Pusz et al. 2024 — Brown coal and activated carbon stabilization of Pb, Cd, Cr, Zn, Cu, Ni in Polish industrial-waste soils planted with Medicago falcata

Pusz and colleagues compared two carbon-based soil amendments, brown coal and activated carbon at single (200 g per 10 kg soil) and double (400 g per 10 kg soil) doses, for their ability to immobilize Pb, Cd, Cr, Zn, Cu, and Ni in five Polish industrial-waste soils and to reduce uptake of those metals by Medicago falcata L. roots and shoots. Activated carbon outperformed brown coal at both doses on every metal in EDTA-extractable form and in plant-tissue concentration. Both amendments eliminated the 21–44% root-growth inhibition and 0–25% shoot-growth inhibition observed on the unamended polluted soils. The paper also reports Pollution Index (PI), Pollution Load Index (PLI), non-carcinogenic Hazard Quotient (HQ), and carcinogenic Individual Lifetime Cancer Risk (ILCR) for soil-borne exposure before and after amendment. The source is a single pot-experiment trial on industrial-waste soils with one test plant and one vegetation cycle; it is primary remediation and phytotoxicity evidence, not food, ingredient, or consumer-product occurrence evidence.

Key numbers

The pot experiment used five soil origins (SC plus S1–S4) from a metallurgical-cart cleaning heap at Krzemionki Opatowskie, Poland, four carbon-amendment treatments, and untreated baselines, yielding 21 soil-amendment combinations in triplicate. Wagner-type pots (0.25 m height, 0.22 m diameter) held 10 kg of soil each. Medicago falcata L. was grown one vegetation cycle (March–November) at 60% field capacity soil moisture and 20 °C; NPK fertilizers were applied. Replication was three per soil-amendment combination; coefficient of variation was kept at ≤10% (page 4).

Carbon characteristics, page 6. Brown coal pH 5.4 (1 M KCl) / 5.9 (demineralized water), dry matter 65.69%. Activated carbon pH 9.5 / 9.8, dry matter 94.04%.

Starting soils

Table 1, page 6 — Baseline soil chemistry before pot setup.

SC has sandy-loam granulometry; S1–S4 are loamy sand. All soils are alkaline. Sample depth 0–0.25 m below ground level (page 6).

Table 2, page 6 — Total metal concentrations in starting soils (mg·kg⁻¹ d.m., mean ± SD over triplicate):

Against the Polish soil-quality ordinance cited as ref [47] (industrial-area limits: Pb 600, Zn 2000, Cd 15, Cu 600, Cr 1000, Ni 500 mg·kg⁻¹ d.m.), Pb exceeds in all four contaminated soils (S1–S4), Zn exceeds in S1 and S2, Cu exceeds only in S1, and Cd, Cr, and Ni do not exceed in any soil (page 6).

Figure 3, page 8 — Pollution Load Index (PLI) banded against residential (group I) and industrial (group IV) area benchmarks. PLI bands: 0 background; 0–1 unpolluted; 1–2 unpolluted to moderately; 2–3 moderately; 3–4 moderately to highly; 4–5 highly; >5 very highly. Residential-benchmark PLI for S1: Cu 3.0, Pb 18.7, Zn 10.4, Cd 5.5, Cr 1.4, Ni 0.8 (very highly polluted on Pb, Zn, Cd). Industrial-benchmark PLI for S1: Cu 1.0, Pb 6.2, Zn 2.6, Cd 0.7, Cr 0.3, Ni 0.3 (extremely polluted on Pb, moderately on Zn). PLI declines monotonically S1 > S2 > S3 > S4 across all six metals.

Total soil metals after carbon amendment

Table 3, page 7 — Total metal concentrations after amendment (mg·kg⁻¹ d.m.). The amendments did not change total metal content beyond analytical variation. Treatment codes: bc1 = single brown-coal dose (200 g / 10 kg), bc2 = double brown-coal dose (400 g / 10 kg), ac1 = single activated-carbon dose (200 g / 10 kg), ac2 = double activated-carbon dose (400 g / 10 kg).

EDTA-extractable (phytoavailable) metals and risk indices

The authors used 0.02 M EDTA single-extraction to estimate plant-available metal forms. The SC control soil post-extraction residuals were Cu 3.11, Pb 5.63, Zn <0.05, Cd <0.005, Cr <0.03, Ni <0.05 mg·kg⁻¹ d.m. (page 9).

Table 4, page 9 — EDTA-extractable concentrations across the 21 combinations (mg·kg⁻¹ d.m., ranges across treatments within each soil):

Table 5, page 9 — Percent reduction in EDTA-extractable (phytoavailable) metal forms vs unamended baseline, pooled across S1–S4:

All Table 4 HQ values (non-carcinogenic risk index, derived as HQ = ADI/RfD per USEPA Risk Assessment Guidance for Superfund [42] and Supplemental Guidance for Soil Screening [43]) were well below 1. Table 6, page 10 — ILCR_T (sum of carcinogenic risk indices over Cd, Cr, Ni for dermal contact) values are on the order of 10⁻⁹ to 10⁻¹⁰, well below the 1.00 × 10⁻⁴ regulatory threshold. Selected S1 entries: unamended Cd 4.19 × 10⁻⁹ / Cr 1.60 × 10⁻⁹ / Ni 2.56 × 10⁻⁹; S1ac2 Cd 2.93 × 10⁻⁹ / Cr 1.04 × 10⁻⁹ / Ni 1.93 × 10⁻⁹. No soil-amendment combination exceeded the carcinogenic threshold for any metal or for the metal sum.

Plant uptake and phytotoxicity

SC control (low-contamination, no carbon), page 10. Medicago falcata roots: Cu 2.80, Pb 1.91, Zn 3.83, Cd <0.005, Cr 1.29, Ni 1.34 mg·kg⁻¹ d.m. Shoots: Cu 2.62, Pb 1.75, Zn 8.89, Cd 0.224, Cr 0.93, Ni 2.19 mg·kg⁻¹ d.m. SC-soil uptake orderings reported by the authors (page 10) differ between plant parts: roots = Zn > Cu > Pb > Ni > Cr > Cd; shoots = Zn > Cu > Ni > Pb > Cr > Cd (Ni precedes Pb in shoots because shoot Ni 2.19 > shoot Pb 1.75).

Contaminated soils with carbon added, page 10. Plant uptake ordering for S1–S4 amended with brown coal or activated carbon at either dose: Zn > Pb > Cu > Cr > Ni > Cd in both roots and shoots. The exception was Medicago falcata roots in the least-polluted S4 soil with carbon, where uptake ordering was Zn > Cu > Pb > Cr > Ni > Cd. Shoots took up more metal than roots for every metal tested except Pb in S4 with carbon (where roots > shoots). Page 10 and page 16.

Reduction in plant-tissue concentration attributable to activated carbon vs brown coal, ordered from largest to smallest reduction percent (Conclusions, page 16):

Activated carbon achieved a larger reduction than brown coal on every metal in both plant parts.

Forage Suitability Level (FSL) and Industrial Suitability Level (ISL) for Medicago falcata shoots, Figure 5, page 11. Critical levels were adapted from Kabata-Pendias et al. [60]. Findings: (i) only the least-polluted soil S4 with double doses of both carbons met FSL across all six metals simultaneously; (ii) ISL was met for Pb in every combination except S4 with both carbons (which fell below ISL on Pb); (iii) for Zn, FSL was met in S3 and S4 with activated carbon at either dose and in S4 with double brown coal — remaining combinations met ISL only; (iv) Cd FSL was met only in S4 with both carbon doses; (v) Ni did not exceed FSL in any combination.

Phytotoxicity, Figure 6, page 12. Without amendment, root growth inhibition was 44% in S1, 37% in S2, 30% in S3, and 21% in S4; shoot inhibition was 25% in S1, 23% in S2, 2% in S3, and zero in S4. With brown coal or activated carbon at either dose, root and shoot growth inhibition fell to zero across all soils. Germination rate was 100% in every combination, with or without amendment.

Bioconcentration factors (BCFs) for shoots, page 12 and Figure 7. SC control BCFs for Medicago falcata: Cu 0.15, Pb 0.08, Zn 0.15, Cd 0.31, Cr 0.09, Ni 0.14. All BCFs across S1–S4 and all amendment combinations were <1, classifying Medicago falcata as an exclusion plant under the Ma et al. [63] criterion (BCF <1 = excluder; 1–10 = accumulator; >10 = hyperaccumulator). Cd consistently showed the highest BCF among the six metals. Activated-carbon combinations had lower BCFs than brown-coal combinations.

Methods (brief)

Test species. Medicago falcata L. (yellow alfalfa), a stress-tolerant deep-rooted leguminous perennial selected for its high biomass, broad-range metal-uptake capacity in roots, and reported tolerance to contaminated soils (page 2). Seeds supplied by the Polish Academy of Sciences Botanical Garden, Centre for Biological Diversity Conservation in Powsin. Plants harvested at flowering stage BBCH 67.

Pot setup, page 3. Wagner-type pots (0.25 m height × 0.22 m diameter, 10 kg soil per pot) held in the vegetation hall of Warsaw University of Life Sciences. Five soil origins (SC + S1–S4) from a metallurgical-cart cleaning heap at Krzemionki Opatowskie, Poland. Twenty-one soil-amendment combinations in triplicate. Carbons mixed once at experiment setup. One vegetation cycle (March–November). NPK fertilizers applied; soil moisture maintained at 60% field capacity; temperature 20 °C; PPFD around 50–70%.

Soil characterization, page 4. Granulometric composition by Casagrande method; pH in 1 M KCl per PN-ISO 10390:2005; TOC per PN-ISO 14235:2003P; CaCO₃ per PN-ISO 10693:2002P; exchangeable alkaline cations per PN-ISO 11260:2018.

Metal analysis, page 4. Total metal mineralization in concentrated HClO₄ + HNO₃ mixture. Phytoavailable forms by single-extraction with 0.02 M EDTA. Exchangeable alkaline cations and metal contents in soils and plant tissues quantified by ICP-OES on a Thermo Scientific iCAP 6500 or a Varian Axial Vista 720-ES (Waltham, MA, USA). Blanks prepared for every measurement series; accuracy verified by the standard-additions method. Replicates in triplicate; standard deviation calculated from triplicate; coefficient of variation maintained at ≤10%.

Carbon characterization, page 4. SEM with EDS on a JSM-6380 LA scanning electron microscope and EDS electron microprobe (JEOL Ltd., Musashino, Tokyo, Japan).

Phytotoxicity test, page 4. Modified Phytotoxkit™ (MicroBioTest, Gent, Belgium) with Medicago falcata substituted for the standard test species per the precedents in Sekutowski et al. [30], Romanowska-Duda et al. [31], and Małachowska-Jutsz et al. [32]. Seeds calibrated, rinsed three times in distilled water, soaked four hours at 25 °C, transferred to test plates, watered to water-holding capacity; 72 h incubation in growth chamber at 25 °C with a night photoperiod. Three repetitions per combination. Root and shoot lengths measured with ImageTool software version 3.0.

Risk indices, pages 5–6. Pollution Index PI = Cᵢ / C_oi (Cᵢ measured, C_oi ordinance maximum). Pollution Load Index PLI = nth root of the product of PIs across n metals. Hazard Quotient HQ = ADI / RfD with ADI from ingestion (Equation 3) and dermal absorption (Equation 4) per USEPA Risk Assessment Guidance for Superfund [42] and Supplemental Guidance for Soil Screening [43]. ILCR_ij = ADI × SF_ij for carcinogenic metal i under exposure pathway j. Aggregate forms HQ_T = Σ HQ_ij and ILCR_T = Σ ILCR_ij. Parameter values (IngR, EF, ED, BW, AT, SA, AF, ABS, RfD, SF) were drawn from cited [35,41,45] literature; the source page does not republish them.

Statistics and computation, page 4. Microsoft Excel for Microsoft 365 with the Analysis ToolPak.

Limitations. Single pot-experiment trial on one geographic-origin soil set; one test plant species; one vegetation cycle. Six metals reported (Cu, Pb, Zn, Cd, Cr, Ni); no arsenic, no mercury, no aluminum, no tin. Chromium is reported as total Cr without hexavalent speciation. The plant species is forage, not human food; the soils are industrial-waste, not agricultural. Findings do not generalize to agricultural-soil food-crop systems without further evidence. A paper-internal inconsistency on SC control-soil total metal content (Table 2 vs Section 3.2 text) is documented in Verification notes.

Implications

Certification: Do not use this source in food, ingredient, or product occurrence pools. The study is an industrial-soil pot experiment and phytostabilization test, not a market sample frame. Per the Part 2 wiki/HMT&C firewall, this page reports what the paper measured and concluded; it does not propose or justify HMT&C threshold values, and the conclusions about activated carbon’s stronger immobilization effect are not extrapolated to agricultural soils or food crops.

Mitigation: contributes evidence on the magnitude of phytoavailable-metal reductions achievable in alkaline industrial-waste soils via brown coal and activated carbon amendments. Activated carbon outperformed brown coal on every metal at both doses, with the largest amendment-vs-amendment gap on Cu (61.6% vs 44.1% reduction in EDTA-extractable Cu at double dose). Relevant to Agronomic mitigation and Remediation evidence — drivers and interventions coverage, with the caveat that the trial used industrial-waste rather than agricultural soils.

App: no per-product or per-ingredient occurrence data. This source does not contribute to ingredient contamination_profile values directly; Medicago falcata is a forage species, not a food crop, and the soils studied are industrial-waste material.

Courses: useful as a case study in educator-audience modules on (i) the difference between total soil metal content and EDTA-extractable phytoavailable forms; (ii) carbon-based soil-amendment levers and their effect on bioavailable vs total metal content; (iii) phytostabilization with low-BCF excluder plants such as Medicago falcata; and (iv) USEPA-style HQ/ILCR risk assessment applied to soil contamination.

Microbiome: not applicable.

Wiki pages updated on ingest

• Lead
• Cadmium
• Chromium
• Nickel
• Copper
• Zinc
• Agronomic mitigation
• Remediation evidence — drivers and interventions
• Soil-to-plant transfer of heavy metals
• Testing

Verification notes

• Merge-enhanced from prior 2026-06-02 revision (ingest commit 61f0b46) on 2026-06-02 by the v2 manual-fetch-ingest skill autonomously, with the following changes verified against the source PDF.
• Downgraded evidence_tier: A → B. A-tier is reserved for designs with stronger external validity (multi-site, peer-replicated, market-frame sampling). This is a single pot-experiment trial on one geographic-origin soil set with one test plant and one vegetation cycle — B-tier is the correct grading.
• Replaced bespoke matrices: [industrial-soil, carbon-amendment, phytotoxicity-test, medicago-falcata, soil-to-plant-transfer] with vocabulary-compliant matrices: [soil, plant-tissue]. The prior matrix strings were not in the controlled vocabulary; phytotoxicity-test is a method label not a matrix, and medicago-falcata is the test species (already noted in sample_population). Soil-to-plant-transfer is a wiki page slug, not a matrix value, and is now correctly listed under ## Wiki pages updated on ingest. Precedent: [[sources/sharma2023-phytoremediation-heavy-metal-soil]] and [[sources/mozdzer2023-sludge-ash-granulates-crop-metals]] use [soil, plant-tissue].
• Reformatted authors: array from full-name strings to the project-standard [Last F, Last F, ...] form and restored Polish diacritics: Wiśniewska, Kamiński. Author given-name initials verified against the title page.
• Added missing provenance fields: access_url (DOI link) and raw_sha256 (computed locally on the manual-fetch PDF, value d8e67c4657e4edbc1d5cd2364610fd6b853ce0d0f86fb2fa3cca8d1ba0b78a48).
• Added sampling_locations and reformatted sample_population to make the soil-origin / pot-experiment distinction explicit.
• Plant-uptake ordering correction. Prior revision stated “the authors summarize plant uptake as Zn > Pb > Cu > Cr > Ni > Cd in both roots and shoots” without distinguishing the SC control from the carbon-amended contaminated soils. Page 10 actually reports three orderings: (i) SC control roots = Zn > Cu > Pb > Ni > Cr > Cd; (ii) SC control shoots = Zn > Cu > Ni > Pb > Cr > Cd (Ni precedes Pb in shoots because shoot Ni 2.19 > shoot Pb 1.75); (iii) amended-contaminated-soil ordering = Zn > Pb > Cu > Cr > Ni > Cd in both roots and shoots, with the S4-with-carbon roots being an exception (Zn > Cu > Pb > Cr > Ni > Cd). Updated the Key numbers section to preserve all three orderings with their attributions. (Audit subagent on 2026-06-02 flagged that my first merge-enhance pass had collapsed the SC root and SC shoot orderings together as identical; verified against page 10 of the PDF — finding was correct, applied.)
• Paper-internal typo on the S4-roots exception ordering (page 16). The source text on page 16 paragraph 1 prints the S4-with-carbon roots exception as “Zn > Cu > Pb > Cr > Ni > As > Cd” — with “As” appearing in the chain. The paper never measures arsenic (Cu, Pb, Zn, Cd, Cr, Ni are the only six metals analyzed). This is a typesetting error in the source. The wiki silently presents the corrected ordering “Zn > Cu > Pb > Cr > Ni > Cd” (dropping the spurious As). Flagged here, not silently resolved.
• SEM model-number typo on page 4 of the source. PDF page 4 prints the JEOL scanning electron microscope as “JJSM-6380 LA” with a double-J. The correct manufacturer catalog name is “JSM-6380 LA” (single J, JEOL JSM series). The wiki silently normalizes to the correct catalog name; the discrepancy is a source-side typo, not a wiki defect.
• Updated legacy heading ## Wiki pages this source may touch to the current convention ## Wiki pages updated on ingest.
• Removed [[supply-chain/wastewater-irrigation]] from the wiki-pages list. The page does not exist in wiki/supply-chain/ and the paper does not discuss wastewater irrigation at all (the study is pot-experiment phytostabilization on industrial-waste soils, not field irrigation). Added [[supply-chain/soil-to-plant-transfer]] (page exists at wiki/supply-chain/soil-to-plant-transfer.md) and [[mitigation/agronomic]] + [[mitigation/remediation-evidence]] (both exist) as the correct routing targets for this paper’s evidence.
• Added page-number citations throughout the Key numbers section per CLAUDE.md Part 14.
• Added Conclusions (page 16) ordered-reduction strings for shoots (Cr 18.2 > Zn 11.5 > Ni 10.7 > Cu 10.3 > Cd 8.9 > Pb 2.4) and roots (Cu 13.3 > Cr 12.5 > Zn 10.5 > Pb 9.0 > Ni 5.7 > Cd 4.6) verbatim from the abstract and conclusions. Values match the prior revision’s table; ordering is now preserved.
• Added Forage Suitability Level (FSL) and Industrial Suitability Level (ISL) detail from Figure 5 / page 11 (only S4 with both double carbon doses met FSL on all six metals; ISL met for Pb except S4-with-carbon; etc.).
• Added Phytotoxicity-Figure-6 (page 12) detailed inhibition percentages (44/37/30/21% for roots, 25/23/2/0% for shoots) and the 100% germination rate observation.
• Added Pollution Load Index (PLI) bands and S1 residential vs industrial benchmark values from Figure 3 / page 8.
• Added BCF detail from page 12 / Figure 7 (SC control BCFs for shoots, excluder classification per Ma et al. ref [63]).
• Methods section enriched with: instrument vendor/model identifiers per brand-firewall Exception 2 (Thermo Scientific iCAP 6500, Varian Axial Vista 720-ES, JEOL JSM-6380 LA SEM, MicroBioTest Phytotoxkit™, ImageTool 3.0); pot dimensions; vegetation period; soil moisture; fertilizer; ISO method numbers for soil characterization; the standard-additions accuracy verification.
• Brand-firewall compliance verified: no food-brand or consumer-product brand names appear in the source; all named vendor/instrument identifiers are scientific-method materials retained per brand-firewall Exception 2.
• metals: uses total-Cr (Cr) because the paper performed total-Cr mineralization (HClO₄ + HNO₃) without hexavalent speciation per CLAUDE.md Part 14 speciation rule. iAs/tAs and MeHg/tHg are not in scope — no arsenic or mercury measurements were taken.
• ingredients: and products: deliberately empty: Medicago falcata is a forage legume, not the food-legume scope covered by [[ingredients/legumes]]. The paper assesses FSL/ISL for plant tissue (a feed-suitability framing) but does not characterize a food ingredient or consumer product in the HMI sense.
• jurisdictions: [PL] reflects Poland as the soil origin, pot-experiment location, and source of the cited Regulation of the Minister of the Environment of 1 September 2016 (J. Laws Item 1395 2016, ref [47]) used as the ordinance benchmark. No HMI regulation slug exists for this Polish ordinance; not added to ## Wiki pages updated on ingest.
• Paper-internal inconsistency preserved from prior revision and re-verified. Table 2 (page 6) reports SC control-soil totals as Cu 13.1 / Pb 14.8 / Zn 49.1 / Cd 0.34 / Cr 7.51 / Ni 12.4 mg·kg⁻¹ d.m. (mean ± SD across triplicate). Section 3.2 text (page 6) reports SC as Cu 17.2 / Pb 23.1 / Zn 61.1 / Cd 0.72 / Cr 10.4 / Ni 15.9 mg·kg⁻¹ d.m. These do not match and the paper does not reconcile them. Table 2 values are used throughout the wiki page because the table is the primary data display and the column units match the ± SD format; the Section 3.2 numbers may be a typesetting carry-over from an earlier draft. Flagged here, not silently resolved.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.