Table 1.
Summary of research on Hg phytoremediation potential and toxicity of Hg promising (hyper)accumulator species, wide-range heavy metal accumulator, and crop plants. * (Growth parameters recorded in regard to the control treatments).
| Type | Plant sp. | Growth Conditions | Phytotoxic Concentration | Growth Parameters (Phytotox. Conc.) * | Hg Accumulation (BAF, BCF and TF) |
References |
|---|---|---|---|---|---|---|
| potential Hg (hyper)accumulator native species | Vigna unguiculata L. Walp | Soil pots—3 m old ecotypes: 1. native genotype 2. commercial line L-019 3. commercial line L-042 |
5 and 8 mg kg−1 Hg(NO3)2 (added to 0.2 mg Hg kg−1 contaminated soil) | Negligible biomass decrease with ^ Hg | root > leaf > stem; BCF < 1 (all genotypes); BAFstem/soil < 0.5, BAFseed/soil < 0.5; 1. TF < 1 for native genotype 2. TF~1.5 (for 0.2 mg Hg kg−1 dw) for both commercial lines |
[102] |
| Phragmites australis | Plant samples were taken from gold mine contaminated wetland (wet and dry season) | - | - | root[Hg]—806 µg kg−1 dw stem[Hg]—495 µg kg−1 dw leaves[Hg]—833 µg kg−1 dw BAF—0.73/0.22 TF—0.57/1.99 |
[55] | |
| Cyperus eragrostis | BAF—0.22/0.35 TF—1.99/3/60 |
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| Datura stramonium | BAF—0.20/0.61 TF—4.26/8.30 |
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| Panicum coloratum | BAF—0.11/0.13 TF—3.70/10.94 |
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| Persicaria lapathifolia | BAF—0.11/0.20 TF—3.10/3.07 |
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| Melilotus alba | BAF—0.13/0.21 TF—0.54/0.60 |
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| Lathyrus pratensis | Aerial parts of plants growing in the area of an abandoned gold mine in the Czech Republic were collected (0.207–15.0 mg total Hg kg−1 soil) | - | - | Shoot[Hg]—0.108 mg kg−1 dw | [54] | |
| Epipactis sp. | Shoot[Hg]—0.152 mg kg−1 dw | |||||
| Axonopus compressus | Plant samples were taken from soil contaminated by artisanal small-scale gold mines (arbuscular mycorrhizal fungi (AMF) colonization was aslo determined | - | - | root[Hg]—0.15 mg kg−1 dw shoot[Hg]—0.33 mg kg−1 dw BAFroot/leaves—0.03/0.06 TF—2.16 |
[103] | |
| Erato polymnioides | root[Hg]—3.56 mg kg−1 dw shoot[Hg]—1.48 mg kg−1 dw BAFroot—0.80; TF—0.42 |
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| Miconia zamorensis | root[Hg]—2.06 mg kg−1 dw shoot[Hg]—0.98 mg kg−1 dw BAFroot—0.47; TF—0.47 |
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| Cyrtomium macrophyllum | 60 d old seedlings from uncontaminated sites (grown 1st hydroponically) 1. 225.73 mg total Hg kg−1 soil or 2. 0, 5, 10, 20, 50, 100, 200, 500 and 1000 mg HgCl2 kg−1 soil |
500 and 1000 mg kg−1 HgCl2 | 20.2% biomass reduction | 1. shoot[Hg]—36.44 mg kg−1 dw root[Hg]—13.90 mg kg−1 dw BCF—0.061; TF—2.62 2. for treatments up to 200 mg kg−1: BCF > 1; TF > 1 |
[53] | |
| Manihot esculenta Crantz | 1. soil pots with mixtures of mine tailings and biosolids; 4 w old cuttings ( 11.67 mg total Hg kg−1 mine tailings); 2. hydroponic solution with 50 or 100 µM HgCl2; 5 w old plants |
mixtures with 50, 75, or 100% mine tailings | significant root biomass decrease | 1. Hg not determined in plants 2. root[Hg]—6.836 and 12.13 g kg−1 dw (50 and 100 µM Hg) |
[104] | |
| Dillenia suffruticosa | Plants were cultivated on 2 ex-gold mine tailings areas: (i) tailings site where last mining activity was 2 years prior (0.5 mg Hg kg−1) (ii) tailings site where last mining activity was 10 years prior (0.02 mg Hg kg−1) |
none observed | no significant decrease in plant growth (height and diameter) | BCF—15.5; TF—3.0 | [50] | |
| Vitex pinnata | BCF—40; TF—0.6 | |||||
| Archidendron pauciflorum | BCF—11.0; TF—0.1 | |||||
| Anacardium occidentale | BCF—6.5; TF—0.3 | |||||
| Shorea leprosula | BCF—7.5; TF—0.5 | |||||
| Alstonia scholaris | BCF—45.0; TF—1.3 | |||||
| Hevea brasiliensis | BCF—13.5; TF—0.1 | |||||
| Alyssum saxatile L. | Plant samples were collected from 41 sites in an active mining district in Western Turkey (mean 6.609 µg Hg kg−1 soil) | - | - | root[Hg]/soil[Hg]—0.10 shoot[Hg]/soil[Hg]—0.04 Mean TF—0.85 |
[52] | |
| Anchusa arvensis L. | root[Hg]/soil[Hg]—0.06 shoot[Hg]/soil[Hg]—0.06 Mean TF—1.03 |
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| Centaurea cyanus L. | root[Hg]/soil[Hg] < 0.5 shoot[Hg]/soil[Hg] < 0.5 Mean TF > 1 |
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| Cynoglossum officinale | root[Hg]/soil[Hg] < 1 shoot[Hg]/soil[Hg] < 1 Mean TF < 1 |
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| Glaucium flavum | root[Hg]/soil[Hg]—0.09 shoot[Hg]/soil[Hg]—0.02 Mean TF—0.25 |
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| Isatis sp. L. | root[Hg]/soil[Hg]—0.02 shoot[Hg]/soil[Hg]—0.02 Mean TF—0.63 |
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| Onosma sp. | root[Hg]/soil[Hg] < 0.5 shoot[Hg]/soil[Hg] < 0.5 Mean TF > 1 |
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| Phlomis sp. | root[Hg]/soil[Hg]—0.21 shoot[Hg]/soil[Hg]—0.56 Mean TF—2.05 |
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| Silene compacta | root[Hg]/soil[Hg] < 0.5 shoot[Hg]/soil[Hg] < 0.5 Mean TF—1.66 |
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| Tripleurospermum maritimum | root[Hg]/soil[Hg]—0.02 shoot[Hg]/soil[Hg]—0.01 Mean TF—0.59 |
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| Verbascum thapsus L. | root[Hg]/soil[Hg]—0.03 shoot[Hg]/soil[Hg]—0.06 Mean TF—2.47 |
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| Sesbania grandiflora | 17 d old seedlings in hydroponic solution | 50 and 60 mg L−1 HgCl2 | 56% growth decrease 19% biomass reduction (60 mg Hg L−1) |
mostly in roots; TF—low. |
[91] | |
| Jatropha curcas | Pots with Hg-contaminated soil (1.76 mg kg−1) spiked with 1, 5 or 10 mg Hg(NO3)2 kg−1; 1, 2, 3 or 4 m old seedlings (seeds of plants from uncontaminated soil) | none observed | - | plant[Hg]—max. 7.25 mg kg−1 dw (for 10 mg Hg kg−1 soil) BCF—good, with increased exposure (4th month); TF~1 (after 2 months, then decreased) |
[105] | |
| Lepidium sativum L. | Soil pots (spiked with 10 or 100 mg HgCl2 kg-1 dw) with/without different fractions of uncontaminated compost; 10 d seedlings | (a) 10 and 100 mg kg−1 HgCl2; (b) none observed for compost amended soil |
(a) 27% decrease in shoot length; 53% decrease in root (10 mg Hg kg−1) |
mostly in roots; add. compost—^ accumulation; BCF—high for 10 mg Hg kg−1 dw in 2/1 compost |
[106] | |
| Flueggea tinctoria (L.) G.L. Webster | Aerial plant parts were collected from a riparian area in the mining district of Almadén (122—385 mg total Hg kg−1 soil) | - | - | BCF—5.9 | [49] | |
| Tamarix canariensis Willd. | BCF—10.72 | |||||
| Nerium oleander L. | BCF—6.2 | |||||
| Typha domingensis Pers. | BCF—4.3 | |||||
| Phragmites australis Cav. | BCF—32.2 | |||||
| Atriplex conodocarpa | 25 seeds/species were sown in pots with Hg spiked potting mix (17.3 mg Hg kg−1 soil) | no phytotoxic symptoms were observed | Biomass, leaf area and number remained unchanged (in regards to unspiked soil) | shoot[Hg]—1.09 mg kg−1 dw translocation %—19% |
[107] | |
| Australodanthonia caespitose | shoot[Hg]—1.20 mg kg−1 dw translocation—15.9% |
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| Chilopsis linearis | 2 w old seedlings in Hoagland solution | 50, 100, 200 µM (CH3COO)2Hg | 49% decrease in root length | root[Hg]—^ with Hg conc. TF—low |
[108] | |
| Medicago sativa | 4 d old seedlings in 1/4 Hoagland solution | 20 µM HgCl2 | 54% decrease in root biomass | - | [88] | |
| Eichornia crassipes | 30 d old plants in spring water tanks (0, 0.5, 2 mg L−1 HgSO4) | - | - | root[Hg]—26.2 mg kg−1 dw (for 2 mg Hg L−1) |
[101] | |
| Pistia stratiotes | root[Hg]—83.2 mg kg−1 dw | |||||
| Scirpus tabernaemontani | root[Hg]—3.88 mg kg−1 dw | |||||
| Colocasia esculenta | root[Hg]—6.99 mg kg−1 dw | |||||
| Sesbania drummondii | 15 d old seedlings in 1/2 Hoagland solution | 50 and 100 mg L−1 HgCl2 | 36.8% biomass reduction (100 mg Hg L−1) | root[Hg] > shoot[Hg] | [89] | |
| Rumex induratus | Field experiment; Whole plants were collected from sites with: 122.4 mg total Hg kg−1 dw (0.006% available Hg) |
- | root[Hg]—8.3 mg kg−1 dw shoot[Hg]—7.3 mg kg−1 dw TF—0.96 Phytoextraction efficiency 12.9 g Hg ha−1 year−1 |
[109] | ||
| Marrubium vulgare | 550.1 mg total Hg kg−1 dw (0.032% available) | root[Hg]—67.2 mg kg−1 dw shoot[Hg]—23.0 mg kg−1 dw TF—0.34 Phytoextraction efficiency 27.6 g Hg ha−1 year−1 |
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| Medicago sativa | 12 d old seedlings in a beaker-size hydroponic system | 30 µM HgCl2 | abrupt 30–40% growth inhibition (first 24 h) | - | [87] | |
|
Myriophylhum aquaticum
Ludwigina palustris Mentha aquatica |
21 d old plants in water solution with hydroponic fertilizer | - | - | average removal efficiency—99.8% (all 3 plants); removal rate—0.0787–0.0002 mg Hg L−1 d−1 |
[100] | |
| Nicotiana miersii | 5 w old plants in 1/4 Hoagland | 1. 1.0 mg Hg0 m3 2. 1.0 µg HgCl2 mL−1 |
1. Visible signs of stress 2. Inhibition of root and shoot |
1. only in shoots 2. mostly in roots |
[110] | |
| broad-spectrum heavy metal (hyper)accumulator species | Brassica juncea Long-standing and Florida Broad Leaf cultivars | 2 and 4 w old plants grown hydroponically | 1.96, 4.11, 12.2, and 16.7 mg L−1 Hg(NO3)2 | 25% biomass decrease | BCFroot—750–1100; BCFshoots—82–104; roots[Hg]/shoot[Hg]—8–100 |
[111] |
| Brassica juncea | 36 d old seedlings grown hydroponically | 5 and 10 mg L−1 HgCl2 | 5.1-fold reduced transpiration rates | BCFroot—100–270; BCFshoot—0.31–1.07; shoots[Hg]/root[Hg]–0.3–0.76 |
[112] | |
| crop plant species | Hordeum vulgare | Soil pots—3 soil compositions: 1. 8.35 mg HgCl2 kg−1 dw; 2. 32.16 mg total Hg kg−1 dw; 3. 32.16 mg total Hg kg−1 dw + 1 mg HgCl2 kg−1; 150 d old plants |
- | - | 1. shoot[Hg]—1.51–5.13 mg kg−1 dw; (L. esculenta and L. albus the highest); 2. shoot[Hg]—0.16–1.13 mg kg−1 dw; 3. shoot[Hg]—6× L. albus, 5× C. aretinum, 3.5× H. vulgare and L. esculenta (* regards to 2nd treatment) |
[113] |
| Lupinus albus | ||||||
| Lens esculenta | ||||||
| Cicer aretinum | ||||||
| Cucumis sativus | 10 and 15 d old seedlings in 10% MS media | 250–500 µM HgCl2 | 96% root length reduction (10 d old seedlings) 98% root length reduction (15 d old seedlings) |
root[Hg]—7-fold and 5.6-fold > cotyledons (after 10 and 15 d) | [114] | |
| Oryza sativa | 3 w old seedlings in Long Ashton modified nutrient solution | 0.5 mg L−1 HgCl2 | 50% shoot biomass reduction | root[Hg] 2× > shoot[Hg] BCF~1900 (for higher Hg conc.) |
[115] | |
| Lycopersicon esculentum | 30 d old seedlings in modified Hoagland | 50 µM HgCl2 | suppressed biomass production (roots and shoots) | root[Hg]—27-fold > shoot; uptake ^ linearly with concentration | [90] | |
| Pisum sativum | seedlings in solution culture | 5 and 10 mg L−1 HgCl2 or 203HgCl2 | growth inhibition: 50% shoot and root length decrease (10 mg Hg L−1) |
mostly in roots; linearly increase with [Hg]; TF—low |
[116] | |
| Mentha spicata | cuttings in solution culture |
BCF = Bioconcentration Factor (plant[Hg]/corresponding soil or media[Hg]; depending on study, plant[Hg] can refer to root[Hg]); BAF = Bioaccumulation Factor (shoot[Hg]/corresponding soil or media[Hg]); TF = Translocation Factor (shoot[Hg]/root[Hg]); ^ = increase; d = days; w = weeks; m=months; [Hg] = Hg concentration.