Lolium perenne

How it works

Mechanisms: rhizodegradation

Contaminants

Contaminant	Evidence	What was shown
Petroleum hydrocarbons	field	At ten refinery sites (13.7 g/kg hydrocarbons on average), ryegrass and alfalfa with nitrogen fertiliser and tillage: 72–90% decontamination in a year, against five years with natural vegetation alone (Panchenko et al. 2023). Panchenko et al., Natural and technical phytoremediation of oil-contaminated soil, Life 13:177, 2023
Polycyclic aromatic hydrocarbons	greenhouse	Soil contaminated with PAHs since World War II, in pots for 12 and 18 months: after one year the 15 PAHs monitored fell to 50%, with fluoranthene and pyrene best degraded and benzo[a]pyrene also declining; mostly, however, with no significant difference between pots with ryegrass and pots with soil microflora alone (Rezek et al. 2008). Dissipation of 3–6-ring PAHs in the rhizosphere is the subject of Binet et al. (2000). Rezek et al., The effect of ryegrass (Lolium perenne) on decrease of PAH content in long term contaminated soil, Chemosphere 70:1603, 2008 Binet et al., Dissipation of 3–6-ring polycyclic aromatic hydrocarbons in the rhizosphere of ryegrass, Soil Biol. Biochem. 32:2011, 2000

Contaminant

Evidence

What was shown

field

At ten refinery sites (13.7 g/kg hydrocarbons on average), ryegrass and alfalfa with nitrogen fertiliser and tillage: 72–90% decontamination in a year, against five years with natural vegetation alone (Panchenko et al. 2023).

Panchenko et al., Natural and technical phytoremediation of oil-contaminated soil, Life 13:177, 2023

Polycyclic aromatic hydrocarbons

greenhouse

Soil contaminated with PAHs since World War II, in pots for 12 and 18 months: after one year the 15 PAHs monitored fell to 50%, with fluoranthene and pyrene best degraded and benzo[a]pyrene also declining; mostly, however, with no significant difference between pots with ryegrass and pots with soil microflora alone (Rezek et al. 2008). Dissipation of 3–6-ring PAHs in the rhizosphere is the subject of Binet et al. (2000).

Limits

Roots in the top 20–30 cm: it does not reach deep contamination. For aged PAHs the limiting factor is bioavailability, which the plant does not always improve (Rezek et al. 2008); dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene did not decline. In the field the plant's effect cannot be separated from that of fertiliser and tillage.

Where it has been tried

Monchegorsk nickel-copper smelter and industrial barren

PhytoremediationGreenhouse, with soil from the site

Perennial ryegrass grown on soils contaminated by the Kola Peninsula nickel-copper smelter, with and without natural iron-manganese nodules from the Gulf of Finland as an immobilising agent; plants and microorganisms were compared as indicators of success. The scale (pot or plot) is not stated in the abstract.

Outcome The nodules lowered soluble metals and shoot metal content and clearly improved growth. Among microbial indicators, community-level physiological profiling, biomass carbon and basal respiration responded; bacterial and fungal counts and enzyme activity proved unreliable.

Dovletyarova E.A. et al. Sensitivity of microbial bioindicators in assessing metal immobilization success in smelter-impacted soils. Chemosphere, 2024

Quintero-Puchuncaví (Ventanas industrial complex)

PhytoremediationLaboratory, with soil from the site

Lolium perenne

Aided phytostabilisation on acidic soils from the Puchuncaví valley: laboratory test of locally available amendments (seashell grit, biosolids, natural zeolite and iron-activated zeolite), with perennial ryegrass as the indicator of phytotoxicity.

Outcome Bringing the soil to pH 6.5 with seashell grit significantly lowers copper and zinc solubilisation without raising that of arsenic, and removes phytotoxicity and excessive accumulation in shoots. Above pH 6.5, with biosolids or zeolite, arsenic in pore water rises.