Inundation Influences on Bioavailability of Phosphorus in Managed Wetland Sediments in Agricultural Landscapes

Abstract

Agricultural runoff carries high nutrient loads to receiving waters, contributing to eutrophication. Managed wetlands can be used in integrated management efforts to intercept nutrients before they enter downstream aquatic systems, but detailed information regarding sorption and desorption of P by wetland sediments during typical inundation cycles is lacking. This study seeks to quantify and elucidate how inundation of wetland sediments affects bioavailability of P and contributions of P to downstream systems. A managed wetland cell in Tunica County, Mississippi was subjected to a simulated agricultural runoff event and was monitored for bioavailable phosphorus (water-extractable P [P], Fe-P, and Al-P) of wetland sediments and water level during the runoff event and for 130 d afterward. Inundation varied longitudinally within the wetland, with data supporting significant temporal relationships between inundation and P desorption. Concentrations of P were significantly higher at the site that exhibited variable hydroperiods (100 m) as compared with sites under consistent inundation. This suggests that sites that are inundated for longer periods of time desorb less P immediately to the environment than sites that have periodic or ephemeral inundation. Concentrations of iron oxalate and NaOH-P were significantly higher at the least inundated site as compared with all other sites (F = 5.43; = 0.001) irrespective of time. These results support the hypothesis that increased hydraulic residence time decreases the bioavailability of P in wetland sediments receiving agricultural runoff. This finding suggests that the restoration of wetlands in the mid-southern United States may be hydrologically managed to improve P retention.

Influence of varying nutrient and pesticide mixtures on abatement efficiency using a vegetated free water surface constructed wetland mesocosm

“…[37,38] Water temperatures were indicative of climatic conditions of the study site (north Mississippi) during summer, with means ranging from 22.4 to 27.3 • C. [36,39] No outflow occurred from the wetland at any time during the study periods (28 July to 26 August 2009 and 1 to 30 September 2009) despite ∼ 162 mm total precipitation occurring from 28 July to 26 August and 188 mm total precipitation occurring from 1 to 30 September. Prior to both the first and second treatment periods, east and west section baseline pretreatment (27 July 2009 and 31 August 2009) nutrient and pesticide concentrations indicated low levels of N and P and very low to below detection limit concentrations of atrazine, S-metolachlor and permethrin (Supplemental Table 1 available online at http://dx.doi.org/10.1080/02757540.2013.861823).…”

“…Monitored in situ water quality of the vegetated free water surface constructed wetland mesocosm was typical of shallow freshwater wetland habitats in the south-eastern USA ( Table 2) with hypoxic conditions (dissolved oxygen < 2.0 mg L) [35,36] and slightly acidic water. [37,38] Water temperatures were indicative of climatic conditions of the study site (north Mississippi) during summer, with means ranging from 22.4 to 27.3 • C. [36,39] No outflow occurred from the wetland at any time during the study periods (28 July to 26 August 2009 and 1 to 30 September 2009) despite ∼ 162 mm total precipitation occurring from 28 July to 26 August and 188 mm total precipitation occurring from 1 to 30 September.…”

Examining Playa Wetland Inundation Conditions for National Wetland Inventory, Soil Survey Geographic Database, and LiDAR Data

“…Periodic inundation is an important component of the physical, chemical, and biological processes for wetlands (Kröger et al 2012). Hydric vegetation is another key parameter in the provision of wetland services.…”

Sediment and Phosphorus Accumulation Dynamics behind Newly Installed Low-Grade Weirs in Agricultural Drainage Ditches

“…Typically, pollutants leave agricultural landscapes through surface and subsurface runoff and are captured and transported through drainage ditches. Therefore, alteration of hydrology of drainage ditches could effectively manage sediment and P (Kröger et al, 2012a). …”

“…As a physical barrier, weirs increase the hydraulic residence time (HRT) of drainage ditch systems (Kröger et al, 2008). Stabilization of HRT in primary aquatic systems associated with agriculture has shown to decrease concentrations of bioavailable P compared with sites under irregular inundation (Kröger et al, 2012a). An increase in HRT allows P time to interact with ditch sediments (Bowmer et al, 1994; Jiang et al, 2007).…”