Phosphorus fractions in biosolids, biosolid-amended soils, runoffs and its impact on primary productivity in aquatic ecosystems

The impact of land application of biosolids on soil phosphorus (P) and subsequent transfer to aquatic ecosystems were assessed. Boxed reference soils were amended with two biosolids at a rate of 8 dry t/ha. Biosolids and soil samples taken over four months were sequentially fractionated to determine various inorganic and organic P pools. Also, within three weeks of biosolids application, four storm events were simulated and surface runoff and leachate from the soils were collected and analyzed for different P forms. The runoffs and equivalent inorganic nutrient were added to different mesocosms that mimicked stratified lakes. Samples from the mesocosms were periodically collected and analyzed for various physical, chemical and biological parameters. The results indicated that biosolids significantly affect different P pools in soils. Also, P loading from biosolids was expected to drive the mesocosms to hypereutrophication, yet the response was moderately eutrophic, followed by decline in chlorophyll a.