OA: Nitrates

Nitrates?

naturally occurring nitrogen and oxygen bearing inorganic ions

NO3-

Nitrogen Cycle Steps

1. Nitrogen fixation

2. Nitrification

3. Assimilation

4. Ammonification

5. Denitrification

Step 1: Nitrogen fixation

atmospheric nitrogen (N2) fixed to nitrogen bearing compounds + converted to ammonia (NH3)

Step 2: Nitrification

Ammonium (NH4+) oxidised by microorganisms producing nitrite (NO2-) then oxidised into nitrate (NO3-)

Step 3: Assimilation

plants take up ammonium and nitrate ions

Step 4: Ammonification

Organic nitrogen to ammonium by bacteria/fungi

Step 5: Dentrification

Nitrate to nitrogen gas, released back into atmosphere

Haber Bosch Process

industrial method of nitrogen fixation

converts N2 from atmosphere to ammonia

used to fertilise crops

How does the Haber Bosch Process impact global nitrogen cycle

• excessive nitrate levels in water

• human waste causes nitrate pollution of water

Eutrophication

Algal bloom develops in water due to over enrichment of nutrients 

What does the EPA say about eutrophication?

eutrophication biggest pollution problem in Ireland

What is the Nitrates limit?

50mg/l

set by WHO 1958

What is the nitrites limit?

0.5mg/l - tap

0.1mg/l - treated

What is an illness that comes from nitrates?

infantile methemoglobinemia

‘blue baby’

in 2007 how much of people’s water supply had nitrate exceedance?

16,337

The Nitrates Directive

EU Directive

Adopted in 1991

What does the EU Directive aim to do?

protecting water from nitrate pollution arising from agricultural sources

What does the EU Directive make member states do?

to identify and monitor susceptible waters and to protect them

Establish a Nitrates Action Programme that’s reviewed every 4 years

What Nitrate Action Programme is Ireland on?

5th

2022

Who studied Nitrates in Malta?

• British Geological Survey

• NERC Isotope Geosciences Laboratory

• Malta Resources Authority

What are the flow mechanisms?

• fast flow through fissures

• Slower flow through small pores in limestone

What are the Maltese islands composed of?

coralline limestone

‘Blue Clay’ mid layer

underlying Globigerina limestone

What is the cause of high Nitrates in Maltese water?

leaching of nitrate from cultivated soils and possibly from manure piles

What is the movement of the two aquifers

Malta aquifer → 15-40 years

Gozo aquifer → 25-60 years