L6 - Phytoremediation of metals Flashcards
What inorganic pollutants can be phytoremediated?
Nitrate, phosphate, Cr, Cu, Fe, Mn, Zn, Mo
Why does phytoremediation work?
Plants have evolved to deal with toxic compounds and metals and the plasticity of these systems allows them to tackle recently produced synthetic compounds
What is the cost of environmental remediation each year in the world?
$25-30 billion
What is phytoextraction?
use of plants to remove metals by absorption from soil and conc in shoot tissues
what is Phytodegradation?
Absorption and conversion of contaminants by metabolism in root or shoot
What is phytostimulation?
Root stimulation of microbial degradation of contaminants
What are the environments of phytoremediation?
Low maintenance Minimally disruptive Cheap Aesthetically pleasing Compatible with restoration ecology
Disadvantages of phytoremediation?
Limited by root depth Slow Limited by climate and soil Limited by bioavail of pollutants Limited by toxicity of pollutants
What is constructed wetland?
Waste water comes in, cleaned by plants and then is drained to other rivers
How do plants take in organic pollutants and why?
Diffuse across membrane because they are man made and so are xenobiotic so plants have no specific transporters
What happens if the organics are too hydrophilic or too hydrophobic?
Hydrophilic ( Kow 3) get stuck in membrane
How are inorganics taken up?
Membrane transporter proteins
What state are most inorganics in in soil and why?
Most oxidised form because most soils are oxidising
What inorganics are similar to nutrients and so are taken up by transporters?
Arsenate looks like phosphate
Selenate looks like sulphate
What happens to toxic pollutants after they’re taken up?
- Sequestered to vacuole or cell wall
- Pollutants bound to chelators or conjugates
What are toxic inorganics commonly bound to after uptake?
Glutathione or phytochelatins
What is phytovolatilisation?
Release of pollutants from plant as a gas
What can be phytovolatilised?
Inorganic Se
Why is phytovolatilisation attractive?
No need to harvest the plant
What kind of pollutants can be degraded by plants?
Organic pollutants
What is involved in degradation of pollutants?
Plant enzymes act to catabolise them to CO2 or partially degrades to compartmentalise
What enzymes are involved in degradation?
Dehalogenases, monooxygenases, dioxygenases, peroxidases, nitrilases, phosphatases, ntiroreductases
What are the most common heavy metals at hazardous waste sites?
Cadmium Chromium Copper Lead Mercury (most toxic) Nickel Zinc
How much mercury does WHO say are released each year?
10000 tons
How does phytoremediation help with heavy metals?
Metals precipitate within root zone
What is phytoextraction?
Use of metal-accumulating plants to remove metals or metalloids from soil by concentrating them into the harvestable parts
What are the key processes in metal hyperaccumulation?
Metal acquisition - uptake
Chelation - ligands chelate in root to minimise toxicity
Translocation - transport to shoot in xylem
Shoot Accumulation - chelation in cytoplasm, transport to vacuole
What is the 1st approach to phytoextraction?
Metal-hyperaccumulator plants - low biomass but high conc
What is the 2nd approach to phytoextraction?
Selected cultivars of crops like Brassica juncea - high biomass, enhanced metal uptake
What is the 3rd approach to phytoextraction?
Fast growing, high biomass woody crops like Salix and Populud selection lines
How can you optimise the candidate plant for phytoextraction?
Select line with highest potential yield
Improve metal uptake by conventional breeding or GM
How can you optimise the agronomy for phytoextraction?
Sowing density, timing, harvest
Fertiliser
Irrigation, weed and pest control
How can you optimise the rhizosphere for phytoextraction?
Apply amendments to increase bioavail
Innoculate bacteria
What is phytomining?
Growing crops on soil with metal conc too low for conventional exploitation to then burn and smelt
What is induced hyperaccumulation and why is it done?
Making gold soluble and making plants take it up using natural chemicals
