Too much phosphorus will prematurely age a lake. These are different measurements. Also, reactive phosphorus is the phosphorus in the water available to creatures right now while total phosphorus is that plus the phosphorus tied up in the bodies that will be released when they die and decompose. Alkalinity is a measure of the ability of the water to resist a change in pH when an acid is added. Increasing concentrations over time in ground water samples indicates possible septic tank contamination.
Sources are fertilizer, oil wells, road salt and paper making.
You want lower values. Some lakes with many roads around them that are salted will have increasing salt concentrations as the road salts move into the lake with rains. Turbidity measures the eye appeal of the water and are usually the result of high phytoplankton or silt concentrations. Turbidity greater than 5 NTU's indicate water both unappetizing in appearance and potential hazards. High silt may harbor high concentrations of bacteria colonies.