مدل سازي انتقال فسفر از حوضه هاي آبخيز به آبهاي سطحي ، (مطالعه موردي : حوضه سنت اسپيريت ايالت كبك كانادا)

Modelling of Phosphorus transport from watersheds to receiving waters (Case study: St. Esprit Watershed, Quebec, Canada)

Organic and commercial phosphorus fertilizers are used in todayʹs agriculture to maintain a high level production of agricultural crops, while in most watersheds controlling of phosphorus is a very important issue. Because of the contribution of phosphorus to water quality deterioration, the environmental scientists are very concerned about the increasing of phosphorus concentration in standing waters. The blossom of the algae and other aquatic plants is related to different nutrient concentration e.g. phosphorus in their media, however, the role of phosphorus as a key element in eutrophication of the surface water and lakes is well documented. Four soil groups and sediment samples from the St. Esprit watershed of Quebec, Canada were amended with 50, 100, and 500 mg P kgʹ soil as KH2PO4. The relationship between water-extractable P, WEP, (soluble phosphorus) and available P, MHi, (Mehlich #3) was determined for water:soil ratios of 100:1, 200:1, and 500:1. Soluble P for these water:soil ratios were measured by method of Murphy and Riley after 4 hours shaking. The 4 hours shaking of the samples were based on the laboratory experience that more than 90% of the water-extracted phosphorus was released after 3 hours shaking for all the samples. Therefore, the shaking time for release of soluble P was set at 4 hours. Mehlich#3 extractable P was also determined in soil and sediment samples. There was a linear relationship (linear isotherm) between the logarithm of soluble and Mehlich#3 extractable P at different water:soil ratios for all soil and sediment samples from the watershed. Therefore, the equation of these isotherms could be used in mathematical models such as ANSWERS, an event based model, for prediction of soluble P transport from this watershed.