Zea mays

How it works

Mechanisms: phytoextraction

Contaminants

Contaminant	Evidence	What was shown
Zinc	field	Field experiment in the Belgian Campine, a region of about 700 km² contaminated by historic deposition of Cd, Zn and Pb: annual reduction of 0.4–0.7 mg/kg Zn in the topsoil; very low removal for Cd and Pb. The crop can give 33,000–46,000 kWh of renewable energy per hectare per year (Meers et al. 2010). Meers et al., The use of bio-energy crops (Zea mays) for phytoattenuation of heavy metals on moderately contaminated soils: a field experiment, Chemosphere 78:35, 2010
Cadmium	field	In the same experiment cadmium removal was very low (Meers et al. 2010). Intercropped with Sedum plumbizincicola, maize grain stayed within the Chinese national Cd limit while the hyperaccumulator extracted the metal (Deng et al. 2016). Meers et al., Chemosphere 78:35, 2010 Deng et al., Long-term field phytoextraction of zinc/cadmium contaminated soil by Sedum plumbizincicola under different agronomic strategies, Int. J. Phytoremediation 18:134, 2016

Contaminant

Evidence

What was shown

field

Field experiment in the Belgian Campine, a region of about 700 km² contaminated by historic deposition of Cd, Zn and Pb: annual reduction of 0.4–0.7 mg/kg Zn in the topsoil; very low removal for Cd and Pb. The crop can give 33,000–46,000 kWh of renewable energy per hectare per year (Meers et al. 2010).

Meers et al., The use of bio-energy crops (Zea mays) for phytoattenuation of heavy metals on moderately contaminated soils: a field experiment, Chemosphere 78:35, 2010

Cadmium

field

In the same experiment cadmium removal was very low (Meers et al. 2010). Intercropped with Sedum plumbizincicola, maize grain stayed within the Chinese national Cd limit while the hyperaccumulator extracted the metal (Deng et al. 2016).

Limits

It does not clean up: under 1 mg/kg of zinc per year, almost nothing for cadmium and lead. It is risk management that makes sense only if the biomass has an outlet (biogas) and metals in the digestate are kept under control.

Where it has been tried

Kasur tanneries

PhytoremediationGreenhouse, with soil from the site

Pot trial on tannery-polluted soils from Kasur and Sialkot: four maize cultivars with and without 3% biochar. This is not phytoextraction: the aim is to immobilise chromium and let the crop grow.

Outcome Biochar lowered the available chromium fraction in soil and Cr(VI) and Cr(III) in roots and shoots, and raised height, biomass and photosynthesis; cultivar P-1543 was the most tolerant in both soils. The abstract gives no percentages.

Bashir M.A. et al. Biochar Mediated-Alleviation of Chromium Stress and Growth Improvement of Different Maize Cultivars in Tannery Polluted Soils. International Journal of Environmental Research and Public Health 18(9), 2021

Janghang smelter

Microbial bioremediationLaboratory, with soil from the site

Rhodococcus aetherivorans, Pseudomonas koreensis, Zea mays

Isolation of 21 arsenic-tolerant bacteria from soils near to and away from the smelter (genera Brevibacterium, Pseudomonas, Microbacterium, Rhodococcus, Rahnella, Paenibacillus) and laboratory testing of their plant-growth-promoting traits, with assisted phytoremediation in mind.

Outcome All 21 isolates produced indole acetic acid, 12 produced siderophores and 17 solubilised phosphate. Rhodococcus aetherivorans JS2210, Pseudomonas koreensis JS2214 and Pseudomonas sp. JS238 increased maize root length in the presence of 100 and 200 µM arsenate. No field test (Shagol and colleagues 2014).