Performance of constructed wetlands in urban and agricultural settings
Abstract
Wetlands are constructed or created for a variety of reasons, including storm water management, non-point source pollution control, and aesthetics. Constructed wetlands are used widely in both urban and agricultural settings to improve water quality, however evaluations of the long-term performance of artificial wetlands are sparse. Evaluation of the performance of constructed wetlands in agricultural, urban, and commercial settings in West Lafayette, Indiana over approximately four years has focused on their performance in treating surface water runoff for nutrients. In the urban setting an average of > 50% of the total mass load of nitrate is due to atmospheric deposition. The trap efficiency of a wetland adjacent to a retail parking lot has increased since installation and was highest in late spring and summer each year during periods of most active plant growth. On a golf course site, overall trap efficiencies are extremely high as water is retained and recycled on the course, except for very large storms, and the number of analytes with positive concentration trap efficiencies has increased with time. Experimental offline wetlands sited in the headwaters of an agricultural watershed reduced nitrate concentrations by an average of 40%, and strong seasonal fluctuations in water chemistry were observed in all wetland settings. In addition, reduction of nitrate concentrations averaged 37% in the first 250 feet (76 meters) of the headwaters of the first-order drainage upstream of the wetlands, and averaged 57% in the one mile (1600 meter) between the headwaters and the wetlands. However, reduction in nitrate concentration in the drainage from the headwaters to the wetlands during the peak plant growth period was approximately 90%. Overall, constructed wetlands are an effective means to reduce non-point source pollution in a range of settings. However, temporal and spatial variations revealed by detailed long-term monitoring indicate that design and placement of the wetlands can be significant influences on their functional sensitivity to anthropogenic activities and natural climatic variations, and highlight the need for continued long-term monitoring.
Degree
Ph.D.
Advisors
Harbor, Purdue University.
Subject Area
Environmental science|Environmental engineering
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