20 cm, and each composite sample weighed 1.0–1.2 kg. In parallel, twenty plant specimens were collected separately at three soil-sampling locations. The study area soils are ordinary, low-humus chernozems developed on heavy loess loam, with pH 6.7 and organic-matter content of 4.4% (as determined by the Turin and Walkley–Black methods). According to the U.S. Soil Taxonomy [36], chernozems are classified within the Mollisols order.

In this study, two analytical procedures were applied depending on the research objective. Total metal content (C_TF) in soils and plant material was determined after complete mineralization of dried and homogenised samples—0.5 g for soil samples and 1.0 g for plant samples—with a mixture of concentrated HNO₃ and H₂SO₄, followed by analysis using inductively coupled plasma atomic emission spectrometry (ICP-AES; iCAP 7000 Plus DUO, Thermo Fisher Scientific, Bremen, Germany) in accordance with internationally recognised protocols (ISO 11466:1995; USEPA 3052:1996). Mobile metal forms (C_MF) in soils were determined by extraction with 1 M ammonium acetate buffer (pH 4.8) at a soil-to-solution ratio of 1:10 (w/v) at room temperature, with continuous shaking for 30 min. Extracts were filtered through ashless filter paper and analysed by the same ICP-AES method. This procedure is designed to assess the bioavailable fraction of metals, which is ecologically relevant and correlates with potential uptake by plants and soil organisms. Certified reference materials for mobile metal forms in chernozem soils and for the specific plant matrix A. artemisiifolia are not available in international CRM databases. Therefore, accuracy and precision were evaluated using alternative quality-control approaches, including analysis of its own control samples with known element concentrations, use of certified multi-element standard solutions for instrument calibration, monitoring calibration stability and signal drift during analytical runs, and triplicate measurements of each sample (calibration certificate №UA/37/211004/001533). For all elements, repeatability (RSD) was <10 %.

The method detection limits for Cr, Cu, Pb, Zn, As, Cd and Hg in soil were 1.0, 0.5, 0.2, 1.0, 0.5, 0,2 and 0.2 µg kg⁻¹, respectively. For plant tissues, the corresponding detection limits were 4.0, 2.0, 10.0, 4.0, 0.1, 0.8 and 0.1 µg kg⁻¹, respectively. Hg concentrations were consistently below the detection threshold, while Cd and As were only sporadically detected in soil and plant samples; therefore, these elements were excluded from subsequent data interpretation and analysis.

The following factors were considered to assess the bioavailability and phytoremediation potential of plant species:

Plant uptake index (PUI) of a HMs [30]:

PUI = C_plant/C_soil,

(1)

where PUI is the plant uptake index;

C_plant—concentration of metal in the total plant (dry matter), mg kg⁻¹;

C_soil—concentration of metal in the available form in the soil, mg kg⁻¹.

Bioabsorption coefficient (BAC) [33]:

BAC = C_shoot/C_soil,

(2)

where BAC is the bioabsorption coefficient;

C_shoot—concentration of metal in the vegetative and generative parts of the plant (dry matter), mg kg⁻¹;

C_soil—concentration of metal in the available form in the soil, mg kg⁻¹.

Bioconcentration factor (BCF) [33]:

BCF = C_root/C_soil,

(3)

where BCF is the bioconcentration factor;

C_root—concentration of metal in the underground part of the plant (dry matter), mg kg⁻¹;

C_soil—concentration of metal in the available form in the soil, mg kg⁻¹.

To assess the efficiency of the plant in translocating HMs from the roots to other parts of the plant, such as the inflorescence, stem, and leaves, the Translocation factor (TF) was calculated as follows [30]:

TF = C_shoot/C_root,

(4)

where TF—translocation factor;

C_shoot—concentration of metal in the vegetative and generative parts of the plant (dry matter), mg kg⁻¹;

C_root—concentration of metal in the root (dry matter), mg kg⁻¹.

These ratios are crucial for evaluating the effectiveness of plants in phytoextraction and phytostabilization by analysing how metals accumulate and move within the plants.

The mobility of HMs is an indicator that allows for the assessment of the possibility of heavy metals’ transfer from total forms to mobile forms available to plants. The mobility of HMs in the soil was evaluated using the availability ratio index (AR), calculated according to Formula [33]:

AR (%) = C_MF × 100/C_TF.

(5)

where AR is the availability ratio index;

C_MF—concentration of metal in the mobile form in the soil, mg kg⁻¹;

C_TF—concentration of metal in the total form in the soil, mg kg⁻¹.

The geoaccumulation index (Igeo), used to assess the intensity of anthropogenic pollution on the soil surface, was calculated as follows [37]:

Igeo = ln C _i/1.5× B_i,

(6)

where C_i is the measured concentration of the element in the soil,

B_i represents the geochemical background value, and the constant 1.5 is included to account for natural variations in the concentration of the substance in the environment, enabling the detection of even slight anthropogenic impacts. For B_i, we used the regional geochemical baseline concentrations for Ukrainian soils reported by [38]. The classification of Igeo values followed Muller’s original scale [39]:

class 0: Igeo ≤ 0—unpolluted;

class 1: 0 < Igeo ≤ 1—unpolluted to moderately polluted;

class 2: 1 < Igeo≤ 2—moderately polluted;

class 3: 2 < Igeo≤ 3—moderately to strongly polluted;

class 4: 3 < Igeo≤ 4—strongly polluted;

class 5: 4 <Igeo ≤ 5—strongly to extremely polluted;

class 6: Igeo> 5—extremely polluted.

The Enrichment factor (EF), an indicator used to evaluate the presence of anthropogenic pollution in soil, is expressed as follows [37]:

EF = (C_i/C_RE) _soil/(C_i/C_RE) _background,

(7)

where C_RE represents the metal content chosen as a reference element.

A reference element is an element that remains highly stable in the soil and is characterised by the absence of vertical mobility and/or degradation processes. Commonly used reference elements in various studies include Al, Fe, Mn, and Rb [40]. In our study, Al was selected as the reference element.

The EF classification for soils according to [41]:

EF < 2—minimal enrichment;

2 ≤ EF < 5—moderate enrichment;

5 ≤ EF < 20—significant enrichment;

20 ≤ EF < 40—very high enrichment;

EF ≥ 40—extremely high enrichment.

Experimental data were processed using standard statistical methods. Basic statistical parameters, such as mean square deviation, variance, and standard error, were calculated using Microsoft Excel. Fisher’s F-test was used to assess the homogeneity of differences between samples. One-way analysis of variance (ANOVA) was used to assess statistically significant differences between samples, and Tukey’s HSD test was used for consistent comparison of mean values.

3. Results and Discussion

3.1. Soil

The determination of EF and Igeo indicators in the studied soils allows us to identify potential metal groups based on common principles, helps to identify possible sources of contamination and assess contamination levels, and assists in the selection of plants for specific phytoremediation mechanisms [42].

Table 1. The concentration of HMs mobile forms (C_MF), HMs total concentration (C_TF), mobility ratio (AR), enrichment factor (EF), and geoaccumulation index (Igeo).

Indicator	Locations	Cr	Cu	Pb	Zn
CTF, mg kg−1	P1	2219.0 ± 177.5 a	1039.0 ± 98.76 a	7830.0 ± 720.36 a	1918.0 ± 230.16 a
	P2	36.51 ± 4.02 bc	15.42 ± 1.33 bc	4.53 ± 0.41 bc	14.29 ± 1.55 bc
	P3	21.21 ± 2.6 bc	5.66 ± 0.6 bc	10.03 ± 1.26 bc	15.11 ± 1.48 bc
Bi *, mg kg−1		49.0	19.3	10.0	53.0
CMF, mg kg−1	P1	1.65± 0.24 a	1.80 ± 0.19 ab	48.96 ± 4.12 bc	20.67 ± 1.88 a
	P2	0.17 ± 0.02 bc	0.16 ± 0.01 ab	0.53 ± 0.05 bc	0.67 ± 0.06 b
	P3	0.89 ± 0.17 bc	0.28 ± 0.05 c	2.72 ± 0.52 a	4.73 ± 0.91 c
AR, %	P1	0.07	0.17	0.63	1.08
	P2	0.47	1.04	11.7	4.69
	P3	4.2	4.95	27.12	31.3
Igeo	P1	2.78	2.88	5.73	2.95
	P2	−1.33	−1.33	−1.73	−1.95
	P3	−1.87	−2.34	−0.93	−1.9
EF	P1	2.58	3.07	44.67	2.06
	P2	0.04	0.05	0.03	0.02
	P3	0.03	0.02	0.06	0.02

Different small letters indicate significant differences (p < 0.05) between plant parts in the concentration of metals according to Tukey’s test (n = 3). *—data taken accordingly [38].

shows the results from the three experimental plots.

The geoaccumulation index (Igeo) was used to detect and determine the concentration of metals in soils by comparing modern concentrations with pre-industrial levels [38,39]. According to the obtained Igeo values for Cr, Cu, Pb, and Zn in soil (total concentration), the studied plots P2 and P3 fall into the first group and are classified as unpolluted (Igeo ≤ 0). In plot P1, Igeo values for Cr, Cu, and Zn were higher, indicating moderate to heavy pollution (2 < Igeo ≤ 3). The highest Igeo values were found for Pb, with a maximum value of 5.73, which indicates extreme pollution (Igeo > 5) at plot P1.

The Igeo values obtained for each metal in the soil at the study plots correlate with the previously determined contamination factor (CF) values [33]. Based on the Igeo values, the metals at all study plots are ranked as follows (by median, in descending order): Pb > Cr > Cu > Zn.

The enrichment factor (EF) for metals is an indicator used to assess the presence and intensity of anthropogenic deposition of pollutants on the soil surface. Based on the EF calculation, any EF value > 2 can be considered as a possible enrichment of the soil with the corresponding metal.

At plots P2 and P3, the EF values for all studied metals were less than 1, which may indicate their natural origin. At research plot P1 (1.0 km from the main pollution sources), the variability of EF values for Cr, Cu, and Zn was higher, reaching values greater than 2 (EF-2.06 for Zn, 2.58 for Cr, and 3.07 for Cu), indicating an anthropogenic source of pollution ranging from moderate to small. The highest EF values were determined for Pb (the maximum EF value was 44.67 at P1), indicating an anthropogenic source of lead entering the soil and classified as extremely high pollution.

The EF values for HMs at the research plots follow the descending order: Pb > Cr > Cu > Zn, which corresponds to the values obtained for other indicators.

Based on the results, the HMs content in soils at study plots P2 and P3 can be characterised as natural for Cr, Cu, Pb, and Zn, while for all metals at study plot P1, it is anthropogenic. Certain values for Cr, Cu, Zn, and especially for Pb are concerning and require further research.

3.2. Plant, Bioaccumulation and Translocation

For all experimental plots, the concentrations of HMs in A. artemisiifolia and its organs (root, stem, leaves, and inflorescence) were determined, and the results are provided in the Supplementary Materials (Table S1).

The plant’s content showed different absorption capacities of its parts for HMs from the soil at three research plots. Based on the content of the studied elements in the plant (dry matter), they can be ranked as follows: P1: Zn > Cu > Pb > Cr; P2 and P3: Zn > Cu > Cr > Pb.

The accumulation pattern of HMs observed in plant does not conform to the accumulation pattern in soil (as mobile and total forms), which may indicate various pathways of these metals entering plants.

The general trend of the studied elements accumulation in all parts, as in the whole plant, as well as in parts of A. artemisiifolia: Zn > Cu > Cr > Pb, which is consistent with the accumulation observed in the plant in previous studies [26,29,30,31,32].

Cr is not easily accessible to plants and cannot be easily translocated within the plant, so it tends to accumulate primarily in the roots [43,44].

In all research plots, Cr accumulation in A. artemisiifolia occurred in the following sequence: roots, leaves, inflorescences, and stem, with the highest total chromium content in the plant observed in plot P3 (19.22 ± 1.75 mg kg⁻¹). In general, the accumulation levels correspond to the results of previous studies, including ours, and do not exceed the recommended level of absorption by plants, which is 300 mg kg⁻¹ [14].

The accumulation of Cr detected in A. artemisiifolia indicates different pathways of uptake (by roots and leaves). (Table S1). Cr, Cu, Pb, and Zn were detected in all parts of the plant in all experimental plots. Summary data on their bioaccumulation and translocation are presented in

Table 2. Indicators of heavy metals bioaccumulation and translocation in A. artemisiifolia.

Metals	Plots	PUI	BAC	BCF	TF Shoot/Root	TF Inflorescence/Root	TF Leaf/Root	TF Stem/Root
Cr	P1	5.25	2.62	2.63	0.99	0.33	0.37	0.3
	P2	67.38	31.09	36.29	0.88	0.4	0.28	0.2
	P3	21.69	12.27	9.42	1.48	0.15	1.08	0.25
Cu	P1	48.63	33.35	15.28	2.18	0.78	1.1	0.3
	P2	411.73	289.73	122.0	2.38	0.91	1.03	0.44
	P3	216.7	125.16	91.54	1.34	0.53	0.64	0.17
Pb	P1	0.67	0.08	0.59	0.12	0.03	0.08	0.02
	P2	6.97	2.95	4.02	0.73	0.25	0.23	0.26
	P3	1.89	0.74	1.15	0.64	0.14	0.37	0.13
Zn	P1	17.09	9.62	7.47	1.29	0.25	0.56	0.48
	P2	672.18	548.36	123.82	4.44	1.37	2.24	0.83
	P3	106.81	75.41	31.4	2.4	0.86	1.15	0.39

Values greater than 1 are bold.

.

The second plot recorded the highest PUI value (67.38), whereas the mobile Cr concentration in the soil (0.17 ± 0.02 mg kg⁻¹) and the translocation factor (TFshoot/root = 0.88 < 1) were the lowest among all experimental plots. For A. artemisiifolia, the highest translocation factor (TF shoot/root = 1.48) was observed in plot P3 (located 12.02 km from the main sources of pollution and 50 m from the E50 motorway), where the highest availability ratio (AR = 4.20%) was also noted.

The ratio of Cr concentration in shoots to roots ranges between 0.005 and 0.027 for vegetable plants and between 0.1 and 0.6 for herbaceous plants [14], showing a low TF index, which limits the usability of most species for phytoremediation. In contrast, our findings on Cr bioaccumulation and translocation in A. artemisiifolia suggest its potential applicability in both phytostabilization (PUI > 1; TF < 1) and phytoextraction (PUI > 1; TF > 1) strategies for Cr-contaminated soils.

Cu is an important element for plants and animals, playing a vital role in numerous physiological processes. Nevertheless, excessive Cu concentrations may exert toxic effects on soil organisms, thereby impairing their growth and disrupting the overall soil ecosystem [13]. The critical Cu concentration in plant roots is reported to range from 100 to 400 mg kg⁻¹ dry matter [13]. In our previous studies, Cu concentrations in common plant species were found to range from 1.57 to 22.05 mg kg⁻¹ [33].

In the present study, the distribution of Cu in different parts of A. artemisiifolia (dry matter) followed the pattern P1—leaves > roots > flowers> stem; P2—leaves > roots > flowers > stem; and P3—roots > leaves > flowers > stem, indicating that both root and foliar pathways contribute to Cu uptake in this species (Table S1).

As a rule, Cu is immobile in plants and gradually accumulates over time [13] due to its strong binding with nitrogen and proteins. Cu toxicity and reduced growth were observed at concentrations in shoots and leaves ranging from 5 to 40 mg kg⁻¹ dry weight [14], which is lower than the Cu levels observed in A. artemisiifolia in this study (59.88–87.34 mg kg⁻¹ dry weight).

For Cu, both PUI and TFshoot/root values exceeded 1 in all experimental plots, indicating high bioavailability and bioaccumulation, and thereby suggesting the potential use of A. artemisiifolia in phytoremediation strategies [19]. The highest PUI value (411.73) was observed at site P2, which was also characterised by the lowest mobile Cu content in soil (0.16 ± 0.02 mg kg⁻¹) and the highest TFshoot/root ratio (2.38) among all sites.

Essential trace elements (Zn, Cu) were found in higher concentrations than toxic elements (Pb, Cd), which is consistent with previous reports indicating rapid translocation of Zn and Cu and slow translocation of Pb [14].

Analysis of the TFshoot/root also showed that at low concentrations of heavy metals, their translocation increases.

Similarly to E. canadensis [33], A. artemisiifolia exhibited a decreasing plant uptake index with increasing concentrations of mobile Cu in the soil. Nevertheless, the translocation factor (TFleaf/root) remained greater than 1. These findings on Cu bioavailability, bioaccumulation, and translocation suggest the potential application of A. artemisiifolia in phytoextraction strategies for Cu-contaminated soils (PUI > 1; TF > 1).

The average Pb content in plants is estimated to be in the 5 to 7 mg kg⁻¹ range [14], and does not play any role in plant processes.

In our study, Pb accumulation in A. artemisiifolia followed the order: roots > leaves > inflorescences > stems. The highest total Pb accumulation was recorded at site P1 (1 km from the main sources of pollution), reaching 32.57 ± 3.87 mg kg⁻¹, with the maximum root concentration also observed at P1 (28.98 ± 2.75 mg kg⁻¹).

As reported in [13], Pb uptake by roots is typically slow and long-lasting, with limited internal translocation, leading to significant accumulation in the root system. At the same time, numerous studies have shown that atmospheric deposition also contributes to increased Pb levels in vegetation [45,46,47,48], as Pb from the air can be taken up by leaves directly [14].

The interaction between the content of HMs in the atmosphere and their content in the above-ground parts of plants should be further studied and researched.

The highest values of the plant uptake index (PUI = 6.97) and the translocation factor (TFshoot/root = 0.73) among all experimental plots were recorded at site P2, where the lowest concentration of mobile Pb in the soil (0.53 mg kg⁻¹) was detected. Consistent with the trends observed for Cr and Cu, PUI values decreased with increasing concentrations of mobile Pb in soil. Moreover, the highest availability ratio (AR = 27.12%) was found at site P3.

Based on their ability to accumulate Pb, plants are generally classified into two groups: excluders, which retain Pb primarily in their roots and are suitable for phytostabilisation strategies (TF < 1), and hyperaccumulators, which store Pb in their vegetative tissues without visible metabolic damage and are suitable for phytoextraction strategies (TF > 1) [49,50]. Our findings indicate that A. artemisiifolia displays Pb accumulation characteristics consistent with phytostabilisation of Pb-contaminated soils, in agreement with previous studies [26,27,28,29,32].

Zn is generally considered highly mobile in most soil types [13]. In contaminated areas, its concentrations—together with those of other elements—may reach substantial levels, ranging from 443 to 1112 mg kg⁻¹ [14], which is consistent with the total Zn content recorded at sites P2 and P3 in the present study (Table S1). According to [51], the average Zn concentration in plant shoots (dry weight) required for normal growth is about 20.0 mg kg⁻¹, while toxic effects may appear when levels exceed 300–400 mg kg⁻¹ [14].

Our study showed that the highest Zn concentration in A. artemisiifolia was observed at site P3, reaching 505.52 mg kg⁻¹ (dry matter), corresponding to a mobile Zn content of 4.73 mg kg⁻¹ in the soil. The overall distribution pattern of Zn among plant organs was as follows: roots > leaves > inflorescences > stems.

A. artemisiifolia demonstrated the capacity to bioaccumulate bioavailable Zn, highlighting its potential application in phytoremediation strategies. Across all study sites, both Zn PUI and TF values declined with increasing concentrations of mobile Zn in the soil.

It is evident that Zn was the most bioavailable element for A. artemisiifolia across all experimental plots, consistent with [52,53]. The observed values ranged as follows: Zn content in plants, 353.27–505.52 mg kg⁻¹; PUI, 17.09–672.18; and translocation coefficient, 1.29–4.44 (Table 2).

The proportion of Zn in the total plant biomass (dry matter) was 3.53% at P1, 5.52% at P2, and 5.06% at P3. According to some estimates, values exceeding 3.0% may indicate economic feasibility when using plants for phytoextraction of contaminated soils [54].

By Fisher’s F-test, the concentrations of Zn and Cu in A. artemisiifolia and its organs were significantly higher than the concentrations of other elements in all experimental plots (Ftheor < Fexp, p < 0.05). Moreover, the content of these elements in plant tissues was significantly greater than in their mobile soil forms (Ftheor < Fexp, p < 0.05), suggesting high bioavailability of Zn and Cu, more efficient translocation within the plant, and the potential contribution of foliar uptake pathways.

In summary, considering its specific physiological traits and the environmental conditions of the study sites, A. artemisiifolia can be regarded as a potential candidate for phytostabilisation of Pb and for phytoextraction of Zn, Cu, and Cr from contaminated soils.

Effective phytoextraction typically requires hyperaccumulator plants that meet several criteria: (1) a translocation factor (TF) greater than 1 [55]; (2) a plant uptake index (PUI) greater than 1 [56]; and (3) metal concentrations in shoots exceeding 1000 mg kg⁻¹ for Cu, Cr, and Pb, and 10,000 mg kg⁻¹ for Zn [57]. However, the practical application of such species is often limited by soil physicochemical properties, climatic conditions, plant growth rate, accumulation time, and element-specific characteristics [58]. Within this framework, A. artemisiifolia satisfies the first two criteria, underscoring its partial suitability for phytoextraction purposes.

According to our results, the total phytomass (dry matter) of A. artemisiifolia contained the following metal concentrations: Zn—P1: 3.53%, P2: 5.52%, P3: 5.06%; Cu—P1: 0.87%, P2: 0.66%, P3: 0.60%; Pb—P1: 0.33%, P2: 0.04%, P3: 0.05%; Cr—P1: 0.09%, P2: 0.12%, P3: 0.19%. This species is fast-growing, demonstrates sufficient biomass productivity [24,25], and has shown the ability to accumulate heavy metals under different levels of contamination (Table 1) as well as to redistribute these elements to both vegetative and generative organs (Table S1).

Thus, considering our results and the criteria for hyperaccumulator plants proposed in [55,56,57,58], A. artemisiifolia can be classified as a accumulator of Zn, Cu, and Cr and can be recommended for phytoextraction of soils contaminated with these elements.

The ability of A. artemisiifolia to retain Pb in root tissues supports its potential application for phytostabilisation of Pb-contaminated soils. According to the results obtained, this species demonstrates the capacity to accumulate Zn and Pb at levels consistent with recommended economic efficiency thresholds [54]. Under comparable experimental conditions and in soils with varying degrees of heavy metal contamination, A. artemisiifolia has also shown enhanced tolerance to pollutants [21,22].

A. artemisiifolia is an invasive species known to exert significant environmental impacts, including suppression of crop yields and displacement of native plant populations. Nevertheless, its use as a stable raw material for the production of biogas, methane or hydrogen is a potential strategy for meeting current energy needs, reducing dependence on irreplaceable carbon sources and alleviating the environmental risks associated with invasive plants. The biomass of A. artemisiifolia has the potential to serve as an efficient substrate for anaerobic fermentation and methane generation [59].

Therefore, this species may be considered as having potential for diversified and integrated applications. Moreover, under current conditions of increased anthropogenic pressure, including the ongoing military conflict in Ukraine, it becomes evident that a single phytoremediation strategy may not ensure sufficient effectiveness for the remediation of heavy metal-contaminated soils. A more comprehensive approach, combining genetic engineering, microbial assistance, and the use of chelating agents, will likely be required to establish efficient and adaptive phytoremediation systems in the future [60].

4. Conclusions

The calculated Igeo and EF indices indicate that Cr, Cu, Zn, and Pb are the predominant anthropogenic pollutants in the study area, with contamination levels ranging from unpolluted to heavily polluted and the highest values being observed for Pb. A. artemisiifolia was found to effectively accumulate heavy metals (Pb, Zn, Cu, and Cr) in the Dnipropetrovsk area, a region characterised by long-term anthropogenic impact. Under such conditions, ragweed exhibited tolerance to elevated concentrations of soil pollutants, including mobile forms, demonstrating its ability to adapt to stressful environments while maintaining visible growth and vitality.

The highest metal concentrations were found in the above-ground biomass, indicating a pronounced phytoextraction potential, particularly for Zn, Cr, and Cu (TF > 1). In contrast, a considerable fraction of Pb accumulated in the root system, suggesting its suitability for phytostabilization. This distribution pattern highlights the potential for a differentiated application of ragweed in phytoremediation: harvesting the aerial parts would enable the effective removal of Zn, Cr, and Cu from the system, whereas retaining the root biomass would promote Pb immobilisation in the soil.

From a practical perspective, A. artemisiifolia may serve as an auxiliary component of integrated phytoremediation strategies in urbanised and post-industrial environments. Its wide distribution, ecological plasticity, and tolerance to heavy metal pollution make this species suitable for remediation scenarios where conventional phytoremediators are less effective. Nevertheless, its allergenic properties and associated public health risks necessitate strict management, including restriction of uncontrolled spread and mowing before flowering.

Future integration of A. artemisiifolia into land remediation programmes in Dnipro and comparable regions should be supported by regular monitoring of metal bioaccumulation, evaluation of secondary environmental risks, and application of agronomic practices enhancing the uptake of the studied elements. Overall, the findings provide a scientific basis for employing ragweed in urban phytoremediation and support the development of environmentally sound strategies for the management of contaminated landscapes.