Nitrates

Question 0

What type of organism are the only ones able to make atmospheric nitrogen usable?

Answer 0

Bacteria

Question 1

What is the most abundant element in our atmosphere?

Answer 1

Nitrogen ~ 80%

Question 2

How is usable nitrogen added to the earth each year?

Answer 2

Biological fixation ~ 50%
Adding fertilisers to crops ~ 45%
High energy fixation (nitrates as nitric acid in rainwater) ~ 5%

Question 3

What enzymes catalyse the splitting of N2?

Answer 3

Feredoxin, nitrogen reductase and nitogenase

Question 4

Chemical formula for production of ammonia?

Answer 4

N2 + 3H2 —> 2NH3

Question 5

Types of nitrogen fixers?

Answer 5

Most important free living fixers in the genus Clostridium
Most important aquatic fixers include Cyanobacteria like Anabaena
Some bacteria also associate with plants in root nodules (esp. Legumes), genus Rhizobium
Some non-legumes plants also have nodules (eg. Alder, tea, olive)

Question 6

Which genus’ can further oxidise ammonia/ammonium into nitrate and nitrite?

Answer 6

Nitrosomonas and Nitrobacter

Question 7

What is the process called where N2 is returned to the environment and name a genus of bacteria that do this?

Answer 7

Denitrification - Pseudomonas

Question 8

How has agriculture increased nitrogen in aquatic environments?

Answer 8

Land conversion exposes soil to elements, nitrates leach easily
Soil cultivation speeds up decomposition (soil microbial activity) and associated leaching
Harvesting removes nitrogen (fertilisers used)
Farm specialisation (point source pollution: livestock, fish farms)

Question 9

What 4 impacts can increased nitrate levels have?

Answer 9

Acidification of water
Eutrophication
Toxicity to aquatic life
Toxicity to humans

Question 10

What does acidification of aquatic environments increase?

Answer 10

Trace metals (aluminium, lead, cadmium etc)

Question 11

Effects of acidification of water?

Answer 11

Decline in invertebrate species (esp. Crustaceans)
Decline in fish (esp. Salmonids)
Microbial activity in freshwater is impaired below pH 5, stopping or slowing decomposition

Question 12

What do algal blooms lead to?

Answer 12

Decreased light penetration (productivity of deep water plants diminishes)
Algae die and decomposition proceeds leading to an increase in biological oxygen demand (BOD) so decreasing dissolved oxygen content (hypoxia)
Examples - Baltic Sea, Black Sea, Gulf of Mexico

Question 13

Less oxygen leads to?

Answer 13

Death of invertebrate species
Death of fish
Build up of hydrogen sulphide (toxic to many aquatic species)

Question 14

What kind of algae can produce toxins?

Answer 14

Cyanobacteria, dinoflagellates and diatoms

Question 15

Why are non heterocystous species of blue green algae dangerous to aquatic life?

Answer 15

Cannot fix N2
Most common bloom forming genus is Microcystis which produces the toxin microcystin (this can kill fish and various invertebrates)

Question 16

What are the characteristics of Dinoflagellates?

Answer 16

Red-brown algae (eukaryotes)
Produce so-called red tides
Most well known genus are Karenia
Produce numerous toxins that can kill both vertebrates and invertebrates
Clear link with elevated levels of nitrate in water courses

Question 17

Characteristics of diatoms?

Answer 17

Eukaryotic siliceous algae produce the neurotoxin Domoic acid
Kills vertebrates and invertebrates
Linked to elevated nitrate levels

Question 18

Elevated nitrate levels in water can have what effects on humans?

Answer 18

Methaemoglobinaemia
Various cancers
Illness related to toxins from algal blooms

Question 19

What is methaemoglobinaemia?

Answer 19

Blue baby syndrome
Nitrates convert to nitrites in digestive tract
Nitrites react with haemoglobin to form methaemoglobin which has reduced oxygen transport capacity
Occurs when normal methaemoglobin levels rise from 1-3% to over 10%
Causes tachycardia, cyanosis, convulsions, coma and ultimately death

Question 20

Why are infants more at risk of methaemoglobinaemia?

Answer 20

Larger fluid intake relative to body size
Fetal haemoglobin has a high affinity for nitrite
Higher stomach pH favours nitrite/haemoglobin reaction
Lower levels of methaemoglobin reductase activity

Question 21

Why is elevated nitrates a cancer risk?

Answer 21

Formation of dimethylnitrosamines in digestive tract
Caused by nitrite and amines (from meat) reacting
Cancers include stomach, oesophageal and colorectal

Question 22

Other effects of elevated nitrates to humans and other vertebrates?

Answer 22

Algal toxins - blooms can lead to rashes, vomiting, fever, pneumonia etc
Paralytic shellfish poisoning - approx 2,000 cases per year with some fatalities. Caused by exposure to toxins concentrated in shellfish
Amphibians in worldwide decline possibly because of exposure to nitrite and nitrate

Question 23

What is the aim of EU act (91/676/EC)?

Answer 23

To reduce nitrate levels in ground and surface waters caused by agricultural sources - manure/chemical fertilisers
Directive requires member states to establish action plans (by 1996) on areas designated as nitrate vulnerable zones (NVZs)

Question 24

What water courses are regarded as NVZs?

Answer 24

Nitrate levels are above 50mg/L
Where eutrophication exists (algal blooms etc)
Where water body may become eutrophic

Question 25

How much of Scotland and England are NVZs?

Which countries are designated 100% NVZs?

Answer 25

Scotland - 20% of land on East Coast
England - 68 identified mostly in Midlands expanded in 2012
Germany Sweden and Denmark designated 100%

Question 26

What are the action plans, assistance and policing of the act 91/676/EC?

Answer 26

Plan - farms must have sufficient manure storage capacity
Fertiliser applications based in crop requirements
Livestock manure limited to 170kg N/ha/year
Records on fertiliser application kept
No application to steep slopes if rain is forecast
Assistance - Grants up to 40% available to help with manure storage
Policing - SEPA in Scotland and Environment Agency in England

Question 27

What is the aim of act (2000/60/EC)?

Answer 27

Water framework directive
Requires much broader range of measures (not just nitrates)
Waters must meet certain standards by 2015 (good chemical and ecological status)
Initial characterisation and implementation of measures by end of 2006