Heavy Metal Pollution Flashcards
Are trace metals a source of pollution?
Yes, they are the main source of metal toxicity in the environment
What are trace metals defined as?
Occurring at 1000 parts per million or less in the earth’s crust
Are all metals toxic and persistant?
All metals are persistent but not all are bio-accumulative or toxic
What are the three groups of metals that are of biological concern?
-Light metals (< 5 gcm-3)
-Transitional metals
-Metalloids (Heavy metals >gcm-3)
What are some examples of light metals?
Sodium, potassium, calcium
-Normally transported as mobile cat ions in aqueous solutions
What are some examples of transitional metals?
Iron, copper, cobalt
-Essential at low concentrations but may be toxic at high concentrations
What are some examples of heavy metals?
Mercury, lead, arsenic,
-Not required for metabolic activity and toxic at low concentrations
What does PBT stand for?
Persistent, Bio-accumulative and toxic
What nutrient metals are not PBT?
Iron (Fe), Manganese (Mn), Vanadium (V)
What are five nutrient metals that are persistent, bio-accumulative and toxic?
Copper (Cu), Nickel (Ni), Zinc (Zn), Selenium (Se), Chromium (Cr)
What are five non-nutrient metals that are PBT?
Antimony (Sb), Arsenic (Ar), Cadmium (Cd), Mercury (Hg) Lead (Pb)
What is the most toxic heavy metal?
Mercury (Hg)
List natural sources of heavy metal pollution
-Normal geological formations (ore formations)
-Weathering of rock and leaching
-Degassing (Hg and Volcanoes)
-Forest Fires
-Food and drinking water
What is degassing?
Is the removal of dissolved gases from liquids, especially water or aqueous solutions
What are some anthropogenic sources of heavy metals?
-Burning fossil fuels
-Mining, smelting and processing metal ores
-Discharging industrial, agri. domestic waste and effluent
-Application of pesticides fungicides and fertilisers
-Paints, dyes, leather, rubber, textiles etc.
-Oil spills
What heavy metal is present in haemocyanin (molluscs and crustaceans respiratory pigment)
Copper (Cu)
What heavy metal is present in haemoglobin? (vertebrates and invertebrates )
Iron (Fe)
What heavy metal is in respiratory pigments of tunicates?
Contains V (Vanadium)
How do organisms obtain essential heavy metals?
-Uptake is by passive diffusion
-Active transport systems
-Food and water
-At higher doses than those needed for nutrition, metals can be toxic
Why are metals permanent additions to the environment?
Metals are not subject to bacterial degradation
How can heavy metals impact the environment?
-Impact the physiology and/or behaviour of an organism
-Reduce growth, reproduction and survival
-Can indirectly effect organisms by reducing their prey
What are organo-metal complexes?
-When heavy metals bind with organic substances
Describe organo-metal complexes?
-They bind hydric soils (eg. Al, Fe with phosphate)
-Can reduce their toxicity
-Many organo-metal complexes are extremely toxic to aquatic organisms
Do heavy metals move up the food chain?
Yes, the effects of heavy metals can become severe as they pass through the food chain
(Bioaccumulation and Biomagnification)
How do heavy metals enter aquatic ecosystems?
-Atmosphere dust and acid rain
-Run off from land and sediment
-Direct discharge
What occurs in severely effected areas by heavy metals, when organisms are absent and scarce?
-Large inter-specific variation in responses to heavy metals
-Toxicity also depends on environmental conditions
-Sensitivity within a taxonomic group differs between fresh and salt water
What are the normal concentrations of heavy metals in freshwater?
-Naturally low metal concentrations
-Higher concentrations cause adverse effects to aquatic organisms
What are the normal concentrations of heavy metals in marine waters?
-Naturally higher concentrations than in freshwater
What is the estimated input of Hg (Mercury) into the sea?
6000-7500 tons which 50-75% is a result of human activity
What organisms are very sensitive to organo-mercurical fungicides?
Phytoplankton, just 0.001 ppm reduces photosynthetic efficiency
Why are plants suspectable to Hg?
Algae and plants have the ability to absorb and concentrate Hg from surrounding environment with high concentrations killing the plants
Do animals accumulate Hg?
Yes, usually through their food
What happens to Hg in the marine environment?
Most forms of Hg are converted methly mercury
Where does fish eating seabirds accumulate Hg?
In their feathers (biomagnification) and feathers are lost when the birds moult
What happens to long-lived fish in regards to Hg?
Fish like tuna and swordfish accumulate Hg 3000 times higher levels than that of their surrounding waters and are dangerous for human consumption (bioaccumulation)
What does an increase of 20 degrees temperature cause in relation to toxicity?
Can produce a 100 fold increase in toxicity of Cd, Cu, Pb, Hg, Ni and Zn
What is the estimated total inputs of Cd to oceans?
8000 t yr-3 from human activites
What does Cd exposure do to blue mussels (Mytilus edulis)
Inhibited DNA repair, causing genetic damage
Does Cd absorb into tissues?
Plants and animals readily absorb Cd and accumulate concentrations in their tissues
What does Copper (Cu) and Zinc (Zn) do to corals?
Can impair reproduction in corals via reduced fertilisation success
What are the effects of Lead (Pb) in the environment?
-High concentrations accumulate in organisms, sometimes not causing harm like impets, seaweeds, mussels
-Effects reproduction in birds
-Decreased egg production, hatchability and increased hatchelling mortality
-Young, growing birds more sensitive
What are the effects of arsenic in the environment?
-Accumulates along the food chain, crabs and lobsters worst affected
-Algae, crustaceans and fish bioaccumulate As
What organisms are most sensitive to heavy metal pollution?
Crustaceans
What organisms are not as sensitive to heavy metal pollution?
Annelids
What are some options to remove heavy metal pollution from environment?
-Removed from sediments by dredging
-Sediments can be capped with sand and fine particles that absorb heavy metals
-Wetland creation (Phragmite australis and Lemna minor are tolerant to heavy metals and absorb them)
-Dead plant matter binds to heavy metals and remove them from environment
How does heavy metals contaminate Irish waters?
Cadmium and mercury released to the atmosphere by fossil fuels and end up in water bodies from atmospheric deposition
What is another source contaminating Irish waters?
-Historic mining activates
-Emissions from waste-water treatment plants are sources of cadmium, lead and mercury
In 2021, how many surface water bodies failed to achieve good chemical status?
173 (50%) out of 349 failed (EPA 2021)
What was 87 (26.4%) of the failures due to? (EPA 2021 report)
Due to substances containing metals,
-Cadmium
-Lead
-Mercury
