Seven wetlands, constructed on agricultural land in the south of Sweden, were investigated with respect to phosphorus (P) retention. The overall aim was to increase the understanding of P retention and find possible explanations for the variations in retention that have been observed in previous studies. This was done by i) investigating P retention in wetlands receiving various water and P loads, ii) investigating the effect of variations in water flow on P transport, iii) comparing how well retention estimates based on water quality data agreed with measurements of the amount of P accumulated in the sediment. Results showed that P retention was positive in all wetlands, but it was variable (1–58 kg ha-1 yr-1) and months with negative retention were observed in nearly all wetlands. Such monthly negative retention coincided with i) high flow periods, when particulate P was either flushed straight through the wetlands or resuspended from the bottoms, and ii) warm low flow periods, in which case dissolved P was probably released from wetland sediments due to anoxic conditions. The results from the two methods for estimating P retention differed. Based on water quality data, the total P load during four years was 65 kg ha-1 and the mean P retention 2.8 kg ha-1 yr-1, or 17% of the total P load. In contrast, the amount of P accumulated in the inlet zone alone amounted to 78% of the P load, and the P content in the upper sediment of the whole wetland area exceeded the P load with a factor four. This discrepancy showed the need to add studies of sediment accumulation to inflow-outflow estimates for an improved understanding of wetland P retention.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:liu-67893 |
| Date | January 2011 |
| Creators | Johannesson, Karin |
| Publisher | Linköpings universitet, Ekologi, Linköpings universitet, Tekniska högskolan, Linköping : Linköping University Electronic Press |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, info:eu-repo/semantics/masterThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Linköping Studies in Science and Technology. Thesis, 0280-7971 ; 1482 |
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