Characterization of phosphorus accumulation and release using diffusive gradients in thin films (DGT) - linking the...

Taihu Lake is well known internationally due to its algae bloom, and phosphorus fertilization and accumulation in the watershed soil played an important role in the lake eutrophication. To explore the linkage between soil and sediment legacy P, the soils from four representative land uses in the upstream watershed and sediments from typical lake areas were sampled and analyzed for P species. Meanwhile, the DGT technology was used to characterize the labile P in the soil and sediment and its release dynamics. The results indicated that Taihu Lake was the major total phosphorus sink (TP = 481.7 ± 97 mg/kg) and wheat land the major reactive phosphorus stock (RP = 37.3 ± 9 mg/kg) in the watershed. The DGT-P dynamic with the deployment time (t) presented a downward exponential curve (f(t) = a × t^-b, b > 0) and the regression parameters implied the initial P stock (a) and release rate (b) of labile P. Although the result of the extract based method was statistically correlated to the DGT measured P (p < 0.05), the DGT result had advantages over the traditional method due to its in-situ measurement and kinetic characterization of available P. Since the regression parameters reflected combined factors that impact the interaction between solid and solution P, the soil or sediment properties such as pH and organic matters need to be further studied in details, although they presented a significant correlation with DGT-P in this work. Our work provides a new insight in the rapid assessment of the size and resupply capacity of the existing legacy P stocks.