Re: What are the causes of land pollution?

Hi Emma,
One of the most important tasks for any scientist is to define the 
question she (or he) wants to ask.  The question that you, as a scientist, 
will endevor to answer must be very precise if you expect to obtain a 
precise answer.  The question "what are the causes of land pollution" is 
not a particuarly precise question, because it is very general.  However, 
I'll define a couple of things below, and give your question a shot...
Land: I'll define "land" as "not river, lake, wetland, or ocean."  Note 
that this is MY definition of land...your definition could be different.
Pollution:  I'll define "pollution" as "any material where I don't want 
it."  I realize that this is a very broad definition of pollution, and 
I've chosen it to make the point that pollution can be defined many ways.
Now, to talk about the causes of pollution:  
If I'm sitting on my back porch and enjoying the view of the mountains 
behind my house, I could define "pollution" as the pile of old apples that 
some inconsiderate person dumped in the arroyo (dry wash) behind my house 
(the cause of the pollution, in this instance, was an inconsiderate person 
dumping "trash").  I think of it as "pollution" because I don't like the 
way it looks, however the coyotes who come up the arroyo to forage for 
food are delighted that some kind soul provided the apples for them.
If I use the garden hose to wash out a paintbrush at the bottom of my 
yard, I could define "pollution" as the brown stain that the paint leaves 
on the ground (in this case the cause is an inconsiderate person (me) 
doing something for convenience, rather than taking the time to wash the 
brush in my shop sink and send the residue to the sanitary sewer), even 
though I know that, given the quantity of paint and environmental 
conditions, the paint will degrade rapidly.
Recently, there was a large forest fire in the mountains behind my house 
(in this case the cause was a "controlled burn" by the National Park 
Service, but it could as easily have been lightening-caused, i.e. "Mother 
Nature").  Much of my former gorgeous view is scarred, black, and ugly.  
In this case there are two kinds of pollution: The visual pollution (black 
trees, black soil) and, because of the loss of plants and trees, there is 
a very real flood hazard.  A flood, if it comes, might wash many thousands 
of tons of sediment (mud) off of the mountains (the pollution, in this 
case, is mud where I don't want it), and perhaps wash my house away (I 
don't expect this to happen to me, but it is a real threat to some of the 
people in my community).
Twice a week, a couple of guys with a truck come by to take my household 
garbage away.  They put in into the local landfill.  Landfills are usually 
pretty ugly, and since all kinds of hazardous stuff go into landfills, 
they are potentially dangerous (especially to groundwater).
A coal-burning power plant many miles away from my house provides me with 
electricity.  The power plant discharges waste gasses and particulate 
matter out of several large smoke stacks.  Some of the particulates settle 
out onto the surface of the ground and onto plants within several hundred 
miles of the power plant, including onto my yard.  I can't really 
distinguish power plant pollution from the dust that would settle into my 
yard anyway, but I know that the pollution is there.  In many areas, 
pollution from coal burning power plants is a very real hazard to the 
health of people (especially asthmatics) and the environment (acid rain).  
Nuclear power plants all over the country produce electricity that people 
use to light, heat, and cool their houses, to cook food, etc.  Nuclear 
power plants don't have big smoke stacks (the pictures of big towers that 
you may have seen in pictures of nuclear power plants are cooling towers, 
and the vapor coming from those towers is pure water vapor [clouds]). 
Nuclear power plants don't pollute air, water, or land to any significant 
degree, but they do produce something called "spent fuel," which is highly 
radioactive, and can be dangerous if it isn't handled carefully.  Spent 
fuel could be considered pollution.
Chemical plants, which make all kinds of things including the rubber for 
the tires on your car and the plastics that cover the appliances in your 
kitchen, pollute the air and the water to some degree, and sediments from 
those actions pollute the land.
I've tried to give you an idea of the kind of activities that pollute, and 
also the variety of pollutants that are out there.  My main point, 
however, is that there are all kinds of pollution, and many times your 
point of view will determine whether something is defined as pollution 
(that gravel pile is ugly to me, but it's beautiful to the person who's 
going to use it to build a road).
Great Question! Science is Beautiful! (from my point of view, of course).