Mitigating agrichemicals from an artificial runoff event using a managed riverine wetland
Highlights
► Mitigation efficiency of a managed wetland dosed with agrichemicals was assessed. ► Peak sediment, nutrient, and pesticide loads occurred within 3 h of dosing. ► Agrichemicals were rapidly attenuated by 42–98% within 48 h. ► By day 28, all agrichemicals were near or below pre-dosing concentrations. ► Managed wetlands can efficiently trap agricultural runoff after rainfall events.
Introduction
Agricultural regions wherein major rivers with broad, low-gradient floodplains exist often contain numerous natural backwater aquatic habitats, such as wetlands, conducive to anthropogenic manipulation (Mitsch et al., 2005, Shields et al., 2005, Shields and Pearce, 2010, Lizotte et al., 2009). Such freshwater wetlands, with minimal cost, can potentially be hydrologically managed to maximize their natural filtering capabilities to mitigate storm runoff from adjacent agricultural fields (Mitsch et al., 2005, Lizotte et al., 2009, Shields and Pearce, 2010). Costs to stakeholders such as farmers, land managers, land owners, and regulatory agencies would be less than the cost of full construction, implementation, and management of a constructed wetland of comparable size (Shields et al., 2005, Kadlec, 2006). Also, because natural backwater wetlands already provide pre-existing hydrology, hydrophytes, and hydrosoils, these conditions would not need any “conditioning period” as for constructed wetlands (Mitsch and Gosselink, 2007). Despite these advantages, little information exists regarding the ability of anthropogenically manipulated natural backwater wetlands in mitigating contaminants from agricultural runoff under controlled conditions.
Riverine backwater wetlands within river floodplains have important economic and ecological functions such as acting as filters and processors of a variety of agricultural contaminants including suspended sediment, nutrients and pesticides entering from adjacent agricultural fields (Reddy and DeLaune, 2008). The hydrology of such wetlands can be controlled to increase the efficacy of their natural filtering capabilities (Mitsch et al., 2002, Lizotte et al., 2009). Nutrient mitigation from agricultural sources has been a primary focus for several decades due to the increase in eutrophication of receiving lakes, rivers, streams and estuaries worldwide (Wetzel, 1992, Scanlon et al., 2007) and wetlands have long been known to be highly efficient at removing nutrients under favorable conditions (Mitsch and Gosselink, 2007). For these reasons, there is an increasing need to expand our knowledge of nutrient mitigation capabilities to efficiently maximize available wetland resources via hydraulic modification of riverine floodplain wetlands, when applicable. The purpose of this study was to assess the trapping efficiency of a modified riverine backwater wetland amended with a mixture of suspended sediment, two nutrients [nitrogen (N) and phosphorus (P)], and three pesticides (atrazine, metolachlor, and permethrin) during a simulated agricultural runoff event. Previous study by Lizotte et al. (2009) within the same wetland system assessed the trapping of pesticides only. The study was limited in scope both spatially (only two sites: inflow and furthest downstream weir) and pollutant mixture complexity. The current study expands the previous work of Lizotte et al. (2009) by incorporating a broader spatial assessment, and more complex, and realistic, pollutant mixture, to better address questions of agricultural pollutant trapping and attenuation efficiency of the managed riverine wetland study site.
Section snippets
Area description
A reach of the Coldwater River ~ 20 km downstream from Arkabutla Lake Dam in Tunica County, Mississippi, was selected because of the presence of > 20 severed riverine backwater meander bends and other floodplain water bodies (Fig. 1). A severed riverine compound meander bend backwater (~ 2.5 km long × 40 m wide) was selected for this study. The study site, inside the mainstem flood control levee, is the result of a 0.4 km cutoff constructed in 1941–42. Land-use both inside and outside the bend are in
Methods
On June 24, 2009, 611 m3 of water was released from the upstream lake cell portion of the study site into the modified wetland cell portion over about 4 h (Fig. 2), simulating agricultural runoff during an ~ 1-cm rainfall event from a 16-ha cultivated field. Simulated agricultural runoff comprised of local source suspended sediment (adjacent field soil), nutrients as P (42% P2O5) and N (34% NH4NO3), and pesticides as atrazine, S-metolachlor and permethrin was amended once simulating a “first
Results
The simulated hydrograph was quite similar to the targeted model, with peak discharge of 85 L s− 1 about 1 h after flow initiation (Fig. 2). No outflow from the wetland occurred during simulated event, and although a total of approximately 149 mm of rainfall was recorded by the nearest rain gage during the monitoring period (reported at Sarah, Mississippi), no outflow occurred during the period following the event until day 22 (Fig. 3). Local thunderstorms triggered outflows from the wetland to the
Discussion
The current study provides valuable information on the use and efficacy of natural wetlands modified to enhance their natural filtering capabilities when inundated with a complex mixture of sediment, nutrients, and pesticides typically occurring in agricultural runoff. As a result, such studies as the current one are important in understanding the viability of using and managing available existing adjacent riverine floodplain wetlands within agricultural watersheds that can be modified to
Conclusions
Overall results of our study indicate that hydraulic management of a natural riverine backwater wetland can effectively trap a variety of contaminants commonly occurring in agricultural runoff during small to moderate rainfall events, mitigating potential ecological effects downstream within the main river channel. Controlled hydrology can be used to increase the efficiency of natural wetland filtering capabilities. The hydrologically modified riverine backwater wetland in the present study can
Acknowledgments
The authors thank the numerous technicians and support personnel who provided assistance with logistics, sample collection, and analysis. We also thank the several anonymous reviewers who provided helpful comments. Mention of equipment, computer programs, or a chemical does not constitute an endorsement for use by the US Department of Agriculture nor does it imply pesticide registration under FIFRA as amended. The US Department of Agriculture is an equal opportunity employer.
References (51)
- et al.
Hydrology and biogeochemistry in a created river diversion oxbow wetland
Ecol Eng
(2007) - et al.
Nutrient removal in wetlands with different macrophyte structures in eastern Lake Taihu, China
Ecol Eng
(2010) Free surface water wetlands for phosphorus removal: the position of the Everglades nutrient removal project
Ecol Eng
(2006)- et al.
Nutrient, metal, and pesticide removal during storm and nonstorm events by a constructed wetland on an urban golf course
Ecol Eng
(2004) - et al.
Constructed wetlands as a component of the agricultural landscape: mitigation of herbicides in simulated runoff from upland drainage areas
Chemosphere
(2011) - et al.
Comparison of nutrient and contaminant fluxes in two areas with different hydrological regimes (Empordà Wetland, NE Spain)
Water Res
(2003) - et al.
Removal of pesticide mixtures in a stormwater wetland collecting runoff from a vineyard catchment
Sci Total Environ
(2011) - et al.
Nitrogen and phosphorus yields in run-off from silty soils in the Mississippi Delta, U.S.A.
Agric Ecosyst Environ
(1989) - et al.
Ecological engineering applied to river and wetland restoration
Ecol Eng
(2002) - et al.
Nitrate-nitrogen retention in wetlands in the Mississippi River Basin
Ecol Eng
(2005)
Mitigation of metolachlor-associated agricultural runoff using constructed wetlands in Mississippi, USA
Agric Ecosyst Environ
Assessment of pesticide contamination in three Mississippi Delta oxbow lakes using Hyalella azteca
Chemosphere
Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland
Environ Pollut
The effect of pre-aeration on the purification processes in the long-term performance of a horizontal subsurface flow constructed wetland
Sci Total Environ
Feasibility of constructed wetlands for removing chlorothalonil and chlorpyrifos from aqueous mixtures
Environ Pollut
Removal of nutrients in various types of constructed wetlands
Sci Total Environ
Standard methods for the examination of water and wastewater
The water quality consequences of restoring wetland hydrology to a large agricultural watershed in the southeastern coastal plain
Ecosystems
How well can we predict the toxicity of pesticide mixtures to aquatic life?
Integr Environ Assess Manag
Intermediate statistical methods and applications: a computer package approach
Efficacy of constructed wetlands in pesticide removal from tailwaters in the Central Valley, California
Environ Sci Technol
Nutrient transformation in a natural wetland receiving sewage effluent and the implications for waste treatment
Water Sci Technol
Wetland nutrient removal: a review of the evidence
Hydrol Earth Syst Sci
Nitrogen retention in natural Mediterranean wetland-streams affected by agricultural runoff
Hydrol Earth Syst Sci
Primer of biostatistics
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