Abstract
Compared to riverine input of nutrients, atmospheric input of nutrients seems to have been given less attention, particularly for lakes and reservoirs with large catchment to lake/reservoir surface area ratio. This is possibly due to the general notion that this nutrient source is not quantitatively important compared to riverine sources considering the fact that the absolute load of atmospheric inputs is a function of the collecting surface area of the lakes. However, it should be noted that nutrient input relative to the size of the lake is more relevant than the absolute load for eutrophication-related water quality problems. Furthermore, for lakes located in arid and semi-arid regions where dry weather conditions prevail during most of the times of the year, riverine inputs of nutrients are greatly reduced. On the other hand, atmospheric input of nutrients through dry fall could be considerable. The results of the eight-month sampling of the present study show that the areal total phosphorus load originating exclusively from atmospheric source, L (P), was 195.05 mg m−2 making the model-predicted in-lake total phosphorus (TP) concentration, Pλ, to be 11.84 mg m−3. This value surpassed the cutoff point of 10 mg m−3 for oligotrophic state making the reservoir mesotrophic based on the probabilistic distribution of trophic state. This suggests that atmospheric sources could sustain the supply of phosphorus during the dry period when riverine input is greatly reduced or even after complete control of riverine sources is achieved. Our results also show that atmospheric input of other nutrients, particularly ammonia, which may trigger the emergence of potentially toxic cyanobacteria, was considerable.
Published Version
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