| Five tracer studies were performed to evaluate potential effects of flow, vegetation density, aeration and seasonal influences on wetland residence time distributions. Residence times under flows of 36 L d-1 and 76 L d-1 averaged 24 d and 20 d, respectively. At the higher flow, non-vegetated wetlands experienced a residence time 3 d longer than vegetated wetlands. At the lower flow, minor differences were observed between vegetated and non-vegetated wetlands. Longer residence times were observed in the non-aerated wetland during winter (20.6 d) and summer (30.2 d) than in fall (14 d) and spring (19.6 d). The aerated wetland had a longer residence time (26.4 d) than the non-aerated wetland (20.6 d) in winter. With the exception of winter, aeration on its own provided minimal benefit to increasing residence time. Distributions related more to wetland flows than to vegetation density. Seasonal effects likely resulted from varying vegetation densities and freezing. |
