Water Pollution-Plant Nutrients
Plant nutrients
? Plant growth requires various nutrients.
– Major nutrient elements,C,N,P,
– trace elements,S,Si,Cl,I,and metallic elements (Fe,Mn,
Cu,etc).
? The minor elements,because of the low demand,can
usually be supplied at adequate rates in natural waters,
? The required proportion of the major nutrient elements
is C:N:P=106:16:1.
? C,despite the largest demand,is plentifully supplied to
phytoplanktons from CO2 in the atmosphere.
Natural nutrient cycling in aquatic ecosystem
N and P are often the limiting nutrients
? The limiting nutrient is the least available element in
relation to its required abundance.
? N is abundant in the form of N2,but N2 can only be
utilized through N2-fixing bacteria.
? In waters where N2-fixing algal species are common,N
is not usually limiting.
– In regions where N2-fixing species are less abundant,
especially the oceans,N maybe the limiting nutrient.
? This leaves P as the limiting element to plant growth.
? This shortage keeps the spread of vegetation under
control.
Phytoplankton productivity as a function of N
and P concentrations and sunlight
In winter,low
temperature and
sunlight are the
limiting factors to
phytoplankton
productivity,In
summer,nutrients
become the limiting
factor,
Decay of dead plant
matter replenish
nutrients,leading to a
secondary peak of
phytoplankton
productivity.
Consequences of excessive nutrient loading
? If a new source of N or P is introduced into the
water,excessive plant growth occurs,and the
algae population explodes (algae bloom),this
phenomenon is called eutrophication.
? Adverse consequences of eutrophication:
– Waterways become clogged
– Algae might release unpleasant-smelling,bad-
tasting substances
– Decay of algae induces decrease in DO,
Source of N
? Agriculture land treated with manure or nitrate
fertilizers
? Slaughterhouses
? Stockyards
? Atmospheric deposition:
– NOx from automobiles,power plants,etc.
Source of P,Detergents
? The two main ingredients in synthetic detergents are
a surfactant and a builder.
? Surfactants remove grease and dirt particles from
clothing and dishes by solubilizing them into water,
? Cations Ca2+ and Mg2+ in water precipitates
surfactants in detergents,making scum.
? Builders tie up polyvalent cations and thereby
prevent them from precipitating the detergents.
Detergents,Surfactant structures
Detergents,surfactant micelle
Detergents,P-containing builder
Sodium tripolyphosphate serves as a builder in detergents to
bind polyvalent ions.
(In addition,it furnishes the necessary alkalinity for cleaning)
Source of P
? Sewage treatment plants
? Industrial plants that use phosphorus-containing
cleaning agents
? Phosphate mines
Control of eutrophication
? Limit discharge and atmospheric deposition
of N
? Limit discharge of phosphorus-containing
wastes.
– Eradication of P in detergents
Alternatives to the P
builder
zeolites
Study Questions
1,What are the major plant nutrients and their
required proportion for plant growth?
2,What are the major sources for the major plant
nutrients?
3,Why P compounds are used in detergents? What is
the link between P in detergents and water quality?
Plant nutrients
? Plant growth requires various nutrients.
– Major nutrient elements,C,N,P,
– trace elements,S,Si,Cl,I,and metallic elements (Fe,Mn,
Cu,etc).
? The minor elements,because of the low demand,can
usually be supplied at adequate rates in natural waters,
? The required proportion of the major nutrient elements
is C:N:P=106:16:1.
? C,despite the largest demand,is plentifully supplied to
phytoplanktons from CO2 in the atmosphere.
Natural nutrient cycling in aquatic ecosystem
N and P are often the limiting nutrients
? The limiting nutrient is the least available element in
relation to its required abundance.
? N is abundant in the form of N2,but N2 can only be
utilized through N2-fixing bacteria.
? In waters where N2-fixing algal species are common,N
is not usually limiting.
– In regions where N2-fixing species are less abundant,
especially the oceans,N maybe the limiting nutrient.
? This leaves P as the limiting element to plant growth.
? This shortage keeps the spread of vegetation under
control.
Phytoplankton productivity as a function of N
and P concentrations and sunlight
In winter,low
temperature and
sunlight are the
limiting factors to
phytoplankton
productivity,In
summer,nutrients
become the limiting
factor,
Decay of dead plant
matter replenish
nutrients,leading to a
secondary peak of
phytoplankton
productivity.
Consequences of excessive nutrient loading
? If a new source of N or P is introduced into the
water,excessive plant growth occurs,and the
algae population explodes (algae bloom),this
phenomenon is called eutrophication.
? Adverse consequences of eutrophication:
– Waterways become clogged
– Algae might release unpleasant-smelling,bad-
tasting substances
– Decay of algae induces decrease in DO,
Source of N
? Agriculture land treated with manure or nitrate
fertilizers
? Slaughterhouses
? Stockyards
? Atmospheric deposition:
– NOx from automobiles,power plants,etc.
Source of P,Detergents
? The two main ingredients in synthetic detergents are
a surfactant and a builder.
? Surfactants remove grease and dirt particles from
clothing and dishes by solubilizing them into water,
? Cations Ca2+ and Mg2+ in water precipitates
surfactants in detergents,making scum.
? Builders tie up polyvalent cations and thereby
prevent them from precipitating the detergents.
Detergents,Surfactant structures
Detergents,surfactant micelle
Detergents,P-containing builder
Sodium tripolyphosphate serves as a builder in detergents to
bind polyvalent ions.
(In addition,it furnishes the necessary alkalinity for cleaning)
Source of P
? Sewage treatment plants
? Industrial plants that use phosphorus-containing
cleaning agents
? Phosphate mines
Control of eutrophication
? Limit discharge and atmospheric deposition
of N
? Limit discharge of phosphorus-containing
wastes.
– Eradication of P in detergents
Alternatives to the P
builder
zeolites
Study Questions
1,What are the major plant nutrients and their
required proportion for plant growth?
2,What are the major sources for the major plant
nutrients?
3,Why P compounds are used in detergents? What is
the link between P in detergents and water quality?
