Water Research, 01 November 2012, Vol.46(17), pp.5635-5644
Shallow lake eutrophication has been an important issue of global water environment. Based on the simulation and field sampling experiments in Baiyangdian Lake, the largest shallow lake in North China, this study proposed a shallow lake remediation regime with (reed) incorporating its opposite effects of nutrient removal and water evapotranspiration on water quality. The results of simulation experiments showed that both total nitrogen (TN) and phosphorus (TP) removal efficiencies increased with the increasing reed coverage. The TN removal efficiencies by reed aboveground uptake and rhizosphere denitrification were 11.2%, 13.8%, 22.6%, 28.4%, and 29.6% for the reed coverage of 20%, 40%, 60%, 80%, and 100%, respectively. Correspondingly, TP removal efficiencies by aboveground reed uptake were 1.4%, 2.5%, 4.4%, 7.4% and 7.9%, respectively. However, the water quality was best when the reed coverage was 60% (72 plants m ). This was due to the fact that the concentration effect of reed evapotranspiration on nutrient increased with reed coverage. When the reed coverage was 100% (120 plants m ), the evapotranspiration was approximately twice that without reeds. The field sampling results showed that the highest aboveground nutrient storages occurred in September. Thus, the proposed remediation regime for Baiyangdian Lake was that the reed coverage should be adjusted to 60%, and the aboveground biomass of reeds should be harvested in each September. With this remediation regime, TN and TP removal in Baiyangdian Lake were 117.8 and 4.0 g m , respectively, and the corresponding removal efficiencies were estimated to be 49% and 8.5% after six years. This study suggests that reed is an effective plant for the remediation of shallow lake eutrophication, and its contrasting effects of nutrient removal and evapotranspiration on water quality should be considered for establishing the remediation regime in the future. Water quality of shallow lakes will be influenced by two opposite effects of reeds. On the one hand, reeds can remove nutrients from water and sediments, which will improve water quality; on the other hand, their evapotranspiration will lead to higher water nutrient concentrations due to the concentration effect. ► Two opposite effects of reeds on water quality were proposed for shallow lake remediation. ► Reed nutrient removal and evapotranspiration increased with its coverage. ► The water quality was best when the reed coverage was 60%. ► The peak reed nutrient storage occurred in September for Baiyangdian Lake. ► The contribution of rhizosphere denitrification to TN removal by reeds was 72%-82%.
Eutrophication ; Nutrient Removal ; Phragmites Australis ; Remediation ; Shallow Lake ; Water Evapotranspiration ; Engineering
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