Plant tables for phytoremediation

Plant tables for phytoremediation

No single plant cleans all impurities equally well. Selection is based on three parameters:

What pollutes the area:metal, petroleum product, solvent, radionuclide.

Where is the pollution located:topsoil, water, sediment, or groundwater.

What result is required:extraction, stabilization, decomposition or interception of contaminated water.

Phytoremediation is most applicable whendiffuse pollution of low or medium intensity, located within the rootsHeavily contaminated localized spots typically require removal, containment, or engineering treatment. EPA considers plants to be a means of removing, degrading, or retaining metals, petroleum products, PAHs, pesticides, solvents, explosives, radionuclides, and leachates.US EPA)

Conventional designations

E- phytoextraction: the pollutant accumulates in the plant, the biomass is removed.

With- phytostabilization: the pollutant is retained in the soil and roots.

R- rhizodegradation: the pollutant is destroyed by root microorganisms.

FD- phytodegradation within the plant or by its enzymes.

Russian Federation- rhizofiltration of contaminated water.

G- phytohydraulic water interception.

IN- phytovolatilization: transformation and release of the volatile form.

1. Cadmium, zinc, nickel, copper and arsenic

Plants for extracting metals from soil

Fast-growing willows and poplars are beneficial for Zn and Cu: they usually do not reach the concentrations of specialized hyperaccumulators, but compensate for this with high biomass and a developed root system. (research.fs.usda.gov)

The best choice for metal

Important Arsenic Limitation

Pteris vittatacan effectively accumulate arsenic, but the plant is capable of altering its chemical form. Therefore, collection, storage, and disposal of the fern should be carried out as with contaminated biomass.nepis.epa.gov)

2. Lead, chromium, copper and waste from mines and metallurgy

For such areas, what is needed is not a quick cleaning, butstable fixation of dusty waste and cessation of erosion.

Plants for phytostabilization

Plants growing on metallurgical and mine waste often retain metals in their roots, rhizosphere, and sediment rather than removing them from the site. For example, in reeds, Fe, Cu, Zn, Pb, and Cd may be concentrated primarily in the root zone with little transfer to the shoots.ARS)

Chromium

In studies withTypha latifolia And Carex luridaPlants and root secretions contributed to the formation of reducing conditions in which Cr(VI) was converted into less mobile Cr(III).ARS)

Lead

For Pb the basic set:

fescue;

ryegrass;

fieldfare;

miscanthus;

cane;

willow;

mustard - mainly for experimental plots;

Sunflower - mainly for rhizofiltration or testing.

Lead is generally poorly transported from the soil to above-ground organs. Therefore, the main goal isprevent it from becoming dusty, washed out, and entering the food chain.

3. Oil, diesel, PAHs and pesticides

Organic contaminants are mainly removed through the interaction of roots, bacteria and fungi.

Soils contaminated with oil and diesel

In one comparative study, sedge, switchgrass, and gamagrass reduced petroleum hydrocarbon residues more effectively than woody plantings, but PAH results were highly dependent on soil, availability, and the activity of the plant's own microflora. Even the same plant species can produce different results at different sites.ARS)

Pesticides and herbicides in water and wastewater

Vegetation ditches and artificial bogs do not necessarily destroy all the pesticide: some of the substance may be temporarily retained in vegetation and sediment. Therefore, analysis of water, sediment, and biomass is necessary.ARS)

4. Herbicides, solvents and explosives

Chlorinated solvents and BTEX

EPA indicates that phytotechnologies have been applied or tested for TCE, other chlorinated solvents, BTEX, petroleum products, and contaminated groundwater. (US EPA)

Explosives

Species selection for TNT and RDX cannot be made solely on the basis of literature tables: EPA notes the need to consider byproducts, stocking density, contamination depth, and groundwater behavior of the substance. (nepis.epa.gov)

5. Metals, radionuclides and contaminated wastewater

Rhizofiltration of water

When purifying water, metals often don't migrate high into the leaves, but rather bind to the roots, iron deposits on the roots, and bottom sediment. This means that it's necessary to periodically remove not only the plants, but sometimes the contaminated sediment as well.ARS)

Radioactive contamination

For radionuclides, a plant should not be selected without a radiological project. The IAEA emphasizes that the transfer of cesium and other radionuclides depends on soil properties and plant species; in many cases, reducing the uptake by crops, growing non-food products, adding binding materials, or removing the topsoil prove more reliable than attempting complete phytoextraction.www-pub.iaea.org)

6. Contaminated groundwater and leachates

Woody plants for phytohydraulic control

Depth limitation

Trees only work where their roots or capillary water can actually reach. Old EPA guidelines for willows and poplars provide an approximate working depth of several meters, but the actual depth depends on soil, oxygen, water levels, and tree species.US EPA)

Filtrate purification system

In practice, the following sequence works better:

accumulation basin → sedimentation of suspended matter → cattail and reed zone → rush and sedge zone → willow plantation → control pond.

7. Selenium, mercury and volatile organic compounds

Phytovolatilization

Phytovolatilization is not automatically considered cleanup: the contaminant may simply migrate from soil or water into the atmosphere. EPA requires an assessment of the final fate of the contaminant and the acceptability of its transformation products.US EPA)

For mercury, this approach is particularly controversial. In a typical environmental area, it's safer to consider:

source isolation;

soil binding;

prevention of methylation;

controlled water purification;

removal of the most contaminated areas.

8. Quick selection of plants for a task

9. Preferred scheme for Central Europe and Switzerland

For a moderate climate, a practical perennial set:

Dry contaminated soils

red fescue;

reed fescue;

ryegrass;

fieldfare;

miscanthus;

birch;

pine;

goat willow.

Wet soils

white willow;

basket willow;

poplar;

black alder;

soddy pike;

a sieve;

sedges.

Sewage treatment swamps

rug;

cane;

reed;

a sieve;

sedges;

controlled duckweed.

Trial extraction plots

mustard;

sunflower;

Noccaea caerulescens;

Pteris vittata- only in a suitable microclimate or closed system;

specialized nickel hyperaccumulators.

Before introducing non-native plants, check their invasiveness and their permitted status. Water hyacinth and some fast-growing exotics are only permitted in sealed, process-based environments, not in the wild.

Mandatory rule for handling the harvest

All biomass from phytoextraction sites should be considered potentially contaminated.

It is not allowed:

to eat;

use as medicinal raw material;

feed to animals;

place in regular compost;

to scatter as mulch;

burn in an oven;

use for home biochar.

EPA specifies that plants that have accumulated contaminants must be collected and sent for controlled processing or disposal; thermal processing preserves the metals and concentrates them in the ash. (US EPA)

The main principle

Metals do not decompose:they are extracted or stabilized. Oil, diesel, PAHs, pesticides and solvents can decompose, but the effectiveness is determined by microflora, oxygen, humidity and the availability of the pollutant. Radionuclides require a separate radiological project. Plants are part of the system, not a replacement for analysis, hydrogeology and safe disposal.