



Human influences on the nitrogen cycle
Humans have contributed significantly to the nitrogen cycle in a number of ways.

Atmospheric pollution is another problem. The main culprits are nitrous oxide (N
_{2} O), nitric oxide (NO) and nitrogen dioxide (NO
_{2} ). Most of these gases result either from emissions from agricultural soils (and particularly artificial fertilisers), or from the combustion of fossil fuels in industry or motor vehicles. The combustion (burning) of nitrogenbearing fuels such as coal and oil releases this nitrogen as NO
_{2} or NO gases. Both NO
_{2} and NO can combine with water droplets in the atmosphere to form
acid rain . Furthermore, both NO and NO
_{2} contribute to the depletion of the ozone layer and some are
greenhouse gases . In high concentrations, these gases can contribute towards
global warming .
 Both
artificial fertilisation and the planting of
nitrogen fixing crops , increase the amount of nitrogen in the soil. In some ways this has positive effects because it increases the fertility of the soil and means that agricultural productivity is high. On the other hand, however, if there is too much nitrogen in the soil, it can run off into nearby water courses such as rivers or can become part of the groundwater supply as we mentioned earlier. Increased nitrogen in rivers and dams can lead to a problem called
eutrophication . Eutrophication is the contamination of a water system with excess nurtrients, which stimulates excessive algae growth at the expense of other parts of the ecosystem. This occurs as eutrophication reduces oxygen levels in the water. Sometimes this can cause certain plant species to be favoured over the others and one species may 'take over' the ecosystem, resulting in a decrease in plant diversity. This is called a 'bloom'. Eutrophication also affects water quality. When the plants die and decompose, large amounts of oxygen are used up and this can cause other animals in the water to die.
Case study : fertiliser use in south africa
Refer to the data table below, which shows the average fertiliser use (in kilograms per hectare or kg/ha) over a number of years for South Africa and the world. Then answer the questions that follow:

1965 
1970 
1975 
1980 
1985 
1990 
1995 
2000 
2002 
SA 
27.9 
42.2 
57.7 
80.3 
66.6 
54.9 
48.5 
47.1 
61.4 
World 
34.0 
48.9 
63.9 
80.6 
86.7 
90.9 
84.9 
88.2 
91.9 
 On the same set of axes, draw two line graphs to show how fertiliser use has changed in SA and the world between 1965 and 2002.
 Describe the trend you see for...
 the world
 South Africa
 Suggest a reason why the world's fertiliser use has changed in this way over time.
 Do you see the same pattern for South Africa?
 Try to suggest a reason for the differences you see in the fertiliser use data for South Africa.
 One of the problems with increased fertiliser use is that there is a greater chance of nutrient runoff into rivers and dams and therefore a greater danger of eutrophication. In groups of 56, discuss the following questions:
 What could farmers do to try to reduce the risk of nutrient runoff from fields into water systems? Try to think of at least 3 different strategies that they could use.
 Imagine you are going to give a presentation on eutrophication to a group of farmers who know nothing about it. How will you educate them about the dangers? How will you convince them that it is in their interests to change their farming practices? Present your ideas to the class.
Questions & Answers
explain and give four Example hyperbolic function
The denominator of a certain fraction is 9 more than the numerator. If 6 is added to both terms of the
fraction, the value of the fraction becomes 2/3. Find the original fraction.
2. The sum of the least and greatest of 3 consecutive integers is 60. What are the valu
1. x + 6 2
 = _
x + 9 + 6 3
x + 6 3
 x  (cross multiply)
x + 15 2
3(x + 6) = 2(x + 15)
3x + 18 = 2x + 30 (2x from both)
x + 18 = 30 (18 from both)
x = 12
Test:
12 + 6 18 2
 =  = 
12 + 9 + 6 27 3
Pawel
2.
(x) + (x + 2) = 60
2x + 2 = 60
2x = 58
x = 29
29, 30, & 31
Pawel
on number 2 question How did you got 2x +2
Ifeanyi
combine like terms. x + x + 2 is same as 2x + 2
Pawel
Mark and Don are planning to sell each of their marble collections at a garage sale. If Don has 1 more than 3 times the number of marbles Mark has, how many does each boy have to sell if the total number of marbles is 113?
Mark = x,. Don = 3x + 1
x + 3x + 1 = 113
4x = 112, x = 28
Mark = 28, Don = 85, 28 + 85 = 113
Pawel
how do I set up the problem?
what is a solution set?
Harshika
find the subring of gaussian integers?
Rofiqul
hello, I am happy to help!
please can go further on polynomials quadratic
Abdullahi
I need quadratic equation link to Alpa Beta
divide by 2 on each side of the equal sign to solve for x
corri
Want to review on complex number
1.What are complex number
2.How to solve complex number problems.
Beyan
yes i wantt to review
Mark
use the y intercept and slope to sketch the graph of the equation y=6x
how do we prove the quadratic formular
please help me prove quadratic formula
Darius
hello, if you have a question about Algebra 2. I may be able to help. I am an Algebra 2 Teacher
thank you
help me with how to prove the quadratic equation
Seidu
may God blessed u for that.
Please I want u to help me in sets.
Opoku
x2y+3z=3
2xy+z=7
x+3yz=6
can you teacch how to solve that🙏
Mark
Solve for the first variable in one of the equations, then substitute the result into the other equation.
Point For:
(6111,4111,−411)(6111,4111,411)
Equation Form:
x=6111,y=4111,z=−411x=6111,y=4111,z=411
Brenna
(61/11,41/11,−4/11)
Brenna
x=61/11
y=41/11
z=−4/11
x=61/11
y=41/11
z=4/11
Brenna
Need help solving this problem (2/7)^2
what is the coefficient of 4×
the operation * is x * y =x + y/ 1+(x × y) show if the operation is commutative if x × y is not equal to 1
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Source:
OpenStax, Siyavula textbooks: grade 10 physical science. OpenStax CNX. Aug 29, 2011 Download for free at http://cnx.org/content/col11245/1.3
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