Yildirim et al. 2021 — Humic + Fulvic acid mitigation of soil Cd uptake by garden cress (Erzurum, Turkey)
This greenhouse pot study tested whether soil application of a commercial humic + fulvic acid product (Powhumus, 80–85% humic substances composed of 90% humic acid + 10% fulvic acid) reduced the uptake of cadmium into the edible aerial tissue of garden cress (Lepidium sativum cv Helen) grown in artificially Cd-spiked soil. Authors used a 3×4 factorial of soil Cd (0, 100, 200 mg/kg as CdSO4·8H2O) crossed with HA+FA solution (0, 3500, 5250, 7000 mg/L). The principal finding for the wiki is that, at the highest HA+FA rate (7000 mg/L), Cd uptake into garden cress leaves was reduced by 95% relative to the no-amendment control at 200 mg/kg soil Cd, and Cl uptake by 80%. HA+FA also mitigated Cd-driven losses of leaf and root biomass, leaf area, chlorophyll content, leaf relative water content, and antioxidant enzyme stress markers. The study is an agronomic / soil-amendment intervention, not a food-occurrence survey: it does not measure Cd in retail or harvested commercial cress and the soil Cd doses are far above typical agricultural-soil contamination.
Key numbers
Analytical method. Plant macro- and micro-element content (N, P, K, Ca, Mg, Fe, Cu, Mn, Zn, B, Cd, Cl) determined on dried, ground leaf tissue by Kjeldahl distillation (for total N, Vapodest 10 Rapid Kjeldahl unit, Gerhardt) and inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 2100 DV, PerkinElmer) following procedures of AOAC Official Methods 922.02 and 975.03. Cd is reported as total elemental Cd on a leaf dry-weight basis. Soil characterization: pH 5.61, CEC 15.5 cmol(+)/kg, EC 1.15 dS/m, total N 1.15%, P 15.5 mg/kg, Zn 2.30 mg/kg, Cu 1.1 mg/kg, Fe 0.5 mg/kg, Mn 1.8 mg/kg, Cd 0.05 mg/kg (baseline soil Cd), K 2.2 cmol(+)/kg, Ca 11.0 cmol(+)/kg, Mg 2.25 cmol(+)/kg; soil texture 33% sand, 34% silt, 33% clay, 1.2% organic matter; classified as Ustorthents per Soil Survey Staff 1999. Cadmium was applied to soil as CdSO4·8H2O and incubated for 3 weeks before sowing. HA+FA applied as Powhumus solution at three rates plus a no-amendment control, three times per week starting before planting, at a rate of 150:100:150 kg/ha N:P:K basal fertilizer in the 0 HA+FA control.
Leaf cadmium (mg/kg leaf dry weight; Table 5; mean ± SD of quadruplicate measurements; Duncan multiple-comparison letters from the paper omitted here):
- 0 mg/kg soil Cd, 0 HA+FA: 0.20 ± 0.02
- 0 mg/kg soil Cd, 3500 HA+FA: 0.25 ± 0.01
- 0 mg/kg soil Cd, 5250 HA+FA: 0.32 ± 0.02
- 0 mg/kg soil Cd, 7000 HA+FA: 0.34 ± 0.03
- 100 mg/kg soil Cd, 0 HA+FA: 43.01 ± 0.20
- 100 mg/kg soil Cd, 3500 HA+FA: 25.99 ± 0.19
- 100 mg/kg soil Cd, 5250 HA+FA: 7.92 ± 1.34
- 100 mg/kg soil Cd, 7000 HA+FA: 1.12 ± 0.81
- 200 mg/kg soil Cd, 0 HA+FA: 96.61 ± 0.26
- 200 mg/kg soil Cd, 3500 HA+FA: 47.05 ± 0.98
- 200 mg/kg soil Cd, 5250 HA+FA: 13.98 ± 1.44
- 200 mg/kg soil Cd, 7000 HA+FA: 3.00 ± 1.13
HA+FA effect on leaf Cd at 200 mg/kg soil Cd: 96.61 → 3.00 mg/kg dry weight, a 96.9% reduction (the paper’s abstract and discussion describe the 7000 mg/L HA+FA effect as a “95% reduction in Cd uptake”; the computed reduction from Table 5 is 96.9% at the 200 mg/kg soil-Cd level and 97.4% at the 100 mg/kg soil-Cd level). Cl uptake at 7000 mg/L HA+FA falls from 1.02 mg/kg to 0.20 mg/kg at 200 mg/kg soil Cd, an 80% reduction (Table 5).
Leaf biomass (Table 1; g/plant fresh weight; n = 4): Without Cd, leaf fresh weight rises from 3.66 g (0 HA+FA) to 4.97 g (7000 HA+FA). At 200 mg/kg soil Cd, leaf fresh weight is 0.43 g without HA+FA and 1.56 g at 7000 HA+FA (262% increase). Leaf dry weight at 200 mg/kg Cd: 0.08 g (0 HA+FA) → 0.19 g (7000 HA+FA), a 137% increase.
Root biomass (Table 1; g/plant fresh weight; n = 4): At 200 mg/kg soil Cd, root fresh weight is 0.14 g (0 HA+FA) → 0.91 g (7000 HA+FA, +550%). Root dry weight: 0.03 g → 0.07 g (+133%).
Stem diameter, leaf area, chlorophyll, membrane permeability, LRWC (Table 2): At 200 mg/kg soil Cd, 7000 HA+FA reverses Cd-driven losses by +92% stem diameter, +104% leaf area, +34% chlorophyll (CRV/SPAD), −9% membrane permeability (lower is better), +32% leaf relative water content.
Oxidative-stress and antioxidant enzymes (Table 3): At 200 mg/kg soil Cd, 7000 HA+FA reduces H2O2 by 66% (662.68 → 218.94 mmol/kg), MDA by 68% (13.67 → 4.37 nmol/g), proline by 70% (200.37 → 59.33 µg/g), and sucrose by 56% (62.95 → 27.60 %). At the same Cd dose, 7000 HA+FA decreases CAT by 43% and SOD by 21%, and increases POD by 186% (0.78 → 2.23 EU gr/leaf).
Other macronutrients and micronutrients at 200 mg/kg soil Cd, 7000 HA+FA vs 0 HA+FA control (Tables 4–5). The paper’s abstract reports N +75%, P +23%, K +84%, Ca +87%, Mg +40%, Fe +85%, Mn +143%, Cu +1%, Zn +65%, B +115%. Cell-level recomputation from Tables 4–5 confirms eight of ten figures (N 1.17→2.05 = +75%, P 1064→1313 = +23%, K 3912→7209 = +84%, Ca 2709→5068 = +87%, Mg 1920→2690 = +40%, Fe 50.87→94.22 = +85%, Zn 6.48→10.72 = +65%, B 4.12→8.87 = +115%), but the Mn and Cu figures appear to have been transposed in the abstract. Cell-level data shows Mn 16.90 → 16.93 = +0.2% (abstract reports +143%) and Cu 3.24 → 7.90 = +144% (abstract reports +1%). The wiki page reports the corrected cell-level values; the abstract figures are noted for traceability but should not be cited as authoritative. These mineral-nutrient improvements are reported as evidence that HA+FA stabilization of soil Cd preserves uptake capacity for essential elements; they are not contamination concentrations and the paper does not cite consumer-protection comparators for them.
Methods (brief)
Garden cress (Lepidium sativum cv Helen) was sown into 1-L pots filled with a 1:1 (v:v) mixture of three-week-incubated garden soil:sand at 1–1.5 cm depth, ten seeds per pot, thinned to four plants per pot after emergence. Greenhouse maintained at 22 ± 2 °C day / 17 ± 2 °C night at Atatürk University, Erzurum, Turkey. Soil was collected from a depth of 15 cm in Erzurum-province agricultural fields (39°55′N, 41°61′E), air-dried and sieved through 4 mm and 2 mm meshes, characterized for physicochemistry, then spiked with CdSO4·8H2O to nominal 0, 100, or 200 mg Cd/kg dry soil and incubated for 3 weeks before sowing.
Powhumus (Humintech GmbH, Grevenbroich, Germany) — 80–85% humic substances (90% humic acid + 10% fulvic acid), 10–12% K2O, 1.0% total organic N, <100 µm particle size, pH 9–10, ash content 22.9% (mass); element content of the Powhumus product itself (% mass) C 2, H 2.8, N 1.3; element content on ash-free basis (% wt) C 47.1, H 3.63, N 1.69, O 47.58 — was dissolved in water to 350,000 mg/L and diluted to working solutions of 3500, 5250, and 7000 mg/L. Solutions applied to soil three times per week starting before planting. The no-HA+FA control received basal 150:100:150 kg/ha N:P:K fertilizer only.
Harvest at day 50. Plant tissue dried at 70 °C for 48 h. Quadruplicate analyses per treatment. Statistics: randomized plot design, ANOVA, Duncan multiple-comparison test (P < 0.05), SPSS 20.
Speciation and methods caveats
- Cadmium is reported as total elemental Cd by ICP-OES. No speciation is performed or required for Cd in this context (Cd does not have routinely reported environmental species the way iAs/tAs or Cr(III)/Cr(VI) do).
- Soil Cd dose levels (100, 200 mg/kg) are 2,000× and 4,000× the baseline soil Cd characterization (0.05 mg/kg) for the same field, and are far above typical agricultural-soil Cd concentrations. The study is a Cd-stress / phytoremediation experiment, not a representation of realistic field soil contamination.
- Leaf Cd values (0.20 mg/kg dry weight in the no-Cd, no-HA+FA control) and absolute Cd concentrations under stress (43.01 to 96.61 mg/kg dry weight) are dry-weight values, not as-consumed values. Garden cress moisture content is high (typical >85% water on fresh-weight basis), so as-consumed concentrations would be approximately one-tenth of the reported dry-weight values; the paper does not convert.
- Limits of detection, recovery percentages, blank values, and certified reference material results are not reported in the methods narrative.
- Only one cultivar of Lepidium sativum (cv Helen) is tested, in one soil type (Ustorthents, Erzurum province), under one greenhouse climate. The generalizability of the 95% Cd-uptake reduction figure to other cultivars, soil types, climates, and field conditions is not established by this study.
- The paper does not report whether Cd entering the leaf tissue is partitioned into bound or bioavailable forms; the 95% reduction refers to total leaf Cd mass.
- The HA+FA product is a specific commercial preparation (Powhumus, Humintech GmbH); funding acknowledgment names Humintech GmbH alongside Atatürk University Scientific Research Projects Foundation (project FBA-2019-7219). The authors declare no competing interests, but readers should note the industry funding when interpreting the magnitude of the effect.
- Paper-internal abstract/text inconsistencies (flagged but not propagated). The paper’s abstract and Results-text on p.4 state HA+FA at 7000 mg/L “increased the MP and LRWC values by 537% and 32%, respectively, compared to the control” at 200 mg/kg Cd. The +537% MP figure only reconciles against the absolute 0 Cd / 0 HA+FA control (MP 5.93 → 37.88 ≈ +539%) — i.e., a comparison across both Cd dose AND HA+FA. The other “increased by N%” figures for biomass and leaf-area parameters reconcile against the same-Cd-dose 200/0 baseline (e.g., leaf fresh weight 0.43 → 1.56 ≈ +263% ≈ the abstract’s +262%). At the more meaningful same-Cd-dose baseline, MP actually decreases (41.94 → 37.88, ≈ −9.7%), so the abstract framing of “+537% MP” misrepresents HA+FA’s effect on membrane permeability. The wiki page reports the same-Cd-dose MP direction throughout. Separately, the abstract’s mineral-nutrient percentages list “Mn” twice and appears to have transposed Mn and Cu (see Key numbers above): the actual cell-level changes are Mn +0.2% and Cu +144%, not Mn +143% and Cu +1%.
Implications
Standards work. This source contributes B-tier evidence on the agronomic/soil-amendment lever for reducing Cd uptake into the edible aerial tissue of a leafy vegetable (garden cress). It is supply-chain mitigation evidence, not finished-product occurrence data, and does not on its own support threshold-setting work for any HMTc product row. It can inform educator-facing and grower-facing material about how soil amendments influence plant Cd uptake, and it adds one data point to the broader literature on humic-substance phytoremediation of Cd-contaminated soils.
Courses. Useful for teaching the relationship between soil Cd contamination, soil chemistry (CEC, organic-matter complexation), and plant Cd uptake; for illustrating how a soil amendment can reduce metal bioavailability without removing the metal from the soil profile; and for the antioxidant-enzyme stress-response framework (H2O2, MDA, CAT, POD, SOD, proline, sucrose) as biomarkers of plant heavy-metal stress.
App. Limited direct app utility. The source documents that leafy-vegetable Cd uptake from heavily Cd-spiked soil can be reduced by an order of magnitude with humic-substance amendment, which is a supply-chain context fact rather than a per-product occurrence value. The dry-weight leaf Cd values (0.20 mg/kg in the no-Cd control) are within the range of normal background leafy-vegetable Cd and should not be used as occurrence percentiles for the leafy-greens commodity.
Wiki pages this source may touch
Verification notes
- Discovery context: this PDF was auto-fetched by the
discoverskill against the seasonal-geographic-variance gap on a keyword match for “mineral water + Cd + product.” The match is a false positive on every term: the paper is a Cd-soil-amendment pot study on garden cress (a leafy vegetable), with no mineral water, no drinking-water analysis, no commercial product, and no seasonal/geographic variance design. The paper is nevertheless on-topic for HMI as an agronomic Cd-mitigation reference for the leafy-greens supply chain. The auto-fetcher’s filename keyword string is retained in raw_handle for daemon traceability but is not descriptive of the paper’s content. - Brand-firewall check: no consumer brands named. The HA+FA product (Powhumus, Humintech GmbH) is a soil-amendment input, not a food brand; named per Part 12 scientific-method/input exception. Scientific equipment named (PerkinElmer Optima 2100 DV ICP-OES, Vapodest 10 Rapid Kjeldahl Distillation Unit, Konica Minolta SPAD-502 chlorophyll meter, CID Bio-Science CID-202 leaf area meter, Olympus light microscope, SPSS 20) retained per Part 12 scientific-method exception.
- Wiki/HMTc-firewall check: no HMT&C-threshold comparisons or harmonization. No consumer-protection or regulatory comparators are cited by the source for Cd, so none are reproduced; the discussion is framed in agronomic/phytoremediation terms (plant growth, antioxidant enzymes, uptake/translocation) not food-safety thresholds.
- Taxonomy: routed to the existing
ingredients/leafy-greensumbrella because garden cress is a leafy vegetable entering the salad/garnish/microgreen supply chain. No species-level ingredient slug exists for garden cress, and the 5-paper threshold for a stand-alonegarden-cressingredient page is not met by this single source. - Matrices set to
leafy-vegetableandagricultural-soil; no product-shaped slug is appropriate because the study is a controlled pot experiment with artificial Cd spiking, not a finished consumer product.products: []is correct. - Metals set to
[Cd]only. The paper measures plant tissue N, P, K, Ca, Mg, Fe, Cu, Mn, Zn, B, and Cl, but these are plant mineral-nutrient measurements (essential elements for plant nutrition), not heavy-metal contamination measurements. Including Cu, Mn, Zn in the metals field would mischaracterize the paper as a Cu/Mn/Zn contamination study. - Evidence tier: B. Greenhouse pot study with a single cultivar in a single soil type with a commercial soil-amendment product whose manufacturer is named as a funding acknowledger. Solid experimental design with quadruplicate measurements, but the funding tie and the single-system scope keep this below A-tier.
- Cd reduction figure: the abstract reports a 95% reduction in Cd uptake at 7000 mg/L HA+FA at 200 mg/kg soil Cd; Table 5 computation gives 96.9% at 200 mg/kg Cd and 97.4% at 100 mg/kg Cd. The wiki page reports both the abstract figure (as the paper states it) and the Table-5-derived figure, with the abstract framing flagged as a rounded approximation.
- Audit subagent (2026-05-30, fresh-context general-purpose agent) returned REVISE with three ⚠️ concerns; verified all three against the PDF and applied:
- (a) Audit flagged that the abstract’s “+537% MP” claim contradicts Table 2’s at-same-Cd-dose decrease (41.94 → 37.88). Verified against PDF p.4 Results text and Table 2 — the +537% only reconciles vs the 0/0 absolute control. Applied: added paper-internal-inconsistency caveat in Speciation and methods caveats.
- (b) Audit flagged that the abstract’s Mn +143% / Cu +1% figures do not reconcile with Tables 4–5. Verified against PDF p.5 Table 5 (Mn cell 200/7000 = 16.93 vs 200/0 = 16.90 ≈ +0.2%; Cu cell 200/7000 = 7.90 vs 200/0 = 3.24 ≈ +144%) — confirmed Mn and Cu values are transposed in the abstract. Applied: corrected Key numbers paragraph to flag the transposition with cell-level values; preserved the abstract figures for traceability.
- (c) Audit flagged Powhumus composition conflated “ash content (mass)” with “element content on ash-free basis” and truncated the “10–12% K2O” range to “12% K2O”. Verified against PDF p.2 — confirmed. Applied: rewrote the Powhumus composition line to separate ash content (22.9%), Powhumus product element content (C 2, H 2.8, N 1.3 % mass), and ash-free element content (C 47.1, H 3.63, N 1.69, O 47.58 % wt), and restored the 10–12% K2O range.
- Audit’s three other checks (slug-validity, brand-firewall, HMTc-firewall) all returned ✅ with no findings. Numeric fidelity check otherwise ✅ across all 12 cells of Table 5, Tables 1–3 biomass/stress markers, soil characterization, and Cd reduction recomputations.
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.