what are the primary sources of these nutrients phosphorous&nitrogen that caused impairment of surface water?

Answer 1

Poor soil management and improper use of quick release fertilizers are the single main sources of nitrogen pollution. Here in Florida, we provide over 50% of all phosphorus used in the World, and it's the mining that causes us trouble. Te best things to do to address this problem is to improve agricultural soil conservation techniques, reduce the use of chemical fertilizer which are quick to leach out of the soil, and to increase the use of compost and manures in large scale agricultural operations. The nitrogen and various nutrients in compost are 'fixed', that is, they are chemically bound to the material, and thus are less capable of washing or leaching away from the root zone and into local water supplies. The two biggest pollution problems in the world today are - too much nitrogen in the water and too much carbon in the air.

Answer 2

The biggest sources of phosphorous and nitrogen in runoff water are agricultural fertilizers. Runoff from feed lots and dairy farms are also major contributors.