Nutrient and Sediment Removal by a Restored Wetland Receiving Agricultural Runoff

• Published in: Journal of environmental quality Vol. 32; no. 4; pp. 1534 - 1547
• Main Authors: Jordan, Thomas E., Whigham, Dennis F., Hofmockel, Kirsten H., Pittek, Mary A.
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy, Crop Science Society of America, Soil Science Society 01.07.2003; American Society of Agronomy
• Subjects: Agriculture; Biodegradation, Environmental; Ecosystem; Environmental Monitoring; Geologic Sediments - chemistry; Nitrogen - analysis; Phosphorus - analysis; Rain; Seasons; Water Movements; Water Pollution - prevention & control; USA, Maryland
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2003.1534

ABSTRACT Few studies have measured removal of pollutants by restored wetlands that receive highly variable inflows. We used automated flow‐proportional sampling to monitor the removal of nutrients and suspended solids by a 1.3‐ha restored wetland receiving unregulated inflows from a 14‐ha agricultural watershed in Maryland, USA. Water entered the wetland mainly in brief pulses of runoff, which sometimes exceeded the 2500‐m3 water holding capacity of the wetland. Half of the total water inflow occurred in only 24 days scattered throughout the two‐year study. Measured annual water gains were within 5% of balancing water losses. Annual removal of nutrients differed greatly between the two years of the study. The most removal occurred in the first year, which included a three‐month period of decreasing water level in the wetland. In that year, the wetland removed 59% of the total P, 38% of the total N, and 41% of the total organic C it received. However, in the second year, which lacked a drying period, there was no significant (p > 0.05) net removal of total N or P, although 30% of the total organic C input was removed. For the entire two‐year period, the wetland removed 25% of the ammonium, 52% of the nitrate, and 34% of the organic C it received, but there was no significant net removal of total suspended solids (TSS) or other forms of N and P. Although the variability of inflow may have decreased the capacity of the wetland to remove materials, the wetland still reduced nonpoint‐source pollution.