Do constructed wetlands in grass strips reduce water contamination from drained fields?

• Published in: Environmental pollution Vol. 207; pp. 365 - 373
• Main Authors: Vallée, Romain, Dousset, Sylvie, Schott, François-Xavier, Pallez, Christelle, Ortar, Agnès, Cherrier, Richard, Munoz, Jean-François, Benoît, Marc
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2015; Elsevier Science
• Subjects: Agriculture; Biodiversity and Ecology; Constructed wetland; Construction; Drainage, Sanitary; Environmental Restoration and Remediation - methods; Environmental Sciences; Field-scale; Freshwater; Grasses; Half life; Nitrate; Pesticide; Pesticides; Pesticides - analysis; Poaceae - growth & development; Remediation; Seasons; Sorption; Strip; Water Pollutants, Chemical - analysis; Water pollution; Wetlands; Nitrate; Remediation; Pesticide; Field-scale; Constructed wetland
• ISSN: 0269-7491; 0013-9327; 1873-6424
• DOI: 10.1016/j.envpol.2015.09.027

This study evaluates the efficiency of two small constructed wetlands installed in the regulatory grass strips between a drained plot and a river. The observed nitrate removal efficiencies were independent of the season or type of constructed wetland and ranged from 5.4 to 10.9% of the inlet amounts. The pesticide mass budgets ranged from −618.5 to 100%, depending on the molecule. The negative efficiencies were attributed to runoff and remobilization. In contrast, the highest efficiencies were associated with pesticides with high Koc and low DT50 (half-life) values, suggesting sorption and degradation. However, the effectiveness of these wetlands is limited for pesticides with low Koc or high DT50 values; thus, the use of these molecules must be reduced. Increasing the number of these small, inexpensive and low-maintenance wetlands in the agricultural landscape would reduce the level of water pollution whilst preserving the extent of cultivated land, but their long-term effectiveness should be evaluated. [Display omitted] •The efficiency of small constructed wetlands was assessed at the field-scale.•These wetlands effectively reduce pollutant concentrations in surface waters.•The nitrate removal efficiencies were independent of the season.•The wetlands' effectiveness is promoted by high pesticide retention and short half-lives. Small wetlands installed in grass strips are effective in minimizing nitrate and pesticide concentrations in surface waters, especially for pesticides with low mobility and persistence.