Helianthus annuus

How it works

Mechanisms: rhizofiltrationphytoextraction

Contaminants

Contaminant	Evidence	What was shown
Uranium	field	Rhizofiltration of uranium from water using terrestrial plants, sunflower and Indian mustard, including a pilot test on water from a former uranium processing plant at Ashtabula, Ohio (Dushenkov et al. 1997). The method had been developed two years earlier for lead and other metals (Dushenkov et al. 1995). Dushenkov et al., Removal of uranium from water using terrestrial plants, Environ. Sci. Technol. 31:3468, 1997 Dushenkov et al., Rhizofiltration: the use of plants to remove heavy metals from aqueous streams, Environ. Sci. Technol. 29:1239, 1995
Zinc	field	Field trial from 2005 at Torviscosa (Udine), on an industrial site polluted by pyrite cinders and placed on the national priority list in 2001 (soil: As 309, Cd 4.29, Co 50.9, Cu 1,527, Zn 980 mg/kg): zinc removal of about 1,000 g/ha with sunflower and 2,000 g/ha with sorghum; fertiliser and amendment raised biomass but not metal concentration in tissues (Marchiol et al. 2007). Marchiol et al., Removal of trace metals by Sorghum bicolor and Helianthus annuus in a site polluted by industrial wastes: a field experience, Plant Physiol. Biochem. 45:379, 2007

Contaminant

Evidence

What was shown

field

Rhizofiltration of uranium from water using terrestrial plants, sunflower and Indian mustard, including a pilot test on water from a former uranium processing plant at Ashtabula, Ohio (Dushenkov et al. 1997). The method had been developed two years earlier for lead and other metals (Dushenkov et al. 1995).

Dushenkov et al., Removal of uranium from water using terrestrial plants, Environ. Sci. Technol. 31:3468, 1997
Dushenkov et al., Rhizofiltration: the use of plants to remove heavy metals from aqueous streams, Environ. Sci. Technol. 29:1239, 1995

Zinc

field

Field trial from 2005 at Torviscosa (Udine), on an industrial site polluted by pyrite cinders and placed on the national priority list in 2001 (soil: As 309, Cd 4.29, Co 50.9, Cu 1,527, Zn 980 mg/kg): zinc removal of about 1,000 g/ha with sunflower and 2,000 g/ha with sorghum; fertiliser and amendment raised biomass but not metal concentration in tissues (Marchiol et al. 2007).

Marchiol et al., Removal of trace metals by Sorghum bicolor and Helianthus annuus in a site polluted by industrial wastes: a field experience, Plant Physiol. Biochem. 45:379, 2007

Limits

From soil, removal is on the order of a kilogram of zinc per hectare per year: against hundreds of mg/kg in soil, clean-up times are very long. Rhizofiltration treats water, not soil, and leaves contaminated roots to dispose of. The use of sunflowers in ponds near Chernobyl is often cited, but no verifiable primary source for its results was found, so it is not quantified here.

Where it has been tried

Ashtabula, former uranium processing facility

PhytoremediationField pilot

Dushenkov and colleagues selected in the laboratory sunflowers whose roots concentrate uranium (bioaccumulation coefficients up to 30,000) and then tested a pilot rhizofiltration system on site, in which contaminated water flows through the roots.

Outcome The pilot system brought uranium below 20 µg/L before discharge. Nearly all the uranium stayed in the roots. It is a trial on water, not on soil.

Uranium

Dushenkov et al., Removal of uranium from water using terrestrial plants, Environmental Science & Technology, 1997

Caffaro di Torviscosa (formerly Grado and Marano Lagoon)

PhytoremediationField scale

Helianthus annuus, Medicago sativa, Raphanus sativus var. oleiformis, Lolium multiflorum

Sunflower, alfalfa, fodder radish and Italian ryegrass grown in the field on pyrite cinders capped with 0.15 m of clean soil, comparing ploughing with subsoiling to 0.3 m. Ploughing brought about 30% more contamination into the topsoil.

Outcome Removal in the shoots was poor: at most 33 mg/m² of trace elements, 62% of it zinc and 18% copper. Fodder radish and sunflower gave the most biomass. Fine roots in the shallow layers were a large sink for the elements, useful for phytostabilisation.

Vamerali T., Bandiera M., Mosca G. In situ phytoremediation of arsenic- and metal-polluted pyrite waste with field crops: effects of soil management. Chemosphere 83, 2011

PhytoremediationField scale, 2005

Sorghum bicolor, Helianthus annuus

The University of Udine (Marchiol, Fellet, Perosa, Zerbi) grew sorghum and sunflower in randomised blocks on soil with As 309, Cd 4.29, Co 50.9, Cu 1,527 and Zn 980 mg/kg, comparing mineral fertiliser, organic amendment and a control, with relief irrigation.

Outcome Fertiliser and amendment raised biomass a great deal but not the metal concentration in the harvested tissue; in some cases organic matter made the elements less available. Zinc removal was about 2,000 g/ha with sorghum and 1,000 g/ha with sunflower: small amounts against what the soil holds.

Marchiol et al., Removal of trace metals by Sorghum bicolor and Helianthus annuus in a site polluted by industrial wastes: a field experience, Plant Physiology and Biochemistry, 2007

Fukushima Daiichi and its fallout area

PhytoremediationField scale, 2011

Helianthus annuus

Trial by Japan's Ministry of Agriculture (MAFF): sunflowers grown on contaminated fields in Iitate and Kōriyama to see whether they would take up radioactive caesium from the soil. It was part of a set of farmland decontamination trials whose results were released on 14 September 2011.

Outcome It failed. With soil at 1,045 Bq/kg (Kōriyama) and 7,715 Bq/kg (Iitate), stems and flowers held 12–79 Bq/kg and roots 64–232 Bq/kg (fresh weight). The caesium sat in the top few centimetres of soil, while sunflower roots reach below one metre. MAFF concluded that plants could not be relied on for decontamination and abandoned the method.

Caesium-137

PhytoremediationField scale, 2012

Helianthus annuus

After the MAFF result, a team led by Osamu Amano (Japan Atomic Energy Agency) had farmers in two districts of Minamisōma grow sunflowers on shallow fields that were tilled first to spread the caesium through the soil, measuring caesium in roots, stems and soil over time.

Outcome The report states that uptake was highest during the most vigorous growth, just before flowering. The amounts removed were not checked for this record.

Caesium-137

Amano O. Results of Removing Radioactive Cesium from the Shallow Rice Fields by Planting Sunflower. Insights Concerning the Fukushima Daiichi Nuclear Accident, vol. 2, aesj.net, 2021

Porto Marghera (Venice)

PhytoremediationField scale

Helianthus annuus, Brassica juncea

In-situ phytoextraction of cadmium, mercury and zinc inside the Porto Marghera industrial area, using two high-biomass crops, sunflower and Indian mustard. The paper reports early results of the ongoing trial and the microcosm and mesocosm tests used to choose the treatments.

Outcome Using EDTA and ammonium thiosulphate together during phytoextraction raised the removal efficiency of Cd, Hg and Zn from the soil (the abstract gives no figures).

Guarino C., Sciarrillo R. The effectiveness and efficiency of phytoremediation of a multicontaminated industrial site: Porto Marghera (Venice Lagoon, Italy). Chemosphere 183, 2017

Chernobyl Exclusion Zone

PhytoremediationField pilot

Helianthus annuus

Rhizofiltration demonstration in a pond near the plant: sunflowers grown on floating rafts with their roots in the water, to remove caesium-137 and strontium-90.

Outcome The University of Hawaii fact sheet reports a 90% reduction in two weeks, with roots concentrating the radionuclides up to 8,000-fold. The review by Lincoln and Noori (2025) notes that after nearly forty years of physical, chemical and biological attempts the contamination persists.