____________________
____________________
occurs
when
large
amounts
of
____________________
are
____________________
to
a
body
of
____________________
.
This
can
happen
in
two
ways
:
-
____________________
substances
are
released
____________________
into
the
water
.
-
Water
can
be
polluted
____________________
.
For
example
,
when
it
rains
,
____________________
used
in
fields
may
be
carried
into
a
stream
.
____________________
____________________
contains
harmful
chemicals
such
as
sulphur
and
nitrogen
.
These
chemicals
are
released
into
the
____________________
as
gases
.
They
undergo
a
chemical
transformation
and
are
____________________
by
the
water
in
____________________
.
They
become
part
of
____________________
and
enter
the
____________________
cycle
.
Acid
rain
can
have
adverse
effects
on
:
-
____________________
and
forests
-
____________________
-
Human
____________________
-
____________________
,
other
aquatic
animals
and
insects
-
____________________
