Inorganic Nutrient Pollution - Eutrophication

No - it’s a natural process as nutrients are washed in and accumulate, supporting increasingly rich food webs

PHOSPHATES - sewage effluent - eroded soil particles NITRATES - washed off farmlands - artificial fertilisers (leachate)

Phosphates Nitrates • these are often the limiting factors of plant growth in ecosystems

the enrichment of a water body with nutrients, usually with an excess amount of nutrients. As a result, plants and algae grow and may result in oxygen depletion of the water body

eutrophication can be natural over time, cultural eutrophication is a result of human activities discharging inorganic nutrients into an aquatic system

• discharge of phosphate-containing detergents • fertilisers • sewage • clearing land • run off this results in large quantities of nutrients that build up relatively rapidly

cultural eutrophication human health impacts baby impacts cancer

• Oligotrophic lakes • Eutrophic lakes • Algae and cyanobacteria proliferation

OLIGOTROPHIC - few nutrients - little plant growth e.g. mountain lakes EUTROPHIC - rich in nutrients - abundant plant growth e.g. lowland lakes

Algae and cyanobacteria absorb their nutrients directly from the water, not from the sediments - this means that dissolved nutrients are used more easily although their levels may fluctuate rapidly. Algal growth leads to a range of probs: • cyanobacteria can release harmful toxins which can affect livestock, pets and people who drink or are in contact with the water e.g. blue green algae in lakes affect water sports • floating algae shade the submerged or rooted macrophytes (larger plants) which cannot photosynthesise. This means the plants may die which disrupts food webs and their decay by aerobic bacteria may cause deoxygenation • algae are an unreliable food source and do not support rich food webs as they can die off rapidly if nutrients become depleted, or if other conditions are not ideal e.g. light or temperature

• nitrates are very soluble and may get into drinking water supplies • they may be ingested in processed food e.g. nitrites added to bacon to give it a smoky flavour

At the end of summer, when warm temperatures cause dead vegetation to decay rapidly, the resulting deoxygenation kills off animal life. Deoxygenation is a particular problem at night when there is no photosynthesis to replace lost oxygen

• unpolluted lake with rich food webs and high macrophyte diversity • phosphates from sewage effluent and nitrates from farmland wash into the water system • Algae absorb nutrients and grow more rapidly than macrophytes. Algae shades macrophytes which reduces photosynthesis • shaded macrophytes die, macrophytes die, macrophyte-based food chains broken, higher trophic levels lose food • decomposition of dead macrophytes reduces dissolved oxygen levels • some algae (b-g algae or cyanobacteria) release toxins • livestock drink water and may die • algae die when nutrients run out. Decomposition by bacteria depletes dissolved oxygen, killing fish, insect larvae and other aerobic organisms • sediments formed of dead algae may be disturbed by storms, releasing nutrients and causing further algal blooms

BLUE BABY SYNDROME - an infant born with a congenital heart defect - nitrates are not very toxic but bacteria in the gut convert them to nitrites which react with haemoglobin in the blood and reduce its ability to carry oxygen - gives the skin a bluish tint - infants especially at risk as they have more of the necessary bacteria and their haemoglobin reacts more rapidly with nitrites (methaemoglobinaemia)

• groundwater contaminated by leaching of nitrate from fertiliser used in agricultural lands and waste dumps (usually only a problem with water from shallow wells receiving drainage water from arable farmland) • ingested as food additives in meat, cheese and fish products • may also be related to some pesticides (DDT, PCBs etc) which cause ecotoxological problems in the food chains of living orgs, increasing biochemical oxygen demand which kills aquatic animals

• some UPF have nitrates in them, e.g. nitrates in bacon give it a smoky flavour • gut bacteria convert nitrates to nitrites • these may then be converted into nitrosamines which are carcinogenic and may cause stomach cancer HOWEVER most research has been carried out on rats and the link between nitrates in water supplies and cancer is not conclusive

designated areas of the UK at risk from nitrate pollution (from a combination of land use and pollutant pathways) • areas where water aquifers are close to the surface and could easily become contaminated

55%

• reduced use of nitrate fertilisers • reduced ploughing at times of heavy rain • use of soluble, rapid-release fertilisers • the deposition of waste manure where the nutrients will not leach into the ground or be washed into a river • reducing the cultivation of crops that have higher nitrogen requirements e.g. replacing wheat with triticale • reducing the reliance on artificial fertilisers e.g. by growing more legume crops that have nitrogen-fixing root nodule bacteria • adsorbent properties of iron sulfate • dredging lakes and rivers • riparian buffer strips

• the adsorbent properties of iron sulfate removes phosphate from liquid efflue ents released by sewage treatment works • the phosphates are precipitated as a fine sediment of iron phosphate e.g. Phoslock - during application, it moves through the water column, and binds Free Reactive Phosphorus (FRP), locking it permanently. Afterwards, it continues to bind FRP released from sediments

removing the phosphate-rich sediments from past pollution - can also add iron sulfate to reduce the solubility of the phosphates stirred up

VEGETATION: - physical filtration - nutrient uptake by plants - enhanced infiltration ALSO - microbial processes in soil

PROS - habitat and ecosystem services - no destruction - soil erosion control (roots) CONS - farmers not impressed with cutting across farmland - if the flow is too much/too fast, it can have limited effectiveness as it goes straight through

PROS - cost effective and widely used - protects all water systems e.g. rivers, lakes, coast, ocean as the cleaned water can now spread freely - prevents eutroph and serious ecological food web damage CONS - the chemical sludge generated by the use of the iron sulfate can require proper disposal and management which can be a proper operational challenge - adding the iron sulfate alters the pH levels of the water making it more acidic. Needs remediation such as crushed lime which is a faff and expensive