Transcript Nitrogen cycle

Environmental Chemistry:
Nitrogen (N)
Or….why we need healthy soils!
N – So what??!!
• What do plants need to live and grow?
• “Nutrients” – what are they?
• 17 Essential Elements
– C, H, O
– N-P-K
– Ca, Mg, S
– Micronutrients: B, Cu, Cl, Fe, Mn, Mo, Ni, Zn
The Nitrogen Cycle
• N2 makes up 78% of troposphere (inner-most
layer of atmosphere)!
• Nitrogen fixation: turning nitrogen in the
atmosphere (N2) into a usable form for plants
• N2 + 3H2
2NH3 (ammonia)
• Bacteria do this (in soil, or living in nodules in
special plants called legumes)
• Industrial fertilizer factories do this
• NH3 quickly dissolves into NH4 + (ammonium
ions)
GASEOUS NITROGEN
(N2) IN ATMOSPHERE
NITROGEN
FIXATION
by industry for
agriculture
FOOD WEBS
ON LAND
FERTILIZERS
NITROGEN FIXATION
bacteria convert to ammonia
(NH3) ; this dissolves to form
ammonium (NH4+)
uptake by
autotrophs
excretion,
death,
decomposition
uptake by
autotrophs
NITROGENOUS WASTES,
REMAINS IN SOIL
NO3IN SOIL
AMMONIFICATION
NH3, NH4+
IN SOIL
loss by
leaching
by bacteria
2. NITRIFICATION
bacteria, fungi convert the
residues to NH3 , this
dissolves to form NH4+
bacteria convert NO2- to
nitrate (NO3-)
1. NITRIFICATION
NO2IN SOIL
bacteria convert NH4+
to nitrite (NO2-)
DENTRIFICATION
loss by
leaching
Fig. 4.30, p. 94
The Nitrogen Cycle
• Nitrification: a two-step process
• 1: Bacteria convert nitrogen in the soils
(NH3 and NH4 + ) to two different forms
– Nitrite ions (NO2-) BAD!! TOXIC! UNUSABLE!
– Nitrate ions (NO3-) GOOD NUTRIENTS FOR
PLANTS!
• 2: Bacteria convert nitrite ions (bad, NO2)
to nitrate ions (good, NO3-) that can be
used by plants!
GASEOUS NITROGEN
(N2) IN ATMOSPHERE
NITROGEN
FIXATION
by industry for
agriculture
FOOD WEBS
ON LAND
FERTILIZERS
NITROGEN FIXATION
bacteria convert to ammonia
(NH3) ; this dissolves to form
ammonium (NH4+)
uptake by
autotrophs
excretion,
death,
decomposition
uptake by
autotrophs
NITROGENOUS WASTES,
REMAINS IN SOIL
NO3IN SOIL
AMMONIFICATION
NH3, NH4+
IN SOIL
loss by
leaching
by bacteria
2. NITRIFICATION
bacteria, fungi convert the
residues to NH3 , this
dissolves to form NH4+
bacteria convert NO2- to
nitrate (NO3-)
1. NITRIFICATION
NO2IN SOIL
bacteria convert NH4+
to nitrite (NO2-)
DENTRIFICATION
loss by
leaching
Fig. 4.30, p. 94
The Nitrogen Cycle
• Denitrification: special bacteria in
waterlogged soil or at the bottom of lakes,
oceans, or wetlands change nitrogen back
into nitrite and nitrate ions, then into
nitrogen gas!
• This is released into the air & atmosphere,
to begin the cycle again.
GASEOUS NITROGEN
(N2) IN ATMOSPHERE
NITROGEN
FIXATION
by industry for
agriculture
FOOD WEBS
ON LAND
FERTILIZERS
NITROGEN FIXATION
bacteria convert to ammonia
(NH3) ; this dissolves to form
ammonium (NH4+)
uptake by
autotrophs
excretion,
death,
decomposition
uptake by
autotrophs
NITROGENOUS WASTES,
REMAINS IN SOIL
NO3IN SOIL
AMMONIFICATION
NH3, NH4+
IN SOIL
loss by
leaching
by bacteria
2. NITRIFICATION
bacteria, fungi convert the
residues to NH3 , this
dissolves to form NH4+
bacteria convert NO2- to
nitrate (NO3-)
1. NITRIFICATION
NO2IN SOIL
bacteria convert NH4+
to nitrite (NO2-)
DENTRIFICATION
loss by
leaching
Fig. 4.30, p. 94
The Nitrogen Cycle
• More important processes!
• Decomposition: process of breaking down
organic material into its parts (nutrients)
• Ammonification: process where bacteria and
fungi convert nitrogen wastes into NH3 which
dissolves into NH4• Assimilation: process where plant roots take up
the useful forms of nitrogen to make DNA, amino
acids and proteins in the plant tissue!
The Nitrogen Cycle
• When we “crop” the land, and take away
plant material that was grown for crops,
we remove N from this cycle!
• If we deplete our soils of their nutrients too
quickly, the sustainability of soil for our
food sources and the health of our
ecosystems are put in jeopardy!
GASEOUS NITROGEN
(N2) IN ATMOSPHERE
NITROGEN
FIXATION
by industry for
agriculture
FOOD WEBS
ON LAND
FERTILIZERS
NITROGEN FIXATION
bacteria convert to ammonia
(NH3) ; this dissolves to form
ammonium (NH4+)
uptake by
autotrophs
excretion,
death,
decomposition
uptake by
autotrophs
NITROGENOUS WASTES,
REMAINS IN SOIL
NO3IN SOIL
AMMONIFICATION
NH3, NH4+
IN SOIL
loss by
leaching
by bacteria
2. NITRIFICATION
bacteria, fungi convert the
residues to NH3 , this
dissolves to form NH4+
bacteria convert NO2- to
nitrate (NO3-)
1. NITRIFICATION
NO2IN SOIL
bacteria convert NH4+
to nitrite (NO2-)
DENTRIFICATION
loss by
leaching
Fig. 4.30, p. 94